Dominance of particle-attached bacteria in the Columbia River estuary, USA

Abstract

Particle-attached bacteria are a central component of the detrital food web of many turbid coastal and estuarine ecosystems. The Columbia River estuary, at the terminus of a 660000 km2 watershed in northwestern North America, is a turbid, partially mixed system that has a flushing time of 1 to 3 d. Several large, well-defined estuarine turbidity maxima (ETM) extend the residence time of both mineral and organic particles transported through the estuary. Water samples collected in the North Channel of the estuary every 2 h for 148 h (6 tidal cycles) in May 1995 were analyzed to determine the concentration and production of particle-attached and free-living bacteria, extracellular enzyme activity, turbidity, salinity, and particulate organic carbon (POC) concentration. The concentration of particle-attached bacteria. defined as those caught by a 3 pm filter. averaged 1.02 X 106 (SD = 1.00 X 106) cells ml-' and correlated with turbidity and POC, and thus to some extent with the tidal cycle that maintains the ETM. The concentration of free-living bacteria was more constant, averaging 1.25 X 106 (SD = 0.4 X 10" cells ml-' Particle-attached bacterial carbon production, ca.lculated from the rate of incorporation of 3H-thymidine, averaged 1.61 (SD = 1.10) pg 1-' h-', accounted for 90% (SD = 9%) of total bacterial carbon production, and correlated with turbidity and POC. Extracellular enzyme activity, measured as the rate of hydrolysis of fluorescently labeled compounds, increased with turbidity and was predominantly associated with particles. Particle-attached bacteria probably account for most of the bacterial degradation of particulate organic material in the estuary, and the transfer of that material into the detrital food web. The hydrodynamics of the estuary contribute to the dominance of particleattached bacteria by extending the residence time of particles in the ETM, and by quickly flushing freeliving cells through the estuary, perhaps preventing the development of an estuarine population of free-living bacteria.

Bacterial production in subarctic peatland lakes enriched by thawing permafrost

“…Grossart and Simon (1993) found lake particle aggregates to be densely colonized by bacteria, with approximately 10 8 bacterial cells per mL, 100 times higher than concentrations in the bulk water. The presence of particleattached bacteria may also result in greater community diversity, as has been demonstrated in studies of estuarine mixing zones (Crump et al, 1998;Waidner and Kirchman, 2007). A study by Ploug and Grossart (2000) identified a positive correlation between bacterial production, particulate organic carbon and aggregate size.…”

Oxic/anoxic oscillations and organic carbon mineralization in an estuarine maximum turbidity zone (The Gironde, France)

“…This DOC supply can be attributed to both desorption processes (Keil et al 1994), because of surface competition and rapid pH change (Morel et al 1991), and to the death of aerobic bacteria. Indeed, particle-attached aerobic bacteria are dominant in estuarine MTZ (Zimmermann 1997;Crump et al 1998) and can be trapped in the anoxic fluid mud, where most of them die after a few days. As a consequence, the growth of anaerobic bacteria is stimulated and could further promote the degradation of refractory POM within the fluid mud.…”

“…This forms MTZs, where photosynthesis is strongly limited by light availability (Cole et al 1992;Fishez et al 1992;Irigoien and Castel 1997) and where allochthonous materials originating from soil erosion and river-borne phytoplankton detritus are predominant (Relexans et al 1988;Small et al 1990;Bianchi et al 1993). Heterotrophic activity, enhanced by high turbidity (Crump et al 1998), results in a net mineralization of a major part of the particulate organic carbon (POC) (Wollast 1983;Smith and Hollibaugh 1993;Keil et al 1996;Gattuso et al 1998), producing CO 2 that interacts with the carbonate system (Kempe and E. Lemaire (DGO) for analytical help. We thank N. Iversen (University of Aalborg, Denmark) for helpful discussion in the field and J. Middelburg (NIOO, The Netherlands) for comments on early versions of the manuscript.…”

A tank system for studying benthic aquatic organisms at predictable levels of turbidity and sedimentation: Case study examining coral growth

“…Fine SPM is the primary cause of reduced light penetration on inshore reefs (e.g., Te 1997), and, according to the results of this study, shading suppresses coral growth to a greater extent than particle loading per se. The large surface area of SPM for colonization by microorganisms (Almeida and Alcantara 1992; Crump et al 1998) may enable a sufficiently high food value that SPM feeding by some coral species can offset the effects of reduced photosynthesis and sediment stress in turbid conditions.…”