Abstract
Sprawling blooms of K. brevis, the primary dinoflagellate responsible for red tides in the Gulf of Mexico, are known for their widespread fish kills and production of a suite of potent neurotoxins (i.e. brevetoxins). As evidence arises for increasing bloom intensity and longevity through time, questions about the fate of brevetoxins concurrently arise. While the scientific record of modern red tides is relatively short, the distributions and concentrations of chemical biomarkers (e.g., brevetoxins) in coastal-marine sediments can potentially be used to study historic red tides. This study aims to first quantify the vertical removal flux of brevetoxins in coastal Southwest Florida (SWFL) waters, and then study brevertoxins in sediment cores to determine their, persistence, transport and potential fates in marine environments. If blooms are increasing in intensity then elevated toxin concentrations within the water may lead to increased vertical flux and therefore higher sedimentary accumulation. This study also aims to better understand the concentration and vertical distribution of brevetoxins in coastal sediment cores in order to determine if downcore brevetoxins may potentially be used to reconstruct historic red tide events. Subsamples of sediments collected from both traps and cores at various locations in SWFL were analyzed utilizing liquid chromatography/triple quadrupole mass spectrometry (LC–MS/MS) for brevetoxin congeners, namely, PbTx-1, PbTx-2, PbTx-3, and PbTx-5. The subsamples of sediment cores were radiometrically dated using 210Pb-based sediment dating models to determine age of the sediments and historic records of associated brevetoxins. In this work, we demonstrate that peaks in brevetoxin concentrations in sediment traps coincide with active blooms. And sediment cores demonstrate that vertical fluxes of particle-bound brevetoxins lead to accumulation and long-term preservation of these lipophilic marine toxins within sediments.
