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

Abstract

The abundance, growth, and grazing loss rates of picophytoplankton were investigated in August 2002 in Barguzin Bay, Lake Baikal. Water samples for incubation were taken once at a near-shore station and twice at an offshore station. Contributions of picophytoplankton to total phytoplankton were high (56.9-83.9%) at the offshore station and low (5.8-6.8%) at the near-shore station. The picophytoplankton community in the offshore station comprised mainly phycoerythrin (PE)-rich cyanobacteria, with eukaryotic picophytoplankton being less abundant. In contrast, as well as PE-rich cyanobacteria and eukaryotic picophytoplankton, phycocyanin (PC)-rich cyanobacteria were found in the near-shore station. At the offshore station, growth and grazing loss rates on 25 August were 0.56 and 0.43 day )1 , respectively, and on 29 August, 0.69 and 0.83 day )1 , respectively. At the near-shore station, growth and grazing loss rates were 1.61 and 0.70 day )1 , respectively. These results show that there is a difference in the abundance, composition, and ecological role in the microbial food web of picophytoplankton between the near-shore and the offshore areas in Barguzin Bay.

Nutrient limitation of the primary production of phytoplankton in Lake Baikal

“…Picocyanobacteria are the predominant primary producers in pelagic Lake Baikal during summer (Nagata et al 1994;Goldman et al 1996;Belykh and Sorokovikova 2003;Katano et al 2005). A general explanation for the predominance of picocyanobacteria in oligotrophic lakes is that they have an advantage in the uptake of low concentration nutrients because of their high surface-to-volume ratio (Weisse 1993;Raven 1998).…”

“…The vernal maximum biomass of phytoplankton in a Melosira year is about tenfold greater than that in a non-Melosira year (Bondarenko and Evstafyev 2002). Another characteristic of Lake Baikal is the dominance of very small phytoplankton, called picoplankton (formerly called ultrananoplankton) in the biomass and primary productivity of the phytoplankton assemblage (Votintsev et al 1972;Back et al 1991;Nagata et al 1994;Bondarenko et al 1996;Watanabe and Drucker 1999;Belykh and Sorokovikova 2003;Yoshida et al 2003;Katano et al 2005).…”

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

“…The pigment type of most picocyanobacterial cells is of the PE-rich type in the pelagic zone of Lake Baikal (Belykh and Sorokovikova 2003). However, PC-rich type picocyanobacteria were found near the shore station in Barguzin Bay (Katano et al 2005b). The previous study indicates that the growth of picophytoplankton near the shore zone is significantly higher than in the pelagic zone (Katano et al 2005b).…”

“…However, PC-rich type picocyanobacteria were found near the shore station in Barguzin Bay (Katano et al 2005b). The previous study indicates that the growth of picophytoplankton near the shore zone is significantly higher than in the pelagic zone (Katano et al 2005b). Therefore, their ecological role in the planktonic food web may be different.…”

“…50-80%) to the total primary production in the southern basin (Nagata et al 1994;Yoshida et al 2003). Several studies on the abundance of picophytoplankton in Lake Baikal demonstrated that picocyanobacteria are also important components in terms of cell density among picophytoplankton (Boraas et al 1991;Nagata et al 1994;Watanabe and Drucker 1999;Belykh and Sorokovikova 2003;Nakano et al 2003;Katano et al 2005b;Belykh et al 2006). Picocyanobacteria are abundant throughout the entire lake during summer (Belykh and Sorokovikova 2003), with a maximum density of 2 9 10 6 cells ml -1 recorded in the southern basin (Nagata et al 1994).…”