Marine Ecosystem Response
My research focuses on marine ecosystem responses; understanding relationships between organisms and their environment and specific biological and physiological responses to environmental change. In particular, I am interested in the mechanisms by which anthropogenic-driven perturbations such as nutrient enrichment and pollution, the presence of coastal structures, global climate change, or harvest pressure affect coastal habitats and species. I give special focus to commercially important coastal bivalves and horseshoe crabs.
Research Interests Lab website
I use a variety of approaches to make these assessments. I measure how perturbations affect habitat and food quality for consumers, and then determine the extent to which these effects may be transferred up coastal food webs in terms of change in growth, survival, and physiology. I also employ natural abundance stable isotopes to trace N and C sources from consumers to their food sources and ultimately to N and C sources from land. I use this information to discern trophic interactions and define linkages between anthropogenic factors and organism responses, but also to assess nutritional importance of food sources, discern physiological state of organisms, and historically trace responses to environmental change.
Specific Research Topic
- Study of the extralimital Manatee population in Mobile Bay, AL
a. A model for conservation management by integration of
research and public outreach
b. Use of telemetry and GPS to monitor West Indian manatee
movements in Alabama waters
- Use of stable isotope ratios to link wastewater sources to effects on shellfish and human health
- The effects of nutrient enrichment on oyster ecology in Mobile Bay
refining and testing a method to determine N stable isotope ratios within annual bands of bivalve shells. These data are applied to trace historical changes in land-derived N loads to estuaries and into estuarine ecosystems. These data will be compared to the short and long-term physiological state of bivalves through time and correlated with other large-scale processes such as global climate change or variation in submarine groundwater discharge. This approach will be useful to discern the relative importance of anthropogenic change compared to natural environmental variation through time.
applying nutritional data obtained from stable isotope analyses to develop and refine artificial diets for horseshoe crabs to inform aquaculture efforts. These data can be combined with data on responses to specific habitat variables to support emerging aquaculture enterprises and aid conservation of natural stocks.
comparing changes in population dynamics among horseshoe crabs at extreme edges of their geographic range. This work will compare data from horseshoe crabs in Maine (northernmost habitat) to those in Alabama (southwesternmost habitat). Horseshoe crab populations in these regions are relatively sparse and poorly studied, as well as considered unique and potentially fragile because they live at the fringe of their viable habitat. The status of these populations may become more important as global climate change, increasing habitat loss, and harvest pressure affect populations elsewhere.
developing a method to use natural abundance stable isotopes to trace metabolic responses of bivalves to environmental stress, specifically tracing responses that may not otherwise be detectable until an organism dies, such as responses to hypoxia. This method also may be applied to assess bivalve responses to harmful algal blooms or to predict depuration rates after contamination.
Selected Current Research Grants
MS-AL Sea Grant Consortium, Use of stable isotope ratios to link wastewater sources to effects on shellfish and human health: Defining relevant and effective spatial and temporal scales for management. 2007
Alabama Oyster Reef Restoration Program, Univ. of South Alabama, Effects of N enrichment on oyster growth and survival via changes in food supply and habitat in Mobile Bay, AL. 2007
Alabama Division of Wildlife and Freshwater Fisheries, A pilot study of the extralimital West Indian Manatee population in Mobile Bay, AL. 2007
Maine Sea Grant Program - Assessing the potential for successful culture of the Atlantic Horseshoe crab, Limulus polyphemus, in Maine. 2005
Past Research Grants
MIT Sea Grant Program - Stable isotope approaches to understand and monitor eutrophication in land-estuary ecosystems. 2004
WHOI Sea Grant Program - The effects of anthropogenic N load on commercially important bivalves. 2002
J. Bowen, K. Kroeger, G. Tomasky, W. J. Pabich, , M. L. Cole, R. H. Carmichael, Valiela, I. A review of land-estuary coupling by groundwater discharge to New England estuaries: Mechanisms and effects. Applied Geochemistry. 22: 175-191.
Carmichael, R. H. and I. Valiela. 2005. Coupling of near-bottom seston and surface sediment composition: Changes with nutrient enrichment and implications for estuarine food supply and biogeochemical processing. Limnol. Oceanogr. 50:97-105.
Carmichael, R. H., A. Shriver and I. Valiela. 2004. Changes in shell and soft tissue growth, tissue composition, and survival of quahogs, Mercenaria mercenaria, and softshell clams, Mya arenaria, in response to eutrophic-driven changes in food supply and habitat. J. Exp. Mar. Biol. Ecol. 313:75-104.
Carmichael, R. H., B. Annette and I. Valiela. 2004. N loading to Pleasant Bay, Cape Cod: Application of models and stable isotopes to detect incipient nutrient enrichment of estuaries. Mar. Pollut. Bull. 48:137-143.
Carmichael, R. H. 2004. Effects of eutrophication on Mya arenaria andMercenaria mercenaria: Growth, survival, and physiological responses to changes in food supply and habitat in estuaries receiving different N loads. Ph.D. Thesis, Boston University.
Carmichael, R. H., D. Rutecki, B. Annett, E. Gaines and I. Valiela. 2004. Position of horseshoe crabs in estuarine food webs: N and C stable isotopic study of foraging ranges and diet composition. I. Exp. Mar. Biol. Ecol. 299: 23 1-253.
Carmichael, R. H., D. Rutecki and I. Valiela. 2003. Abundance and population structure of the Atlantic horseshoe crab, Limulus polyphemus, in Pleasant Bay,Cape Cod . Mar. Ecol. Prog. Ser. 246:225-239.
Shriver, A. C., R. H. Carmichael and I. Valiela. 2002. Growth, condition, reproductive potential, and mortality of bay scallops, Argopecten irradians, in response to eutrophic-driven changes in food resources. J. Exp. Mar. Biol. Ecol. 279:21-40.
Gaines, E., R. H. Carmichael, S. P. Grady and I. Valiela. 2002. Stable isotopic evidence for changing nutritional sources of juvenile horseshoe crabs. Biol. Bull. 203:228-230.
|Current Graduate Students
||Post Doctoral Associates
Heather Patterson, Ph.D.
Peter Biancani, M.S.
Allen Aven, M.S.