A time series assessment of planktonic archaeal variability in the Santa Barbara Channel

Abstract

Although detailed temporal studies of marine planktonic cyanobacteria have been reported, relatively little is known about variation of other marine picoplankton groups on time scales on the order of months to years. In this study, we followed vanation in relative abundance of planktonic archaeal rRNA at 5 depths in the upper 300 m of the Santa Barbara Channel (SBC) over 32 mo. Small subunit rRNA targeted oligonucleotide probes were used to quantify archaeal, bacterial, and eucaryal rRNA relative abundance. Archaea subgroups were quantified using probes specific to 2 planktonic archaeal groups, termed G1 and G11 The archaeal rRNA signal in the upper 20 m was characterized by intermittent 'blooms' that coincided with increases in the relatlvc ab.undance of GII rRNA as well as decreases in chlorophyll a (chl a). At greater depths, archaeal rRNA abundance was consistently elevated, approaching bacterial rRNA abundance. The G1 rRNA accounted for the majority of the deeper archaeal rRNA signal throughout the time series. Consistent with a previous report, the 2 groups of archaea had maximal rRNA abundance at different depths. The lnajolity of the variability in the G1 archaeal slgnal in the upper 75 m (77 %) could be attributed to a positive relat~onship with nutrients and negative relationships with prokaryotic abundance, chl a, and temperature; although, at most, 41% of the variability at each depth could be explained. Only 21 % of the variability in the G11 rRNA signal could be explained by the variables included in the model. Leucine incorporation rates and, to a lesser extent, prokaryote abundance, were highly correlated with chl a and POC levels. Only weak relationships were observed between prokaryote abundance or leucine incorporation and incredses in temperature. The results of linear regressions between prokaryote abundance and leucine incorporation suggest that top-down ecological controls may regulate prokaryotic assemblages in this dynamic coastal system. The distribution of the 2 archaeal groups suggested that they responded independently to environmental conditions, are physiologically different, and likely participate in different environmental processes.

Molecular and biogeochemical evidence for ammonia oxidation by marine Crenarchaeota in the Gulf of California

“…For example, the profiles observed here follow the expected progression from ammonification to ammonia oxidation to nitrite oxidation with increasing depth in the water column (Codispoti and Christensen, 1985;Ward, 2000)-as evidenced by peak NH 4 þ concentrations at 35-40 m, peak NO 2 À concentrations at 40-50 m, maximum ammonia oxidation rates and archaeal amoA gene copies at 50-60 m and an eventual increase in NO 3 À concentrations at 50 m and below ( Figure 5). Because NO 2 À and NH 4 þ are produced and consumed by multiple processes, including ammonia oxidation, concentrations of NO 2 À and NH 4 þ are not necessarily expected to correlate with amoA gene copies throughout the water columnhowever, in some cases they might be related over certain depth ranges, or, more likely, through time (for example, Murray et al, 1999;Wuchter et al, 2006). These data may instead capture coincident variation in biogeochemical properties and microbial abundances along the transition from surface layers to the deep ocean; however, this seems like an oversimplification given variation over several orders of magnitude for both amoA copies and 15 NH 4 þ oxidation rates, as well as distinct biogeochemical differences between basins.…”

The origin of transparent exopolymer particles (TEP) and their role in the sedimentation of particulate matter

“…Concentrations of bacteria integrated over the upper 75 m, varied between 16 and 120Â10 12 cells m À2 and showed no regular seasonal pattern (Murray et al, 1999). None of the peaks in TEP concentration were associated with elevated bacteria concentrations, except during some phytoplankton blooms, where both bacteria and Chl.…”

Application of the TEX86 temperature proxy to the southern North Sea

“…This is consistent with our data, since higher concentrations of the GDGTs used for calculating the TEX 86 were found in February (Table 1). This seasonal occurrence of Crenarchaeota may be related to the strong negative correlation between crenarchaeotal abundance and chlorophyll a reported for surface seawater in other areas (Murray et al, 1998(Murray et al, , 1999. Indeed, the southern North Table 2 Concentrations of GDGTs used for calculating TEX Apr.…”