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Marine Animal Health
Overview
The health of coastal ecosystems is reflected in the health of the marine animals inhabiting those systems. At HML, researchers concentrate specifically on the development of diagnostic tools and the epidemiology, or the study of the factors that affect health and disease of populations, for sentinel species which are most likely to be sensitive indicators of emerging stressors in marine ecosystems. Species such as the bottlenose dolphin, corals, shrimp, blue crabs and key fish species are studied at HML. Understanding the health of these sentinel species and how it is changing in relation to an altering coastal environment can help predict how the condition of the oceans, and more specifically our coast waters, may affect marine ecosystems, which include people, now and in the future.
Bottlenose Dolphins
Bottlenose dolphins (Tursiops truncatus) are found in estuaries and nearshore waters along the entire southeast
U.S. coast where they are exposed to environmental stressors such as chemical pollutants, disease-causing pathogens
and harmful algal toxins. Many of the chemical pollutants in coastal waters are biomagnified as they move up the
food chain. Therefore, as top-level predators, dolphins are exposed to high levels of these pollutants continuously
throughout their life. Dolphins, like humans, are mammals and they swim in the same coastal waters as humans,
breath the same air and are exposed to a number of marine pathogens that are potentially transmissible to humans.
For these reasons, dolphins may serve as effective sentinels for human health concerns in many coastal regions.
Other important sentinel species under study include the California sea lion which is distributed along the U.S.
Pacific coast, and filter-feeding oysters which are sensitive indicators of pollution and other stressors in
sentinel habitats such as subtidal and intertidal estuarine creeks along the U.S. Atlantic coast. HML conducts
work with bottlenose dolphins and related species as part of NOAA’s Cooperative Center for Marine Animal Health. Learn more about the cooperative center for marine animal health »
Oysters
The oyster lives in coastal waters that have highly variable water quality (e.g., low dissolved oxygen, high pH)
and substantial pollutant loadings (e.g., metal and organic pollutants). Like other filter-feeding bivalves,
oysters harbor and concentrate pathogens that occur in their marine habitat and transfer them to humans when the
oysters are eaten. Laboratory findings suggest that water quality factors such as pH and O2 levels,
as well as concentration of metal and organic pollutants, can impact the ability of oysters to inactivate human
pathogens within the tissues of the animal. This OHH project has yielded a monitoring assay that quantifies the
persistence and degradation of live bacterial pathogens in the eastern oyster, Crassostrea virginica, as well as
externalization of live bacteria from the oyster to the environment. Stressors such as low oxygen (hypoxia),
chronic low-level cadmium and seasonal variation alter the persistence of tissue bacteria in the oyster. Learn more about oysters »
Crustaceans
Scientists often want to know what kinds of effects a particular environmental variable has on an organism.
Organisms can be taken into the laboratory to study the effects of individual variables. But how can the laboratory
responses be translated into responses of organisms in the field where they are exposed to more than one stressful
environmental variable such as low oxygen, fluctuating salinity, wide ranges of temperatures, parasites and
bacterial and viral infections? Working with low oxygen and bacterial infections of marine organisms has led us to
develop a challenge model where we have begun measuring the performance of organisms under controlled conditions.
A shrimp encountering a bacterial infection has mechanisms to fight this infection, but like humans fighting an
infection, the shrimp may not be as physically fit.
In response to the movement of the belt of a treadmill submerged in water, shrimp will walk at slow treadmill
speeds and swim at higher speeds. We have used this treadmill system to stimulate shrimp to high levels of activity
after they have been injected with a dose of a common shrimp bacterial pathogen, Vibrio campbellii. We have begun
measuring a variety of physiological variables as the shrimp respond to this bacterial challenge. Our early studies
indicate that the shrimp are severely stressed by bacterial injection and, while they are able to completely eliminate
the injected bacteria, their performance suffers.
Crustaceans in the natural environment encounter both bacterial and viral challenges and we suggest that they are
less fit to engage in higher levels of activity (prey capture, predator avoidance) and they are less able to tolerate
low levels of ambient oxygen.Learn more about crustaceans »
Corals
The Coral Disease and Health Consortium (CDHC) provides the framework for a network of federal, university,
non-profit and industry scientists and managers with diverse expertise to provide information needed to understand
the nature of coral disease, what causes it and how it spreads; thereby providing critical information and diagnostic
tools for early detection of pending disease outbreaks and allowing resource managers the opportunity to take corrective
measures proactively. The CDHC works to determine the cause of declines in coral reef health (diseases, bleaching,
mortalities, abiotic factors and human stressors), define exposure-response threshold values and provide technical
information and assistance to managers and scientists regarding the condition of coral reefs and possible causes and
remedies.
HML scientists, for their contribution to CDHC, are developing research tools in the form of innovative biomolecular
technologies and clinical pathology to investigate host and symbiont defense mechanisms, disease etiologies and
transmission, the influence of anthropogenic factors as well as contemporary risk analysis and modeling for predicting
disease outbreaks and epizootics.Learn more about corals »