Search Results (2)

Polychaeta and Sipuncula are abundant inhabitants of benthic marine habitats and have been increasingly sampled in the Northwest Pacific (NWP). However, polychaete and sipunculan species richness, composition, and distribution patterns still require further investigation, despite previous studies due to increasing deep-sea data flow. Using occurrence records for Polychaeta and Sipuncula from the Ocean Biodiversity Information System (OBIS) and the Global Biodiversity Information Facility (GBIF), we analyzed sampling effort (the number of distribution records), alpha (the number of species per 700,000 km² hexagon cells) and gamma (the number of species per 5° latitudinal band) species diversity, and estimated species richness along latitudinal and bathymetric gradients. The species richness estimations were also correlated with multiple environmental and topographic variables, including depth, temperature, dissolved oxygen, chlorophyll, primary production, phytoplankton, current velocity, light, iron, nitrate, phosphate, silicate, and salinity. The dataset included over 30,000 distribution records belonging to polychaete (31,114 records, 98%) and sipunculan (690 records, 2%) species. Half of the distribution records were reported at a species level. The area around the island of Hainan and South Korea showed the highest alpha species richness (the number of species per 700,000 km² hexagon cell), yet the estimated species richness (ES50) indicated that there might be many unknown, unsampled, or non-digitized species throughout the whole NWP. Correspondingly, most distribution records (sampling effort) and gamma species richness were found between latitudes 20 and 40° and decreased towards higher latitudes. Sipuncula were reported relatively more frequently from the deep sea than Polychaeta (62.8% vs. 12%). Overall, the number of species and records decreased with increasing depth, with a peak at about 5000 m. The alpha species richness had the strongest positive correlations with temperature, chlorophyll, primary production, and phytoplankton concentration. Here, we provide an overview of the species richness and distribution of Polychaeta in comparison with Sipuncula in the NWP, in both shallow and deep environments. This study demonstrates where further sampling efforts are needed to fill our knowledge gaps on annelids’ distribution and diversity along the NWP. This could improve the analyses of the distribution and diversity of annelids to better understand the current environmental drivers of biodiversity, as well as predicting potential future drivers. The outcome of the environmental correlation provides thus valuable knowledge for predicting the future impacts of global warming on potential distribution shifts of annelids into new environments such as the Arctic Sea, possibly resulting in biological invasions. Full article

Rhodolith seabeds are ‘ecosystem engineers’ composed of free-living calcareous red macroalgae, which create extensive marine habitats. This study addressed how depth influenced the structure (size and morphology) of rhodoliths and the abundance of associated floral and faunal epibionts across the Eastern Atlantic Ocean. Sampling was carried out at two sites within five regions (Brittany, Galicia, Madeira, Gran Canaria, and Principe Island), from temperate to tropical, covering a latitudinal gradient of 47°, in three depth strata (shallow, intermediate and deep), according to the rhodolith bathymetrical range in each region. Depth typically affected the rhodolith size at all regions; the largest nodules were found in the intermediate and deep strata, while rhodolith sphericity was larger at the shallow depth strata. Higher biomasses of attached macroalgae (epiphytes) were observed at depths where rhodoliths were larger. The abundance of epifauna was variable across regions and depth strata. In general, the occurrence, structure, and abundance of the associated biota across rhodolith habitats were affected by depth, with local variability (i.e., sites within regions) often displaying a more significant influence than the regional (large-scale) variation. Overall, this study showed that the rhodolith morphology and associated epibionts (flora and fauna) were mostly affected by depth, irrespective of latitude. Full article