The benthos ecosystems of the Crimea shelf: Hypoxia expansion and biodiversity
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....HYPOX kickoff: Site introduction
The benthos ecosystems of the Crimea
shelf: Hypoxia expansion and biodiversity
N. G. Sergeeva1, V.E. Zaika1, S.K. Konovalov2,
S.A. Mazlumyan1
1Institute
of Biology of the Southern Seas NASU,
Sevastopol, 2, Nakhimov ave., Ukraine
2Marine Hydrophysical Institute, NASU,
Sevastopol, 2, Kapitanskaya str., Ukraine
....HYPOX kickoff: Site introduction
Field site
Crimea
The Black Sea is the world's largest meromictic marine
basin having an anoxic water column below a permanent
halocline.
Today it is at a depth of 90 to 170 m.
2
....HYPOX kickoff: Site introduction
Long-term changes of the oxygen in the
Black Sea (1955-1982; 1983-2003)
Temporal and spatial changes in the
oxygen distribution at the depth of
100m were studied. The average
oxygen concentration for the
different periods varied.
Oxygen decrease is
typical for the central part
of the sea and an
increase in the oxygen is
typically traced at the
deep basin periphery.
The essential decrease
of oxygen concentration
at the depth of 100m in
comparison with early
period is shown.
3
....HYPOX kickoff: Site introduction
Long-term changes of the oxygen &
sulfide in the Black Sea 1960-2005 (100m)
Long-term increasing of the
sub-oxygen zone in the
1980’s was primarily due to
decline of the oxygen
concentration in the aerobic
zone.
The zones of hypoxia were
observed on the different
parts of the Black Sea. The
origin of hypoxia is inherent
to the Black Sea deep-water
biotopes and in another
anthropogenic cases.
Hydrogen sulfide (both
natural and anthropogenic
origin) in combination with
other ecological factors
leads to emergence of
hypoxic zones. 4
....HYPOX kickoff: Site introduction
Changes in deep-water biotopes of the
Black Sea connected to hypoxia (20th cent.)
In Crimean shelf at depths less than
30–40m the Chamelea gallina belt
community is located. The belt of silt
mussels Mytilus galloprovincialis
located the depth range 30–40m to
50–60m. The belt-community of
Modiolula phaseolina located the
depth range 50-135m. Boundary
displacement of main belt
communities to lesser depths revealed
in the end of XX century. This case can
be explained by global climate change
and increasing of anthropogenic
pollution impact on ecosystems.
Formation of stable zones of the
oxygen deficit in the near-bottom
water layers influenced the balance of
ecosystem. Finally it leads to rise of
the dead-zones of different scales. 5
....HYPOX kickoff: Site introduction
Changes in macrofauna diversity connected
to hypoxia 1950–1960 (1), 1970–1980 (2)
Modern composition of macrofauna
in the Crimea included 560 species.
While 463 species were registered in
the Crimean region benthos before
1975, in 1980–90s there were 471
species.
During the XX century the position
of macrofauna diversity changed
vertically. The reason of that
phenomena was change of the
oxygen rate in habitat (oxic-
hypoxic-anoxic).
55 macrozoobenthos species were
met at the depths of 100 and more
depths for the whole period of the
bottom fauna investigation at the
Crimean shores.
6
....HYPOX kickoff: Site introduction
Meiobenthos in the oxic/anoxic interface
of the NW Black Sea (2007)
Meiobenthos is distributed
irregularly. The meiobenthos
structure is defined by
development of the
eumeiobenthos.
Peak of meiobenthos
maximum is noted in the
zone of oxygen deficit at a
depth of 120 m, and the
second peak is at the depth
160m in anoxic area with
hydrogen sulfide presence.
7
....HYPOX kickoff: Site introduction
Meiobenthos taxonomic diversity in oxic/
anoxic interface of the Black Sea (2007)
.
Specific communities of the benthic
organisms were formed, adapting to
the limited oxygen concentration.
Meiobenthic fauna at the
oxic/anoxic interface of the Black
Sea (at the depths range 120-240
m) was numerous, specific and
diverse. Taxonomic diversity
decreased with depth. Deep water
fauna included 16 higher taxa.
Some species of Gromiida, Ciliates,
Foraminifera, Nematoda, two
species of Polychaeta and two
species of Tardigrada were
characterized by the best adaptive
ability to anoxic conditions.
8....HYPOX kickoff: Site introduction
Some specific deep-water biota in oxic-
anoxic interface of the NW Black Sea
Ciliophora Foraminifera
Nematoda Tardigrada
Gromia
Polychaeta
9....HYPOX kickoff: Site introduction
Meiobenthos in biogenic local redox-zone
in a shallow bay (Kruglaya Bay, SW Crimea)
Ciliophora Nemertini Ostracoda Kruglaya Bay (0,66 km2) is semi-closed
Foraminifera Polychaeta Amphipoda basin located in the SW part of Crimea,
Nematoda Bivalvia Harpacticoida included in the complex of large
Turbellaria Gastropoda Decapoda (juv.) Sevastopol Bay. Its depths are 2 -17 m.
Oligochaeta Acarina Tardigrada Low densities and mass mortality of
3000000 meiobenthos under hypoxic
conditions were not found as
expected. In central redox zones
2500000
Abundance, ind./m2
2000000 meiobenthos & macrobenthos were
diverse and abundant. Taxonomical
composition of meiobenthos
1500000
1000000 included organisms from 15 high
taxa. Taxonomical structure of
500000
meiofauna and quantitative
0 characteristics showed adaptation to
ar
y ry ch ril ay ne ly hypoxic conditions during the year.
u ua ar Ap M Ju Ju Months
Ja
n
Fe
br M The mechanisms of this phenomena
are not clear yet.
centre edge control
10....HYPOX kickoff: Site introduction
Aim of the HYPOX work at the site &
suggested key parameters to measure
-Study hypoxia expansion and biodiversity, and faunal responses to
variations in oxygen concentrations in the Crimea region and Bosporus;
-study of specially adapted benthic groups (Nematoda,Ciliata, Foraminifera,
Polychaeta etc.) in oxic/anoxic interface of both Black and Baltic Seas with
potential value as medium term redox indicators;
- assessing the history and effect of oxygen on benthic communities
(meiobenthic and macrobenthic species);
-analysis of available knowledge about past oxygen regimes and benthic
communities structure at selected target sites;
- study the phenomenon of horizontal near-bottom intrusions of aerated,
saline waters in the anoxic water column near the Bosporus outlet;
- study the benthic community distribution patterns in relation to depth,O2
and H2S gradients, and gas seepage of Crimea but also in the other target
areas of the Black Sea and in the Baltic Sea.
Key parameters: O2, CH4, H2S, temperature and salinity in water column and
in bottom sediments; benthic parameters (biomass, abundance, diversity).
11Thank you for attention
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