Abundance and Community Structure of Picoplankton and Protists in the Microbial Food Web of Barguzin Bay, Lake Baikal

Abstract

We examined the vertical abundance of bacteria, phytoplankton and protists along a transect of six stations from near-shore (Stn. 1) to off-shore (Stn. 6) in Barguzin Bay of Lake Baikal, in the summer of 2002. Chlorophyll concentrations at Stn. 1 were higher (>10 lg l À1 ) than at the other five stations (<3 lg l À1 ). Planktonic and sessile diatoms dominated at Stn. 1, while pico-phytoplankon was dominant at other stations. Densities of heterotrophic bacteria were high in both the epilimnion and the thermocline at all stations. Nanoflagellates were abundant in the epilimnion, and ciliates in the thermocline, but no horizontal trend could be found for these heterotrophs. At Stn. 1, not only filter feeding (Strombidium and Strobilidium) and raptorial (Balanion) ciliates but also predatory ciliates (Prorodon and Spathidiosus) dominated, while at other stations only the filter feeding and raptorial ciliates were dominant. In off-shore stations (Stns. 5 and 6), significant correlations were detected between concentrations of chlorophyll a and density of filter feeding or raptorial ciliates, suggesting tight food linkages between phytoplankton and these ciliates. The concentration of dissolved organic carbon (DOC) was significantly correlated with chlorophyll a concentration, although there was no significant correlation between DOC concentration and bacterial density. We suggest that there is a shift of the dominant food linkage from a herbivorous food chain in near-shore areas to a microbial food web in off-shore areas in Barguzin Bay of Lake Baikal.

Abundance and pigment type composition of picocyanobacteria in Barguzin Bay, Lake Baikal

“…In the area near the shore of Barguzin Bay, there is no available data on the spectral range of solar radiation. However, in this area, high chlorophyll a concentrations were detected in our previous studies (Ueno et al 2005;Katano et al 2005b;Satoh et al 2006); thus, the wavelength of maximal light penetration may shift from the blue-green towards the red portions of the spectrum, as in other eutrophic lakes.…”

Abundance, growth and grazing loss rates of picophytoplankton in Barguzin Bay, Lake Baikal

“…1. Ueno et al (2005) enumerated the heterotrophic nanoflagellates (HNF) and ciliates and found that the abundance of HNF was similar between the stations (5.4-10.4·10 3 cells ml )1 ). The cell densities of ciliates at Stations 1 and 4 were 345-649 and 89-245 cells l )1 , respectively, with suspension feeders such as Strombidium and Strobilidium being numerically dominant at both stations.…”

A comparison of phytoplankton size-fractions in Mondsee, an alpine lake in Austria: distribution, pigment composition and primary production rates

“…Several studies have documented the substantial contribution of APP to total production and Chl a. Furthermore, these studies reported that the picophytoplankton was favoured in lakes with low phosphorus concentrations even if this tendency could be partially superimposed by other influences as grazing and light availability (Padisák et al 1997;Stockner et al 2000;Callieri and Stockner 2000;Drakare et al 2003;Ueno et al 2005).…”