Attached and Free-Floating Bacteria in the Fraser River Estuary, British Columbia, Canada

Abstract

The contribution of free-floating bacteria versus bacteria attached to particulate material to the microbiology of the Fraser River Estuary was assessed. Approximately 60 % of bacterial biomass and heterotrophic activity was associated with suspended particulates in the turbid Fraser River (0 Y&o S). The influence of attached bacteria decreased down the estuary as salinity increased dropping to 15-39 % of total bacterial numbers and 4 % of heterotrophic activity in the Strait of Georgia (26 Ym S). Bacteria, both attached and free-floating, were the predominant part of the microbial population in the river in terms of biomass and productivity. In the Strait of Georgia, however, bacteria constituted only 4 % of the microbial biomass and 25 % of microbial productivity. Heterotrophic activity and productivity were stimulated in the plume (15 % S) to levels higher than those found in either the strait or the river. The percentage glucose respired was always found to be lowest in the river. INTRODUCTIONnoted the importance of detritus with its attached microflora to the dynamics of several estuaries. The relative abundance of free-floating bacteria and Accordingly, we report herein upon biomasses, those attached to suspended matter in aquatic environheterotrophic activities and productivities of free-floatments is controversial. In the open ocean most invesing and attached bacteria within the estuary of the tigators have found that the majority of the planktonic Fraser River through its plume into the saline waters of bacteria are unattached and free-floating (Wiebe and the Strait of Georgia. Pomeroy, 1972;Sieburth et al., 1974;Ferguson and Rublee, 1976; Azam and Hodson, 1977).However, data from various freshwater environments vary. Rieman (1978) observed 50-93 % of glu-MATERIALS AND METHODS cose uptake activity passed through a 1.0 pm Nuclepore filter; however, these percentage values varied Samples were collected from the Fraser River Estuwith the seasons. Burnison (1975) found 82 % of the ary on 6 cruises over a period of 13 months (Table 1). bacterial biomass passed through a 1.0 pm Nuclepore Three stations only were examined during the first 5 filter in samples from the Bay of Quinte. Berman and cruises. The 'river' station was situated approximately Stiller (1977) noted 90 % of carbon uptake in the fil-40 km upstream from the river mouth and the salinity trate from a 3.0 km Nuclepore filtration of Lake Kinwas always 0 % S (Station 10, Fig. 1). Surface water neret water.(1 m) at 15 Om S was chosen as the 'plume' station. This Within estuaries the situation may be even more location varied between Stations 1 and 4 (Fig. l ) complex because of the changing physicochemical and depending on the tide and discharge volume of the biological reactions which occur as the fresh river river. The 'strait' station constituted the third and last water meets the sea water. Unfortunately literature on location lying in the Strait of Georgia midway between bacterial attachment to solid surfaces in estuaries is Vancouv...

Planktonic bacteria in estuaries and coastal waters of northern Massachusetts: spatial and temporal distribution

“…This estuary is similar to the Parker River system, and it seems likely that the factors discussed above are also responsible for the distribution of bacteria found by Peterson. Other published works involving the distribution of bacteria in estuaries (Bell and Albright, 1981;Bent and Goulder, 1981) deal with such fundamentally different systems that a comparison of results is not possible. Palumbo and Ferguson (1978) suggested that the bacteria were behaving as conservative constituents in the Newport River estuary, to explain the upper estuary peak and an inverse relation between bacteria numbers and salinity proceeding out into coastal water.…”

“…This pattern is a consequence of the fact that most of the bacteria were attached to suspended solids. The Fraser River estuary in British Columbia is also characterized by high turbidity and a large proportion of particulate bacteria (Bell and Albright, 1981). Total counts showed an inverse trend with salinity, although heterotrophic activity of the bacteria was generally highest in the plume water of intermediate salinity.…”

Microbial ecology of organic aggregates in aquatic ecosystems

“…, Grossart & Simon 1998b, Turley & Stutt 2000. In riverine and estuarine systems, however, they may constitute as much as 90% of total bacterial numbers and production (Bell & Albright 1981, Bent & Goulder 1981, Zimmermann & Kausch 1996, Zimmermann 1997, Crump & Baross 2000. In most environments, even with high amounts of suspended matter, the relative proportion of particleassociated bacteria is lower than that of free-living bacteria (Kirchman 1993, Berger et al 1996, Crump & Baross 1996, Crump et al 1998).…”

Fate of particle-bound bacteria ingested by Calanus pacificus

“…Attached bacteria may thus be a substantial food source which, if passed on directly to metazoans, could link the microbial loop (Azam et al 1983) with the grazing food chain. This direct pathway would likely be more important in waters with high particle load such as estuaries and coastal waters, and during post-algal bloom periods where the quantitative significance of production of attached bacteria can be quite high (Bell & Albright 1981). Attached bacteria may also provide a mechanism of energy flow in oligotrophic waters where the primary production is often dominated by picoplankton too small to be efficiently ingested by metazoa and where bacterial carbon can exceed phytoplankton carbon (Fuhrman et al 1989, Cho & Azam 1990).…”