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    LEVARLEVAR

LEVAR

LEVAR stands for: LEvantine Basin Biodiversity VARiability

 

Project leader: Dr. M. Türkay, Senckenberg Institute, Frankfurt 

 

Study area

The deep waters of the Mediterranean Sea are a very special environment because the water is 13°C warm even in abyssal depths, which is ultimately caused by the very narrow connection of the Mediterranean with the Atlantic Ocean. While in most open oceans the evaporation, for example, near the equator, is neutralised by cold polar waters sinking to the seafloor and then flowing toward the equator, in the Mediterranean there is too little cold deep water coming from the Atlantic, and consequently the water with the highest density is the water with the highest salinity caused by evaporation in the warm sun. LEVAR is designed to find out what the most important factor causing patterns in the diversity of life on the deep-sea floor where consitions are extremely oligotrophic, i.e., there are very little nutrients in the water and in the sediment. An estimate of the relative importance of pelagic production (algae in the surface water, sinking to the bottom as marine snow) versus lateral transport (nutrients in sediments flowing down the slopes into abyssal basins) is the main target of this project. Contributions of pelagic production and lateral transport can be determined by measuring the correlation of benthic diversity with depth and distance from coast.

The first LEVAR expedition took place from 28 December 2006 to 15 January 2007 in the Levantine Basin southeast of Crete. There were two sampling sites, one more than 4,000 m deep and close to the coast, the other shallower (2800 m) but further away from land. The working hypothesis of the scientists was that it is distance from shore rather than depth influencing deep-sea diversity in this part of the world’s oceans. Samples are currently analysed- first results will be published here as soon as they are available.

Microbiology

The main target of the microbiological studies is to investigate the structure and function of bacterial communities under extremely oligotrophic, warm deep sea water in relation to nutrient input into the system. Because of the specific environmental conditions, currently undescribed specialised bacterial communities are to be expected, which must be genetically characterised in detail through cultivation experiments.

Benthic fauna

Nanofauna are unicellular organisms which are, to our current knowledge, much more diverse in the eastern Mediterranean than in other regions of the world ocean. To either reject or confirm observations on extremely wide distribution of several species in the world’s ocean, their potential role in the marine food web as bacterivores is being investigated as well as their population genetics. The analysis of benthic foraminiferan communities will enhance the knowledge on the ecology of these organisms in oligotrophic deep sea regions, not the least in correlation with global climate change.

 

Meio-, Macro- and Megafauna

 

 

 

Information on the abundance and diversity of these size classes- from about half a millimetre to 10’s of centimetres- are compiled and compared with data from other CeDAMar projects, especially those concentrating on deep-sea basins of the southern Atlantic. All working groups will tackle the same questions:

 

· How many species per surface unit (species density) and species per number ofindividiuals (species richness) are present at the individual stations ?

· How large are the differences between the stations and the working areas and which species do they have in common? · How does the species presence change ?

· Which correlations exist between the number of species and environmental factors ?

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