The Functional Mechanism for Fish Kills By the Harmful Algae Species Chattonella subsalsa

Harmful algae blooms (HAB) and toxins associated with HAB species represent a significant threat to the health of marine species and coastal environments. Excessive land treatment and increased impervious surfaces in the rapidly urbanizing South Carolina coastal zone have intensified anthropogenic eutrophication in coastal waters, causing a proliferation of HABs.  The raphidophyte species Chattonella subsalsa is one of the most prominent causative agents for algal bloom fish kills in South Carolina estuaries. Though C. subsalsa is a known ichthyotoxic alga, the lethal mechanism of this species remains unidentified.  C. subsalsa is likely to elicit fish mortality via one of two mechanisms:  1) physical irritation and/or damage to the gills causing copious production of mucus and clogging of the gill filaments, or 2) the production of a bioactive compound or toxin. We hypothesized that fish mortality from C. subsalsa blooms is due to the degradation of gill tissue via clogging or bioactive compound or toxin. Larvae of Fundulus heteroclitus were exposed to C. subsalsa both directly and indirectly (through a 0.2 μm mesh) for 48 hours.  Fish mortality rates and histological examination of gill tissue were examined to compare the effects of C. subsalsa exposures.