Salt marsh ponds (SMPs) are small (one to 10’s of meters in diameter) isolated pools that form a vital component of New Jersey (NJ) coastal wetlands. They provide unique microhabitats for diverse aquatic organisms, including algae, snails, fish, crustacea, and insects, and year-round food supplies for shorebirds, wading birds, and dabbling ducks. While salt marshes in the eastern US provide natural barriers from storms and waves, they have been extensively altered by marsh management practices for mosquito control, especially parallel grid ditching (PGD) and open marsh water management (OMWM). Over 90% of the coastal wetlands from Maine to Virginia and 94% along New England have experienced ditching. The number of SMPs and their areal coverage has been increasing due to anthropogenic modifications and the frequent storms and flooding associated with climate change and sea level rise. 

We hypothesized that the tidal SMPs, forming unique microhabitats, can potentially function as Harmful Algal Bloom (HAB) reservoirs and sources for NJ coastal waters. Our study area, the Sheepshead Meadow Peninsula is a marsh platform located within the Jacques Cousteau National Estuarine Research Reserve (JC NERR) (map of study area). Its northwestern part was ditched through PGD in the 1920s, and the central area was modified through OMWM from the 1960s to 1990s. The southern part of the peninsula, however, remains one of the largest unaltered salt marshes in NJ. As a NOAA designated sentinel site, the JC NERR has been well studied for habitat types and patterns, vegetation composition, and fish communities in SMPs. However, little is known about the algal communities, and the presence of HAB species has not been previously studied in the SMPs. 

To test our hypothesis, the microalgal assemblages were investigated in SMPs at the JC NERR in three types of marshes: OMWM, PGD, and unaltered between May 2022 and June 2023. The investigation consisted of monthly water parameter measurements and collections of algal samples. The algal samples were examined through microscopy and DNA analysis in a first effort to investigate the presence of HABs in the Sheepshead Meadow Peninsula SMPs.

The detected HAB species cover several taxonomic classes, including dinoflagellates Amphidinium carterae, Gymnodinium aureolum, Prorocentrum lima and Alexandrium sp., raphidophytes Chattonella subsalsa and Heterosigma akashiwo, haptophyte Prymnesium parvum, and cyanobacteria Planktothrix agardhii, Lyngbya aestuarii. In many cases, the HABs accounted for > 60% to 98% of total algal abundance, and cell density reached as high as 103 to 104 cell/mL for dinoflagellates and 105 cells/mL for Prymnesium parvum. A follow-up study, using Enzyme-linked Immunosorbent Assay (ELISA), detected five types of algal toxins, including brevetoxin, saxitoxin, okadaic acid, microsytins, and cylindrospermopsins in the SMPs.

Project Funding
Contract SR22-014 between New Jersey Department of Environmental Protection (NJDEP) and George Mason Univeristy (GMU) was funded by EPA Wetland Program Development Grant. Grant #: CD 96246800-0.