California's Coastal Wetlands

ThefollowingmaterialsareexerptsfromtheCaliforniaCoastalCommission'sCaliforniaCoastal

ResourceGuide,whichcanbeorderedfromUniversityofCaliforniaPressbycalling1-800-822-6657.

Coastal wetlandsincludeanumber ofnaturalcommunitiesthatshare theuniquecombination of aquatic,semi-aquatic,and terrestrialhabitats that results fromperiodicfloodingby tidal waters, rainfall,orrunoff. Wetlands providea habitat fora vast arrayof organisms, including manyendangeredspecies. Duringpeakannualmigrationperiods,hundredsofthousandsof birds migratingalongthe PacificFlywaydescend upon these coastalwetlands insearchof refugeandfood.Coastalwetlandsprovideavitallinkbetweenlandandopensea,exporting nutrients and organicmaterialto oceanwaters, and harboringjuvenilesof numerous aquatic speciesincludingmany fish. Waterflow inthese highlyproductivecommunitiescirculatesfood, nutrients,andwasteproductsthroughoutthesystem.Wetlandsbuffertheeffectsofstorms, reducingshorelineerosion,and improvewaterqualityby filteringand assimilatingmany pollutantsfromsewageoutfallsandagriculturalrunoff.Inaddition,wetlandsprovideaunique opportunityfornaturestudy.

MostofCalifornia'scoastalwetlandsareestuarinesaltmarsheswithassociatedtidalchannelsand mudflats.Estuariesareformedwherefreshwaterstreamsmeetthesea,andcontainvariablybrackish water.Saltmarshesdevelopalongtheshoresofprotectedestuarinebaysandrivermouths,aswellasin moremarine-dominatedbaysandlagoons.WetlandsthatarelesscommonalongtheCaliforniacoastare freshwatermarshes,riparianwetlands,bogs,andvernalpools.Freshwatermarshesoccurinpondsand slowmovingstreams.Likesaltwatermarshes,theyarevegetatedmostlywithherbaceousplants, predominantlycattails,andspeciesofsedges,andrushes.Freshwatermarsheshavemineralsoilsthat arelessfertilethanthoseofsaltmarshes,andexhibitagreatervarietyofplantspeciesthandosalt marshes.Riparianwetlands,whichoccuronthebanksofsteams,rivers,andlakes,commonlyfeature woodyvegetationsuchasredalder,waxmyrtle,andwillow.Bogs,unlikemarshesandstreams,have detritalsoilscomposedofpeat,andarevegetatedmostlywithmosses.Vernalpoolsoccurinsmall depressionsunderlainbydense,impenetrableclaypansoilsthatallowwatertoaccumulateinwinterand spring.Thepoolssupportsmall,usuallyannualplants,whichflowerasthewaterinthepoolsbeginto evaporate.

Wetlandsareuniqueamongbiologiccommunitiesinthattheyarecharacterizedbybothaquaticand terrestrialfeatures.Plantsandanimalsthatinhabitwetlandshavesuccessfullyevolvedmorphological andphysiologicaladaptationstothepresenceofhighlevelsofsaltandperiodicinundationand desiccation,aswellastolowconcentrationsofdissolvedoxygeninthewater-loggedsoilsand exposuretoalternatingsaltandfreshwater.Manywetlandinhabitants,includingsaltmarshplantsand somewaterbirdsareabletoexcretetheexcessiveamountsofsaltthatareabsorbedoringested.

Ecologistshaveestimatedthatahealthysaltmarshproducesfivetotentimesasmuchoxygenand

correspondingcarbohydratebiomassperacreasawheatfield.Marshplantscapturetheenergyof sunlightandformthebasisthehighlyproductivewetlandfoodweb.Akeypartofthewetlandssuccess isthebreakdownofplantmatterintodetritus,whichisthenconsumedbyfilterfeeders,depositfeeders, andotheromnivoresandscavengers.Thisassemblageofproducersandconsumerscreatesalargefood web,withfish,birds,andhumansasultimatelinks.

Decomposers,suchasbacteriaandfungi,alsobreakdownplantandanimalmatterandrecyclethe nutrients.Excrementfrombirds,fish,andinvertebratesfurtherenhancesmarshsoilsandwaterswith nitrogenrichcompounds,whicharetakenupbyalgaeandvascularplants.Thesematerialsare transportedandmixedbystreamflows,tidalcirculation,andeventheactivitiesofburrowingclamsand shrimp.Asaresult,themudflatsbecomerichininorganicnutrientsandorganicfoods.This"mixing bowl"helpstosupportthemanylinksofthemarsh'sfoodchains.Saltmarshfoodwebsareamongthe mostcomplexinnature.

Coastalwetlandsarehometoavarietyofanimals.Numerousfishspecies,includingCaliforniakillifish, baygoby,stripedbass,topsmelt,andstarryflounderareresidentsofwetlandsanddependuponthem forreproduction.Subtidaleelgrassbedsshelterlarvalandjuvenilefish,aswellasmanyspeciesof invertebrates.Saltmarshesarehometoinsectssuchasthesaltmarshwaterboatman,wandering

skipper,andnumerousspeciesofbeetlesandflies,whichgrazeonleaveandseeds,helptopollinatethe wetlandflowers,andpreyuponavarietyofsmallanimals.Clapperrailsbuildplatformnestsinthelow marsh,whereasBelding'ssavannahsparrowsnestinandfeedonthepickleweedofthehighermarsh. Saltmarshmammalsincludeshrews,harvestmice,andotherrodents;harborsealshaulouton pickleweedandsaltgrassinsouthSanFranciscoBay.

Althoughrelativelyfewbirdspeciesareyear-roundresidentsofcoastalwetlands,manyspecies temporarilyinhabitsaltmarshesduringtheirannualmigrations.CoastalCaliforniaispartofthePacific Flyway,oneofthefourprincipalbirdmigrationroutesinNorthAmerica.Duringthespringandfall months,coastalwetlandssupportflocksofwaterfowlsuchasbrant,pintails,mallard,andcanvasbacks, andshorebirds such as sandpipers,curlews,willets,andgodwits,whichstopheretorest,feed,andin somecasesoverwinter.

Sincethe1850's90percentofCalifornia'soriginalcoastalwetlandacreagehasdisappeared,andmany oftheremainingwetlandsareindangerofbeingfurtherdegradedordestroyedduetolandfill,diking, dredging,pollution,andotherhumandisturbances.However,agrowingawarenessoftheimportanceof thishabitathasledtoeffortstoprotectexistingwetlands,andtorestorethosethathavebeendegraded.