title: ENVIRONMENTAL MODULATION OF KARLOTOXIN LEVELS IN STRAINS OF THE COSMOPOLITAN DINOFLAGELLATE, KARLODINIUM VENEFICUM (DINOPHYCEAE)(1).
abstract: We examined the influence of N or P depletion, alternate N- or P-sources, salinity, and temperature on karlotoxin (KmTx) production in strains of Karlodinium veneficum (D. Ballant.) J. Larsen, an ichthyotoxic dinoflagellate that shows a high degree of variability of toxicity in situ. The six strains examined represented KmTx 1 (CCMP 1974, MD 2) and KmTx 2 (CCMP 2064, CCMP 2283, MBM1) producers, and one strain that did not produce detectable karlotoxin under nutrient-replete growth conditions (MD 5). We hypothesized that growth-limiting conditions would result in higher cell quotas of karlotoxin. KmTx was present in toxic strains during all growth phases and increased in stationary and senescent phase cultures under low N or P, generally 2- to 5-fold but with some observations in the 10- to 15-fold range. No karlotoxin was observed under low-N or low-P conditions in the nontoxic strain MD 5. Nutrient-quality (NO3 , NH4 , urea, and glycerophosphate) did not affect growth rate, but growth on NH4 produced 2- to 3-fold higher cellular toxicity and a 50% higher ratio of KmTx 1-1:KmTx 1-3 in CCMP 1974. CCMP 1974 showed higher cellular toxicity at low salinity (≤5 ppt) and high temperature (25°C). Our results suggested that given the presence of a toxic strain of K. veneficum in situ, the existence of environmental conditions that favor cellular accumulation of karlotoxin is likely a significant factor underlying K. veneficum-related fish kills that require both high cell densities (10(4)  · mL(-1) ) and high cellular toxin quotas relative to those generally observed in nutrient-replete cultures.
authors.affiliation: University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Adolf
authors.affiliation: University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
authors.forename: Tsvetan R
authors.initials: TR
authors.lastname: Bachvaroff
authors.affiliation: University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA.
authors.forename: Allen R
authors.initials: AR
authors.lastname: Place
keywords: Karlodinium veneficum; harmful algal blooms (HABs); karlotoxin; nutrient control