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Estuaries. Where freshwater and saltwater meet Water levels in estuaries rise and fall with the tides. Salinity fluctuates with Tidal cycles Time of year Precipitation. Estuaries . Organisms must tolerate wide fluctuations in salinity, temperature and light.
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Estuaries • Where freshwater and saltwater meet • Water levels in estuaries rise and fall with the tides. • Salinity fluctuates with • Tidal cycles • Time of year • Precipitation
Estuaries • Organisms must tolerate wide fluctuations in salinity, temperature and light. • Among the most fertile, productive systems in the world. • Nutrients from land and upstream • Tidal action “stirs” up the nutrients and removes wastes • Shallow water, so high light penetration • Presence of many plants
Oceans • Covers 71 % of the Earth’s surface • Oceans contain 96.5 % water with the salinity being in the range of 33 - 37 ppm. Varies place to place due to evaporation , precipitation and freshwater sources. • Ions found: Cl- 1.9%, Na+ 1.1%, SO42- 0.3%, Mg2+ 0.1%, Ca2+ 0.04%, K+ 0.04% and HCO3- 0.01%
Oceans • Salinity near the equator is low due to high precipitation • Salinity 30-35 degrees north and south of that is high due to evaporation exceeding precipitation • Dissolved oxygen as well as phosphates and nitrates are also key abiotic factors.
Oceans • Vertical structured and horizontally flowing • Water density increases as salinity increases and temperature decreases. Results in different layers of water. • Water at the surface is heated by sunlight and stirred by the wind.
Oceans • Surface Zone – range 0 – 150 m; 2% of ocean water by volume. Heated by sunlight, stirred by wind. • Pycnocline Zone– density of water increses rapidly with depth; 18% of ocean water volume • Deep Zone – Sluggish and unaffected by winds or sunlight; remaining 80% of ocean water volume
Oceans • Midlatitude ocean temperature only experiences a 10 degree celsius annual temperature variation. • Tropical and polar regions even more stable. • Reason: high heat capacity of water.
Ocean • Currents is the horizontal movement of the waters within 400 m of the surface. • Caused by the density differences, heating and cooling, gravity and wind. • Currents transport nutrients, heat, larvae and even pollution.
Ocean • Vertical Movement • Upwelling – caused when the colder, deeper water moves to the surface. Occurs where currents diverge or flow away from one another. Winds parallel or from inland can cause condition as well. Rich in nutrients from the bottom, great fishing! • Downwelling – Currents converge, surface water sinks. Warm water rich in DO provides influx of oxygen for deep water organisms.
Topography • Underwater mountains and valleys affect the biodiversity. • Continental Shelf – gentle sloped shallow waters bordering continents 1.9 m per km • Photic zone upper 10 m absorbs 80% of sunlight and is thus where almost all the oceans’ primary productivity occurs.
Topography • Pelagic between photic zone and benthic zone • In Open-Ocean ecosystems, primary productivity and abundant animal life occurs in pelagic zones if areas of updwellings. • Benthic - ocean floor
Marine & Coastal Ecosystems • Open-Ocean – Phytoplankton is base of food chain. Zooplankton (photsynthetic algae, protists and cyanobacteria) feed fish, whales and other swimming animals. Higher trophic level animals (turtles, sharks and large fish) feed on them.
Marine & Coastal Ecosystems • Within the continental shelf, kelp forests and coral reefs are unique ecosystems. • Kelp is actually brown algae that grows from the floor of continental shelf towards sunlit surface. Faster (18” per day) than kudzu.
Marine & Coastal Ecosystems • Kelp forests shelter and provide food for invertebrates and fish and thus provide a happy hunting ground for higher trophic level (seals, sharks and sea otters). • Keystone species of sea otters feed on sea urchins that feed on kelp. No sea otters….
Marine & Coastal Ecosystems • Kelp forests ecosystem service is as a wave energy absorber • Kelp forests are found in high primary productivity areas near shoreline.
Marine & Coastal Ecosystems • Coral Reefs are also in areas of high primary productivity near shore lines mostly in subtropical and tropical waters. • Coral reefs are a mass of CaCO3 skeletons of tiny colonial marine organisms known as corals. • Receive their nutrients from tiny, symbiotic algae called zooxanthelle
Marine & Coastal Ecosystems • Zooxanthelle give the coral reefs their exquisite colors. • Ecosystem service is also as a wave energy absorber. Look at Pacific atolls with reef systems.
Marine & Coastal Ecosystems • Dangers to coral reef ecosystems cause coral bleaching; the zooxanthenelle leave the coral. Lose their color or die as a result of • Increased surface temperature due to climate change • Influx of pollutants • Or combination of both
Marine & Coastal Ecosystems • Other threats to reefs: • Influx of nutrient pollutants (PO43- and NO31-) leading to algae blooms that blanket reefs (Florida Keys). • Increased amounts of CO2 from the atmosphere increasing acidity • Bottom-trawling fishing
Marine & Coastal Ecosystems • Deep water reefs exist off Norway, Spain and British Isles. Cooler waters. • Fishery habitat for commercial cod; threatened
Fishing • International community studies have predicted total collapse of world’s marine current fished resources by 2048 • 50% of the world’s marine fish are fully exploited – more intense fishing of those species will lead to extinction.
Fishing • 25% of the world’s marine fish are over exploited – are headed towards extinction. • We are already seeing fishery collapse off the coast of Newfoundland and New England
Fisheries in Distress: Cod Landings from Georges Bank, 1982-2004
Industrial Fishing • Commercial fleets use fossil fuels, huge vessels and new technologies to capture fish in undreamed of numbers. Factory fishing ships even package and freeze fish for markets while underway.
Commercial Fishing Damages to Ecosystems • By-catch – accidental catching of non-target species accounts for the deaths of thousands upon thousands of fish, sharks, marine mammals and birds. • Dolphin deaths alone in 1986 were 133 000 a year. In 1998 had dropped to 2 000 a year
Trawler fishing Fish farming in cage Spotter airplane Sonar Purse-seine fishing Trawl flap Trawl lines Fish school Trawl bag Drift-net fishing Long line fishing Buoy Float Lines with hooks Deep sea aquaculture cage Fish caught by gills Fig. 12-A, p. 255
Commercial Fishing Methods • Driftnetting • Long nets , spanning large expanses that drift with the currents • Capture passing fish • Target fish that travel in large schools in open waters such as herring, sardines and mackeral (even sharks)
Fishing • Long-line Fishing • Extremely long-lines extended out with baited hooks along the line (Perfect Storm). • Goal is to catch larger fish like tuna, swordfish and halibut.
Fishing • Purse-Seine Fishing – schools are surrounded by a large net. Bottom of net in cinched up and then gathered up. • Target fish – herring, mackerel, yellowfin tuna and anchovies that feed in schools along the surface.
Fisheries Problems: Bottom Trawling Too many boats High technology Too few fish
Fishing • Trawling • Drag immense cone shaped nets behind the boat. Weighted at bottom with floats attached at to to keep them open. • Catch pelagic fish in open waters • Bottom-trawling • Continental-shelf; goal is to catch ground fish, shellfish and other benthic organisms
Commercial Fishing Damages to Ecosystems • Drift netting by-catches leads to the drowning deaths of turtles, dolphins and seals. • Many nations have banned drift net fishing altogether. UN banned nets longer than 2.5 km in international waters • Long-line fishing kills turtles, sharks and albatrosses (large, with 3.6m wingspan). • Estimated that 300 000 seabirds a year die as a result of diving for the baited hooks.
Commercial Fishing Damages to Ecosystems • Bottom-trawling is akin to clear cutting in a forests. • Leaves large swathes of damaged sea bottom; crushes animals in its path. • Coral reefs are irreversibly damaged.
Past Overexploitation • Chesapeake Bay oyster • Overharvesting in 18th and 19th century lead to collapse of industry in late 19 century. • Act as algae and bacteria filters on the bottom. • Resulted in eutrophication and hypoxia of waters.
Marine Species Management • Endangered Species Act (ESA) • Marine Sanctuaries Act • U.S. Whale Conservation and Protection Act • International Whaling Commission and Protection Act – regulates the species that can be harvested and sets quotas on the numbers of cetaceans that can be harvested
Marine Species Management • Magnuson-Stevens Fisheries Management and Conservation Act (Magnuson Act) – establishes Regional Fisheries Management Councils that set quotas, size limits and seasons; establishes 200 mile fishing area; protects essential habitat; rebuilds overfished stocks and minimizes bycatch.
The Magnuson Conservation Act of 1976 • Gave federal government authority to manage fisheries • Claimed the area between 3 and 200 miles offshore as the “Exclusive Economic Zone”
The Magnuson Conservation Act of 1976 • Designed to eliminate foreign fishing • Designed to restore and conserve fish http://images.fws.gov/
Sustainable Fisheries Act • The 1996 reauthorization of the Magnuson Act • Mandates that fish stocks be rebuilt • Management plans and yields be based on scientific data • Steps be taken to minimize “by catch”
Marine Species Management • Marine Mammal Protection Act • Convention on International Trade in Endangered Species/CITES • UN Law of the Seas – individual countries have jurisdiction over the Exclusive Economic Zone (200 miles off shore) and sovereignty over the sea bed 12 miles off shore; allows for the Individual Transferable Quotas (ITQ) in which allocated quotas can be sold to others.
