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Imagine if only 1 percent of your children survived to adulthood — and that that was normal. For most marine species, including lobsters, clams, cod, and herring, that’s the way life is. They begin as larvae, and drift along for miles on ocean currents in a process called dispersal. Most die during dispersal —some are eaten by predators, others wither in too-harsh environments, and many simply don’t make it to their destinations and starve to death.
The larvae have to separate from the parent organisms in order to develop and find mates. “Dispersal prevents inbreeding,” said Mary O’Connor, a doctoral student in marine ecology in UNC’s Curriculum in Ecology and the Department of Marine Sciences. “For some species, this is a time to move from breeding ground to a habitat where they’ll mature.”
Scientists have long known that warm water temperatures speed larval development and metabolism. But O’Connor and her collaborators, which include UNC’s John Bruno and Jack Weiss, have found that the distance larvae travel before they mature is directly linked to ocean temperature — specifically, larvae don’t travel as far in warm waters as they do in cold waters.
“Temperature can alter the number and diversity of adult species in a certain area by changing where larvae end up,” O’Connor says. “To conserve and manage marine animals, whether for harvested fish stocks or for conservation of biodiversity, we need to know how they will respond to climate change.”
O’Connor and her collaborators used data from 72 species to develop a model that predicts how far larvae will travel at certain temperatures. The model can make predictions about almost all marine animals that go through a larval stage, without having to closely investigate each different species.
“The link between ocean temperature and larval movement help us to understand and predict patterns of the number of fish and other animals from year to year as ocean temperatures fluctuate,” O’Connor said. Although their model suggests that warm water can keep the larvae from traveling very far, it may also mean they’re more likely to survive dispersal.
“This could mean some populations may become isolated from other populations,” she said. “It also means Marine Protected Areas should be close enough to each other to allow animals to disperse from one protected area to another.”
Understanding ocean life makes possible better biodiversity management. “Better management and conservation means there is a greater chance people will be able to enjoy ocean ecosystems, either through tourism or by eating fish, for a long time, even as the entire ocean environment changes and already unsustainable fishing pressure increases,” O’Connor said.
For this study, O’Connor, Bruno, and Weiss collaborated with researchers Steven Gaines, Sarah Lester, and Brian Kinlan of the University of California, Santa Barbara, as well as Benjamin Halpern of the National Center for Ecological Analysis and Synthesis in Santa Barbara, California.
Provided by Research and Economic Development.
Editor: Neil Caudle
Writer: Margarite Nathe