Environmental Engineering Reference
In-Depth Information
COMPOSITION AND ACTIVITIES OF MICROBIAL
COMMUNITIES INVOLVED IN CARBON, SULFUR,
NITROGEN AND MANGANESE CYCLING IN THE
OXIC/ANOXIC INTERFACE OF THE BLACK SEA
Nikolay V. Pimenov
1
and Lev N. Neretin
2,3
1
Winogradsky Institute of Microbiology of Russian Academy of Sciences, 60-letiya Oktyabrya
Prosp., 7-2, 117811 Moscow, Russia
2
Max Planck Institute for Marine Microbiology, Biogeochemistry Department, Celsiusstrasse
1, 28359 Bremen, Germany
3
Federal Institute for Geosciences and Natural Resources, Section Geomicrobiology, Stilleweg
2, 30655 Hannover, Germany
Abstract
Own and literature data on the structure and functional activities of microbial
communities in the Black Sea chemocline are reviewed. Bacterial numbers in the
oxic/anoxic interface increase by an order of magnitude compared to above-lying
waters. The dark carbon dioxide fixation rate increases too and often does not
correspond to the maximum in total cell numbers. Carbon isotope measurements
of particulate organic carbon indicate that bacterial chemosynthesis (rates are
between 9.6 and 25 mmol C m
−
2
d
−
1
) is the main source of organic matter in the
Black Sea chemocline and accounts for 20-50% of total primary production. The
increased dark CO
2
fixation rates in the chemocline reflect a mixed signal derived
from CO
2
fixation of a number of lithoautotrophic bacteria involved in sulfide
oxidation, but also with methanotrophs, methanogens and with sulfate reduc-
ers. Chemolithoautotrophic bacteria related to
Thiobacillus
and
Thiomicrospira
and heterotrophic sulfur oxidizing
Rhizobiaceae
strains are probably the main
sulfide oxidizing bacteria.
Shewanella
species using Mn (Fe) oxyhydroxides as
an alternative electron acceptor to dissolved oxygen may play a role in sulfide
oxidation too. Anoxygenic photosynthesis mediated by green sulfur bacteria re-
lated to
Chlorobium
accounts for not more than 13% of the total sulfide flux
[Overmann and Manske, this volume]. 'Anammox' bacteria together with deni-
trifiers may be mainly responsible for the inorganic nitrogen loss in the interface.
Below the interface, sulfate reduction, methane oxidation and methanogenesis
co-occur. Highest sulfate reduction rates are observed below the interface down
to 300 m; however this process is detected throughout the entire water column.
Several lines of evidence (isolates, rate measurements, molecular fingerprinting
and biomarkers) suggest that both, aerobic and anaerobic methane oxidation oc-
cur at the Black Sea oxic/anoxic interface and in anoxic waters. ANME-1 and
501
