Benthic cyanobacterial accumulations and associated cyanotoxins in coastal urban stormwater pond networks

Extensive cyanobacteria-dominated mats were observed during late summer of 2021 within coastal urban stormwater retention pond networks in northwest Florida. Common in residential communities across the region, such ponds may be routinely visited by humans, domestic and wild animals, and often contain a variety of aquatic life. To begin examining correlations between environmental factors and mat characteristics, we investigated the temporal heterogeneity of these networks with regards to presence of potentially toxic cyanobacteria, associated toxins, and other putative cyanobacterial compounds throughout the fall at several sites within the networks. Multiple toxin classes were detected in whole water and passive SPATT samples using targeted analysis including levels of cylindrospermopsin that exceeded national recreational guidelines. Non-targeted analysis also revealed a collection of potential cyanobacteria-associated compounds. Our results suggest that the benthic proliferations may be, at least in part, correlated with the intended functions of the stormwater treatment networks, which are nutrient and sediment removal. Furthermore, these retention ponds may serve as an episodic source of cyanotoxins to estuarine waters.