Damage to Threatened Gulf of California Habitats Can Be Reversed

Once described by Jacques Cousteau as the "world's aquarium," the marine ecosystems of the Gulf of California are under threat. Destructive new fishing methods are depleting the sea's habitats, creating areas that are ghosts of their former existences (see Scripps explorations story "Threatened Gulf."But, as Octavio Aburto-Oropeza of Scripps Institution of Oceanography at UC San Diego described during a presentation at the 2010 American Association for the Advancement of Science (AAAS) annual meeting in San Diego, habitat conservation can revitalize once-depleted marine ecosystems.One recently emerging threat is a highly destructive fishing method called "hookah" diving in which fishermen use crude oxygen piping to walk along the seafloor for long periods. The technique is typically conducted at night when fish are resting, allowing the hookah fishermen to spear or grab large numbers of vulnerable fish and invertebrates.Aburto-Oropeza's findings on reversing the effects of such threats are part of a series of research studies headed by the newly launched Gulf of California Program based at Scripps Oceanography."In these studies, whether reefs or mangroves, we are trying to show that the destruction on the coast and overexploitation in other areas are diminishing the biomass (the amount of organisms in an ecosystem) in several areas," said Aburto-Oropeza. "With lower biomass, the large predators, the keys to a robust marine ecosystem, are missing and that causes disruption down the marine food web."But there is hope to counteract such damage, says Aburto-Oropeza.One successful example is Cabo Pulmo, a little-known protected area near the southern tip of the Baja peninsula that is thriving and a living example of the benefits of protected marine areas. Restricted of fishing since 1995, Cabo Pulmo features a robust mix of sea life and flourishing fish populations. Other successes include Coronado Island inside the Loreto marine park and Los Islotes inside Espiritu Santo marine park."Different sites recover in different ways, but they all have increased in biomass, especially top predators," said Aburto-Oropeza."The common thing is that they have reduced or eliminated fishing activity."Beyond simply shielding certain locations, Aburto-Oropeza's presentation will cover new research that reveals the strategic importance of protecting areas that are key for fish species populations. In particular, these include important sites such as fish "spawning aggregation" areas, where fish converge in large numbers to reproduce at select times of the year, and sensitive nursery habitats that are vital to ensuring healthy ecosystems."For some species these spawning aggregation events occur two to four times per year, and can represent 100 percent of the replenishment of their populations," said Aburto-Oropeza.Aburto-Oropeza and others recently calculated the economic value of mangroves at roughly $37,500 per hectare per year. An ongoing study has shown that a fish species called gulf corvina provided 3,500 tons of landings in 2009 in one community, a volume worth $3 million.These studies have been supported by the David and Lucile Packard Foundation, Walton Family Foundation, Pew Foundation, International Community Foundation and Fondo Mexicano para la Conservación de la Naturaleza.

Invasive Species Threaten Critical Habitats, Oyster Among Victims

A study of oyster reefs in a once-pristine California coastal estuary found them devastated by invasive Atlantic Coast crabs and snails, providing new evidence of the consequences when human activities move species beyond their natural borders.Led by marine biologist David L. Kimbro, now of The Florida State University Coastal and Marine Laboratory , the study shows that in Tomales Bay , half the population of California's native Olympia oyster has perished because its habitat has fallen victim to the dysfunctional relationship between native species and non-native ones accidentally introduced.The work of Kimbro, a postdoctoral associate at the FSU lab, and colleagues from the University of California-Davis and its Bodega Marine Laboratory has magnified concerns that predator-prey mismatches between native and exotic species may lead to further losses of critical habitats that support marine biodiversity and ecosystems."What David Kimbro's research reveals about California's Olympia oyster raises a specter for Florida as well," said Felicia Coleman, director of the FSU Coastal and Marine Laboratory."First, our state has a remarkably productive native oyster population at risk in the Apalachicola Bay ," she said. "These oysters are sustainably harvested and provide critically important settlement habitat for an amazing array of species, so its loss would be devastating. Second, we know that in Florida's benign climate, exotic species are pretty easily established. One need only follow the trajectories of lionfish, Australian pine, Brazilian pepper and Burmese python for a grim view through the looking glass."Their study is expected to help guide habitat management and conservation efforts, including plans now being drawn up along the West Coast to restore native oysters."We've identified what my California colleagues call 'an important restoration bottleneck,' the attack on oysters by invasive species, which must be dealt with prior to undertaking oyster population enhancement and the rebuilding of remnant reefs," Kimbro said.In California, said Kimbro, the artificial predator-prey mismatch has allowed high numbers of invasive snails to destroy the biological diversity of Tomales Bay, a coastal estuary about 40 miles northwest of San Francisco, by consuming and eliminating oyster habitat.As an example, he points to the invasive European green crab from the Atlantic Coast (inadvertently introduced from Europe, so an exotic species even there). Smaller than California's native crab, it is less effective at controlling the snail population because it uses only brute force to kill its prey -- unlike its native counterpart, which is capable both of crushing the snails and using its claws like a can opener to peel open hard-to-crush larger shells.Ecological consequences are profound when the species most affected by a predator-prey mismatch is a "foundation species" that supports biodiversity by creating extensive habitat, such as California's native Olympia oyster (Ostreola conchaphila), which provides critical nursery habitat for a suite of species including crabs, anemones and fishes.Although Olympia oyster reefs are normally preyed upon by native predatory snails, said Kimbro, they are somewhat protected by the presence of native rock crabs that both consume native snails and force all others to spend more time hiding from crabs -- rather than eating the oysters.But when Atlantic snails and crabs invade, the whole dynamic changes."You'd think similar-looking invasive and native species could be swapped in a system without adverse effects," he said. "But we have shown that, functionally, this is not the case."In Tomales Bay, the exotic species occupy its inner reaches, where saline levels are lower. However, native predators cannot tolerate the inner bay's lower salinity, so they can't help to check the invasive snail population proliferating there. The invasive crabs are stuck in the inner bay because the natives hold the middle, with its higher salinity. Once upon a time, native oysters enjoyed a release from predation in the inner bay -- that is, until the invasive species moved in."While native predator-prey interactions that benefit oyster reefs are intricate and took a long time to develop, the invasive crab and snail don't have the historical exposure necessary to recreate these important interactions," Kimbro said. "A fellow researcher likened the native crabs and snails to a long-married couple who have learned to coexist, leaving oyster populations intact. But the lack of experience the invasive crabs and snails have with each other has led to the destruction of parts of the oyster population, much as an incompatible couple might destroy an entire family."Journal reference:Kimbro et al. Invasive species cause large-scale loss of native California oyster habitat by disrupting trophic cascades. Oecologia, 2009; 160 (3): 563 DOI: 10.1007/s00442-009-1322-0 Florida State University

DNA Used To Study Migration Of Threatened Whale Sharks

Whale sharks -- giants of the fish world that strike terror only among tiny creatures like the plankton and krill they eat -- are imperiled by over-fishing of the species in parts of its ocean range.

That threat is underscored in a new study from geneticists led by Jennifer Schmidt, University of Illinois at Chicago associate professor of biological sciences, reported online April 7 in the journal PLoS One.
Schmidt and her colleagues studied the DNA of 68 whale sharks from 11 locations across the Indian and Pacific Oceans and the Caribbean Sea -- an area that covers most of the shark's known range. Results showed little genetic variation between the populations, which indicates migration and interbreeding among far-flung populations of the big fish.
"Our data show that whale sharks found in different oceans are genetically quite similar, which means that animals move and interbreed between populations," said Schmidt. "From a conservation standpoint, it means that whale sharks in protected waters cannot be assumed to stay in those waters, but may move into areas where they may be in danger."
A tropical fish that can grow 50 feet or longer and weigh over 20 tons, a whale shark's range can span oceans. They do not breed until they are about 25 to 30 years old, so it will take a long time for the species to recover from recent population declines.
Whale sharks are listed as threatened, but not every country protects them. The large animals are especially prized by fishermen for meat and fins used in soup.
Little is known about the shark's biology, perhaps because they have been studied primarily near shore, while mature animals may breed and give birth out in the open ocean. Nor is much known about neonatal or juvenile sharks, including where they grow to maturity, or how and when they move between regions. That has made devising effective conservation efforts a problem.
"The only real threat to whale sharks is us," said Schmidt. "To design proper conservation plans, we need to understand the sharks' lifestyle. We can only protect their habitat if we know what habitat they use."
Schmidt credits some countries for closing whale shark fisheries and hopes that efforts such as ecotourism programs, which sometimes include swims with the gentle giants, may prove an attractive economic alternative to fishing.
With the money brought in by well-managed ecotourism programs, Schmidt said, "people in many countries have come to realize that whale sharks are more valuable alive than dead."
The research was funded by UIC and the Shark Research Institute in Princeton, N.J.
Other authors of the report include Marie Levine, executive director of the Shark Research Institute; Mary Ashley, professor of biological sciences at UIC; and Kevin Feldheim, director of the Pritzker Laboratory at the Field Museum in Chicago.
Journal reference:
Jennifer V. Schmidt, Claudia L. Schmidt, Fusun Ozer, Robin E. Ernst, Kevin A. Feldheim, Mary V. Ashley, Marie Levine. Low Genetic Differentiation across Three Major Ocean Populations of the Whale Shark, Rhincodon typus. PLoS ONE, 2009; 4 (4): e4988 DOI: 10.1371/journal.pone.0004988
Adapted from materials provided by University of Illinois at Chicago.

Leatherback Turtle Threatened By Plastic Garbage In Ocean

Leatherback turtles, the most widely distributed reptiles on Earth, are threatened with extinction themselves, in large part due to the carelessness of humans. A Dalhousie University professor addresses the threat of plastics to this endangered species.They survived the extinction of the dinosaurs. They're descendants of one of the oldest family trees in history, spanning 100 million years. But today leatherback turtles, the most widely distributed reptiles on Earth, are threatened with extinction themselves, in large part due to the carelessness of humans.We've seen reference to the dangers plastic poses to marine life, garbage that we humans directly and indirectly deposit in the oceans, but how clearly have we received the message? Not well enough according to a recent article in the journal Marine Pollution Bulletin co-authored by Dalhousie University's Mike James."We wanted to see if plastics ingestion in leatherbacks was hype or reality," says Dr. James, senior species at risk biologist for Fisheries and Oceans Canada and adjunct professor with Dalhousie's Department of Biology."It was a monumental effort that looked back at necropsies over the last century from all over the world," he explains. (Necropsies are post-mortem examinations performed on animals.) "After reviewing the results of 371 necropsies since 1968, we discovered over one third of the turtles had ingested plastic."Since leatherbacks prefer eating jellyfish, it's widely believed they mistake bags or other plastics for their meals. Since jellyfish and marine debris concentrate where ocean water masses meet, leatherbacks feeding in these areas are vulnerable to ingesting plastic.Once leatherbacks ingest plastic, thousands of spines lining the throat and esophagus make it nearly impossible to regurgitate. The plastic can lead to partial or even complete obstruction of the gastrointestinal tract, resulting in decreased digestive efficiency, energetic and reproductive costs and, for some, starvation."Plastics ingestion doesn't always cause death, but there are clearly health risks to the turtles," says Dr.James.Fascinated by reptiles as a child, Dr. James developed a lifelong interest in turtles, from raising them as a kid, to his PhD research and now as a biologist and conservationist. He says there are simple ways to stop these ongoing threats."The frustrating, yet hopeful aspect is that humans can easily begin addressing the solution, without major lifestyle changes," says Dr. James. "It's as simple as reducing packaging and moving towards alternative, biodegradable materials and recycling."Leatherback turtles are classified as critically endangered world-wide. The true population size is not precisely known, as only adult females come ashore for nesting in remote tropical locations. During the summer and fall, Canadian waters support the highest density of foraging leatherbacks in the North Atlantic.Journal reference:Mrosovsky et al. Leatherback turtles: The menace of plastic. Marine Pollution Bulletin, 2009; 58 (2): 287 DOI: 10.1016/j.marpolbul.2008.10.018 Source: Dalhousie University

Noisy oceans 'threaten sea life'

Some whales show damage suggesting they surfaced too quickly, experts say Increasing noise pollution in the world's oceans is threatening the survival of whales and dolphins, a UN-backed conference has heard. Experts say the noises sea creatures use to communicate are being drowned out by noises from commercial shipping, new military sonar and climate change. They become disoriented, cannot find mates or food and behave differently, scientists say. Suggestions to cut noise include installing quieter engines. The Convention on the Conservation of Migratory Species of Wild Animals, which representatives from 100 countries are attending, is considering issuing a resolution that would oblige countries to reduce sound pollution. 'Cocktail party' Other suggested measures include re-routing shipping, cutting speed and banning tests and sonar use in the habitats of endangered animals. Describing the increasing noise in oceans, Mark Simmonds from the Whale and Dolphin Conservation Society said: "Call it a cocktail-party effect: you have to speak louder and louder until no-one can hear each other anymore." He said there were a growing number of cases where the stranding of whales and dolphin could be linked to sound pollution. In some cases, the mammals had tissue damage similar to divers who surface too quickly, leading scientists to suggest that they were scared by military sonar or seismic testing, and surfaced beyond their physical limits, he added. Other research suggests that rising levels of carbon dioxide are increasing the acidity of the Earth's oceans, making sound travel further through sea water. According to a report by the International Fund for Animal Welfare, the distance over which blue whales can communicate has been cut by 90% as a result of higher noise levels over the last 40 years. A spokesman for the UN Environment Programme said governments seem ready to take action to alleviate the problems caused by noisy oceans. BBC News

Ocean Life Under Threat From Climate Change

"Marine ecosystems are undoubtedly under-resourced, overlooked and under threat and our collective knowledge of impacts on marine life is a mere drop in the ocean," wrote Dr Anthony Richardson, from The University of Queensland and CSIRO, and his co-author, Dr Elvira Poloczanska from CSIRO in Hobart."There is an overwhelming bias toward land-surface studies which arise in part because investigating the ocean realm is generally difficult, resource-intensive and expensive," they said. The disparity in focus on land-based compared to marine impacts was highlighted in the Intergovernmental Panel on Climate Change's (IPCC's) Fourth Assessment Report (2007), which included 28,500 significant biological changes in terrestrial systems but only 85 in marine systems.The paper argues that the collection of marine environment data over 20 years or more – a requirement for inclusion in IPCC assessments – suffered in the mid-1980s due to government funding cutbacks for international marine science research, just as ocean warming began accelerating.The authors advocate change in the existing IPCC process to better assess the impacts."Climate change is affecting ocean temperatures, the supply of nutrients from the land, ocean chemistry, food chains, shifts in wind systems, ocean currents and extreme events such as cyclones," Dr Poloczanska said. "All of these in turn affect the distribution, abundance, breeding cycles and migrations of marine plants and animals, which millions of people rely on for food and income. Development of the Integrated Marine Observing System, announced in 2006, is an important step forward but securing data over the time scales relevant for climate assessment will not occur until near 2030."Dr Richardson said the situation is made more urgent as emerging evidence suggests marine organisms may be responding faster to climate change than land-based plants and animals. "As the climate is warming, marine plants and animals are shifting towards the poles and their timing of peak abundance is occurring earlier in the year," he said. "The slower dynamics of the ocean also means that some changes such as ocean acidification will be irreversible this century."While understanding impacts of climate change in the oceans is important, ultimately we need to develop adaptation options as the knowledge-base expands," Dr Richardson said.Source: University of Queensland