"The Oceans and Human Health"
Dr. Rita R. Colwell
Director
National Science Foundation
COMPASS1 Forum hosted by the House Oceans Caucus
Washington, D.C.
October 6, 2003
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Good afternoon to everyone. I am delighted to speak with you on a subject near and dear to my heart: the oceans and their future.
We all have a stake in the health of our planet's oceans, and each of us, in some way, can shape that future for the better. I declare myself an unabashed advocate for ocean research, exploration, and conservation, and my intent is to provide persuasive reasons for strong advocacy.
Although oceans cover about 70% of our planet, we have only just begun to explore the extraordinarily rich diversity of life to be found there—from estuaries to seashores, from open ocean to the darkest depths, and from cold Antarctic waters to the tropics. On a global scale, we are beginning to tease out the intricate details of how life in the oceans maintains the biogeochemical cycles necessary to sustain life on earth, and their role in climate.
[Title slide: Oceans and human health]
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I've titled my remarks "Oceans and Human Health" to emphasize that our own fate and the fate of the oceans are inextricably linked. Although we often focus on disease and its cures, when we investigate this relationship, a larger, more complex picture emerges. We recognize that oceans not only harbor potential pathogens, but, most importantly, they maintain health. Only when we develop this somewhat subtle understanding, will we have the knowledge that is required to predict—and thus prevent—risks to human health.
I'd like to describe a new framework for viewing the relationship between human health and the oceans that allows us to do just that.
[New biocomplexity spiral]
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It's called biocomplexity. The term describes the study of complex interactions in biological systems, including humans, and between those systems and their physical environments.
We know that ecosystems, including oceans, do not respond in a simple, linear way to environmental change. We also know that understanding demands observing at multiple scales, from the nano to the global. Complex interactions emerge at various levels, whether studying a cell, a human body, or an ecosystem.
Interactions between health and oceans, whether natural or nefarious in origin, also span scales of space and time. For example, the earth's climate acts on a global scale, while decisions on human health are made locally.
[List of topics to be discussed]
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Today, I will take you on a brief tour of some of the links between human health and the oceans. One of the most visible of these—harmful algal blooms—and then move on to infectious diseases, the discovery of new drugs and models of basic life processes, and finally the role oceans play in planetary cycles.
[Red tide on the coast of Maine]
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Harmful algal blooms, or HABs for short—are probably the most notorious case of risks to human health associated with the oceans. HABs occur when certain species of algae reproduce in great numbers and release toxins in ocean waters. A variety of species contribute to the problem.
HABs can lead to human illness and death when humans consume contaminated seafood or inhale contaminated sea spray. More than 60,000 human infections occur each year in the U.S. alone, caused by toxins that exist at the limit of detection.
HABs are also a serious threat to marine resources, causing mass mortalities of wild and farmed fish and shellfish, as well as the death of marine mammals. When algae accumulate in huge numbers they block the penetration of sunlight and may alter the structure of an entire ecosystem.
[Map of U.S. HABs before and after 1972]
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HABs are increasing nationally and worldwide—both in frequency and duration. In the U.S. most coastal states have reported major blooms. This map shows the increase in their occurrence around the U.S.
Research is needed not only to determine what triggers HAB events, but to study to what extent and by what routes harmful algae may be transported in the oceans. The EU-US Collaborative Programme on Harmful Algal Blooms is a new initiative to support collaborative, international research. It is a joint effort of the European Commission and the US National Science Foundation.
HABs are not the only source of human health risks in the oceans. Bacteria and viruses, including human and wildlife pathogens, can reach estuaries and coastal water through sewage and runoff from terrestrial sources. We know little about what happens to these pathogens once they reach the marine environment. Indeed, seafloor sediments may provide a long-term reservoir for pathogens.
[Generic cholera: spiral]
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My own research on cholera tells yet another story. It is the saga of how ecology and infectious disease are linked, and exemplifies the need to be able to trace complexity in order to predict.
While largely controlled in the U.S., cholera is still a devastating presence in much of the world. It's endemic in Bangladesh, for example, where I've done much of my research.
[Chesapeake Bay sampling sites]
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My scientific quest to understand cholera began more than 30 years ago. In the 1970's my colleagues and I realized that the ocean itself is a reservoir for the bacterium Vibrio cholerae, the cause of cholera, when we identified the organism in water samples from the Chesapeake Bay.
We cannot eradicate the cholera bacterium. Understanding the ecology of the disease, forecasting major outbreaks, and controlling it by prevention and treatment are our only options.
[Copepod]
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Here we see a copepod close-up. This minute relative of shrimp lives in salt or brackish waters. It's the host for the cholera bacterium, which it carries in its gut as it travels with currents and tides.
[Cholera outbreaks, SST and SSH]
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As we now know, environmental, seasonal and climate factors influence copepod populations, and indirectly cholera. Populations peak in abundance in spring and fall. In Bangladesh, we discovered that cholera outbreaks occur shortly after sea surface temperature and sea surface height peak. This usually occurs twice a year, in spring and fall, the same time that populations of copepods peak in abundance.
Ultimately, we can connect outbreaks of cholera to major climate fluctuations. In the El Nino year of 1991, a major outbreak of cholera began in Peru and spread across South America. We can now link cholera with El Nino/Southern Oscillation events, providing us with an early warning system to forecast when major cholera outbreaks are likely to occur.
[Cholera montage]
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Understanding cholera requires us to explore the problem on different scales from genome to climate patterns. Add in economic and social factors of poverty, poor sanitation, and unsafe drinking water, and we begin to see how this microorganism sets off the vast societal traumas of cholera pandemics. What appears to be a tightly circumscribed biological problem—a bacterium that infects people--can have ramifications and interrelationships on a global scale.
I'll turn now to the vast, and largely unexplored, diversity of life in the oceans. Sea creatures great and small hold enormous potential for drug discovery and for basic insights into human health.
[Life around undersea vents]
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Genomics, for the first time, offers the possibility to identify "what's out there"—such as what lives in the rich communities around deep-sea hydrothermal vents, where life may well have originated.
Tubeworms, crabs and other vent-dwellers thrive there, along with bacteria and archaea in water near or above the boiling point.
[NSF PR 03-84]
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I look back to when I was a graduate student, when we were taught that the deepest parts of the ocean were devoid of life. Now, undersea vents are recognized as potential goldmines of genetic clues to how organisms handle environmental stresses, whether extremes in temperature, pH, salinity or oxygen.
Just a month ago, as this NSF press release portrays, Science Magazine featured "Strain 121"—a microorganism that lives at 121 degrees C—the hottest existence known, on a black smoker on the Juan de Fuca ridge off the northwestern United States. Derek Lovley and Kazem Kashefi of the University of Massachusetts-Amherst reported its discovery, originally isolated by John Baross at the University of Washington.
[Norbert Wu: Antarctic sea floor community]
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At quite the opposite extreme, in Antarctic waters, Jim McClintock and Chuck Amsler of the University of Alabama-Birmingham and Bill Baker, University of South Florida, have studied the basic chemical ecology of marine invertebrates. As a sideline, they have also supplied extracts of Antarctic compounds to drug screening programs, several of which show activity against cancer. Antarctica's diverse marine biota clearly have potential to yield novel chemicals with pharmaceutical potential.
[Streptomyces griseus standard antibiotic producer and a cousin of the "new" bacteria found in deep ocean sediments]
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Antibiotic resistance, which occurs when pathogens develop defenses against known antibiotics, has been increasing and poses a serious problem for treating bacterial diseases. In recent years, researchers have had diminishing success in identifying new antibiotics among terrestrial organisms. The oceans may be our best hope for new antibiotics.
Many of you will recognize the names of the antibiotics streptomycin, actinomycin and vancomycin—for many years staples in our drug arsenal. These antibiotics are the natural product of terrestrial microorganisms. This past year, William Fenical and colleagues at the Scripps Institute of Oceanography at the University of California-San Diego reported the discovery of related bacteria in deep ocean sediments that produce similar antibiotic molecules. These ocean organisms deliver a double punch. They also produce a substance that is a potent inhibitor of cancer growth.
[Coneshells]
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We know-as a recent National Research Council report puts it—that "many aquatic species have been waging 'chemical warfare' with each other for millennia..." A central means is neurotoxin; tetrodotoxin, one of the most potent neurotoxins known, comes from the pufferfish and has become a critical toxin in neuropharmacology and neurophysiology research.
Here are the beautiful cone snails, the group of 500 species that are the source of an incredible array of toxins. As Baldomera Olivera of the University of Utah says, these animals could be among the world's most successful pharmacologists, potentially producing tens of thousands of compounds—peptide toxins—with pharmacological activity. Each compound targets a specific compound in the cell. One cone shell's venom has inspired a synthetic molecule that shows promise to control chronic pain in patients resistant to opiates.
Ocean organisms provide another link to human health when they serve as models to investigate basic mechanisms of life.
[Sea squirt-adult]
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The lowly sea squirt, it turns out, is the first creature that we know to have evolved an immune system, and its embryo is similar to a human's.
The upper-right photo shows the notochord or precursor backbone of the sea squirt, and the diagram shows its evolutionary relationship with us. The sequence of the sea squirt's genome was announced just last December. Its relatively small number of genes helps to make it an ideal model organism to study how more complex life—including humans—evolved.
[Giant squid axon]
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Another sea creature, the squid, gave us the classic early insight that led to a better understanding of how nerve cells fire. The squid possesses a giant axon—a type of nerve cell, seen here—found in no terrestrial animal. The large size of the axon has enabled researchers to establish that potassium channels in cell membranes control nerve firing. This relationship is not only a basic mechanism of life but also plays a role in heart arrhythmias and seizures. Again, our own marine ancestry makes us regard marine diversity with a fresh eye—viewing animals as models as well as sources of compounds that control the developmental stages of life.
[Bobtail squid]
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On quite another front, great strides have been made in recent years on "listening in" on bacterial communication. My next example, which begins with a squid, shows how ocean ecology sheds new light on human disease. I am referring to a bobtail squid from Hawaii, which exudes a ghostly blue glow on moonlit nights. This occurs when the squid ingests quantities of luminescent bacteria, which glow inside the squid and cause its shadow to disappear—perfect camouflage.
The real secret, however, is the whispers that animate this community of glowing bacteria—whispers of communication that take place through chemical secretion. Only when enough chemical builds up—indicating that a critical number of bacteria are present—do they light up, making the squid glow.
[Signaling microbes]
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Bonnie Bassler of Princeton University and others have discovered that this bacterial communication governs a wide variety of bacterial pursuits. E. coli and many other bacteria responsible for human diseases use similar signaling.
Discovery of the "signaling gene" could lead the way to foiling drug-resistant bacteria. Here's a case in which the study of marine bacteria's luminescence—once considered "incredibly arcane, with no application at all"—produces a fundamental insight for human health.
[Nacre inset with spiral background]
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This image symbolizes another area of promise: nacre, or mother-of-pearl, is renowned for its strength and flexibility. Chemists supported by NSF have taken natural nacre as their model to create a lightweight, artificial material, shown in the inset picture. Fashioned at the nanoscale, that material could have ultimate application in artificial bones.
The medical harvest from the sea is really no surprise; our evolutionary connection is a compelling reason to seek beneficial products, pathways and clues to our won makeup from the oceans.
Vestiges of our origins include the composition of our blood, the rudimentary gills of early human development, the natural swimming response of babies in water. We turn to the sea not only for medical compounds but also for clues to blood pressure control and to the transfer of carbon dioxide in the lungs.
Because microorganisms play a central role in the cycling of carbon, nutrients, and other matter, they have large impacts on other life - including humans. Recent research has shed new light on these complex interdependencies in the oceans.
[Bacteria in background, chart in foreground]
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Oded Beja and Ed Delong of the Monterey Bay Aquarium Research Institute recently discovered a new photosystem in ocean microorganisms. Through creating a library of DNA from marine microbes, they discovered bacteria containing a photoprotein called photorhodopsin. They have shown that the bacteria containing this energy-generating, light-absorbing pigment are almost ubiquitous in the world's oceans.
Another remarkable feature: genetic variants of these bacteria contain slightly different pigment molecules that seem "tuned" to absorb light of different wavelengths, matching the type of light penetrating to different depths. They may be a part of the carbon cycle and hence be necessary to refining global climate models.
[Title slide image without words]
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Human activities enter the picture when we consider these vast biogeochemical cycles and the oceans. For example, agriculture, mining, and the burning of fossil fuels have increased nutrient levels in the environment. Nutrients can serve as limiting factors controlling the biodiversity, dynamics, and functioning of many ecosystems.
Nutrients that find their way to the ocean from runoff and sewage can stimulate the growth of algae and lead to harmful algal blooms and the "dead zones" caused by loss of oxygen. They also can contribute to fish kills, loss of seagrass beds, degradation of coral reefs, and loss of commercial and sport fisheries and shellfish industries.
Yet we still know little about the controls on nitrogen fixation and denitrification processes in ocean water and about the triggers of harmful algal blooms. Similarly, we have not unraveled the effects on coastal oceans of the buildup of phosphorus in agricultural soils. Knowledge about these processes could help us identify ways to mitigate the flows or effects of excess nutrients.
The National Science Foundation and the National Institute of Environmental Health Sciences are collaborating in a new initiative to advance fundamental research on oceans and human health. The ideas ripe for research include many that I have described here: harmful algal blooms, vector and water-borne diseases, and marine pharmaceuticals. The new program will fund the establishment of several Centers for Oceans and Human Health. Each Center will bring together ocean scientists with biomedical and public health scientists to carry out multidisciplinary investigations of the complex interconnections that characterize the dynamics of physical, chemical, biological ocean systems and human health.
These examples just scratch the surface. I return now to where I began—to a new way of viewing the links between the oceans and human health.
When we limit our view of human health to problems of disease, diagnosis, and cure, we miss a significant perspective. A larger vision recognizes the evolutionary processes through which we arrived on the scene, and the ecological balances that sustain us. We see the vulnerability of the oceans and life that resides there as our vulnerability. That is what links our health to the health of the oceans.
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