Scientists at this year's American Association for the Advancement of Science annual meeting in Boston unveiled the first comprehensive global map of humanity's cumulative impact on the oceans.

According to the new study, which is the first to integrate multiple drivers of current human impact on oceans, the ocean is confronting a "multi-jeopardy" situation. “The water is becoming warmer, circulation patterns are changing in unpredictable ways, and oceans are becoming acidic,” says Gretchen Hofmann, a molecular physiologist at the University of California, Santa Barbara.

The study concludes that there is no oceanic area unaffected by human influence. Combined factors including over-fishing, coastal development, shipping traffic, and pollution run-off, threaten the existence of marine organisms in many ways, and make our impact on the oceans very complex. Scientists, in recent months, have also reported the giant "dead zone" off the coast of Washington is expanding, not to mention the vast islands of plastic trash forming in the Pacific.

The complexity of the ocean environment also complicates the research being conducted by scientists to study and monitor marine species.

Forty-one percent of the oceans are strongly affected, particularly just offshore in the Eastern Caribbean, the North Sea, the Japanese waters. Only a mere four percent is relatively pristine, such as in northern Australia, the Torres Strait, and the poles.

Given the vastness of ocean affected, scientists predicted an alarming amount of disruption in the ocean's physical, chemical and biological patterns, not to mention the decline of socio-economic ecosystem "services" provided by the earth's oceans.

Climate Change and the Ocean
Geochemically, the oceans naturally absorb atmospheric carbon dioxide to maintain carbon equilibrium with the atmosphere, which can then dissolve into carbonic acid or other carbon ions. In the presence of steeply increasing anthropogenic greenhouse gases, oceans are acidifying much faster than the IPCC or any model previously predicted - as is the melting of Arctic sea ice and sea level rise.

“Ocean acidification harms plants and animals that form shells from calcium carbonate, like corals, pteropods and lobsters,” says Scott Doney of the Woods Hole Oceanographic Institution. Many of these organisms provide critical food sources or habitats for other organisms and the impact of acidification on food webs and higher trophic levels is not well understood.

Professor Hofmann, who studies tiny marine snails called pteropods, says “It’s possible by 2050 they may not be able to make a shell anymore.” Since pteropods are one of the most widely eaten organisms in the ocean, she claims, “If we lose them, the impact on the food chain will be catastrophic.”

As some species dissolve, others may become displaced by changing currents. With rising global mean temperatures, a heat imbalance may cause a shift in currents resulting in a series of feedback loops. For instance, freshwater influx from melting ice could trigger a halting of the Thermohaline Circulation, which transfers surface waters to the deep oceans like a conveyor belt. Since this current is linked to the Atlantic Jet Stream, changes in weather patterns in the Northern Hemisphere could reduce upwelling zones that are critical for fish-feeding grounds.

Even modest warming of a degree or two above normal maximum temperatures can cause a massive epidemic to the most threatened of all marine ecosystems—coral reefs. “Temperature increase can break down the relationship between corals and their symbiotic algae, zooxanthellae, causing coral to ‘bleach’ and grow more slowly,” said Nancy Knowlton, a marine biologist with the Smithsonian Institution.

In addition to acidification and warming, many unpredictable changes from global warming may further complicate the ocean’s feedback system. Ocean hypoxia, for instance, which usually occurs from excessive agricultural run-off, is now also becoming a climate-driven occurrence. These low-oxygen dead zones, which have doubled in number every decade, have taken global upwelling zones by surprise. In the U.S., since 2000, hypoxia events have plagued coastal upwelling zones in the Northwest Pacific.

Jack Barth, an oceanographer at Oregon State University, believes these unprecedented hypoxia observations are most likely linked to stronger, more persistent winds blowing off heated landmass, that are expected to occur with global warming. Because the winds don't go slack as they used to do, the upwelling is prolonged, producing a surplus of phytoplankton that isn't consumed. This unused biomass decays and creates a surge in oxygen-depleting bacteria and algae.

Collapsing Global Fisheries
Although the oceans changing feedback system threatens global fish populations—over-fishing and aquaculture may in fact get around to sinking fisheries first, say experts.

A Science report in 2006 initially predicted a global fisheries collapse by 2048, assuming fishing around the world continues at present rate and nothing is done to mitigate the problems.

Of particular concern amongst AAAS Panelists, are the fate of large predators, like tuna and sharks. The numbers of many large shark species have declined by more than half since 1970 due to increased demand for valuable fins in the shark fin trade. For large coastal shark species, the declines were much greater: tiger, scalloped hammerhead, bull and dusky shark populations have all plummeted by more than 95 per cent.

High value fisheries, like tuna, are also in extreme decline. Bluefin tuna, for example, in the western Atlantic have suffered a 90 percent drop in population since the 1970s. One of the biggest reasons why species like bluefin, bigeye and yellowfin tuna are in decline is due to significant juvenile by-catch.

Developed countries like the U.S. and Japan have technologically advanced long-line fishing fleets that enable them to harvest adult yellowfin tuna, highly valuable and popular with the Japanese sushi market. Developing countries such as the Philippines, however, have less advanced fleets that target skipjack using purse-seiners and fish aggregating devices while trapping juvenile yellowfin as by-catch.

“This hurts the economy and impacts the species,” said Jose Ingles of WWF-Philippines. “If juvenile fish are allowed to mature, they would be worth more than $1.5 billion annually–significantly higher than the $236 million currently derived from juvenile catch.”

Satellite Solutions?
Luckily, Scientists have developed methods to help reverse fish decline trends. For instance, new cooperative management agreements between juvenile and adult tuna catching nations could result in win-win outcomes for local economies, future generations of people and fish. An economist from the University of British Columbia’s states, “This approach could have prevented the depletion of cod stocks off Newfoundland and such balancing can reduce the chance of a similar fate befalling the tuna stocks of the Coral Triangle.”

Scientists at the AAAS meeting also argue that marine reserves need to become large enough to include healthy populations of top predators.

Furthermore, they claim that high-tech solutions involving vessel and fish monitoring via satellite may be the best--if not the only--way to monitor the high seas.

Michael Behrenfeld, an oceanographer from Oregon State University who studies phytoplankton says, “Using NASA satellites, we can track changes in phytoplankton on a global basis and what we find is that warming ocean temperatures are linked to decreasing photosynthesis. Satellites are one of the most important tools we have for understanding the link between climate and ocean biology because they provide measurements of the whole planet on a daily basis, which could never be accomplished by ship.

Even actions like bottom trawling, the world’s most destructive industrial fishing method - whereby large, heavy nets are dragged across the sea floor, stirring up huge, billowing plumes of sediment - can be monitored from space, says Dr. Elliott Norse, President of Marine Conservation Biology Institute in Bellevue WA.

“Unfortunately,” Behrenfeld adds, “it is at this very time when we need satellites most that we are facing the end of NASA ocean biology satellites because of budget cutbacks or new priorities. “This is a serious issue that needs to be addressed.”

“Instead of facing the end of these critical missions and becoming blind to the changes occurring in our oceans,” Behrenfeld said, “we should be building even better ones to see more clearly than we have in the past, and to gauge the potential consequences of climate change on ocean productivity.”

New approaches also need to be developed to foster recovery. "Some progress has been made but there is a long way to go,” says Dr. Gary Rosenberg.

A New Eco-System Approach
Some of these latest approaches range from the continued refinement of fishing privileges to the emerging, all-encompassing method of “ecosystem-based management” of ocean resources. Ecosystem-based management seeks to tie the disparate ocean-related puzzle pieces together so that policies put in place can be most effective when confronted with the inevitable trade-offs between ecosystem “services” – from seafood to erosion control to recreation.

WWF’s Katharine Newman further states, “We need to find solutions that advocate sustainable fishing starting right at the source like the Coral Triangle down to consumers’ plates through MSC certification and public awareness.”

In addition, scientists claim we also need to resolve the growing problem of pesticides, nuclear contamination, and PHAs (polycyclic aromatic hydrocarbons from fossil fuel contamination) impacting aquatic life and possibly human health.

Bagging Carbon at the Bottom of the Sea?
Restoring global fisheries will have to overcome many hurdles before achieving global cooperation, realistic monitoring, and accurate management. But compared to resolving the issues associated with climate change, they seem fairly tangible.

The causes of anthropogenic climate change are broad and often difficult to address. Although numerous opportunities exist for reducing greenhouse gas emissions, the solutions are complex due to lack of global carbon controls and abundance of cheap, highly available fossil fuels.

One of the most optimistic, attention-grabbing—yet controversial—carbon mitigation ideas at the AAAS meeting, came from Dr. David Keith, one of Canada’s foremost experts on carbon capture and sequestration, who promotes ‘contained carbon sequestration’ in the ocean. Each carbon containment bag, which look like giant sausages measuring up to 100 meters in radius, and several kilometers long, would “benignly rest on the seabed 3 kilometers below the ocean’s surface. They are capable of storing 160 million tons of CO2 each -- the equivalent of 2.2 days of current global emissions." Keith claims the use of containment is necessary since dissolved CO2 in the ocean could adversely impact marine ecosystems.

"Fortunately," says Keith, "The cost of containment is quite minimal with this solution." He and his colleagues calculate that the bags can be constructed of existing polymers for less than four cents per ton of carbon.

Even despite the fact that anything could tear this giant polymer bag, not to mention the many costs associated with transporting CO2 to the deep ocean, he still claims, “Ocean storage might be an important option for reducing CO2 emissions.”

Photo courtesy of Chris Seufert, via Grist.