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.
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.
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)
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.
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)
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
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.
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
“Littoral” Zone Food Web bacteria phytoplankton & zooplankton (mostly “washed in”) periphyton & macrophytes particulate organic matter (POM) (from a range of sources) grazers fishes, mollusks, crustaceans planktivores fishes, mollusks, crustaceans, echinoderms, cnidarians deposit feeders (soft substrates) fishes, mollusks, crustaceans, echinoderms “predatory” fishes, mollusks, crustaceans, echinoderms
Euphotic Neritic Food Web dissolved organic compounds (DOC) phytoplankton phytobacteria bacteria microzooplankton phyto- plankti- vorous fishes grazing zooplankton predatory zooplankton “predatory” fishes, mollusks, etc. larger “predatory” fishes, mammals, etc.
Neritic Benthic Food Web bacteria particulate organic matter (POM) dissolved organic compounds (DOC) collecting/scavenging animals (annelid worms, echinoderms, mollusks crustaceans, fishes, etc.) predatory animals (echinoderms, mollusks, crustaceans, fishes, etc.) larger predatory animals (mollusks, crustaceans, fishes, etc.)
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)
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.
Sea Grass Communities • Fully aquatic submerged plants (true grasses). • Require soft substrates. When present they stabilize the substrates. Primary production and species richness higeher.
Sea Grass Communities Pipefish Sharptail Eel Lizard Fishes Seahorses
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)
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.
Rocky Intertidal Zonation • Provides a gradient of physical conditions.
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 – CaCO3 skeletons. • The need for “shallow” waters means that most are around land.
Fringing Reef back reef flat reef face
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.
Butterfly Fishes Bluehead Wrasse Parrot Fishes Cleaner Gobies
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.
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.
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.
Human Impacts: Fishing Reefs -dynamite fishing -poisoning Seagrass Beds -dynamite fishing -trawling – net drags Soft bottom -trawling – net drags -bycatch dumping