By Lee Anna Sherman
When talk turns to the mud-dwelling creatures of the deep seafloor, Mark Hixon jumps up from his swivel chair, strides to a cabinet in his office and swings open the door. Taking out a long cardboard box, he gently lays it on his desk.
“This,” he says, reaching inside, “is a sponge from just off the Oregon coast. Isn’t it cool?”
He holds up the dried organism, an 18-inch-long spire the color of raw pinewood, delicately honeycombed. Its tousle of roots tells you why scientists long classified sponges, mistakenly, as plants. In your hand it is nearly weightless.
“There’s a whole host of things that live down there,” says Professor Hixon, an internationally known marine ecologist in OSU’s Department of Zoology.
The astounding array of seafloor organisms — brittlestars and bivalves, marine worms and sea pens, cold-water corals and sponge species by the score — plays a vital role in ocean systems by providing food and shelter for finfish and shellfish. Before manned submersibles and remotely operated vehicles (ROVs) gave scientists direct, deep-water access, Hixon says, many viewed the teeming ocean mud as empty ooze. Now they know the seafloor is the “nursery” for many of the finned species humans eat.
Since he came to OSU in 1984, Mark Hixon has received research support from the National Science Foundation and National Undersea Research Program of the National Oceanic and Atmospheric Administration. In 2004, the ISI Citation Index recognized him as the most cited author in the Western Hemisphere on coral reef ecology in the past decade. His reports have appeared in the journals Science, Fisheries, Ecology, American Naturalist and Proceedings of the National Academy of Sciences, among others.
Hixon’s research on fish population dynamics has taken him to most of the planet’s oceans, both temperate and tropical. One of the world’s leading authorities on coral reefs, he has been cited in scientific journals more often than any other coral-reef ecologist in the Western Hemisphere over the past decade, according to the Thomson Institute for Science Research. He was ranked third worldwide behind two scientists who live adjacent to coral reefs year-round.
One big mystery relevant to both fisheries management and marine conservation is whether and how isolated populations of adult fish are linked. Understanding these links will help answer questions such as, Can protecting fish in one location compensate for overfishing in another location? Hanging in the balance are decisions about marine reserves that, while designed to sustain fisheries, have raised fishing industry concerns.
In two ongoing studies — one in Hawaii, the other in the Bahamas — Hixon and his graduate students are investigating connections among isolated populations of coral-reef fishes. They are studying the demographics of the yellow tang on Hawaii’s Big Island and the bicolor damselfish in Exuma Sound off the Bahamas. They are sampling DNA from adult and juvenile fish at multiple reefs. Their goal is to understand the drift patterns of fertilized eggs and larvae that travel with tides and currents in a process known as “larval dispersal.” And they are testing whether a high level of larval connectivity is also reflected in the population dynamics of adult fish.
Ultimately, the answers will guide conservation and management, not only of fish, but of the reefs themselves. These complex ecosystems brim with more species than anyplace on the planet, even tropical rainforests. And many are dying. Pollution, global warming and overfishing have degraded about 20 percent of Earth’s coral reefs so far. Another 50 percent are at risk. In Hawaii, the yellow tang, coveted by the aquarium trade for its brilliant color, was depleted until the state created marine reserves along the Kohala-Kona coast to protect them. Preliminary data from Hixon and his colleagues suggest the reserves are working. “Long-term policy about marine reserves must be based on data rather than hearsay,” he says. The yellow tang genetics, still being analyzed in Hixon’s lab, will reveal which of Hawaii’s reefs need replenishment from spawn drifting in from highly productive “source” reefs and where those respective reefs are located.
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In his three decades as a fish ecologist, Hixon has dived in oceans from the Pacific to the Atlantic, the Caribbean to the Coral Sea. Studying marine science at UC Santa Barbara was, for him, just a natural extension of a sea-centered boyhood as a surfer and the son of a naval officer. As the family moved from one coastline to another, young Mark – a fan of Sea Hunt and ocean explorer Jacques Cousteau – had a recurring dream: He would be standing on the beach trying to imagine what lived beneath the heaving seas when, suddenly, the water would disappear, revealing fishes “swimming around in the air.”
As a doctoral student in the 1970s, he shivered through dozens of bone-chilling dives in cold-water kelp forests. These days, he relies on small research submarines in the frigid northern waters as he studies the ecology of coastal marine fishes, focusing on what naturally regulates populations and sustains biodiversity. His scuba gear gets used mostly in warm-water ecosystems.
The tropical reef research, part of OSU’s top-ranked efforts in conservation biology, has relevance here in Oregon. “Off Oregon, it’s impossible to gather the enormous amount of data we can extract from warm, clear tropical waters,” Hixon says. “However, once our methods are developed and tested in the tropics, we can bring them home to Oregon.”
Such research is timely. Governor Ted Kulongoski is leading an initiative to create marine reserves in the Oregon Territorial Sea to replenish and preserve the state’s marine ecosystems and fisheries. Hixon’s work will help test the effectiveness of Oregon’s reserves. For example, in the 1990s, Hixon, who chairs the Marine Protected Areas Federal Advisory Committee, witnessed a post-trawl patch on Oregon’s continental shelf from the portal of a research sub named Delta. He and his team were surveying fish populations on the rocky reefs between Bandon and Cape Blanco, a fish-rich outcrop called Coquille Bank, when they stumbled upon a muddy area deeply scarred by groundfish trawl nets. An adjacent area unmarred by trawl tracks provided a readymade control site. The researchers decided to conduct a comparative study, the first-ever documentation of trawling impacts on the deep mud seafloor off North America’s West Coast.
The contrast was stark. About half as many groundfish species were living in the trawled area as in the untrawled area. Numbers of individuals, too, were significantly lower in the trawled site. Most striking, though, was the disparity in sea pens and other invertebrates. Members of the jellyfish phylum, the fragile, soft-bodied sea pens stood out brightly in Delta’s spotlight as it scanned the sediment in the lightless depths. Forests of the flowerlike stalks of yellow-and-orange polyps were anchored in the untrawled mud. But where the nets had passed, sea pens were virtually absent, Hixon and Brian Tissot of Washington State University reported in the Journal of Experimental Marine Biology and Ecology last year.
Sea pens and other such invertebrates can’t swim away when their habitat is disturbed. Nor can they quickly rebound. These “sessile, slow-growing, long-lived species,” Hixon notes, “are likely to recover slowly” from the effects of bottom dragging.
“What we saw off Coquille Bank,” Hixon concludes, “was completely consistent with studies conducted all over the world showing that bottom trawling has severe impacts on seafloor habitat.” Unfortunately, Hixon and Tissot’s findings were dismissed by the Oregon trawl industry, which questioned their validity, despite appearing in a peer-reviewed scientific journal.
“My greatest frustration as a scientist happens when any special interests reject peer-reviewed science,” says Hixon. As Chair of the Ocean Sciences Advisory Committee for the National Science Foundation, Hixon notes that rejection of scientific findings about climate change and ocean acidification stem from the same attitude. Hixon likes to quote Aldous Huxley, author of Brave New World: “Facts do not cease to exist because they are ignored.”
For Hixon, biology and conservation have become inseparable as threats to the oceans continue to grow. “The challenge,” he says, “is to successfully walk the fine line between scientific objectivity and personal advocacy. Some scientists refuse to walk that line, but I did not abdicate my citizenship when I became a scientist.” Discovering how to connect science (left-brained and analytical) with public engagement (right-brained and passionate) is as urgent to Hixon as tracking fish movements across reefs. Data alone won’t save our oceans. “People must feel it here,” he says, placing his hand over his heart, “to value not only themselves and the present, but also to value others and the future.”
To that end, he and Professor of Philosophy Kathleen Dean Moore, director of OSU’s Spring Creek Project for Ideas, Nature and the Written Word, are investigating the psychology of conservation communications: how to craft messages that effectively change minds and behaviors.
Mark Hixon wants our progeny to inherit a world still relatively intact. He wants tomorrow’s children to have a chance to dive into the pulsating rainbow of biodiversity that is the tropical reef. “You feel as if you’ve fallen into a universe of stars,” he says. “It really, truly is amazing.”
Meet the photographers, Daniel and Robbie Wisdom
Protecting tropical reefs is a passion for these two graduate students in OSU’s College of Oceanic and Atmospheric Sciences. The Idaho natives plan to live in Australia where they can pursue scuba and underwater photography. Both are enrolled in OSU’s Marine Resource Management program. Daniel works with Assistant Professor Kelly Benoit-Bird analyzing fish-school movements with high-frequency sonar. Robbie is studying cooperative marketing programs for small seafood micro-canners in the Pacific Northwest with Gil Sylvia, superintendent of the Coastal Oregon Marine Experiment Station in Newport.
See Mark Hixon’s 2010 “Oceans of Life” presentation for the F.A. Gilfillan Memorial Award
- Mark Hixon’s Web site
- Department of Zoology
- College of Science
- National Science Foundation
- National Undersea Research Program
- OSU Foundation
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