Where did these atrocities take place?
Hydrothermal vents
typically arise near hotspots of tectonically active mid-ocean ridges. These
release super heated seawater, (as high as 400°c) into the surrounding ocean along with
chemicals from the lithos’ and asthenosphere. Little if any light penetrates
these depths, thus the primary production of the deep tends toward the
chemosynthetic. The ‘vent environment’ is not solely restricted to the area
immediately surrounding the vent; the hydrothermal ejaculate, once diluted by
about “10,000 fold” cools and reaches neutral buoyancy and is hence swept
laterally by currents in the surrounding seawater. In this way particulates and
chemicals may spread as far as “2000km” or more.
Studies have found
that abundances of chemosynthetic prokaryotes within vent fields to be higher
than those found in the surrounding seawater. Viral lysis is a likely source of
prokaryote mortality, and has been implicated as an affecter of carbon cycling
and prokaryote community structure around the vents. However there is little
knowledge on hydrothermal vent viral abundance and distribution. Compared to
surface waters, viral numbers are significantly diminished by about
“1000-fold”. An exemption of these maybe hydrothermal vents, where high
microbial biomass can potentially lead to high lytic production.
This study examined
the distribution and abundance of viruses around active vents, in an attempt to
ascertain if virus mediated mortality affects the microbial dynamics within the
system over a four-year period.
Samples were taken
from three active sites, within these were found both viruses and prokaryotes,
though viral abundance was generally higher. Results showed higher viral
abundances found at active hydrothermal vents than surrounding deep sea, this
is indicative that viral production was occurring and that it was a source of
microbial mortality.
However within
neutrally buoyant plumes, abundance of viruses and prokaryotes was lower than
that of samples from active fields but were higher than non-plume samples.
Though this decrease was exacerbated for viruses compared to prokaryotes.
Additionally it was found that prokaryotic and viral abundances in non-hydrothermal
regions were as much as 10-fold higher than in previous studies. The difference
may be because this study employed the use of epifluorescent microscopy which
was previously not available.
The authors suggest
that viral infection may be a greater source of prokaryotic mortality than
previously recognised. The results indicate that mortality of prokaryotes
mediated by viruses in hydrothermal environments may be significant enough to
reduce energy flow to higher trophic levels.
This study bares
significance as it presents the first data on viral abundance and distribution
from black smokers, additionally providing further data on the abundance of
viruses and prokaryotes in hydrothermal-vent plumes, which so far has been limited.
Alice C. Ortmann, Curtis A. Suttle, High abundances of
viruses in a deep-sea hydrothermal vent system indicates viral mediated
microbial mortality, Deep Sea Research Part I: Oceanographic Research Papers,
Volume 52, Issue 8, August 2005, Pages 1515-1527
Available at: http://www.sciencedirect.com/science/article/pii/S0967063705001032
hey sean, just a quick question, was the identification of the viruses and prokaryotics more specific, like was there a greater abundance of a specific well known one, or did they just keep it vague-ish and just say virus and prokaryotes and not go into the identification
ReplyDeletethanks, Ollie.
Hi Ollie,
ReplyDeleteReally good point, just skimmed the paper again – and they keep the community compositions vague – and isn’t mentioned in any detail. Though it would be really interesting to know, and could add a whole additional dimension to the study.
Thanks for the comment and sorry for the slow reply
Sean