The Hidden Biodiversity of the Ocean Realm

Then and Now: In the 1860s, Ernst Haeckel used a simple microscope and ink to describe 3,000 new species of Radiolara (above), a group of minute marine microbes that measure just one-hundredth of an inch across. More recently, scientists have used high-powered microscopes and photography to study these (below) and even smaller bacteria. Today's genetic techniques allow researchers to look beyond appearances, which has led to an explosion of discovery. Illustration by Ernst Haeckel, Kuntsformen der Nature (1904); microbe photo couresty of Dave Caron Lab.

To get a sense of how marine biology has evolved in the last century, consider USC’s Allan Hancock Foundation building. From its construction in the 1930s until the last decade, wooden shelves holding hundreds upon hundreds of glass specimen jars filled much of the red-brick building’s core. The collection revealed the great diversity of form, color, geographies and habitats of ocean life.

Today, the jars are gone. The rooms have been gutted and remodeled. The long shelves have given way to laboratory benches, gene amplifying machines, centrifuges, computers and other equipment of a modern molecular lab. These are the tools driving a new era of discovery, allowing scientists to describe the biological diversity of the sea in greater detail than ever before.

“A huge amount of biological diversity has been totally undetectable without genetic tools,” said marine microbiologist Jed Fuhrman, the McCulloch-Crosby Chair in Marine Biology in USC College and a member of the USC Wrigley Institute for Environmental Studies. “That’s been especially true for microbes, the most abundant kind of life on Earth.”

Using state-of-the-art genetic tools, Fuhrman and his colleagues have begun to reveal the heretofore hidden diversity among marine plankton and microbes, as well as the unexpected ways these microscopic organisms make a living. Others are exploring another frontier of biological diversity — the genetic diversity of individuals within a species — in studies of marlin, oysters and other larger creatures.

“Biodiversity runs the natural world,” Fuhrman said. “Human beings don’t exist in a vacuum. Everything’s connected. So if we want to understand our world, we have to understand all of the other organisms in it.”

To many, biodiversity refers simply to the number of different species on Earth. “Biologists think of biodiversity more broadly, not only as the diversity of organisms, but also of their functions and abilities, their appearances, their roles in the system,” Fuhrman said.

Geneticist Dennis Hedgecock believes biodiversity contributes to a healthy environment, but says hard evidence supporting that belief has only just started to emerge. He points to a 2006 study in the journal Science showing that both species and genetic biodiversity increase the productivity and stability of the ocean ecosystem, making it more resilient to major disturbances, both natural and human.

“This is some of the first evidence showing that biodiversity matters, at least for large species,” said Hedgecock, the Paxson H. Offield Professor of Fisheries Ecology in the College.

Using genetics, Jed Fuhrman has identified hundreds of new species of marine bacteria and provided new insights into global microbial diversity. Photo credit: Phil Channing Click here for high-resolution photo.

Hedgecock’s studies of genetic diversity in oysters, sea bass and salmon have helped to promote more thoughtful management of commercial and recreational fisheries, as well as conservation breeding programs. He and Donal Manahan, professor of biological sciences, study oysters and recently published a paper pinpointing the genes that gives a breed of hybrid oysters an advantage over others. “We’re studying which genes allow one individual to successfully reproduce or grow larger than others in the same population,” Hedgecock said.

Suzanne Edmands, an associate professor of biological sciences, also investigates genetic variation in marine creatures. Her aim is to better understand the mechanisms by which new species form, as well as the implications of genetic biodiversity for fishery management and conservation efforts.

“Diversity within populations allows adaptation to new circumstances or stresses, like infection or the increasing sea temperatures associated with global warming,” said Edmands.

In one project, Edmands and marine biology doctoral student Catherine Purcell are looking at the genetics of striped marlin populations in the Pacific. Their results show surprisingly large genetic differences in the absence of obvious geographic barriers. For example, they find a genetic break between Southern California and Mexico marlin populations, which both spend time in the fall near the tip of Baja California. Meanwhile, populations in Japan and Hawaii, though separated by thousands of miles, show no genetic differences between each other or the Southern California group.

In addition to studying the genetic basis of hybrid vigor in high-yield oyster varieties, Dennis Hedgecock investigates how fish hatcheries impact the genetic diversity of wild populations. Photo credit: Phil Channing Click here for high-resolution photo.

“Genetic diversity is key to a species’ ability to respond to evolutionary challenges,” said Edmands. “And in the big picture, biological diversity — and the conservation of it — is important for many utilitarian reasons. Many pharmaceuticals begin as compounds isolated from ocean species, for example. But there’s a moral aspect to this, too. These species have been around for eons. What right do we have to extinguish any of them before their time?”

Considering the essential role marine microbes play in the ocean’s health — they form the base of the entire ocean food web, recycle nutrients and help balance the planet’s atmosphere — scientists like Fuhrman think that maintaining microbial diversity may be just as important as that of better-known marine life. Yet, understanding of microbial diversity lags decades behind what’s known about larger land and sea organisms, said Fuhrman.

“We’re still largely in the exploratory, discovery phase where we’re just trying to see what’s out there,” said Fuhrman, whose team has developed a number of new molecular identification techniques for bacteria, viruses and a distinct group of ancient microbes called Archaea.

Microbes make up some 90 percent of the biomass in the sea. Despite their abundance, the microbes’ small size, non-descript features and the fact that most will not grow in dishes in the lab have meant that the majority of species have eluded efforts to identify them.

Suzanne Edmands' studies of the genetic diversity of striped marlin populations will be used to better manage recreational and commercial marlin fisheries in the Pacific. Photo credit: Phil Channing Click here for high-resolution photo.

“It’s a major deal when someone finds a new species of fish, or even a new kind of worm. Now we are doing that every day. It’s just astounding,” said Caron, who studies protists, a group of single-celled microbes that includes marine algae and zooplankton called the protozoa. “Now, instead of just looking at these microbes under microscopes, we’re looking at genes to identify species.”

Adding to their interest is that they have “no clue” about many of these new microbes’ morphology, physiology or ecological role, said Caron, a professor of biological sciences in the College.

Their project piggybacked on the USC Wrigley Institute’s San Pedro Ocean Time Series, an ongoing study led by Anthony Michaels, professor of biological sciences and director of the Wrigley Institute. The Time Series allows institute scientists to study long-term changes in environmental factors such as temperature, salinity, nutrient concentrations and ocean ecology at a spot in the San Pedro Channel, about halfway between the coast and Catalina Island.