Lacydonia shohoensis (Annelida, Lacydoniidae) sp. nov. – a new lacydonid species from deep-sea sunken wood discovered at the Nishi-Shichito Ridge, North-western Pacific Ocean

Lacydonia Marion & Bobretsky, 1875 is the sole genus in the family Lacydoniidae Bergström, 1914. We herein describe the new species of Lacydonia shohoensis sp. nov. from 2042-m deep bottoms at Shoho Seamount of the Nishi-Shichito Ridge, the Northwest Pacific Ocean. It is most similar to L. anapaulae Rizzo et al., 2016 in having a depression on the median anterior region and lacking lateral lobes on the posterior margin of prostomium whereas it is distinguished by possessing pygidium dorsally pigmented with three reddish spots and non-pigmented pygidial lateral cirri equally elongated.

A New Species of Diaphus Associated with Seamounts of the Emperor Chain, North-Western Pacific Ocean (Teleostei: Myctophiformes: Myctophidae)

A new species, Diaphus balanovi, is described based on 35 specimens collected over the Emperor Seamount Chain in the north-western Pacific Ocean. It belongs to the D. fulgens species complex and is most similar to D. kuroshio both morphologically and genetically. Nevertheless, the new species can be distinguished from D. kuroshio by its higher gill-rakers count, large luminous scale at PLO, large Dn, somewhat higher position of SAO3, otolith shape, and larger absolute size. The CO1 mtDNA sequence of D. balanovi differs by 16 substitutions from that of D. kuroshio. Diaphus balanovi may represent a benthopelagic derivate of D. kuroshio endemic to the Emperor Seamounts.

Nutrient ratios driven by vertical stratification regulate phytoplankton community structure in the oligotrophic western Pacific Ocean

The stratification of the upper oligotrophic ocean has a direct impact on biogeochemistry by regulating the components of the upper-ocean environment that are critical to biological productivity, such as light availability for photosynthesis and nutrient supply from the deep ocean. We investigated the spatial distribution pattern and diversity of phytoplankton communities in the western Pacific Ocean (WPO) in the autumn of 2016, 2017, and 2018. Our results showed the phytoplankton community structure mainly consisted of cyanobacteria, diatoms, and dinoflagellates, while the abundance of Chrysophyceae was negligible. Phytoplankton abundance was high from the equatorial region to 10∘ N and decreased with increasing latitude in spatial distribution. Phytoplankton also showed a strong variation in the vertical distribution. The potential influences of physicochemical parameters on phytoplankton abundance were analyzed by a structural equation model (SEM) to determine nutrient ratios driven by vertical stratification to regulate phytoplankton community structure in the typical oligotrophic ocean. Regions with strong vertical stratification were more favorable for cyanobacteria, whereas weak vertical stratification was more conducive to diatoms and dinoflagellates. Our study shows that stratification is a major determinant of phytoplankton community structure and highlights that physical processes in the ocean control phytoplankton community structure by driving the balance of chemical elements, providing a database to better predict models of changes in phytoplankton community structure under future ocean scenarios.

Eddy Around Zhoushan Island: Observations with Synthetic Aperture Radar at C-band

We studied mesoscale (∼100 km length) eddy around the Zhoushan Island (one Sentinel-1 (S-1) image at coastal East China Sea). The simultaneous sea surface temperature (SST) data from the Advanced Very High-Resolution Radiometer (AVHRR) confirms the existence of upwelling in the Western Pacific Ocean, although, the AVHRR data around the Zhoushan Islands were not available. The difference in the root mean square error (RMSE) between the simulations with the Region Ocean Modelling System (ROMS) and that of the AVHRR data was around 1 °C. Also, the RMSE of the model-simulated current speed compared with that of the Climate Forecast System Version 2 (CFSv2) data was 0.04 m/s. We concluded that natural biogenic slicks mainly contributed to damping Bragg waves for sub-mesoscale upwelling, while ocean currents are an important factor affecting the roughness of mesoscale cold eddies.

Integrating Stochastic and Deterministic Process in the Biogeography of N2-Fixing Cyanobacterium Candidatus Atelocyanobacterium Thalassa

UCYN-A is one of the most widespread and important marine diazotrophs. Its unusual distribution in both cold/warm and coastal/oceanic waters challenges current understanding about what drives the biogeography of diazotrophs. This study assessed the community assembly processes of the nitrogen-fixing cyanobacterium UCYN-A, developing a framework of assembly processes underpinning the microbial biogeography and diversity. High-throughput sequencing and a qPCR approach targeting the nifH gene were used to investigate three tropical seas: the Bay of Bengal, the Western Pacific Ocean, and the South China Sea. Based on the neutral community model and two types of null models calculating the β-nearest taxon index and the normalized stochasticity ratio, we found that stochastic assembly processes could explain 66–92% of the community assembly; thus, they exert overwhelming influence on UCYN-A biogeography and diversity. Among the deterministic processes, temperature and coastal/oceanic position appeared to be the principal environmental factors driving UCYN-A diversity. In addition, a close linkage between assembly processes and UCYN-A abundance/diversity/drivers can provide clues for the unusual global distribution of UCYN-A.