Seafloor heterogeneity influences the biodiversity–ecosystem functioning relationships in the deep sea

Theoretical ecology predicts that heterogeneous habitats allow more species to co-exist in a given area. In the deep sea, biodiversity is positively linked with ecosystem functioning, suggesting that deep-seabed heterogeneity could influence ecosystem functions and the relationships between biodiversity and ecosystem functioning (BEF). To shed light on the BEF relationships in a heterogeneous deep seabed, we investigated variations in meiofaunal biodiversity, biomass and ecosystem efficiency within and among different seabed morphologies (e.g., furrows, erosional troughs, sediment waves and other depositional structures, landslide scars and deposits) in a narrow geo-morphologically articulated sector of the Adriatic Sea. We show that distinct seafloor morphologies are characterized by highly diverse nematode assemblages, whereas areas sharing similar seabed morphologies host similar nematode assemblages. BEF relationships are consistently positive across the entire region, but different seabed morphologies are characterised by different slope coefficients of the relationship. Our results suggest that seafloor heterogeneity, allowing diversified assemblages across different habitats, increases diversity and influence ecosystem processes at the regional scale, and BEF relationships at smaller spatial scales. We conclude that high-resolution seabed mapping and a detailed analysis of the species distribution at the habitat scale are crucial for improving management of goods and services delivered by deep-sea ecosystems.

Report of the striped red mullet (Mullus surmuletus) and red mullet (Mullus barbatus) Exchange 2016

In September 2015, the Working Group on Biological Parameters (WGBIOP) recommended an otolith exchange for Mullus surmuletus and Mullus barbatus in 2016 (Otolith Exchanges proposals for 2016/2017; ICES, 2015). Kélig Mahe (IFREMER, France) was decided to be the responsible to organise this otolith exchange. Two otolith exchanges (2008, 2011), and two age reading workshops (ICES, 2009; 2012), have been taken place until now (Mahé et al., 2012). A total of 13 readers from 5 countries (France, Spain, Italy, Cyprus and Greece) participated at the exchange of 2016. The otoliths of 465 individuals (345 M. barbatus & 120 M. surmuletus), sampled from 2011 to 2014 in the Mediterranean Sea (Central Adriatic Sea, Cyprus, Levantine Spain coasts, Balearic Islands) were used for this exchange. For both Mullus species, the precision values were very low, the PA ranged between 56 and 67% the CV ranged from 32 to 64% and the APE ranged from 1.9 to 3.6%. The results by area and species showed the same trend with the first age groups presenting the higher CV values and in some cases lower PA values. These results could be explained by the position of the first growth increment and the two different approaches of reading interpretation used by the readers (ICES, 2012).