Geo108 lec23 coastal habitats - Clark Science Center

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Coastal EnvironmentsCoastal Environments

Where the Land Meets the SeaWhere the Land Meets the SeaLand: “Hello, I’m the Land.”Land: “Hello, I’m the Land.”

Sea: “Nice to meet you, Land. I’m the Sea.”Sea: “Nice to meet you, Land. I’m the Sea.”

Coastal habitatsCoastal habitats

•• some of thesome of therichest environments richest environments on Earthon Earth•• associated with both associated with both terrestrialterrestrial and and marinemarine processesprocesses•• high biological productivityhigh biological productivity supports large and diverse supports large and diverse

biological communitiesbiological communities•• ““ fertile oasesfertile oases” with abundant nutrients” with abundant nutrients

–– estuariesestuaries –– tidally influenced, semitidally influenced, semi--enclosed zones where river water enclosed zones where river water mixes with sea watermixes with sea water

–– lagoonslagoons –– isolated, semiisolated, semi--enclosed bodies of shallow coastal water with no enclosed bodies of shallow coastal water with no river input and brackish to river input and brackish to hypersaline hypersaline salinitysalinity

–– salt marshessalt marshes –– intertidalintertidal flats covered by vegetationflats covered by vegetation–– mangrove swampsmangrove swamps –– dense growth of woody trees with complex root dense growth of woody trees with complex root

systems in tropical and subtropical areassystems in tropical and subtropical areas

•• ““ fragile oasesfragile oases” with scarce nutrients” with scarce nutrients–– coral reefs coral reefs –– another lecture for another timeanother lecture for another time

Importance of coastal habitatsImportance of coastal habitats•• support many support many coastal coastal

& oceanic food webs& oceanic food webs•• provide provide nurseriesnurseries for for

many species of fishmany species of fish•• supply supply foodfood for for

humanshumans•• provide productive provide productive

habitats along habitats along flywaysflywaysof migratory birdsof migratory birds

•• support support local local economieseconomies (fisheries, (fisheries, ecotourismecotourism))

•• rich in liferich in life due to due to abundance of abundance of nutrientsnutrients& & sunlightsunlight

•• Base of Base of coastal food coastal food chainschains::1.1. bacteriabacteria2. 2. algaealgae

a.a. singlesingle--celled celled (phytoplankton)(phytoplankton)b.b. multimulti--cellular cellular (seaweeds) (seaweeds)

3. 3. true plantstrue plants (grasses)(grasses)4. 4. detritusdetritus (dead and dying (dead and dying

algae or grass covered by algae or grass covered by bacteria)bacteria)

HIGH TIDE

LOW TIDE

salt marsh grassesfood source and protection

seaweeds (kelp and other algae)

and grasses (turtle grass, eel grass) food source and protection

Inner Subneritic Zonewithin the photic zone,

attached benthic algae and plants

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)

Zonation Zonation of of coastal habitatscoastal habitats

•• intertidalintertidal zonezone is the area between is the area between high tide and low tidehigh tide and low tide–– also called the also called the littoral zonelittoral zone

•• supratidalsupratidal zonezone is just above high tideis just above high tide–– affected by salt spray or stormsaffected by salt spray or storms

•• subtidalsubtidal zonezone is below low tideis below low tide–– also called the inner also called the inner neriticneritic or or

subneriticsubneritic provinceprovince

Littoral Zone= Intertidal Zone

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Biota in coastal habitatsBiota in coastal habitats•• High energyHigh energy (beaches) and (beaches) and

low energylow energy (salt marshes (salt marshes & tidal mudflats)& tidal mudflats)

•• Many Many nichesnichesfor organisms for organisms exist above, within, and exist above, within, and below the below the intertidalintertidal zonezonedue to numerous due to numerous environmental variables:environmental variables:

–– temperature & salinitytemperature & salinity

–– exposure to atmosphereexposure to atmosphere

–– wave or tidal energywave or tidal energy

–– type of substratetype of substrate

•• Many animals live Many animals live buried withinburied withinthe sediment the sediment –– called called infaunainfauna–– clams, sand dollars, crabs, wormsclams, sand dollars, crabs, worms

•• Other plants and animals live Other plants and animals live on on top oftop of the sediment the sediment –– called called epifaunaepifauna–– snails, mussels, salt marsh grassessnails, mussels, salt marsh grasses

HIGH TIDE

LOW TIDE

salt marsh grasses

seaweeds& grasses

Inner Subneritic Zonewithin the photic zone,

attached benthic algae and plantsLittoral Zone

= Intertidal Zone

EstuariesEstuaries•• originsorigins

–– drowned river valleys (rising sea level)drowned river valleys (rising sea level)•• Chesapeake BayChesapeake Bay

–– fjords (in glacial valleys, terminal fjords (in glacial valleys, terminal moraine at inlet)moraine at inlet)

•• fjords in Norway, New Zealandfjords in Norway, New Zealand

–– barbar--built estuaries (sand spit grows built estuaries (sand spit grows across embayment)across embayment)

•• Parker River Estuary (Plum Island)Parker River Estuary (Plum Island)

–– tectonic estuaries (tectonic estuaries (fautlingfautling/folding /folding creates coastal basin)creates coastal basin)

•• San Francisco BaySan Francisco Bay

•• salinitysalinity–– typically gradestypically gradesfrom from normal marine normal marine

salinitysalinity at the at the tidal inlettidal inlet–– to to fresh waterfresh waterat the at the mouth of the rivermouth of the river

EstuariesEstuaries•• typestypes

–– saltsalt--wedge estuarieswedge estuaries•• dominated by dominated by river outflowriver outflow, with, with weak tidal currentsweak tidal currents•• strongstrong stratification (halocline) generates internal wavesstratification (halocline) generates internal waves•• sediments: coarse at upper estuary to fine at lowersediments: coarse at upper estuary to fine at lower

–– partiallypartially--mixed estuariesmixed estuaries•• dominated by dominated by neitherneither river inflow nor tidal mixingriver inflow nor tidal mixing•• weakweak stratification allows stronger surface & bottom flowstratification allows stronger surface & bottom flow

•• sediments: marine at lower estuary,sediments: marine at lower estuary,riverine riverine at upperat upper

–– wellwell--mixed estuariesmixed estuaries•• dominated by dominated by tidal turbulencetidal turbulence•• destroysdestroys the halocline and water stratificationthe halocline and water stratification•• in a wide basinin a wide basin

–– CoriolisCoriolis causes freshwater on one side and salt on the othercauses freshwater on one side and salt on the other–– mixing is horizontalmixing is horizontal

•• sediments: coarse and finesediments: coarse and fine--grained, derived from offshoregrained, derived from offshore

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.

Estuaries Estuaries -- examplesexamples•• Chesapeake BayChesapeake Bay

–– drowned river valley, partiallydrowned river valley, partially--mixed estuarymixed estuary

–– dumping of raw sewage, nutrients, dumping of raw sewage, nutrients, and toxins, as well as toxic algal and toxins, as well as toxic algal bloom outbreaks, have ruined bloom outbreaks, have ruined ecosystemecosystem

–– Chesapeake Bay Foundation (CBF) Chesapeake Bay Foundation (CBF) founded in 1984founded in 1984

–– has begun to recoverhas begun to recover

•• San Francisco BaySan Francisco Bay–– tectonic estuary, partiallytectonic estuary, partially--mixed but mixed but

complexcomplex–– loss of wetlands, diversion of water, loss of wetlands, diversion of water,

water quality deterioration, and water quality deterioration, and introduced exotic species have introduced exotic species have imperiled ecosystemimperiled ecosystem

–– private and public entities have private and public entities have implemented sensible management implemented sensible management strategiesstrategies

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LagoonsLagoons•• isolated to semiisolated to semi--enclosed, shallow bodies of costal water that enclosed, shallow bodies of costal water that

receive receive little if anylittle if any fresh water inflowfresh water inflow•• exist on the exist on the landwardlandward side of barrier islandsside of barrier islands•• can occur at can occur at anyany latitude (not just tropical!)latitude (not just tropical!)•• salinities vary from salinities vary from brackish tobrackish to hypersalinehypersaline depending depending

upon climate and local hydrologyupon climate and local hydrology•• bottom sediments are usually bottom sediments are usually sand or mudsand or mud eroded from the eroded from the

shoreline or swept in through the tidal inletshoreline or swept in through the tidal inlet•• in the subtropics, salinity (and therefore density) can be in the subtropics, salinity (and therefore density) can be

higher than seawaterhigher than seawater–– causes lagoon water to sink and flow out at depth, which may indcauses lagoon water to sink and flow out at depth, which may induce uce

inverse flowinverse flowat surfaceat surface–– analogous to Mediterranean Seaanalogous to Mediterranean Sea

Salt marshesSalt marshes•• intertidalintertidal flats covered by vegetationflats covered by vegetation•• most commonly found in most commonly found in protectedprotected areas with a areas with a

moderate tidal rangemoderate tidal range, such as the landward side of , such as the landward side of barrier islandsbarrier islands

•• immersedimmersed daily at high (daily at high (floodflood) tide and then ) tide and then draineddrainedthrough a series of channels at low (through a series of channels at low (ebbebb) tide) tide

•• distribution and density of organisms in salt marshes distribution and density of organisms in salt marshes strongly reflects availability of food, need for strongly reflects availability of food, need for protection, and frequency of floodingprotection, and frequency of flooding

•• one of the most productive environments on Earthone of the most productive environments on Earth–– once considered useless land, used as dumping groundsonce considered useless land, used as dumping grounds–– now known to be extremely sensitive and important areas now known to be extremely sensitive and important areas

•• protect against coastal erosion from stormsprotect against coastal erosion from storms•• serve as nurseries for larval fish, fiddler crabs, and other wilserve as nurseries for larval fish, fiddler crabs, and other wildlifedlife

Salt marsh profileSalt marsh profile•• can be divided into can be divided into two partstwo parts::

–– low salt marshlow salt marsh –– mean low tide to neap high tidemean low tide to neap high tide•• Spartina alternifloraSpartina alterniflora(smooth (smooth cordgrasscordgrass) flourishes in this harsh, daily flooded environment) flourishes in this harsh, daily flooded environment

•• other species of marsh grass other species of marsh grass cannot survivecannot survive herehere

–– high salt marshhigh salt marsh –– neap high tide to highest spring tideneap high tide to highest spring tide•• Spartina Spartina patens patens (salt hay grass)(salt hay grass)Salicornia Salicornia ((saltwort saltwort grass), and grass), and Distichlis spicata Distichlis spicata (spike (spike

grass) do well in this more terrestrialgrass) do well in this more terrestrial--type environment.type environment.

•• Spartina alternifloraSpartina alternifloranot found here because it is not found here because it is outcompetedoutcompeted..

Salt marsh picturesSalt marsh pictures

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Mangrove swampsMangrove swamps•• “rainforests by the sea”“rainforests by the sea”•• mangrove treesmangrove trees

–– large woody trees with a dense, large woody trees with a dense, complex root system that grows complex root system that grows downward from the branchesdownward from the branches

–– the dominant plant of the tropical the dominant plant of the tropical and subtropicaland subtropicalintertidalintertidalareaarea

–– distribution controls:distribution controls:

•• air temperatureair temperature

•• exposure to wave exposure to wave and current attackand current attack

•• tidal range tidal range

•• substratesubstrate

•• seawater chemistryseawater chemistry..

–– detritus from the mangroves, largely leaf litter, forms the basedetritus from the mangroves, largely leaf litter, forms the baseof of the food chainthe food chain

•• important habitat for creatures great and smallimportant habitat for creatures great and small