Using novel genomic technology, marine biologists have found troubling clues that marine life could be extremely vulnerable to climate change. By mimicking future ocean climes and using gene chips to detect how marine organisms respond, the researchers can evaluate how well different organisms deal with environmental stress. The findings, while still preliminary and incomplete, are worrisome.
“What we’re doing is linking the predictions that are released by IPCC [the Intergovernmental Panel on Climate Change] with genomics to assess how changes in ocean chemistry will impact these ecosystems,” says Gretchen Hoffman, a marine biologist at the University of California, Santa Barbara.
Scientists predict that in the next 100 years, the ocean will become warmer and increasingly acidic–environmental changes that together could wreak havoc on marine creatures from krill to killer whales. Marine biologists want to know how organisms will respond to this stress: under what conditions can they adapt to climate changes, and when will they simply surrender?
Hoffman studies simple animals such as mussels and sea urchins, which are the ocean’s version of canaries in a mine. “They can tell you what’s happening in the bigger ecosystem,” she says. The urchins and mussels are grown in large buckets in Hoffman’s lab under atmospheric conditions that mimic those predicted by the Intergovernmental Panel on Climate Change. For example, by 2100, atmospheric carbon levels could increase from 375 to 540 parts per million–the so-called best-case scenario–or to 970 parts per million, the business-as-usual scenario.
The researchers then use a specially built DNA microarray–a small slide speckled with carefully chosen sequences of DNA–to measure which genes are activated in response to specific conditions, such as changes in temperature or acidity.
So far, the team has focused its attention on a set of proteins, known as heat-shock proteins, which kick in when an animal is under stress. Almost all animals carry copies of these proteins, which can repair other proteins that have been bent out of shape by heat and additional environmental stresses. According to early results from gene-chip studies, sea-urchin larvae raised at current carbon levels activate their heat-shock proteins when faced with warming water temperatures. But larvae raised at the best-case-scenario carbon level no longer activate these genes under stress and therefore can’t respond to a warming climate. “I don’t want to say we will lose all sea urchins,” says Hoffman. “But there will be some part of the population that can’t develop.”
Although it’s hard to predict exactly how that loss will affect the environment, it’s likely to change the structure of the entire ecosystem. Without algae-eating urchins, “you might predict that algae will become dominant in a particular area, which then might affect availability of fish that live there, which could affect the fishing industry or even tourism,” Hoffman says.
Hoffman is now collaborating with scientists in New Zealand and Mexico to study the impact of ocean warming and acidification in other areas. She hopes her work will spur more researchers to develop chips for other organisms, including those that are economically important, such as fish raised in fisheries. “I’d like to see the tools we’re developing be used as widely as possible in as many ecosystems as possible,” says Hoffman.
Some similar studies are under way. Coral, which protects coastal regions from storms and floods and provides habitats for thousands of marine species, may be particularly susceptible to warming oceans. When water temperatures climb, coral “bleaches,” meaning that the algae that live in the coral and give it its color die off. Monica Medina, a geneticist at the University of California, Merced, is developing genetic tools to study both the coral and the algal symbionts that live within it. She wants to determine what genes are activated both when coral begins to bleach and when it begins to recover.
George Somero and his colleagues at Stanford University are working much farther south. They have developed a microarray for fish that they are now using to study a specific species living in the Antarctic. Previous studies have shown that the fish, which is a major food source for marine mammals, has lost its ability to activate heat-shock proteins, and therefore it may be particularly vulnerable to climate change. “Now we’re using gene chips to see if they have lost other stress-response mechanisms,” says Somero. “We want to know what happens when the environment collapses. That hasn’t really been done before.”
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