Journal
AQUATIC MICROBIAL ECOLOGY
Volume 46, Issue 2, Pages 125-140Publisher
INTER-RESEARCH
DOI: 10.3354/ame046125
Keywords
harmful algal bloom; HAB; management; mitigation; immigration; barley straw; extract
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Large fish kills associated with toxic populations of the haptophyte Prymnesium parvum occur worldwide. In the past 5 yr, incidences of P. parvum blooms in inland water bodies of Texas (USA) have increased dramatically, where cell densities in excess of 1 x 10(7) cells l(-1) are typically observed. We conducted field experiments (Lake Possum Kingdom) during the fall and early spring of 28 d duration using 24 enclosures of 1.57 m(3) each. The experiments investigated the effect of nutrient enrichment, immigration of F parvum and addition of barley straw extract on phytoplankton biomass and assemblage structure, P. parvum population density, zooplankton biomass and assemblage structure, bacteria, and toxicity. Nutrient enrichment stimulated P. parvum population growth beyond bloom proportions (> 1 x 10(7) cells l(-1)). However, P. parvum did not dominate the assemblage under these conditions, as it does during natural blooms. Instead, euglenophytes and chlorophytes dominated. Toxicity, estimated using fish (Pimephales promelas) and cladoceran (Daphnia magna) bioassays and which is linked to P. parvum's allelopathic and mixotrophic effectiveness, was greatly reduced (eliminated in many cases) under conditions of nutrient enrichment. The suppression of toxicity by nutrient addition suggested that targeted and time-limited nutrient manipulations might be used to mitigate the effects of R parvum blooms. Immigration of R parvum into natural assemblages and addition of barley straw extract had no significant effect on plankton dynamics.
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