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...