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Tank Experiment to Quantify Fate of Microcystin in Shallow Coastal Sediments | Ohio Sea Grant

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Tank Experiment to Quantify Fate of Microcystin in Shallow Coastal Sediments

OHSU-TD-1508: Tank Experiment to Quantify Fate of Microcystin in Shallow Coastal Sediments

Published: Jan 1, 2016
Last Modified: Apr 29, 2016
Length: 38 pages
Direct: Permalink

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Abstract

Harmful algal blooms (HABs) have become more prevalent within Lake Erie since the mid-
1990s. Microcystin is one of the most common and harmful toxins associated with HABs, yet
little is known about its attenuation and fate in the environment. Microcystin is a cyclic
heptapeptide with 2 variable L-amino acids, which differentiate between the over 60 variants of
microcystin known. Variants have differing toxicity profiles, the most toxic being microcystin-
LR, which contains leucine (L) and arginine ® amino acids. The goal of this thesis research
was to determine whether wave-driven benthic exchange accelerates the attenuation of
microcystin in shallow coastal waters using laboratory wave tank experiments. Sediment was
collected from Western Lake Erie and incorporated into a 110-gallon tank. A solution consisting
of both a conservative chloride tracer and microcystin-LR stock dissolved in water was added to
surface water at the start of both a Wave Trial and a Non-Wave Trial, and concentrations were
monitored over time in surface water and shallow pore water. Results show that wave conditions
had a significant impact on exchange rates of conservative chloride, mixing the system over 30
times faster than stagnant conditions. Microcystin concentration in surface water and pore water
decreased faster than chloride, likely due to sorption to sediments, degradation, or both. It is
crucial to better understand microcystin attenuation and mechanisms responsible in order to
accurately predict the severity, duration, and extent of algal toxin plumes, which negatively
affect the health of coastal ecosystems and economies.