Little is known of New Guinea's deep benthic communities. In fall 2010, the Museum national d'Histoire naturelle, Institut de Recherche pour le Developpement, and University of Papua New Guinea spearheaded an international three-leg cruise, BioPapua, aimed at exploring the deep waters of eastern Papua New Guinea and its satellite islands. Special attention was given to faunal assemblages associated with sunken wood and decomposing vegetation as well as seamount summits and slopes. In this article, we review the information available on the deep ecosystems of Papua New Guinea and summarize preliminary results of the BioPapua cruise.

BIOPAPUA

The deep-sea part of the ‘Papua Niugini Biodiversity Expedition’ surveyed the deep-sea environments along the coasts of New Guinea Island in the Bismarck Sea, from the Vitiaz Strait to the border between Papua New Guinea (PNG) and Irian Jaya. This expedition was a follow-up of the BIOPAPUA cruise (2010) that gave some of the first insights into the diversity of the deep-sea fauna of the Bismarck and Solomon Seas for environments other than deep-sea hydrothermal vents. The main aims of the cruise were to survey the diversity of the fauna of (i) hard bottoms that are typically found on deep seamounts, (ii) Astrolabe Bay from 200 m to about 1000 m, (iii) the chemosynthetic environments of the deep sea, including cold-seep environments and plant debris. Astrolabe Bay was one of our targets because its topography allows sampling over the complete bathymetric gradient covered by our sampling gear (down to 1000 m depth), and the recent start of nickel refining activities in the bay is a potential threat to its marine fauna for which little reference data are available. Sampling in the bay revealed not only a diversified fauna associated with soft bottoms and plant debris, but also a chemosynthetic fauna typical of coldseep environments (e.g. siboglinid worms and bathymodioline mussels) below the Ramu refinery. Although the refinery activities had officially started just one week before our work in the area, we observed impacts of these activities. Our molecular work indicates that the siboglinid tubeworm species and one of the two mussel species collected below the Ramu refinery have so far only been documented from this location, despite intensive sampling effort. This illustrates the potential destructive effects of human activities in areas where the diversity and uniqueness of deep-sea communities are poorly understood.

BIOPAPUA, MADEEP, PAPUA NIUGINI

The giant bathymodioline mussels from vents have been studied as models to understand the adaptation of organisms to deep-sea chemosynthetic environments. These mussels are closely related to minute mussels associated to organic remains decaying on the deep-sea floor. Whereas biological data accumulate for the giant mussels, the small mussels remain poorly studied. Despite this lack of data for species living on organic remains it has been hypothesized that during evolution, contrary to their relatives from vents or seeps, they did not acquire highly specialized biological features. We aim at testing this hypothesis by providing new biological data for species associated with organic falls. Within Bathymodiolinae a close phylogenetic relationship was revealed between the Bathymodiolus sensu stricto lineage (i.e. "thermophilus'' lineage) which includes exclusively vent and seep species, and a diversified lineage of small mussels, attributed to the genus Idas, that includes mostly species from organic falls. We selected Idas iwaotakii (Habe, 1958) from this latter lineage to analyse population structure and to document biological features. Mitochondrial and nuclear markers reveal a north-south genetic structure at an oceanic scale in the Western Pacific but no structure was revealed at a regional scale or as correlated with the kind of substrate or depth. The morphology of larval shells suggests substantial dispersal abilities. Nutritional features were assessed by examining bacterial diversity coupled by a microscopic analysis of the digestive tract. Molecular data demonstrated the presence of sulphur-oxidizing bacteria resembling those identified in other Bathymodiolinae. In contrast with most Bathymodiolus s.s. species the digestive tract of I. iwaotakii is not reduced. Combining data from literature with the present data shows that most of the important biological features are shared between Bathymodiolus s.s. species and its sister-lineage. However Bathymodiolus s.s. species are ecologically more restricted and also display a lower species richness than Idas species.

AURORA 2007, BIOPAPUA, BOA1, PANGLAO 2005, SALOMON 2, SANTO 2006, TERRASSES

Bathymodiolinae are giant mussels that were discovered at hydrothermal vents and harboring chemosynthetic symbionts. Due to their close phylogenetic relationship with seep species and tiny mussels from organic substrates, it was hypothesized that they gradually evolved from shallow to deeper environments, and specialized in decaying organic remains, then in seeps, and finally colonized deep-sea vents. Here, we present a multigene phylogeny that reveals that most of the genera are polyphyletic and/or paraphyletic. The robustness of the phylogeny allows us to revise the genus-level classification. Organic remains are robustly supported as the ancestral habitat for Bathymodiolinae. However, rather than a single step toward colonization of vents and seeps, recurrent habitat shifts from organic substrates to vents and seeps occurred during evolution, and never the reverse. This new phylogenetic framework challenges the gradualist scenarios from shallow to deep. Mussels from organic remains tolerate a large range of ecological conditions and display a spectacular species diversity contrary to vent mussels, although such habitats are yet underexplored compared to vents and seeps. Overall, our data suggest that for deep-sea mussels, the high specialization to vent habitats provides ecological success in this harsh habitat but also brings the lineage to a kind of evolutionary dead end.

BIOPAPUA