BIODEEP (EVK3-2000-00042) First year Scientific Report
Workpackage number 2: DHABs physical, chemical and geological characterisation
Lead contractor: UTRECHT UNIVERSITY
Participants: CoNISMa, UTRECHT UNIVERSITY, UP, NERC
Start date: month 9
3.1 Objectives
The objectives of WP2 are related to the chemical characterisation of the DHABs brines, seawater/brine interface and sediments, so as to determine the most appropriate sampling sites for biological and microbiological workpackages and to the characterisation of the relevant fluxes and the sedimentations rates in studied areas by using sediment traps.
In view of the intensive sampling and processing activity needed for microbiological work on board, and the amount and size of equipment needed (e.g. Modus), it became evident in the planning phase that microbiological and geological/geochemical sampling had to be done on different cruises. Problems during the Pelagia 2001 Cruise (failure in sediment trap recovery), made it impossible to collect new sediment samples. The preliminary sediment sampling was therefore made during the Urania 2001 Cruise but there were no people-time-space on-board for core subsampling.
The microbiological sampling during the Urania cruise was feasible even without prior detailed geological/geochemical sampling and analysis, based on previous experience and expertise of the geology ad geochemistry groups.
3.2 Methodology and scientific achievements
During the Urania 2001 cruise, several bathymetric profiles were acquired for a better definition of the basins’ morphology and for the identification of the most appropriate sites for sediment sampling. During the sampling operations, most of the stations sampled for microbiological investigation were sampled also for geochemical analyses, therefore a preliminary overview of the
DHABs chemistry can be done.
A) Morphology of the DHABs
The bathymetric data collected during the Urania 2001 cruise were assembled to produce new detailed bathymetric maps of the investigated areas. Such maps and 3D plots, containing the position of the sampling sites, are shown in the Cruise report.
35°20’N
35°15’N
Map from MEDRIFF Consortium, in:
Eos, Trans. AGU, 76, 313, 1995
21°30’E 21°40’E
B) Description of the collected samples
Brines.
The table with the list and kind of samples collected during the Urania 2001 Cruise is reported in chapter 10 of the Cruise report.
Sediments. Cores were collected during the Urania 2001 Cruise by means of box- and multicorer.
The figure below shows the locations of the cores in the Anoxic Basin Area; the anoxic core in

BIODEEP (EVK3-2000-00042) First year Scientific Report
Bannock Basin, not shown in the map, was collected in the south-western part of the Basin, the
Libeccio sub-basin, (see also chapter 3 of the Cruise report for core location).
All cores were immediately sub-sampled for microbiological purposes. From most of the stations investigated, one core was stored within its plastic liner, subsequently opened in the laboratories onland ( CoNISMa Milano-Bicocca) and described following the standard procedures, with the
0 identification of the sediment colour and the major and minor lithologies.
Cores BC02 (Discovery Basin) and MCAT04 (L’Atalante Basin) were sub-sampled at 1 cm resolution for trace ( UP ) and major element composition ( UU, SOC ).
Disc overy Basin
BC02
0
L’Atalante Basin
MCAT04
Fluid top
L’Atalante Basin
MCAT02
0
Fluid top
0
Urania Basin
MCURA02
0
Bannoc k Basin
MCBANN02
Cores from inside the
DHABs
10
Blac k mud with gray bands
10 10
Soft aqueous m ud
Color: dark olive gray with gray band
10
Very fluid gray mud
10
Very fluid silty mud
Color: dark olive gray
Very soft aqueous mud
Color: dark olive gray with gray bands
20 20 20
Resedimented layer?
20
Silty mud, pale yellow
20
Gelatinous pellic les
Gray mud
Resedimented layer?
30
Dark gray m ud with nodules
30 30 30 30
Dark olive gray mud
Brown mud with nodules
40
Resedimented layer?
Soft aqueous m ud
Stiff mud, dark olive gray
40 40
Aqueous mud
Color: dark olive gray
Finely laminated
40
50 50 50
Brown mud
Aqueous mud
Darker olive gray layer
LEGENDA
Nodules
Resedim ented layer
Pellic les
60
MCAT01
Fluid pteropod mud
0
Urania Basin Area
BCURA03
Fluid pteropod mud
Disc overy Basin Area
BC01
0
Fluid pteropod mud
Disc overy Basin Area
MC02
0
Fluid pteropod mud
0
Cores from normal oxygenated bottom in the DHABs area
Brown mud
10
20
10
Brown mud
Tephra?
Resedimented layer?
Resedimented layer?
20
Ox. S1
Resedimented layer?
Mn-ric h layer
Ox. S1
S1
Pre-S1
10
20
Brown mud
Pteropod layer
10
20
Brown mud
Pteropod layer
Pteropod layer
Pteropod layer
30 30 30
Mn-ric h layer
Ox. S1
30
Mn-ric h layer
Ox. S1
S1 S1
Resedimented layer?
S1
40 40 40
Pre-S1 Pre-S1
LEGENDA
Planktonic shells
Resedimented layer
Sapropel S1
Pre-S1 layer 50
.
C) Sample analyses
Samples collected for this WP have been distributed to 3 partners for the preliminary assessment of the general sediment composition, and for inter-calibration, including the comparison of methods for high salinity sediments. UP has focused on trace elemental composition, whereas UU and SOC have done major elemental and C,N compositions.
Trace elemental compositions: major findings from analysis of BC02
1. The vertical variability of the elements studied suggests that during the time represented by the sediment layers occurring below 40 cm no significant geochemical variability took place.

BIODEEP (EVK3-2000-00042) First year Scientific Report
2. Above 40 cm important geochemical changes appear, which become more intense towards the present.
3. A decrease of Mn is observed towards the more recent sediments, which would suggest parallel important changes of physicho-chemical conditions towards the present.
4. During the time represented by the 18 – 22 cm layer there has been an important geochemical event, which led to metal enrichments (i.e. Fe, Mn, Co, Ni).
5. The symmetric geochemical anomalies observed at 20 cm suggest a gradual changing in the environmental conditions, including the rate of incorporation of the metals in the sediments.
6. Similar results of another significant geochemical anomaly are recognized at 28-32 cm depth.
7. At 23 cm depth Ca exhibits marked enrichments, whereas Cu, Mn and Ni show depletions.
8. Barium, a known biogenic element, exhibits characteristic peaks at 16 cm and 7 cm depth.
Interestingly at both depths, Ba anomalies have similar asymmetric shape.
Details on trace elemental research of sediment samples are given in the Appendix.
Major elemental and C,N compositions:
Calibration Sediments from the brine basins contain different salt compositions and contents which are 7 to > 15 times seawater values. These high salt contents not only offer a unique and extreme environment for microbiological studies but also present unusual analytical complications for determining the exact water content and the exact geochemical composition. These are important background parameters for all flux calculations, and sediment permeability (solid to liquid ratio in the sediments), and thus are essential elements for understanding microbiological processes.
On the selected sediment samples for each of three different basins, namely Urania, L’Atalante, and
Discovery Basins, we have started to undertake a thorough comparative analytical programme to detect the best possible approach in preparation and analysis of such extreme sediments. This will include not only the drying of a total sample, but also different washing techniques to remove the salt, and the analysis of the sample after such washing. Discovery basin samples appear to be highly hygroscopic, therefore, are likely to result in relatively large analytical uncertainty. We will have a full comparison for all of these results and done by the three partners involved in different geochemical analyses before month 19. This will permit us to come with a recommended approach for preparation of samples so as to assure the best analytical results for our detailed geochemical studies to be done in yr 2 and 3.
Preliminary results Our preliminary results on core BC02 (Discovery basin) suggests that the top 20 cm have been deposited within a brine environment, whereas the sediments below 24 cm had been emplaced during ‘normal’ oxic conditions (Fig. 1). This indicates that brine deposition has started relatively recently, i.e. a few thousands years ago.
Furthermore, the sediment composition of Discovery Basin is heavily influenced by its extremely high salt contents, which severely complicates its proper interpretation. As mentioned earlier, a detailed intercomparison of methods needs to be completed for these sediments, so as to assure the best possible approach for the scheduled detailed geochemical studies associated with the microbiological work.
%C.org
Ti/Al (%/%)
0 0.2
0.4
0.6
0.8
0.052
0.054
0.056
?
Figure 1 . Examples of preliminary concentration versus depth profiles from core BC02 (Discovery basin): a. org.C (UU),
b. CaCO3 (UU),
c. Ti/Al (SOC).
Grey shading indicates transition between upper and lower interval (see text)
0 10 20
% carbonate
30

BIODEEP (EVK3-2000-00042) First year Scientific Report
In sediments from L’Atalante basin there is one deviating sample at 29-30 cm depth, which is likely to indicate volcanic ash.
In view of the extreme influence of sedimentary salt contents on the total sediment composition, the data reported here are preliminary data. Certain elements may require modification/further calibration due to the extremely high salt loading and higher than usual spectral interferences in these uncommon samples of extreme compositions (see Appendix ).
K/Al (%/%) Ti/Al (%/%)
0.4
0.6
0.8
1 1.2
1.4
0.052
0.056
0.06
Figure 2 . Examples of preliminary concentration versus depth profiles from core
MCAT04 (L’Atalante basin): a. Fe/Al (SOC), b. K/Al (SOC), c. Ti/Al (UU).
Note the presence of an ashlayer (?) at 29-30 cm depth.
0.52
0.54
0.56
0.58
0.6
Fe/Al (%/%)
3.3 Socio-economic relevance and policy implication
DHABs of the eastern Mediterranean represent unique sites with peculiar physico-chemical conditions and can host peculiar micro-organisms with possible biotechnological potential. The geological characterisation of these basins and the definition of the geochimical composition of the brines is essential for the understanding of the environment where these organisms live; the geochemical characterisation of the anoxic sediments of the DHABs allows to trace modifications in the DHABs bottom conditions.
3.4 Discussion and conclusion
The milestone to be reached during the I year of the Project was related to the calibration and optimisation of sampling methods and sample analysis procedures. During the first year of the project, much effort has been done on this topic, in particular due to the problems of dealing with high salt content of sediment samples. Moreover, profiles of minor element composition were performed on a sediment core from Discovery Basin.
3.5 Plan and objectives for the next period
The objectives for the next year are related to the new sampling program for the Urania 2002 cruise and to the analysis of the new and already existing samples.
Urania 2002 cruise:
- new attempt to recovery the 2 Urania Basin sediment traps (operations failed during Pelagia 2001
Cruise), provided that they are still at the bottom;
- collection of new brine and sediment samples and pre-processing directly on-board: this is essential in order to obtain reliable data on surface sediment accumulation rates and detailed geochemical analyses at a suitable depth resolution;
- collection of large volumes of water for suspended matter analysis.
Sample analyses will be performed on:
- water samples (Urania 2002)
- brine and sea-water/brine interface (Urania 2002)
- sediment trap samples related to the period 2000-2001 (samples collected during Pelagia 2001 plus the remaining ones, to be collected possibly during Urania 2002)
- sediments and bottom water/sediment interface