Bacterioplankton communities of Crater Lake, OR: dynamic changes with euphotic zone food web structure and stable deep water populations

Abstract

The distribution of bacterial and archaeal species in Crater Lake plankton varies dramatically over depth and with time, as assessed by hybridization of group-specific oligonucleotides to RNA extracted from lakewater. Nonmetric, multidimensional scaling (MDS) analysis of relative bacterial phylotype densities revealed complex relationships among assemblages sampled from depth profiles in July, August and September of 1997 through 1999. CL500-11 green nonsulfur bacteria (Phylum Chloroflexi) and marine Group I crenarchaeota are consistently dominant groups in the oxygenated deep waters at 300 and 500 m. Other phylotypes found in the deep waters are similar to surface and middepth populations and vary with time. Euphotic zone assemblages are dominated either by bproteobacteria or CL120-10 verrucomicrobia, and ACK4 actinomycetes. MDS analyses of euphotic zone populations in relation to environmental variables and phytoplankton and zooplankton population structures reveal apparent links between Daphnia pulicaria zooplankton population densities and microbial community structure. These patterns may reflect food web interactions that link kokanee salmon population densities to community structure of the bacterioplankton, via fish predation on Daphnia with cascading consequences to Daphnia bacterivory and predation on bacterivorous protists. These results demonstrate a stable bottom-water microbial community. They also extend previous observations of food web-driven changes in euphotic zone bacterioplankton community structure to an oligotrophic setting.

Chloroflexi CL500-11 Populations That Predominate Deep-Lake Hypolimnion Bacterioplankton Rely on Nitrogen-Rich Dissolved Organic Matter Metabolism and C 1 Compound Oxidation

“…The peak relative abundance of CL500-11 in Lake Michigan was similar to that in Lake Biwa, where the same CARD-FISH probe used in the present study was used, while it remained well below the 50% reported in Crater Lake (15,16). Total bacterial and CL500-11 cell numbers were about 1 order of magnitude lower in Lake Michigan than in Lake Biwa, most likely reflecting the lower levels of DOC and nutrients in Lake Michigan, which is oligotrophic (Fig.…”

“…Chloroflexi are rarely observed in freshwater pelagic zones when oxygen is plentiful (8), but CL500-11-like populations are a notable exception and are emerging as a taxon restricted to lakes that are deep enough to maintain low temperatures (Ͻ10°C) in the hypolimnion after stratification (14). This group was first observed in Crater Lake, OR, where it is abundant throughout the year, contributing up to 50% of all cells in the deep (15,16). Since its initial discovery, a similar predominance has been observed in deep lakes around the world, including in Western Europe, East Asia, and, most recently, two of the largest freshwater lakes in the world, Lake Superior and Lake Huron (14,17).…”

Vertical Distribution of Ammonia-Oxidizing Crenarchaeota and Methanogens in the Epipelagic Waters of Lake Kivu (Rwanda-Democratic Republic of the Congo)

“…Although obtained by a different methodological approach, archaeal abundance in neighboring Lake Victoria reached 5.9% of the total nucleic acids (38). Similar values (between 1 and 7% of DAPI-stained cells) were obtained by FISH and CARD-FISH in different freshwater lakes (36,59), although recent studies carried out in high mountain lakes reported abundances of up to 22% in Crater Lake (87) and 37% in Lake Llebreta (4). In stratified marine environments such as the Cariaco Basin and the Black Sea, the archaeal planktonic fraction ranged from 1% to 9% and from 10% to 30% of total DAPI counts, respectively, showing maximal abundances at the redoxcline coinciding with depth maxima of nitrite and nitrate (15,41,44).…”

Microbial Ecology of Lake Kivu

“…The small contribution of archaea to the planktonic microbial community is a common trait for freshwater environments (Casamayor and Borrego 2009 ) . In this regard, values below 10% of total prokaryotes have usually been reported for different freshwater lakes (Pernthaler et al 1998 ;Jürgens et al 2000 ;Llirós et al 2011 ) , although higher archaeal abundances have been reported (>20% of total cells) in some oligotrophic (Urbach et al 2007 ;Auguet and Casamayor 2008 ) or oligomesotrophic (Callieri et al 2009 ) freshwater lakes.…”