Multiscale variability in bacterioplankton abundance, production, and specific growth rate in a temperate salt‐marsh tidal creek

Abstract

Heterotrophic bacterioplankton abundance, production, and specific growth rate in a salt-marsh tidal creek were measured weekly from April 199 1 to September 1992. During the same period, tidal and diel sampling studies were performed in May, June, and October 199 1 and May and August 1992. Seasonal variability of bacterial abundance, production, and specific growth rate was regulated by temperature during nonsummer seasons when temperature was <2O"C. During summer, bacterial variables were not limited by temperature. Daily variability of bacterial abundance, production, and specific growth rate was regulated interactively by tidal mixing, substrate supply, and temperature over several tidal cycles. Higher bacterial abundance, production, and specific growth rate observed at low tide indicated that bacterial growth rate in the tidal creek was higher than in the adjacent river waters. This pattern might be due to larger nutrient fluxes originating in the tidal creek. Occasionally, the tidal effect was overridden by temperature during study periods when temperature changed dramatically over several tidal cycles. Bacterial diel patterns in production and specific growth rate in the tidal creek occurred only when day-night temperature differences exceeded lO"C, with maximal values during daytime. Short-term temperature manipulation experiments suggested that diel patterns in bacterial production and specific growth rate were probably caused by temperature, not light intensity. Thus, temperature regulated both seasonal and diel variations in bacterial production.

A time series assessment of planktonic archaeal variability in the Santa Barbara Channel

“…Similar relations have been described for estuarine (Hoch & Kirchman 1993) and lake systems (Sommaruga & Conde 1997). Also, unlike estuarine ecosystems which have been studied in recent years, where temperature was clearly the controlling environmental factor (Shiah & Ducklow 1995, Goosen et al 1997, prokaryote abundance in the SBC seemed to be independent of temperature control (though a peak in September did correlate with surface warming). Even though there was an 8°C spread in temperature at both the surface and 20 m through the annual cycle (12 to 20 or 10 to 18"C, respectively), these temperatures may exceed the range for which this relationship holds (<12"C, Hoch & Kirchman 1993).…”

“…It is quite possible that there are independent controls affecting different groups of planktonic prokaryotes (Hollibaugh 1994). The factors influencing the SBC bacterioplankton assemblage are probably therefore the result of a combination of controls such as diurnal mixing (Shiah & Ducklow 1995), substrate quality and quantity (ChinLeo & Benner 1991), temperature (e.g. Shiah & Ducklow 1995, Goosen et al 1997), and top-down influences such as bacterivory (e.g.…”

“…The relationship between abundance versus activity has been used to infer relative importance of bottomup (nutrient limitation) and top-down (removal) processes (Billen et al 1990), where slopes >0.7 are indicative of strong bottom-up control (Shiah & Ducklow 1995) and slopes of 0.4 to 0.55 suggest moderate control by bottom-up processes (Dufour & Torreton 1996). Linear regression between log prokaryote abundance and log leucine incorporation rate (Fig.…”

Bacterioplankton dynamics in the York River estuary: primary influence of temperature and freshwater inputs

“…There have been several studies of bacterial dynamics in the major tributaries of the Chesapeake Bay (Rublee et al 1984, Gilmour et al 1987, Shiah & Ducklow 1995. In the York and James Rivers, Ducklow (1982), Eldridge & Sieracki (1993), and Koepfler et al (1993) all studied short-term, event-scale processes including the effect of the spring-neap tidal cycle on bacterial abundance and activity at the mouth.…”

Annual average abundance of heterotrophic bacteria and Synechococcus in surface ocean waters

“…Most notably, these are oceanic locations such as the Labrador Sea (Li unpubl. ), the Equatorial Pacific (Ducklow et al 1995;Kirchman et al 1995;Landry et al 1996), the Arabian Sea (http://usjgofs.whoi.edufjg/dir/ jgofs/arabian& and the noahwest Indian Ocean Wiebinga et al 1997). Annual averages for such areas were based on data much less highly resolved over a complete cycle.…”