DIVA 1 & 2 workshop Ferrol SpainDIVA 1 & 2 workshop Ferrol Spain

DIVA 1 & 2 workshop, Ferrol, Spain

Twenty-five participants from Spain and Germany gathered in Ferrol to discuss results based on material collected during the first two DIVA expeditions to the southeastern Atlantic Ocean in 2000 and 2005, and to make plans for the expeditions DIVA-3 to the Argentine Basin (southeastern Atlantic Ocean) and DIVA-4 to a basin in the northern Atlantic. Seventeen oral presentations and eleven posters gave an overview of the achievements of the last seven years and provided a base for future plans. Several themes emerged from the presentations which are summarised below.

The project name DIVA stands for “Latitudinal gradients of deep-sea biodiversity in the Atlantic Ocean”, and while biodiversity data were astonishing for many taxa, the concept of latitudinal gradients in biodiversity- greater diversity toward the equator than toward the poles- could not generally be verified for the deep sea, based on the comprehensive data set assembled from DIVA 1 & 2 material. 

Distributional patterns of deep-sea animals are still not well understood. Generally, it seems that distance is not a factor regulating biogeographic distribution in the deep sea. For example, the bacterial diversity of the basins was found to be the highest ever detected in oligotrophic deep-sea sediments, and different abyssal basins harbour different communities which are, however, difficult to define by statistics. Moreover, the communities did not become more different from each other with increasing distance, which means that a factor other than distance influences community structure- sedimentary characteristics may be more important. Interestingly, this phenomenon has also been described from macrofaunal communities in the Southern Ocean. Among the meiofaunal organisms, harpacticoid copepods proved to be highly diverse- during DIVA 1 alone, nearly 700 species of harpacticoids were identified from little more than 2000 specimens!

For Harpacticoida, results from both DIVA expeditions suggest that geographic structures, such as ridges between two basins, does not influence the distribution or occurrence of species. A particular complex of harpacticoid genera (Ceratonotus-Dendropsyllus) was investigated in terms of  distribution, which is apparently worldwide. As for macrofaunal crustaceans, it appears that many isopod species in the Southeast Atlantic deep sea have a wider distribution than hitherto assumed, and that the species turnover in the deep sea is much lower than expected. Some species of isopods seem to be more restricted in their distribution than others in the same genus (Haploniscus). On the other hand, the tanaidaceans seem to be highly endemic to one abyssal basin, but since nearly all species discovered in DIVA material are new to science, this finding may change with more material being analysed. 

While samples taken during a single expedition are necessarily just one frame out of a movie, long-term investigations at the Porcupine Abyssal Plain add a time axis and allow to investigate the dynamics of a deep-sea site. It could be shown that sea cucmbers (genus Amperima) affect meiofaunal distribution in the sediment. A downward movement deeper in the sediment was evident, in response probably both to the impoverishment and reworking of the surface layer and the downward mixing of organic matter in the sediment by larger macro- and megabenthic organisms. 

Data from the Southern Ocean proved interesting in another context as well, the postulated gradient in deep-sea diversity from the equator to the poles. Even molluscs, the organisms providing the original evidence for this paradigm in the northern hemisphere, seem to behave differently in the southern hemisphere, as comparison of data from DIVA and ANDEEP (Weddell Sea) has proven. Several new species of Solenogastres, worm-like molluscs, were presented from abyssal depths and from upper slope depths (project DIVA-Artabria I) in areas adjacent to the abyssal plains sampled during DIVA. 

Deep-sea organisms are also analysed with molecular genetic methods. During the DIVA-2 expedition DNA of over 300 specimens assigned to about 38 species of Desmosomatidae and other related isopod families was extracted. 

Deep-sea taxonomists are used to a high percentage of new species in every sample they analyse, but each program provides its special highlights. For DIVA, one of these highlights is the very large number of new species of Loricifera, a group of meiofaunal animals described in the 1980’s. They may be the third most abundant meiofaunal taxon after harpacticoid copepods and nematodes, and the DIVA-2 material yielded over 1200 specimens of Loricifera representing probably about 120 new species. Stunning details of their intricate and beautiful morphology can be made visible with the confocal-laser-scanning-microscope.The discovery of new families is another very special result of a taxonomic analysis. A new harpacticoid family has been described with more than 30 new species from  DIVA 1 & 2 and NODINAUT samples collected in the southeast Atlantic and central Pacific Oceans, respectively. New families may also have to be established for several amphipods.

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