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<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 2: Spartina Distribution and SpreadSPREAD OF INVASIVE SPARTINA IN THE SAN FRANCISCO ESTUARYK. ZAREMBA 1,4 ,M.MCGOWAN 2 , AND D.R. AYRES 31 San Francisco Estuary Invasive Spartina Project, 2612-A 8 th St., Berkeley, CA 947102 Maristics, 1442A Walnut St., Suite 188, Berkeley, CA 94709, maristics@comcast.net3 U.C. Davis, Evolution and Ecology, Davis, CA 95616, drayres@ucdavis.edu4 Current address: 971 Village Dr. Bowen Island, BC, V0N 1G0 Canada; katyzaremba@yahoo.caWe mapped <strong>the</strong> location and extent <strong>of</strong> all non-native Spartina in <strong>the</strong> San Francisco estuary in 2000and 2001 and mapped a sample <strong>of</strong> 28 sites in 2003. We incorporated aerial photographs, groundsurveys, and genetic analyses into a GIS. These sites demonstrated an average increase <strong>of</strong> 317percent coverage <strong>of</strong> S. alterniflora x foliosa hybrids, radiating from points <strong>of</strong> <strong>the</strong> deliberateintroduction <strong>of</strong> S. alterniflora. Extrapolating to <strong>the</strong> entire estuary, this suggests a potential increasefrom ca 190 hectares(ha) (470 acres[ac]) recorded in 2001 to as much as 793 ha (1,960 ac) in 2003.Hybrids now occupy approximately four percent <strong>of</strong> <strong>the</strong> total area <strong>of</strong> marsh and mudflats in <strong>the</strong> bay.Spread was greater in tidal marshes or formerly diked baylands and mudflats than in creeks, sloughs,and urbanized marsh (riprap, boat ramps). Genetic testing found no new invasion sites. Manualcontrol methods applied in 2002-2003—digging or covering with geo-textile fabric—were effectiveat removing or killing small populations or single plants <strong>of</strong> Spartina species.Keywords: invasive Spartina, S. alterniflora, S. densiflora, S. patens, S. alterniflora x foliosahybrids, monitoringINTRODUCTIONThe San Francisco Bay Estuary contains <strong>the</strong> largest andmost ecologically important expanses <strong>of</strong> tidal mudflats andsalt marshes in <strong>the</strong> contiguous western United States with adiverse array <strong>of</strong> native plants and animals. Over <strong>the</strong> years,many non-native species <strong>of</strong> plants and animals have beenintroduced to <strong>the</strong> Estuary threatening to change <strong>the</strong> structure,function, and value <strong>of</strong> <strong>the</strong> Estuary’s tidal lands. In recentdecades four species <strong>of</strong> non-native Spartina have begun tospread rapidly in <strong>the</strong> Estuary. Though valuable in <strong>the</strong>irnative settings, <strong>the</strong>se introduced Spartina species are highlyaggressive in this new environment and frequently become<strong>the</strong> dominant plant in areas <strong>the</strong>y invade. (Callaway andJosselyn 1992; Cohen and Carleton 1995; Daehler andStrong 1996; Goals Project 1999; Ayres et al. 2003;California Coastal Conservancy 2003; Ayres et al. 2004).In 2000 <strong>the</strong> California Coastal Conservancy established<strong>the</strong> San Francisco Estuary Invasive Spartina Project (ISP) toprovide a regionally coordinated approach to controlling oreradicating non-native Spartina in San Francisco Bay. TheISP includes a monitoring program to map non-nativeSpartina and to assess <strong>the</strong> effectiveness <strong>of</strong> treatmentmethods. In 2000-2001 <strong>the</strong> ISP mapped <strong>the</strong> entire Estuaryusing <strong>the</strong> methods outlined in Collins et al. (2001). In 2003<strong>the</strong> ISP Monitoring Program mapped a subset <strong>of</strong> 28 sites,monitored sites treated in 2002 and 2003, used genetictesting to confirm identifications at known and suspectedinvasion sites, and compared methods for monitoringcordgrass in <strong>the</strong> Estuary.Five species <strong>of</strong> Spartina are currently found in <strong>the</strong> SanFrancisco Bay Estuary including <strong>the</strong> native, S. foliosa. Thefour non-native species currently found in <strong>the</strong> estuary are S.alterniflora, S. densiflora, S. anglica, and S. patens. Hybridsbetween Atlantic smooth cordgrass S. alterniflora, and <strong>the</strong>native Pacific cordgrass S. foliosa (hereafter termed“hybrids”) now threaten <strong>the</strong> ecological balance <strong>of</strong> <strong>the</strong>Estuary and are likely to cause <strong>the</strong> extinction <strong>of</strong> nativePacific cordgrass, choke tidal creeks, dominate newlyrestored tidal marshes, and displace thousands <strong>of</strong> acres <strong>of</strong>existing shorebird habitat (Ayres and Strong, this vol.;Stralberg et al. this vol.; Ayres et al. 2003; Ayres et al.2008). Invasive cordgrasses from <strong>the</strong> San Francisco Estuarycould spread to o<strong>the</strong>r California estuaries through seeddispersal on <strong>the</strong> tides.The 2000-2001 survey found 195 net hectares (ha) (483acres (ac)) <strong>of</strong> non-native Spartina distributed throughoutnearly 16,187 ha (40,000 ac) <strong>of</strong> tidal marsh and 11,736 ha(29,000 ac) <strong>of</strong> tidal flats (Ayres et al. 2004). Net area is <strong>the</strong>coverage if all non-native Spartina plants were contiguouswhile gross area would be all <strong>the</strong> marsh areas that have somenon-native Spartina plants. Of this total, 190 ha (470 ac)were hybrids, 5 ha (13 ac) were S. densiflora, 0.23 ha (0.58ac) were S. patens, and 0.04 ha (0.09 ac) were S. anglica.The hybrids have increased in area 100-fold since <strong>the</strong> 1970s,from just over one ha <strong>of</strong> planted S. alterniflora in 1978(Ayres et al. 2004). It is hypop<strong>the</strong>sized that <strong>the</strong> proliferation<strong>of</strong> hybrids is accelerating <strong>the</strong> rate at which areas are covereddue to <strong>the</strong> evolution <strong>of</strong> greater invasiveness (Ayres et al.2004; Ayres and Strong this vol.; Hall et al. 2006 and this-73-
Chapter 2: Spartina Distribution and Spread<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive Spartinavol.). In addition to <strong>the</strong> physical displacement <strong>of</strong> nativemarsh plants, <strong>the</strong> hybrid invasion threatens <strong>the</strong> geneticintegrity and continued existence <strong>of</strong> <strong>the</strong> native Spartinafoliosa (Ayres et al. 2003).METHODSOverall DescriptionA total <strong>of</strong> 31 estimates <strong>of</strong> area covered by three species<strong>of</strong> non-native Spartina were made at 28 separate samplingsites in 2003 (Table 1). The three species were S. patens, S.densiflora and hybrids. A sample <strong>of</strong> sites was selected toprovide coverage for <strong>the</strong> entire bay shoreline stratified by“region” as defined by <strong>the</strong> Wetlands Goals Project (GoalsProject 1999) (latitude) and “site type.” Field sites wereselected across <strong>the</strong> latitudinal extent <strong>of</strong> <strong>the</strong> non-nativeSpartina spp. invasion in <strong>the</strong> Estuary (Fig. 1). The regionswere North Bay (NB) (2 sites), Central Bay (CB) (21 sites),and South Bay (SB) (5 sites). The site types were I) tidal,micro-tidal, and formerly diked bayland, and back barriermarsh (9 sites); (II) fringing tidal marsh, mud flats andestuarine beaches (7 sites); (III) major tidal sloughs, creeksor flood control channels (5 sites); and (IV) urbanized rock,riprap, docks, boat ramps and marinas (7 sites). At least twomarshes <strong>of</strong> each site type were selected from each <strong>of</strong> <strong>the</strong>three regions <strong>of</strong> <strong>the</strong> Bay. Within each site type six to sevenmarshes were selected.The three non-native species differed in <strong>the</strong>irdistributions among <strong>the</strong> three bay regions. Spartina. patensoccurred at one location, Southampton, in <strong>the</strong> North Baywhere no o<strong>the</strong>r non-native species occurred. Spartinadensiflora occurred at seven locations: one in <strong>the</strong> North Bayand six in <strong>the</strong> Central Bay. At three <strong>of</strong> <strong>the</strong> Central Bay sitesS. densiflora and hybrids both occurred. Two <strong>of</strong> <strong>the</strong>se threesites are adjacent to each o<strong>the</strong>r, that is, Blackie’s Creek runsthrough Blackie’s Pasture. Hybrids occurred at 23 separatesites from <strong>the</strong> Central Bay and <strong>the</strong> South Bay. It was notpossible to sample equal numbers <strong>of</strong> sites within each typeand region due to <strong>the</strong> unequal frequencies <strong>of</strong> appropriatesites, <strong>the</strong> requirement to avoid clapper rails in somelocations and to sample particular sites at particular tideheights, and limited numbers <strong>of</strong> trained field staff andGlobal Positioning System (GPS) units. Never<strong>the</strong>less, asnoted below, <strong>the</strong> sampling in 2003 encompassed <strong>the</strong> fullknown regional extent <strong>of</strong> non-native Spartina speciesdistribution.MappingIn 2003 distribution and abundance <strong>of</strong> non-nativeSpartina were mapped at <strong>the</strong> 28 sample sites and comparedto <strong>the</strong> distribution and abundance at those locations in 2001.Overall methods followed Collins et al. (2001) with somemodifications.At each sampling site observers mapped <strong>the</strong> locationand areal extent <strong>of</strong> non-native Spartina using a GPS dataTable 1. Change in Area Covered Between 2001 and 2003 Using FieldMeasurements and Field Estimates*at 28 sites for three Spartina taxa.SitesTaxaArea in Area in2001 (ac) 2003 (ac)Area in2001(squaremeters)Area in2003(squaremeters)Changein Area2001 to2003Site Type IBunker Marsh* Hybrids 0.39 1.40 1580.11 5665.59 259%Citation Marsh* Hybrids 0.51 1.93 2059.74 7803.41 279%Cogswell Marsh(North Quadrant)*Hybrids 0.37 1.32 1503.16 5334.08 255%Piper Park West S. densiflora 0.02 0.08 99.92 318.40 219%SouthamptonMarshS. patens 0.31 0.05 1244.49 196.99 -84%Point Pinole S. densiflora 0.00 0.00 2.99 6.39 114%Palo Alto Baylands Hybrids 0.12 0.15 478.26 618.49 29%Corte MaderaMarsh Reserve 1Corte MaderaMarsh Reserve 2S. densiflora 0.011 0.014 44.95 60.75 35%Hybrids 0.01 0.05 26.46 214.92 712%Pickleweed Park S. densiflora 0.49 0.03 1964.07 118.73 -94%Site Type IIEmeryville West Hybrids 0.07 1.59 282.60 6430.15 2175%Coyote CreekMarshAlameda Island –N. Elsie Roemer*Hybrids 0.09 0.06 353.25 233.15 -34%Hybrids 0.29 0.98 1171.89 3948.94 237%Blackie’s Pasture 1 S. densiflora 0.021 0.020 84.12 82.66 -2%Blackie’s Pasture 2 Hybrids 0.01 0.08 41.37 330.90 700%Ideal Marsh* Hybrids 0.26 0.88 1070.72 3541.00 231%Richmond InnerHarbor – SteegeMarshHybrids 0.01 0.02 32.19 100.46 212%Bayshore Park Hybrids 0.05 0.25 168.19 1018.84 506%Site Type IIIBlackie’s Creek 1 Hybrids 0.03 0.02 108.33 93.97 -13%Blackie’s Creek 2 S. densiflora 0.00 0.00 12.06 8.46 -30%Colma Creek Hybrids 2.36 7.16 9551.11 28957.46 203%Corte MaderaCreekS. densiflora 1.19 2.70 4802.16 10948.30 128%San Leandro Creek Hybrids 2.16 3.83 8760.60 15481.79 77%San Mateo Creek Hybrids 0.20 0.78 825.41 3172.16 284%Site Type IVCoyote Pt Marina Hybrids 0.35 0.74 1408.81 3004.87 113%Oakland InnerHarborHybrids 2.74 5.40 11087.72 21685.73 96%Yosemite Slough Hybrids 0.02 0.12 75.47 476.02 531%India Basin Hybrids 0.10 0.01 408.20 41.47 -90%Pier 94 Hybrids 0.04 0.03 171.72 129.50 -25%Pier 98/Heron’sHead (treat tookplace in 2002)Loch LomondMarinaHybrids 0.002 0.009 8.83 37.40 324%Hybrids 0.005 0.016 19.63 64.98 231%Site and Marsh Types:Type I. Former Diked Bayland/Microtidal/Tidal/Back Barrier MarshType II. Fringing Tidal Marsh/Mudflats/Estuarine BeachesType III. Major Tidal Slough, Creek or Flood Control ChannelType IV. Urbanized rock, riprap, dock, ramp, marina.-74-
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FORWARD & ACKNOWLEDGEMENTSThe <stro
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TABLE OF CONTENTSForward & Acknowle
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Community Spartina Education and St
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CHAPTER ONESpartina Biology
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Chapter 1: Spartina Biology
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CHAPTER THREEEcosystem Effects <str
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