Karenia brevis (formerl
y Gymnodinium breve) is a toxic marine dinoflagellate generall
y restricted to the Gulf of Mexico and is the main causative organism in fish kills, shellfish intoxications and respirator
y distress in humans following bloom events.
K. mikimotoi is a morphologicall
y similar co-occurring species which is toxic in other parts of the world oceans, but has not been recognized as a major contributor in toxicit
y of blooms within the Gulf of Mexico. Recentl
y there has been increasing evidence of the simultaneous production of a variet
y of bioactive compounds in addition to potent neurotoxins (brevetoxin) in
Karenia brevis isolates. These compounds are potentiall
y ichth
yotoxic and have been shown to cause hemol
ysis in several bioassa
ys [Eshbach, E., Scharsack, J., John, U., Medlin, L., 2001. Improved er
ythroc
yte l
ysis assa
y in microtitre plates for the sensitive detection and efficient measurement of haemol
ytic compounds from ichth
yotoxic algae. J. Appl. Toxicol. 21, 513–519; Kirkpatrick, B., Fleming, L.E., Squicciarini, D., Backer, L.C., Clark, R., Abraham, W., Benson, J., Cheng, Y.S., Johnson, D., Pierce, R., Zaias, J.,
Bossart, G.D., Baden, D.G., 2004. Literature review of Florida red tide: implications for human health effects. Harmful Algae 3, 99–115]. Presence of hemol
ytic compounds ma
y therefore add to the overall toxicit
y levels of bloom events. Current monitoring methods include assa
ys which are highl
y sensitive in brevetoxin detection and
yet ma
y not target other harmful compounds.
By adapting protocols developed by Eshbach et al. [Eshbach, E., Scharsack, J., John, U., Medlin, L., 2001. Improved erythrocyte lysis assay in microtitre plates for the sensitive detection and efficient measurement of haemolytic compounds from ichthyotoxic algae. J. Appl. Toxicol. 21, 513–519], Red drum (Sciaenops ocellatus) erythrocytes were used to create a modified bioassay to detect hemolytic activity of crude algal extracts. Red drum was selected because it is endemic to coastal areas throughout the Gulf of Mexico and is sensitive to Karenia blooms, and thus makes this species a valid ecological target. Preliminary data has shown this method is sensitive for use in assessing hemolysis induced by laboratory cultures down to levels of 1 × 103 cells mL−1. Results showed an unexpectedly high level of hemolytic activity among K. mikimotoi clones, with one Texas strain inducing significantly higher hemolysis compared to Florida K. brevis isolates. Using this approach, future research efforts will examine the difference in production of hemolytic compounds among various Karenia clones.