A persistent benthic Lyngbya wollei bloom in Lake Wateree SC: toxin, inventories, and fates.

The occurrence and spatial distribution of the persistent benthic filamentous algae Lyngbya wollei was determined for Lake Wateree, SC over the period of July 2018 - August 2019. A 16S rRNA gene sequence was recovered from a sample of collected algae to verify microscopic determination of the presence of Lyngbya wollei as the dominant algal species in grab samples from the bloom. Grab samples presented as fibrous masses and the organic carbon and ash contents were also determined for all samples taken. Samples exhibited a surprisingly high inorganic content at a mean 35% ash by gravimetric determination. The mass of inorganic material trapped in the fibers was applied as a correcting factor for grab sample biomass. Samples were lyophilized, extracted, and extracts were subjected to analysis by liquid chromatography-mass spectrometry (LCMS) for toxin determination, focusing on the neurotoxins Lyngbya wollei toxins (LWTs) 1-6. The LWTs 1, 4, 5, and 6 were observed in all locations sampled over the measured time period. Standard reference LWTs were unavailable; therefore, LWT 5 and LWT 6 were quantified against their structural analogue saxitoxin and normalized against organic carbon content. Based on the same standard LWTs 1 and 4 were present at much lower concentrations and are reported as qualified but not quantified. Samples were analyzed for spatial or temporal trends over the 13 month period. Algal occurrence maps and mean toxin concentrations were used to estimate an approximate total Lyngbya wollei toxin inventory for Lake Wateree. The cation exchange capacity of several Lake Wateree sediments was determined to evaluate the possibility of sedimentary LWT sinks.