Genesis of Eden

Genesis Home


Humpback whales may provide crucial nutirents to ocean-bottom dwellers by sinking to the sea floor after they die. By severelylimiting this food supply, the extensive hunting of whales mayhave already irreversibly altered the marine ecosystem.

Diversity Blues Scientific American Aug 94 10

Oceanic biodiversity wanes as scientists ponder solutions

Stop press Jan 98: A news report from a whaling commission cites ocean pollution as the principal threat to large marine mammals, particularly because of the position many have high up the food chain.

The evidence is everywhere. Populations of fish and shellfish, of corals and mollusks, of lowly ocean worms, are plummeting. Toxic tides, coastal development and pollutant runoff are increasing in frequency and dimension as the human population expands. The oceans-near shore and in the abyssal deep-may be reaching a state of ecological crisis, but, for the public, what is out of sight is out of mind. "The oceans are in a lot more trouble than is commonly appreciated," rues Jane Lubchenco of Oregon State University. "There is great urgency." To remedy this situation, marine scientists recently gathered in Irvine, Calif., to devise a national research strategy to protect and explore marine biodiversity. Although the variety of organisms found in the oceans is thought to rival or exceed that of terrestrial ecosystems, there is no large-scale conservation effort designed to protect these creawms. hideed, there is no large-scale effort even to understand the diversity found in saltwater regions. The National Research Council meeting attendees first set about estabhshing their ignorance: the system they study remains, in large part, a mystery. Several years ago, for instance, J. Frederick Grassle of Rutgers University reported that previous esfimtes of the number of organisms thriving on the deep-sea floor were probably too low. in analyzing sediment from an area off the coasts of Delaware and New jersey, Grassle found 707 species of polychaetes, or worms, and 426 species of crustaceans. All these creatures were harvested in samples taken from boxes that measured only 30 centimeters per side and 10 centimeters in depth. Earlier studies had suggested a total of a mere 273 species of polychaetes. As researchers at the meeting emphasized repeatedly, even the diversity of areas that have been exhaustively studied is not fully appreciated. New findings about star coral, or Montastraea annularis, offer a dramatic example. This organism 'is sort of a lab rat of corals," explains Nancy Knowlton of the Smithsonian Tropical Research Institute in Panama. "It is an extremely intensively studied coral." Knowlton and her colleagues have discovered that this single species of coral is, in fact, three species in shallow waters. (There may be even more species in the star corals that inhabit deeper water.) These various species have also been found to be adapted to different depths. Knowing that diversity is out there, however, has not yet allowed marine researchers to make a stab at species numbers-something their peers on land have been able to do to galvanize public action "We are not close to making an esfimte," Knowlton acknowledges. "Even a seat-of-the-pants guess might be off by an order of magnitude." Identifying threats to the oceans was less tricky. Although the usual suspects were in the lineup-including oil spills, the destruction of estuaries, toxic dumping and the introduction of nonindigenous species that outcompete the locals-conference attendees deemed fishing the greatest danger to marine biodiversity. "I was pretty surprised. The impacts of fishing have been at the top of my list for years,' says Les Wading of the Darhng Marine Center at the University of Maine. 'But I thought there was not such a big awareness of that. The biggest problems are usually seen as pollutants or eutropWcatiorL" (Eutrophication is caused by excess nutrients from such chemicals as fertilizers and can lead to algal blooms.) Nevertheless, reports about the global decline of fisheries keep coming in. As Carl Safina of the National Audubon Society outlined in a recent article in Issues in Science and Technology, catches of groupers and snappers fell by 80 percent during the 1980s, and the population of swordfish in the Atlantic Ocean has fallen by 50 percent since the 1970s. In addition to the depletion of fishwhich may have far-reaching but little understood ecological effects-fishing often wipes out habitat. By trawling on the seafloor, vessels disrupt bottom communities or coral reefs. Waflft cites the destruction of sponges in the Gulf of Maine as one example. Last seen in 1987 on a videotape taken from a submarine, "the sponges are gone. They have been ground off the rocks,' Watling states. These sponges may be iinportent nursery habitats for species such as cod-of course, that possibility reveals another marine unknown. 'The real problem is that we do not know anything about the ftrst year of Iffe in cod,' Watt warns. A crisis in taxonomy also worried the scientists. Every researcher had a complaint about years going by before he or she could get someone to identify an alga, about seminal papers misidenti4ft creatures, about graduate students receiving no training in taxonomy. Without good taxonomy, trying to identify and protect diversity becomes moot. Beyond the challenge of identifying species correctly is the challenge of understandmg their interactions. If marine biology is going to help policymakers, it has to be at least somewhat predictive. Even if the effects of climatic change on a certain species are understood, for example, the implications for the entire ecosystem may be obscure. Unpublished studies by Lubchenco about increases in water temperature caused by a power plant in Diablo Cove, illustrate just this problem 'You could not have predicted the changes that occurred based on a knowledge of the individual species' sensitivity to water temperature,' Lubchenco explains. "What is going on is greater than the individual response." Getting the scientific community to voice concern about the threat to oceanic ecology was the first step, according to conference chairs Cheryl Ann Butman of the Woods Hole Oceanographic Institution and James T. Carlton of Williams College and Mystic Seaport. Designing a research program that wfll address the issue and receive ftmding from Congress is the next task at hand. The most dimcult hurdle may be catalyzing public awareness before the marine environmt-nt is altered beyond the point of no return. As Butman and Carlton describe, hunting whales may already have altered the oceans utevocably. Because deep-sea organisms rely on food falling from the surface, large carcasses of whales may have been one of the major sources of nutrients for the bottom of the food chain The sulfur-rich bones of whales may have provided stepping-stones for sulfur bac tena and other o as they moved from hydrothermal vent to vent. Fewer sinking cetaceans may have had miportant impacts on deep-sea processes. 'Unfortunately, the question is impossible to answer now,' Butman comments. 'But it certainly would be irresponsible of us to put ourselves in a position like this again-that is, a position where we embark on a dramatic alteration of species diversity, which is what the whaling industry represents-without evaluating the ecological consequences.' -Marguerite Holloway