When fishermen report strange episodes of memory loss associated with a bloom of the dinoflagellate Pfiesteria or there is an announcement of a new cancer-fighting drug isolated from a marine organism, the public becomes aware of the potential of the ocean both to threaten and benefit human health. Attention is then directed to the scientific experts to interpret these events and to make the appropriate policy recommendations. However, this requires an active research community that recognizes the links between human health and ocean processes and nurtures cooperative studies in fields as diverse as physical oceanography, public health, epidemiology, marine biology, and medicine. There is clearly a need for scientific exchange among these fields to ensure an integrated approach to issues where human health and ocean systems intersect. The workshop and this report on the Ocean's Role in Human Health were designed to initiate this type of interaction and provide guidelines for future programs.
In 1998, awareness of the dangers associated with marine driven weather events was heightened by the occurrence of an unusually strong El Niño which brought record rainfall and flooding to coastal communities. Because the majority of the world's population lives in coastal zones, the hazards associated with these events have an inordinate impact on public health. Coastal communities are especially vulnerable to storm surges, coastal flooding, and the outbreak of diseases that invade marine habitats. These natural disasters in turn stress the public health infrastructure that ensures safe drinking water, sewage treatment and disposal, and emergency medical care.
Another growing concern in the international community is the potential for global climate change due to alterations in atmospheric conditions from human activities such as the burning of fossil fuels and deforestation. Because the ocean acts as an immense reservoir for water, heat, and carbon (mineral and biogenic),
an understanding of ocean processes is essential for predicting climate change. Also, because the oceanic and atmospheric systems interact dynamically, there is concern that a change in atmospheric conditions due to global warming could modify the thermal-driven circulation of the world's ocean. This dynamic circulation is essential for replenishing seawater with nutrients and oxygen and represents one of the driving forces behind changing atmospheric conditions and weather. As demonstrated during the 1997–1998 El Niño, a change in the temperature of a body of water in the equatorial Pacific can have dramatic impacts on the climates of countries as far away as Africa and Asia.
However, why should the medical community be concerned with changes in climate and weather? Experts in infectious diseases warn that in concert with changes in temperature and rainfall, there will be a change in the distribution of both waterborne and vector-borne diseases (Colwell, 1996; Haines and Parry, 1993; Rogers and Packer, 1993). Disease organisms are sensitive to changes in their environments and can quickly spread into new areas when conditions become favorable for their survival or decrease or disappear when conditions become unfavorable. Add to this the increasing mobility of human society and the probability of dispersal of disease agents worldwide increases with increasing travel and commerce.
In the past, outbreaks of cholera have been traced to shipping activities (Colwell, 1996). Current research indicates that the bacterium responsible for causing cholera, Vibrio cholerae, can spread through attachment to marine organisms in ship ballast water. In addition, recent studies have linked some disease outbreaks to changes in marine conditions such as prolonged periods of elevated sea surface temperature (Colwell, 1996). Vibrio cholerae inhabits the guts of planktonic crustaceans, specifically copepods. In this milieu, the bacteria can become concentrated into a dose sufficient to cause cholera if only a few copepods contaminate ingested shellfish or drinking water. Therefore, conditions that favor the growth and reproduction of planktonic organisms may also favor the propagation of resident cholera pathogens.
The primary source of marine-borne illness in humans is ingestion of seafood contaminated with hepatitis and caliciviruses, and pathogenic bacteria including both indigenous marine vibrios and a variety of non-marine species from human and animal fecal contamination (IOM, 1991). Traditional methods for assessing bacterial and viral contamination are not always adequate for assessing the public health risk. The increasing demand for seafood in both industrialized and developing countries, compounded by the variety of waterborne pathogens, adds to the potential for outbreaks of disease, a threat that may be offset by vigilant public health surveillance.
Other public health threats associated with marine conditions include harmful algal blooms (HABs) which have increased in frequency and geographic range in the past two decades. HABs result in human health hazards caused by dead and dying fish, adulteration of food supplies by at least five different types of
toxic agents, and inhalation of these toxins when they become aerosols through wave action. Many of these toxins affect the nervous system and cause paralytic, diarrheic, neurotoxic, and amnesic shellfish poisoning, and ciguatera fish poisoning, with symptoms ranging from mild nausea to paralysis and death. As discussed in Marine Biotoxins and Harmful Algae: A National Plan 1992 (Anderson et al., 1993) and The Ecology and Oceanography of Harmful Algal Blooms: A National Research Agenda (ECOHAB, 1995), management of this problem will require research in biological oceanography to study how ocean processes affect the blooms and the distribution of different algal species, in biochemistry and molecular biology to identify algal toxins and the metabolic pathways affected by algal toxins for improved diagnosis and treatment, and in epidemiology and public health to document the association between outbreaks of illness and incidence of algal blooms, and to provide appropriate health warnings.
Scientists have investigated the algal toxins in order to understand the pathology of the illness listed above and to use these toxins as molecular probes of neural function. Many marine organisms have contributed to biomedicine through the unique molecules they produce. Other examples include bioluminescent and fluorescent indicator proteins, restriction enzymes used in molecular cloning, and novel antibiotics, anti-inflammatory agents, and anti-neoplastic drugs. Why do organisms produce these novel compounds that are incidentally valuable to humans? Similar to their terrestrial counterparts, marine organisms have evolved molecular strategies for evading disease and predation. Many of these strategies include the production of inhibitory chemicals that have biological activity in humans and may provide new therapies for a variety of diseases.
Finally, there has been a long tradition in the biological sciences of exploiting the properties of marine organisms as models for biomedical research. Through study of their unique adaptations to the marine environment, these organisms have contributed to our understanding of human biology from the most reductionist cellular process to the unraveling of the neural processes underlying behavior. Some of these discoveries have started new areas of investigation in cancer research, immunology, inflammatory joint diseases, kidney physiology, and neurochemistry to name a few prominent examples.
Clearly, we have benefitted greatly from our past studies of the ocean and marine life. However, challenges remain to develop more accurate forecasting of climate and weather, to assess the threat of the emergence and spread of infectious diseases, to anticipate changes in the growth and distribution of harmful algal species, and to explore marine biodiversity in order to uncover new pharmacologic agents and animal models for biomedical research.
Organization of the Report
This report evolved from the workshop on The Ocean's Role in Human Health, hosted by the National Research Council's Ocean Studies Board. In the
first part of the workshop, experts in physical oceanography, public health, infectious diseases and harmful algal blooms discussed areas in which the ocean presents risks to human health. In the second part, experts in marine pharamacology and marine biomedical models presented examples of how marine organisms have provided a source of new compounds for treating human disease and have led to discoveries of biological processes that underlie many human diseases. A complete description of the workshop appears in Appendix C, the general topics and speakers are listed below:
Following the workshop, the Committee on the Ocean's Role in Human Health met and discussed the major findings presented and outlined conclusions based
on these findings. The committee structured the report using the same organization as the workshop. Hence the five sessions of the workshop correspond to Chapters 1, 2, 3, 4, and 5 of this report. Because each chapter addresses a discrete topic, conclusions are presented at the end of each chapter. Finally, this report is meant to serve as an overview, not a comprehensive discussion of all the possible connections between human health and the oceans. For this reason, health hazards such as shark bites and jellyfish stings and the secondary effects of pollution and changes in ocean-based food resources were not included in the scope of the study.