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GLOBAL CLIMATE AND LARGE-SCALE INFLUENCES ON AQUATIC ANIMAL HEALTH
Citation:
GLOBAL CLIMATE AND LARGE-SCALE INFLUENCES ON AQUATIC ANIMAL HEALTH. Presented at International Symposium on Aquatic Animal Health, New Orleans, LA, Sep 1-5, 2002.
Description:
The last 3 decades have witnessed numerous large-scale mortality events of aquatic organisms in North America. Affected species range from ecologically-important sea urchins to commercially-valuable American lobsters and protected marine mammals. Short-term forensic investigations of these events have sometimes characterized a causative agent or condition, but have rarely provided sufficient insight to predict and manage animal health. Traditionally, we apply the tools of microbiology, parasitology and pathology to investigate causality. More recently, satellite imagery and remote sensing have provided physical information on broad
temporal and spatial scales that can be compared with local biological phenomena. These tools provide a means to develop epizootiological models that include large-scale influences, such as global climate and land use change, on aquatic diseases. A prime example is worldwide bleaching of corals in relation to water temperatures driven by El Nino-Southern Oscillation (ENSO) conditions. Bleaching can be exacerbated by increased exposure of corals to ultraviolet light, a situation that is linked to loss of stratospheric ozone and local doldrum conditions that sometimes accompany ENSO. Another example is a sea fan coral disease
stemming from the long-range transport of a nonindigenous fungal pathogen; it's transport is linked to increased global dust and easterly trade winds coincident with decadal variability in the North Atlantic Oscillation. Transport of essential nutrients, particularly iron, under this same scenario has been hypothesized to account for the increased number and severity of coral diseases in the Caribbean and to indirectly affect red tide blooms in the Gulf of Mexico. Sea-level rise, a large-scale change that is predicted to vary with location, will affect temperature, salinity and estuarine flushing. Health consequences for coastal organisms, such as the economically-important eastern oyster, can be expected. Oyster population success is dependent on fluctuating estuarine salinity and temperature and their population dynamic is heavily influenced by a salinity-and temperature-dependent protozoan disease. Local land use decisions, although sometimes seemingly inconsequential, accumulate into watershed land-use patterns that can greatly influence the quality of coastal waters. Elevated nutrients from watershed effluent are suspected in increased hypoxia in the Gulf of Mexico, as well as the increase in the number and severity of harmful algal blooms across North America. Toxic algae
have been implicated not only in frequent fish and shellfish mortalities, but in bivalve neoplasia and sea turtle fibropapillomatosis diseases. Regional observing systems that employ satellite imagery and real-time remote sensors are being developed to forecast conditions conducive to blooms of harmful algae. Our investigation of existing and emergent diseases will be greatly enhanced by tools that provide additional information on large-scale factors. However, these tools are still being applied on a retroactive, case-by-case basis. The greatest benefits will accrue when large-scale physical trends can be applied to predict health risks to multiple
species.