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Lecture notes
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tarix | 23.01.2018 | ölçüsü | 16,75 Kb. | | #21953 |
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LECTURE NOTES MARINE BIOLOGY (MARSC 180) L. SNYDER
Ch. 8 Temperate Coastal Seas
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Lie between Tropics & Polar Circles (23.5º – 66.5º N. & S.)
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Intertidal Shore to Continental Shelf
Coastal Species
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Many in close association w/ seafloor
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All large marine plants & algae
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Benthic species live on or in sediment
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Impacted by sediments & seawater
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Seafloor accumulates organic detritus from photic zone
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Major food source
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Especially in aphotic zone
Benthic Animals
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Epifauna: live on sediment
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Suspension feeders live on rocks or coarse substrate to avoid clogging filters
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Infauna (macro, micro): live w/in sediment
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Swallow or displace sediments as they move, burrow
Benthic Larval Dispersal
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75% of slow-moving or attached benthos extend geographic range by broadcast spawning (eggs & sperm)
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Many larvae don’t survive
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But, survivors extend species’ geographic range
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Increase genetic diversity
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Factors influence larval selection of suitable settling area:
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Bottom type/ texture, current speed, temp, light, chemicals from conspecific adults Metamorphose into a juvenile form
Intertidal (Littoral) Communities
Rocky Shores
Sandy Beaches
Intertidal Zone
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Daily tidal fluctuations expose intertidal species to extremes
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Submergence (High tide): Preferred for most intertidal species (marine)
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Temp & salinity return to normal, food/nutrients & DO replenished, wastes removed
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Emergence (Low tide): Dry terrestrial conditions, exposed to air, heat, etc.
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Intertidal species must adapt to stresses
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High tide: Crashing waves, abrasion
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Low tide: Heat, sun (UV), dryness, No O2 Cold, Freshwater (rainfall & runoff), Predators (birds, terrestrial spp.), human trampling
Sandy Beaches
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Depositional environments
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Unconsolidated sediment (granite, shell, volcanic), & detritus
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Waves gentle enough to allow sand accumulation, but wash silt & clay away
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Longshore currents move sand along shore
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Animal populations vary seasonally
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Lower species diversity & density than rocky shores
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Unsuitable substrate for attachment
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Little algae & epifauna, mostly infauna
Beach Zonation
Filter Feeding
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Common among beach macrofauna EX: Sand crab (Emerita analoga)
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Uses feathery antennae to filter plankton, bacteria, & detritus from incoming water
CA Grunion (Leuresthes) Reproduction
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Come out of water to spawn (lay & fertilize eggs) on beach
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At night from Feb-Sep
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1st 3 hours after highest spring tides (full or new moon)
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Female digs tail in sand to lay eggs & Male deposits milt (sperm) around her
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In ~10 days babies hatch & wash out to sea at next high spring tide
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California Least Tern & Western Snowy Plover
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Ground Nesters
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Endangered species
Rocky Intertidal (Rocky Shore)
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Stressful habitat
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Wave stress, alternate dry & wet periods, sun (UV) exposure, rocks
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Clumped distribution
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Contradiction:
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Harsh physical factors: Wave stress, sun, dry
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Abundant: Food, nutrients, micro-habitats & niches
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Competition for resources:
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Affects success of species & individuals
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Vertical Zonation: species adapted to unique conditions
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Splash zone: Receive only ocean's salty spray. Flooded only by highest tides & winter storm waves
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Upper intertidal: closest to land, mostly dry. Periwinkle snails, Barnacles
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Mid-intertidal: ½ Dry, ½ wet
Algae, limpets, crabs, mussels, purple sea urchin, Sea anemones
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Lower intertidal: furthest from shore, mostly submerged. Algae, sea stars, red sea urchin, sea hare, sea cucumber
Intertidal Zonation: Increasing Diversity from splash zone to low intertidal
Upper Intertidal
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Wet infrequently by high tide, sea spray
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Lichens & algae store water to avoid desiccation
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Few invertebrates that tolerate dryness & temp. change
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Can seal & anchor shells to rock to seal in moisture
Middle Intertidal
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Covered & uncovered 2X/day by tides
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Species adapted to exposure to air & seawater
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Dense population = competition for substrate, water, & food
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Monocultures: Ochre seastar (Keystone sp.)
Lower Intertidal
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Species cannot tolerate air exposure
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High diversity
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Abundant algae, sea grasses
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Many soft bodied animals
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Predatory seastars move between mid & low intertidal
Oil Spills & the Intertidal
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Oil released in sea will eventually float to & rest in intertidal
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Most oil in marine environment enters via urban runoff, dumping
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Effects of spilled oil depends on type:
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Light refined petroleum (diesel & gas) – mixes in H2O column, more toxic, but evaporates quickly & doesn’t persist in environment
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Crude – less toxic, but remains on water surface or shoreline much longer, sinks
Oil Tanker Spills
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Small portion of total marine spills
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Locally devastating, major cleanup
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U.S. Oil Pollution Act 1990 (response to Exxon Valdez): all oil-carrying vessels must have double-hull
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Exxon still appealing $5 billion fine (17 yrs)
Oil Spills & Marine Life
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Clogs gills of fish & benthic species
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Damages digestive system
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Mammals & birds (fur, feathers) lose bouyancy & insulation
Oil Spill Cleanup
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Scrubbing w/ high pressure, hot water damage
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Leave it alone, rely on natural processes
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Booms, shovels, buckets, absorbent materials
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Bioremediation by oil digesting bacteria
Subtidal (Sub-littoral)
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Lower intertidal merges w/ upper continental shelf
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Lower intertidal species also abundant here
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Beyond effects of tidal action
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Sediments & detritus accumulate
Kelp Forests
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Dominate subtidal areas w/ rocky outcrops
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S. California impacts:
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Overgrazed by urchins (loss of otters)
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El Nino (high temps.)
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Suspended organic material from outfalls
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Decreases photosynthesis
Sewage Treatment & Outfalls
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Primary Tr. - large solids, grease removed
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Secondary Tr. – Good bacteria eats organic solids, chlorine kills bacteria,
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chlorine removed (via chemicals)
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22% of biosolids used by farmers or compost centers
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Many chemical toxins, heavy metals, pharmaceuticals not removed & enter ocean
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Orange County Sanitation District outfall: 4 miles off coast of Huntington Beach (200 ft. deep)
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