Changes in production and respiration during a spring phytoplankton bloom in San Francisco Bay, California, USA:implications for net ecosystem metabolism

Abstract

We present results of an intensive sampling program designed to measure weekly changes in ecosystem respiration (oxygen consumption in the water column and sediments) around the 1996 spring bloom in South San Francisco Bay, California, USA. Measurements were made at a shallow site (2 m, where mean photic depth was 60% of the water colunln height) and a deep site (15 m, mean photic depth was only 20% of the water column). We also estimated phytoplankton primary producbon weekly at both sites to develop estimates of net oxygen flux as the sum of pelagic production (PP), pelagic respiration (PR) and benthic respiration (BR). Over the 14 wk period from February 5 to May 14, PP ranged from 2 to 210, PR from 9 to 289, and BR from 0.1 to 48 rnrnol O2 m-' d-l, illustrating large variability of estuarine oxygen fluxes at the weekly time scale. Pelagic production exceeded total respiration at the shallow site, but not at the deep site, demonstrating that the shallow domains are net autotrophic but the deep domains are net heterotrophic, even during the period of the spring bloom. If we take into account the potential primary production by benthic microalgae, the estuary as a whole is net autotrophic during spring, net heterotrophic during the nonbloom seasons, and has a balanced net metabolism over a full annual period. The seasonal shift from net autotrophy to heterotrophy during the transition from spring to summer was accompanied by a large shift from dominance by pelagic respiration to dominance by benthic respiration. This suggests that changes in net ecosystem metabolism can reflect changes in the pathways of energy flow in shallow coastal ecosystems.

Benthic fluxes, net ecosystem metabolism and seafood harvest: Completing the organic carbon balance in the Ría de Vigo (NW Spain)

“…The term net community production (NCP) is often used when just the microbial pelagic community metabolism is being measured (Staehr et al, 2012). The balance between net autotrophy and heterotrophy will depend on the nature of exogenous inputs (Caffrey et al, 1998) and so, coastal systems receiving high inorganic nutrient inputs tend to be net autotrophic (P>R) while those ones with high organic inputs tend to be net heterotrophic (R>P).…”

Exploring estuarine eutrophication sensitivity to nutrient loading

“…Respiration rates (g m 23 d 21 ) for Pensacola Bay (0.32) and Patuxent River Estuary (0.25-0.50; Murrell et al 2009) overlapped or spanned the modeled 95% CI (0.23-0.32). In addition, measured rates for Chesapeake Bay (0.5-0.7; Kemp et al 1997;Scavia et al 2006) span modeled rates (0.21-0.63) for its tributary estuaries, and rates for South San Francisco Bay (0.00-0.9; Caffrey et al 1998) span modeled rates for Central San Francisco Bay (0.14-0.21). Higher respiration rates have also been observed in Mobile Bay (0-3.7; Park et al 2007), Hopkins River Estuary (mean 6.5; Sharples et al 2003), and the Swan River Estuary (mean 2.9; Atkinson et al 1987).…”

Water, salt, and nutrient exchanges in San Francisco Bay

“…It is unreasonable to expect that none of the primary production is respired. Although uptake by benthic microalgae, which was not included in the budget of Cloern et al (1985), may be significant (Caffrey et al 1998), we suspect that much of the DIP uptake in this system is abiotic. Owing to the high turbidity of North San Francisco Bay in particular, this uptake is probably the result of P sorption onto particles (Froelich 1988).…”

“…gov/access/wqdata/. These data are also contained in the following technical reports: Wienke et al (1990), Wienke et al (1991Wienke et al ( , 1992; Wienke et al (1993);Caffrey et al (1994); Edmunds et al (1995);and Edmunds et al (1997). We obtained additional data for North San Francisco Bay and the Sacramento and San Joaquin Rivers from the State of California, Department of Water Resources.…”