![]() This phenomenon has been observed in the San Francisco Estuary, where a largely contiguous tidal wetland complex has been converted to a primarily open-water system (Whipple et al. Dramatic declines in tidal wetland affect the relative abundance of other habitat types (e.g., bays or mudflats make up a higher proportion of remaining habitat), which can influence organisms across multiple trophic levels and in multiple habitats. 2019), a particularly biologically productive component of the estuary milieu. In most estuaries, the habitat type most frequently lost is tidal wetland (Dahl 2011 Brophy et al. 1977 Pimm and Lawton 1980 Thompson et al. Organisms at higher trophic levels, especially mobile omnivores feeding across various habitats (e.g., fishes Pyke et al. For organisms at lower trophic levels (e.g., invertebrates), a decline or change in productivity can have catastrophic impacts on local populations because their relatively limited mobility and short lifespans bind them to local production (Orsi and Mecum 1996 Kimmerer 2002). Habitat loss can reduce the quantity or availability of different organic matter sources to the ecosystem (Cloern et al. 2012), with diverse intertidal and subtidal habitats, and with severe human impacts, which include eutrophication, species invasions, and habitat loss (Kennish 2002). 2005).Įstuaries are particularly complex, with a complicated mix of trophic contributions from marine and freshwater inputs (Fry and Smith 2002 Hoffman et al. 1997) because diverse sources of productivity maintain consistent support for higher trophic levels (McCann et al. These spatiotemporal differences stabilize complex food webs (Winemiller 1996 Polis et al. For example, phytoplankton, benthic microalgae, and marsh vegetation were all important to local consumers in Plum Island Sound, MA, USA, but the relative importance differed depending on location within the estuary (Deegan and Garritt 1997). ![]() Although each source may be an important contributor, the relative importance of each differs substantially across space and time (Peterson et al. 2002), and terrestrial vegetation (Chanton and Lewis 2002 Zeug and Winemiller 2008 Tanentzap et al. 1995 Kwak and Zedler 1997), submersed aquatic vegetation (SAV Kitting et al. 2008), macroalgae and benthic microalgae (Currin et al. 1985) however, estuarine consumers also use many other organic-matter sources such as phytoplankton (Deegan and Garritt 1997 Galvan et al. Many estuarine food webs appear to be fueled by exported wetland detritus (Teal 1962 Odum 1980 Peterson et al. Ecosystem restoration may improve with emphasis on restoring a wide variety of primary producers to support consumers. Availability of primary producers differs seasonally and across multiple spatial scales, helping to buffer environmental variability and thus enhancing food web resilience. ![]() Most fishes utilized multiple primary producers and showed little segregation between pelagic and littoral food webs among habitats. Using stable isotope analysis coupled with a Bayesian mixing model, we identified significant differences in primary-producer contribution to fishes and invertebrates across habitats and seasons, especially in the relative contribution of submersed aquatic vegetation and phytoplankton. In this study, we evaluated the importance of primary producers to adult fishes in three closely spaced subregions that represented disparate habitat types (a tidal wetland channel, a turbid backwater channel, and a deep open-water channel), each a potential outcome of local restoration projects. Previous studies have documented broad spatial differences in the importance of primary producers to fishes within the Upper San Francisco Estuary, California, including separation between pelagic and littoral food webs. However, identifying the relative importance of each producer to consumers is difficult, particularly for fishes that utilize multiple food sources due to both their mobility and their generally high trophic levels. Estuarine food webs are fueled by multiple different primary producers.
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