Determination of brevetoxin in recent marine sediments

Abstract

Harmful algal blooms (HAB) of Karenia brevis (K. brevis) produce a suite of lipid soluble polyether brevetoxins, known to cause environmental, health and economic ill effects. There is evidence that K. brevis has increased in abundance over the past 50 years, but the dataset is incomplete. The objective of this paper was to analyze sediment from an area where K. brevis blooms have occurred and investigate if these compounds are incorporated into the underlying sediment, thus potentially allowing the use of brevetoxins as an indicator of past K. Brevis blooms. The results from LC-ESI-MS-MS analyses of brevetoxin analogs detected in surficial sediments from three sites (Fort Meyers Beach [FMB], Big Hickory Pass [BHP] and Big Carlos Pass [BCP]) along the Southwest Florida coastline with prior HAB history are promising. The analogs detected from BHP sediments were PbTx-2 and PbTx-3 with values of 0.81 and 3.1 ng g(-1) dry sediment, respectively. The detected PbTx-2 from BCP was 3.6 ng g(-1) dry sediment, while the detected PbTx-3 from BCP was 9.7 ng g(-1) dry sediment. PbTx-3 was only detected at the FMB site (2.7 ng g(-1) dry sediment). The detection of brevetoxins in recent sediments where K. brevis have occurred indicates brevetoxin incorporation into marine sediments.

Fig. 1

Structures of the two types of brevetoxin and their respective analogs.

Fig. 2

Sources of sediment samples from the southwest coast of Florida were at (1) Fort Myers Beach (FMB), (2) Big Carlos Pass (BCP), and (4) Big Hickory Pass (BHP).

Fig. 3

Percentage of PbTx-9 recovered after brevetoxin was spiked into BHP sediment. Sonication times employed were 5, 10 and 30 min (n = 2).

Fig. 4

Reconstructed ion chromatograms of PbTx-2 and PbTx-3 from HPLC-ESI-MS-MS analysis of sediments and cultured cells. The instrument conditions are detailed in Section 2.