Burkholder has been a key figure in advancing scientific understanding of
harmful algal blooms (HABs) as ecological phenomena linked to nutrient enrichment. In the same period, Burkholder co‑authored
Harmful algal blooms and eutrophication: Examining linkages from selected coastal regions of the United States, which documented specific case studies linking nutrient loads to toxic and harmful blooms in
U.S. coastal waters and highlighted regional differences in bloom responses to
eutrophication. Her broad engagement with HAB science extended into editorial leadership as co‑editor (with Sandra E. Shumway and Steven L. Morton) of
Harmful Algal Blooms: A Compendium Desk Reference, a comprehensive volume addressing causes, impacts, detection,
mitigation, and management strategies for HAB species worldwide. Contributions in this reference covered nutrient influences on harmful species such as
Prymnesium parvum,
cyanobacteria,
dinoflagellates, and others, and included sections she co‑authored on
Pfiesteria ecology,
Prorocentrum physiology, and macroalgal blooms.
Dinoflagellates, Pfiesteria, and Toxin Dynamics Burkholder is widely recognized for her research on the toxigenic
dinoflagellates Pfiesteria piscicida and
Pfiesteria shumwayae and their role in harmful fish kills in nutrient‑enriched estuaries. Her laboratory’s work demonstrated that
toxicity is strain‑specific, with some populations capable of producing potent ichthyotoxins while others are not, and that proper assessment of toxicity depends critically on experimental methods and test organisms. Beyond
Pfiesteria, Burkholder’s work on harmful
dinoflagellate ecology included research on interactions between toxic species and ecologically important
bivalve molluscs, demonstrating effects on survival, grazing, and behavioral responses relevant to
ecosystem food webs. She also co‑authored studies on growth and developmental responses of
Pfiesteria under different conditions and on strategies to cultivate
heterotrophic dinoflagellates under axenic conditions to better observe feeding behavior and toxicity expression.
Seagrasses and Eutrophication Burkholder, alongside David A. Tomasko and Brant W. Touchette, summarized historical and experimental evidence demonstrating that cultural eutrophication is a major driver of
seagrass decline. Their research showed that nutrient enrichment reduces light availability through stimulation of epiphytic algae and macroalgae and identified direct physiological effects of nitrate and ammonium on seagrasses (
Zostera marina).
Pfiesteria Research Burkholder is widely known for her discovery and characterization of
Pfiesteria piscicida and
Pfiesteria shumwayae,
toxigenic dinoflagellates responsible for
fish kills in nutrient-enriched estuaries of the southeastern United States. She demonstrated that toxicity is strain-specific, with populations ranging from non-toxic to highly toxic, and showed that toxic strains attach to fish tissues, feed on cells, and release soluble toxins capable of killing fish without direct contact . The chemical characterization of Pfiesteria toxins by Moeller and colleagues, recognized by
NOAA, provided definitive evidence of biologically active compounds responsible for ichthyotoxicity. International studies, including Moestrup et al. (2014), confirmed that
Pfiesteria can cause fish kills in aquaculture settings, corroborating Burkholder’s findings. Bioassay sensitivity was shown to depend on fish species, with Oreochromis spp. (Tilapia) more susceptible to Pfiesteria toxins than
Cyprinodon variegatus (
sheepshead minnow).
Freshwater Ecosystems Burkholder’s studies in freshwater reservoirs and streams included documenting cryptic dinoflagellates under episodic sediment loadings, quantifying interactions between nutrient and sediment concentrations in promoting algal blooms, and assessing cyanotoxin prevalence in potable water supplies . == Public Engagement and Environmental Education ==