Microbial diversity in a Pacific Ocean transect from the Arctic to Antarctic circles

Abstract

Microbial diversity in surface waters was examined along a ~15 400 km transect of the Pacific Ocean from 70°N to 68°S latitude between late August and early November 2003. Comparative microbial diversity was determined using terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR amplified 16S and 18S rDNA restriction digested with CfoI and MspI. Bacterial numbers and total chlorophyll were greatest at higher latitudes in both hemispheres, with a smaller peak in equatorial waters. Flow cytometry analysis indicated a strong peak in Prochlorococcus from approximately 30°N to 30°S. Richness at each station was relatively low, with 11 prokaryotic peaks per sample and ~12 eukaryotic peaks per community. Overall, prokaryotic populations appeared more diverse, with 181 total terminal restriction fragments (T-RFs) generated, while eukaryotic populations produced a total of 135 T-RFs. Prokaryotic and eukaryotic similarity dendrograms revealed 4 distinct cluster groups relating to regions sub-Arctic/Arctic, temperate, tropical and sub-Antarctic/Antarctic. T-RFLP patterns suggest that microbial communities may be influenced by ambient water temperature, with mid-latitudinal and equatorial communities more similar in composition to each other than to cold water communities. Global distribution of prokaryotic communities revealed an average inter-group similarity of ~52%, while eukaryotic communities showed ~51% similarity, implying that Pacific planktonic communities appear to be fairly homogenous in composition. Several T-RFs were ubiquitously distributed and contributed significantly to each cluster group, while several T-RFs were observed to be endemic to particular oceanic regions. Within-group similarities of > 70% were attributed to 12-14 T-RFs and 8-11 T-RFs in prokaryotic and eukaryotic profiles, respectively, suggesting that a small number of phylogenetic groups were responsible for each cluster group.

Pole-to-pole biogeography of surface and deep marine bacterial communities

“…Moreover, polar ocean circulation patterns and cold seawater temperatures have been present for up to 25 million years (3). Few studies have compared bacterioplankton communities at the poles; one transect along the axis in the Pacific Ocean from the Arctic to the Southern Ocean used a DNA fingerprinting technique, which indicated differences between the two poles, as well as mid latitudes (12). That study detected, but did not identify, ∼11 taxa per sample and covered only a small area of each polar zone.…”

“…Community-wide comparisons using small subunit (SSU) rRNA gene surveys of planktonic Archaea reported sequences that are 99% identical from the two poles (11). However, a latitudinal transect of the Pacific Ocean using a community fingerprinting method indicated differences in the bacterial and eukaryal communities from the two poles as well as from tropical and temperate regions (12). Likewise, sea ice microbial communities at the two poles harbor closely related organisms although differ significantly in the representation of some groups (9,13).…”

A biophysical perspective on dispersal and the geography of evolution in marine and terrestrial systems

“…Darling et al 2000;Esteban et al 2007; see also Brown & Hovmøller 2002). Most studies to date suggest that neither marine nor soil bacteria show the latitudinal diversity gradient (Baldwin et al 2005;Fierer & Jackson 2006), but there are recent exceptions (Pommier et al 2007) which may be common among larger microbes (e.g. tintinnids; Dolan et al 2006;see Finlay 2002); indeed, organisms with large, but subhemispheric, ranges are expected to show strong broad peaks in latitudinal diversity under the mid-domain model, with patterns of local species richness being modified by small-scale environmental heterogeneity (Colwell et al 2004(Colwell et al , 2005. )…”

“…The initial picture is that marine bacterioplankton are very widely dispersed but not ubiquitous. Ribotypes often have global distributions that segregate along broad climatic bands (Baldwin et al 2005;Pommier et al 2005;Follows et al 2007) or ecologically relevant depth strata (DeLong et al 2006). Cosmopolitanism appears as an occasional trait (Pommier et al 2005), presumably in species with very wide ecological tolerances.…”

Protist community composition in the Pacific sector of the Southern Ocean during austral summer 2010

“…There are several studies from the Arctic Ocean (Hamilton et al 2008;Galand et al 2009;Lovejoy and Potvin 2011) and the Southern Ocean (Diez et al 2004;Baldwin et al 2005), addressing the question how hydrography is shaping microbial eukaryotic distribution. Diez et al (2004), e.g., showed in the Atlantic sector of the Southern Ocean that picoeukaryotic assemblages were characteristic of each water mass.…”