Why long term trawled red algae beds off Balearic Islands (western Mediterranean) still persist?

The bottom morphology, the surface sediments and the epibenthic community of two adjacent areas within the fishing ground traditionally known as Pesquera Rica (Balearic Islands) were characterized using multibeam echosounder, van Veen dredge and beam trawl. Red algae beds predominate in both areas, but one has been exploited by trawling since at least 90 years ago, whereas the presence of natural barriers prevents this fishing activity in the other one. Comparisons between the two areas showed a biomass reduction of 46.8 and 39.3% of dominant red algae taxonomic groups Peyssonneliaceae and Corallinophycidae, respectively, in the trawled area (TA). Similarly, both mean abundance and biomass of most groups of fauna were higher in the not trawled area (NTA). N90 biodiversity index showed higher mean values of algae species in NTA than in TA (7.0 and 4.9, respectively), whereas no differences were detected neither for sessile nor for mobile fauna. SIMPER analysis showed that large species of both sessile and mobile epibenthic fauna (e.g. the ascidia Polycarpa mamillaris and the echinoderm Spatangus purpureus, respectively) presented higher abundance and contribution to within area similarity in NTA than in TA. In coincidence, these are the most abundant epibenthic species in the commercial hauls from the Pesquera Rica. The relatively low fishing effort and the gears used, addressed to avoid large catches of algae allowing longer hauls, may explain the subsistence of red algae beds in the Balearic Islands trawl fishing grounds. However, the detrimental effects shown here claim for urgent management measures aiming to preserve these bedsVersión del edito

Influence of the hydrodynamic conditions on the accessibility of Aristeus antennatus and other demersal species to the deep water trawl fishery off the Balearic Islands (western Mediterranean)

Postprint2,655

Structure and dynamics of food webs in the water column on shelf and slope grounds of the western Mediterranean

Benthic–pelagic coupling is an important process connecting species throughout the water column, particularly, in deep-sea systemswhere faunal assemblages can be dense if indirectly sustained by production fromthe above. Through stable isotope analyses, this study explored the sources of production, trophic structure, and benthopelagic coupling in two locations with contrasting oceanographic conditions from the western Mediterranean, in the Balearic (BsB) and the Algerian (AsB) sub-basins. The samples of 89 dominant species (23 decapods, 19 cephalopods, 33 fishes, among the other taxa), inhabiting the hyperbenthic and pelagic domains, from the shelf break (250 m), upper slope (650 m), and middle slope (850 m) were analyzed. Results suggested long food webs of approximately four trophic levels (TrLs) that were sustained by planktonic source material in shallowerwaters and degraded particulate organic matter of planktonic origin in deeperwaters.Most of the collected species (70%) occupied intermediate trophic positions between the 3rd and 4th TrLs. The species δ15Nand δ13C values exhibited a broad range, consistent with the high diversity that might be attributed to the oligotrophic conditions. As the depth increased, stronger segregation occurred between the trophic groups, and spatial differenceswere found among consumers of the two locations. Species in the AsB always had consistently higher δ15N values than in the BsB, which could possibly be attributed to the basal δ15N that was present through the foodweb. Despite the contrasting basin characteristics, a similarly close bentho-pelagic coupling pattern was observed at both locations, except at the deepest ground, especially at the AsB,where themean δ13Cvalues fromthe hyperbenthic and pelagic compartments were more distant. This could be related to the higher degree of reworking of organicmatter in the AsB. Overall, these findings suggested the need for a depth-stratified approach to analyze deep-sea food webs in the study site in future studiesVersión del edito

First results of the athapoc mooring at the ne of Menorca, Western Mediterranean Sea

V Encuentro de la Oceanografía Física (EOF 2018) - V Physical Oceanography Meeting, VI Simposio Internacional de Ciencias del Mar - VI International Symposium of Marine Sciences (ISMS 2018), 20- 22 June 2018, Vigo.-- 1 pageThe deep water thermohaline anomaly, named Western Mediterranean Transition (WMT) (CIESM, 2009) was first observed in winter 2005 (López-Jurado et al. 2005) NE of Menorca, at a deep station (2500 m water depth) sampled on a seasonal basis since 2001, within the RADMED Program (López-Jurado et al. 2015). To improve the knowledge of the evolution of this thermohaline anomaly, an instrumented mooring was deployed in 2015 at the same station during the ATHAPOC Project. This mooring is composed of 5 current meters, 8 CTDs, 8 thermistors and covers most of the water column, allowing for a continuous record of salinity, temperature and currents that characterize the different water masses present in the region, including those that contribute to the anomaly. The mooring also includes 1 turbidity sensor and 2 sediment traps to evaluate the sediment dynamics and the associated particle fluxes. Designed to be operative at least during two years, this contribution presents the preliminary results of the first 9 months of deployment, when 40 days period oscillations are observed from the sea bottom to 400 m below the surfaceThis work is supported by the ATHAPOC Project (CTM2014-54374-R), funded by Plan Nacional I+D+I and by the RADMED Program, funded by the IEOPeer Reviewe