Idea Transcript
Coastal habitats
Coastal Environments Where the Land Meets the Sea Land: “Hello, I’m the Land.” Sea: “Nice to meet you, Land. I’m the Sea.”
• some of the richest environments on Earth • associated with both terrestrial and marine processes • high biological productivity supports large and diverse biological communities • “ fertile oases” oases” with abundant nutrients – estuaries – tidally influenced, semisemi-enclosed zones where river water mixes with sea water – lagoons – isolated, semisemi-enclosed bodies of shallow coastal water with no river input and brackish to hypersaline salinity – salt marshes – intertidal flats covered by vegetation – mangrove swamps – dense growth of woody trees with complex root systems in tropical and subtropical areas
• “ fragile oases” oases” with scarce nutrients – coral reefs – another lecture for another time
Importance of coastal habitats • support many coastal & oceanic food webs • provide nurseries for many species of fish • supply food for humans • provide productive habitats along flyways of migratory birds • support local economies (fisheries, ecotourism) ecotourism)
• intertidal zone is the area between high tide and low tide – also called the littoral zone
• supratidal zone is just above high tide
• rich in life due to abundance of nutrients & sunlight • Base of coastal food chains: chains:
Zonation of coastal habitats
– affected by salt spray or storms
• subtidal zone is below low tide – also called the inner neritic or subneritic province
Littoral Zone = Intertidal Zone
Innerwithin Subneritic Zone the photic zone, attached benthic algae and plants
1. bacteria 2. algae a. singlesingle-celled (phytoplankton) b. multimulti-cellular (seaweeds)
3. true plants (grasses) 4. detritus (dead and dying algae or grass covered by bacteria)
HIGH TIDE LOW TIDE
salt marsh grasses food source and protection
Base of Food Chain in Coastal Waters: 1. phytoplankton (PROTOCTISTS: planktic diatoms & dinoflagellates ) 2. benthic microscopic autotrophs (PROTOCTISTS: benthic diatoms ) 3. benthic algae (PROTOCTISTS: brown & green algae = seaweed ) & grasses (PLANTS: turtle grass, eel grass ) 4. detritus = dead and decaying algae and grasses covered with bacteria (MONERA)
seaweeds (kelp and other algae) and grasses (turtle grass, eel grass) food source and protection
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Biota in coastal habitats • High energy (beaches) and low energy (salt marshes & tidal mudflats) • Many niches for organisms exist above, within, and below the intertidal zone due to numerous environmental variables: – temperature & salinity
– called infauna
• Other plants and animals live on top of the sediment – snails, mussels, salt marsh grasses
– type of substrate
– fjords (in glacial valleys, terminal moraine at inlet) • fjords in Norway, New Zealand
• Parker River Estuary (Plum Island)
Inner Subneritic Zone within the photic zone, attached benthic algae and plants HIGH T IDE LOW T IDE
– wave or tidal energy
– drowned river valleys (rising sea level)
– barbar-built estuaries (sand spit grows across embayment)
– called epifauna
= Intertidal Zone
• origins • Chesapeake Bay
– clams, sand dollars, crabs, worms
Littoral Zone
– exposure to atmosphere
Estuaries
• Many animals live buried within the sediment
salt marsh grasses seaweeds & grasses
– tectonic estuaries (fautling /folding (fautling/folding creates coastal basin) • San Francisco Bay
• salinity – typically grades from normal marine salinity at the tidal inlet – to fresh water at the mouth of the river
Estuaries - examples
Estuaries
• Chesapeake Bay
• types – saltsalt-wedge estuaries • dominated by river outflow, outflow, with weak tidal currents • strong stratification (halocline) generates internal waves • sediments: coarse at upper estuary to fine at lower
– partiallypartially-mixed estuaries • dominated by neither river inflow nor tidal mixing • weak stratification allows stronger surface & bottom flow • sediments: marine at lower estuary, riverine at upper
– wellwell-mixed estuaries • dominated by tidal turbulence • destroys the halocline and water stratification • in a wide basin
Note: Because river discharge and tidal flow vary, conditions within an estuary can also change, being well-mixed when river flow decreases relative to tidal mixing, to becoming a salt-wedge estuary at times of maximum river discharge.
– drowned river valley, partiallypartiallymixed estuary – dumping of raw sewage, nutrients, and toxins, as well as toxic algal bloom outbreaks, have ruined ecosystem – Chesapeake Bay Foundation (CBF) founded in 1984 – has begun to recover
• San Francisco Bay – tectonic estuary, partiallypartially-mixed but complex – loss of wetlands, diversion of water, water quality deterioration, and introduced exotic species have imperiled ecosystem – private and public entities have implemented sensible management strategies
– Coriolis causes freshwater on one side and salt on the other – mixing is horizontal
• sediments: coarse and finefine-grained, derived from offshore
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Lagoons • isolated to semisemi-enclosed, shallow bodies of costal water that receive little if any fresh water inflow • exist on the landward side of barrier islands • can occur at any latitude (not just tropical!) • salinities vary from brackish to hypersaline depending upon climate and local hydrology • bottom sediments are usually sand or mud eroded from the shoreline or swept in through the tidal inlet • in the subtropics, salinity (and therefore density) can be higher than seawater – causes lagoon water to sink and flow out at depth, which may induce induce inverse flow at surface – analogous to Mediterranean Sea
Salt marshes • intertidal flats covered by vegetation • most commonly found in protected areas with a moderate tidal range, range, such as the landward side of barrier islands • immersed daily at high (flood (flood)) tide and then drained through a series of channels at low (ebb (ebb)) tide • distribution and density of organisms in salt marshes strongly reflects availability of food, need for protection, and frequency of flooding • one of the most productive environments on Earth – once considered useless land, used as dumping grounds – now known to be extremely sensitive and important areas • protect against coastal erosion from storms • serve as nurseries for larval fish, fiddler crabs, and other wildlife wildlife
Salt marsh profile
Salt marsh pictures
• can be divided into two parts: parts: – low salt marsh – mean low tide to neap high tide • Spartina alterniflora (smooth cordgrass) cordgrass) flourishes in this harsh, daily flooded environment • other species of marsh grass cannot survive here
– high salt marsh – neap high tide to highest spring tide • Spartina patens (salt hay grass) Salicornia (saltwort grass), and Distichlis spicata (spike grass) do well in this more terrestrialterrestrial-type environment. • Spartina alterniflora not found here because it is outcompeted.
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Mangrove swamps • “rainforests by the sea” • mangrove trees – large woody trees with a dense, complex root system that grows downward from the branches – the dominant plant of the tropical and subtropical intertidal area – distribution controls: • air temperature • exposure to wave and current attack • tidal range • substrate • seawater chemistry. – detritus from the mangroves, largely leaf litter, forms the base of the food chain
• important habitat for creatures great and small
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