Probabilistic ecological hazard assessment of microcystin-LR allelopathy to Prymnesium parvum
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abstract
The harmful algal species Prymnesium parvum, a toxin-producing mixotrophic haptophyte, has caused massive fish kills in select inland Texas water bodies. Though P. parvum is present in a number of water bodies and Gulf of Mexico estuaries, it does not develop harmful blooms in all of them. A previous study by our team identified dissolved constituents from a cyanobacterial-dominated lake to exhibit concentration-dependent growth inhibition of P. parvum. Here we employed a probabilistic ecological risk assessment approach to examine the potential allelopathy of the cyanotoxin microcystin-LR (MC-LR) to P. parvum under laboratory conditions representative of Texas water bodies when blooms form. An environmental exposure distribution was constructed utilizing MC-LR concentrations detected in the environment and compared with experimental acute median lethal values reported in the literature. In a laboratory experiment, P. parvum cells were grown in media containing different MC-LR concentrations and cell density was determined daily. A concentration of 4392.8 g L -1 significantly inhibited P. parvum growth over a portion of the study. Such a concentration was predicted to be detected or exceeded 9% of the time when microcystin producers are likely to occur. However, when a concentration this high occurs in the environment to affect P. parvum growth, a number of aquatic organisms may be expected to experience acute mortality from MC-LR. Further studies are warranted to define the effects of other compounds released by cyanobacteria on P. parvum populations. The Author 2010.
