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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.


Influence of macrophytes on stratification and dissolved oxygen dynamics in ponds
2022 - Albright, E. A., Ladwig, R., & Wilkinson, G. M.

Small waterbodies are sensitive to stressors such as nutrient enrichment and heatwaves. However, when present, macrophytes may mediate these compounding stressors through their influence on water column thermal structure. Canopy-forming macrophyte beds can induce thermal stratification, which may limit the depth and degree of water column warming during heatwaves. We leveraged an ecosystem experiment and hydrodynamic model to evaluate how macrophyte biomass, thermal structure, and dissolved oxygen (DO) responded to the interaction of episodic nutrient loading and periods of high temperatures in two shallow, temperate ponds (mean depth 0.8 m, maximum depth 2 m). We added nutrients to one pond, simulating storm-driven loading, while the other pond served as an unmanipulated reference. Following the first nutrient addition both ponds experienced a 5-day period of high surface water temperatures. Submersed macrophytes in the nutrient addition pond began to senesce mid-summer, likely a result of phytoplankton shading from the nutrient addition and heat stress, while macrophytes in the reference pond followed expected seasonal patterns, senescing in early autumn. We found that macrophytes structured the thermal environment in the ponds through vertical attenuation of turbulent kinetic energy and light. Macrophytes reduced the vertical extent of water column warming during the sustained heat event by 0.25-0.5 m and maintained cooler bottom temperatures (up to 2.5 °C cooler) throughout the summer, suggesting that macrophytes may buffer small waterbodies from heatwaves. Seasonal patterns in DO saturation also followed trends in macrophyte biomass; however, during the heat event, DO saturation fell sharply (declined by 22.4 to 50.4%) in both ponds and remained depressed through the remainder of the summer. Synthesis: Our findings reveal that canopy-forming aquatic plant beds can buffer ponds from brief aquatic heat events but also that the plants themselves are sensitive to nutrient loading and temperature extremes. These results contribute to our mechanistic understanding of the effects of compound, extreme events in small waterbodies and the role aquatic plants can play in mediating these stressors. This understanding is necessary for adaptive management of small waterbodies such that these systems will continue to support freshwater biodiversity.
Macrophyte-hydrodynamic interactions mediate stratification and dissolved oxygen 2 dynamics in ponds
Albright, E. A., Ladwig, R., & Wilkinson, G. M.

Small waterbodies are sensitive to stressors such as eutrophication and heatwaves; 25 however, interactions between macrophytes and hydrodynamics may mediate the effects of 26 compounding stressors. Leveraging an ecosystem experiment and hydrodynamic model, we 27 evaluated how macrophyte biomass, thermal structure, and dissolved oxygen (DO) responded to 28 the interaction of episodic nutrient loading and periods of high temperatures in two temperate 29 ponds. In one pond we experimentally added pulses of nutrients, simulating storm-driven loading 30 (the other pond served as an unmanipulated reference). Following the first nutrient pulse both 31 ponds experienced a 5-day period of high surface water temperatures. Macrophytes in the 32 nutrient addition pond began to senescence mid-summer due to phytoplankton shading from the 33 nutrient addition and heat stress while macrophytes in the reference pond followed expected 34 seasonal patterns, senescing in early autumn. Field observations and model results indicate that 35 macrophytes structured the thermal environment through vertical attenuation of turbulent kinetic 36 energy and light. Macrophytes reduced the vertical extent of water column warming during the 37 heat event by 0.25-0.5 m and maintained cooler bottom temperatures (up to 2.5 °C cooler) 38 throughout the summer, suggesting that macrophytes may buffer small waterbodies from 39 heatwaves. Seasonal patterns in DO saturation also followed trends in macrophyte biomass; 40 however, during the heat event, DO saturation fell sharply (-22.4 to 50.4 %) in both ponds and 41 remained depressed through the remainder of the summer. This experiment and modeling 42 exercise demonstrated that macrophyte influence on turbulent flows and light are pivotal in 43 mediating how small waterbodies respond to compounding stressors.


Positive Community Interactions of Artificial Eastern Oyster Reefs (Crassostrea virginica) on Cotransplanted Eelgrass (Zostera marina) Growth and Survival
2023 - DeLany, Flynn

Seagrass and oyster habitats are two key habitat-forming species that contribute significantly to coastal system function and resilience. However, seagrass populations have been disappearing at accelerating rates over recent decades, and global restoration efforts have had low rates of transplant establishment in target areas. Implementation of known facilitations between eelgrasses, oysters, and their communities may result in increased yields for traditional restoration methodologies. We focused on the co-planting of eelgrass with artificial eastern oyster reefs to explore the impact of documented facilitations on eelgrass transplants from oyster communities and their associated community assemblages.
Prevalence of Autotrophy in Non-humic African Lakes
2022 - Cédric Morana, Alberto V. Borges, Loris Deirmendjian, William Okello, Hugo Sarmento, Jean-Pierre Descy, Ismael A. Kimirei & Steven Bouillon

Heterotrophic respiration of organic matter (OM) is thought to dominate over aquatic primary production (PP) in most freshwater lake ecosystems. This paradigm implies that lateral transport of OM from the terrestrial biosphere subsidize the major fraction of aquatic respiration and that many lakes are a net source of carbon dioxide (CO2) to atmosphere. Nevertheless, African lakes were absent of the datasets upon which this paradigm was built. Here, we report a comprehensive and methodologically consistent data set of pelagic PP and community respiration (CR) obtained over the last decade in contrasting non-humic African lakes including 5 of the East African Great lakes (Tanganyika, Kivu, Edward, Albert, Victoria) and smaller shallow lakes located in Eastern Africa.
Morphological and genetic mechanisms underlying the plasticity of the coral Porites astreoides across depths in Bermuda
2022 - Federica Scucchia, Kevin Wong, Paul Zaslansky, Hollie M. Putnam, Gretchen Goodbody-Gringley, Tali Mass

The widespread decline of shallow-water coral reefs has fueled interest in assessing whether mesophotic reefs can act as refugia replenishing deteriorated shallower reefs through larval exchange. Here we explore the morphological and molecular basis facilitating survival of planulae and adults of the coral Porites astreoides (Lamarck, 1816; Hexacorallia: Poritidae) along the vertical depth gradient in Bermuda. We found differences in micro-skeletal features such as bigger calyxes and coarser surface of the skeletal spines in shallow corals. Yet, tomographic reconstructions reveal an analogous mineral distribution between shallow and mesophotic adults, pointing to similar skeleton growth dynamics.
The Role of Abiotic and Biotic Processes in Regulating Benthic Ecosystem Function Along a Productivity Gradient
2022 - Framsted, Nicholas

"The benthic zone of lakes can be a hotspot for lake energy flows and nutrient cycling. Indeed, the notion of benthic “ooze” and its role in the recycling of nutrients forms a conceptual cornerstone of ecology (Lindeman 1942). Benthic habitats can vary from soft, muddy sediments rich in organic matter and nutrients to bare rock covered by thin biofilms. These habitats form the linkage between lake and watershed, and support a range of ecosystem processes—from exchange of groundwater nutrients, internal nutrient cycling, mineralization of organic matter, heterotrophic respiration, and benthic algal production—that each vary in importance between different waterbodies. Clear Lake, CA, and Lake Tahoe represent two systems that span a gradient in trophic level, depth, and underlying geology. "
Plasticity of Porites astreoides Early Life History Stages Suggests Mesophotic Coral Ecosystems Act as Refugia in Bermuda
2021 - Gretchen Goodbody-Gringley, Federica Scucchia, Rebecca Ju, Alex Chequer, Shai Einbinder, Stephane Martinez, Hagai Nativ, Tali Mass

As the devastating impacts of global climate change and local anthropogenic stressors on shallow-water coral reefs are expected to rise, mesophotic coral ecosystems have increasingly been regarded as potential lifeboats for coral survival, providing a source of propagules to replenish shallower reefs. Yet, there is still limited knowledge of the capacity for coral larvae to adjust to light intensities that change with depth. This study elucidates the mechanisms underlying plasticity during early life stages of the coral Porites astreoides that enable survival across broad depth gradients.
Always ready? Primary production of Arctic phytoplankton at the end of the polar night
2021 - Clara J. M. Hoppe

The end of the polar night with the concurrent onset of photosynthetic biomass production ultimately leads to the spring bloom, which represents the most important event of primary production for the Arctic marine ecosystem. This dataset shows, for the first time, significant in situ biomass accumulation during the dark–light transition in the high Arctic, as well as the earliest recorded positive net primary production rates together with constant chlorophyll a-normalized potential for primary production through winter and spring. The results indicate a high physiological capacity to perform photosynthesis upon re-illumination, which is in the same range as that observed during the spring bloom. 
Vertical Habitat Gradients: Comparing Phytoplankton Dynamics in Lakes with Low to Moderate Dissolved Organic Carbon Concentration
2021 - Matthew J. Farragher

Concentrations of dissolved organic carbon (DOC) increased across lakes of Maine for several decades before stabilizing or decreasing in recent years. To investigate the seasonal effects of DOC on phytoplankton habitat structure, I assessed vertical gradients of temperature, oxygen, light, and chlorophyll in four lakes in Acadia National Park from under ice through fall turnover in 2020. Lake DOC concentrations ranged from low (~2 mg L-1) to moderate (~4 mg L-1). Low-DOC lakes were clearer, with greater mean Secchi depths (9-15 m) than moderateDOC lakes (5-6 m). Moderate-DOC lakes experienced hypolimnetic anoxia in the summer and had more variable concentrations and vertical gradients of chlorophyll a.
Under Ice and Early Summer Phytoplankton Dynamics in Two Arctic Lakes with Differing DOC
2021 - V. Hazuková, B. T. Burpee, I. McFarlane-Wilson, J. E. Saros

We investigated Arctic lake phytoplankton response along vertical gradients in the water column during seasonal succession from ice-covered to open-water conditions. Two oligotrophic lakes in West Greenland with different dissolved organic carbon (DOC) concentrations were selected. We assessed which factors: (1) promote under-ice growth of phytoplankton, and (2) trigger shifts in the community structure. Our results suggest that DOC is an important driver of the seasonal distribution of phytoplankton biomass—high DOC exacerbates light limitation under ice resulting in low phytoplankton biomass, but supports phytoplankton growth during the open-water period when photolytic and biological degradation of organic matter contributes to the pool of available nutrients.
Drivers of Biogeochemical Variability in a Central California Kelp Forest: Implications for Local Amelioration of Ocean Acidification
2020 - Heidi K. Hirsh, Kerry J. Nickols, Yuichiro Takeshita, Sarah B. Traiger, David A. Mucciarone, Stephen Monismith, Robert B. Dunbar

Kelp forests are among the world's most productive marine ecosystems, and they have the potential to locally ameliorate ocean acidification (OA). In order to understand the contribution of kelp metabolism to local biogeochemistry, we must first quantify the natural variability and the relative contributions of physical and biological drivers to biogeochemical changes in space and time. We deployed an extensive instrument array in Monterey Bay, CA, inside and outside of a kelp forest to assess the degree to which giant kelp (Macrocystis pyrifera) locally ameliorates present-day acidic conditions which we expect to be exacerbated by OA.
Calcification and organic productivity at the world's southernmost coral reef
2020 - Kay L. Davis, Ashly McMahon, Rogger E. Correa, Isaac R. Santos

Estimates of coral reef calcification and organic productivity provide valuable insight to community functionality and the response of an ecosystem to stress events. High-latitude coral reefs are expected to experience rapid changes in calcification rates and become refugia for tropical species following climate change and increasing bleaching events. Here, we estimate ecosystem-scale calcification and organic productivity at the world's southernmost coral reef using seawater carbon chemistry observations (Lord Howe Island, Australia). We reduce uncertainties in metabolic calculations by producing a detailed bathymetric model and deploying two current meters to refine residence time and volume estimates.


Viral contamination in shellfish growing areas during normal harvesting periods and following wastewater overflows in an urban estuary with complex hydrography
2024 - Campos Carlos Joanne Hewitt Pradip Gyawali

Knowledge of the dispersive characteristics and time of travel of microbiological contamination is a key consideration in determining impacts on shellfish growing areas following wastewater overflows. In this study, norovirus genogroup I and II, indicators of viral contamination (F-RNA bacteriophage genogroup II (F-RNA GII), crAssphage, pepper mild mottle virus) and Escherichia coli were monitored during periods of normal harvesting and following overflows in two commercial shellfish growing areas in Otago Harbour (Aotearoa New Zealand).
Study of Shellfish Growing Area During Normal Harvesting Periods and Following Wastewater Overflows in an Urban Estuary With Complex Hydrography
2024 - Carlos J. A. Campos, Pradip Gyawali & Joanne Hewitt

Viral testing combined with hydrographic studies is considered standard good practice in determining microbiological impacts on shellfish growing areas following wastewater overflows. In this study, norovirus genogroup I and II, indicators of viral contamination (F-RNA bacteriophage genogroup II (F-RNA GII), crAssphage, pepper mild mottle virus) and Escherichia coli were monitored during periods of normal harvesting and following overflows in two commercial shellfish growing areas in Otago Harbour (Aotearoa New Zealand).
Dinophysis acuminata or Dinophysis acuta: What Makes the Difference in Highly Stratified Fjords?
2023 - Ángela M. Baldrich, Patricio A. Díaz, Gonzalo Álvarez, Iván Pérez-Santos, Camila Schwerter, Manuel Díaz, Michael Araya, María Gabriela Nieves,Camilo Rodríguez-Villegas, Facundo Barrera, Concepción Fernández-Pena, Sara Arenas-Uribe, Pilar Navarro, Beatriz Reguera

Dinophysis acuminata and D. acuta, which follows it seasonally, are the main producers of lipophilic toxins in temperate coastal waters, including Southern Chile. Strains of the two species differ in their toxin profiles and impacts on shellfish resources. D. acuta is considered the major cause of diarrhetic shellfish poisoning (DSP) outbreaks in Southern Chile, but there is uncertainty about the toxicity of D. acuminata, and little information on microscale oceanographic conditions promoting their blooms.
An advanced towed CTD chain for physical-biological high resolution in situ upper ocean measurements
2023 - Thomas Kock, Burkard Baschek, Florian Wobbe, Martina Heineke, Rolf Riethmueller, Stephan C. Deschner, Gerd Seidel, Paulo H. R. Calil

Submesoscale eddies, fronts, and filaments are ubiquitous in the upper ocean and play an important role in biogeochemical and mixing processes as well as in the energy budget. To capture the high spatial variability of submesoscale processes, it is desirable to simultaneously resolve the vertical and horizontal gradients of hydrographic properties on scales of 10 m to 10 km. We present a revised towed CTD chain, for rapid quasi-synoptic in situ measurements of submesoscale oceanographic features, that is lighter, more robust and scientifically more useful than previous towed CTD chains.
Monitoring multiple parameters in complex water scenarios using a low-cost open-source data acquisition platform
2023 - Steven Martinez Vargas, Alejandro J. Vitale, Sibila A. Genchi, Simón F. Nogueira, Andrés H. Arias, Gerardo M.E. Perillo, Agustín Siben, Claudio A. Delrieux

Water monitoring faces challenges that are driven by the infrastructure, protection, financial resources, science and innovation policies, among others. A modular, low-cost, fully open-source and small-sized Unmanned Surface Vessel (USV) called EMAC-USV (EMAC: Estación de Monitoreo Ambiental Costero), is proposed for monitoring bathymetry and water quality parameters (i.e. temperature, suspended solids concentration and hydrocarbon concentration) in complex water scenarios. A detailed description of each part of the platform as well as all electronic connections and functioning is presented.


Carbon Biogeochemistry and Export Governed by Flow in a Non-Perennial Stream
2023 - Kristen A. Bretz, Natalie N. Murphy, Erin R. Hotchkiss

Non-perennial headwaters experience extremes in flow conditions that likely influence carbon fate. As surface waters contract through dry periods, reconnect during storms, and re-expand or dry again, there is a great deal of variability in carbon emissions and export. We measured discharge, dissolved oxygen, carbon dioxide (CO2), and dissolved organic carbon (DOC) continuously in a persistent pool at the base of a non-perennial, forested headwater stream in the southeastern United States to characterize how flow changes affect carbon emissions and export as the stream expands and shrinks. We also compared carbon concentrations and export during different stream flow categories before and after fall wet-up.
Unexpected functional diversity of stream biofilms within and across proglacial floodplains despite close spatial proximity
2023 - Grégoire Michoud, Tyler J. Kohler, Hannes Peter, Jade Brandani, Susheel Banu Busi, Tom J. Battin

High-mountain streams are particularly vulnerable to climate change because they intimately interface with the cryosphere. As glaciers shrink and snowpack diminishes, proglacial streams will eventually shift from being glacier-fed to streams fed by groundwater, snowmelt and precipitation. This shift will affect both the flow regime and physico-chemical characteristics of streams, possibly also the structure and function of their benthic microbiome. Here, we applied genome-resolved metagenomics to benthic biofilms from glacier-fed streams and their groundwater-fed tributaries within three proglacial floodplains in the Swiss Alps.
Homogeneous Environmental Selection Structures the Bacterial Communities of Benthic Biofilms in Proglacial Floodplain Streams
2023 - Jade Brandani, Hannes Peter, Stilianos Fodelianakis, Tyler J. Kohler, Massimo Bourquin, Grégoire Michoud, Susheel Bhanu Busi, Leila Ezzat, Stuart Lane, Tom J. Battin

In proglacial floodplains, glacier recession promotes biogeochemical and ecological gradients across relatively small spatial scales. The resulting environmental heterogeneity induces remarkable microbial biodiversity among proglacial stream biofilms. Yet the relative importance of environmental constraints in forming biofilm communities remains largely unknown. Extreme environmental conditions in proglacial streams may lead to the homogenizing selection of biofilm-forming microorganisms. However, environmental differences between proglacial streams may impose different selective forces, resulting in nested, spatially structured assembly processes.
Analysis of the Simulation of the Hydraulics of a Sacramento-San Joaquin Delta Marsh with a Mesocosm
2022 - Rupali Ashok Sigi

The Sacramento – San Joaquin Delta has been facing the major issue of land subsidence within the last century. This has created a high risk of failure of existing levees that have been protecting the area from flooding. Land subsidence below sea level is also creating the risk of salinity intrusion into the freshwater system of the Delta. Wetlands in the Delta help reduce oxidation of the land and compaction of the peats, which assist with reversal of land subsidence. These wetlands need to be re-established and maintained in the Delta.
A Holistic Approach to Study Groundwater-Surface Water Modifications Induced by Strong Earthquakes: The Case of Campiano Catchment (Central Italy)
2022 - Elisa Mammoliti, Davide Fronzi, Costanza Cambi, Francesco Mirabella, Carlo Cardellini, Emiliano Patacchiola, Alberto Tazioli, Stefano Caliro and Daniela Valigi

Carbonate aquifers are characterised by strong heterogeneities and their modelling is often a challenging aspect in hydrological studies. Understanding carbonate aquifers can be more complicated in the case of strong seismic events which have been widely demonstrated to influence groundwater flow over wide areas or on a local scale. The 2016–2017 seismic sequence of Central Italy is a paradigmatic example of how earthquakes play an important role in groundwater and surface water modifications. The Campiano catchment, which experienced significant discharge modifications immediately after the mainshocks of the 2016–2017 seismic sequence (Mmax = 6.5) has been analysed in this study.
The use of Rhodamine WT for the characterization of hydraulic residence times in wetlands
2020 - Rachael Dal Porto

Objectives: 1. Determince hyrdraulic residence time and related parameters in Delta wetlands using Rhodamine WT releases; 2. Analyze Rhodamine WT sorption to wetland peat in batch, mesocosm and field experiments; and 3. Determine how Rhodamine WT tracer dye sorption affects the calculation of residence time and other parameters.
Comparison between Periodic Tracer Tests and Time-Series Analysis to Assess Mid- and Long-Term Recharge Model Changes Due to Multiple Strong Seismic Events in Carbonate Aquifers
2020 - Davide Fronzi, Diego Di Curzio, Sergio Rusi, Daniela Valigi and Alberto Tazioli

Understanding the groundwater flow in carbonate aquifers represents a challenging aspect in hydrogeology, especially when they have been struck by strong seismic events. It has been proved that large earthquakes change springs hydrodynamic behaviour showing transitory or long-lasting variations and making their management much more difficult. This is the case of Sibillini Massif (central Italy), which has been hit by the well-known 2016–2017 seismic period. This work aims to improve the knowledge of carbonate aquifers groundwater circulation and their possible changes in the hydrodynamic behaviour, during and after a series of strong seismic events.
E-DATA: A Comprehensive Field Campaign to Investigate Evaporation Enhanced by Advection in the Hyper-Arid Altiplano
2020 - Francisco Suárez, Felipe Lobos, Alberto de la Fuente, Jordi Vilà-Guerau de Arellano, Ana Prieto, Carolina Meruane and Oscar Hartogensis

In the endorheic basins of the Altiplano, water is crucial for sustaining unique ecological habitats. Here, the wetlands act as highly localized evaporative environments, and little is known about the processes that control evaporation. Understanding evaporation in the Altiplano is challenging because these environments are immersed in a complex topography surrounded by desert and are affected by atmospheric circulations at various spatial scales. Also, these environments may be subject to evaporation enhancement events as the result of dry air advection. To better characterize evaporation processes in the Altiplano, the novel Evaporation caused by Dry Air Transport over the Atacama Desert (E-DATA) field campaign was designed and tested at the Salar del Huasco, Chile.
Interpretation of Dye Tracing Data Collected November 13–December 2, 2017, at the Savoy Experimental Watershed as part of the Advanced Groundwater Field Techniques in Karst Terrains Course, Savoy, Arkansas
2019 - Eve L. Kuniansky, Joshua M. Blackstock, Daniel M. Wagner, and J. Van Brahana

The first course on the use of advanced groundwater field techniques for karst aquifers was conducted November 13–17, 2017, at the University of Arkansas Savoy Experimental Watershed (SEW), which is located on pastures for beef livestock research conducted by the Department of Animal Sciences at the University of Arkansas at Savoy, Arkansas. The SEW is an interdisciplinary, collaborative, long-term research site for the study of animal-waste management in a mantled karst setting. The course focused on advanced field activities appropriate for karst aquifer studies: dye tracing, groundwater/surface-water interactions, geophysical methods, and geochemistry.
A Retrospective Analysis of a Constructed Stormwater Wetlands
2017 - Molina, Stephanie Mary

Sustainable stormwater management is prevalent today as many seek greener solutions for runoff collection and treatment. In most cases they are implemented as means to manage rainwater before it enters sewer systems via stormwater control measures (SCM). In other cases, SCMs are implemented to regulate nutrient and metal loads transported by stormwater runoff that flow and collect in rivers and streams. At Villanova University a Constructed Stormwater W etlands (CSW) was designed to reduce nutrient concentration and attenuate flow entering the headwaters of Mill Creek, a tributary of Schuylkill River.


Modelling prolonged stratification and hypoxia in dryland river waterholes during drought conditions
2023 - Peisheng Huang, Jonathan C. Marshall, Jaye Lobegeiger, Rebecca L. Cramp, Monique A. Parisi, Craig E. Franklin, Andrea Prior, Kamilla Kurucz & Matthew R. Hipsey

Dryland river waterholes provide critical habitat and serve as refugia for aquatic animals during droughts, but the quality of these waterholes can often be severely compromised by hypoxic conditions that can lead to mass fish kills and loss of biodiversity. To assist river management, we developed a waterhole-scale ecohydrology model representing thermal stratification and dissolved oxygen regimes during prolonged drought periods in northern Murray-Darling Basin dryland rivers in Queensland, Australia. Model development focused around 6 typical waterholes in these rivers that were shallow (<5 m deep), highly turbid, and stratified with low dissolved oxygen.
Phosphorus and Oxygen Dynamics between Fall and Spring Turnover Events in a Small Canadian Shield Lake
2022 - Ghane, Alireza

"In dimictic lakes, the stable density stratification during summer and winter inhibits vertical mixing of nutrients and oxygen. This favors the development of hypolimnetic hypoxia, which degrades cool-water fish habitat and enhances nutrient mineralization and diffusion from the sediments. Fall turnover began once the entire water column become nearly isothermal (within 0.4 °C) at the deepest point of the lake and continued to the onset of winter stratification. Similarly, spring turnover began when the water column became nearly isothermal (within 0.4 °C) and continued until the average water column temperature reached 4.0 to 4.5 °C. "
On biogenic turbulence production and mixing from vertically migrating zooplankton in lakes
2018 - Stefano Simoncelli, Stephen J. Thackeray & Danielle J. Wain

Vertical mixing in lakes is a key driver of transport of ecologically important dissolved constituents, such as oxygen and nutrients. In this study we focus our attention on biomixing, which refers to the contribution of living organisms towards the turbulence and mixing of oceans and lakes. While several studies of biomixing in the ocean have been conducted, no in situ studies exist that assess the turbulence induced by freshwater zooplanktonic organisms under real environmental conditions. Here, turbulence is sampled during three different sampling days during the sunset diel vertical migration of Daphnia spp. in a small man-made lake.
Sensor-based quality control of raw water
2018 - "Esmeralda Frihammar, Madeleine Gobl, Jennifer Jonsson, Ylva Kjellgren, Alexi Lampinen, Lina Oskarssonoch, Mathias Wallin "

This report was carried out on behalf of the company Norrvatten, which operates the Görvälnverket water plant in Jakobsberg outside Stockholm. The study is divided into three main objectives. The first goal involves performing an analysis of existing measurement data from a sensor located inside the water plant. Data from the plant was compared with weather data to bring out possible connections. Information about connections could lead to Norrvatten being able to use its measuring equipment more efficiently. MatLab was used in the analysis and certain relationships between TOC (Total Organic Carbon), precipitation and water levels could be seen and clear seasonal trends could also be discerned.
Internal wave-driven transport of fluid away from the boundary of a lake
2013 - Danielle J. Wain, Michael S. Kohn, Joshua A. Scanlon, Chris R. Rehmann

A field experiment was conducted to study transport of fluid from the boundary to the interior of a lake. Tracking of a tracer injected into the metalimnion was combined with measurements of meteorological forcing, internal waves, and temperature microstructure. Seiches of vertical mode 2 and horizontal modes 1 and 2 were initiated after a wind event, and the tracer moved 950 m into the interior after 29.2 h. Four potential mechanisms for spreading of the tracer from the boundary to the interior were considered: intrusions from boundary mixing, horizontal dispersion, advection by seiches, and advection and dispersion driven by internal waves.