My current and recent projects are described below:
Selected previous research projects:
- Hypoxia in Marine Ecosystems: Implications for Neritic Copepods (summary here)
- Modeling the Impacts of Hypoxia on Ecologically and Commercially Important Living Resources in the Northern Gulf of Mexico
- RAPID Collaborative Research: Historic freshwater input and hypoxia effects on zooplankton populations of the northern Gulf of Mexico (summary here)
- RAPID Collaborative Research: Spatially-explicit, High-resolution Mapping and Modeling to Quantify Hypoxia and Oil Effects on the Living Resources of the Northern Gulf of Mexico (summary here)
- Predicting Striped Bass (Morone saxatilis) recruitment in the Chesapeake Bay
- 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 (summary here)
- Dynamic Stability and Particle Transformations: Tracing Pathways of Production in Estuarine Turbidity Maxima
- Forays and Foraging in Marine Zooplankton
Short Descriptions of Current Projects:
The effects of diatom-produced polyunsaturated aldehydes on the microbial food wed in temperate and polar waters
Funded by NSF OCE
This project will conduct a set of field/laboratory experiments to address the following hypotheses with respect to microzooplankton (consumers between 20-200 µm) and diatom- produced polyunsaturated aldehydes:
I. Aldehydes will impair microzooplankton herbivory on diatoms and non-diatom phytoplankton.
II. Aldehydes will reduce the growth rates of microzooplankton and non PUA-producing phytoplankton.
III. In the presence of aldehyde-producing diatoms, copepods will switch to microzooplankton, whereas non- (mildly)- toxic diatoms will be an important food source for copepods.
IV. The effects of aldehydes on microzooplankton and copepods will depend on the grazers' prior exposure to PUA.
The experiments will include natural plankton, captured copepods, cultured Skeletonema marinoi (SM), including its aldehyde-producing strain, and synthetic aldehydes. To gain insights into complex interactions within planktonic communities, detailed information on their composition, abundance, and dynamics will be obtained using microscopy, flow-cytometry, and cytological methods. This approach will allow the PIs to draw conclusions about the role of diatom-produced aldehydes in phytoplankton-microzooplankton- copepod trophic interactions. The PIs will coordinate efforts and exchange information with the PUA study group at the Stazione Zoologica Anton Dohrn (Naples, Italy).
Intellectual merit: Diatoms are dominant autotrophic plankton in the ocean. Recent evidence indicates that microzooplankton are the dominant herbivores, whereas copepods often rely on microzooplankton as food, except during peak diatom production. The ability of microzooplankton to feed on large diatoms and grow as fast as their algal prey leads to the question of what allows diatoms to escape microzooplankton grazing control during the initial phases of their blooms and maintain the blooms until nutrient resources are depleted? Allelopathy is wide spread among phytoplankton. The cosmopolitan bloom-forming SM produces several aldehydes and has become a model organism in plankton allelopathy studies. Most studies on diatom cytotoxicity have been dedicated to inhibitory effects on reproduction and development of marine invertebrates, whereas surprisingly little information exists on its impact on key diatom grazers, microzooplankton. Preliminary results in the Chesapeake Bay show that aldehydes may induce cascading effects within planktonic communities. The proposed study will: (1) Improve our knowledge of the critical diatom-microzooplankton-copepod links in the coastal ocean; (2) Generate novel data on the effects of allelopathy on marine food webs; (3) Contribute to our understanding of broader patterns of marine ecosystems by comparing plankton structure and dynamics in the temperate Atlantic waters; (4) Advance biological oceanography through international collaboration.
Broader Impacts: One post-doctoral fellow, two graduate students and several undergraduate students at the Universities of Akron and Maryland will be trained as a result of this project. The project will attract motivated minority students into the program. The research will be extended to students in grades 7-12 and teachers via an interactive distance learning series in collaboration with the WVIZ Ideastream network. The PIs will continue an existing outreach partnership with the Great Lakes Science Center, where a recent electronic presentation dedicated to Arctic change and NSF-sponsored research was seen by ca. 45,000 visitors. The PIs will also work with the Cleveland Museum of Natural History to develop public programs, and with the National Inventors Hall of Fame STEM Middle School to develop a curriculum focused on polar research. Curriculum modules will be available as free downloads from a dedicated website. Broader Impacts, LLC, will evaluate these education and outreach activities.
Copepod Population Dynamics in Hypoxic Coastal Waters: Physical and Behavioral Regulation of Resupply and Advective LossesFunded by NSF OCE
The PIs will develop a mechanistic understanding of how circulation interacts with hypoxia-induced behavioral and physiological changes to affect the population dynamics of coastal zooplankton. They will do this by assessing two potentially contrasting mechanisms influencing the dynamics of the copepod Acartia tonsa in the hypoxic zone of Chesapeake Bay. The first hypothesis is that maintenance of copepod populations in the hypoxic region requires replenishment by advection (immigration) of animals through wind-driven lateral transport processes. The second, counteractive, hypothesis is that bottom water hypoxia alters the vertical distribution of A. tonsa, thereby making them more susceptible to advective losses from the region (emigration) via surface water transport in the estuarine circulation. They will take advantage of a current NSF-funded physical oceanography research program in Chesapeake Bay that will comprehensively measure and model axial and lateral water exchanges in the mid-Bay region.
The present study will use the physical oceanography study site as a Controlled Volume (CV) in which the oceanographic exchanges of water and the driving mechanisms for those exchanges will be well defined. The PIs will conduct high-resolution spatial and temporal sampling of zooplankton and combine the data with measurements of copepod behavior, mortality and egg production in the hypoxic region. They will use an improved Individual-Based Model of the life history of A. tonsa coupled with the circulation to explore the combined effects of advection, behavior, egg production, and mortality on population dynamics. In addition to increasing our knowledge of the impacts of bottom water hypoxia on copepod populations in Chesapeake Bay, the study will improve our general understanding of the regulation of zooplankton populations by physical and biological processes and the impacts of hypoxia on secondary production and food webs in coastal waters.
The project will enhance existing public education and outreach efforts so that the public can be better informed about the effects of hypoxia on Chesapeake Bay. This will be accomplished in part through the Center for Ocean Science Education Excellence (COSEE) Coastal Trends program (now the Horn Point Laboratory STEM Center Student Learning Activities program). The PIs will enhance an existing set of online education modules (http://www.teachoceanscience.net/) that focus on the causes and consequences of the Chesapeake Bay's "Dead Zone" through development of an online interactive version of their synthetic plankton model. The study also includes participation by undergraduate summer interns through a Research Experience for Undergraduates (REU) program. In addition, this research will contribute information toward the development and improvement of dissolved oxygen criteria for Chesapeake Bay, will support broad initiatives of the Chesapeake Bay Program by providing information on the role of zooplankton in supporting productivity of fisheries, and will contribute information to ecosystem-based fisheries management plans.