Trophic structure and avian communities across a salinity gradient in evaporation ponds of the San Francisco Bay estuary

Abstract

Commercial salt evaporation ponds comprise a large proportion of baylands adjacent to the San Francisco Bay, a highly urbanized estuary. In the past two centuries, more than 79% of the historic tidal wetlands in this estuary have been lost. Resource management agencies have acquired more than 10 000 ha of commercial salt ponds with plans to undertake one of the largest wetland restoration projects in North America. However, these plans have created debate about the ecological importance of salt ponds for migratory bird communities in western North America. Salt ponds are unique mesohaline (5-18 g l )1 ) to hyperhaline (>40 g l )1 ) wetlands, but little is known of their ecological structure or value. Thus, we studied decommissioned salt ponds in the North Bay of the San Francisco Bay estuary from January 1999 through November 2001. We measured water quality parameters (salinity, DO, pH, temperature), nutrient concentrations, primary productivity, zooplankton, macroinvertebrates, fish, and birds across a range of salinities from 24 to 264 g l )1 . Our studies documented how unique limnological characteristics of salt ponds were related to nutrient levels, primary productivity rates, invertebrate biomass and taxa richness, prey fish, and avian predator numbers. Salt ponds were shown to have unique trophic and physical attributes that supported large numbers of migratory birds. Therefore, managers should carefully weigh the benefits of increasing habitat for native tidal marsh species with the costs of losing these unique hypersaline systems.

Habitat use of an endangered cyprinodontid fish in a saline wetland of the Iberian Peninsula (SW Mediterranean Sea)

“…These habitat conditions may favour the species, since well-developed meadows of submerged vegetation could provide refuge against predators and abundant food resources for this species (Alcaraz et al, 2008;OlivaPaterna et al, 2009). Furthermore, it has been demonstrated that lower values of salinity in these systems promote high diversity and biomass of macroinvertebrates (Takekawa et al, 2006;López et al, 2010), which are potential prey for A. iberus. In a study on Aphanius fasciatus (Nardo, 1827), Leonardos et al (1996) reported that populations of this species inhabiting lower salinity habitats had higher growth rates and lower values of mortality due mainly to the abundant presence of aquatic macrophytes, which offered abundant food resources and refuge against piscivorous birds.…”

Prokaryotic Community Structure Driven by Salinity and Ionic Concentrations in Plateau Lakes of the Tibetan Plateau

“…Increasing salinity was found to be correlated with a reduced richness of plant and animal species (5,6) and of microbial community diversity in some cases (7,8). However, this pattern is not consistently observed for all microbial communities (9)(10)(11)(12)(13)(14).…”

A Bioenergetics Approach to Setting Conservation Objectives for Non-Breeding Shorebirds in California’s Central Valley

“…For example, invertebrate productivity can be affected by vegetation composition and cover, topography and water depth diversity, duration of flooding, and salinity (Severson 1987;Batzer and Resh 1992;Batzer and Wissinger 1996;Takekawa et al 2006;Batzer 2013). However, invertebrate responses to management may be taxonand region-specific, requiring careful research to identify effective strategies (Batzer 2013).…”