Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA |
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Authors: | Christopher J Gobler Dianna L Berry O Roger Anderson Amanda Burson Florian Koch Brooke S Rodgers Lindsay K Moore Jennifer A Goleski Bassem Allam Paul Bowser Yingzhong Tang Robert Nuzzi |
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Institution: | aSchool of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA;bBiology, Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, USA;cAquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University Ithaca, NY 14853-6401, USA;dSuffolk County Department of Health Services, Office of Ecology, Yapank, NY 11980, USA |
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Abstract: | We report on the emergence of Cochlodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Bay, NY, USA, during 2002–2006. Blooms occurred during late summer when temperatures and salinities ranged from 20 to 25 °C and 22 to 30 ppt, respectively. Bloom patches achieved cell densities exceeding 105 ml−1 and chlorophyll a levels exceeding 100 μg l−1, while background bloom densities were typically 103–104 cells ml−1. Light, scanning electron and ultrathin-section transmission electron microscopy suggested that cells isolated from blooms displayed characteristics of C. polykrikoides and provide the first clear documentation of the fine structure for this species. Sequencing of a hypervariable region of the large subunit rDNA confirmed this finding, displaying 100% similarity to other North American C. polykrikoides strains, but a lower similarity to strains from Southeast Asia (88–90%). Bioassay experiments demonstrated that 24 h exposure to bloom waters (>5 × 104 cells ml−1) killed 100% of multiple fish species (1-week-old Cyprinodon variegates, adult Fundulus majalis, adult Menidia menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation of the gills of moribund fish revealed epithelial proliferation with focal areas of fusion of gill lamellae, suggesting impairment of gill function (e.g. respiration, nitrogen excretion, ion balance). Lower fish mortality was observed at intermediate C. polykrikoides densities (103–104 cells ml−1), while fish survived for 48 h at cell densities below 1 × 103 cells ml−1. The inability of frozen and thawed-, or filtered (0.2 μm)-bloom water to cause fish mortality suggested that the thick polysaccharide layer associated with cell membranes and/or a toxin principle within this layer may be responsible for fish mortality. Juvenile bay scallops (Argopecten irradians) and American oysters (Crassostrea virginica) experienced elevated mortality compared to control treatments during a 9-day exposure to bloom water (5 × 104 cells ml−1). Surviving scallops exposed to bloom water also experienced significantly reduced growth rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation, and apoptosis in gill and digestive tissues with gill inflammation specifically associated with areas containing C. polykrikoides cells. In summary, our results indicate C. polykrikoides blooms have become annual events on eastern Long Island and that bloom waters are capable of causing rapid mortality in multiple species of finfish and shellfish. |
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Keywords: | Cochlodinium Fish kill Harmful algal blooms Histopathology Long Island Peconic Estuary Polysaccharides Red tide Shellfish TEM and SEM fine structure Toxicity |
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