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Published byMalcolm Charles Modified over 9 years ago
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Coastal Seas A Coastal Sea is the part of the world ocean that covers the continental shelf. Continental shelves extend variable distances from continents and typically gradually descend to 140 m (460ft) before dropping off as the continental slope.
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Continental Shelves
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Coastal Sea
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Light Penetration Epipelagic / Euphotic Zone = The zone of the oceans to 200 m with enough light to sustain photosynthesis. Almost all of all continental shelves is within the euphotic zone. However, almost all photosynthesis occurs in the top 30 m and turbidity can reduce that. The benthic zone of continental shelves away from shore is still pretty dark and rarely supports any but the most minimal photosynthesis.
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Tides Tides = Periodic movement of the sea due to the gravitational effects of the sun and the moon on the world ocean (High and low tides ~ twice a day.) Spring Tides – are tides with the largest tidal range (greatest range of tides = every 14 days) Neap Tides – are tides with the lowest tidal range (least range of tides = every 14 days)
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Tides
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Tidal Range
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Coastal Sea: “The Littoral” Littoral zone = ? (Different for lakes.) -area affected by the ocean to ~ 60 m deep -splash zone to deepest area affected by wave energy -covered and uncovered by tides (Eulittoral) Surf zone = area above where wave energy affects the bottom and waves begin to break.
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The “Littoral” Substrate Hard substate = rock outcrops, large boulders, and/or rocks not moved by wave or tidal action. = VERY small part of littoral “Soft” substate = particles (from microscopic silt to rocks) moved by wave or tidal action. = most of the littoral -mud, sand, gravel (beaches & mud flats) -well sorted = particles mostly same size (particles move easily) -poorly sorted = particles vary in size (particles move less easily)
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Coastal Sea: Neritic Zone Neritic zone = from the lowest level NOT uncovered by the tides to the edge of the continental shelf -Neritic pelagic -Neritic benthic – continental shelf sea floor
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The Neritic Substrate Almost all of the substrate of the neritic zone is soft due to sediment from the water column and little or no wave action effects.
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Stream/Runoff Contributions
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Coastal Upwelling
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Oceanic Primary Production
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Coastal Primary Production Macrophytes = near shore; green, brown, and red algae In general, surface to deeper brown-to-green-to-red (This is very rough and all are found shallowly and deeply.) Periphyton = near shore; mostly green algae, diatoms, and cyanobacteria Phytoplankton = euphotic zone; mostly green algae, diatoms, dinoflagellates, cocclithophores, and cyanobacteria
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“Littoral” Zone Food Web periphyton & macrophytes grazers fishes, mollusks, crustaceans “predatory” fishes, mollusks, crustaceans, echinoderms planktivores fishes, mollusks, crustaceans, echinoderms, cnidarians phytoplankton & zooplankton (mostly “washed in”) deposit feeders (soft substrates) fishes, mollusks, crustaceans, echinoderms particulate organic matter (POM) (from a range of sources) bacteria
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Euphotic Neritic Food Web grazing zooplankton predatory zooplankton bacteria phytoplankton phytobacteria dissolved organic compounds (DOC) “predatory” fishes, mollusks, etc. phyto- plankti- vorous fishes microzooplankton larger “predatory” fishes, mammals, etc.
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Neritic Benthic Food Web predatory animals (echinoderms, mollusks, crustaceans, fishes, etc.) bacteria dissolved organic compounds (DOC) particulate organic matter (POM) collecting/scavenging animals (annelid worms, echinoderms, mollusks crustaceans, fishes, etc.) larger predatory animals (mollusks, crustaceans, fishes, etc.)
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Soft Substrate Communities Affected by constant change in substrate due to wave action or sedimentation. Species composition usually more structured by disturbance and predation (less affected by competition)
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Reefs & Banks Reef = a solid (hard) outcrop in shallow water reached by sunlight. (Not all are coral reefs. e.g., oyster reefs ) Bank = shallower regions of the offshore continental shelf.
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Sea Grass Communities Fully aquatic submerged plants (true grasses). Require soft substrates. When present they stabilize the substrates. Primary production and species richness higeher.
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Sea Grass Communities Seahorses Pipefish Lizard Fishes Sharptail Eel
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Hard Substrate Communities Less change in substrate and substrate provides fixed anchoring point. Species composition usually structured by competition and predation (usually a little less affected by disturbance)
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Hard Substrate Limitation The predominance of soft bottoms means that hard substrates are limited. Artificial reefs are rapidly colonized. Both biomass and species richness are greater around such reefs.
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Rocky Intertidal Zonation Provides a gradient of physical conditions.
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Tropical Coral Reefs Coral reefs found only between 30º N and S latitude & require shallow, warm, clear water. Built by coral animals with mutualistic algae – CaCO 3 skeletons. The need for “shallow” waters means that most are around land.
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Coral Polyps
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Reef Types
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Fringing Reef flat back reef reef face
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Australia Great Barrier Reef
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Tropical Coral Reef Communities Primary production from microphytic algae in corals and macrophytic algae. Plankton from open water important. Very diverse communities. Structured by competition, predation, & disturbance. Competition (especially for space) is usually very intense. Many territorial animals.
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Bluehead Wrasse Parrot Fishes Cleaner Gobies Butterfly Fishes
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Human Impacts: General Pollutants from stream & direct runoff. -additional sediment -heavy metals & industrial pollutants -phosphate (P) [and nitrate (N)] Over fishing/over harvest – removing part of the community. Red Tides – blooms of certain species of dinoflagellate (phytoplankon) that can result in low oxygen and/or neurotoxin release.
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Human Impacts: Sea Grasses Pollutants from stream & direct runoff. -additional sediment – can cover or increase turbidity -heavy metals & industrial pollutants -phosphate (P) [and nitrate (N)] – overgrown by periphyton and smothered Dredging (& dragging of boat anchors) – root damage takes a long time for recovery.
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Human Impacts: Coral Reefs Pollutants from stream & direct runoff. -additional sediment – can cover or increase turbidity and smother -heavy metals & industrial pollutants -phosphate (P) [and nitrate (N)] – overgrown by periphyton/macrophytes and smothered Physical Damage to the Reef –takes a long time for recovery. Increase or decrease in temperature. Coral stress causes bleaching.
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Human Impacts: Coral Reefs
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Coral Bleaching
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Human Impacts: Fishing Reefs -dynamite fishing -poisoning Seagrass Beds -dynamite fishing -trawling – net drags Soft bottom -trawling – net drags -bycatch dumping
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