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More Information about Harmful Algal Bloom Identification Tools
Background
Over the last four years, an unprecedented density and prevalence of harmful algal blooms (HABs) have been found in South Carolina brackish stormwater detention ponds, along with an anomalous raphidophyte bloom extending to coastal waters (Lewitus and Holland 2003, Lewitus et al., 2003; 2005). All of the observed HABs have potential for toxicity and causing fish kills, including Pfiesteria spp., Heterosigma akashiwo, Chattonella verruculosa, C. subsalsa, Fibrocapsa japonica, Prymnesium parvum, and Karlodinium micrum.
High HAB species abundances and dissolved oxygen concentrations were associated with 6 of 22 fish kills documented in SC brackish-to-marine waters in 2001-2002 (Lewitus et al., 2003). Evidence for HAB toxicity to fish was obtained in two of these six fish kills including a Pfiesteria-linked fish kill on Hilton Head Island and a K. micrum-associated kill in Charleston (Lewitus and Holland, 2003; Kempton et al., 2002). On other occasions, dense algal blooms (e.g., Chattonella spp., Kryptoperidinium spp.) were observed one day prior to fish kills that were associated with low levels of dissolved oxygen (Richardson et al., 2002; Lewitus et al., 2003). This finding suggests the possibility that algal blooms depleted oxygen from the water, leading to fish suffocation.
Five of the Chattonella or Fibrocapsa blooms were positive for brevetoxin or a brevetoxin-like substance using an ELISA screening assay. All of these species have precedence for causing major fish kills around the world, and brevetoxin can cause neurotoxic shellfish poisoning and human respiratory problems. In addition to their potential environmental and human health effects within or near pond boundaries, tidal transport of harmful algal cells, cysts, or toxins may adversely affect fish or shellfish in adjacent tidal creeks or open estuaries. For example, increased cell damage (as indicated by higher rates of destabilized lysosomes from oyster hepatic cells) were observed in oysters exposed to purified brevetoxin in the laboratory, and when exposed to field-collected water from raphidophyte blooms (Keppler et al., submitted). The blooms in these ponds, adjacent tidal creeks, and open estuaries are a potential threat to fish, shellfish, and humans.
Literature Cited
Jenny, M.J., A.H. Ringwood, E. Lacy, A.J. Lewitus, J.W. Kempton, R.W. Chapman, and G.W. Warr. 2002. Potential Indicators of Stress Response Identified by Expressed Sequence Tag Analysis of Hemocytes and Embryos from the American Oyster, Crassostrea virginica. Mar. Biotechnol. 4:81-93.
Kempton, J.W., A.J. Lewitus, J.R. Deeds, J. McH. Law, and A.R. Place. 2002. Toxicity of Karlodinium micrum (Dinophyceae) associated with a fish kill in a South Carolina brackish retention pond. Harmful Algae. 1(2):233-241.
Keppler, C.J., J. Hoguet, K. Smith, A.H. Ringwood,and A.J. Lewitus. 2004. Sublethal effects of the toxic alga Heterosigma akashiwo on the southeastern oyster (Crassostrea virginica). Harmful Algae, in press.
Keppler, C.J., A.H. Ringwood, T. Staton and J. Hoguet. (submitted). Sublethal cellular effects of a short-term brevetoxin exposure on the oyster, Crassostrea virginica. Toxicon.
Lewitus, A., Hayes, K., Kempton, J., Mason, L., Wilde, S., Williams, B. and Wolny, J. 2005. Prevalence of raphidophyte blooms in South Carolina brackish ponds associated with housing and golf courses. Proc. 10th International Conference on Harmful Algal Blooms (in press).
Lewitus, A.J. and A.F. Holland. 2003. Initial results from a multi-institutional collaboration to monitor harmful algal blooms in South Carolina. Environmental Monitoring and Assessment 81: 361-371.
Lewitus, A. J., L. B. Schmidt, L. J. Mason, J. W. Kempton, S. B. Wilde, J. L. Wolny, B. J. Williams, K. C. Hayes, S. N. Hymel, C. J. Keppler, A. H. Ringwood. 2003. Harmful algal blooms in South Carolina residential and golf course ponds. Population and Environment. 24 (5):387-413.
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Richardson, A.N. and A.J. Lewitus. 2002. The Ecology of Harmful Algal Blooms in a Brackish Subdivision Pond. Abstract at Southeastern Estuarine Research Society (SEERS) Fall Meeting, 17-19 October, 2002, Conway, SC.