The introduction and spread of smooth cordgrass (Spartina alterniflora) in South San Francisco Bay

Spartina alterniflora was first introduced into south San Francisco Bay in the 1970’s. Since that time it has spread to new areas within the south bay and is especially well established at four sites. The spread of this introduced species was evaluated by comparing its vegetative and reproductive characteristics to the native cordgrass, Spartina foliosa. The characters studied were intertidal distribution, phenology, aboveground and belowground biomass, growth rates, seed production, and germination rates. Spartina alterniflora has a wider intertidal distribution than S. foliosa and outproduced the native cordgrass in all aspects that were studied. These results indicate that the introduced species has a much better chance of becoming established in new areas than the native species, and once established, it spreads more rapidly vegetatively than the native species. Spartina alterniflora is likely to continue to spread to new areas in the bay and displace the native plant. In addition, this introduced species may effect sedimentation dynamics, available detritus, benthic algal production, wrack deposition and disturbance, habitat structure for native wetland animals, benthic invertebrate populations, and shorebird and wading bird foraging areas. *** DIRECT SUPPORT *** A01BY058 00013     

Loss and recycling of amino acids and protein from smooth cordgrass (Spartina alterniflora) litter

We investigated the source and composition of free and protein-bound amino acids during the decomposition ofSpartina alterniflora Loisel in laboratory percolators and in a field experiment in the Great Sippewissett Marsh (Falmouth, Massachusetts). In the percolator experiment, 50% of the nitrogen (N) could be extracted fromS. alterniflora litter in 16 d. This extract consisted of dissolved free amino acid N (28%), suspended protein amino acid N (16%), inorganic N (12%), and nitrogen from unidentified compounds (44%). Much of the free amino acid nitrogen was utilized by detrital microorganisms, resulting in a greater loss of suspended protein amino acid (SPAA) nitrogen from the biologically active percolator due to microbials biomass. Suspended microbial mass accounted for at least 50% of the SPAA washed out of the biologically active percolator. In the field study, 38% of the original litter nitrogen was leached fromS. alterniflora litter in litterbags during the first 13 d. After this initial leaching period, the concentration (41% to 69% of total nitrogen) and composition of most amino acids bound in the litter did not change over the 23-month period of the experiment. Increases in microbial protein did not account for increases in total nitrogen which occurred during the decomposition of the litter. Similarly, adsorbed ammonium did not appear to be responsible for this increase.     

Epiphytic nitrogen fixation associated with standing dead shoots of smooth cordgrass, Spartina alterniflora

N₂ fixation associated with the epiphytic community on standing dead Spartina alterniflora shoots was examined in both a natural and transplanted salt marsh in North Carolina. Acetylene reduction (AR) assays were conducted over a 24-mo period to estimate N₂ fixation rates on standing dead stems and leaves. In the natural salt marsh, mean AR rates ranged from 0.5 nmol C₂H₄ cm^?2 h^?1 to 14 nmol C₂H₄ cm^?2 h^?1, while in the transplanted marsh mean AR rates ranged from 1 nmol C₂H₄ cm^?2 h^?1 to 33 nmol C₂H₄ cm^?2 h^?1. Diel AR activity of epiphytic communities in both marshes varied seasonally. Midday incubations yielded higher AR rates than nighttime incubations in the spring, while midday incubations in late summer and fall generally yielded AR rates equal to or lower than nighttime incubations. Desiccation during low tides occasionally repressed AR activity, although AR rates quickly rebounded with wetting. AR activity was localized in the epiphytic community, rather than in the underlying Spartina stem material. Based on the measured AR rates and the density of standing dead stems, the annual input of new N to the natural salt marsh via epiphytic N₂ fixation is estimated to be 2.6 g N m^?2 yr^?1. The estimate of annual input of new N to the transplanted marsh is 3.8 g N m^?2 yr^?1. These estimates should be added to previous estimates of N₂ fixation in marsh sediments to estimate the total contribution of new nitrogen to salt marsh nitrogen budgets.     

The influence of subsurface hydrology on nutrient supply and smooth cordgrass (Spartina alterniflora) production in a developing barrier island marsh

The supply of nutrients from surface and subsurface water flow into the root zone was measured in a developing barrier island marsh in Virginia. We hypothesize that high production of tall-formSpartina alterniflora in the lower intertidal zone is due to a greater nitrogen input supplied by a larger subsurface flux. Individual nitrogen inputs to the tall-form and short-formS. alterniflora root zones were calculated from water flow rates into the root zone and the nutrient concentration corresponding to the source of the flow. Total dissolved inorganic nitrogen (DIN) input (as ammonium and nitrate) was then calculated using a summation of the hourly nutrient inputs to the root zone over the entire tidal cycle based on hydrologic and nutrient data collected throughout the growing season (April–August) of 1993 and 1994. Additionally, horizontal water flow into the lower intertidal marsh was reduced experimentally to determine its effects on nutrient input and plant growth. Total ammonium (NH₄ ⁺) input to the tall-formS. alterniflora root zone (168 μmoles 6 h^?1) was significantly greater relative to the short-form (45 μmoles 6 h^?1) during flood tide. Total NH₄ ⁺ input was not significantly different between growth forms during ebb tide, and total nitrate (NO₃ ^?) and total DIN input were not significantly different between growth forms during either tidal stage. During tidal flooding, vertical flow from below the root zone accounted for 71% and horizontal flow from the adjacent mudflat accounted for 19% of the total NH₄ ⁺ input to the tall-formS. alterniflora root zone. Infiltration of flooding water accounted for 15% more of the total NO₃ ^? input relative to the total NH₄ ⁺ input at both zones on flood tide. During ebb tide, vertical flow from below the root zone still accounted for the majority of NH₄ ⁺ and NO₃ ^? input to both growth forms. After vertical flow, horizontal subsurface flow from upgradient accounted for the next largest percentages of NH₄ ⁺ and NO₃ ^? input to both growth forms during ebb tide. After 2 yr of interrupted subsurface horizontal flow to the tall-formS. alterniflora root zone, height and nitrogen content of leaf tissue of treatment plants were only slightly, but significantly, lower than control plants. The results suggest that a dynamic supply of DIN (as influenced by subsurface water flows) is a more accurate depiction of nutrient supply to macrophytes in this developing marsh, relative to standing stock nutrient concentrations. The dynamic subsurface supply of DIN may play a role in spatial patterns of abovegroundS. alterniflora production, but determination of additional nitrogen inputs and the role of belowground production on nitrogen demand need to also be considered.     

The effects of crude oil and remediation burning on three clones of smooth cordgrass (Spartina alterniflora loisel.)

Burning has been employed as an oil spill remediation technique in coastal marshes, even though the combined and interactive effects of oil and burning on vegetation are poorly understood. Variation among clones of perennial marsh grasses in response to these perturbations is not known. We performed a greenhouse experiment designed to assess the effects of Venezuelan crude oil alone and of oil followed by burning on three clonal genets ofSpartina alterniflora. The fully-crossed 6-mo experiment involved five dosages of oil (0 l m⁻², 4 l m⁻², 8 l m⁻², 16 l m⁻², and 24 l m⁻²) and two burn treatments (burned or unburned) applied to ramets from three clones. All oil-only dosages reduced survival, but burning after oiling (oil + burn treatments) increased survival relative to oil-only groups in all except the highest two oil dosages. Higher oil-only treatments also reduced ramet densities and inhibited density increases over 6 mo. Burning after treatment with the 16 l m⁻² oil concentration allowed increased production of new ramets, but burning exacerbated the negative impacts on ramet density at the oil concentration of 24 l m⁻². At some intermediate oil dosages, burning remediated the negative effects of oil on aboveground biomass production and growth in height. There was a significant effect of oil-only treatments on numbers of flowering ramets produced, in which two clones responded with decreased flower production and one exhibited increased flowering. There was no main effect of oil + burn on flowering. There were significant among-clones differences in all response variables to one or both treatments. Our experiment demonstrates that burning of oiledS. alterniflora marshes may have little measurable effect at low levels of Venezuelan crude oil, can remediate the effects of oil at intermediate oil concentrations, but can increase the negative impacts at high concentrations of oil. These results indicate that oil spills have the potential to adversely affect genetic diversity inS. alterniflora populations by eliminating some sensitive clonal variants or changing the relative dominance of genets. These results suggest certain clones may be better suited for phytoremediation or restoration planting following oil spills.     

Direct-count estimates of fungal and bacterial biovolume in dead leaves of smooth cordgrass (Spartina alterniflora Loisel.)

Two types of hyphal-extraction, direct-count methods of estimating fungal biovalume in standing-dead, autumn leaves of Spartina alterniflora were compared with a clearing+staining method which does not require homogenization. Bacterial biovolume also was estimated, by an acridine-orange direct-count method. Type of homogenization had little effect on measured fungal volume, but counts made using water-soluble-aniline-blue epifluorescence were consistently lower than those made using phase-contrast (by 6–10x). Clearing+staining could not be used to estimate hyphal lengths, but was of use in estimating total ascocarp volume (=0.06 mm³ per mm³ of leaf). Estimated fungal hyphal volume was approximately 0.27 mm³ per mm³ of leaf. Bacterial volume was <3% of fungal volume.     

Impact of high herbivore densities on introduced smooth cordgrass,Spartina alterniflora,invading San Francisco Bay,California

Spartina alterniflora, smooth cordgrass, invading San Francisco Bay, California (USA), is attacked by high densities of a plant hopper, Prokelisia marginata, and a mirid bug, Trigonotylus uhleri. Both herbivores are sap-feeders. We investigated the impact of these herbivores on S. alterniflora's growth rate, vegetative spread, and seed production by manipulating herbivore densities in the field and in a greenhouse. Herbivore densities in the field peaked in early fall, with P. marginata averaging more than 300 individuals per mature culm of S. alterniflora (about 100,000 per m²) and T. uhleri densities exceeding 10 per culm (about 3,000 per m²). Field reductions of herbivore densities by approximately 70% with insecticidal soap did not result in greater vegetative growth rates or lateral spread of plants; plants grew vigorously with the highest densities of insects. In the greenhouse study, conducted with seedlings, herbivory significantly reduced plant mass and tiller number in some but not all replicate herbivory treatments. In both field and greenhouse, there were significant differences between some clones' growth rates independent of herbivory. Inflorescence production in the field was not affected by reduced-herbivory treatments. Seed set was low under conditions of both natural and reduced herbivory, averaging 0.4%. Despite densities of P. marginata and T. uhleri that are much higher than typically observed in areas where S. alterniflora is native, herbivory by these particular insects appears to have little impact and in unlikely to limit S. alterniflora’s spread through San Francisco Bay. *** DIRECT SUPPORT *** A01BY070 00009     

Factors controlling aboveground Spartina alterniflora (Smooth cordgrass) tissue element composition and production in different-age barrier island marshes

Aboveground production and tissue element composition of Spartina alterniflora were compared in bareier island marshes of different age off the Eastern Shore of Virginia. The marshes were also characterized by physical and chemical parameters of the substrate. The results suggest that sediment nutrient stock do not directly control the spatial pattern of element content or production of S. alterniflora between these marshes. Elevated salinity likely limits the nitrogen uptake capability of S. alterniflora in the high marsh, which, in turn, controls leaf tissue nitrogen content of plants within individual sites. Low substrate redox potential may control the spatial pattern of nitrogen uptake between the different-age marsh sites, loading to more favorable growing conditions at the low stations of the young marsh sites where values of tissue nitrogen and production are highest. Tissue phosphorus did not differ between, or within the marsh sites. The result of a fertilization experiment suggest that nitrogen, and not phosphorus, is the primary limiting nutrient in this sytem. This indicates that nutrient limitation and other stresses work in conjunction to control tissue element content and macrophyte production at these marsh sites. Spatial variability of factors that control leaf tissue nitrogen and production is likely related to topography and grain size of an individual marsh, which is a function of marsh age. Most studies in different-age marshes have compared transplanted marshes to older, natural marshes. This work is one of few studies comparing developing and mature natural, marshes on barrier islands.     

Expansion rates and recruitment frequency of exotic smooth cordgrass, Spartina alterniflora (Loisel), colonizing unvegetated littoral flats in Willapa Bay, Washington

We estimated lateral growth rates of nonindigenous Spartina alterniflora patches in Willapa Bay, Washington, over three intervals between 1970 and 1990, to reconstruct recruitment frequency since S. alterniflora was initially introduced c. 1890. Black and white aerial photographs (1∶24,000 scale) of four representative sites where S. alterniflora has invaded were analyzed. Individual patches were digitized on a computer, and diameter and area were computed for each patch for all years and sites sampled using CAD software. Lateral growth rates of individual. S. alterniflora patches increased linearly at 79.3 (± 1.674 SE) cm yr⁻¹. Back calculations of origin dates for individual patches based on mean lateral growth rates indicate that recruitment of new patches has been episodic and increasing in frequency since initial introduction. Environmental factors such as sea surface temperature, sea level, and precipitation may account for some of this recruitment variability. These data may be useful in existing and future models of S. alterniflora expansion in Pacific Northwest estuaries.     

Genetic effects of a large-scaleSpartina alterniflora (smooth cordgrass) dieback and recovery in the northern Gulf of Mexico

A large-scale dieback event struck marshes along the northwestern Gulf of Mexico coast during summer 2000, in apparent response to a prolonged and severe drought. Along the Louisiana coast, large areas of the dominant marsh species,Spartina alterniflora, turned brown, followed by death of at least the aboveground structures of entire plant mortality. Key ecological and genetic measures were studied in a dieback-affected marsh in southwest Louisiana (C83 marsh, Sabine National Wildlife Refuge), for which existed predieback ecologic and genetic datasets. Effects on genetic diversity only were studied in a second set of sites in southeastern Louisiana (near Bay Junop), where the dieback was more widespread. We hypothesized that stem density, live aboveground biomass, and genetic diversity would be significantly reduced compared to predieback conditions and to nearby unaffected marshes. Stem densities and biomass levels approached predieback conditions 14 months after first observance of the dieback in the Sabine marsh and were similar to or exceeded the same measures for a nearby unaffected marsh. DNA extracted from leaf samples in the Sabine and Bay Junop sites was used to construct genotype profiles using AFLPs and analyzed using the complement of Simpson’s Index (1-D), the richness measure G/N, average heterozygosity <H>, and the estimated proportion of polymorphic genes <P>. Genetic diversity was relatively unaffected by the dieback at either the Sabine or Bay Junop sites. Evidence from field observations and the results of the genetic analyses suggest that seedling recruitment is an important factor in the recovery of both the Bay Junop and C83 sites, although re-growth from surviving below-ground rhizomes appeared to dominate recovery at the latter site. Survival of below-ground structures, leading to the rapid recovery observed, indicates a high level of resilience of the Sabine marsh to drought-induced stress. Still, the genetic diversity ofS. alterniflora-dominated marshes may be promoted by occasional disturbance events, which produce open areas in which seedling recruitment can occur.     

Measurement of cordgrass,Spartina alterniflora,production in a macrotidal estuary,Bay of Fundy

A one-year field study was conducted of the growth, mortality, and loss dynamics of aSpartina alterniflora low marsh in the Minas Basin, a macrotidal estuary at the head of the Bay of Fundy. Data were used to examine the suitability of four methods for estimating annual net aerial primary production (NAPP) of a marsh subject to energetic tidal flooding. Shoots start to grow in April and reach maximum height (about 0.5 m) and weight in October. Maximum shoot density (900–1,600 m^?2) occurs around June and drops thereafter due to the export of entire shoots. The average shoot produces about seven leaves and at least 2–3 are lost during the growing season. All remaining vegetation dies before the end of November. Methods based on harvesting vegetation underestimated NAPP, especially at lower elevations where export is greater due to more frequent and prolonged tidal flooding. The highest NAPP values, on the order of 500–600 g m^?2 y^?1, were obtained using methods based on the population dynamics of individual shoots. These methods are recommended for energetic tidal environments because they include the production of vegetation exported during the growing season.     

A method for quantifying living roots of Spartina (cordgrass) and Juncus (needlerush)

Quantifying living roots in a marsh is a necessary but difficult task in wetland research. The two main difficulties usually encountered are distinguishing living from dead roots and processing a dense mat of fine roots. We found that living roots of salt-marsh plants release much more dissolved organic carbon (DOC) in boiling water than dead roots. Based on the finding, we developed a DOC procedure to quantify living roots of Spartina alterniflora and Juncus roemerianus. The DOC released in boiling water is a function of root activity, and the amount released can be used to calculate the living root biomass of a sample. The amount of living roots determined by the DOC method correlated well with the amount of living roots determined by the manual, sorting method (r² = 0.78, p<0.01). The DOC method is more objective, precise, and much less tedious than the manual sorting method.     

Decomposition of saltmeadow cordgrass (Spartina patens) in Louisiana coastal marshes

In Louisiana, plant production rates and associated decomposition rates may be important in offsetting high rates of land loss and subsidence in organic marsh soils. Decomposition ofSpartina patens shoot and leaf material was studied by using litter bags in mesohaline marshes in the Barataria and Terrebonne basins of coastal Louisiana.Spartina patens decomposed very slowly with an average decay constant of 0.0007, and approximately 50% of the material remained after 2 years in the field. Material at the Barataria site decomposed faster than did Terrebonne material with trend differences apparent during the first 150 days. This difference might be explained by the higher content of phosphorus in the Barataria material or a flooding period experienced by the Barataria bags during their first 10 days of deployment. Nitrogen and carbon content of the plant material studied did not differ between the two basins. We detected no consistent significant differences in decomposition above, at, or below sediment/water level. BecauseS. patens is the dominant plant in these marshes, and because it is so slow to decompose, we believe thatS. patens shoots are an important addition to vertical accretion and, therefore, marsh elevation.     

Evaluating the progress of restored cordgrass (Spartina foliosa) marshes: Belowground biomass and tissue nitrogen

We report the first data on belowground tissue mass and nitrogen (N) concentration forSpartina foliosa in southern California, assessing one natural and two constructed marshes on San Diego Bay. Biomass at the natural marsh was low compared to that of otherSpartina spp., but higher than values reported forS. foliosa in northern California. In sandy constructed marshes planted 5 and 10 years before this study,S. foliosa had lower belowground tissue N, lower N crop (%N×biomass), and shallower roots than in the adjacent natural marsh. We took advantage of a 2-yr, large-scale fertilization project being performed in the older constructed marsh and examined biomass and N storage after N additions. Although there was a trend toward N accumulation with fertilization, N crop remained at approximately 50% of natural marsh levels, unlike the large aboveground responses to N addition in our previous studies. Lower belowground reserves help to explain poor aerial growth in the created marshes and suggest the need for finer sediments (with greater potential for holding and supplying nutrients) to sustain (S. foliosa. While fine sediments are beginning to accumulate on the surface of the created marshes, vertical accretion is more likely to shift the plant community toward other species than to enhanceS. foliosa growth. We suggest salvaging and importing fine, organic marsh sediments or providing organic amendments to establish proper substrate conditions. Overexcavating and allowing fine sediments to accumulate remains an option, although the time scale is unpredictable due to the stochasticity of accretion events.     

Growth dynamics of cordgrass,Spartina alterniflora loisel., on control and sewage sludge fertilized plots in a Georgia salt marsh

Seasonal plant growth dynamics were followed for a year in undisturbed plots of tall and short formSpartina alterniflora Loisel. and in plots of short formS. alterniflora which were enriched with sewage sludge at a rate of 100 g dry sludge m^?2wk^?1, corresponding to a nitrogen enrichment of 2 g N m^?2wk^?1. Monthly determinations of aboveground live and dead biomass, density of live stems, the ratio of number of young shoots to total number of shoots, and belowground mass of macro-organic matter to a depth of 30 cm were made for each area. Sludge fertilization increased the live biomass of the short formS. alterniflora by up to 150% of the control live biomass, but had little effect on the dead biomass, stem density, or proportion of young shoots. There was a trend of increased amount of belowground macro-organic matter in fertilized compared to control plots during the last 6 months of the study. In all areas, there was a marked decrease in the proportion of young shoots from winter to early summer, followed by a rapid increase in the percent of young shoots from late summer to fall. Sampling of plots 7 and 20 months after termination of sludge enrichment showed higher plant biomass and % N content in surface soils, but no difference in N content of live plant tissue, in fertilized compared to unfertilized marsh. After 20 months, about half of the sludge nitrogen remaining in the soils of the fertilized plots had disappeared.     

Productivity of cordgrass,Spartina alterniflora,estimated from live standing crops,mortality, and leaf shedding in a Virginia salt marsh

Net annual productivity of tall and medium form cordgrass,Spartina alterniflora, was estimated by a new clip sampling method in a sloping foreshore salt marsh at Wallops Island, Virginia. This method measured live standing crops only, to avoid problems of measuring dead biomass inherent in other methods. Losses from live standing crops by shoot mortality and by leaf shedding were estimated from these measurements and added separately to production of live tillers and of live culms. This allowed quantification of various components of production.Spartina tillering in different zones of the marsh produced 62 to 211 g dry weight per m² per yr. Tiller mortality removed 37 to 106 g per m² per yr from live standing crops. Culms produced 348 to 1,132 g per m² before flowering and die-back. Culm mortality removed 28 to 246 g per m² before flowering. Leaf shedding removed an additional 83 g per m² in tall formSpartina. Altogether, net annual productivity These estimates are much higher than previous estimates of productivity and standing crops inSpartina marshes nearby.     

Stem Borer Frequency and Composition in Healthy <Emphasis Type="Italic">Spartina alterniflora</Emphasis> (smooth cordgrass) and Dieback Zones in a Southern Atlantic Coast Salt Marsh

Unprecedented Spartina alterniflora (smooth cordgrass) dieback has recently plagued Atlantic and Gulf coast US salt marshes. The hypothesized drivers of dieback vary geographically but include drought and herbivory. Stem-boring insect larvae may also contribute to dieback, but have thus far been overlooked. Here we describe stem borer frequency and composition among healthy S. alterniflora morphs (tall and short) and dieback zones in Dean Creek Marsh on Sapelo Island, GA. Overall stem borer frequency was highest in tall morph S. alterniflora and dieback zones (present in 46.7% and 39.5%, respectively). Healthy habitat types were characterized by six stem borer families with only two of those families observed in dieback zones. Taxa from these two families, previously reported by others to cause stem death, were found at their highest frequency in dieback zones. Although we cannot infer causation, our results raise the possibility of stem borers contributing to the formation of dieback zones, meriting further research.     

A review of environmental and genetic factors that affect height inSpartina alterniflora loisel. (Salt marsh cord grass)

The salt marsh cord grass,Spartina alterniflora Loisel., occurs in markedly distinct short and tall growth forms. Both forms have the same number of chromosomes, although polyploidy is well established in the genus. Previous studies have shown that height is primarily affected by nitrate availability and environmental stresses such as increased soluble salt concentrations. These studies have shown that, within a marsh, height differences cannot be attributed to genetic, chromosomal differences or electrophoretic banding. However, more subtle genetic differences may be involved. Other studies suggest that between marshes,S. alterniflora, in response to a latitudinal gradient on the Atlantic coast, has evolved ecotypes differing in height, color and flowering period. This review paper points out that plant height inS. alterniflora may be determined by a combination of environmental and genetic factors.     

Episodic colonization of an intertidal mudflat by native cordgrass (<Emphasis Type="Italic">Spartina foliosa</Emphasis>) at Tijuana Estuary

Following heavy winter storms and sedimentation in 1993,Spartina foliosa (Pacific cordgrass) clones established on a 6.5-ha mudflat in Tijuana Estuary, with over 80 new clones counted by 1997. El Niño Southern Oscillation (ENSO) storms in 1993 apparently facilitated the habitat conversion through river flooding, which caused a temporary reduction in soil salinity and delivered large volumes of sediment. Extreme sedimentation likely raised mudflat elevations enough to allowSpartina establishment. We hypothesized that clones, once established, increased sedimentation in a positive feedback loop leading to accelerated habitat conversion. We collected data on elevation,Spartina expansion, and sediment accretion in two consecutive years (1998–1999). The elevation range of the mudflats in 1998 (0.5–0.83 m NGVD) was within the elevation range ofSpartina at this site (0.39–0.83 m NGVD), indicating that remaining mudflats are at elevations suitable for further expansion. Sediment accretion ranged from 4.0–12.7 cm between 1997–1998 (ENSO conditions), but was close to long-term averages (? cm yr^?1) in 1998–1999 (nonflood year) indicating how susceptible Tijuana Estuary is to sedimentation from episodic storms. Although accretion rates were similar withinSpartina clones and on bare mudflats over the ENSO winter, clones were typically dome-shaped suggesting higher sediment retention rates within clones. The radial expansion rates of clones (1.31±0.25 m in 1998; 1.12±0.07 m in 1999) approximated the maxima reported for this species and were not related to clone size or vigor. Conditions on the mudflat appear ideal forSpartina growth, masking differences that might otherwise be observed. Given the likelihood of sedimentation-driven habitat conversion in southern California and other Mediterranean-type estuaries, management efforts are needed to address sedimentation issues on a watershed scale. We recommend that wetland restoration projects in southern California include large areas of intertidal mudflat, both to maintain habitat for shorebird feeding and to allow colonization by salt marsh vegetation.