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Threats to Marine Ecosystems and Biodiversity 1. 2. 3. 4. 5. General Habitat Loss and Degradation Resource Extraction Species Invasions and Diseases Climate Change EXXON Valdez Oil Spill Trust Counciil; photolib.noaa.gov Source: NOAA General • Human pressures on coastal resources are compromising many of the ecosystem services crucial to the well-being of coastal economies and peoples • The greatest threat to coastal systems is development-related loss of habitats and services • Coastal ecosystems and islands face greater numbers of threats than others, because pressures are greater and because they are the downstream recipients of degradation from afar Habitat Loss and Degradation • The most serious consequences of biodiversity loss occur when changes are irreversible: e.g. habitat loss, species extinctions, population extirpations, regime shifts • The most important driver behind these large scale impacts on biodiversity is land conversion (including coastal/marine habitat loss) • The other drivers behind biodiversity loss differ in various ecosystems, and include overexploitation, pollution, and climate change Resource Extraction • Many fisheries exceed sustainable limits of use • The removal of small-scale heterogeneity associated with the homogenization of habitats is an important cause of the loss of biodiversity Source: T. Agardy • Both over-exploitation beyond sustainable levels and fishinginduced or coastal development-related habitat destruction are major issues NOAA Overfishing (= Intense Predation) • The global marine catch has increased more than four times in the past 40 years. • Overfishing has pushed many fish populations into steep declines. Catches are falling, even though fleets are fishing harder than ever before • The U.N. Food and Agriculture Organization (FAO) reports that seven of ten commercially targeted fish stocks are either fully or heavily exploited (44 percent), overexploited (16 percent), depleted (6 percent), or slowly recovering from previous overfishing (3 percent). Pillaging the North Atlantic: species and the year that > fishing effort = no increase in yield: ‘overfishing!’ C= cod H=haddock P=plaice R=redfish Hk=hake Hg=herring Ocean Fisheries • > 109 people (mostly developing nations) depend upon marine fish for primary source of protein • a 40 y ‘fishing boom’ has now ended: catch increasing steadily since 1950, but since 1989 world catch has stayed the same • catch of ‘high value’ fish decreasing; catch of low value fish increasing Exploitation of global fisheries Overfishing: Gear Impacts • Trawlers often scrape the same area several times each year. Sea-floor species can be crushed and displaced, and the types and availability of nutrients changed. – Sediments stirred up by trawling can make water a thousand times cloudier than normal, limiting resettlement and feeding of plants and animals Trawling Beam trawlhow to destroy benthic habitats Effects of scallop dredging on a gravel bottom: George’s Bank: 84 m depth Un-fished area Fished area 500 m away Frequency of trawling in some representative areas The rapid decline of the orange roughy fishery Red: est. biomass Blue: catch Overfishing: Continued • There is great difficulty in sustaining global fisheries production. In response to declines of big, slower growing species, fishers have begun "fishing down the food chain", targeting smaller species of less value, but which can play critical roles in food webs. • The most glaring crises of global fisheries include: – over-capitalization of the industry which has led to the buildup of excessive fishing fleets, particularly of the larger-scale vessels catching too many fish. Overfishing: Continued • Government subsidies enabled vessels to operate in conditions that are uneconomic and environmentally unsound. Fleets migrate globally to find more lucrative fishing opportunities. Subsidies also supported a spree in new vessel construction in recent years. • Increased fishing pressure and competition among fishing nations severely stresses fish stocks and the marine environment. The use of unselective fishing gear results in millions of tons of unwanted bycatch being dumped overboard annually. Many millions of other animals are incidentally killed by fishing fleets. “Discards” in the fishing industry: A.K.A. ‘BYCATCH’ Overfishing: Indirect Effects of Fishing on Food Webs (bycatch cont.) • Driftnets drown by-catch – With nearly invisible filament mesh, enormous driftnets catch and hold fish by the gills. • Driftnets also entangle and drown birds, sharks, whales, and dolphins. – The by- catch problem was so dire that the UN banned large- scale driftnetting on the high seas in 1993. • Smaller driftnets are still used in coastal waters, including those of the U.S The high seas driftnet fishery Overfishing: Impacts on Biodiversity • Fishing can be an agent of selection, affecting age distribution, age and size at maturity, and growth • Fishing can alter species composition and interactions among fished species and their prey. • Fisheries often begin on large predators but their reduced numbers may lead to increased numbers of prey species, which may themselves become fished. • Intense fishing can lead to dominance by r-selected species, which often become major parts of mature fisheries. Other species can also be affected; e.g., fishery discards have caused long-term changes in seabird species composition. Overfishing: Indirect Effects Overfishing: large marine herbivores • Losses of herbivorous green turtles and fishes are thought to be partly responsible for low levels of seagrass grazing and algal overgrowth of coral reefs Overfishing: A few success stories • One success story, Spanish mackerel in the Gulf of Mexico are no longer overfished and, in fact, have become a sustainable fishery. • Pompano are also recovering in the Gulf The three main “failings” of fisheries • Oceans are a ‘free for all’, and regulatory bodies make weak commitments to preserve stocks and then fail to follow through • Fishing fleets are subsidized by nations: $20 billion globally • Conservation measures: there are few closed seasons and limits to total catch • http://www.learner.org/courses/envsci/unit/text.php?unit=9 &secNum=0# Jackson video Exotic Species in the Oceans • Invasion of marine areas by non-native species is a major threat. The National Research Council's study "Understanding Marine Biodiversity: A Research Agenda for the Nation“ says it is one of the five most critical issues facing marine life. • The ecological consequences of invasions include: – habitat loss and alteration – altered food webs – creation of novel and unnatural habitats that may be colonized by other exotic species – abnormally effective filtration of the water column – hybridization with native species – highly destructive predators; and – introductions of pathogens and disease Ecosystem characteristics that may favor successful invasions • The invaded habitat is climatically matched with the original habitat • The community is an early successional one; thus, there may be low diversity and absence of similar species. • Lack of natural enemies • Lack of keystone species • Heavily polluted or disturbed environments Possible characteristics of successful invaders • r-selected species with short generation times, high fecundity, high population growth rates – but some suggest a role for shifts between r and K strategies Non-native Pathways of Introduction • • • • • • • • • Aquaculture Aquarium trade Biological control Boats and ships Channels, canals, locks Live bait Nursery industry Scientific research institutions, schools and public aquariums Recreational fisheries enhancement Exotic Species: Ballast Water T • To maintain stability ships fill ballast tanks with water. Large ships often carry millions of gallons of ballast water. As a ship loads ballast it also loads many organisms. Ballast water is carried from one port to another, where the water may be discharged. Exotic Species: Ballast Water (2) • Perhaps 3,000 species per day are transported around the world. Most don’t survive, but some thrive in their new homes. These invaders can cause disruptions to ecosystems, economies, and may carry human diseases. • The Int’l Maritime Org. and the U.S. government recommend open ocean ballast water exchange; however, few countries have adopted this. Exotic Species: Nutria • Nutria, from South America, were introduced into Maryland and La. in 1940’s & 50s for fur production. Since the 1970s, there has been a weak demand for fur • Nutria burrows normally extend 4 to 6 ft. into marshes (but may be as long as 150 ft.) • Damage first noted in the early 1990's, and $millions in damages have accumulated Exotic species: Nutria (2) • Nutria herbivory can have dramatic impacts on coastal landscapes , and nutria have been implicated in large scale losses of marsh in Maryland. • What was once continuous marshland (above) now appears as fragmented remnants Solutions to the Nutria Problem • From the Dallas Morning News on July 7, 1997 “A nutria a day helps keep erosion at bay: Louisianians urged to eat rodents, save coast” • "A young nutria tastes a lot like rabbit," Mr. Windom (a La. Wildlife and Fisheries biologist) said, adding that they can be fried, barbecued or cooked numerous other ways. Eutrophication • Increased population density within watersheds has led to dramatic increases in nutrient inputs to coastal waters – increases range between 2 and 20 fold over preindustrial age • Consequences of eutrophication – elevated phytoplankton production coupled with stratification of the water column leads to hypoxia and anoxia – fish kills, reduced light for seagrasses, increased incidence of harmful algal blooms Worldwide “Dead Zones” Eutrophication: Harmful Algal Blooms Marine Diseases Are much more prevalent in the world’s oceans in the past few decades, and this has spurred a great deal of research into the causes of these disease outbreaks. Marine Diseases:Black Band Disease and Coral Reef Losses • Black band disease caused significant coral losses – 1973-74 in Bermuda and Florida Keys, in 1978 Acropora corals in Florida – 1985-86 in Florida again – The major component is a cyanobacterium and other microorganisms, including sulfate-reducing bacteria and heterotrophic bacteria White Band Disease • First reports of tissue slowly peeling off elkhorn and staghorn corals at Tague Bay, U.S. V. I. – The loss of tissue resulted in a band of white skeleton and this was named white-band disease (WBD). – Unlike BBD, despite intensive study, no microorganisms could be found Additional coral diseases Dark Spots Disease Rapid Wasting Disease Red Band Disease White Plague Yellow Band Disease Marine Diseases: The loss of Diadema antillarum in the Caribbean • Black urchin plague occurred in the Caribbean and caused 98% mortality within 10 days of the first signs of the disease in a new locality. – Unlike other diseases, which were localized, black urchin plague spread from Venezuela to Bermuda, reducing populations to 17% of former levels. Consequences of Diadema Dieoff • Algal overgrowth of • • coral reefs Loss reef productivity & cover Lost ecosystem productivity Marine Diseases-Seagrasses • Labyrinthula is a slime mold that could be responsible for mass mortality of seagrass . • In 1931, observers noticed blackish-brown discolorations, a loss of leaves and death of the eelgrass along the U.S. east coast • By 1933, this "disease" had decimated 90% of all eelgrass in the North Atlantic. Occurrence of Labyrinthula in Florida Bay Climate Change • • • The geographically largest scale impacts to coastal systems are caused by global climate change Warming of the world’s seas affects species by: - Changing sea level faster than most can adapt; - stressing temperature-sensitive organisms such as corals; - changing current patterns to interfere with important processes like recruitment Global warming also changes the temperature, salinity and aciditiy of estuarine and nearshore habitats and exacerbates the problem of eutrophication Climate Change and Disease • Warming can increase the transmission rates of pathogens and hasten the spread of many forms of human and non-human disease. • In most if not all cases, global climate change impacts act in negative synergy with other threats to marine organisms, and can be the factor sending ecosystems over the threshold levels for stability and productivity. Methods to Conserve Marine Biodiversity 1. Spatial management through 2. 3. 4. 5. zoning and marine protected areas Restoration Fisheries Management Integrated coastal zone management Regional & international agreements/treaties Kevin Frey © CBC-AMNH West Andros Island, Bahamas Source: T. Agardy Spatial management through zoning and marine protected areas (MPAs) Individual sites recognized for their valuable services are sometimes protected through zoning regulations and other spatial management interventions such as marine protected areas (MPAs) Restoration • Some key coastal habitats such as mangrove forests, marshes, and seagrass meadows can be, and are being, restored • In general, however, the costs of restoration far exceed costs of protecting the natural habitat Fisheries Management • Management of living marine resource use has been practiced for several centuries • Modern fisheries management has moved away from stock-by-stock and single species management to broader, ecosystem-based management • Fisheries management tools include quotas on take, gear restrictions, access restrictions, seasonal or other timing restrictions, and MPAs Integrated coastal management • Though coastal management is spreading around the world, management has not kept pace with degradation • Specific approaches have shortcomings in managing complex issues such as biodiversity • An integrated management response is needed to conserve most aspects to biodiversity, especially at the ecosystem level Regional & intl. agreements/ treaties • Most marine species cross the boundaries of individual countries, making regulation beyond the control and responsibility of any individual nation (e.g., spiny lobsters and corals in the Fla. Keys) • International/Regional treaties provide a legal framework for marine conservation action, resource regulation, and scientific research on a broad scale Constraints to Marine Conservation • Time Lags between perturbation to a system and the eventual effects on the system mean that anticipating effects is difficult • Incomplete ecological understanding (and corollary incomplete sociological understanding), can be a major constraint in effective conservation • Lack of funding (for research, for monitoring and for enforcement of regulations) is a hindrance • The lack of awareness and political will to change policies is perhaps the biggest constraint Conclusions •Marine ecosystems are extraordinarily complex and ecological understanding of marine ecosystems is limited, but enough is known that better management action can be taken •Establishing adaptive management regimes will allow us to gain important marine ecological information quickly •Integrated approaches and international cooperation are needed to conserve marine ecosystems and marine biodiversity