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Characterization of hypoxic events in Paracas bay (Peru, 13.8°S) through intensity and biological effect indexes
2024 - Maricarmen Igarza, Arturo Aguirre-Velarde b, Jorge Tam, Rosa Cueto-Vega, Jonathan Flye-Sainte-Marie, Dimitri Gutiérrez, Lander Merma-Mora, Francois Colas
Over the past decade, there has been a significant increase in low oxygen conditions within marine coastal areas, profoundly impacting ecosystem processes and living coastal resources. Coastal bays in highly productive upwelling regions, where hypoxia occurs naturally, are special areas affected by both local and adjacent shelf-related processes. Paracas Bay (13.8°S) is a traditional shellfish fishing and intense farming area highly influenced by one of the most active upwelling centers of the Peruvian coast. Despite the small dimensions of the bay (35 km2), a key feature is its complex physical dynamics and high environmental variability. Recently, important efforts have been made in the study of both the spatial and temporal oxygen concentration variability, nevertheless, information regarding the ecological and biological impact of hypoxic events is still lacking. In this study, the spatial and temporal distribution of hypoxic events was analyzed across Paracas bay at different depths by means of high-frequency hourly dissolved oxygen records collected by data-loggers deployed across the bay during the periods September 2012 – February 2013 and March 2015 – February 2017. To study the ecological impact of hypoxic events, we developed a hypoxia intensity index, while the biological impact was studied through the development of a hypoxia biological effect index using as model species the Peruvian scallop (Argopecten purpuratus). Our results showed that hypoxic events have an intrinsic variability across the bay. The deeper areas of the bay, towards the northwest and center, were characterized by long, intense, and lethal events, while the southeast and southwest, shallower areas, were characterized by shorter events of low intensity and either sublethal or innocuous. We propose that the observed variability is not only related to the large-scale environmental context in which the events occurred, but also to small-scale variability linked to local circulation, biological activity, and sediment biogeochemistry. We expect that our research will be useful not only for scientific purposes, but also for coastal resource management and aquaculture, underlining the importance of developing high-resolution oxygen monitoring systems in coastal bays.
Over the past decade, there has been a significant increase in low oxygen conditions within marine coastal areas, profoundly impacting ecosystem processes and living coastal resources. Coastal bays in highly productive upwelling regions, where hypoxia occurs naturally, are special areas affected by both local and adjacent shelf-related processes. Paracas Bay (13.8°S) is a traditional shellfish fishing and intense farming area highly influenced by one of the most active upwelling centers of the Peruvian coast. Despite the small dimensions of the bay (35 km2), a key feature is its complex physical dynamics and high environmental variability. Recently, important efforts have been made in the study of both the spatial and temporal oxygen concentration variability, nevertheless, information regarding the ecological and biological impact of hypoxic events is still lacking. In this study, the spatial and temporal distribution of hypoxic events was analyzed across Paracas bay at different depths by means of high-frequency hourly dissolved oxygen records collected by data-loggers deployed across the bay during the periods September 2012 – February 2013 and March 2015 – February 2017. To study the ecological impact of hypoxic events, we developed a hypoxia intensity index, while the biological impact was studied through the development of a hypoxia biological effect index using as model species the Peruvian scallop (Argopecten purpuratus). Our results showed that hypoxic events have an intrinsic variability across the bay. The deeper areas of the bay, towards the northwest and center, were characterized by long, intense, and lethal events, while the southeast and southwest, shallower areas, were characterized by shorter events of low intensity and either sublethal or innocuous. We propose that the observed variability is not only related to the large-scale environmental context in which the events occurred, but also to small-scale variability linked to local circulation, biological activity, and sediment biogeochemistry. We expect that our research will be useful not only for scientific purposes, but also for coastal resource management and aquaculture, underlining the importance of developing high-resolution oxygen monitoring systems in coastal bays.
Investigating the Effects of Suspended Algal Content, Dissolved Oxygen, and Temperature on a High-Frequency Acoustic Attenuation System in a Controlled Laboratory Environment
2024 - Noah Watson
The Single Frequency Acoustic Attenuation System (SFAAS) has been developed at the National Center for Physical Acoustics (NCPA). This system uses acoustic methods to monitor fine suspended sediment concentration in streams. Site-specific calibrations are necessary for this system, and previous research has indicated that algal concentration or dissolved oxygen concentration of water may affect collected data. Temperature, dissolved oxygen concentration, and fluorescence, used as a proxy for algal concentration, were monitored during this system’s use, and calibrations were derived to account for the effect of each of these variables on acoustic measurements. It has been shown that temperature has a significant effect on acoustic measurements, while dissolved oxygen concentration has no discernible effect. The effect of algal concentration is slight, and subject to further research.
The Single Frequency Acoustic Attenuation System (SFAAS) has been developed at the National Center for Physical Acoustics (NCPA). This system uses acoustic methods to monitor fine suspended sediment concentration in streams. Site-specific calibrations are necessary for this system, and previous research has indicated that algal concentration or dissolved oxygen concentration of water may affect collected data. Temperature, dissolved oxygen concentration, and fluorescence, used as a proxy for algal concentration, were monitored during this system’s use, and calibrations were derived to account for the effect of each of these variables on acoustic measurements. It has been shown that temperature has a significant effect on acoustic measurements, while dissolved oxygen concentration has no discernible effect. The effect of algal concentration is slight, and subject to further research.
Environmental Variability in West Lake Mangroves: A Climatology Report
2023 - Ada Pastor, Cecilie M.H. Holmboe, Olatz Pereda, Pau Giménez-Grau, Annette Baattrup-Pedersen, Tenna Riis
The aquatic eddy covariance technique is increasingly used to determine oxygen (O2) fluxes over benthic ecosystems. The technique uses O2 measuring systems that have a high temporal and numerical resolution. In this study, we performed a series of lab and field tests to assess a new optical submersible O2 meter designed for aquatic eddy covariance measurements and equipped with an existing ultra-high speed optical fiber sensor. The meter has a 16-bit digital-to-analog-signal conversion that produces a 0–5 V output at a rate up to 40 Hz. The device was paired with an acoustic Doppler velocimeter. The combined meter and fiber-optic O2 sensor's response time was significantly faster in O2-undersaturated water compared to in O2-supersaturated water (0.087 vs. 0.12 s), but still sufficiently fast for aquatic eddy covariance measurements. The O2 optode signal was not sensitive to variations in water flow or light exposure. However, the response time was affected by the direction of the flow. When the sensor tip was exposed to a flow from the back rather than the front, the response time increased by 37%. The meter's internal signal processing time was determined to be ~ 0.05 s, a delay that can be corrected for during postprocessing. In order for the built-in temperature correction to be accurate, the meter should always be submerged with the fiber-optic sensor. In multiple 21–47 h field tests, the system recorded consistently high-quality, low-noise O2 flux data. Overall, the new meter is a powerful option for collecting robust aquatic eddy covariance data.
The aquatic eddy covariance technique is increasingly used to determine oxygen (O2) fluxes over benthic ecosystems. The technique uses O2 measuring systems that have a high temporal and numerical resolution. In this study, we performed a series of lab and field tests to assess a new optical submersible O2 meter designed for aquatic eddy covariance measurements and equipped with an existing ultra-high speed optical fiber sensor. The meter has a 16-bit digital-to-analog-signal conversion that produces a 0–5 V output at a rate up to 40 Hz. The device was paired with an acoustic Doppler velocimeter. The combined meter and fiber-optic O2 sensor's response time was significantly faster in O2-undersaturated water compared to in O2-supersaturated water (0.087 vs. 0.12 s), but still sufficiently fast for aquatic eddy covariance measurements. The O2 optode signal was not sensitive to variations in water flow or light exposure. However, the response time was affected by the direction of the flow. When the sensor tip was exposed to a flow from the back rather than the front, the response time increased by 37%. The meter's internal signal processing time was determined to be ~ 0.05 s, a delay that can be corrected for during postprocessing. In order for the built-in temperature correction to be accurate, the meter should always be submerged with the fiber-optic sensor. In multiple 21–47 h field tests, the system recorded consistently high-quality, low-noise O2 flux data. Overall, the new meter is a powerful option for collecting robust aquatic eddy covariance data.
A high-resolution submersible oxygen optode system for aquatic eddy covariance
2023 - Kayleigh E. Granville, Peter Berg, Markus Huettel
The aquatic eddy covariance technique is increasingly used to determine oxygen (O2) fluxes over benthic ecosystems. The technique uses O2 measuring systems that have a high temporal and numerical resolution. In this study, we performed a series of lab and field tests to assess a new optical submersible O2 meter designed for aquatic eddy covariance measurements and equipped with an existing ultra-high speed optical fiber sensor. The meter has a 16-bit digital-to-analog-signal conversion that produces a 0–5 V output at a rate up to 40 Hz. The device was paired with an acoustic Doppler velocimeter. The combined meter and fiber-optic O2 sensor's response time was significantly faster in O2-undersaturated water compared to in O2-supersaturated water (0.087 vs. 0.12 s), but still sufficiently fast for aquatic eddy covariance measurements. The O2 optode signal was not sensitive to variations in water flow or light exposure. However, the response time was affected by the direction of the flow. When the sensor tip was exposed to a flow from the back rather than the front, the response time increased by 37%. The meter's internal signal processing time was determined to be ~ 0.05 s, a delay that can be corrected for during postprocessing. In order for the built-in temperature correction to be accurate, the meter should always be submerged with the fiber-optic sensor. In multiple 21–47 h field tests, the system recorded consistently high-quality, low-noise O2 flux data. Overall, the new meter is a powerful option for collecting robust aquatic eddy covariance data.
The aquatic eddy covariance technique is increasingly used to determine oxygen (O2) fluxes over benthic ecosystems. The technique uses O2 measuring systems that have a high temporal and numerical resolution. In this study, we performed a series of lab and field tests to assess a new optical submersible O2 meter designed for aquatic eddy covariance measurements and equipped with an existing ultra-high speed optical fiber sensor. The meter has a 16-bit digital-to-analog-signal conversion that produces a 0–5 V output at a rate up to 40 Hz. The device was paired with an acoustic Doppler velocimeter. The combined meter and fiber-optic O2 sensor's response time was significantly faster in O2-undersaturated water compared to in O2-supersaturated water (0.087 vs. 0.12 s), but still sufficiently fast for aquatic eddy covariance measurements. The O2 optode signal was not sensitive to variations in water flow or light exposure. However, the response time was affected by the direction of the flow. When the sensor tip was exposed to a flow from the back rather than the front, the response time increased by 37%. The meter's internal signal processing time was determined to be ~ 0.05 s, a delay that can be corrected for during postprocessing. In order for the built-in temperature correction to be accurate, the meter should always be submerged with the fiber-optic sensor. In multiple 21–47 h field tests, the system recorded consistently high-quality, low-noise O2 flux data. Overall, the new meter is a powerful option for collecting robust aquatic eddy covariance data.
Macrophyte removal affects nutrient uptake and metabolism in lowland streams
2023 - Ada Pastor, Cecilie M.H. Holmboe, Olatz Pereda, Pau Giménez-Grau, Annette Baattrup-Pedersen, Tenna Riis
Macrophytes provide essential ecosystem services in lowland streams, including nutrient uptake that can reduce downstream transport to vulnerable coastal areas. Despite that, to ensure water conveyance and effective run off from agricultural fields, aquatic plant biomass is removed regularly in many European streams (i.e. weed cutting practices). However, the impacts of weed cutting on stream ecosystem processes are not yet well documented. Here, we studied the effect of weed cutting on nutrient retention and ecosystem metabolism in three lowland streams with contrasting dominant vegetation communities (submergent and emergent plants) during summer in Denmark. Our results showed a decrease in nutrient retention; uptake velocity of ammonium decreased 34–77 % and of phosphate decreased 50–77 %. Ecosystem metabolic rates also decreased after weed cutting, both in gross primary production (9 %, 60 % and 85 %) and respiration (47 %, 69 % and 76 %). The effects of weed cutting on these ecosystem processes prevailed three weeks after the cutting occurred. Understanding the effects of weed cutting on stream ecosystem functioning can improve nature-based management strategies to control eutrophication of downstream coastal areas.
Macrophytes provide essential ecosystem services in lowland streams, including nutrient uptake that can reduce downstream transport to vulnerable coastal areas. Despite that, to ensure water conveyance and effective run off from agricultural fields, aquatic plant biomass is removed regularly in many European streams (i.e. weed cutting practices). However, the impacts of weed cutting on stream ecosystem processes are not yet well documented. Here, we studied the effect of weed cutting on nutrient retention and ecosystem metabolism in three lowland streams with contrasting dominant vegetation communities (submergent and emergent plants) during summer in Denmark. Our results showed a decrease in nutrient retention; uptake velocity of ammonium decreased 34–77 % and of phosphate decreased 50–77 %. Ecosystem metabolic rates also decreased after weed cutting, both in gross primary production (9 %, 60 % and 85 %) and respiration (47 %, 69 % and 76 %). The effects of weed cutting on these ecosystem processes prevailed three weeks after the cutting occurred. Understanding the effects of weed cutting on stream ecosystem functioning can improve nature-based management strategies to control eutrophication of downstream coastal areas.
Remediation of marine dead zones by enhancing microbial sulfide oxidation using electrodes
2023 - Andreas Libonati Brock, Kristin Kostadinova, Emma Mørk-Pedersen, Fides Hensel, Yifeng Zhang, Borja Valverde-Pérez, Colin A. Stedmon, Stefan Trapp
Marine dead zones caused by hypoxia have expanded over the last decades and pose a serious threat to coastal marine life. We tested sediment microbial fuel cells (SMFCs) for their potential to reduce the release of sulfide from sediments, in order to potentially protect the marine environment from the formation of such dead zones. Steel electrodes as well as charcoal-amended electrodes and corresponding non-connected controls of a size of together 24 m2 were installed in a marine harbour, and the effects on water quality were monitored for several months. Both pure steel electrodes and charcoal-amended electrodes were able to reduce sulfide concentrations in bottom water (92 % to 98 % reduction, in comparison to disconnected control steel electrodes). Also phosphate concentrations and ammonium were drastically reduced. SMFCs might be used to eliminate hypoxia at sites with high organic matter deposition and should be further investigated for this purpose.
Marine dead zones caused by hypoxia have expanded over the last decades and pose a serious threat to coastal marine life. We tested sediment microbial fuel cells (SMFCs) for their potential to reduce the release of sulfide from sediments, in order to potentially protect the marine environment from the formation of such dead zones. Steel electrodes as well as charcoal-amended electrodes and corresponding non-connected controls of a size of together 24 m2 were installed in a marine harbour, and the effects on water quality were monitored for several months. Both pure steel electrodes and charcoal-amended electrodes were able to reduce sulfide concentrations in bottom water (92 % to 98 % reduction, in comparison to disconnected control steel electrodes). Also phosphate concentrations and ammonium were drastically reduced. SMFCs might be used to eliminate hypoxia at sites with high organic matter deposition and should be further investigated for this purpose.
Disturbance of primary producer communities disrupts the thermal limits of the associated aquatic fauna
2023 -
J.M. Booth, F. Giomi, D. Daffonchio, C.D. McQuaid, M. Fusi
Environmental fluctuation forms a framework of variability within which species have evolved. Environmental fluctuation includes predictability, such as diel cycles of aquatic oxygen fluctuation driven by primary producers. Oxygen availability and fluctuation shape the physiological responses of aquatic animals to warming, so that, in theory, oxygen fluctuation could influence their thermal ecology. We describe annual oxygen variability in agricultural drainage channels and show that disruption of oxygen fluctuation through dredging of plants reduces the thermal tolerance of freshwater animals.
Environmental fluctuation forms a framework of variability within which species have evolved. Environmental fluctuation includes predictability, such as diel cycles of aquatic oxygen fluctuation driven by primary producers. Oxygen availability and fluctuation shape the physiological responses of aquatic animals to warming, so that, in theory, oxygen fluctuation could influence their thermal ecology. We describe annual oxygen variability in agricultural drainage channels and show that disruption of oxygen fluctuation through dredging of plants reduces the thermal tolerance of freshwater animals.
The effect of water management and ratoon rice cropping on methane emissions and yield in Arkansas
2023 - Marguerita Leavitt, Beatriz Moreno-García, Colby W. Reavis, Michele L. Reba, Benjamin R.K. Runkle
Sustainable intensification of rice farming is crucial to meeting human food needs while reducing environmental impacts. Rice production represents 8% of all anthropogenic emissions of CH4, a potent greenhouse gas. Cultivation practices that minimize the number of days the rice fields are flooded, such as irrigation using the alternate wetting and drying (AWD) technique instead of continuous flooding (DF) can potentially reduce CH4 emissions. Ratoon cropping, wherein a second crop of rice is grown from the harvested stubble of the first crop, can produce additional yield with minimal labor but may generate more CH4 than single cropping.
Sustainable intensification of rice farming is crucial to meeting human food needs while reducing environmental impacts. Rice production represents 8% of all anthropogenic emissions of CH4, a potent greenhouse gas. Cultivation practices that minimize the number of days the rice fields are flooded, such as irrigation using the alternate wetting and drying (AWD) technique instead of continuous flooding (DF) can potentially reduce CH4 emissions. Ratoon cropping, wherein a second crop of rice is grown from the harvested stubble of the first crop, can produce additional yield with minimal labor but may generate more CH4 than single cropping.
Effects of flow, water quality, and hypoxia on threatened Salish sucker (Catostomus sp. cf. catostomus) and juvenile coho salmon (Oncorhynchus kisutch)
2022 - Kaitlyn R. Zinn
The Salish sucker (Catostomus sp. cf. catostomus) is a federally Threatened species under Canada’s Species at Risk Act and is restricted to 11 watersheds in British Columbia (lower Fraser River Valley) and six in Washington State. Agricultural development has been historically prominent in these areas, and hypoxia and the physical destruction of habitat have been identified as the most important threats to this species. Synergistic effects of reduced streamflow, nutrient inputs, and high temperatures are likely large determinants of seasonal hypoxia. The effects of stream flow on temperature and dissolved oxygen in Salish sucker critical habitat, and corresponding changes in habitat use, distribution, and growth of Salish sucker were studied. As salmonids are even more sensitive to impaired water quality than suckers, and maintaining salmonid populations is an additional major conservation concern in the lower Fraser Valley, the biological response of juvenile coho salmon was also studied as they co-occur in Salish sucker habitats. Through various flow manipulation and enclosure experiments I found that severely reducing flow in off-channel ponds resulted in low levels of dissolved oxygen (< 3 mg/L). Salish sucker showed variable growth rate differences in flow and no-flow treatments, while juvenile coho salmon showed significantly decreased growth under the no flow treatment. A subset of fish were tagged with a passive integrated transponder (PIT), and their movement into an enclosed oxygenated refuge was studied. Salish sucker and coho salmon both made greater use of the oxygenated refuge under the no flow treatment. Salish sucker use of the oxygenated refuge was highest at night. It is likely that the availability of an oxygenated refuge in all treatments mitigated negative impacts of reduced water quality on Salish sucker. The results of my thesis will help inform the potential costs and benefits of flow reduction or flow enhancement, and the potential impacts of altered flows in a changing climate.
The Salish sucker (Catostomus sp. cf. catostomus) is a federally Threatened species under Canada’s Species at Risk Act and is restricted to 11 watersheds in British Columbia (lower Fraser River Valley) and six in Washington State. Agricultural development has been historically prominent in these areas, and hypoxia and the physical destruction of habitat have been identified as the most important threats to this species. Synergistic effects of reduced streamflow, nutrient inputs, and high temperatures are likely large determinants of seasonal hypoxia. The effects of stream flow on temperature and dissolved oxygen in Salish sucker critical habitat, and corresponding changes in habitat use, distribution, and growth of Salish sucker were studied. As salmonids are even more sensitive to impaired water quality than suckers, and maintaining salmonid populations is an additional major conservation concern in the lower Fraser Valley, the biological response of juvenile coho salmon was also studied as they co-occur in Salish sucker habitats. Through various flow manipulation and enclosure experiments I found that severely reducing flow in off-channel ponds resulted in low levels of dissolved oxygen (< 3 mg/L). Salish sucker showed variable growth rate differences in flow and no-flow treatments, while juvenile coho salmon showed significantly decreased growth under the no flow treatment. A subset of fish were tagged with a passive integrated transponder (PIT), and their movement into an enclosed oxygenated refuge was studied. Salish sucker and coho salmon both made greater use of the oxygenated refuge under the no flow treatment. Salish sucker use of the oxygenated refuge was highest at night. It is likely that the availability of an oxygenated refuge in all treatments mitigated negative impacts of reduced water quality on Salish sucker. The results of my thesis will help inform the potential costs and benefits of flow reduction or flow enhancement, and the potential impacts of altered flows in a changing climate.
A mobile observatory powered by sun and wind for near real time measurements of atmospheric, glacial, terrestrial, limnic and coastal oceanic conditions in remote off-grid areas
2022 - Søren Rysgaard, Kim Bjerge, Wieter Boone , Egon Frandsen, Michael Graversen c, Toke Thomas Høye, Bjarne Jensenm Geoffrey Johnen, Marcin Antoni Jackowicz-Korczynski, Jeffrey Taylor Kerby, Simon Kortegaard, Mikhail Mastepanov, Claus Melvad, Peter Schmidt Mikkelsen, Keld Mortensen, Carsten Nørgaard, Ebbe Poulsen, Tenna Riis, Lotte Sørensen, Torben Røjle Christensen
Climate change is rapidly altering the Arctic environment. Although long-term environmental observations have been made at a few locations in the Arctic, the incomplete coverage from ground stations is a main limitation to observations in these remote areas. Here we present a wind and sun powered multi-purpose mobile observatory (ARC-MO) that enables near real time measurements of air, ice, land, rivers, and marine parameters in remote off-grid areas. Two test units were constructed and placed in Northeast Greenland where they have collected data from cabled and wireless instruments deployed in the environment since late summer 2021. The two units can communicate locally via WiFi (units placed 25 km apart) and transmit near-real time data globally over satellite. Data are streamed live and accessible from (https://gios.org). The cost of one mobile observatory unit is c. 304.000€. These test units demonstrate the possibility for integrative and automated environmental data collection in remote coastal areas and could serve as models for a proposed global observatory system.
Climate change is rapidly altering the Arctic environment. Although long-term environmental observations have been made at a few locations in the Arctic, the incomplete coverage from ground stations is a main limitation to observations in these remote areas. Here we present a wind and sun powered multi-purpose mobile observatory (ARC-MO) that enables near real time measurements of air, ice, land, rivers, and marine parameters in remote off-grid areas. Two test units were constructed and placed in Northeast Greenland where they have collected data from cabled and wireless instruments deployed in the environment since late summer 2021. The two units can communicate locally via WiFi (units placed 25 km apart) and transmit near-real time data globally over satellite. Data are streamed live and accessible from (https://gios.org). The cost of one mobile observatory unit is c. 304.000€. These test units demonstrate the possibility for integrative and automated environmental data collection in remote coastal areas and could serve as models for a proposed global observatory system.
Experimental reductions in subdaily flow fluctuations increased gross primary productivity for 425 river kilometers downstream
2022 - Bridget R Deemer, Charles B Yackulic, Robert O Hall, Jr, Michael J Dodrill, Theodore A Kennedy, Jeffrey D Muehlbauer, David J Topping, Nicholas Voichick, Michael D Yard
Aquatic primary production is the foundation of many river food webs. Dams change the physical template of rivers, often driving food webs toward greater reliance on aquatic primary production. Nonetheless, the effects of regulated flow regimes on primary production are poorly understood. Load following is a common dam flow management strategy that involves subdaily changes in water releases proportional to fluctuations in electrical power demand. This flow regime causes an artificial tide, wetting and drying channel margins and altering river depth and water clarity, all processes that are likely to affect primary production.
Aquatic primary production is the foundation of many river food webs. Dams change the physical template of rivers, often driving food webs toward greater reliance on aquatic primary production. Nonetheless, the effects of regulated flow regimes on primary production are poorly understood. Load following is a common dam flow management strategy that involves subdaily changes in water releases proportional to fluctuations in electrical power demand. This flow regime causes an artificial tide, wetting and drying channel margins and altering river depth and water clarity, all processes that are likely to affect primary production.
Is All Seagrass Habitat Equal? Seasonal, Spatial, and Interspecific Variation in Productivity Dynamics Within Mediterranean Seagrass Habitat
2022 - Emma A. Ward, Charlotte Aldis, Tom Wade, Anastasia Miliou, Thodoris Tsimpidis, Tom C. Cameron
Seagrass meadows’ ability to capture carbon through sequestering autochthonous carbon via photosynthesis means they could represent a potential nature-based solution to rising carbon emissions. In multispecies seagrass communities, and due to species introduction or predicted range shifts, it is important to know which species deliver different carbon sequestration gains to inform conservation actions. Large benthic chamber experiments (volume = 262L) assessed the seasonal and spatial variation in metabolism dynamics of the endemic and dominant Mediterranean seagrass, P. oceanica whilst small benthic chamber experiments (volume = 7L) compared the dynamics between, P. oceanica the native C. nodosa and non-native H. stipulacea.
Seagrass meadows’ ability to capture carbon through sequestering autochthonous carbon via photosynthesis means they could represent a potential nature-based solution to rising carbon emissions. In multispecies seagrass communities, and due to species introduction or predicted range shifts, it is important to know which species deliver different carbon sequestration gains to inform conservation actions. Large benthic chamber experiments (volume = 262L) assessed the seasonal and spatial variation in metabolism dynamics of the endemic and dominant Mediterranean seagrass, P. oceanica whilst small benthic chamber experiments (volume = 7L) compared the dynamics between, P. oceanica the native C. nodosa and non-native H. stipulacea.
Dissolved organic matter mediates the effects of warming and inorganic nutrients on a lake planktonic food web
2022 - Marie-Pier Hébert, Cynthia Soued, Gregor F. Fussmann, Beatrix E. Beisner
Lakes are undergoing striking physicochemical changes globally, including co-occurring increases in dissolved organic carbon and nutrient concentrations, water color, and surface temperature. Although several experimental studies of lake browning and warming have been conducted over the last decade, knowledge remains limited as to the structural and functional responses of multitrophic plankton communities, especially under environmentally relevant physicochemical conditions. Using reverse osmosis to manipulate naturally occurring dissolved organic matter (DOM), we performed an enclosure experiment to evaluate the response of a planktonic food web (zooplankton–phytoplankton–bacterioplankton) to individual and combined increases in DOM and temperature, while accounting for changes in inorganic nutrients associated with DOM enrichment. We found that concomitant increases in DOM and temperature or inorganic nutrients elicited substantially greater biotic effects, but infrequently led to interactive effects. Overall, major plankton groups responded differently to manipulated factors, with most effects observed in standing stocks, community composition, and trophic structure, while metabolic (primary production and respiration) rates appeared to be generally less responsive.
Lakes are undergoing striking physicochemical changes globally, including co-occurring increases in dissolved organic carbon and nutrient concentrations, water color, and surface temperature. Although several experimental studies of lake browning and warming have been conducted over the last decade, knowledge remains limited as to the structural and functional responses of multitrophic plankton communities, especially under environmentally relevant physicochemical conditions. Using reverse osmosis to manipulate naturally occurring dissolved organic matter (DOM), we performed an enclosure experiment to evaluate the response of a planktonic food web (zooplankton–phytoplankton–bacterioplankton) to individual and combined increases in DOM and temperature, while accounting for changes in inorganic nutrients associated with DOM enrichment. We found that concomitant increases in DOM and temperature or inorganic nutrients elicited substantially greater biotic effects, but infrequently led to interactive effects. Overall, major plankton groups responded differently to manipulated factors, with most effects observed in standing stocks, community composition, and trophic structure, while metabolic (primary production and respiration) rates appeared to be generally less responsive.
Contribution of boulder reef habitats to oxygen dynamics of a shallow estuary
2022 - Peter A.U. Staehr, Sanjina U. Staehr, Denise Tonetta, Signe Høgslund, Mette Møller Nielsen
We assessed the importance of boulder reefs to the oxygen dynamics of a shallow estuary during two growing seasons in 2017 and 2018. Using open-system diel oxygen measurements and benthic and pelagic incubations, we evaluated the relative contribution of pelagic and benthic habitats to the ecosystem metabolism along a depth gradient in two areas, with (Reef) and without (Bare) boulder reefs in the Limfjorden, Denmark. System integrated areal rates of gross primary production (GPP) and ecosystem respiration (ER) both increased with depth in both areas.
We assessed the importance of boulder reefs to the oxygen dynamics of a shallow estuary during two growing seasons in 2017 and 2018. Using open-system diel oxygen measurements and benthic and pelagic incubations, we evaluated the relative contribution of pelagic and benthic habitats to the ecosystem metabolism along a depth gradient in two areas, with (Reef) and without (Bare) boulder reefs in the Limfjorden, Denmark. System integrated areal rates of gross primary production (GPP) and ecosystem respiration (ER) both increased with depth in both areas.
Solar circulator to restore dissolved oxygen in a hypoxic ice-covered lake
2022 - Kyle F. Flynn , Kyle A. Cutting, Matthew E. Jaeger, Jeffrey M. Warren, Theodore Johnson, Darrin Kron, Chace Bell
Hypoxia is common to shallow ice-covered lakes during the winter season, and restorative actions to prevent impacts to aquatic ecosystems are desired yet untested in remote settings. The use of a solar photovoltaic circulator was investigated for reoxygenation in a shallow hypoxic lake in the northern Rocky Mountains. During the fall of 2019, a solar powered lake circulator (SolarBee SB10000LH; hereinafter circulator) was installed near the center of Upper Red Rock Lake, Montana USA (latitude 44° 36’N) and dissolved oxygen (DO), temperature, turbidity, and changes to ice formation were monitored until ice-out the following spring of 2020 using an array of real-time and data logging sondes. Observations indicate the circulator formed a polynya that lasted until late November, did not increase lake turbidity, and facilitated oxygen exchange through the circulator-created-polynya for at least 3 weeks after an adjacent lake became ice covered.
Hypoxia is common to shallow ice-covered lakes during the winter season, and restorative actions to prevent impacts to aquatic ecosystems are desired yet untested in remote settings. The use of a solar photovoltaic circulator was investigated for reoxygenation in a shallow hypoxic lake in the northern Rocky Mountains. During the fall of 2019, a solar powered lake circulator (SolarBee SB10000LH; hereinafter circulator) was installed near the center of Upper Red Rock Lake, Montana USA (latitude 44° 36’N) and dissolved oxygen (DO), temperature, turbidity, and changes to ice formation were monitored until ice-out the following spring of 2020 using an array of real-time and data logging sondes. Observations indicate the circulator formed a polynya that lasted until late November, did not increase lake turbidity, and facilitated oxygen exchange through the circulator-created-polynya for at least 3 weeks after an adjacent lake became ice covered.
Seasonality and biological forcing modify the diel frequency of nearshore pH extremes in a subarctic Alaskan estuary
2021 - Cale A. Miller, Amanda L. Kelley
Acidification in nearshore waters is influenced by a multitude of drivers that shape the dynamics of pH and carbonate chemistry variability on diurnal, seasonal, and yearly time scales. Monitoring efforts aimed at characterizing high temporal variability are lacking in many nearshore systems, particularly in high-latitude regions such as Alaska. To rectify this, a nearshore acidification sensor array was established in the Fall of 2017 within Kachemak Bay, Alaska. Presented here are the results from the first year of these deployments, and the first record of a year-long high-frequency pH time series for nearshore Alaska. SeaFET™ pH and O2 sensors deployed in Jakolof Bay and Bear Cove reveal a seasonally dynamic system in which nearshore waters in these two enclosed bays transition to being predominantly net autotrophic systems for a period of 60-plus days. High rates and durations of primary production in late spring and early summer create high pH conditions and extreme variability. Observed pH values in Jakolof Bay and Bear Cove tracked hourly rates of change on the order of 0.18 and 0.10 units, respectively. In Jakolof Bay nondirectional variability within a 12-h period was > 1 pH unit, exposing organisms to unstable, nonstatic pH conditions on tidal and diurnal cycles. Consistent frequency patterns detailing the magnitude of pH variability was correlated to tidal and O2 signatures, elucidating the dynamics and drivers of pH variability. This first year of observations is the first step in quantifying the anthropogenic contribution to acidification for Kachemak Bay in the forthcoming years.
Acidification in nearshore waters is influenced by a multitude of drivers that shape the dynamics of pH and carbonate chemistry variability on diurnal, seasonal, and yearly time scales. Monitoring efforts aimed at characterizing high temporal variability are lacking in many nearshore systems, particularly in high-latitude regions such as Alaska. To rectify this, a nearshore acidification sensor array was established in the Fall of 2017 within Kachemak Bay, Alaska. Presented here are the results from the first year of these deployments, and the first record of a year-long high-frequency pH time series for nearshore Alaska. SeaFET™ pH and O2 sensors deployed in Jakolof Bay and Bear Cove reveal a seasonally dynamic system in which nearshore waters in these two enclosed bays transition to being predominantly net autotrophic systems for a period of 60-plus days. High rates and durations of primary production in late spring and early summer create high pH conditions and extreme variability. Observed pH values in Jakolof Bay and Bear Cove tracked hourly rates of change on the order of 0.18 and 0.10 units, respectively. In Jakolof Bay nondirectional variability within a 12-h period was > 1 pH unit, exposing organisms to unstable, nonstatic pH conditions on tidal and diurnal cycles. Consistent frequency patterns detailing the magnitude of pH variability was correlated to tidal and O2 signatures, elucidating the dynamics and drivers of pH variability. This first year of observations is the first step in quantifying the anthropogenic contribution to acidification for Kachemak Bay in the forthcoming years.
Characterization of the abiotic drivers of abundance of nearshore Arctic fishes
2021 - Noah S. Khalsa, Kyle P. Gatt, Trent M. Sutton, Amanda L. Kelley
Fish are critical ecologically and socioeconomically for subsistence economies in the Arctic, an ecosystem undergoing unprecedented environmental change. Our understanding of the responses of nearshore Arctic fishes to environmental change is inadequate because of limited research on the physicochemical drivers of abundance occurring at a fine scale. Here, high-frequency in situ measurements of pH, temperature, salinity, and dissolved oxygen were paired with daily fish catches in nearshore Alaskan waters of the Beaufort Sea. Due to the threat that climate change poses to high-latitude marine ecosystems, our main objective was to characterize the abiotic drivers of abundance and elucidate how nearshore fish communities may change in the future. We used generalized additive models (GAMs) to describe responses to the nearshore environment for 18 fish species.
Fish are critical ecologically and socioeconomically for subsistence economies in the Arctic, an ecosystem undergoing unprecedented environmental change. Our understanding of the responses of nearshore Arctic fishes to environmental change is inadequate because of limited research on the physicochemical drivers of abundance occurring at a fine scale. Here, high-frequency in situ measurements of pH, temperature, salinity, and dissolved oxygen were paired with daily fish catches in nearshore Alaskan waters of the Beaufort Sea. Due to the threat that climate change poses to high-latitude marine ecosystems, our main objective was to characterize the abiotic drivers of abundance and elucidate how nearshore fish communities may change in the future. We used generalized additive models (GAMs) to describe responses to the nearshore environment for 18 fish species.
Large spatiotemporal variability in metabolic regimes for an urban stream draining four wastewater treatment plants with implications for dissolved oxygen monitoring
2021 - Sarah H. Ledford, Jacob S. Diamond, Laura Toran
Urbanization and subsequent expansion of wastewater treatment plant (WWTP) capacity has the potential to alter stream metabolic regimes, but the magnitude of this change remains unknown. Indeed, our understanding of downstream WWTP effects on stream metabolism is spatially and temporally limited, and monitoring designs with upstream-downstream comparison sites are rare. Despite this, and despite observed spatiotemporal variability in stream metabolic regimes, regulators typically use snapshot monitoring to assess ecosystem function in receiving streams, potentially leading to biased conclusions about stream health.
Urbanization and subsequent expansion of wastewater treatment plant (WWTP) capacity has the potential to alter stream metabolic regimes, but the magnitude of this change remains unknown. Indeed, our understanding of downstream WWTP effects on stream metabolism is spatially and temporally limited, and monitoring designs with upstream-downstream comparison sites are rare. Despite this, and despite observed spatiotemporal variability in stream metabolic regimes, regulators typically use snapshot monitoring to assess ecosystem function in receiving streams, potentially leading to biased conclusions about stream health.
Testing angular velocity as a new metric for metabolic demands of slow-moving marine fauna: a case study with Giant spider conchs Lambis truncata
2021 - Lloyd W. Hopkins, Nathan R. Geraldi, Edward C. Pope, Mark D. Holton, Miguel Lurgi, Carlos M. Duarte & Rory P. Wilson
Quantifying metabolic rate in free-living animals is invaluable in understanding the costs of behaviour and movement for individuals and communities. Dynamic body acceleration (DBA) metrics, such as vectoral DBA (VeDBA), are commonly used as proxies for the energy expenditure of movement but are of limited applicability for slow-moving species. It has recently been suggested that metrics based on angular velocity might be better suited to characterize their energetics.
Quantifying metabolic rate in free-living animals is invaluable in understanding the costs of behaviour and movement for individuals and communities. Dynamic body acceleration (DBA) metrics, such as vectoral DBA (VeDBA), are commonly used as proxies for the energy expenditure of movement but are of limited applicability for slow-moving species. It has recently been suggested that metrics based on angular velocity might be better suited to characterize their energetics.
Carcass deposition to suppress invasive lake trout causes differential mortality of two common benthic invertebrates in Yellowstone Lake
2020 - Michelle A. Briggs, Lindsey K.Albertson, Dominique R. Lujan, Lusha M. Tronstad, Hayley C. Glassic, Christopher S. Guy, Todd M. Koel
Invasive species require management to mitigate their harmful effects on native biodiversity and ecosystem processes. However, such management can also have negative, unintended consequences on non-target taxa, ecosystem processes, and food web dynamics. In Yellowstone Lake, invasive lake trout (Salvelinus namaycush) have caused a decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) population. To suppress the invader, lake trout carcasses are deposited on the species’ spawning sites, causing embryo mortality by reducing dissolved oxygen as they decay. The non-target effects of carcass deposition are unknown, but benthic invertebrates may be sensitive to reductions in dissolved oxygen.
Invasive species require management to mitigate their harmful effects on native biodiversity and ecosystem processes. However, such management can also have negative, unintended consequences on non-target taxa, ecosystem processes, and food web dynamics. In Yellowstone Lake, invasive lake trout (Salvelinus namaycush) have caused a decline in the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) population. To suppress the invader, lake trout carcasses are deposited on the species’ spawning sites, causing embryo mortality by reducing dissolved oxygen as they decay. The non-target effects of carcass deposition are unknown, but benthic invertebrates may be sensitive to reductions in dissolved oxygen.
In situ pelagic dataset from continuous monitoring: A mesocosm experiment in Lake Geneva (MESOLAC)
2020 - Viet Tran-Khac, Philippe Quetin, Isabelle Domaizon, Stéphan Jacquet, Laurent Espinat, Clémentine Gallot, Serena Rasconi
This dataset corresponds to a data series produced from automated data loggers during the MESOLAC experimental project. Nine pelagic mesocosms (about 3000 L, 3 m depth) were deployed in July 2019 in Lake Geneva near the shore of Thonon les Bains (France), simulating predicted climate scenarios (i.e. intense weather events) by applying a combination of forcing. The design consisted of three treatments each replicated three times: a control treatment (named C – no treatment applied) and two different treatments simulating different intensities of weather events. The high intensity treatment (named H) aimed to reproduce short and intense weather events such as violent storms. It consisted of a short-term stress applied during the first week, with high pulse of dissolved organic carbon (5x increased concentration, i.e. total DOC ∼ 6 mg L−1), transmitted light reduced to 15% and water column manual mixing. The medium intensity treatment (named M) simulated less intense and more prolonged exposures such as during flood events. It was maintained during the 4 weeks of the experiment and consisted of 1.5x increased concentration of dissolved organic carbon (i.e. total DOC ∼ 2 mg L−1), 70% transmitted light and water column manual mixing. Automated data loggers were placed for the entire period of the experiment in the mesocosms and in the lake for comparison with natural conditions. Temperature, conductivity, dissolved oxygen and CO2 were monitored every 15 min at different depths (0.15, 0.25, 1 and 2 m).
This dataset corresponds to a data series produced from automated data loggers during the MESOLAC experimental project. Nine pelagic mesocosms (about 3000 L, 3 m depth) were deployed in July 2019 in Lake Geneva near the shore of Thonon les Bains (France), simulating predicted climate scenarios (i.e. intense weather events) by applying a combination of forcing. The design consisted of three treatments each replicated three times: a control treatment (named C – no treatment applied) and two different treatments simulating different intensities of weather events. The high intensity treatment (named H) aimed to reproduce short and intense weather events such as violent storms. It consisted of a short-term stress applied during the first week, with high pulse of dissolved organic carbon (5x increased concentration, i.e. total DOC ∼ 6 mg L−1), transmitted light reduced to 15% and water column manual mixing. The medium intensity treatment (named M) simulated less intense and more prolonged exposures such as during flood events. It was maintained during the 4 weeks of the experiment and consisted of 1.5x increased concentration of dissolved organic carbon (i.e. total DOC ∼ 2 mg L−1), 70% transmitted light and water column manual mixing. Automated data loggers were placed for the entire period of the experiment in the mesocosms and in the lake for comparison with natural conditions. Temperature, conductivity, dissolved oxygen and CO2 were monitored every 15 min at different depths (0.15, 0.25, 1 and 2 m).
The Southampton Island Marine Ecosystem Project, 2019 Cruise Report, 2-29 August, MV William Kennedy
2020 - Gretchen M. Spencer
Sea level rise, ocean acidification, increasing sea temperatures, and deoxygenation are all consequences of climate change that are impacting the ocean. However, nearshore environments are being affected by climate change at varying rates compared to the open ocean. Mangroves, environments which already see wide variety in their daily environmental conditions due to the natural physical and biogeochemical processes which occur in them, are habitats that are expected to change at a faster rate than other ecosystems. The goal of this study was to create a baseline understanding of the daily, monthly, and seasonal changes occurring in a local mangrove habitat, to help understand what impacts climate change may have on the system in the future. Using a stationary Smart Spotter buoy in West Lake (Hollywood, FL), temperature and dissolved oxygen was measured to create hourly climatologies of the lake. Daily and seasonal trends were found for both temperature and percent dissolved oxygen. The summer, or wet season, shows overall warmer sea surface temperatures and lower average amounts of oxygen. The winter, or dry season, shows overall lower sea surface temperatures and higher amounts of oxygen. The results indicate the solar irradiance plays a large part in controlling the sea surface temperature, where biological processes (photosynthesis and respiration) influence the percent dissolved oxygen. More studies on nearshore systems, like mangroves, need to be conducted to better understand how natural diel changes will be impacted by large scale environmental changes to protect the organisms living in those habitats.
Sea level rise, ocean acidification, increasing sea temperatures, and deoxygenation are all consequences of climate change that are impacting the ocean. However, nearshore environments are being affected by climate change at varying rates compared to the open ocean. Mangroves, environments which already see wide variety in their daily environmental conditions due to the natural physical and biogeochemical processes which occur in them, are habitats that are expected to change at a faster rate than other ecosystems. The goal of this study was to create a baseline understanding of the daily, monthly, and seasonal changes occurring in a local mangrove habitat, to help understand what impacts climate change may have on the system in the future. Using a stationary Smart Spotter buoy in West Lake (Hollywood, FL), temperature and dissolved oxygen was measured to create hourly climatologies of the lake. Daily and seasonal trends were found for both temperature and percent dissolved oxygen. The summer, or wet season, shows overall warmer sea surface temperatures and lower average amounts of oxygen. The winter, or dry season, shows overall lower sea surface temperatures and higher amounts of oxygen. The results indicate the solar irradiance plays a large part in controlling the sea surface temperature, where biological processes (photosynthesis and respiration) influence the percent dissolved oxygen. More studies on nearshore systems, like mangroves, need to be conducted to better understand how natural diel changes will be impacted by large scale environmental changes to protect the organisms living in those habitats.
Drought alters the biogeochemistry of boreal stream networks
2020 - Lluís Gómez-Gener, Anna Lupon, Hjalmar Laudon & Ryan A. Sponseller
Drought is a global phenomenon, with widespread implications for freshwater ecosystems. While droughts receive much attention at lower latitudes, their effects on northern river networks remain unstudied. We combine a reach-scale manipulation experiment, observations during the extreme 2018 drought, and historical monitoring data to examine the impact of drought in northern boreal streams. Increased water residence time during drought promoted reductions in aerobic metabolism and increased concentrations of reduced solutes in both stream and hyporheic water.
Drought is a global phenomenon, with widespread implications for freshwater ecosystems. While droughts receive much attention at lower latitudes, their effects on northern river networks remain unstudied. We combine a reach-scale manipulation experiment, observations during the extreme 2018 drought, and historical monitoring data to examine the impact of drought in northern boreal streams. Increased water residence time during drought promoted reductions in aerobic metabolism and increased concentrations of reduced solutes in both stream and hyporheic water.
The Southampton Island Marine Ecosystem Project, 2019 Cruise Report
2019 - C.J. Mundy
Climate warming is forcing rapid change to Canada’s marine Arctic icescape (Hochheim and Barber 2010) and its associated ecosystem, while the increasing ice-free season is supporting an ever-increasing industrial presence in the North. With over two-thirds of Canada’s coastline being located in the North and the fact that nearshore waters represent some of the most productive Arctic regions, there is a need to improve our understanding of marine ecosystem processes in the sensitive Arctic coastal zone. The marine region around Southampton Island, northwest Hudson Bay (Nunavut), encompasses one of Canada’s largest summer and winter aggregations of Arctic marine mammals, providing multiple ecosystem services. This biological hotspot has supported local human habitation for millennia with confirmed Dorset, Thule, and Sadlermiut occupation sites (Collins 1956; Clark 1980; McGhee 1970), and is still crucial to the subsistence economy of local communities today. The region has also been a marine mammal management focus of Fisheries and Oceans Canada (DFO) for decades and supports two sea bird sanctuaries, yet we know surprisingly little of the region’s oceanography, productivity or biological community below these top trophic levels. This fact highlights a major management risk, severely limiting our ability to understand and predict changes to this unique and productive marine ecosystem. Exacerbating this risk are pressures posed by the ongoing climate changes and an increasing industrial presence. Therefore, we undertook an oceanographic study called the Southampton Island Marine Ecosystem Project (SIMEP), funded by the MEOPAR Network of Centres of Excellence (NCE).
Climate warming is forcing rapid change to Canada’s marine Arctic icescape (Hochheim and Barber 2010) and its associated ecosystem, while the increasing ice-free season is supporting an ever-increasing industrial presence in the North. With over two-thirds of Canada’s coastline being located in the North and the fact that nearshore waters represent some of the most productive Arctic regions, there is a need to improve our understanding of marine ecosystem processes in the sensitive Arctic coastal zone. The marine region around Southampton Island, northwest Hudson Bay (Nunavut), encompasses one of Canada’s largest summer and winter aggregations of Arctic marine mammals, providing multiple ecosystem services. This biological hotspot has supported local human habitation for millennia with confirmed Dorset, Thule, and Sadlermiut occupation sites (Collins 1956; Clark 1980; McGhee 1970), and is still crucial to the subsistence economy of local communities today. The region has also been a marine mammal management focus of Fisheries and Oceans Canada (DFO) for decades and supports two sea bird sanctuaries, yet we know surprisingly little of the region’s oceanography, productivity or biological community below these top trophic levels. This fact highlights a major management risk, severely limiting our ability to understand and predict changes to this unique and productive marine ecosystem. Exacerbating this risk are pressures posed by the ongoing climate changes and an increasing industrial presence. Therefore, we undertook an oceanographic study called the Southampton Island Marine Ecosystem Project (SIMEP), funded by the MEOPAR Network of Centres of Excellence (NCE).
Organic Pellet Decomposition Induces Mortality of Lake Trout Embryos in Yellowstone Lake
2019 - Todd M. Koel, Nathan A. Thomas, Christopher S. Guy, Philip D. Doepke, Drew J. MacDonald, Alex S. Poole, Wendy M. Sealey, Alexander V. Zale
Yellowstone Lake is the site of actions to suppress invasive Lake Trout Salvelinus namaycush and restore native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri and natural ecosystem function. Although gill netting is effective (Lake Trout λ ≤ 0.6 from 2012 through 2018), the effort costs more than US$2 million annually and only targets Lake Trout age 2 and older. To increase suppression efficiency, we developed an alternative method using organic (soy and wheat) pellets to increase mortality of Lake Trout embryos on spawning sites.
Yellowstone Lake is the site of actions to suppress invasive Lake Trout Salvelinus namaycush and restore native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri and natural ecosystem function. Although gill netting is effective (Lake Trout λ ≤ 0.6 from 2012 through 2018), the effort costs more than US$2 million annually and only targets Lake Trout age 2 and older. To increase suppression efficiency, we developed an alternative method using organic (soy and wheat) pellets to increase mortality of Lake Trout embryos on spawning sites.
Oxygen supersaturation protects coastal marine fauna from ocean warming
2019 - Folco Giomi, Alberto Barausse, Carlos M. Duarte, Susana Agusti, Vincent Saderne, Andrea Anton, Daniele Daffonchio
Ocean warming affects the life history and fitness of marine organisms by, among others, increasing animal metabolism and reducing oxygen availability. In coastal habitats, animals live in close association with photosynthetic organisms whose oxygen supply supports metabolic demands and may compensate for acute warming. Using a unique high-frequency monitoring dataset, we show that oxygen supersaturation resulting from photosynthesis closely parallels sea temperature rise during diel cycles in Red Sea coastal habitats.
Ocean warming affects the life history and fitness of marine organisms by, among others, increasing animal metabolism and reducing oxygen availability. In coastal habitats, animals live in close association with photosynthetic organisms whose oxygen supply supports metabolic demands and may compensate for acute warming. Using a unique high-frequency monitoring dataset, we show that oxygen supersaturation resulting from photosynthesis closely parallels sea temperature rise during diel cycles in Red Sea coastal habitats.
Environmental parameters of shallow water habitats in the SW Baltic Sea
2019 - Markus Franz, Christian Lieberum, Gesche Bock, and Rolf Karez
The coastal waters of the Baltic Sea are subject to high variations in environmental conditions, triggered by natural and anthropogenic causes. Thus, in situ measurements of water parameters can be strategic for our understanding of the dynamics in shallow water habitats. In this study we present the results of a monitoring program at low water depths (1–2.5 m), covering 13 stations along the Baltic coast of Schleswig-Holstein, Germany.
The coastal waters of the Baltic Sea are subject to high variations in environmental conditions, triggered by natural and anthropogenic causes. Thus, in situ measurements of water parameters can be strategic for our understanding of the dynamics in shallow water habitats. In this study we present the results of a monitoring program at low water depths (1–2.5 m), covering 13 stations along the Baltic coast of Schleswig-Holstein, Germany.
Thermal dependence of seagrass ecosystem metabolism in the Red Sea
2019 - Celina Burkholz, Carlos M. Duarte, Neus Garcias-Bonet
The Red Sea is one of the warmest seas with shallow seagrass ecosystems exposed to extreme temperatures, in excess of 35°C, during the summer months. Seagrass meadows are net autotrophic ecosystems, but respiration increases faster than primary production with temperature. This may lead to a shift from an autotrophic to a heterotrophic system at the highest temperatures. Although tropical seagrasses are adapted to high temperatures, the metabolic rates of Red Sea seagrasses have not yet been reported. Here we assessed the community metabolism of 2 seagrass ecosystems, an Enhalus acoroides monospecific meadow and a Cymodocea serrulata and Halodule uninervis mixed meadow, located in the central Red Sea.
The Red Sea is one of the warmest seas with shallow seagrass ecosystems exposed to extreme temperatures, in excess of 35°C, during the summer months. Seagrass meadows are net autotrophic ecosystems, but respiration increases faster than primary production with temperature. This may lead to a shift from an autotrophic to a heterotrophic system at the highest temperatures. Although tropical seagrasses are adapted to high temperatures, the metabolic rates of Red Sea seagrasses have not yet been reported. Here we assessed the community metabolism of 2 seagrass ecosystems, an Enhalus acoroides monospecific meadow and a Cymodocea serrulata and Halodule uninervis mixed meadow, located in the central Red Sea.
Oxycline oscillations induced by internal waves in deep Lake Iseo
2019 - Giulia Valerio, Marco Pilotti, Maximilian Peter Lau, and Michael Hupfer
Lake Iseo is undergoing a dramatic deoxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the pre-alpine area that are, to a different extent, undergoing reduced deep-water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments are a major concern.
Lake Iseo is undergoing a dramatic deoxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the pre-alpine area that are, to a different extent, undergoing reduced deep-water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments are a major concern.
A network model for primary production highlights linkages between salmonid populations and autochthonous resources
2018 - W. Carl Saunders, Nicolaas Bouwes, Peter McHugh, Chris E. Jordan
Spatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources.
Spatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources.
Atmospheric stilling leads to prolonged thermal stratification in a large shallow polymictic lake
2017 - R. Iestyn Woolway, Pille Meinson, Peeter Nõges, Ian D. Jones & Alo Laas
To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures.
To quantify the effects of recent and potential future decreases in surface wind speeds on lake thermal stratification, we apply the one-dimensional process-based model MyLake to a large, shallow, polymictic lake, Võrtsjärv. The model is validated for a 3-year period and run separately for 28 years using long-term daily atmospheric forcing data from a nearby meteorological station. Model simulations show exceptionally good agreement with observed surface and bottom water temperatures during the 3-year period. Similarly, simulated surface water temperatures for 28 years show remarkably good agreement with long-term in situ water temperatures.
High salmon density and low discharge create periodic hypoxia in coastal rivers
2017 - Christopher J. Sergeant, J. Ryan Bellmore, Casey McConnell, Jonathan W. Moore
Dissolved oxygen (DO) is essential to the survival of almost all aquatic organisms. Here, we examine the possibility that abundant Pacific salmon (Oncorhynchus spp.) and low streamflow combine to create hypoxic events in coastal rivers. Using high-frequency DO time series from two similar watersheds in southeastern Alaska, we summarize DO regimes and the frequency of hypoxia in relationship to salmon density and stream discharge. We also employ a simulation model that links salmon oxygen respiration to DO dynamics and predicts combinations of salmon abundance, discharge, and water temperature that may result in hypoxia. In the Indian River, where DO was monitored hourly during the ice-free season from 2010 to 2015, DO levels decreased when salmon were present. In 2013, a year with extremely high spawning salmon densities, DO dropped to 1.7 mg/L and 16% saturation, well below lethal limits. In Sawmill Creek, where DO was monitored every six minutes across an upstream–downstream gradient during the 2015 spawning season, DO remained fully saturated upstream of spawning reaches, but declined markedly downstream to 2.9 mg/L and 26% saturation during spawning. Modeled DO dynamics in the Indian River closely tracked field observations. Model sensitivity analysis illustrates that low summertime river discharge is a precursor to salmon-induced oxygen depletion in our study systems. Our results provide compelling evidence that dense salmon populations and low discharge can trigger hypoxia, even in rivers with relatively cold thermal regimes. Although climate change modeling for southeastern Alaska predicts an increase in annual precipitation, snowfall in the winter and rainfall in the summer are likely to decrease, which would in turn decrease summertime discharge in rain- and snow-fed streams and potentially increase the frequency of hypoxia. Our model template can be adapted by resource managers and watershed stakeholders to create real-time predictive models of DO trends for individual streams. While preserving thermally suitable stream habitat for cold-water taxa facing climate change has become a land management priority, managers should also consider that some protected watersheds may still be at risk of increasingly frequent hypoxia due to human impacts such as water diversion and artificially abundant salmon populations caused by hatchery straying.
Dissolved oxygen (DO) is essential to the survival of almost all aquatic organisms. Here, we examine the possibility that abundant Pacific salmon (Oncorhynchus spp.) and low streamflow combine to create hypoxic events in coastal rivers. Using high-frequency DO time series from two similar watersheds in southeastern Alaska, we summarize DO regimes and the frequency of hypoxia in relationship to salmon density and stream discharge. We also employ a simulation model that links salmon oxygen respiration to DO dynamics and predicts combinations of salmon abundance, discharge, and water temperature that may result in hypoxia. In the Indian River, where DO was monitored hourly during the ice-free season from 2010 to 2015, DO levels decreased when salmon were present. In 2013, a year with extremely high spawning salmon densities, DO dropped to 1.7 mg/L and 16% saturation, well below lethal limits. In Sawmill Creek, where DO was monitored every six minutes across an upstream–downstream gradient during the 2015 spawning season, DO remained fully saturated upstream of spawning reaches, but declined markedly downstream to 2.9 mg/L and 26% saturation during spawning. Modeled DO dynamics in the Indian River closely tracked field observations. Model sensitivity analysis illustrates that low summertime river discharge is a precursor to salmon-induced oxygen depletion in our study systems. Our results provide compelling evidence that dense salmon populations and low discharge can trigger hypoxia, even in rivers with relatively cold thermal regimes. Although climate change modeling for southeastern Alaska predicts an increase in annual precipitation, snowfall in the winter and rainfall in the summer are likely to decrease, which would in turn decrease summertime discharge in rain- and snow-fed streams and potentially increase the frequency of hypoxia. Our model template can be adapted by resource managers and watershed stakeholders to create real-time predictive models of DO trends for individual streams. While preserving thermally suitable stream habitat for cold-water taxa facing climate change has become a land management priority, managers should also consider that some protected watersheds may still be at risk of increasingly frequent hypoxia due to human impacts such as water diversion and artificially abundant salmon populations caused by hatchery straying.
Redox Dynamics and Oxygen Reduction Rates of Infiltrating Urban Stormwater beneath Low Impact Development (LID)
2016 - Mays N. Danfoura and Jason J. Gurdak
Low impact development (LID) best management practices (BMPs) collect, infiltrate, and treat stormwater runoff, and increase recharge to aquifers. Understanding the controls on reduction/oxidation (redox) conditions within LID BMPs is important for groundwater management because outflow from some LID BMPs can recharge aquifers and affect groundwater quality. Here we evaluate redox conditions of urban stormwater runoff in a LID infiltration trench in San Francisco, California, and quantify the relation between water saturation (%) and temperature (°C) and resulting dissolved oxygen (DO) concentrations, redox dynamics, and O2 reduction rates. The DO fluctuations have an inverse response to the duration of saturation of the trench. Anoxic (<0.5 mg/L) conditions often occurred within hours of stormwater events and persisted from a few hours to two days, which indicate that microbial respiration can be a limiting factor for DO. Temperature of stormwater runoff was not a statistically significant control on DO. The estimated O2 reduction rate is 0.003 mg·L‒1·min‒1, which is two to five orders of magnitude higher than in groundwater from previous studies. Higher rates of O2 reduction are a function of the more oxic and organic-rich stormwater runoff that drives faster microbial O2 reduction. Our findings have important implications for the design of infiltration trenches and other LID BMPs to achieve desired redox conditions for infiltrating stormwater toward minimizing groundwater contamination.
Low impact development (LID) best management practices (BMPs) collect, infiltrate, and treat stormwater runoff, and increase recharge to aquifers. Understanding the controls on reduction/oxidation (redox) conditions within LID BMPs is important for groundwater management because outflow from some LID BMPs can recharge aquifers and affect groundwater quality. Here we evaluate redox conditions of urban stormwater runoff in a LID infiltration trench in San Francisco, California, and quantify the relation between water saturation (%) and temperature (°C) and resulting dissolved oxygen (DO) concentrations, redox dynamics, and O2 reduction rates. The DO fluctuations have an inverse response to the duration of saturation of the trench. Anoxic (<0.5 mg/L) conditions often occurred within hours of stormwater events and persisted from a few hours to two days, which indicate that microbial respiration can be a limiting factor for DO. Temperature of stormwater runoff was not a statistically significant control on DO. The estimated O2 reduction rate is 0.003 mg·L‒1·min‒1, which is two to five orders of magnitude higher than in groundwater from previous studies. Higher rates of O2 reduction are a function of the more oxic and organic-rich stormwater runoff that drives faster microbial O2 reduction. Our findings have important implications for the design of infiltration trenches and other LID BMPs to achieve desired redox conditions for infiltrating stormwater toward minimizing groundwater contamination.
