Over the past ten years, my research has been focused primarily in three areas in aquatic ecosystems:
- Chronic effects of nutrient over-enrichment (eutrophication) and other chemical environmental contaminants (CECs) on aquatic plants (algae, angiosperms)
- The ecology and impacts of harmful algae (cyanobacteria, dinoflagellates, haptophytes, raphidophytes
- Influences of long-term (decadal+) changes in watershed land use and pollution sources on surface water quality
I am the Director of the Center for Applied Aquatic Ecology (CAAE), located in the Department of Plant and Microbial Biology at NCSU. Our research team has designed and maintained a 14-year ongoing research and monitoring program on the Neuse Estuary. We developed and patented an instrument that allows automated depth profiles of water quality on an hourly basis, 24/7, to track environmental changes, examine the ecology of harmful algae, and improve assessment of fish kill causality. We also have designed and maintained a 6-year ongoing research and monitoring program in three major potable water supply reservoirs in North Carolina. We are working to combine our real-time, automated sampling capability with microarrays to detect toxic cyanobacteria (blue-green algae), pesticides and other CECs, and microbial pathogens to improve early warning systems to safeguard public water supplies. We recently completed a decadal study on land use changes in the Neuse watershed, emphasizing the importance of both urban and agricultural pollutant sources. We documented a striking increase in ammonium concentrations, by more than 500%, in surface waters affected by numerous confined swine feed operations. The increased ammonium supply is significantly related to an increase in algal species such as the raphidophyte, Heterosigma akashiwo, that is potentially toxic to humans. In earlier work, we co-discovered potentially toxic estuarine dinoflagellates (Pfiesteria piscicida, P. shumwayae), stimulated by nutrient over-enrichment, than can cause major fish kills. The findings provided the foundation for recent research by toxin chemists at NOAA (Charleston, SC), who described a group of potent Pfiesteria toxins, new to science, with potential application in treating memory disorders.
Ph.D. Botanical Limnology Michigan State University 1986
M.S. Aquatic Botany University of Rhode Island 1981
B.S. Zoology Iowa State University 1975
Area(s) of Expertise
Aquatic ecology and dinoflagellates
- Diversity of bioactive compound content across 71 genera of marine, freshwater, and terrestrial cyanobacteria , HARMFUL ALGAE (2021)
- An Environmental Assessment of the North and South Carolina Coasts , WORLD SEAS: AN ENVIRONMENTAL EVALUATION, VOL I: EUROPE, THE AMERICAS AND WEST AFRICA, 2ND EDITION (2019)
- Odorella benthonica gen. & sp. nov. (Pleurocapsales, Cyanobacteria): an odor and prolific toxin producer isolated from a California aqueduct , JOURNAL OF PHYCOLOGY (2019)
- Sampling bias misrepresents the biogeographical significance of constitutive mixotrophs across global oceans , GLOBAL ECOLOGY AND BIOGEOGRAPHY (2019)
- Assessment of atrazine toxicity to the estuarine phytoplankter, Dunaliella tertiolecta (Chlorophyta), under varying nutrient conditions , Environmental Science and Pollution Research (2018)
- Chattonella subsalsa (Raphidophyceae) growth and hemolytic activity in response to agriculturally-derived estuarine contaminants , Harmful Algae (2018)
- Imbalanced nutrient regimes increase Prymnesium parvum resilience to herbicide exposure , Harmful Algae (2018)
- Mixotrophy in Harmful Algal Blooms: By Whom, on Whom, When, Why, and What Next , GLOBAL ECOLOGY AND OCEANOGRAPHY OF HARMFUL ALGAL BLOOMS (2018)
- Environmental stressors and lipid production by Dunaliella spp. I. salinity , Journal of Experimental Marine Biology and Ecology (2017)
- Environmental stressors and lipid production in Dunaliella spp. II. nutrients, pH, and light under optimal or low salinity , Journal of Experimental Marine Biology and Ecology (2017)
The southeastern United States (US) is the richest region of global diversity for freshwater mussel, snail, fish, and crayfish, and is, therefore, a region of high conservation priority. However, this high regional biodiversity intersects with intense pressures of energy mining and development, urbanization and sprawl, increasingly intensive agricultural practices, and growing demands on water and other natural resources for human use. Nestled within this complex landscape, and falling within this rich faunal province, North Carolina contains streams that drain to the Interior Basin (Tennessee â€“ Cumberland) in the west and to the Atlantic Ocean (Atlantic Slope) in the Piedmont and East. The species of freshwater mussels (Unionoida), snails, and fish vary among these regions of the state, face differing landscape and water quality challenges, and, therefore, have differing statues of conservation concern. For example, North Carolina once supported more than 60 species of freshwater mussels, but unfortunately, 50% of these species are now designated as Endangered, Threatened, or of Special Concern and the stateâ€™s 161 freshwater fish of conservation concern are also likely integral to the unique unionoid mussel life cycle, serving as obligate hosts during the musselsâ€™ parasitic larval stage. Because of these declines and degree of imperilment, protection, restoration, and conservation of these irreplaceable aquatic organisms are paramount. The proposed research will specifically benefit these imperiled mollusks and non-game fishes and contains objectives related to their captive propagation and culture, improvement of their water quality and riparian environment, and better understanding of their ecosystem function and services. The specific tasks include: (1) propagation and culture of the federally endangered Dwarf Wedgemussel, the at-risk Yellow Lance mussel, and the at-risk Magnificent Ramshorn snail; (2) understanding the ecosystem functions and services provided by native freshwater mussels and their associated economic and social benefits to humans and other wildlife; (3) determining the effects of transportation and energy production stressors on the survival, health and well-being of native freshwater mussels; and (4) assessing the integrated risk, ecology, and control of Giant Lyngbya (an invasive Cyanobacteria species) on native mussels. These collective projects will provide natural resource managers and other decision makers with the tools, organisms, and science-based information needed to restore, improve, and conserve these important faunal resources.
Falls Lake Partners in Forensic Science is a three-year project designed to engage 8th grade/rising 9th grade students of Wake County, NC in STEM and Information Technology content and career education, through handson learning experiences in â€œforensicâ€ investigative aquatic science. This project partners middle school students in the watershed (Carnage Middle School â€“ 420 8th graders, 70% African-American and other minorities; and Moore Square Middle School â€“ 145 8th graders, 64% African-American and other minorities, and NCSUâ€™s Center for Applied Aquatic Ecology (CAAE). The overall goals are to encourage underprivileged minority, female, and special needs American youth to appreciate the direct connections between water quality, healthy aquatic life and healthy people; and to inspire students to pursue STEM careers in aquatic science and water resource management. The specific objectives are to: 1) Kindle studentsâ€™ interest in aquatic science through short, interactive presentations to all 1,060 8th grades followed by brief classroom visits, emphasizing the importance of Falls Lake to their everyday health and the health of their families and friends; 2) Excite students and their teachers about aquatic science by providing hands-on experiences which teach them the science underpinning issues that affect lake water quality; 3) Inspire students to pursue STEM careers in aquatic science and water resources management through direct interactions with aquatic specialists; and 4) Provide related classroom activities, career information, and references to enhance teachersâ€™ skills in teaching aquatic science. All activities involved in addressing these objectives will be correlated to Goals 8E.1.1. â€“ 220.127.116.11 of the NC Essential Science Standards. Mentored by CAAE scientists, students will complete a Science Fair-caliber project in their special are of interest about Falls Lake science, including a poster and PREZI presentation given in the fourth Saturday session. Selected students will serve as peer mentors to Falls Lake Partners students in subsequent project years.
North Carolina State Universityâ€™s Center for Applied Aquatic Ecology (CAAE) will conduct a three-part study in Falls Lake. First, additional research will be completed to assess nutrient and TOC inputs and trends from the upper to the middle lake and from the middle lake to the lower lake. Water quality sampling and other monitoring at our present sites will be continued as in previous years. Samples collected will be analyzed by the CAAEâ€™s State- Certified Analytical Laboratory. Data acquired will be entered into the Centerâ€™s Access database after quality-assurance/quality-control protocols for data management. Second, a vertical-profiling acoustic Doppler current profiler (ADCP) will be installed at the Falls Lake Hwy. 50 site to assess the possibility of bi-directional flow between the upper and lower lake. This unit will replace the present ADCP at that site, which is capable of monitoring only a single horizontal point for velocity and direction. Third, we will continue ongoing renovation, calibration, and maintenance efforts on the three monitoring profilers installed in Falls Lake. The profilers were installed during 2004-2010 (water treatment plant intake-2004, Hwy. 50 - 2008, Falls Hwy. I85 - 2010), and are in need of constant maintenance to prevent damage to the equipment from recreational boaters who use the sites to tie up when fishing. The data acquired during this study will be provided to the Department of Public Utilities at the City of Raleigh, as part of our ongoing partnership.
Many streams, lakes, and reservoirs in North Carolina are adversely affected by excess nutrients (nitrogen, phosphorus) and organic carbon associated with algae and with deposition of fine sediment. These pollutants enter freshwaters through various point and nonpoint sources such as wastewater treatment plant and industrial plant effluents, storm-water runoff, landscape development, and agricultural activities. These excess nutrients lead to rapid eutrophication (nutrient over-enrichment) and subsequent adverse effects such as harmful algal blooms, reduced dissolved oxygen concentrations, less palatable drinking water for humans and livestock, and fish kills. Reducing nutrient and sediment influx to surface waters from all sources is important, and utilizing established best management practices such as improved effluent treatment technologies, vegetated buffers along streams and reservoirs, and storm-water retention ponds are all proven techniques. Another demonstrated influence on nutrient cycling and availability in aquatic systems is the natural functional role of ecosystem services provided by native freshwater mussels of the families Unionidae and Margaritiferidae. This project will provide urgently needed information on the nutrient (nitrogen, phosphorous, carbon) assimilative and cycling capacity of native freshwater mussels (Family Unionidae) under eutrophic conditions commonly encountered in surface waters of North Carolina; these mussel responses will be evaluated within an ecosystem services framework to assess potential effects on water quality.
This research will build from the foundation provided by a decadal dataset from the Center for Applied Aquatic Ecology on Falls Lake water quality, to assess the influences of documented high ammonium enrichment on phytoplankton assemblages and bloom dynamics. The research will consist of four components. First, decadal trends in ammonium concentrations and related parameters will be characterized, and relationships will be assessed among ammonium, other nutrients, phytoplankton biomass as chlorophyll a, and major phytoplankton groups. Second, dominant harmful algal species from phytoplankton samples freshly collected seasonally will be isolated and the clonal cultures will be examined for uptake and growth on ammonium versus nitrate, the two major inorganic nitrogen forms in Falls Lake. Third, seasonal microcosm experiments will be completed in the lake to assess the natural phytoplankton assemblage response to ammonium versus nitrate enrichment. In the fourth and final component, the findings will be considered collectively to inform a conceptual model describing how eutrophication, and specifically high ammonium, influences seasonal shifts in phytoplankton assemblage composition and harmful species abundance.