deliverable d 4.2 “report on assessment of changes in...
TRANSCRIPT
SEVENTH FRAMEWORK PROGRAMME Area 6.4.1.2. Cross-cutting research activities relevant to GEO
ENV.2008.4.1.2.1. Monitoring and observing oxygen depletion throughout the different Earth system components
Deliverable D 4.2 “Report on assessment of changes in oxygen availability using organic and inorganic proxies, benthic communities structure,
and hypoxia indicator species”, month 30 Editor: Namik Çagatay (ITU-EMCOL) with all
partners of WP4 Project acronym: HYPOX Project full title: In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and land-locked water bodies Grant agreement no.: 226213 Date of preparation: 03 October 2011, revised version: 09 January 2012
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TABLE OF CONTENTS
1.INTRODUCTION...................................................................................................................3
2.INORGANIC AND ORGANIC GEOCHEMICAL PROXIES...........................................3
2.1.Inorganic geochemical studies in the Istanbul Strait (Bosphorus) Outlet Area of
Black Sea (ITU-EMCOL)...............................................................................................3
2.2.Inorganic Geochemical Studies Lake Rotsee and Lake Zurich(EAWAG).............11
2.3.Porewater Phosphorus-Iron Dynamics in the Eckernförde Bay (SW Baltic Sea)
(IFM-GEOMAR)..........................................................................................................12
2.4.Inorganic and Organic Studies in Baltic Sea, Black Sea and meromictic lake Alat
(Fuessen Bavaria) (MfN)..............................................................................................15
2.5.Natural radionuclides studies in the Greek Lagoons (UPAT).................................16
2.6.Noble Gases in the Black Sea (EAWAG)...............................................................19
2.7.Biomarkers studies in the Lake Rotsee and Lake Zurich (both Switzerland),
Amvrakikos Gulf (Greece) and the Black Sea (EAWAG)...........................................20
3.BENTHIC COMMUNITIES ...............................................................................................22
3.1.Benthic communities structure and hypoxia indicator species in the Black Sea
(IBSS)............................................................................................................................22
3.2.Benthic foraminifera studies in the Greek Lagoons (UPAT)..................................45
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1. INTRODUCTION
This report summarizes the changes in oxygen availability using organic and inorganic
proxies, benthic communities‟ structure, and hypoxia indicator species in the Black Sea shelf
areas (Istanbul Strait outlet area and Crimean shelf and Sevastopol area), Greek Lagoons in
the Ionian Sea and the Swiss Lakes. The main objectives are to reconstruct the basin evolution
and past changes in the redox conditions and to give brief information about structures of the
benthic communities and species that indicate hypoxia in the various basins.
Study areas include the İstanbul Strait outlet area (Turkey), Crimean shelf and Sevastopol
areas (Ukraine) in the Black Sea; Lake Zurich and Lake Rotsee (Switzerland); and the
Amvrakikos Gulf in the Ionian Sea in western Greece.
2. INORGANIC AND ORGANIC GEOCHEMICAL PROXIES
2.1. Inorganic geochemical studies in the Istanbul Strait (Bosphorus) Outlet Area of
Black Sea (ITU-EMCOL)
Site description: İstanbul Strait (Bosphorus) is the only connection of Black Sea to the world
ocean via Sea of Marmara and Çanakkale (Dardannelles) Strait. The İstanbul Strait outlet area
of the Black Sea (ISBS) includes the shelf and upper slope areas north of the Strait (Fig. 1.1;
Hypox D4.3, 2010). This area is characterized by the Mediterranean inflow that is
responsible for the ventilation and sluggish deep circulation of the anoxic Black Sea basin
(Oğuz et al., 1993; Özsoy and Ünlüata, 1997). The anoxic/oxic boundary is located at a depth
of 100-150 m with a ~30 m thick suboxic zone (Murray et al., 1989; 1993; Codispoti et al.,
1991; Baştürk et al., 1994). Presently, a two-way current system occurs in the Bosphorus
channel, with the Black Sea water forming the upper current and the warm and saline
Mediterranean Water (MW) the undercurrent (Özsoy and Ünlüata, 1997; De Iorio et al., 1999;
Özsoy et al., 2001).
The MW enters the ISBS shelf through the submarine extension of the Istanbul Strait‟s
channel, and then spreads as a uniform 2-3 m thick saline sheet over the shelf. At depths of
50-75 m, it mixes with the Cold Intermediate Water (CIW) and sinks along the continental
slope forming a series of lateral intrusions to depths of 500 m.
4
Fig.2.1. Multibeam bathymetric map of the Istanbul Strait (Bosphorus) outlet area (Di Iorio
and Yüce, 1999; Flood et al., 2009).
The ISBS outlet area is also characterized by a fan-delta complex on the mid and outer shelf
areas with an anastomosing distributary channels, 5-8 m high levées, in-channel stream-lined
bars, cravasse splays, and NW-SE oriented linear to wavy sedimentary structures in between
the channel-levée complexes (Fig.2.1) (De Iorio and Yüce, 1998; Flood et al., 2009, Hypox
D.4.3, 2010). Shallow sill depth of the Istanbul Strait together with the oxygen consumption
by organic matter mineralization is responsible for the establishment of a permanent oxic-
anoxic boundary (chemocline) in the area. The oxic-anoxic boundary is presently at 100-150
m depth, but may have varied in the past as result of the changes in the amounts of the MW,
of riverine water input and global sea level.
Cores and Core analysis: Geophysical subbottom profiling and sediment coring along depth
transects from -75 m to -307 m on the shelf and upper slope areas onboard RVs Arar and MS
Merian were carried out within the framework of the EC FP7 Hypox project (Fig.2.2). A total
of 81 cores and 4 long cores were analyzed for physical properties using Geotek Multi-Sensor
Core Logger (MSCL;), 42 cores for elemental analysis by Itrax XRF Core Scanner, and 22
cores for total organic (TOC) and inorganic (TIC) contents by Shimadzu TOC analyser. 17
5
core samples were dated by AMS C-14 analysis. The core data produced by Hypox project in
the ISBS outlet area can be found in data portal PANGAEA Archive /http://www.pangaea.
de/search?count=10&q=arar_2009+geochemistry&minlat=&minlon=&maxlat=&maxlon=&
mandate=&maxdate=&env=All&offset=20 and http:// www.pangaea.de/ search?count =10&q
=MSM15%2F1+geochemistry&minlat=&minlon=&maxlat=&maxlon=&mindate=&maxdate
=&env=All&offset=0), and the discussion in Erdem (2011, MSc Thesis).
Holocene Basin Evolution: High resolution seismic profiles and sedimentary cores show the
evidence of two low stand shelf crossing unconformities: a post-Younger Dryas transgression
unconformity (α) and a younger unconformity (α1) that form the base of the channel-levée
complex dated at ca. 7 14
C kyr BP (Fig.2.3, Fig.2.4) (Aksu at al., 2002; Ryan et al, 2003;
Major et al., 2006; Flood et al., 2009; this Hypox study). The α1 unconformity was formed by
the subaqueous erosion by the latest saline Mediterranean inflow and subsequent deposition
of the fan-delta complex under mainly submarine conditions.
Fig.2.2. Bathymetric map of the Istanbul Strait‟s outlet area in the Black Sea, showing the
location of the seismic lines and cores.
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Fig.2.3. A part of the seismic profile SL-1 representing water depths of 90-95 m on mid shelf
area. The sedimentary units on top belong to the channel-levée complex. The unconformity α1
is a flat surface at -98 m. The sediments below the unconformity is dated at ca. 10 ka BP (post
Younger Dryas). Vertical exaggeration = 8.1. See inset map for location of the line shown
with red rectangle on Line SL-1.
Results of Inorganic Geochemical Studies: The anoxia development started after the latest
connection with Mediterranean. The oxic/anoxic boundary and changes in the bottom water
conditions in the slope area are detectable by Mn, S and Fe anomalies in the cores located
between -120 m and -150 m, which show the rise of the oxic/anoxic boundary to depths
between -120 m and -150 m around 6.8 ka BP (Fig.2.5 and Fig.2.6).
Mediterranean inflow initially used the NW trending main channel transporting oxygenated
waters to the western side of the area. This NW transport stopped at 5.3 ka BP. Anoxic
bottom water conditions started to prevail in the western area at that time as a result of this
change in the direction of the inflow. The ventilation effect of MW on the seafloor can be
observed in the eastern part of the outlet area down to at least -307 m (depth limit of the
transects) as indicated by high Mn counts on the XRF scanner profiles, whereas in the western
part of the area no active ventilation effect observed in the sedimentary record after 5.3 ka BP
(Fig.2.7 and Fig.2.8) (Erdem, 2011). Such Mn anomalies in upper slope cores, unassociated
with Fe and S anomalies, are probably formed by deposition of Mn(II) from the water
column.
7
Fig.2.4. A part of the seismic profile SL-4 water at depths of 85-90m on mid shelf area,
showing the levée deposits of a distributary channel. The unconformity α1 overlain by
sediments dated ca. 7 ka BP. Vertical exaggeration = 8.2. See inset map for location of the
line shown with red rectangle on Line SL-4.
Fig.2.5. XRF and TOC/TIC results of sediment core G17B collected from -120 m depth in the
western part (SL8) of the area above the present oxic/anoxic interface. Green shaded area
indicates a lower unit with abundant benthic shells showing oxygenated bottom water
conditions. Yellow shaded area on top indicates oxygen depleted bottom water conditions.
Elemental concentrations are in cps. See Fig.2.2 for core location.
8
In addition to Mn anomalies, the transition from oxic to anoxic conditions are shown by
changes in mud colour from gray green through gray and dark gray to black, and by the
disappearance of the euryhaline bivalves and benthic foraminifera.
A recent rise in the oxic/anoxic interface is determined in a sedimentary core collected at -83
m. This rise is indicated by increased values of Mn-Fe-S and high TOC at 7-13 cm interval,
corresponding to intersection of the oxic/anoxic interface with the shelf area (Fig.2.9) (Erdem,
2011). A 505 14
C a BP (uncalibrated) date obtained from 21-23 cm of this core, correlates
with the finding of Lyons et al. (1993), which concluded a similar event at 250-300 a BP
according to the radionuclide dating.
Fig.2.6. XRF and TOC/TIC results of sediment core 245 collected from -152 m depth in the
eastern part (SL1) of the area below the present oxic/anoxic interface. Green shaded area
indicates oxygenated bottom water conditions by high values of Mn, Ca, TIC and shell
abundance. Above the boundary, minor Mn fluctuations show the MW ventilation effect.
Elemental concentrations are in cps. See Fig.2.2 for core location.
9
Fig.2.7. XRF and TOC/TIC results of sediment core 311 collected from -307 m depth in the
western part (SL8) of the area below the present oxic/anoxic interface. Green shaded area
indicates past oxygenated bottom water conditions before 5.3 ka BP. Lighter green area shows
the transition zone from oxic to anoxic bottom water conditions. Present MW ventilation
effect is not recorded above the transition zone. Elemental concentrations are in cps. See Fig.
1.2 for core location.
Fig.2.8. XRF and TOC/TIC results of sediment core 192 collected from -307 m depth in the
eastern part (SL1) of the area below the present oxic/anoxic interface. MW ventilation effect
is indicated by Mn fluctuations throughout the core length. Elemental concentrations are in
cps. See Fig.2.2 for core location.
10
Fig.2.9. Ti normalized Mn-Fe-S element profiles and TOC/TIC results of sediment core G18
collected from -83 m depth in the western part (SL8) of the area above the present oxic/anoxic
interface. Yellow shaded area with enrichment of Mn-Fe-S record suggests oxic/anoxic
shoaling. Elemental concentrations are in cps. See Fig.2.2 for core location.
References
Aksu, A.E., Hiscott, R.N., Kaminski, M.A., Mudie, P.J., Gillespie, H., Abrojano, T.,
Yaşar, D., 2002. Last glacial-Holocene paleoceanography of the Black Sea and Marmara Sea:
stable isotopic, foraminiferal and coccolith evidence. Marine Geology 190, 119-149.
Baştürk, Ö., Saydam, C. Salihoğlu, I., Eremeeva, L.V., Konovalov, S.K., Stoyanov, A.,
Dimitrov, A., Cociasu, A., Dorogan, L. and Altabet, M., 1994. Vertical variation in the
principle chemical properties of the Black Sea in the autumn of 1991, Marine Chemistry, 45:
149-165.
Codispoti, L.A. Friederich, G.E., Murray, J.W., and Sakamato, C.M., 1991. Vertical
variability in the Black Sea: Implications of continuous vertical profiles that penetrated the
oxic/anoxic interface, Deep-Sea Res., 38(2A): 691-710.
Di Iorio, D., Akal, T., Guerrini, P., Yüce, H., Gezgin, E. And Özsoy, E., 1999. Oceanographic Measurements of the West Black Sea: June 15 to July 5, 1996. Report SR-
305, SACLANTCEN; NATO, La Spezia
Di Iorio, D., and Yüce, H., 1998. Observations of Mediterranean flow into the Black Sea:
Journal of Geophysical Research v. 104, no. C2, p. 3091-3108.
11
Erdem, Z., 2011. Sedimentary Record of Mediterranean Inflow Effect on Redox Conditions
of Istanbul Strait Outlet Area of Black Sea. MSc thesis, Eurasian Institute of Earth
Sciences.79 pages.
Flood, R. D., Hiscott, R. N., and Aksu, A. E., 2009. Morphology and evolution of an
anastomosed channel network where saline underflow enters the Black Sea: Sedimentology,
56: 807-839.
Hypox Report D4.3., 2010. Report on coring, marine geological and geophysical surveys, 71
pages.
Lyons, T.W., Berner, R.A., Anderson, R.F., 1993. Evidence for large pre-industrial
perturbations of the Black Sea chemocline, Nature 365, 538-540.
Major, C.O., Goldstein, S.L., Ryan, W.B.F., Lericolais, G., Piotrowski, A.M. and
Hajdas, I., 2006. The co-evolution of Black Sea level and composition through the last
deglaciation and its paleoclimatic significance, Quaternary Science Reviews Volume 25,
Issues 17-18, Pages 2031-2047. Murray, J.W., Jannasch, H.W., Honjo, S., Anderson; S., Reeburgh, W.S., Top, Z.,
Friederich, G.E., Codispoti, L.A. and Izdar, E., 1989. Unexpected changes in the
oxic/unoxic interface in the Black Sea, Nature, 338: 411-413.
Murray, J.W., Friederich, G.E., Codispoti, L.A., 1993. The suboxic zone in the Black Sea,
in C.P. Huang, C.R. O‟Melia and J.J. Morgan (eds.), Aquatic Chemistry, Advances in
Chemical Series No. 244, Am. Chem. Soc., Washington DC.
Oğuz, T., Latun, V.S., Latif, M.A., Vladimirov, V.V., Sur, H.I., Markov, A.A., Özsoy, E.,
Kotovshchikov, B.B., Eremeev, V.V., Ünlüata, Ü., 1993. Circulation in the surface and
intermediate layers of the Black Sea, Deep-Sea Res. Part I 40, pp. 1597-1612.
Özsoy, E., Di Iorio, D., Gregg, M. C., and Backhaus, J. O., 2001. Mixing in the Bosphorus
Strait and the Black Sea continental shelf: observations and a model of the dense water
outflow: Journal of Marine Systems, 31: 99-135.
Özsoy, E., and Ünlüata, Ü., 1997. Oceanography of the Black Sea: a review of some recent
results, Earth-Science Reviews, 42, 231-272.
Ryan, W.B.F., Major., C., Lericolais, G. and Goldstein., S.L., 2003. Catastrophic
Flooding Of the Black Sea. Annu. Rev. Earth Planet. Sci. 31, 525-554.
2.2. Inorganic Geochemical Studies Lake Rotsee and Lake Zurich(EAWAG)
For XRF Core Scanner inorganic elemental analysis we could obtain seasonal resolution.
Iron and manganese distributions show seasonality in Lake Zurich. Because of half-year
lamination patterns and calcium abundance changes within the year, we could establish a very
precise age model that allows us to observe a seasonality of trace metals. Our results suggests
that the higher abundance of iron during fall/winter depends either on when the first traces of
bottom water oxygen reach the sediments, the dilution of calcium, or an increased supply of
12
iron during winter. On the other hand, we observed higher abundances of manganese during
spring, which correlate well with higher bottom water oxygen concentrations. Therefore,
manganese traces oxygenation of bottom water during spring when the lake mixes.
2.3. Porewater Phosphorus-Iron Dynamics in the Eckernförde Bay (SW Baltic Sea)
(IFM-GEOMAR)
Site description: Boknis Eck is a small channel located at the northern entrance of
Eckernförde Bay (54 31‟N, 10‟20 E) and has a water depth of about 28 m (Fig.2.10). From
mid-March until mid-September, vertical mixing is restricted by density stratification of the
water column, which leads to pronounced periods of hypoxia during late summer due to
microbial respiration of organic material in the deep layer and sediment (Fig.2.11). Autumn
storms and a decrease in surface water temperature cause a mixing of the water column and
ventilation of the deeper water layers with increased nutrient concentrations.
Fig.2.10. Location (black square) of the time series station Boknis Eck in the Eckernförde
Bay (SW Baltic Sea).
The sediments at the study site in Boknis Eck are classified as fine grained muds (< 40 µm)
with a carbon content of 3 to 5 wt % (Balzer et al., 1986). With no significant terrestrial
runoff, the bulk of organic matter within Eckernförde Bay sediments originates from marine
13
plankton and macroalgal sources. The dominant fauna in the sediments in winter/spring are
the polychaetes Pectinariakoreni and Nephtys ciliate with recorded abundances of 201-476
and 63-122 individuals m-2
, respectively (Graf et al., 1982). Specimens up to 10 cm long were
present during winter sampling. Bacterial mats were absent on the surface of Boknis Eck
sediments at the time of sampling, but Beggiatoa are present below the sediment surface at
the redox interface at the top of the sulfide layer (Preisler et al., 2007). In late summer 2010
when the bottom waters became almost anoxic, a blackening of the surface sediments and
colonization by Beggiatoa filaments was observed.
Sampling time and resolution: Monthly multi-core samples with core length of ca. 30 cm
were obatained from Eckernförde Bay (SW Baltic Sea) from February 2010 until January
2011.
Phosphorus-Iron dynamics: During 2010, the sediments at a 28 m deep site in the Boknis Eck
channel (Fig.2.10) were sampled monthly and analyzed for their major nutrients and
geochemical constituents. The data were used to constrain a benthic model to study the
benthic cycling of redox sensitive elements and investigate how the pathways of organic
matter degradation and biogeochemical fluxes across the sediment-water interface respond to
changing O2 concentrations. The model includes organic matter degradation by aerobic and
anaerobic respiration pathways and can be used to quantify the total rate of O2 depletion in the
sediment. An example of the model application to data from winter 2010 can be found in Dale
et al. (2011) when oxygen levels in the bottom waters were high (Fig.2.11b).
Bottom water oxygen levels are well known to affect the dynamic of phosphorus and iron,
which are often highly coupled (Krom and Berner, 1981). Oxygen levels decreased through
spring into summer and by autumn the bottom water became anoxic. Selected porewater
profiles, including ferrous iron (Fe2+
) and phosphate (PO43-
), are shown in Fig.2.11a. The data
show how the concentrations of both species increase rapidly from September to October
following the onset of anoxia. Reductive dissolution of iron oxide minerals and release of
iron-adsorbed PO43-
very likely explains these observations. To interpret these findings
quantitatively, the numbers at the top of the figure panels denote the diffusive fluxes of PO43-
out of the sediment in mmol m-2
d-1
. The flux increased by a factor 10 from 0.4 mmol m-2
d-
1in September and 4.2 mmol m
-2 d
-1 in October, remained fairly high in November and then
returns to background levels in December when fully oxic conditions are restored in the
bottom water.
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Fig.2.11. (a) Measured porewater concentrations of phosphate and ferrous iron in the upper
30 cm of Boknis Eck sediments during autumn 2010. The red lines approximate the
concentration gradients in the surface layers, and the diffusive fluxes calculated from these
slopes are shown above the panels. (b) Measured bottom water (28 m) oxygen concentrations
during 2010 at Boknis Eck (September, October and November samplings are indicated).
The results demonstrate the dynamicity of the sediments over the short autumn anoxic period
and the potential importance of the benthos in supplying nutrients to the water column for the
following spring. Ongoing work will address whether the PO43-
and Fe3+
fluxes out of the
sediments are determined directly by the onset of anoxia or indirectly by animal mortality and
hiatus in bio-irrigation.
Sep Oct Nov Dec
0.4 4.2 1.4 0.5
S O N
(a)
(b)
15
References
Balzer, W., Pollehne, F., Erlenkeuser, H., (1986). Cycling of organic carbon in a coastal
marine system. In: P.G. Sly, Editor, Sediments and Water Interactions, Springer Verlag, New
York pp. 325–330.
Dale, A. W., Sommer, S., Bohlen, L., Treude, T., Bertics, V. J., Bange, H. W.,
Pfannkuche, O., Schorp, T., Mattsdotter, M., Wallmann, K. (in press., 2011). Rates and
regulation of nitrogen cycling in seasonally hypoxic sediments during winter (Boknis Eck,
SW Baltic Sea): sensitivity to environmental variables. Estuarine, Coastal and Shelf Science.
Dale, A.W., Sommer, S., Pfannkuche, O., Wallmann, K. Changes in Fe and P redox
dynamics in marine sediment during the onset and recovery of seasonal bottom water
hypoxia. Planned submission 2012.
Graf, G., Bengtsson, W., Diesner, U., Schulz, R., Theede, H., (1982). Benthic response to
sedimentation of a spring phytoplankton bloom: Process and budget. Marine Biology 245,
201-208.
Krom, M. D. Berner, R. A., (1981). The diagenesis of phosphorus in a nearshore marine
sediment. Geochimica et Cosmochimica Acta 45, 207-216.
Preisler, A., de Beer, D., Lichtschlag, A., Lavik, G., Boetius, A., Jørgensen, B. B., (2007).
Biological and chemical sulfide oxidation in a Beggiatoa inhabited marine sediment. The
ISME Journal 1, 341-353.
2.4. Inorganic and Organic Studies in Baltic Sea, Black Sea and meromictic lake Alat
(Fuessen Bavaria) (MfN)
In the frame of a master thesis in geosciences at the Freie University Berlin three short (Jacob
2011) sediment cores were studied for the impact of eutrophication in the northern most
Baltic Sea (Bottenwiek). Results indicate that during the past hundred years the area of the
Bottenwiek was eutrophied only to a small extent. However, sedimentary d15N and d13C
(TOC) show clear trends towards higher values in more recent sediments (the last 2 decades)
indicating the increasing bioproductivity and more nutrients in that area (Jacob, 2011).
In the frame of a BSc thesis in geosciences at the Freie Universität Berlin the physico-
chemical stratification and stability of the meromictic and anoxic lake Alat was studied with
respect to influence of the dense population of purple sulfur bacteria on the nitrogen cycle.
16
Green or purple sulfur bacteria had probably a significant impact in the nitrogen cycle during
phases of strong anoxia in earth history (Falk, 2011).
Water samples and surface sediments obtained from the short cores are used for the analysis
with a sub-decadal resolution. Ages are obtained by the 210Pb-dating method.
Planned publications are; 1)Fritz G.B., Pfannkuchen M., Struck U., Hengherr S., Strohmeier
S. & Brümmer F. (in press) Characterizing an anoxic habitat: sulphur bacteria in a
meromitic alpine lake. In: J., Seckbach (Ed.) /Anoxia: Fossils, Anaerobic and
Microaerophiles./ Cellular Origin, Life in Extreme Habitats and Astrobiology, Springer
Verlag. 2) Struck U. (in press). On the use of stable nitrogen isotopes in present and past
anoxic environments. -In: J., Seckbach (Ed.) /Anoxia: Fossils, Anaerobic and
Microaerophiles./ Cellular Origin, Life in Extreme Habitats and Astrobiology, Springer
Verlag.
References
Falk, M., 2011: Physico-chemical stratification and stability of the meromictic lake Alat. -
BSc thesis Geosciences, Freie Universität, Berlin, Supervisor: M. Schneider, 27pp.
Jacob, J., 2011: Ablagerungsgeschichte des anthropogenen Einflusses in der nördlichen
Ostsee während der letzten 100 Jahre. - MSc-Thesis, Geoscience, Freie Universität Berlin,
Supervisor: U. Struck, 84pp.
2.5. Natural radionuclides studies in the Greek Lagoons (UPAT)
Activity concentration of natural radionuclides (238
U, 232
Th, 226
Ra, 40
K) and man-made 137
Cs
were determined in sediment cores collected from 5 different sampling sites from the
Amvrakikos Gulf (Fig.2.12). The total concentrations of Fe and Mn were also determined and
compared to U total concentration. To obtain information on the distribution of metals and
radionuclides in various chemical fractions of the sediments, sequential extraction procedures
(BCR) were used.
17
Fig.2.12. Map of Amvrakikos Gulf showing the sediment sampling locations.
The enhanced uranium activity levels found in the sediment samples and the disequilibrium
between 238
U and 232
Th are mainly associated with the phosphate fertilizer inputs in the Gulf
via the rivers (Fig.2.13 and Fig.2.14). The highest 238
U activities and the highest values of
U/Th ratio were observed at the uppermost part of the sediment cores (Fig.2.13). Moreover,
the sequential extraction results further support the above interpretation (Fig.2.15). A
significant percentage of uranium was found in the mobile fractions, which might be
attributed to an input of phosphate fertilizers that hold radioactive materials, especially
uranium, in the Gulf, and to a lesser extent to the transport of phosphate rocks experienced
alteration processes (leaching of U by ground or surface water from a source rock). 137
Cs was
found in measurable concentrations (5.2 – 20.2 Bq kg-1
) in all surface sediments (0-8 cm),
while higher activity concentrations of 137
Cs were found in the deeper sediment layers than in
the surface one, suggesting a high sedimentation rate for the Amvrakikos Gulf.
18
Fig.2.13. Downcore distribution of 238
U activities in the sediment cores collected from
Amvrakikos Gulf.
Fig.2.14. Downcore distribution of 238U/
232Th in the sediment cores collected from
Amvrakikos Gulf.
Fig.2.15. Diagram showing the results of Sequential extraction results (BCR) for 238
U in
sediment samples collected from Amvrakikos Gulf.
0%
20%
40%
60%
80%
100%
U U U U U U U U U U U U
Residual
BCR C Step
BCR B Step
BCR A Step
Core 2 Core 9 Core 13 Core 16
2/1 2/5 2/7 9/1 9/3 9/5 13/1 13/4 13/6 16/1 16/3 16/4
19
References
Athanassopoulos D., H., Papaefthymiou, G., Papatheodorou, M., Iatrou, M., Geraga, D.,
Christodoulou, E., Fakiris, 2011. Physical and chemical associations of natural
radionuclides and 137Cs in the sediments of a Mediterranean fjord-like embayment,
Amvrakikos Gulf (Ionian Sea), Greece. (Submitted for publication).
2.6. Noble Gases in the Black Sea (EAWAG)
In the Black Sea we aim to reconstruct hypoxia through determination of atmospheric noble
gases (He, Ne, Ar, Kr and Xe) in the pore-waters of unconsolidated sediments (Brennwald,
2004; Tomonaga, 2011a) and test our hypothesis based on samples from different water
depths at different locations. We will have a particular focus on the transitions of unit 1, 2 and
3 which represent the transition of the Black Sea from a rather oxic, limnic basin into a
brackish, hypoxic, anoxic and euxinic state. Samples were taken from sediment cores
collected in three regions (Fig.2.16): near the Bosphorus Strait (3 cores), the Crimean Shelf (3
cores) and the Romanian shelf (3 cores).
Analysis of the collected sediment samples is ongoing and results should become available in
the coming months.
References
Analysis of dissolved noble gases in the pore water of lacustrine sediments. Limnol.
Oceanogr. Methods, 1:51–62.
Brennwald, M. S. (2004). The use of noble gases in lake sediment pore water as
environmental tracers. Diss. ETH Nr. 15629, ETH Zurich.
Brennwald, M. S., Peeters, F., Imboden, D. M., Giralt, S., Hofer, M., Livingstone, D. M.,
Klump, S., Strassmann, K., and Kipfer, R. (2004). Atmospheric noble gases in lake
sediment pore water as proxies for environmental change. Geophys. Res. Lett., 31(4), L04202,
doi:10.1029/2003GL019153.
20
Brennwald, M. S., Imboden, D. M., and Kipfer, R. (2005). Release of gas bubbles from
lake sediment traced by noble gas isotopes in the sediment pore water. Earth Planet. Sci.
Lett., 235(1-2):31–44, doi:10.1016/j.epsl.2005.03.004.
Tomonaga, Y. (2010). T Noble gases as tracers for transport of solutes and fluids in lake and
ocean sediments. Diss. ETH Nr. 18923, ETH Zurich., doi:10.3929/ethz-a-006129449.
Tomonaga, Y., Brennwald M. S., and Kipfer, R. (2011a). An improved method for the
analysis of dissolved noble gases in the pore water of unconsolidated sediments. Limnol.
Oceanogr. Methods, 9:42-49, doi:10:4319/lom.2011.9.42.
Tomonaga, Y., Brennwald M. S., and Kipfer, R. (2011b). Spatial distribution and flux of
terrigenic He dissolved in the sediment pore water of Lake Van (Turkey). Geochim.
Cosmochim. Acta, in press.
2.7. Biomarkers studies in the Lake Rotsee and Lake Zurich (both Switzerland),
Amvrakikos Gulf (Greece) and the Black Sea (EAWAG)
For the biomarker studies the sediment cores were recovered from the study areas, with the
following details:
Lake Rotsee: 50-60cm long sediment cores were obtained from 16 m water depth (maximum
lake depth).
Lake Zurich: 3 locations at water depths of 45 m (51 cm long), 109 m (94cm long) and 139 m
(110 cm long, maximum lake depth).
Amvrakikos Gulf: 30cm long cores from 2 locations in water depths of 29 and 39 m.
Black Sea: Multi-collector cores between 30-50 cm long, noble gas cores up to 2.5m long,
and reference cores up to 2.5m long. All cores are from the Crimean and the Romanian Shelf
and from sampling stations offshore from the Bosporus Strait outlet area.
According to the radionuclide analysis of the cores, the covered time of the cores obtained
from Lake Rotsee is extends back to about 150 a, for Lake Zurich, the longest record from
139 m water depth, covering at least the last 110 a; the lower limit is unclear because of high
21
amounts of turbidites without much lamination. The cores from Amvrakikos Gulf still need to
be dated while the longest Black Sea core dates back to about 10-11.5 ka.
Biomarker analyses from Lake Rotsee cores represent a resolution of about 3 years in the
majority of the core, but lower below 30 cm. For Lake Zurich the highest resolution is up to 5
years, only applicable in the upper part of the core. For the Amvrakikos Gulf and the Black
Sea we cannot make any statements about analytical resolution at this stage of the work.
Lake Rotsee biomarker analysis represents a high-resolution biomarker study that revealed a
complete eutrophication history starting in the 1850s. We observe times of higher primary
productivity, which can be explained by high nutrient input from the catchment through
agriculture and untreated sewage. Periods of higher productivity resulted in higher
abundances of phytoplankton and bacteria and resulted in an enhanced stratification.
Furthermore, the higher productivity resulted in an enhanced supply of organic matter (OM)
to the sediments, which increased the overall hypolimnetic oxygen demand. The high OM
supply to the sediments is related to higher abundances of methanogens in the sediment,
leading to increased emission of methane into the water column. The abundance of
methanotrophs due to the higher methane emissions increased with a few years delay. Since
the construction of sewage treatment plants in the 1970s, the lake is slowly recovering.
In Lake Zurich lipid biomarker degradation is probably dependent upon oxygen abundance in
the water column. Such a relationship would explain finding lower concentrations of
biomarkers at shallower water depths with higher oxygen concentrations.
All results of Amvrakikos Gulf and Black Sea are preliminary. For the Amvrakikos Gulf, we
could show higher terrestrial contribution at the sampling station near the Preveza strait. Two
biomarkers, isorenieratene and okenone, indicating at least seasonal photic zone anoxia, could
be identified in the Amvrakikos Gulf.
In Amvrakikos Gulf, we plan to combine biomarkers and benthic faunal data, supported by
other geochemical parameters, to reconstruct hypoxia in this embayment. We will try to
compare Amvrakikos Gulf with the Black Sea concerning the development of hypoxia,
showing similarities and differences between both sites.
22
3. BENTHIC COMMUNITIES AND HYPOXIA INDICATOR SPECIES
3.1. Benthic communities structure and hypoxia indicator species in the Black Sea
(IBSS)
In line with Task 4.4 and D 4.1, an extensive study of the benthic community structure and
hypoxia indicator species was carried out by IBSS in the Crimean shelf and Istanbul Strait‟s
(Bosphorus) outlet area of the Black Sea. The samples for the studies and data on
oceanographic and benthic environmental conditions were collected during the Hypox cruises
on board RVs Arar and M. S. Merian during November 2009 and April/May, 2010. In the
coastal zone of the Crimea, sampling was made every 45 days throughout the year. The
analyses in the water column involved CTD and dissolved O2, and in sediment pore waters
dissolved O2 and H2S concentrations.
Sediment sampling for the biological studies were carried out using multi-corer (TVMUC),
push-corer and box corers. At each station, the sediment cores were sampled in 0-1, 1-2, 2-3,
3-5 cm below sea floor (cmbsf) intervals.
Crimean shelf: Five selected areas for the HYPOX project were studied: 1) Dnepr Canyon
(Paleo-Delta), 2) Tarkhankut seeps, 3) Sevastopol areas: Omega (Kruglaya) Bay, 4)
Sevastopol Bay: inner part (Yuzhnaya bay), 5) Sevastopol Bay: outer part (reference site).
IBSS focused its studies on the changes in taxonomic structure, quantity and biomass of
modern meiobenthos in response to seasonal hypoxia in the environment in the above target
coastal sites of the Crimea. The structure and distribution of meiobenthic fauna was analyzed
from the seafloor to 5-7 cm sediment depth. Oceanographic and O2 and H2S (by voltametric
profiling) concentrations in the sediment pore waters were carried out at a sub-millimeter
vertical resolution to a depth of 100 - 400 mm below seafloor.
Sampling interval in coastal zone of the Crimea was every 45 days. An additional sampling
cruise was carried out in the Paleo Dnepr region during the April-May 2010.
Tarkhankut seeps: The cape Tarkhankut is the most western part of Crimea (Fig.3.1), where
there are no anthropogenic and industrial sources of pollutants. The most prominent natural
feature of this region is the presence of shallow methane seeps. Seeps are distributed along an
axis of the Kalamit Ridge.
The flow of methane from the sediments to the water column at this site ranges from
17 µl·dm-2
·day-1
(12 mkg·dm-2
·day-1
) for well-aerated sites with strong oxidizing conditions
23
Fig.3.1. Study area at the Tarkhankut Cape
Fig.3.2. The flow of methane from the sediments to the water column at Tarkhankut Cape
(July 2010)
to 81700 µl·dm-2
·day-1
(58,000 mkg·dm-2
·day-1
) for sediment with active processes of
methane genesis (Fig.3.2).
Results of voltametric profiling of all sediment cores retrieved on different seasons reveal the
presence of sulfide inside the bacterial mat, when the mat existed. The usual vertical profile of
sulfide in porewater demonstrates an increase of the concentration of sulfide from zero or
minimal values at the surface of sediments to the highest values at a depth of 40 to 70 mm. An
interesting feature is the decline in the vertical distribution of sulfide concentrations with
24
depth below 10 cm. Though the source of methane is located deeper in sediments, methane
consuming bacteria need also an oxidizer (oxygen, oxidized forms of nitrogen, manganese,
iron, or sulphate) and nutrients to make oxidation of methane possible and to build up
bacterial biomass. As sources of methane, oxidizers, and nutrients are located in different
layers, there is a depth of the optimal ratio of their fluxes.
The only time of sulphide absence in the bottom sediments is the period of winter storms,
when bacterial mats are completely disintegrated and sandy material is well washed to reveal
any presence of bacterial biomass. As soon as sediments are undisturbed for several weeks, a
new bacterial mat is formed resulting in suboxic and anoxic/sulfidic conditions. Thus, an
average annual cycle of redox conditions consists of two seasonal periods - minimal or no
sulfide period of winter storms and the sulfide maximum at the end of summer. The minimal
concentrations of sulfide were about 50 µM at the depth of 25 to 60 mm with no or extremely
low concentration of sulfide in the upper 15 mm of sediments and the concentration of oxygen
as high as 250 µM in waters located 2 to 3 mm above the surface of sediments. On the time of
maximum concentrations of sulfide at the end of summer, the sulfide concentrations can
easily reach 1500 µM and it was almost 3000 µM in September of 2009. The concentration of
sulfide reached 1000 µM at the surface of sediments that revealed extremely high vertical
gradients of sulfide and oxygen. In September of 2009, waters were oxygenated at the
distance of 10 cm above the mat, but oxygen disappeared at the distance of 2 mm above the
mat. Sulfide appeared and its concentration sharply increased with depth. In December of
2009, the vertical distribution of oxygen and sulfide was different. There was oxygen at the
surface of the mat, but its concentration decreased with depth and oxygen disappeared at the
depth of 4 mm. Sulfide was detected within the mat, but its maximum concentration had
decreased by two orders of magnitude (Fig.3.3 and Fig.3.4).
The meiobenthos density in the upper 5 cm layer of sediments varies widely depending on
redox conditions. The population density varies during the day for each of
the sites. Meiobenthos communities were provided with plenty of bacterial organic matter,
but a limited flux of oxygen at the redox habitat. The abundance of meiobenthos is higher and
it ranged from 97·103 to 632·10
3ind/m
2 and from 243·10
3 to 800·10
3ind/m
2 at two reference
sites during the day.
25
05.09.2009 12-00 05.09.2009 19.00 06.09.2009 7-00
November 2009 June 2010
Fig.3.3. The vertical distribution of oxygen and sulfide in the sediments of the Tarkhankut region
Fig.3.4. Seasonal variations in the distribution of oxygen and sulfide in porewaters of methane fed
microbial mat.
26
An expected (classical) distribution of the abundance and diversity of meiofauna has been
observed at the reference site, where these characteristics are the highest in the upper layer.
Contrary to this, the meiofauna abundance in the sulfidic sediments is higher in the lower
sediment layers where the hydrogen sulfide concentration reaches its maximum. At the same
time, taxonomic richness is similar in all layers (see also D4.3 report the taxonomic richness
and number of main meiobenthos taxa in horizons of the bottom sediment column under high
H2S concentration and under normoxia, (reference site).
Indicator species: Harpacticoida relating only to one species of Darcythompsonia fairlensis
(Scott, 1899) have been found at a depth of 3.5 cm of the anoxic/sulfidic bacterial mat in
September 2009. Interestingly, these species have never been reported for the Black
Sea. Analysis of the vertical distribution of D. fairlensis in the sediments from the surface to a
depth of 7 cm with an interval of 1 cm showed the highest concentration of species in a layer
of 4-5cm, where oxygen is absent, and high concentrations of hydrogen sulfide is present. In
this layer of sediments, adult females, males, and copepodites at different stages have been
found.
Data for July 2010, when „alive‟ samples were analyzed, very the same data were obtained.
We found alive and actively moving individuals of D. fairlensis, which proved their tolerance
to these environmental conditions. At the reference site, in normoxia, Harpacticoida species
composition was more diverse, but these species were absent.
D. fairlensis is one of the few species of the order Harpacticoida, which is known to inhabit
anoxic and hypoxic environments in other seas (Cristoni et al, 2004). This is endobenthic
species, as it usually exists in shallow waters on decaying plant material. Following its
distribution, "the ancestral stock of Darcythompsonia could have originated in the equatorial
Thetys Sea at during the Late Triasic - Early Jurassic periods" (Gomez, 2000).
Thus, rich well-developed populations of the harpacticoids species D. fairlensis have been
found in anoxic sediments and they may used as an indicator of hypoxic conditions.
Our studies of the response of main taxa and the depth of penetration of fauna in anoxic /
sulfidic sediments demonstrate that some benthic fauna is adaptive to toxic H2S environment.
Sevastopol areas: Seasonal changes oxygen concentrations were studied in water column.
Attendant factors in near-bottom layer water column and hydrogen sulfide in bottom
sediments were studied in target sites. Different sources of organic carbon (urban in the
27
Omega Bay and industrial in the Sevastopol Bay) may effectively support hypoxia or anoxia
of bottom sediments from different regions.
The method of voltametric profiling including application of a glass Au-Hg microelectrode is
used to collect pioneer data on high resolution vertical profiles of oxygen, dissolved sulfide,
oxidized and reduced iron, reduced manganese, and iron monosulfide in pore waters and to
study regional variations in chemistry of sediments in the bays near Sevastopol. It is shown
that vertical distribution of red-ox species is governed by a combination of three major factors
– content of organic carbon, content of reactive iron, and the particles‟ size of sediments.
O2 and H2S concentrations in the pore water in bottom sediments column in target sites were
measured in 2009-2010. On the target station were detected: temperature, salinity, O2, PO4,
Silicates, NO3, NO2, NH4 BOD5 (D3.4 Tabl. 2 and Tabl. 3).
Parallel to this we analyzed distribution of meiobenthic fauna from surface of sediment to 5-7
cm depth. Some meiobenthos species as indicators of hypoxia in coastal area are revealed.
Sevastopol Bay: The inner part of the Bay has regular hypoxic events as result the effects of
anthropogenic/industrial pollution last decades and restricted water exchange and low
freshwater input (Fig.3.5). Biogeochemical conditions of sediments in the bay's environment
are so extreme that hypoxia had become a regular feature of the inner part of the bay on
summer time. To make matter worse, sediments are sulfidic and serve as a source of hydrogen
sulfide for the bottom layer of water and make influence on the benthic communities.
Nutrients are released to the bay with the Black river waters and with urbun and industrial
waste waters providing intensive eutrophication of the bay. Besides, artificial piers at the
bay's entrance dramatically limited the intensity of water exchange between the bay and the
open part of the sea (Romanov et al., 2007). As the result, the sediments in bay are reached in
organic carbon, which is on average 4%, but may locally reach 7%. Such sediments support
intensive consumption of oxygen both in sediments and from the near-bottom layer of water
and this result in anoxic and hypoxic conditions (Orekhova and Konovalov, 2009).
28
Fig.3.5. Study sited of Sevastopol Bay (Inner and Outer parts)
Sediments in the inner part of the Sevastopol Bay are always anoxic / sufidic, but the
concentration of sulfide does not increase dramatically. We observed temporal variations of
hydrogen sulfate concentrations in the bottom sediment column, whereas O2 is observed only
on the sediment‟s surface. H2S appeared in 2 - 20mm of depth depending on the season.
Concentration of H2S is low during all the period of investigations (Fig.3.6).
We have demonstrated that oxygen does not penetrate to sediments deeper than 2 mm. Sulfide
is traced in the upper 10 mm layer of sediments. Sometimes, sulfide presents at the surface of
sediments supporting the flux of sulfide from sediments to water.
The outer part of the bay is still rather clean (see Fig. 2.5). This part is actually a paleo river
bed of the same river that currently releases its waters in the head of Bay. Intensive along
shore currents effectively mix and transport pollutants off the coastal sources and the bay.
Hypoxic events have never been reported for the waters of the outer part of the Sevastopol
Bay and the oxygen content is under influence of natural seasonal changes in T-S properties
and biological activities.
Outer part of Sevastopol Bay was chosen as a reference site. Similar to other sites, the oxygen
concentrations increase from summer to winter due to the increase in oxygen solubility
(Fig.3.7). As compared to the other sites, BOD remains rather constant and at the minimum
level due to a less heavy load of OM and more intensive ventilation in all seasons.
The Kruglaya (Omega) Bay is located at the shoreline of Sevastopol city, but no industrial
objects are located around the bay (Fig.3.8). Instead, there are resorts, parks and apartment
buildings at its coast. The water exchange is restricted due to the shape of the bay with a
29
broader inner part and a narrower outlet. There are several beaches at the coast of the bay, but
no technological objectives are located in its vicinity. Thus, anthropogenic pressure is
presented by urban waste waters.
Small depths, rather weak ventilation on summer time, discharge of municipal waste waters
results in hypoxic conditions at the bottom. Concentrations of oxygen in water column
typically increase from summer to winter due to more intensive ventilation. Yet, biochemical
oxygen demand (BOD) also increases from summer to winter suggesting that the load of OM
remains constant, but the rate of OM respiration decreases with the drop of temperature.
Inorganic nitrogen does not expose a straight forward pattern, but the highest concentration of
NH4 corresponds to the maximum of BOD, while nitrate increases in line with oxygen.
July 2009 September 2009 October 2009
December 2009 January 2010
Fig.3.6. The vertical distribution of oxygen and sulfide in the sediment core from the
Sevastopol Bay (inner part)
0 50 100 150 200 250
O2, µM
0
20
40
60
80
100
120
140
160
180
200
Depth
, m
m
0 0.5 1 1.5 2H2S, µÌ
bottom layer of water
0 50 100 150 200 250
O2, µM
0
20
40
60
80
100
120
140
160
180
200
Dep
th,
mm
0 0.5 1 1.5 2
H2S, µM
bottom layer of water
0 50 100 150 200 250
O2, µM
200
180
160
140
120
100
80
60
40
20
0
Dep
th,
mm
0 0.5 1 1.5 2
H2S, µM
bottom layer of water
0 50 100 150 200 250
O2, µM
200
180
160
140
120
100
80
60
40
20
0
Dep
th,
mm
0 50 100 150 200 250
H2S, µM
bottom layer of water
0 50 100 150 200 250
O2, µM
0
20
40
60
80
100
120
140
160
180
200
Dep
th,
mm
0 0.5 1 1.5 2
H2S, µM
bottom layer of water
30
July 2009 October 2009 January 2010
Fig.3.7. The vertical distribution of oxygen and sulfide in the sediments from the Sevastopol Bay
(outer part)
Fig.3.8. Study site at (Kruglaya) Omega Bay
We traced extremely low concentrations of oxygen in the near-bottom layer of water and in the upper
layer of sediments in July of 2009. Sulfide was detected in the near-bottom layer of water and it
increases in sediments reaching its maximum of 818.1 µM at the depth of 19 mm, and it
decreased with depth, but remained above 140 µM within the profiled core. Yet, this situation
is highly dynamic. It varies inter-annually. Thus, the situation was different in September of
2009 both in terms of the concentrations and vertical distribution of oxygen and sulfide.
Those changes were rather expected because the water column stratification had decreased
and the intensity of vertical exchange, thus the downward flux of oxygen, had increased from
summer to fall. Yet, the bottom sediments remained anoxic / sulfidic below 40 mm, though
the concentration of sulfide had decreased (Fig.3.9).
0 50 100 150 200 250 300 350 400 450
O2, µM
0
20
40
60
80
100
Dep
th,
mm
0 10 20 30 40
H2S, µM
bottom layer of water
0 50 100 150 200 250 300 350 400 450O2, uM
100
90
80
70
60
50
40
30
20
10
0
Dep
th,
mm
0 2 4 6 8H2S, uM
0 50 100 150 200 250 300 350 400 450
O2, µM
0
20
40
60
80
100
Depth
, m
m
bottom layer of water
31
July 2009 September 2009 December 2009
Fig.3. 9. The vertical distribution of oxygen and sulfide in the sediment cores in the Omega Bay
Unlike in the Omega Bay, the redox conditions in the Sevastopol Bay are more stable and
hypoxia is a quasi-permanent feature of this system. Local and seasonal hypoxia on bottom of
the Sevastopol bays and its impact on benthos were studied. Abundance of every macro – and
meiobenthos size groups were shown different dependence on the changes of depth of
hydrogen sulfide appearance in the bottom floor in all three points in the Sevastopol region.
Such varied benthos densities could indicate to an influence of hypoxia on benthos. In
general, abundance of the benthic animals usually decreases nearing of the hydrogen sulfide
boundary to the bottom surface. Such reaction is more visible for high abundant taxa.
Total macrobenthos abundance decreases with hydrogen sulfide boundary coming closer to
the bottom ground surface (Fig.3.10). Among the taxonomic groups the same fact was
revealed in Annelida and Bivalvia. At the same time Gastropoda reaction differed in separate
points, and Crustacea abundance increased with H2S approaching to the bottom ground
surface. (Zaika et all, 2011).
0 200 400 600 800 1000
O2, H2S, µM
0
10
20
30
40
50
60
70
80
90
100
110
Dep
th,
mm
bottom layer of water
0 50 100 150 200 250 300 350
O2, µM
0
10
20
30
40
50
60
70
80
90
100
110
Depth
, m
m
0 5 10 15 20 25 30
H2S, µM
bootom layer of water
0 50 100 150 200 250 300 350
O2, µM
0
10
20
30
40
50
60
70
80
90
100
110
Depth
, m
m
0 5 10 15 20 25 30
H2S, µM
bottom layer of water
32
Fig.3.10. Total macrobenthos quantity in three points: Yuzhnaya bay, Omega bay and reference site.
The series of data, ranged according to the depth of the hydrogen sulfide appearance has been
created. This series was considered to be an indicator of a degree of hypoxia. When the data
were ranged in accordance with hydrogen sulfide appearance in the core, then three
distinctive groups of locality were revealed: (1) H2S is observed in the surface of bottom
sediments and even in near-bottom water, (2) H2S is appeared at the depth 2 - 4 mm in the
core, (3) H2S is registrated at the depths 12 – 36 mm in the core. At the same time all the
samples from Yuzhnaya bay are fallen within third group, the samples from reference site –
within the second and third groups, and the site in Omega bay shows the most variable results.
Outcrop of H2S was observed exactly in Omega Bay in July and December, but in October it
was marked in the sediment at the depth 36 mm. That is why benthos response is more
distinctive just in Omega bay. It was compared with general benthos quantity, with its main
taxa group‟s abundance (Fig.3.11).
Fig.3.11. Total macrobenthos abundance depending on the hydrogen sulfide appearance depth in the
ground (firm line – Omega bay, dash line – united data for two other points)
0
10 000
20 000
30 000
40 000
50 000
60 000
VII. 09 VIII. 09 X. 09 XII. 09 I. 10 III. 10 V. 10 VII. 10
Ind
.m2
Yuzhnaya Bay Reference site Omega Bay
33
The local and season differences are showed up in the dynamic of meiobenthos abundance in
the studied sites (Fig.3.12). Abundance of meiobenthos in the Sevastopol Bay and reference
site in contrast to abundance in the Omega Bay reached its maximum by July 2009. In Omega
maximum of abundance in May 2010 was observed (Fig.3.12). Taxonomic structure and the
dominant groups were changing during study period.
In gastropodes, crustacea (in macrobenthos) and nematodes (in meiobenthos), we revealed a
contrary tendency: the closer to surface is the hydrogen sulfide boundary, the more is their
abundance. This is clearly observed in nematodes, among which quite a lot of species prefer
hypoxic habitats.
Fig.3.12. Dynamics of general quantity of meiobenthos is in three sites
Indicator species: It was recorded 15 species of Harpacticoida in the inner part of Sevastopol
Bay. Herewith Haloschizophera pontarchis was dominated the community under strong
hypoxic conditions.
At the Kruglaya Bay the seasonal dynamics of Harpacticoida species was observed. At the
moment when oxygen concentration drops significantly in the bottom sediment, the
Harpacticoida species composition changes were registered. Thus, it was found 12 species
with dominating of Darcythompsonia fairliensis in July 2009 when in October 2009 under
0
250
500
750
1000
1250
1500
1750
2000
July Sept Oct Dec Jan March May July
tho
us
an
d in
d./
m2
Sevastopol Bay Reference site Omega
34
normoxic conditions interstitial species Scotopssyllus sp (gen. Scotopssyllus) was dominated
and D. fairliensis was found absent.
It is noted that D. fairliensis from Kruglaya Bay had appeared and attained maximum
densities only under reduced conditions at the sediments. As be marked higher, rich well-
developed populations of the harpacticoids species D. fairlensis have been found in anoxic
sediments in the Tarkhankut Cape region.
It is thus; two species H. pontarchis and D. fairlensis (Copepoda, Harpacticoida) may be as
an indicator of hypoxic conditions in bottom sediments at coastal zone of Crimean shelf. The
analysis of species composition of other main groups of the meiobenthos is proceeding.
The İstanbul Strait (Bosporus) outlet area: The transition between hypoxic, but non-sulfidic
bottom water and the anoxic/sulfidic zone in the Black Sea is the ideal area to search for
animals thriving under hypoxic conditions. We investigated the response of the benthic fauna
on oxygen depletion in this zone at the Bosporus Strait region and in the Crimean Shelf area
along a water depth transect between 100 and 300m.
Benthic fauna analyses suggest that the oxic/anoxic transition zone supports a high abundance
and rich protozoan and metazoan life. In this study, we identified „live‟ protists and other
organisms based on Rose-Bengal staining. At the same time we have done direct observations
of “alive” bottom fauna using microscopy on board the research vessel. We registered in situ
active indigenous fauna of some forms of benthic ciliates, hydroids and nematodes in the
hypoxic and anoxic/hydrogen sulfide conditions of the depths region 150- 300 m.
Altogether, these results confirm our earlier conclusion about a possible adaptation of some
benthos forms to hypoxia/anoxia and the hydrogen sulfide environment. Our data suggest that
some of the organisms (gromiids, allogromiids, hydrozoa, nematodes, polychaetes) have
indeed adapted to live under hypoxic/anoxic and sulfidic conditions in the Black Sea. This
fauna is indigenous, rather than having been transported from adjacent oxygenated areas.
IBSS studied sediment cores in the Near-Bosporus region with the depth range 75 – 300 m
depths during cruise RV Arar (November 2009) and RV Maria S. Merian (April-May 2010)
(Fig.3.13).
35
A B
Fig.3.13. Station data at Istanbul Strait‟s (Bosporus) outlet area of the Black Sea
(A- cruse R/V Arar, November 2009, B-cruise R/V M.S. Merian, April-May 2010)
Main groups of macrobenthos taken from multiple-corer samples at the Bosporus Strait were
crustaceans, annelids, bivalves and echinodermates in November of 2009 (Fig.3.14).
Macrobenthos is represented till 250m depth. Low boundary of habitat of Crustacea was at
103m, Bivalves and Echinodermates was 123m. Annelides and Gastropoda were found to
250m depth. Polychaete Vigtorniella zaikai forms accumulates the depth of 250 m in the
Near-Bosporus region, thought, its peaks are at the depths of 150 – 170 m, in the belt of
oxygen to the hydrogen sulphide zone transition, in the sea northern half.
Fig.3.14. Main macrobenthos groups abundance correlation at the depth of 75 m in the Bosporus
region (November 2009)
The data obtained showed, that the main macrobenthos groups change in the Bosporus region,
depending on the bathymetric gradients (Fig.3.15).
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
ind/m
2
Crustacea Annelida Bivalvia Echinodermata
36
Fig.3.15. Main macrobenthos groups quantity according to the groups in the Bosporus region
(November 2009)
Taxonomical structure of meiobenthos is very diverse and was presented by 6–21 higher
taxons depending on depth gradient (Fig.3.16). The main share of the total quantity falls on
nematode group, and harpacticoids are the following.
Fig.3.16. Taxa richness of meiobenthos along depth gradient at the Bosporus Strait (November 2009).
The meiobenthos abundance changes ranges from 9 - 1.900 (103
*indiv*m-2
) along observed
depths in the Bosporus Strait. Total quantity is the highest at the depth of 75 m (1861.6 thous.
smpl/m2). It becomes lower, with the depth increase, forming the smaller peaks at the depths
of 88 m (1011 thous. indiv. m-2
), 162 m (468.5 thous. indiv. m-2
) and 250 m (603.2 thous.
indiv. m-2
). The lowest abundance peak is at the depth of 250 m and meiobenthos quantity
decreases considerably at the depth of 300 m.
Peaks of meiobenthos abundances were located at 75, 88, 103, 160, 250 m water depth,
decreasing with increasing water depth from 75 to 300 m (Fig.3.17). The abundance of
8
9
10
11
12
13
14
15
16
17
18
75 82 88 103 122 160 190 250 300
Taxa
rich
ness
depth (m)
37
meiobenthos ranged from 9 - 1.900 (103
*indiv*m-2
) and the meiobenthos structure is
dominated by eumeiobenthos. Pseudomeiobenthos (temporary meiofauna) abundance was
elevated at 103 m water depth with the highest abundances of Turbellaria and Bivalvia taxa
and at 250 m water depth, where Oligochaeta, Polychaeta and Turbellaria taxa dominated.
Fig.3.17. Distribution of meiobenthos abundance (N) along the water depth gradient.
The changes of abundance of benthic organisms depend on the oxygen content of the bottom
sediments. The distribution of different taxonomic groups of meiobenthos along different
water depths between 75 and 300 m were shown as patchy (Fig.3.18 and Fig.3.19). Such
distribution could provide the evidence of existence meiofauna who have differ adaptation to
the oxygen depletion and anoxia.
A B
Fig.3.18. Changes in the Protozoa abundance along depth gradient of the Istanbul Strait‟s (Bosporus)
outlet area of the Black Sea: A- Gromiida, B - Ciliophora
38
A B C
Fig.3.19. Changes in the Metazoa abundance along depth gradient of the Istanbul Strait‟s (Bosporus)
outlet area of the Black Sea: A- Nematoda, B - Harpacticoida, C – Polychaeta
Thus meiobenthos had distributed of the Istanbul Strait‟s (Bosporus) outlet area of the Black
Sea at depths range from 75 to 300m. The maximum of meiobenthos density is located in at a
depth of 75 m, other peaks occur on the 88, 103, 160, 250 m. At a depth of 300 m amount of
the meiobenthos was significantly reduced, while the importance of such groups as the
Ciliophora and Nematoda increased relatively. Species identification of meiofauna is still in
progress.
During RV Maria S. Merian‟ scientific cruise the data of taxonomic composition and
meiobenthos abundance from Bosporus Strait area were obtained. Comparative analysis of
meiofauna densities had shown the patchiness of meiobenthos distribution along the depth
transects (Fig.3.20 and Fig.3.21).
Fig.3.20. Meiobenthos abundance (N) along depth gradient of the Bosporus Strait area of the Black
Sea. Data from two cruises RV Arar (blue points) (November, 2009), RV Maria S. Merian (red points)
(April,2010)
39
Fig.3.21. Meiobenthos taxa richness along depth gradient of the Bosporus Strait area of the Black Sea
RV Maria S. Merian (April, 2010)
Indicator species: Twenty-nine Harpacticoida species belonging to 20 genera and 7 families
were registered at the depth range 75-250 m in November 2009. Species distribution was
varied with depth. Maximum number of species was registered at the 85 m depth. Two
species - Ectinosoma melaniceps and Haloschizophera pontarchis were dominating
Harpacticoida taxocen by their abundances. The first one is eurybathic, epibenthic species
burrowing through the sediment up to 4 cm depth while the second one typically occurs in
muddy-sandy sediments. Before Haloschizophera pontarchis was found as dominant species
at the depth range 40 – 125 m near the Crimea cost of Black Sea.
At the 1 -2 cm sediment layer three typical deep-water species – Bulbamphiascus imus,
Typhlamhiascus confuses, Proameira simplex were found as dominant at the 75 and 85 m
depth. Two muddy-sandy species – Enhydrosoma gariensis and Normanella mucronata also
were formed the high abundant assemblages. Common species for biocenosis of phaseolina
mud at Crimea shelf - the Cletodes tenuipes was represented by high density at the 103 m
depth.
Polychaete Vigtorniella zaikai was formed well-developed assemblages at the depth of 250 m
in the Near-Bosporus region, thought, its maximum peaks are at the depths of 150 – 170 m, in
the belt of oxygen to the hydrogen sulfide zone transition, in the northern sea part.
Dnepr Canyon (Paleo-Delta): During cruise RV M.S. Merian meiobenthic samples were
collected at two water areas (I & II) (Fig.3.22).
40
Fig.3.22. Meiobenthos samples stations in the Crimea area, the Back Sea (RV Merian, May 2010).
The analysis of the benthos distribution is still in progress. Here we are presenting the results
about change of taxonomic structure and abundance benthos in north-western part of Black
Sea. These are marked the high abundance and taxa richness distinctions of benthos
communities along the depth gradient. Taxonomical structure of meiobenthos is very diverse
and was presented by 6–21 higher level taxons (type, class, order) depending on depth
gradient. The stations of two sampling areas (I, II) were grouped by total meiofauna densities
into three divisions of depth ranges in 75-85, 95-145 and 145-375 m. The benthic fauna
(macro- and meiofauna) densities were calculated by number of all organisms founding in the
sediment corers taken by multicorers and pushcorers (Fig.3.23). Benthos was registered at all
depth range from 75 to 375m. Benthos densities were found higher at the 95-145m depth.
Eumeiobenthos was dominant at two areas, contributing high share of the total meiobenthos
abundance.
41
Fig. 2.23. Distribution of total zoobenthos (macro- and meiofauna) at Crimea shelf along depth
gradient
Fig.3.24. Rank of high meiobenthic taxa from different depth ranges.
Maximum total zoobenthos densities of 2489704 ind./m2
were registered at the 95-105 m,
minimum density of 13475 ind./m2 at the 205-215m depth, respectively. Dominant group at
all depth was Nematoda. Harpacticoida, Foraminifera, Bivalvia were found as subdominant
groups depends on depth range (Fig.3.24 and Fig.3.25).
Indicator species: Polychaete Vigtorniella zaikai was formed assemblages at the depth of 124-
175m in Crimea shelf, thought, its maximum peaks are at the depths of 135 – 163 m, in the
belt of oxygen to the hydrogen sulfide zone transition, in the north-western sea part. This
species was suggested to be an indicator hypoxia in water column and bottom sediments at all
regions of the Black Sea.
Total zoobenthos density
0,00E+00
5,00E+05
1,00E+06
1,50E+06
2,00E+06
2,50E+06
75
-85
95
-10
5
11
5-1
25
12
5-1
35
13
5-1
45
14
5-1
55
15
5-1
65
16
5-1
75
19
5-2
05
20
5-2
15
37
5
Depth range, m
De
nsity, in
d./
m2
42
Fig.3.25. Contribution of meibenthos main taxa at the different depth ranges
References
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Foraminifera Other
43
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3.2. Benthic foraminifera studies in the Greek Lagoons (UPAT)
Benthic foraminifera analysis in two sediment cores (st13 and st15) in Amvrakikos Gulf was
carried out using standard micropaleontological methods (Fig.3.26). Twenty-five samples
were analyzed from the 30cm long Core St13 and twenty-eight from the 42cm-long Core
St15.
Although the resolution of the sediment sampling is still low, preliminary results show that
benthic foraminifera assemblages exhibit changes in relation to the decline of oxygen
availability at the sea bottom of the gulf (Fig.3.27). The onset of the interval of low oxygen
availability is marked in the core sediments by lithological changes and a decrease in the
benthic foraminifera diversity. Shallow infauna species dominate together with agglutinated
foraminifera. The abundance of epifauna species shows a gradual decrease. When the sea
bottom is characterized by minimum oxygen values, the benthic diversity is the lowest. Then
deep infauna species are dominant.
The sea bottom oxygen recovery is characterized by an increase of benthic diversity. Epifauna
and shallow infauna species replace the previous microfauna. Many of the benthic species
obtained at the onset of the low-oxygen interval are observed also at this stage. This pattern
seems to characterize the top black organic layer of the short and long sediment cores
analyzed
46
Furthermore a similar trend has also been obtained in the sediments of the long core at
sediment depths 110-115cm.
Fig.3.26. Map of Amvrakikos Gulf showing the location of sediment cores st 13 and st15.
Fig.3.27. Downcore variability of micropalaeontological parameters in sediment Core st 13
collected from Amvrakikos Gulf.