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Dr. Colwell's Remarks


"Oceans and Human Health: A Symbiotic Relationship Between People and the Sea"

Dr. Rita R. Colwell
National Science Foundation
Special Session on "Oceans and Human Health"
American Society of Limnology and Oceanography and The Oceanography Society
2004 Ocean Research Conference
Honolulu, Hawaii

February 16, 2004

See also slide presentation.

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The Office of Legislative and Public Affairs: (703) 292-8070.

[Title slide: Oceans and Human Health]
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Thank you, Sunny,1 for your invitation and introduction. I am delighted to discuss a subject that is of personal interest to me: oceans and human health.

In 1833, Edward Forbes, considered by many to be the founder of oceanography, was convinced that life could not exist in the freezing, crushing depths of the deep sea. Forty years later, scientists aboard the HMS Challenger found an abundance of life on the floor of the major oceans, at depths they were able to sample. Yet, they still predicted "dead" zones at middle depths, and believed the deepest trenches were azoic, or devoid of life.

In keeping with the nature of scientists, these hypotheses were accepted as challenges, rather than obstacles. As a graduate student, I was intrigued with the notion of life in the deepest parts of the ocean. I seized the opportunity to include the oceans in my research plans, and, as a young professor at the University of Maryland, collaborated with scientists at the National Bureau of Standards (now NIST) to develop a deep ocean microbiological sampler.

I went on to study the natural populations of bacteria in deep sea sediments and in the gut of deep sea amphipods. Because the readily cultured bacteria from these samples were frequently Vibrios, I was able to hypothesize and prove that Vibrio cholerae, the causative agent of cholera, is a marine bacterium.

How far we've come--from primitive studies of mollusks and fish to recognition of the ocean as a cradle of life and death, a conduit for health and disease, and a major player in the earth's environmental processes.

[Slide not available]
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The naturalist John Muir said, "When we try to pick out anything by itself, we find it hitched to everything else in the Universe."

From the complex chemistry that spawned life on Earth to the many thousands of lives lost in surging seas, human fate has been hitched to the oceans. More than a century of ocean science has teased out intricate, subtle relationships.

We have discovered that life in the oceans maintains the biogeochemical cycles necessary to sustain life on earth, and that we share a mutual vulnerability to ecological change.

We recognize that oceans are conduits for threats to human health. But we've also found that life in the oceans offers potential sources of therapeutic compounds, which could be used to treat cancer and infectious diseases.

To understand and preserve these symbiotic relationships, we must study and protect the rich reservoir of organisms, physical and chemical processes, and ecological balances of the world's oceans.

[Collage with blue ocean and cholera inset]
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Today I'd like to highlight some of the ties that bind human health to the oceans, borrowing partly from my research on the relationship between infectious disease and the oceans. I'll also look to a future in which, using modern tools, we might reap a medical harvest from marine microorganisms.

During my 30 years of research, I have seen tools such as genomics, sensors, submersibles, and computational analysis effect a "sea change" (forgive the pun) in the research on infectious disease, oceanography, climatology. In fact, marine biotechnology, from a scant beginning in the early 1980s, is now a significant component of the global efforts in biotechnology, per se. The complexity of the discoveries that have been made in the past few decades would have been unimaginable by Forbes and the crew of the Challenger.


[Biocomplexity spiral]
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The spiral of biocomplexity is a framework for studying the interactions between biological systems and their physical environments. We have learned that ecosystems--including oceans--host an intricate web of life that adapts in multiple dimensions to environmental change.

I use the form of a spiral to underscore the point that these interactions occur at multiple levels, from the nanoscale to the global. The spiral of biocomplexity unfurls at the scale of the atom, and curves up through successive levels of life, through the cell, the organism, the community, and the ecosystem.

The lens of biocomplexity helps us understand the links between the oceans and health. For example, shifts in climate, whether natural or caused by human activity, cause physical and chemical changes in the world's water reservoirs. Organisms adapt. The sophisticated tools at our disposal allow greater understanding and observations from multiple perspectives.

[Frequent flyers]
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We observe from a global as well as local perspective. As the movement of living beings--whether invasive species or pathogens or humans--accelerates, and circles the globe, so does the scope of biological and oceanographic research.

Air travel, for one, has skyrocketed in the past half century, increasing the transport of microorganisms. As Gro Harlem Brundtland—former director of the World Health Organization—has said, "In the modern world, bacteria and viruses travel almost as fast as money. With globalization, a single microbial sea washes all of humankind. There are no health sanctuaries."

[Slide not available]
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Microorganisms travel by land, sea and air, via international trade or accidentally, in ocean-going ships. Here we see a scientist inside the ballast tank of a ship, collecting water samples.

Many species of animals and plants have been introduced into new habitats. Even cholera bacteria have been detected in the ballast water of ships entering the Chesapeake Bay and the Great Lakes after an ocean crossing.

However, I hasten to add that the cholera vibrio is a natural inhabitant of the coastal, estuarine, and riverine areas of temperate and tropical regions. Thus, disease-causing organisms are spread by natural marine processes as well.

[Harmful algal blooms]
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Virtually every coastal state today is threatened with harmful algal blooms, which occur when algae reproduce in great numbers and release toxins in ocean waters.

These blooms are a notorious hazard, and a primary subject of this session. More than 60,000 human infections occur each year in the United States alone, from eating contaminated seafood or inhaling contaminated sea spray.

To manage the risks to human health, we must determine what triggers blooms, whether they are linked to climate and/or pollution, and how algae are transported throughout the world oceans. The EU-US Collaborative Programme on Harmful Algal Blooms, a joint initiative of the European Commission and the National Science Foundation, will support international research in these areas.

HABs are not the only human health threat in the oceans. Bacteria and viruses, including human pathogens, reach estuaries and coastal water through sewage and storm runoff and via the deep ocean dumping of domestic and industrial wastes.

We must keep in mind also that, for some bacteria, the ocean serves as a natural reservoir. One of those is Vibrio cholerae, the causative agent of cholera.


[Chesapeake Bay map with inset of cholera]
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Cholera is still a devastating presence in much of the world, including Bangladesh, where I've done much of my research.

We know the disease is spread through water contaminated with human and animal waste. But, in the 1970's, we discovered that the ocean is the natural reservoir, when we identified the organism in water samples from Chesapeake Bay, in the eastern United States.

Using biochemical methods that were new at the time--direct fluorescent assays--we were able to demonstrate that the vibrios were present all year long.

[Tube worms and eel around undersea vent]
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Twenty years ago, Vibrio species were isolated from colonies such as this one around deep-sea hydrothermal vents. Recently, some of our deep sea isolates of Vibrio species have borne molecular similarities to V. cholerae. This suggests that cholera is native to the deep sea, and our experiments have shown that it can survive in extreme environments; that is, under high hydrostatic pressure and in anaerobic habitats.

[Vibrio cholerae: small and large chromosomes]
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Recent advances in genomic techniques have helped to substantiate that theory. In 2000, the genomes of the two chromosomes of V. cholerae were sequenced. The sequencing data confirm that V. cholerae is a versatile organism, able to live in several habitat types beyond coastal waters and the human intestinal tract.

These techniques also confirmed that Vibrio cholerae has the ability to transfer genetic material. Deadly outbreaks of cholera in India and Bangladesh after 1992 were caused by a strain of cholera that had not previously been known to cause epidemics. This strain had picked up toxin genes from other cholera bacteria in its environment.

This was a significant turning point in cholera research because we now understood that a new strain could arise from genetic recombination and DNA transfer. This knowledge underscored our need to understand its capacity to evolve and adapt to its environment.

[Copepod with egg case]
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In the aquatic environment, V. cholerae colonizes the oral region and eggs sacs of copepods, components of zooplankton common to salty and brackish water. It can also be isolated from fish and shellfish, especially in the coastal areas of developing countries.

As many as 7,100 vibrios have been measured on a single copepod. In an area where drinking water is not treated, several copepods could be ingested in a single glass, containing an infectious dose that could cause cholera in a human being.

We hypothesize that cholera originally evolved commensally with marine animals such as copepods, which provided them a surface to grow, nutrition, and perhaps other mutual benefits. The organism possesses pili and forms biofilms that enable it to adhere to surfaces, such as those provided by copepods and crustaceans. Essentially the same mechanism allows the cholera bacteria to stick to the human gut.

[Global spread of cholera, 1961-1991]
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The pattern of outbreaks on multiple continents led me to further exploration of cholera's relationship with the ocean. In the 1990s, India and Bangladesh experienced multiple outbreaks of cholera. During a similar time span, the disease returned to Peru and Latin America, after a century's absence from the Americas.

We knew the epidemics on both continents were seasonal. Using remote sensing data, we discovered a correlation between increased ocean temperature and height and subsequent outbreaks of cholera.

[Graph: SST, SSH, and cholera in Bangladesh]
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The satellite data showed that cholera outbreaks in Bangladesh occurred shortly after sea surface temperature and sea surface height reached their zenith. This usually occurs twice a year, in spring and fall. Higher water levels carry potentially infected water farther inland.

In Chesapeake Bay, we confirmed that native V. cholerae populations increase when the weather warms and freshwater influxes reduce salinity. In fact, temperature and salinity combined predict the presence of V. cholerae with an accuracy of between 75.5 and 88.5 percent.

[Slide not available]
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The patterns we discovered in the Chesapeake Bay and the Bay of Bengal held true on a third continent. The cholera outbreaks in Peru also followed a seasonal pattern. Again, we found a correlation between increases in water temperature and annual outbreaks of disease.

We also suspected a correlation with the El Nino Southern Oscillation, and took advantage of the predicted El Nino event of 1997-1998 to confirm it. Warm water along the coast, coupled with plankton blooms fostered by El Nino rains, appears to have helped amplify the populations of cholera bacteria in the ocean.

Techniques that emerged in recent years from the genomics toolkit--including PCR, a fast method of testing for specific DNA; genomic fingerprinting; and fluorescent gene probes--have enabled a more efficient and more accurate sampling of the fluctuating populations.

[Collage with cholera-carrying copepod and biocomplexity spiral background]
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The tools--ranging from DNA detection to overhead observations--lend insights into the complex behavior of infectious bacteria. They also offer hope for moving from discovery to prediction, and from there, to pathways of prevention.

Observations of sea surface temperature and height, as well as plankton blooms, play a role in predicting outbreaks of cholera. Through remote sensing, we can determine when the bloom is occurring. The climate-cholera link seen in the years of El Nino suggests yet another early warning system.

[Gorgonia ventalina (sea fans) infected with aspergillosis]
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Cholera is but one threat associated with the oceans. In seeking to predict other vulnerabilities, we find another early warning system: depletion of marine populations.

The loss of as much as 30 percent of the world's coral reefs is thought to be attributed to changing climate patterns and the degradation of ocean ecosystems. Such conditions could favor the spread of plant, animal, and human disease and encourage the emergence of new pathogens.

Here, we see Caribbean sea fans infected by aspergillosis, a fungal condition that originates on land. Increased freshwater runoff, erosion, and warming ocean temperatures are factors suspected to be increasing the vulnerability of the sea fan.

In examining the condition of these gorgonian corals, researchers uncovered an interesting property: a natural resistance to disease. The corals produce antibacterial and antifungal chemicals, which are now being studied for potential applications in human medicine.

Thus the vulnerability of these creatures signals both impending threat and pharmaceutical promise. You could say this is the ultimate irony of a biocomplex world.


[Diver with sponge]
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The potential for a medical harvest increases the incentive to study and protect the ocean's bounty. The diversity of life at higher taxonomic levels is greater in the ocean than on land, suggesting that many compounds with therapeutic qualities could be found. Already, the oceans have offered up a rich pharmacopoeia.

[Pseudopterogorgia elisabethae (sea plume)]
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The sea plume Pseudopterogorgia elisabethae is harvested for its anti-inflammatory and analgesic compounds, valuable in therapeutic creams and cosmetics. Scientists are using the genetic sequence to help clone a key enzyme and produce a synthetic equivalent, thereby ensuring a sustainable supply while protecting the natural reefs.

This project will lay the groundwork for the biosynthesis of a broad range of anti-inflammatory, anti-cancer, and antibiotic compounds produced naturally in marine invertebrates.

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In many cases, discoveries of pharmaceutical potential are a surprising byproduct of marine surveys and basic research on marine evolution, physiology, and disease.

As you are well aware, resistance to antibiotics is increasing. Traditionally, many of our antibiotics, such as actinomycin and streptomycin, have come from soil-based bacteria in the family Actinomycetales. In fact, these bacteria are one of the single most important sources of prescription drugs.

But researchers have had diminishing success in finding new antibiotic compounds among terrestrial organisms. Instead, new strains of actinomycetes have been found in the ocean.

[Three Florida sponges]
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One potentially rich source is the sponge, which acts as a sort of "marine condominium" for microorganisms living within its porous structure. The microbes form a symbiotic relationship with their host--a thriving colony indicates a healthy creature.

In studying the ecology of sponge "condominiums," such as the ones shown here in the Florida Keys, scientists were surprised to find many new types of actinomycetes.

Sponge colonies offer more than just antibiotic potential. In Indonesia, the bacteria residing among sponges also appear to contain compounds that appear to be effective in inhibiting the malaria parasite.

[Cone snail shells]
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We know—as a National Research Council report puts it—that "many aquatic species have been waging 'chemical warfare' with each other for millennia. . ." Tetrodotoxin, the weapon of the pufferfish, is at least an order of magnitude more lethal than the venom of the black widow spider. Yet, in tiny doses, tetrodotoxin can also relieve pain, and it has become a tool of neuropharmacology research.

The 500 species of the snail genus Conus, some of whose shells are shown here, also paralyze their prey, by injecting a venom that targets nerve and muscle cells. The cone snails could deliver new potency to our medicine chests. Researchers are using biochemical, biophysical, and molecular approaches to identify and biosynthesize compounds that could potentially target pain, epilepsy, cardiovascular disease, and neurological disorders.


[Collage with evolutionary tree and ocean]
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Ocean organisms provide another link to human health when they serve as models to investigate the basic mechanisms of life and the operation of human systems.

Our marine origin is enough reason to seek beneficial products and clues to our makeup from the oceans. The wealth of information that has already enhanced the study of human biology, chemistry, and mechanics reinforces the potential.

[Loligo pealei (squid)]
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Perhaps a favorite model is the squid. Some scientists have suggested nominating the long-finned squid (Loligo pealei) for a Nobel Prize for its contributions to basic biology, including insights into the electrical properties of nerves. This creature contains some of the largest axons--or nerve cells--found in nature, allowing it to mobilize with lightning speed. The giant axons are ideal for neurobiology studies, allowing scientists to determine that sodium and potassium channels in the cell membranes control nerve firing. Determining these relationships helped pave the way for understanding the electrical properties of human nerves and muscles, including the heart, and for developing anti-arrhythmic and nerve-blocking drugs.


These examples offer only a very few examples of what we can learn from the oceans as a vector of life and death, health and disease; a purveyor of environmental processes; and a model of environmental and human health.

The National Science Foundation and the National Institute of Environmental Health Sciences are collaborating to advance research on the complex interdependencies between the oceans and human health. The ideas ripe for research include many that I have described here: harmful algal blooms, waterborne disease, and marine pharmaceuticals. The program will fund the establishment of several Centers for Oceans and Human Health, which will bring oceanographers together with biomedical and public health scientists to carry out multidisciplinary studies.

Through the lens of biocomplexity, we see the links between oceans and human health through multiple perspectives--from the ecological balances that sustain us to the prospects for mutual benefit.

The vulnerability of the ocean is our vulnerability. Understanding its role in climate, chemistry, and evolution, and protecting its diverse resources, are the least that we owe to ourselves and our planet.

["Black smoker" hydrothermal vent]
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A hundred years after Forbes declared a dearth of life deep in the oceans, the author and poet D. H. Lawrence wrote: "They say the sea is cold, but the sea contains the hottest blood of all..."

You could say that Lawrence anticipated the incredible diversity of life and extremes of conditions we have since discovered in the oceans. In a biocomplex world, there are no isolated places. There are only niches yet to be explored.

1 Dr. Sunny Jiang, University of California, Irvine, session organizer.
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