Research Projects
My current and recent projects are described below:
Previous Earlier projects:
Hypoxia in Marine Ecosystems: Implications for Neritic Copepods
Funded by NSF OCE
Participants may click here to acces a password protected site.
The occurrence of low-oxygen waters, often called "dead zones" in coastal ecosystems throughout the world is increasing. Despite these increases, the pelagic food-web consequences of low-oxygen waters remain poorly understood. Laboratory research has demonstrated that hypoxic water (< 2 mg l-1) can result in mortality, reduced fitness and lower egg production of planktonic copepods, a major link in food webs supporting pelagic fish. Observations in the sea indicate that hypoxic bottom waters usually have depressed abundances of copepods compared to normoxic waters (> 2 mg l-1). The gradient of declining oxygen concentration with respect to depth (oxycline) can be a critical interface in coastal pelagic ecosystems by altering the migratory behavior and depth distribution of copepods and their spatial coherence with potential predators and prey. This project will result in a mechanistic understanding of how behavior and fitness of copepods are affected by hypoxia. The PIs will compare bottom-up and top-down controls on the ecology of copepods in Chesapeake Bay waters experiencing seasonal hypoxia and those that are normoxic.
Specific objectives of this project are to: 1) analyze changes in migratory behavior and fine-scale (meter) distribution of copepods across the oxycline over hourly and diel time scales while simultaneously examining the distribution and abundance of their food (phytoplankton and microzooplankton) and predators (fish, gelatinous zooplankton); 2) estimate effects of hypoxia on the "fitness" of copepods using a suite of measurements (length/weight ratios, feeding, egg production, and egg hatching success) to develop condition indices of copepods captured at different times and depths in hypoxic and normoxic waters; and 3) evaluate effects of hypoxia on copepod mortality by hypoxia-induced, stage-specific copepod mortality in hypoxic bottom waters and by changes in top-down control of copepods from predation by fish and gelatinous zooplankton. Oxyclines may be a barrier to vertical migration of copepods and thus disruptive to predator avoidance behavior. Faced with increased predation risk from fish and jellyfish, copepods may seek refuge in hypoxic waters for part of the day and/or make short-term vertical excursions between hypoxic and normoxic waters. By regulating vertical migrations, copepods may increase utilization of microzooplankton prey concentrated in the oxycline. Hypoxic waters may elevate consumption of copepods by jellyfish and depress consumption by pelagic fish. This project will evaluate copepod distribution and migration behavior, individual fitness and stage-specific mortality in hypoxic and normoxic waters. It will examine food-web consequences of increased or decreased spatial coherence of copepods and their predators and prey in regions with hypoxic bottom waters and will contribute to fundamental understanding of food-web processes in eutrophic coastal ecosystems.
Collaborators:
- Michael Roman, Diane Stoecker, & Ed Houde, University of Maryland Center for Environmental Sciences
- Mary Beth Decker, Yale University
Modeling the Impacts of Hypoxia on Ecologically and Commercially Important Living Resources in the Northern Gulf of Mexico
Funded by NOAA CSCOR
Participants may click here to acces a password protected site.
To assess the full impact of hypoxia on living resources of the Northern Gulf of Mexico (NGOMEX) requires a multi-scale (both time and space) and multi-stressor approach. This project proposes a framework to simultaneously account for direct and indirect effects of hypoxia, including their linear and non-linear interactions on key organisms to support ecosystem-based management in the NGOMEX. A battery of modeling approaches of varying complexity (individual - to ecosystem-level), spatial configuration (near-field plume to fine-scale spatial pelagic to entire NGOMEX), and temporal duration (hourly to inter-annual) will be employed to provide both understanding and forecast capabilities to the management community of the NGOMEX.
Multiple models will be used to evaluate:
- What is the effect of the spatial extent and seasonal timing of hypoxia on fish growth, recruitment and production potential?
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How does hypoxia affect food web interactions in the pelagic zone? Specifically:
- How will hypoxia affect the spatial distribution and predator-prey interactions of mobile organisms and zooplankton?
- How does hypoxia affect habitat quality and suitability for economically and ecologically important fishes?
- How will management decisions on loadings affect fisheries through its impact on the timing and extent of hypoxia?
- What is the potential of strong wind events (and their relationship to climate change) to re-aerate the water column and alter the interactions of fish and their prey?
- What are the most effective tools to forecast food-web interactions, habitat suitability, and fish production in relation to hypoxia?
It is hypothesized that hypoxia in the NGOMEX can strongly impact pelagic food webs and production through unexpected, indirect pathways, potentially leading to changes in production potential (both positive and negative) of economically and ecologically important fishes. Our overall goal is to provide quantitative tools to probabilistically forecast the effects of hypoxia on the living resources in the NGOMEX. Direct linkages to fisheries management will ensure continued interaction with, and attention to, the critical management issues.
Collaborators:
- Michael Roman, University of Maryland Center for Environmental Sciences
- Stephen Brandt & Sarah Kolesar, Oregon State University
- James Cowan & Kim deMutsert, Louisiana State University
- Doran Mason and Craig Stow, NOAA Great Lakes Environmental Research Laboratory
- Shaye E. Sable, Louisiana Department of Fishes and Wildlife
- Aaron Adamack, University of Michigan
- Fredrick Sutter, NOAA NMFS Southeast Regional Office
GLOBEC Pan Regional Synthesis: Life histories of species in the genus Calanus in the North Atlantic and North Pacific Oceans and responses to climate forcing
Funded by NSF OCE
Species in the genus Calanus are predominant in the mesozooplankton of the North Atlantic and North Pacific Oceans. Their key role in marine food web interactions has been recognized in GLOBEC programs, both in the U.S. and internationally. Considerable knowledge of life history characteristics, including growth, reproduction, mortality, diapause behavior and demography has been acquired from both laboratory experiments and measurements at sea. This project reviews and synthesizes this knowledge and uses it to develop an Individual Based Life Cycle model for sibling species in two sympatric species pairs, C.marshallae and C. pacificus in the North Pacific Ocean and C. finmarchicus and C.helgolandicus in the North Atlantic, that have been the particular focus of GLOBEC programs and other recent research projects in the U.S., Canada and Europe. The IBLC model is then applied to make predictions about the life history response of each species to forcing under reasonable climate change scenarios for ambient food and temperature. The project involves training of a graduate student and two postdoctoral researchers in evaluation and prediction of effects of climate change on marine plankton populations. It fosters international collaboration with Canadian and European researchers, including participation in a workshop in Europe. Outreach to the broader fishing and management community is through seminars, information exchange sessions with fishermen managers, including the Maine Fisherman’s Forum, collaboration in affiliated projects with colleagues involved in herring and tuna research in the Gulf of Maine and in climate and fisheries interactions within NOAA.
Collaborators:
- Dr. Jeff Runge, UMaine, GMRI
- Dr. Andrew Leising, NOAA, SWFSC
- Dr. David Kimmel, ECU
- Dr. Andrew Pershing, UMaine, GMRI
Participants may click here to go to the participants site (some material password protected).
BITMAX II: Dynamic stability and particle transformations: tracing pathways of production in Estuarine Turbidity Maxima
Funded by NSF OCE
Estuarine turbidity maxima (ETMs) are turbid water regions located at the heads of coastal plain estuaries, near the landward limit of saltwater intrusion. They trap sediment, detritus, zooplankton and fish early-life stages, enhance secondary production, and serve as critical nursery areas for economically important fishes.
The overall goal of this project is to evaluate and explain why the Chesapeake Bay ETM is dynamically stable and supports enhanced secondary production. Our specific hypotheses are:
- Particle aggregation promotes formation and retention of nutritious particles in the ETM.
- Particle-attached bacteria enrich the nutritional value of food for copepods, transforming the microbial loop into a microbial shunt.
- Abundant food and stable stratification enhance the feeding conditions and production of copepods and fish larvae.
- Life-history strategies of key ETM species are adapted to take advantage of event-scale changes (pulses) in ETM circulation patterns.
Collaborators:
- Dr. Ed Houde, CBL
- Dr. Byron Crump, HPL
- Dr. Elizabeth North, HPL
- Dr. Mike Roman, HPL
- Dr. Larry Sanford, HPL
- Dr. Shenn-yu Chao, HPL
- Dr. Raleigh Hood, HPL
- Dr. Dave Kimmel, ECU
Forays and foraging in marine zooplankton
Funded by NSF OCE
This project seeks to explore the hypothesis that zooplankton make repeated short distance migrations into and out of the high chlorophyll surface layer throughout the night. Although diel vertical migration (DVM – a pattern in which zooplankton reside at depth during the day and near the surface at night) is a prevalent behavior among many zooplankton species, often the peak abundance of zooplankton is found below the depth of the chlorophyll maximum. To study this hypothesis, we are developing a zooplankton “trap” to catch zooplankton as they move between layers throughout the night, and we will collect animals migrating into and out of the chlorophyll rich layer. In addition, we will make physiological and morphological measurements on individuals to see if we can determine how individual behaviors might affect the observed population distributions and explore physiological cues (e.g. gut fullness) that might lead to observed migration patterns.
Collaborators:
- Dr. Andy Leising, PFEL/NOAA
- Dr. Bruce Frost, UW
- Mikelle Nuwer, UW
- Jim Postel, UW
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