An Urban Estuary in a Changing World PDF Download

Author: Andrew Louis Chang
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Languages : en
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Book Description
Estuarine and coastal ecosystems face both large scale physical environmental stresses from climate change and local scale community changes, including non-native species introductions. In northern California, USA, climate change projections indicate increasingly severe droughts in the future punctuated by more frequent, intense winter storms, significantly affecting freshwater outflow to estuaries like San Francisco Bay. Using long-term physical and biological data sets coupled with experiments, I found drastic changes in epifaunal communities in the Bay between years with extreme high and low freshwater outflow (Chapter 1). In dry years (low outflow), competition determines community composition, but in wet years (high outflow), low salinity stress shifts the community to being recruitment limited, with community membership determined by the availability of larvae to recruit. Shifts in outflow extremes drive changes in the dominant species, resulting in altered community performance (Chapter 2). I experimentally tested the effect of functional group diversity on community performance in different outflow regimes. Communities containing more functional groups generally occupied more space, but the strength of this effect varied from year to year. In the absence of normally dominant species during a wet year, resident community functional group diversity had no effect on subsequent invasion by non-resident species. These results suggest that outcomes of short-term, unreplicated studies of biodiversity-ecosystem function relationships may thus be contingent on prevailing conditions. Finally, I assessed the risk posed by the aquarium fish trade for introducing non-native fish species to the San Francisco Bay-Delta using an inventory of fish species for sale, a model comparing fish physiological tolerances to environmental parameters, and a telephone survey of store representatives' knowledge and attitudes toward invasions (Chapter 3). This analysis showed that the local aquarium trade includes at least five and as many as twenty-seven species that could potentially survive in the Bay-Delta. Management efforts for this vector should focus on improving labeling and identification of fish species in stores, expanding available information on fish physiological tolerances, educating customers and store employees about the risks of pet release, and providing better options for responsible disposal of unwanted fish.