Visualizing Environmental Science The Ocean and Fisheries Chapter 11 Chapter 7 [chapter [chapter opener opener image] Copyright
The Global Ocean Patterns of circulation Winds over the ocean produce currents Mass movements of surface-ocean water Gyres- large circular ocean currents Clockwise gyre in North Atlantic Coriolis effect Influences the paths of shallow ocean currents Earth s rotation causes currents to swerve» Right in Northern Hemisphere, clockwise movement» Left in Southern Hemisphere, counterclockwise movement
Patterns of Ocean Circulation Ocean conveyor belt Moves deep, salty sea water from higher to lower latitudes water warms up Affects regional and global climate Delivers heat from tropics to Europe
Normal vs. El Niño (ENSO) Conditions
The Global Ocean ENSO 1997 98 caused 20,000 deaths and $33 billion in property damage Snows in Western U.S., ice storms in Eastern Canada Torrential rains in Peru, Ecuador, California, Western Europe Droughts in Texas, Australia, Indonesia TAO/TRITON array Used to monitor sea surface temperatures and winds Used to forecast and better understand ENSO events
Major Ocean Life Zones
Tidal Zones
Major Ocean Life Zones Benthic environment The ocean floor, which extends from the intertidal zone to the deep ocean trenches Consists of sediments (sand and mud) Burrowing animals Bacteria, worms, clams, etc. Corals: soft-bodied animals, similar to jellyfish Live in hard cups or shells of calcium carbonate Accumulated skeletons produce coral reefs Found in warm, shallow waters Require light for symbiotic zooxanthellae High productivity even in poor nutrient waters Ecologically important: habitat; protect coastlines from erosion A threatened ecosystem: Pollution from ocean dumping and coastal pollution, silt washing downstream from clear-cut forests is smothering reefs, overharvesting, introduction of nonnative species, bleaching where stressed corals expel zooxanthellae (an event correlated with warming ocean waters), overfishing of top predators, damage from recreation.
Major Ocean Life Zones Benthic environment Sea grasses Flowering plants adapted to live in sea water Quiet temperate, subtropical, and tropical waters High primary productivity Ecologically important Stabilize sediments, reduce erosion, provide food and habitat for marine organisms Kelps Largest and most complex of all seaweeds Brown algae Common in cooler temperate marine waters Primary food producers for kelp forest ecosystem Provide habitat for many marine organisms Tubeworms, sponges, sea cucumbers, clams, crabs, fishes, sea otters, and sharks Very diverse ecosystem
Neritic province Major Ocean Life Zones Part of the pelagic environment that overlies the ocean floor from the shoreline to a depth of 200 meters Organisms are floaters (plankton) or swimmers (nekton) Euphotic zone: upper level of neritic zone Sufficient light to support photosynthetic organisms Phytoplankton are basis of food webs Zooplankton feed on phytoplankton Plankton-eating nekton consumes zooplankton Carnivorous nekton consumes plankton-eating nekton
Major Ocean Life Zones Oceanic province Cold waters, high pressure, no light Life adapted to darkness and scarce food Drifting or slow swimming, reduced bone & muscle mass Light producing organs to locate mates or prey Depend on marine snow (organic debris from upper layers of ocean) Filter feeders, scavengers, predators Many large invertebrates, e.g., giant squid
Human Impacts on the Ocean Marine pollution and deteriorating habitat Paradox: ocean provides food but is used as dumping ground Pollution increasingly threatens fisheries 80% of ocean pollution comes from land activities
Ocean Pollution has Few Controls Discarded plastic flotsam and jetsam are becoming a ubiquitous mark of human impact on the oceans. 6 million metric tons of plastic are tossed from ships every year into the ocean, where they ensnare and choke seabirds, mammals, and even fish. Estimated 8 plastic pieces for every 1 zooplankton 10-13
Human Impacts on the Ocean World fisheries Valuable food resources 90% of world s catch is fishes 6% is clams, oysters, squid, octopus, and other molluscs 3% is crustaceans: lobsters, crabs, shrimp 1% is marine algae World s annual fish harvest 1950-19 million tons 2000-95 million tons 2011-90 million tons
Human Impacts on the Ocean Problems and challenges for the fishing industry No nation has legal claim to open ocean Resources are susceptible to overuse and degradation (Tragedy of the Commons) Many species have been harvested to the point where their numbers are severely depleted Unstable for marine species that rely on them as part of food web At least 75% of world s fish stocks are exploited, overexploited or depleted Growing human population requires protein Technological advances allow efficient catch, removing all fish from an area 25% of all is bycatch (unintentionally caught, then discarded)
Human Impacts - Aquaculture Net pens anchored in nearshore areas allow spread of diseases, escape of exotic species and nonnative genes (GMO fish), and release of feces, uneaten food, antibiotics, and other pollutants into surrounding ecosystems. Plus these fish are still fed with wild caught fish.
Human Impacts on the Ocean Offshore extraction of mineral and energy resources Large deposits of minerals lie under the sea floor Manganese nodules Petroleum Major source of energy Major threat to fishing
Human Impacts on the Ocean Climate change Potential disruption of the ocean conveyor belt, which transports heat around the globe Climate warming could shut down conveyor belt within a decade» Could cause major cooling in Europe» Major warming in other parts of the world» Would not sequester CO 2 into ocean more CO 2 in atmosphere more warming more weakening of belt Acidification of the ocean
Addressing Ocean Problems Problems are complex and require complex solutions U.N. Convention on the Law of the Sea (UNCLOS) -1994-157 countries have ratified Protecting ocean resources U.N. Fish Stocks Agreement - 1995 Regulates marine fishing Fishery Conservation and Management Act (1977) Protect essential fish habitat for 600 species Reduce overfishing, rebuild populations, minimize bycatch Fishing quotas, restrictions on fishing gear, limits on number of fishing boats, closure of fisheries during spawning
Addressing Ocean Problems Future actions Establishment of no-take reserves Substantial reduction of fishing fleet Remove subsidies of fishing industry Adopt an ecosystem-based approach to manage ocean environments Focus on preserving the health and function of the entire marine ecosystem Establish networks of fully protected marine reserves Less than 5% of U.S. marine environments have been protected, with great success
Case Study The dead zone in the Gulf of Mexico N and P runoff from Mississippi River Algae grow rapidly, dead algae sink to bottom and decompose, deplete water of O 2 (hypoxic zone) Only anaerobic bacteria thrive there
Case Study March to September, worst June-August Climate change is making dead zones worse, even without runoff Threaten biodiversity and coastal fisheries