Life Sciences Commons^™

Fecal Pellet Production By North Atlantic Zooplankton, Michael Gibson

Undergraduate Honors Theses

Fecal pellet carbon (FPC) production by zooplankton is a significant component of the ocean’s biological carbon pump: the suite of biological processes that mediate export of carbon to the deep ocean, ultimately leading to the sequestration of atmospheric carbon dioxide in the ocean. In this study, mesozooplankton (zooplankton 0.2 mm to ~2 cm) were collected from the epipelagic zone in the temperate North Atlantic Ocean during day and night in May 2021. Zooplankton were live separated into five size fractions and incubated on board ship in natural surface seawater to measure fecal pellet production rate of the mixed mesozooplankton community. …

Impacts And Uncertainties Of Climate Change On The Chesapeake Bay, Kyle E. Hinson

Dissertations, Theses, and Masters Projects

Climate change impacts in the Chesapeake Bay will limit the efficacy of nutrient reduction efforts and decrease dissolved oxygen, but uncertainties associated with the magnitude of these effects remain. An understanding of underlying mechanisms that have driven recent warming trends will narrow uncertainties for future pathways of temperature change. Additionally, future simulations of climate impacts in the estuary are dependent on multiple different sources of uncertainty, many of which have not yet been fully evaluated. This dissertation used a three- dimensional coupled hydrodynamic-biogeochemical model to investigate recent warming trends as well as underlying uncertainties likely to influence regional projections of …

The Role Of Zooplankton Community Composition In Fecal Pellet Carbon Production In The York River Estuary, Chesapeake Bay, Kristen Nicole Sharpe

Dissertations, Theses, and Masters Projects

The biological pump is a critical component of carbon transformation in aquatic ecosystems, but the role that zooplankton play in carbon production and vertical export is rarely studied in estuaries. Zooplankton produce carbon-rich fecal pellets which sink to depth and can fuel benthic community metabolism. The body size and taxonomic structure of the zooplankton community varies on interannual, seasonal, and diel time scales, and can lead to varying carbon production and export rates. We quantified fecal pellet carbon (FPC) production by the whole mesozooplankton community (> 200 µm) in the York River, a sub-estuary of Chesapeake Bay. Biomass and taxonomic …

Diel, Seasonal, And Interannual Changes In Coastal Antarctic Zooplankton Community Composition And Trophic Ecology, John A. Conroy

Dissertations, Theses, and Masters Projects

Throughout the ocean, zooplankton transfer energy from primary producers to higher predators and transport carbon from surface waters to depth. The efficiency of these processes depends in part upon the taxonomic composition and trophic ecology of the zooplankton community. Zooplankton species abundance and distribution shifted over recent decades along the West Antarctic Peninsula during a period of rapid regional warming and sea-ice decline. Although conducted within the context of long-term change, this dissertation research focuses on zooplankton dynamics at finer temporal scales that have received less attention. I analyzed depth-stratified net samples to investigate zooplankton diel vertical migration during Antarctic …

Estuarine Microbiomes And Biogeochemistry: Impacts Of Spatiotemporal Variation, Algal Blooms, And Microplastics, Samantha Grace Fortin

Dissertations, Theses, and Masters Projects

Estuaries are biogeochemical hotspots connecting terrestrial and coastal ecosystems. Anthropogenic disturbances, including increased nitrogen loading and plastic pollution, may have significant impacts on estuarine carbon and nitrogen cycling by altering microbiome structure and functions. The overarching goal of this dissertation was to examine how microbiomes and their associated biogeochemical processes are influenced by natural variation and anthropogenic disturbances in the York River Estuary (YRE). In chapter 2, spatial and temporal variation in benthic microbiomes and the rates of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) were examined to determine biotic and abiotic drivers of nitrogen …

Improving Observation, Assessment, And Management Of Atlantic Coastal Sharks, Cassidy Dawn Peterson

Dissertations, Theses, and Masters Projects

Coastal sharks represent a group of stocks for which observation, assessment, and management are particularly challenging. Large distributional ranges, complex migratory behavior, low economic value, and relatively few observations in fishery independent surveys hinder relative abundance estimation. Assessing stock status of coastal sharks is encumbered by limited data availability, data quality, and knowledge of life history strategy. Further, coastal sharks are challenging to manage due to their slow intrinsic population growth rates, competing stakeholder interests, history of overexploitation, and in some cases, subjection to international exploitation. This dissertation aimed to improve the capacity to observe relative abundance of coastal sharks. …

Quantifying The Increased Resiliency Of Chesapeake Bay Hypoxia To Environmental Conditions: A Benefit Of Nutrient Reductions, Luke Thomas Frankel

Dissertations, Theses, and Masters Projects

Seasonal hypoxia is a characteristic feature of the Chesapeake Bay as a result of anthropogenic eutrophication from agriculture and urban development throughout the watershed. Although in recent years coordinated management efforts have successfully reduced the flux of nutrients into the Bay, the overall goal of sufficient oxygen concentrations below the pycnocline for living resources remains unfulfilled. This was particularly apparent in 2018 and 2019 when the volume of hypoxic water exceeded the long-term (35-year) average due to anomalously high riverine discharge. To quantify the impact of watershed nutrient reductions, conventional statistical methods were employed in concert with a 3-D numerical …

An Operational Overview Of The Export Processes In The Ocean From Remote Sensing (Exports) Northeast Pacific Field Deployment, David A. Siegel, Ivona Cetinic, (...), Deborah K. Steinberg, Et Al

VIMS Articles

The goal of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) field campaign is to develop a predictive understanding of the export, fate, and carbon cycle impacts of global ocean net primary production. To accomplish this goal, observations of export flux pathways, plankton community composition, food web processes, and optical, physical, and biogeochemical (BGC) properties are needed over a range of ecosystem states. Here we introduce the first EXPORTS field deployment to Ocean Station Papa in the Northeast Pacific Ocean during summer of 2018, providing context for other papers in this special collection. The experiment was conducted with …

Dealing With Many Species: Improving Methodology For Forming And Assessing Species Complexes, Kristen Omori

Dissertations, Theses, and Masters Projects

In the United States, the Magnuson-Stevens Reauthorization Act mandates that all federally fished species must have catch limits, which can be challenging for data-limited species. One approach is to assess and manage a group of species with similar life history characteristics, vulnerability to the fishery, and overlapping geographic distributions in a single management unit, or a complex (i.e., stock or species complex). Using the Gulf of Alaska (GOA) Other Rockfish complex as a case study, the main goals of this dissertation are five-fold: 1) review species complexes in the United States; 2) compare multivariate techniques for assigning species to complexes; …

Effects Of Seawater Exchange On Water Chemistry Among Coastal Lakes With Intermittent Connections To The Sea, A. Challen Hyman, Dana Bigham Stephens

VIMS Articles

Intermittently closed and open lakes and lagoons (ICOLLs) are a dynamic class of coastal waterbodies with the unique feature of intermittently connecting to the sea. Understanding the functioning and potential threats of these globally rare systems is important to their preservation and protection. Coastal dune lakes of northwest Florida are one example of an understudied group of ICOLLs which connect with the Gulf of Mexico for brief periods of time. Using a 17-year, monthly water chemistry dataset, we analyzed long-term patterns in water chemistry among 16 coastal dune lakes. Using salinity as a proxy for frequency of seawater inflows, principal …

Relative Impacts Of Global Changes And Regional Watershed Changes On The Inorganic Carbon Balance Of The Chesapeake Bay, Pierre St-Laurent, Marjorie A.M. Friedrichs, Raymond G. Najjar, Elizabeth Shadwick, Hanquin Tian, Yuanzhi Yao

VIMS Articles

The Chesapeake Bay is a large coastal-plain estuary that has experienced considerable anthropogenic changeover the past century. At the regional scale, land-use change has doubled the nutrient input from rivers and led to an increase in riverine carbon and alkalinity. The bay has also experienced global changes, including the rise of atmospheric temperature and CO2. Here we seek to understand the relative impact of these changes on the inorganic carbon balance of the bay between the early 1900s and the early 2000s. We use a linked land–estuarine–ocean modeling system that includes both inorganic and organic carbon and nitrogen cycling. Sensitivity …

Zooplankton Diel Vertical Migration During Antarctic Summer, John A. Conroy, Deborah K. Steinberg, Patrica S. Thibodeau, Oscar Schofield

VIMS Articles

Zooplankton diel vertical migration (DVM) during summer in the polar oceans is presumed to be dampened due to near continuous daylight. We analyzed zooplankton diel vertical distribution patterns in a wide range of taxa along the Western Antarctic Peninsula (WAP) to assess if DVM occurs, and if so, what environmental controls modulate DVM in the austral summer. Zooplankton were collected during January and February in paired day-night, depth-stratified tows through the mesopelagic zone along the WAP from 2009-2017, as well as in day and night epipelagic net tows from 1993-2017. The copepod Metridia gerlachei, salp Salpa thompsoni, pteropod …

Providential Tides: The Double Low Water Of Narragansett Bay, D. G. Bowers, J. M. Brubaker

VIMS Articles

We investigate a mechanism for producing double-lows and double-highs in the semi-diurnal tide by selective amplification of higher harmonics in a resonant gulf. A double low water is observed at Providence, RI, near the head of Narragansett Bay on days when there is a flattening of the low water tidal curve at Newport, at the mouth of the bay. The flattening is caused by an unusually large quarter-diurnal component to the tide at Newport. The quarter diurnal component has the right phase (a maximum close to the time of the minimum in the semi-diurnal tide) to produce a prolonged flattening …

Feeding Time: How Nutrients Drive Phytoplankton Growth, Brianna Stanley

Reports

Grades: 9-12 Subjects: Biology | Environmental Science | Oceanography

This lesson plan helps students make the connection between the amount of nutrients present in an ecosystem and the resulting growth of phytoplankton in our coastal waters. This lesson takes this concept a step deeper, by exploring how the proportions of nitrogen and phosphorus in the environment create the ideal conditions for phytoplankton growth. Students will explore the concept of limiting factors and will work on both their graphing skills and their ability to compare ratios.

Environmental Controls On Pteropod Ecology And Physiology Along The Western Antarctic Peninsula, Patricia Susan Thibodeau

Dissertations, Theses, and Masters Projects

Pteropods (pelagic snails) are ubiquitous zooplankton in the Southern Ocean and abundant along the Western Antarctic Peninsula (WAP), one of the most rapidly warming regions on the planet. They are important prey for higher trophic levels, grazers of phytoplankton, and contribute to particulate organic and inorganic carbon export. Pteropods are heralded as bioindicators of ecosystem health due to the vulnerability of their aragonitic shells under ocean acidification conditions, which could greatly affect their abundances in the future. Despite their importance within Antarctic food webs, few studies have analyzed the effects of climate change on pteropod physiology and biogeography in the …

The Importance Of Antarctic Krill In Biogeochemical Cycles, El Cavan, A Belcher, Sl Hill, S Kawaguchi, S Mccormack, B Meyer, S Nicol, K Schmidt, Deborah K. Steinberg, Ga Tarling, Pw Boyd

VIMS Articles

Antarctic krill (Euphausia superba) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguins – but they have another important role. With their large size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean’s largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval …

Impacts Of Sea Level Rise On Hypoxia In The Chesapeake Bay: A Model Intercomparison, Pierre St-Laurent, Marjorie A.M. Friedrichs, Ming Li, Wenfei Ni

Reports

Over recent years a number of studies have examined the effects of sea level rise (SLR) on hypoxia in Chesapeake Bay. However, variations in the methodology, the years considered, and the metrics reported made comparisons between these studies difficult. To clarify the effects of SLR on the Bay’s hypoxia, we present an intercomparison between four numerical models following a common methodology. The models share the riverine fluxes, baseline period (1991–1995), and consider the same three scenarios of SLR: an increase in sea level of 0.17m, 0.50m, and 1.00m (representative of years 2025, 2050 and 2100, respectively). SLR is the sole …

James River Water Quality Model Refinement And Scenario Simulations, Jian Shen, Qubin Qin

Reports

This project was part of the Virginia Department of Environmental Quality’s (DEQ) study to evaluate the protectiveness of chlorophyll criteria and consider potential criteria revisions, along with implications for the James River portion of the Chesapeake Bay TMDL.

Scientific Considerations For Acidification Monitoring In The Us Mid-Atlantic Region, Ka Goldsmith, S Lau, Et Al, Eh Shadwick, Et Al

VIMS Articles

Coastal and ocean acidification has the potential to cause significant environmental and societal impacts. Monitoring carbonate chemistry parameters over spatial and temporal scales is challenging, especially with limited resources. A lack of monitoring data can lead to a limited understanding of real-world conditions. Without such data, robust experimental and model design is challenging, and the identification and understanding of episodic acidification events is nearly impossible. We present considerations for resource managers, academia, and industry professionals who are currently developing acidification monitoring programs in the Mid-Atlantic region. We highlight the following considerations for deliberation: 1) leverage existing infrastructure to include multiple …

It’S About Time: A Synthesis Of Changing Phenology In The Gulf Of Maine Ecosystem, Md Staudinger, Ke Mills, Et Al, David S. Johnson, Et Al

VIMS Articles

The timing of recurring biological and seasonal environmental events is changing on a global scale relative to temperature and other climate drivers. This study considers the Gulf of Maine ecosystem, a region of high social and ecological importance in the Northwest Atlantic Ocean and synthesizes current knowledge of (a) key seasonal processes, patterns, and events; (b) direct evidence for shifts in timing; (c) implications of phenological responses for linked ecological-human systems; and (d) potential phenology-focused adaptation strategies and actions. Twenty studies demonstrated shifts in timing of regional marine organisms and seasonal environmental events. The most common response was earlier timing, …

Treading Water: Tools To Help Us Coastal Communities Plan For Sea Level Rise Impacts, E A. Smith, W Sweet, Molly Mitchell, R Domingues, C P. Weaver, M Baringer, G Goni, J Haines, Jon Derek Loftis, John D. Boon, David L. Malmquist

VIMS Articles

As communities grapple with rising seas and more frequent flooding events, they need improved projections of future rising and flooding over multiple time horizons, to assist in a multitude of planning efforts. There are currently a few different tools available that communities can use to plan, including the Sea Level Report Card and products generated by a United States. Federal interagency task force on sea level rise. These tools are a start, but it is recognized that they are not necessarily enough at present to provide communities with the type of information needed to support decisions that range from seasonal …

Alkalinity In Tidal Tributaries Of The Chesapeake Bay, R. G. Najjar, M. Herrmann, S. M. Cintrón Del Valle, Jaclyn R. Friedman, Marjorie A.M. Friedrichs, Et Al

VIMS Articles

Despite the important role of alkalinity in estuarine carbon cycling, the seasonal and decadal variability of alkalinity, particularly within multiple tidal tributaries of the same estuary, is poorly understood. Here we analyze more than 25,000 alkalinity measurements, mostly from the 1980s and 1990s,in the major tidal tributaries of the Chesapeake Bay, a large, coastal‐plain estuary of eastern North America.The long‐term means of alkalinity in tidal‐fresh waters vary by a factor of 6 among seven tidal tributaries,reflecting the alkalinity of nontidal rivers draining to these estuaries. At 25 stations, mostly in the Potomac River Estuary, wefind significant long‐term increasing trends that …

Ocean Change Within Shoreline Communities: From Biomechanics To Behaviour And Beyond, Brian Gaylord, Kristina M. Barclay, Brittany M. Jellison, Laura L. Jurgens, Aaron T. Ninokawa, Emily B. Rivest, Lindsey R. Leighton

VIMS Articles

Humans are changing the physical properties of Earth. In marine systems, elevated carbon dioxide concentrations are driving notable shifts in temperature and seawater chemistry. Here, we consider consequences of such perturbations for organism biomechanics and linkages amongst species within communities.In particular,we examine case examples of altered morphologies and material properties, disrupted consumer–prey behaviours, and the potential for modulated positive (i.e. facilitative) interactions amongst taxa, as incurred through increasing ocean acidity and rising temperatures. We focus on intertidal rocky shores of temperate seas as model systems, acknowledging the longstanding role of these communities in deciphering ecological principles. Our survey illustrates the …

Symbiotic Unicellular Cyanobacteria Fix Nitrogen In The Arctic Ocean, K. Harding, K. A. Turk-Kubo, Rachel E. Sipler, M. M. Mills, D. A. Bronk

VIMS Articles

Biological dinitrogen (N2) fixation is an important source of nitrogen (N) in low-latitude open oceans. The unusual N2-fixing unicellular cyanobacteria (UCYN-A)/haptophyte symbiosis has been found in an increasing number of unexpected environments, including northern waters of the Danish Straight and Bering and Chukchi Seas. We used nanoscale secondary ion mass spectrometry (nanoSIMS) to measure 15N2 uptake into UCYN-A/haptophyte symbiosis and found that UCYN-A strains identical to low-latitude strains are fixing N2 in the Bering and Chukchi Seas, at rates comparable to subtropical waters. These results show definitively that cyanobacterial N2 fixation is not constrained to subtropical waters, challenging paradigms and …

Assessing The Impact Of Land Use And Climate Change On Streamflow And Nutrient Delivery To The New River Estuary, Nc, Shanna Williamson

Dissertations, Theses, and Masters Projects

Freshwater inflow influences numerous physical, chemical, and biological characteristics of estuaries. The influx of freshwater to an estuary typically serves as an important source of allochthonous material from which primary producers derive their energy and transfer this energy to higher trophic levels. Any changes to freshwater flow subsequently impacts nutrient delivery and indirectly impacts organisms across multiple trophic levels. Anthropogenic changes to coastal land use and climate both act to threaten the integrity of estuarine systems by influencing freshwater inflow and dissolved nutrient input. Watershed loading models such as the Regional Nutrient Management (ReNuMa) model offer the ability to estimate …

Crab Larval Abundance And Settlement Patterns In A Changing Chesapeake Bay, Itchika Sivaipram

Dissertations, Theses, and Masters Projects

All estuarine crabs have two larval stages, the zoea and the megalopa. Zoeae are entirely planktonic, whereas megalopae begin as plankton before beginning to search for settlement substrates as late stage megalopae. At both stages, crab larvae are subject to environmental conditions of the estuary. With changing environmental conditions due to anthropogenic activities and climate change, an understanding of how these planktonic larvae respond to environmental conditions is necessary for understanding subsequent larval supply to benthic populations and implication for fisheries management and habitat restoration. For this dissertation, I: 1) analyzed long-term timeseries in the lower Chesapeake Bay for spatial …

Impacts Of Atmospheric Nitrogen Deposition And Coastal Nitrogen Fluxes On Chesapeake Bay Hypoxia, Fei Da

Dissertations, Theses, and Masters Projects

Although rivers are the primary source of dissolved inorganic nitrogen (DIN) inputs to the Chesapeake Bay, direct atmospheric DIN deposition and DIN fluxes from the continental shelf can also significantly impact Chesapeake Bay hypoxia. The relative role of these additional sources of DIN has not previously been thoroughly quantified. In this study, the three-dimensional Estuarine-Carbon-Biogeochemistry model embedded in the Regional Ocean Modeling System (ChesROMS-ECB) is used to examine the relative impact of these three DIN sources. Model simulations highlight that DIN inputs from the atmosphere have roughly the same impact on hypoxia as the same gram for gram change in …

Consumption Patterns Of Chesapeake Bay Fishes, Christopher James Sweetman

Dissertations, Theses, and Masters Projects

As fisheries management moves away from single-species approaches and towards more holistic, ecosystem-based approaches, physiological and ecological interactions need to be explicitly considered and mechanistically understood. Accurate portrayals of food web interactions and the direction and magnitude of energy flow between predator and prey populations are fundamental components to further develop ecosystem-based fisheries management (EBFM). to bolster information that is required within an EBFM framework in the Chesapeake Bay, I conducted research designed to advance traditional dietary studies and better understand the form and structure within the Bay's food web. This research relied on controlled feeding experiments, comprehensive sampling of …

Improving Stock Assessments And Management Advice For Bluefin Tunas And Other Highly Migratory Species, Lisa Elma Ailloud

Dissertations, Theses, and Masters Projects

For years bluefin tuna has been the poster child for overfishing and poor management. However, recent improvements in data collection, catch monitoring and international cooperation are providing an opportunity to reverse the perception of a fishery that is doomed to collapse. Stock assessments are conducted routinely to monitor the abundance and productivity of exploited fish stocks so managers can determine how many fish can be sustainably harvested each year. Should a stock be declared overfished or under-going overfishing, the science behind stock assessments also equip managers with the knowledge necessary to make decisions about what short-term and long-term management measures …

Preliminary Estimate Of Contribution Of Arctic Nitrogen Fixation To The Global Nitrogen Budget, Rachel E. Sipler, Donglai Gong, Se Baer, Mp Sanderson, Qn Roberts, M Mulholland, Da Bronk

VIMS Articles

Dinitrogen (N-2) fixation is the source of all biologically available nitrogen on earth, and its presence or absence impacts net primary production and global biogeochemical cycles. Here, we report rates of 3.5-17.2 nmol N L-1 d(-1) in the ice-free coastal Alaskan Arctic to show that N-2 fixation in the Arctic Ocean may be an important source of nitrogen to a seasonally nitrogen-limited system. If widespread in surface waters over ice-free shelves throughout the Arctic, N-2 fixation could contribute up to 3.5 Tg N yr(-1) to the Arctic nitrogen budget. At these rates, N-2 fixation occurring in ice-free summer waters would …