Nursery Areas at Risk
The massive oil release in the Gulf of Mexico, officially referred to as the Deepwater Horizon Incident, is receiving worldwide attention and will result in long-lasting environmental impacts. Some of the impacts, including the harm to shore birds, the spoiling of coastal wetlands and the short-term cessation of several major fisheries, are painfully familiar to the public.
The coastal wetlands of the Gulf of Mexico account for the vast majority of this crucial habitat in the United States. (Those wetlands in Louisiana alone account for nearly a third.) They provide food and haven for wildlife and nourish finfish and shellfish populations that provide many of our country’s most important commercial and sport fisheries. Reductions in the ecosystem services provided by these productive and vital wetlands will be felt for years to come.
Impacts are also occurring well below the surface. The oil from the damaged Deepwater Horizon drilling site is mixing with Gulf Coast waters nearly a mile below the surface. Massive deepwater plumes of oil droplets have been detected, but it’s much harder to gauge their extent than it is to measure the size of oil slicks on the surface. Moreover—like most things associated with the deep sea—scientists know far too little. How much of it will remain suspended in deep water or end up on the sea floor? How long will it remain there? How will microorganisms, fish, and other animals exposed to this toxic brew fare? Will bacteria that feed on these newly abundant hydrocarbons deplete oxygen levels and create more dead zones?
The National Academy of Sciences has put together an online resource page about the Deepwater Horizon oil spill and its impact on the environment.
Source: The Academy of Natural Sciences http://www.ansp.org/deepwater-horizon/index.php
The Chesapeake Bay is one of the world’s largest, and formerly most productive, estuaries. The Bay and its tributaries sustain a wide variety of species (nearly 300 known species of fish and approximately 3000 aquatic species of plants and animals in total). This biological richness has long been tapped by humankind; commercial and recreational fishing has gone on for centuries. Unfortunately, both environmental degradation and overfishing have contributed to the ecological decline of the Bay, impairing the many ecosystem services that it once provided. Not least among these functions is the provision of nursery areas for a wide variety of fish, crabs, oysters, and other marine organisms. The nursery function of the Chesapeake is not restricted to marine life continuously living within it – many coastal species traveling up and down the eastern seaboard rely on the seagrass beds and oyster reefs to protect their vulnerable young.
In the 1600s when Captain John Smith sailed into the Bay, he was struck by the beauty and bounty around him. In the logs of his explorations, he recorded transparent waters, vast meadows of underwater grass, extensive oyster beds, and abundant fish. Today the Chesapeake operates at barely one-fourth of its historical potential, with marked declines in overall productivity and almost complete extirpation of oysters, shad, and red drum. Blue crabs, a target species of the colorful, iconic Bay Watermen, were almost eliminated in the 1980s and are only slowly recovering. Even if the population does eventually recover fully, it will have been too late for many of the Watermen, whose livelihoods could not survive the decades long environmental decline of the Chesapeake.
The Bay region is subjected to a wide variety of negative impacts caused by land and water use. Habitat conversion due to coastal and urban development along the tributaries and along the coastline of the Bay itself has led to a massive decline in seagrasses and other critically important nursery habitats. Excessive nutrients (especially nitrogen, but also phosphorus) from farming within the watershed and from untreated sewage have caused eutrophication and algal blooms, including the alarming incidence of toxic Pfisteria. Other forms of pollution, including massive heavy metal loading, pesticides, herbicides, hydrocarbons, and debris have killed and sickened the Bay’s resident species and have contaminated its sediments. Overexploitation of oysters has led to the destruction of oysters reefs, which in turn serve as nursery areas for many fish, mollusk, and crustacean species. Overfishing other marine life such as shad, blue crab, bluefish, red drum and tautog has stressed the system even further.
There are some hopeful signs of recovery, however. The Chesapeake Bay Foundation, started 35 years ago, and other government agencies and environmental groups have made restoration of the Chesapeake a high priority. Watchdog groups monitor the condition of the Bay, as well as new development along its shores and watershed areas. Education programs in the greater Bay region teach the importance of stewardship of the Bay, and the consequences of damaging activities like pouring poisons into storm drains. During 2002, seagrasses made a significant recovery in the extent of their cover – thought to be the result of the extended drought and consequent decline in run-off. Scientists and conservationists warn, however, that when this drought ends, rainfall will cause run-off of large amounts of accumulated toxins, potentially shocking the Bay with the sudden influx of pollutants. Stronger policies to preserve the bay and control run-off may offset some of these impacts. Chesapeake 2000, the new Chesapeake Bay agreement signed by federal, state, and local officials in June of 2000, outlines ways to recover the health of the Bay while securing $8.5 billion in federal support for restoration and mitigation of further impacts on this precious ecosystem, and serves as a model for regional cooperation to conserve critical coastal areas in the United States.
Source: Chesapeake Bay Foundation http://www.cbf.org; Chesapeake Bay Program http://www.chesapeakebay.net/bayresourcelibrary.aspx?menuitem=13998,. US Fish and Wildlife Service Chesapeake Field Office www.fws.gov; NOAA http://chesapeakebay.noaa.gov; University of Maryland http://mdsg.umd.edu/CQ/V06N1
In the United States, one of the ecosystems most severely affected by biological invasions can be found in California. San Francisco Bay, an estuary protected from the dynamic Pacific Ocean, has been drastically altered by invasive species that have settled in over the past 130 years. The bay once had rich fishing waters for prized catch such as oysters, shrimp, Pacific salmon and Dungeness crab. Today, the native species of the bay are greatly outnumbered by more recent arrivals.
The transformation of the bay is the result of many factors. In 1899, after the completion of the transcontinental railroad, trains brought live oysters from the east coast to the bay for cultivation. The oysters were unable to adapt to their new home, but other organisms that traveled with the oyster clusters thrived. As California's population grew, and demands on the land increased, agriculture runoff and industrial pollution degraded the system and enabled invasive species to outcompete stressed native species.
San Francisco is a thriving international port, receiving shipments from locations around the world, including stowaway organisms in ballast water. In1985, a species of clam native to Asia appeared in the upper region of the bay, likely the result of larvae stowing away in freighter ballast water. Today, the floor of the bay is carpeted with these creatures, with more than 10,000 clams per square meter in some places. Asian clams are eating the food sources of two species that utilize the Bay as nurseries: salmon and striped bass. To complicate an already complex situation, another invader was found in southern San Francisco Bay in 1990. The European green crab, a small but voracious crab with a hearty appetite for oysters, clams and mussels, has since spread throughout the bay. Alien species of hydrozoans feed on crab zoea larvae and other small crustaceans that rely on the Bay’s nursery areas. The rapid growth of these and other invasives is an environmental concern because of the major negative impacts on native shellfish and other invertebrates.
There are now more than 200 non-indigenous species of organisms in the San Francisco Bay. Many of the species have arrived in a surprising way: transported in the seaweed used to pack bait for recreational fishing that originates in other coastal areas. Sea slugs from New Zealand and jellyfish from the Black Sea are just a few of the recent arrivals that have joined the alien menagerie in the bay. The nursery habitats of the bay have become less productive as a result, and decline in commercially valuable and ecologically important native species continues.
Success Stories: Protecting Crucial Marine Nursery Areas
The Merritt Island National Wildlife Refuge at Cape Canaveral, Florida, has the oldest fully protected marine reserve in the US, comprising two estuaries (Banana Creek, 16 square kilometers in size and North Banana River, 24 square kilometers in size) that were closed the public in 1962 to protect the security of the Kennedy Space Center. In the protected area, relative abundances of gamefish such as black drum, red drum, spotted sea trout, and common snook, were found to be much higher (2-13-fold increases) than in adjacent unprotected areas. World-record fish catches registered by the International Game Fish Association show that, although the area adjacent to the reserves encompasses only 13% of the Florida coast, it accounts for over 50% of world record-size black drum, red drum, and spotted sea trout caught in Florida between 1939 and 1989. The frequencies of these records have increased over time, as would be expected if the refuge were supplying fish to the adjacent recreational fishery. Since 1985, all of the new Florida records for black drum, and most for red drum, have been won for fish caught adjacent to the refuge. The lag before seeing these record-breaking fish can be explained by the time it took for fish to grow to record-breaking size once the refuge was established.
Source: Stevens, P.W. and K.J. Sulak. 2001. Egress of adult sport fish from an estuarine reserve within
The Tampa Bay Watershed supports a human population of about 2 million within the cities of Tampa, St. Petersburg, Clearwater, Bradenton, and their suburbs. In 1954, the U.S. Public Health Service first pointed out the bay’s decline, citing untreated sewage and industrial wastes from phosphate mines and citrus canneries as major contributors. In the early 1970s, a citizens group called Save Our Bay began to push for a halt to dredging and sewage disposal in the bay. Tampa had for decades been piping raw sewage into Tampa Bay, and many portions of the bay were badly polluted and were experiencing continuous blue-green algae blooms. The newly formed US Environmental Protection Agency awarded Tampa a grant to upgrade its sewage treatment plant, and in 1979 Tampa installed an advanced wastewater treatment system, reducing the flow of nitrogen into the bay by an estimated 90%. St. Petersburg, taking a different approach, pioneered the first large-scale wastewater reuse program in the state, which also greatly reduced the discharge of nitrogen to the bay. Once the nutrient reduction occurred, , it took five years to see a decline in algal blooms and an increase in water transparency.
The Tampa Bay estuary, comprising mangrove forests, saltmarshes, and seagrass meadows, has been a major seaport for over 100 years yet continues to support a diversity of marine organisms, including fish, crustaceans, sea turtles, and marine mammals. Coastal development (including port construction) resulted in the excavation or filling of over 40% of the tidal marshes and mangrove forests. Seagrass meadows, which originally covered about 300 square kilometers of the shallow bay bottom, were reduced by the early 1980s to about 88 square kilometers. Citizen action groups, beginning with the first Earth Day in 1969, eventually worked with government to help create an Integrated Coastal Management program that defined what types of sewage treatment should be applied and specified water quality parameters to be achieved. Eventually they used seagrass distribution as their standard. Bay-wide seagrass mapping has been conducted every two years since 1988, showing that the trend of seagrass loss has been reversed. Currently, the Tampa Bay National Estuary Program is working to protect existing seagrass meadows and to restore 5000 hectares of additional seagrass, primarily through controlling nitrogen input into the bay. It is also constructing tidal platforms to encourage the regrowth of marshes and mangroves, and has found that fish populations characteristic of such wetlands appear within five years of the platforms’ construction.
The struggle to protect and manage the natural resources and nursery habitats of Tampa Bay has evolved in less than thirty years from a grass-roots citizens effort to a network involving three counties, a dozen cities, a variety of regional and federal agencies and many citizens and special interest groups. Citizen involvement and concern remain important driving factors in creating long-term goals for bay restoration.
Source: Lewis, III, R.R. et al. 1998. The rehabilitation of the Tampa Bay Estuary, Florida, USA, as an example of successful integrated coastal management. Marine Pollution Bulletin 37(8-12):468-473.
Coral reefs in the Philippines are being rapidly degraded. Studies by Angel Alcala and Gary Russ provide a historical perspective on a few cases where this degradation has been halted (summarized in Russ et al., 1999). In 1974, a marine park with a no-take reserve was established around Sumilon Island. Goals included protecting fish habitat, increasing fish yield in nearby fishing areas, and encouraging tourism. In the subsequent decades, protection waxed and waned as the political context changed. In the mid-1980s, the reserve was fished heavily and destructively with explosives and drive-nets (nets fixed to poles that catch fish by ‘scraping’ them off reefs, damaging the reefs in the process). Such fishing not only depleted fish populations but also acted to destroy nursery habitats. In 1987, the mayors halted fishing in the reserve to encourage the building of a tourist resort on the island, a decision that may have been made easier by the perception that the reserve had been “fished out.” All fishing was banned on the whole reef from 1988 to 1992, when the resort was completed. In 1992, fishers were allowed back, and the ‘no-take’ reserve was again fished regularly. The resort, incidentally, failed.
The on-again-off-again management of the Sumilon reserve provided a natural experiment for evaluating the efficacy of habitat protection using no take reserves. Yields increased from 1976 to 1983, when protections were in place. After the heavy fishing of 1985-1986, catch per unit effort and total yield in the area dropped by about 50%, supporting the contention that protective management had maintained higher abundances of fish in the reserves and significantly higher yields in adjacent, fished areas. After protections were reestablished in 1987, populations of heavily fished species rebounded, only to decline again when fishing resumed in 1992.
The story of Apo Island’s is different. Silliman University started a marine conservation and education program there in 1976. Six years later, the local municipality endorsed a no-take marine sanctuary consisting of about 10% of the island’s coral reef area, and in 1985 the municipality declared the entire reef a marine reserve. A committee of local residents was given responsibility to maintain the sanctuary and reserve. A marine education and community center, built with the university’s help, kept interest and commitment high among residents. The committee’s management objectives included: restricting fishing around the island to residents, maintaining the no-take sanctuary within the reserve, preventing the use of destructive fishing techniques, increasing local fish yield through export from the sanctuary to local fishing grounds, and encouraging tourism. Two small but successful eco-tourism resorts were established on the island, and have benefited the local economy. When local fishers were surveyed in 1992, all expressed a positive attitude toward the reserve and sanctuary and towards the committee that managed it, and said that their yields had increased since the reserve was implemented. In the Apo reserve, the density of large predatory species favored by fishers increased almost eight-fold between 1983 and 1993. Density and species richness of such fish also increased year by year in areas adjacent to the no-take reserve, suggesting that fish may be being exported from the reserve.
The element that distinguishes Apo’s success in managing its marine reserve from Sumilon’s inability to do so has been the continued strong support and involvement from the people who depend on the resources. In order for marine reserves to be more than just paper entities, local communities must be convinced of the benefits of management, and their support must be continuous and long-term.
Source: Russ, G.R. and A. Alcala. 1999. Management histories of Sumilon and Apo Marine Reserves, Philippines, and their influence on national marine resource policy. Coral Reefs 18: 307-319.
No-take marine reserves were declared in 1991 at Governor Island, Maria Island, Tinderbox, and Ninepin Point, on the eastern/southeastern Tasmanian coasts. Maria Island is the largest reserve, with about 7 km of coastline protected. Tinderbox, the next largest, has 2 km, while Governor Island and Ninepin Point protect about 1 km of coastline each. Reference sites were picked outside the reserves so that the effect of protection on reef assemblages could be compared with similar, unprotected reef. Surveys, conducted at least annually for five years, found that the number of fish and invertebrate species increased inside the Maria Island Marine Reserve relative to sites outside the reserve, but did not change significantly in the smaller reserves. Large fish became much more common at Maria Island than outside the reserve, partly because of an increase in size of the abundant blue-throated wrasse (Notolabrus tetricus), and partly because of an enormous increase in the abundance of the bastard trumpeter (Latridopsis forsteri) inside the reserve (no trumpeter at all were found at sites outside the reserve). Other large fish species such as ling and draughtboard shark, which had been virtually eliminated from heavily fished reefs, were found at Maria Island and Tinderbox. The density of large fish did not increase at the two smaller reserves.
Rock lobster numbers steadily increased in the Maria Island reserve, and the largest animals encountered inside the reserve increased by about 15 mm during each year of monitoring. Outside the reserve, numbers remained stable, and very few individuals exceeded the minimum legal size for the fishery. The total biomass of rock lobsters in the Maria Island reserve was estimated to have increased by more than an order of magnitude during the study, and total biomass of lobsters above legal size was estimated to have increased over twenty times. This trend to larger size was seen in all the reserves.
These increases in size and density should translate to increased reproductive output, since larger animals are more likely to be sexually mature, and numbers of eggs produced increases with body size. Whether the huge increase in reproductive potential actually translated into more juvenile recruitment into nearby fisheries was not directly tested, but the tendency for fishers to set nets and pots on reserve boundaries suggested that considerable export of adult fish and rock lobster did occur.
Studying these no-take reserves has shown that Tasmanian coastal reefs are capable of supporting much higher densities of rock lobster and commercially important fish than other areas, but have been heavily overfished. Current levels of fishing, which primarily target immature fish, are far in excess of maximum sustainable levels for the region.
Source: Edgar, G.J. and Barrett, N.S. 1999. Effects of the declaration of marine reserves on Tasmanian reef fishes, invertebrates, and plants. Journal of Experimental Marine Biology and Ecology 242: 107-144.