This image shows marine viruses. The small dots are viruses and the large blobs are bacteria, their hosts. Credit: Rachel Parsons
fill the ocean and have a significant effect on ocean biology,
specifically marine microbiology, according to a professor of biology at
UC Santa Barbara and his collaborators.
A. Carlson, professor with UCSB’s Department of Ecology, Evolution, and
Marine Biology, is the senior author of a study of marine viruses
published this week by the International Society for Microbial Ecology Journal, of the Nature Publishing Group.
new findings, resulting from a decade of research, reveal striking
recurring patterns of marine virioplankton dynamics in the open sea,
which have implications regarding our understanding of cycling of
nutrients in the world’s oceans.
viruses encompass enormous genetic diversity, affect biogeochemical
cycling of elements, and partially control aspects of microbial
production and diversity, according to the scientists. Despite their
importance in the ocean, there has been a surprising lack of data
describing virioplankton distributions over time and depth in open
interactions, between oceanic viruses and bacteria, take place on the
nanometer scale but are extremely important in governing the flow of
energy and the cycling of nutrients like carbon, nitrogen, and
phosphorus on the ecosystem scale of the world’s oceans,” said Carlson.
The scientists studied microbes in the water column of the Saragasso
Sea, off of Bermuda, for a decade.
we can’t see them with our naked eye, marine microbes are the dominant
life forms in our oceans,” said Rachel J. Parsons, first author and a
microbial oceanographer with the Bermuda Institute of Ocean Science.
“They comprise 95% of the living biomass in the oceans––more than all
the krill, fish and whales put together. They grow at rates many times
faster than larger animals. As a result of their sheer numbers, and the
rates at which they grow, they are responsible for transforming and
shaping the distribution of life’s essential elements––and they help
control climate on our planet. Without marine microbes, life as we know
it could not persist.”
to the scientists, there are approximately 10 million viruses in every
drop of surface seawater, yet despite the high number of viruses very
few are infectious agents to larger animals like fish, whales, or
humans. That is because almost all of the marine viruses are
“phages”––viruses that specifically attack marine bacteria. Marine
phages cannot carry out cellular metabolism and must therefore rely on
the metabolic machinery of their bacterioplankton hosts to replicate.
This warfare often kills the hosts, causing them to spill their internal
nutrient content into the surrounding water.
the new paper, the authors describe remarkably regular annual patterns
of virioplankton abundance, tied to ocean physics and chemistry. These
patterns in turn control the dynamics of the bacterioplankton hosts. The
data suggest that a significant fraction of viruses in the upper
photic, or light, zone of the subtropical oceanic gyres may be
cyanophages––viruses that infect photosynthetic bacterioplankton.
This image shows the deployment of a sensor for conductivity, temperature and depth-profiling rosette (CTD). The equipment was used to sample the water throughout the water column, including viruses. Credit: Craig Carlson
true, the dominance of cyanophages in open ocean systems has
significant biogeochemical implications. Viral-mediated breakdown of
cyanobacteria could benefit phytoplankton through the release of macro-
and micronutrients. Viral breakdown of host cells converts particulate
material to suspended or dissolved materials such as amino acids and
nucleic acids, effectively resulting in the retention of nitrogen,
phosphorous, and iron within the surface water. These dissolved
materials fuel microbial activity in an otherwise nutrient-poor open
this decade-long study, the scientists studied in unprecedented detail
the temporal and vertical patterns of virioplankton abundance within the
open ocean. Samples were collected throughout the upper 300 meters of
the water column every month, beginning in the year 2000, at an open
ocean hydrostation called the Bermuda Atlantic Time-series Study (BATS)
site. The additional data collected as part of the BATS program provides
oceanographic details regarding ocean physics, chemistry, and biology
that are extremely valuable for interpreting the observed trends in
high-resolution, decadal survey provides insight into the possible
controls of virioplankton dynamics and the role they play in regulating
biology and nutrient cycling in the open ocean,” said Carlson. “The data
provided by this study will now be utilized by ecosystem and
biogeochemical modelers in an attempt to better understand how microbial
processes affect the larger biogeochemical cycling in the ocean.”
co-authors of the study are Mya Breitbart, of the University of South
Florida, and Michael W. Lomas, of the Bermuda Institute of Ocean