Abstract

The inability of modern harmful algal bloom detection techniques to identify past K. brevis events has left the field without access to almost 300 years of historical data essential to the assessment of their apparent increase in frequency and intensity. As such, the marine sediments underlying K. brevis affected areas, and the final sink of the brevetoxins they produce when in bloom, represent the only means of establishing the spatial and temporal history of past occurrences.

In this work, a novel accelerated solvent extraction - solid phase microextraction method has been developed and optimized for the extraction and quantification of brevetoxins from marine sediments. Although the extraction method requires further optimization to improve its extraction efficiency and robustness, the method provides an effective means of recovering brevetoxins from most normal marine sediments, with total recoveries of spiked sediments as high as 62.0 ± 9.5% for brevetoxin-2 and 61.6 ± 6.5% for brevetoxin-3. The development of the method has allowed for several procedural pitfalls to be identified, including the potential presence of several contaminants and interferences detrimental to the precise and accurate quantification of brevetoxin using mass spectrometry. The most important among these limiting factors is the presence of high concentrations of co-extracted hydrophobic organic carbon, which affects the extraction efficiency of brevetoxins through the entrainment and sedimentation of extracted brevetoxins from the sediment extract by the formation of organic matter-rich flocculates. A strong relationship exists between organic carbon concentration and brevetoxin recoveries, which allows correcting for the effect of flocculation.