Our group is interested in determining (1) the relationships between 'top-down' (nutrient) and 'bottom-up' (grazer) controls on phytoplankton assemblages, (2) the causes and consequences of HABs for ecosystem and human health, (3) novel techniques for identifying and quantifying natural phytoplankton assemblages. We use a combination of field, laboratory, and in situ approaches to conduct our research.
Select Current Projects
Algal bloom monitoring and fish kill responses. Fish kills are common events along the South Carolina coast, particularly during the summer and in residential neighborhoods with detention ponds, human-made systems built as catchments for stormwater. Responses entail on-site evaluations of fish kill events for water quality, nutrients, and phytoplankton to assess whether HABs may be a cause. Efforts have shown that approximately 1 in 4 of South Carolina coastal fish kills were associated with algal blooms, mostly HABs, over the past decade (hypoxia is the major cause). Work funded by the CDC expands the lab’s long-term (since 2001) database, and fish kill response data are contributed to HABISS, the CDC’s database. Long-term monitoring primarily focuses on brackish stormwater detention ponds because these poorly-flushed systems tend to accumulate runoff, making them susceptible to HAB formation. Funding for this multi-agency work is courtesy of 1) the CDC, awarded to PIs R. DeVoe, J. Glover, D. Greenfield, and others; 2) SRFAC, awarded to PIs D. Greenfield and C. Keppler; 3) Private contract, Kiawah Island Community Association.
Public outreach: Water quality, HABs, and stormwater detention ponds. Stormwater detention ponds are routinely constructed within recreational (parks, golf courses) and residential settings across the South Carolina coast. Since these shallow systems tend to stagnate and accumulate nutrients from fertilizers and other runoff, they are ideal environments for HAB formation. Through a multi-agency effort, we present informational seminars at homeowners’ association board meetings about bloom formation, proper reporting of bloom and fish kill events, identifying potential HAB-related illnesses, and bloom prevention. This effort has also included a Q&A workshop for managers, researchers, and the general public. Funding for this work is courtesy of SC Sea Grant.
Evaluating nutrient levels and cycling in South Carolina coastal systems. Coastal South Carolina is undergoing some of the most rapid urbanization in the country, including industry, managed wetlands, residential neighborhoods, and golf courses that contribute nutrients to receiving waters. It is generally accepted that elevated nitrogen (N) and phosphorus (P) levels contribute to eutrophication and algal blooms in a wide range of aquatic systems. Yet, surprisingly little is known about how nutrient levels affect phytoplankton community composition and biomass in South Carolina estuaries. Work under this research theme combines field and laboratory experimentation to assess N and P levels across coastal South Carolina and determine responses of key phytoplankton species to various nutrient forms and levels in select coastal regions representing diverse land use patterns. Results will be useful for decision makers when considering numeric criteria for estuarine nutrients. Funding for this work is courtesy of 1) state revenue funds (previous), and 2) the EPA (current), awarded to PIs D. Greenfield and R. Van Dolah.
MERHAB: Comparative analysis of quantitative detection methods for enumeration of HAB species: Applications for resource management. Cell homogenate approaches have been developed to quantify HAB species using quantitative real-time PCR (QPCR) and sandwich hybridization assay (SHA). With QPCR, species are enumerated by enzymatic amplification of DNA. By comparison, SHA directly detects RNA from an unpurified/unamplified homogenate. Both methods have been validated for HAB species quantification, but they have not been thoroughly compared, representing a gap in the ability to provide recommendations to managers. This effort provides a thorough assessment of QPCR and SHA for HAB monitoring and research using laboratory and field studies using the globally-distributed harmful raphidophyte, Heterosigma akashiwo as a model species. Funding for this work is courtesy of NOAA/NOS, and it is awarded to PIs D. Greenfield and K. Coyne.
Development of a novel genetic approach to rapidly detect fish eggs of economically important species: A new tool for fisheries management. Indices of fish egg production are essential for understanding recruitment and developing stock assessment models for species management. Traditional methods of enumerating and identifying planktonic fish eggs entail time-consuming microscopy, and eggs of different species are often morphologically indistinguishable leading to faulty population assessments that affect fishery management decisions. This project provides an entirely novel application of SHA by adapting it to the economically important fish species, red drum (Sciaenops ocellatus). Funding for this work is courtesy of SC Sea Grant, and it is awarded to PIs D. Greenfield and S. Arnott, collaborator J. Jones.
Development of a genetic tool to rapidly identify and quantify HAB species linked with fish kills and public health concerns. Incidences of HABs are increasing globally. In coastal SC, HABs are associated with 1 out of 4 fish kills, and phycotoxins are routinely detected, making HABs an environmental and public health threat. Traditional methods for identifying and quantifying HABs use time-consuming microscopy. Moreover, many species are morphologically similar, which is problematic for early warnings and management decisions. Work proposed here develops a novel and economical molecular tool (sandwich hybridization assay; SHA) that facilitates rapid and accurate HAB assessments. We are developing assays for 3 locally-abundant species: two icthyotoxic raphidophytes and one regional diatom (Pseudo-nitzschia sp.). Funding for this work is courtesy of SC Sea Grant, and it is awarded to PIs D. Greenfield and J. Jones.