Monitoring Harmful Algal Blooms in a Coastal System to Identify the Factors that Affect HAB Production and the Downstream Transport of Cyanobacteria and Associated Cyanotoxins from Freshwater to Marine Environments

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By New Jersey Water Science Center May 15, 2023

Across the nation, Ccyanobacterial harmful algal blooms (HABs) in freshwater coastal lakes and ponds have become a major environmental and public health concern. Under the right conditions, cyanobacteria can produce cyanotoxins that can pose health risks to both animals and humans (U.S. Environmental Protection Agency (USEPA), 2020) and have been shown to have severe impacts on water quality, aquatic ecosystem health, and the safe recreational uses of water resources.

Two scientists in wide brimmed hats and floatation vests holding buoy for deployment — Scientists Brad Bjorklund and Erika Bernal prepare to deploy continuous water-quality sensors at Deal Lake, NJ.

Exposure to cyanobacterial toxins, such as Anatoxin-a Microcystins, Cylindrospermopsins, Nodularins, and Saxitoxins, through ingestion, inhalation of aerosolized toxins, consumption of contaminated seafood and dermal contact has the potential to produce a wide range of symptoms in humans, including liver failure, respiratory arrest and, in rare cases, death (Turner et al. 1990; Stewart et al. 2006, USEPA, 2020). Recent studies have shown that cyanobacteria and associated cyanotoxins in coastal freshwater lakes can be transported to the marine environment (Gibble et al., 2016; Preece et al., 2017; Paerl et al., 2018; Buckaveckas et al., 2018; Bormans et al., 2019). Preece et al. (2017) recently reviewed studies of cyanotoxin transport in rivers to nearshore marine waters and highlighted the growing body of evidence demonstrating that microcystins and other cyanotoxins can persist during transport and accumulate in these saline environments. Of major concern is the potential impact of elevated cyanotoxin concentrations in these nearshore water environments for dermal exposure during recreational contact and aquatic life impairments, such as accumulation in shellfish, which can cause poisoning via consumption (Bukaveckas et al 2018; Miller et al 2010). Stakeholders such as fisheries, regulatory agencies, and estuary programs have expressed concern over the occurrence and potential risks freshwater cyanotoxins pose to the health of coastal systems.

Coastal lakes play a significant role in New Jersey’s marine ecosystems. As with inland waterbodies, coastal lakes and impoundments can suffer from the effects of over development, stormwater runoff, pollution, and high nutrient inputs that can stimulate the overgrowth of algae and cyanobacteria. Deal Lake is a man-made lake in Monmouth County, NJ that was created by impounding outflows to the Atlantic Ocean at the shore of Asbury Park, NJ in the 1890s. At approximately 158 acres, it is the largest coastal lake in New Jersey and has a rich history of recreational fishing and boating. Deal Lake is fed by seven major tributaries including (from north to south) Hollow Brook, Seaview Brook, Harvey Brook (once known as Hog Swamp Brook), and four unnamed streams

USGS Scientists in float vests climbing on rocks of jetty collecting samples of algae — USGS scientists climb on boulders of the jetty at Asbury Park to collect blue mussels (*Mytilus edulis*) and biological measurements from the Atlantic Ocean for analysis of cyanotoxins in mussel tissue.

Deal Lake discharges to Atlantic Ocean beaches through a sluice gate. Lake levels are controlled by a flume structure on the shore side that has been modified several times since the original construction. In the past, the lake experienced significant inflows from the Atlantic Ocean allowing saltwater species such as herring to spawn in the freshwater areas of the coastal lake system. Lake levels are highly regulated by the New Jersey Department of Environmental Protection (NJDEP) with outflows during summer months and spawning seasons allowed only for flood control during heavy storm events. When the flume gates are opened there can be a significant exchange of fresh and saline waters between the ocean and Deal Lake (Deal Lake Commission, 2022).

Most of the region surrounding the lake is highly urbanized and is heavily dominated by both residential and commercial structures that were constructed during the 20^th century (Princeton Hydro, LLC, 2011). Poor stormwater management over this period, including direct inputs from combined sewer overflows until the 1950s, has resulted in heavy pollution of the lake and surrounding tributaries (Princeton Hydro, LLC, 2011). The degradation in water-quality prompted the creation of the Deal Lake Commission (DLC) in 1974 to restore and preserve the lake and regulate flow through the flume house. A 2008 report compiled by Princeton Hydro, LLC. in support of the DLC Watershed Protection Plan, found that the within the watershed, Deal Lake acts as the sole means of passive pollutant removal prior to discharge to the ocean (Princeton Hydro, LLc, 2011). The degradation in the water quality of Deal Lake over time has included elevated levels of several non-point source (NPS) pollutants such as phosphorus, nitrogen, sediment, fecal coliform bacteria and floatables (Princeton Hydro, LLc, 2011).

Sunset Lake, which empties into Deal Lake on the southernmost boundary, has been assigned both the HAB watch and advisory tiers by the NJDEP with a confirmed presence of cyanobacterial toxins (The NJDEP HAB Interactive Map Reporting and Communication System). Nutrient monitoring by Monmouth University, in cooperation with NJDEP and U.S. Environmental Protection Agency (USEPA) for the Coastal Lake Program, is routinely performed within Deal Lake and Sunset Lake (Coastal Lakes Observing Network (CLONet) sites). Weekly samples are collected at sites from April through October and biweekly from November through March. The data have shown “dramatically increased nutrient concentrations at certain locations that may contribute to the production of harmful algal blooms within the lake” (oral communication from Jason Adolf, 1/6/2022).

The main objectives of the study are to:

Two scientists in a lab examining different sized mussel shells. — Scientists Kathryn Cahalane and Lucas Sirotniak sort blue mussels (*Mytilus edulis*) from the Atlantic Ocean for the analysis of cyanotoxins in mussel tissue.

Assess the potential transport of cyanobacteria and cyanotoxins from a freshwater coastal lake to the marine environment.
Assess water-quality conditions that contribute to HAB production and subsequent production of associated cyanotoxins:
1. Monitor nutrients and cyanotoxin occurrence in discrete water quality samples and physiochemical parameters that serve as surrogates for biological activity to assess conditions that may contribute to production and persistence of HABs and associated cyanotoxins.
2. Continuously monitor physiochemical parameters and biological activity at collocated Monmouth University/NJDEP Coastal Lakes Observing Network (CLONet) sites on open water to help identify drivers of HABs in saline lake environments.
Evaluate low-cost passive, time-integrated Solid Phase Adsorption Toxin Tracking (SPATT) samplers to capture cyanotoxin occurrence during ephemeral events and transfers from freshwater to marine environments, which can be missed by traditional approaches.
Collaborate with state and academic partners to assess cyanotoxin occurrence (Saxitoxin) in shellfish near the lake outfall.