Planktonic protist diversity across contrasting Subtropical and Subantarctic waters of the southwest Pacific

Planktonic protists are an essential component of marine pelagic ecosystems where they mediate important trophic and biogeochemical functions. Although these functions are largely influenced by their taxonomic affiliation, the composition and spatial variability of planktonic protist communities remain poorly characterized in vast areas of the ocean. Here, we investigated the diversity of these communities in contrasting oceanographic conditions of the southwest Pacific sector (33-58 S) using DNA metabarcoding of the 18S rRNA. Seawater samples collected during twelve cruises (n = 482, 0-2000 m) conducted east of New Zealand were used to characterize protist communities in subtropical (STW) and subantarctic (SAW) water masses and the subtropical front (STF) that separates them. Diversity decreased with latitude and temperature but tended to be lowest in the STF. Sample ordination resulting from the abundance of amplicon single variants (ASVs) corresponded to the different water masses. Overall, Dinophyceae (34% of standardized total reads) and Chlorophyta (27%) co-dominated the euphotic zone, but their relative abundance and composition at class and lower taxonomic levels varied consistently between water masses. Among Chlorophyta, several picoplanktonic algae species of the Mamiellophyceae class including Ostreococcus lucimarinus dominated in STW, while the Chloropicophyceae species Chloroparvula pacifica was most abundant in SAW. Bacillariophyta (7%), Prymnesiophyceae (5%), and Pelagophyceae (3%) classes were less abundant but showed analogous water mass specificity at class and finer taxonomic levels. Protist community composition in the STFZ had mixed characteristics and showed regional differences with the southern STF (50 S) having more resemblance with subantarctic communities than the STF over the Chatham Rise region (42-44 S). Below the euphotic zone, Radiolaria sequences dominated the dataset (52%) followed by Dinophyceae (27%) and other heterotrophic groups like Marine Stramenopiles and ciliates (3%). Among Radiolaria, several unidentified ASVs assigned to Spumellarida were most abundant, but showed significantly different distribution between STW and SAW highlighting the need to further.

On the Challenge of Plastic Wastes and Litter in Oceans: Some Policy Reflections

The increasing pollution in oceans, especially of the plastics litter, has degraded health of the oceans in many parts of the world. As plastic degrade very slowly, its accumulation in oceans expected to rise exponentially in coming decades and critically affect marine ecosystems, ocean fauna and humans. Microplastics, generated due to mechanical breakdown of plastic waste, is particularly affecting the pelagic ecosystems and can even alter them. It is necessary to generate and update scientific knowledge about production, transport, sink of plastics and their impacts, develop innovative approaches to manage plastic waste, and bringing awareness about effects of plastic pollution to communities. The issue of plastic pollution needs be tackled at local as well as regional levels through effective policy and multi-national cooperation.

Middle-Late Paleozoic conodont ecogeochemistry: an overview

The ecogeochemistry is the application of geochemical features to study animal ecology. This approach is promising for using in reconstructions of ancient pelagic ecosystems. Among other Paleozoic fossils of pelagic animals, remains of conodonts are the most suitable for ecogeochemical investigations. The article reviews ecogeochemical applications of Middle to Late Paleozoic conodont elements. The following features are considered as the most informative: calcium isotopic composition and element ratios (e.g. Sr/Ca) of conodont apatite, and isotopic composition of carbon of conodont elements. These parameters allow us supposing ecological specialization of conodont species, and temporal and spatial dynamics of the ecogeochemistry of conodonts can be used to reconstruct transformations of ancient pelagic ecosystems.

FEATURES OF FORMATION OF THE WINTER PLANKTON COMMUNITIES IN THE NEFTEGAVAN (“OIL HARBOUR”) - MAKHACHKALA AREA OF THE MIDDLE COASTAL CASPIAN

Made has been the analysis of the pelagic ecosystems state in the Western coastal waters of the Middle Caspian in winter period of 2020 in the Neftegavan area, Seaport of Makhachkala. The taxonomic composition of phytoplankton and zooplankton communities, and the density of hydrobionts inhabiting them have been determined. It is noted that in phytocenoses during mass blossom of Rhizosolenia calcar avis (Schultze,1843) the diatom water plants (Bacillariophyta) dominated, and in zooplankton communities the paddle-footed crustaceans, mainly acarcidis ( Acartai tonsa Dana,1843) dominated on abundance. All sampling stations were characterized by a high degree of similarity of phyto-zooplankton in taxonomic composition but they differed significantly in number and biomass.

Implication of single year seasonal sampling to genetic diversity fluctuation that coordinates with oceanographic dynamics in torpedo scads near Taiwan

Many fisheries management and conservation plans are based on the genetic structure of organisms in pelagic ecosystems; however, these structures tend to vary over time, particularly in cyclic ocean currents. We performed genetic analyses on the populations of the pelagic fish, Megalaspis cordyla (Osteichthyes: Carangidae) in the area surrounding Taiwan during 2000–2001. Genotyping was performed on M. cordyla collected seasonally around Taiwan as well as specimens collected from Singapore (Malacca strait) and Indonesia (Banda Sea). Gonadosomatic indices (GSI) revealed that M. cordyla does not spawn near Taiwan. Data related to the mitochondrial control region revealed that the samples from Singapore and Indonesia represented two distinct genetic cohorts. Genotyping revealed that during the summer (June–August 2000), the Indonesian variant was dominant in eastern Taiwan (presumably following the Kuroshio Current) and in the Penghu region (following the Kuroshio Branch Current). During the same period, the Singapore genotype was dominant along the western coast of Taiwan (presumably following the South China Sea Current); however, the number dropped during the winter (December–February 2001) under the effects of the China Coast Current. Divergence time estimates indicate that the two genetic cohorts split during the last glacial maximum. Despite the fact that these results are based on sampling from a single year, they demonstrate the importance of seasonal sampling in unravelling the genetic diversity in pelagic ecosystems.

Extensive morphological variability in asexually produced planktic foraminifera

Marine protists are integral to the structure and function of pelagic ecosystems and marine carbon cycling, with rhizarian biomass alone accounting for more than half of all mesozooplankton in the oligotrophic oceans. Yet, understanding how their environment shapes diversity within species and across taxa is limited by a paucity of observations of heritability and life history. Here, we present observations of asexual reproduction, morphologic plasticity, and ontogeny in the planktic foraminifer Neogloboquadrina pachyderma in laboratory culture. Our results demonstrate that planktic foraminifera reproduce both sexually and asexually and demonstrate extensive phenotypic plasticity in response to nonheritable factors. These two processes fundamentally explain the rapid spatial and temporal response of even imperceptibly low populations of planktic foraminifera to optimal conditions and the diversity and ubiquity of these species across the range of environmental conditions that occur in the ocean.