Bioavailability of organic matter in a highly disturbed estuary: The role of detrital and algal resources

Abstract

The importance of algal and detrital food supplies to the planktonic food web of a highly disturbed, estuarine ecosystem was evaluated in response to declining zooplankton and fish populations. We assessed organic matter bioavailability among a diversity of habitats and hydrologic inputs over 2 years in San Francisco Estuary's Sacramento-San Joaquin River Delta. Results show that bioavailable dissolved organic carbon from external riverine sources supports a large component of ecosystem metabolism. However, bioavailable particulate organic carbon derived primarily from internal phytoplankton production is the dominant food supply to the planktonic food web. The relative importance of phytoplankton as a food source is surprising because phytoplankton production is a small component of the ecosystem's organicmatter mass balance. Our results indicate that management plans aimed at modifying the supply of organic matter to riverine, estuarine, and coastal food webs need to incorporate the potentially wide nutritional range represented by different organic matter sources.

Terrestrial deposits on intertidal sandflats: sediment characteristics as indicators of habitat suitability for recolonising macrofauna

“…Our study provides further evidence to show that, while terrestrially derived organic material commonly enters estuaries in relatively large amounts when associated with sedimentation events, it does not necessarily represent a nutritionally important or utilisable food source (e.g. Sobczak et al 2002).…”

Strong evidence for terrestrial support of zooplankton in small lakes based on stable isotopes of carbon, nitrogen, and hydrogen

“…Given the allochthonous nature of combined dissolved and particulate organic matter in these lakes, it is striking that terrestrial organic matter comprises only 25-30% of zooplankton biomass. The relatively high reliance on algal material demonstrates that zooplankton are quite selective in keeping with physiological studies (51,52) and some field studies (22,23).…”

Dietary Segregation of Pelagic and Littoral Fish Assemblages in a Highly Modified Tidal Freshwater Estuary

“…A variety of organic carbon sources may support coastal and estuarine consumers, including phytoplankton (Canuel et al 1995;Deegan and Garritt 1997;Sobczak et al 2002;Howe and Simenstad 2007), submerged aquatic vegetation (SAV;Fry 1981;Kitting et al 1984), benthic algae (Hecky and Hesslein 1995;Deegan and Garritt 1997;Kwak and Zedler 1997;Page 1997), epiphytic macroalgae (Kitting et al 1984;Moncrieff and Sullivan 2001;Vizzini et al 2002), and terrestrial vegetation (Chanton and Lewis 2002).…”

“…These studies have demonstrated the importance of in situ phytoplankton production as the primary source of available organic carbon for pelagic consumers in the tidal freshwater region of the estuary (Canuel et al 1995;Jassby and Cloern 2000;Mueller-Solger et al 2002;Sobczak et al 2002Sobczak et al , 2005. However, the relative importance of phytoplankton as an energy source for consumers in other habitats is unclear.…”

“…In addition, long-term declines in phytoplankton production may be increasing the relative importance of other energy sources . The answers to these questions remain outstanding because long-term monitoring and special studies have focused on pelagic habitats (Orsi and Mecum 1996;Kimmerer 2002aKimmerer , 2006Mueller-Solger et al 2002;Sobczak et al 2002).…”