Humans may affect marine eco-systems, says scientist

By: Betsy Cohen

Posted: 11/19/08

11/19/08 - According to a scientist at last night's fall Honors Colloquium lecture, human impact is to blame for detrimental changes in the world's oceans.

Professor Jeremy Jackson of the Scripps Institute of Oceanography at the University of California, San Diego spoke to a packed Edwards Auditorium as part of a series, entitled "Human Effects on the Ocean and its Ecosystems."

Jonathan Garber, a University of Rhode Island Graduate School of Oceanography alumnus and coastal marine ecologist, introduced Jackson as a "scientist, advocate and communicator extraordinaire."

"Jackson is a world leader in the study of marine ecology and marine organisms - one of the world's outstanding marine ecologists," Garber said.

Jackson, who is working on the publication of his new book, "Brave New Ocean," brought a plethora of data and a sense of humor to the presentation.

"Can I do anything about it, or just stop and drink [away the problem]?" Jackson joked about the current marine ecological damage situation.

"People are the problem," Jackson said. "With every generation, we lose all concept of nature, or what natural is."

In his seminar, he addressed the fact that on a global scale, all large estuaries and essentially all coastal ecosystems are currently facing many issues, specifically a huge decrease in biodiversity.

He said many of the major human impacts on the oceans include overfishing, the destruction of ocean floor habitat (predominately done by trawling), the introduction of new species, the warming and acidification of the ocean, the poisoning of food webs and the rise of slime.

In regards to overfishing, an informative slide showed that the total biomass of fish in 1900, which included that of cod, pollack and haddock, was significantly greater than that of the total biomass of fish in 2000.

A second example Jackson gave were the numbers of green turtle nesting beaches. In 1492, 91 million green turtles were present in the Caribbean.

"That is more biomass than the animals in Africa," Jackson said. Today, he said the numbers dwindle at a rate lower than 300,000.

He also discussed how trawling results in the destruction of coral reefs.

"You can see the lines like corn fields" through the traveled area, Jackson said. Off the coast of New Mexico, trawls are conducted twice every year.

"The area of forests deforested by humanity is approximately the same amount as that of the area of trawled ocean floor," he said.

Non-native introduced species like the green algae Caulerpa taxifolia are becoming a serious problem in marine environments. The organism carpets the bottom of the Mediterranean Sea and smothers communities of native species. Caulerpa taxifolia "will soon pave this huge area in the Northwest Mediterranean," Jackson said.

Oceanic acidification results in mass mortalities of coral species because of coral bleaching and negatively affects the skeletal growth of calcifying organisms. Jackson defined coral bleaching as "the breakdown of mutualism between coral and its symbionts caused by high temperatures."

"All over the world, sites like this are becoming very common," he said.

Human activities have also led to the poisoning of food webs. When tested, mercury and other contaminants are frequently found to be present in marine organisms. Higher levels are most commonly observed in apex-level species, including humans. Jackson also noted Inuit mothers' breast milk contains dangerously high concentrations of toxins because of their seafood diet.

In recent years, wild salmon populations have been decreasing at alarming rates because of toxins in the Pacific Northwest waters.

Farmed salmon have even higher concentrations of toxins because of terrestrial feed. Faming deepwater fish is "just dumb, but it tastes good," Jackson joked. "It's an ecological disaster, the amount of blue fin tuna you have to kill to feed the blue fin tuna."

He also stressed that the quantity of human consumption is the issue, not population.

"Farming is just insane from an ecological point of view. It's hard to imagine as an American, European, Japanese, or Australian the population issue, when we consume [an enormous amount] of stuff [compared to] a person in Bangladesh," he said.

The increase of slime is the largest threat to the development of aquaculture. As the frequency of slime outbreaks continue to increase, so do the severity of toxic blooms and diseases that are responsible for wiping out entire species, populations and communities. Jackson also included various scenarios and consequences, as well as steps to rationally manage and conserve the world's oceans.

"It's really easy to break a marine ecosystem and it's really hard to put one back together again," Jackson said.

Libby Miles, chair of the writing and rhetoric program and professor in the Honors Program, attended Jackson's lecture with her young daughter.

"We often don't notice what is happening in the ocean the way we notice devastation on the land," she said. "[The presentation] gives those of us in the Ocean State an idea of what we can not see, because it's underwater. I sensed that he sent everyone away wanting us to take charge in our lives, to make a difference. I think everybody really liked it."

Nora Eschenheimer, a freshman theater major who attended last night's colloquium as a part of Miles' Honors "Writing Around the Ocean State" course, also enjoyed the lecture.

"If everyone was presented with this information, then we'd all be activists," she said. "We'd all be passionate and involved in trying to make this country more environmentally aware. It's such a shame that not everyone has the opportunity to be exposed to this information."

The next lecture in the fall Honors Colloquium series will be Dec. 2 in Edwards Auditorium.