Research

My students and I address a wide array of topics that are centered around sessile benthic invertebrates that occur on both tropical and temperate reefs. In recent years much of the focus has been on recruitment processes, but students in my lab have addressed everything from antipredator chemical defenses to controls on population genetic structure. My research program tends to be driven by interesting questions rather than past experience, so I am always willing to entertain new and intriguing research directions. I view this as one of the wonderful aspects of having a career in academia: if it interests you and you can fund it, you can investigate it.

Below I have summarized some of the research conducted in my lab in recent years. Please contact me if you have an interest in any of these areas or would like to discuss other ideas that are related to any of these topics.

Connectivity between Georgia Rivers and offshore marine habitats

It is well-documented that pollutants such as pesticides and excess nitrogen are transported from human activities on land to rivers and eventually to estuaries. While pollutants can negatively affect estuarine health, the potential for their transport to and impact on critical near- and offshore habitat is less clear. This knowledge gap exists because of 1) a natural division in scientific disciplines, i.e. estuarine ecologists focus on waters bounded by the estuary whereas oceanographers conduct investigations in deeper waters offshore, and 2) jurisdictional boundaries of government entities. The result is that linkages between estuarine and offshore ecosystems are often assumed, but rarely investigated. However, if we are to develop coastal management plans that are holistic, documenting the presence and extent of connectivity between estuarine and offshore water masses is a knowledge gap that must be filled. We propose to conduct a study that will begin to improve our understanding of the connectivity between one of the largest river outflows on the Atlantic seaboard, the Altamaha River Estuary, and critical offshore habitats (i.e., 5-20 NM off the coast) of the South Atlantic Bight (SAB). To begin deciphering these connections we will release a non-toxic water tracing dye (rhodamine WT) into the Altamaha River outflow during times of high and low freshwater discharge, and will track the dye as it moves offshore. Tracking will be accomplished using a combination of visual, fluorometric, and Geographic Information System (GIS) methods and will allow calculations of dispersion coefficients for dissolved substances coming out of the estuary. The offshore targets will be five sport fishing sites located at various distances north, south, and east of the dye drop location. These sites encompass artificial and natural reef structures along the Georgia coast that are visited frequently by sport fisherman and harbor abundant fish and bottom-dwelling invertebrate populations.

Effects of Ocean Acidification

Excess CO₂ released into the atmosphere from human activities is partially absorbed by the oceans resulting in ocean acidification (OA), a term coined because the most prominent chemical change is a reduction in sea water pH. While the effects of OA on organisms has been studied extensively in some ecosystems, such as coral reefs and oceanic plankton, comparable investigations have not been completed for organisms occupying hard bottom reefs of the South Atlantic Bight (SAB). Live bottom reefs in the SAB are biodiversity hotspots as they are colonized by a proliferation of sponges, tunicates, corals, bryozoans, and algae that in turn attract and support abundant and diverse fish populations. In this project, we are conducting a series of laboratory experiments to assess the effects of OA on ecologically important benthic invertebrates and algae that encrust hard bottom reefs of the SAB. In carrying out this study there are two specific aims. Initially OA sensitivity experiments are being conducted on ten different species common on SAB reefs. These species cover the broad taxonomic diversity (corals, sponges, tunicates, algae, etc.) and functional diversity (calcifiers, photosynthesizers, consumers) present on these reefs. Having identified species that are highly sensitive to OA, the future aim is to characterize the response of these species under more realistic conditions. Specifically, experiments will be conducted to assess the effects of OA within the context of strong seasonal cycles in water temperature and inorganic carbon parameters common in the SAB, as well as within the additional framework of long-term increases in temperatures due to climate change. The study is taking place at a site in NOAA’s Ocean Acidification Monitoring Network where the chemical effects of OA are being monitored, but no complimentary work on the biological effects of OA have been conducted.