No abstract

Abstract. In a changing ocean there is a critical need to understand global biogeochemical cycling, particularly regarding carbon. We have made strides in understanding upper ocean dynamics, but the deep ocean interior (> 1000 m) is still largely unknown, despite representing the overwhelming majority of Earth's biosphere. Here we present a method for estimating deep-pelagic zooplankton biomass on an oceanbasin scale. We have made several new discoveries about the Atlantic, which likely apply to the world ocean. First, multivariate analysis showed that depth and Chl were the basic factors affecting the wet biomass of the main plankton groups. Wet biomass of all major groups was significantly correlated with Chl. Second, zooplankton biomass in the upper bathypelagic domain is higher than expected. Third, the majority of this biomass comprises macroplanktonic shrimps, which have been historically underestimated. These findings, coupled with recent findings of increased global deep-pelagic fish biomass, suggest that the contribution of the deep-ocean pelagic fauna for biogeochemical cycles may be more important than previously thought.

<p><strong>Abstract.</strong> In a changing ocean there is a critical need to understand global biogeochemical cycling, particularly regarding carbon. We have made strides in understanding upper ocean dynamics, but the deep ocean interior (> 1000 m) is still largely unknown, despite representing the overwhelming majority of Earth's biosphere. Here we present a method for estimating deep-pelagic zooplankton biomass on an ocean-basin scale. In so doing we have made several new discoveries about the Atlantic, which likely apply to the World Ocean. First, zooplankton biomass in the upper bathypelagic domain is higher than expected, representing an inverted biomass pyramid. Second, the majority of this biomass comprises macroplanktonic shrimps, which have been historically underestimated. These findings, coupled with recent findings of increased global deep-pelagic fish biomass, revise our perspective on the role of the deep-pelagic fauna in oceanic biogeochemical cycling.</p>

Global climate changes and anthropogenic activity greatly impact Arctic marine biodiversity including phytoplankton which contribute greatly to atmospheric oxygen production. Thus the study of microalgae has rising topicality. Class Mamiellophyceae is an important component of phototrophic picoplankton. To gain more knowledge about Mamiellophyceae distribution and diversity special studies were performed in such remote areas as the Russian Arctic seas. A metabarcoding of pico-sized Mamiellophyceae was undertaken by high-throughput sequencing of the 18S rRNA gene sequence V4 region from samples collected in July–September 2017 in the Barents, Kara and Laptev seas, and in the adjacent waters of the Norwegian Sea. Our study is the first to show that Mamiellophyceae among the summer picoplankton of Russian Arctic seas are diverse and represented by 16 algae species/phylotypes. We discovered a new candidate species of Bathycoccus assigned to a new Bathycoccus clade A—uncultured Bathycoccus Kara 2017. It was found that several Micromonas species can co-exist, with Micromonas polaris dominating north of 72°N. The presence of Ostreococcus tauri, Ostreococcus lucimarinus and Ostreococcus mediterraneus at high latitudes beyond 65°N was documented for the first time, similar to findings for some other taxa. Our results will be important for obtaining a global view of Mamiellophyceae community dynamics.

BackgroundPelagic pteropods Limacina helicina are widespread and can play an important role in the food webs and in biosedimentation in Arctic and Subarctic ecosystems. Previous publications have shown differences in the genetic structure of populations of L. helicina from populations found in the Pacific Ocean and Svalbard area. Currently, there are no data on the genetic structure of L. helicina populations in the seas of the Siberian Arctic. We assessed the genetic structure of L. helicina from the Kara Sea populations and compared them with samples from around Svalbard and the North Pacific.MethodsWe examined genetic differences in L. helicina from three different locations in the Kara Sea via analysis of a fragment of the mitochondrial gene COI. We also compared a subset of samples with L. helicina from previous studies to find connections between populations from the Atlantic and Pacific Oceans.Results65 individual L. helinica from the Kara Sea were sequenced to produce 19 different haplotypes. This is comparable with numbers of haplotypes found in Svalbard and Pacific samples (24 and 25, respectively). Haplotypes from different locations sampled around the Arctic and Subarctic were combined into two different groups: H1 and H2. The H2 includes sequences from the Kara Sea and Svalbard, was present only in the Atlantic sector of the Arctic. The other genetic group, H1, is widespread and found throughout all L. helicina populations. ϕ ST analyses also indicated significant genetic difference between the Atlantic and Pacific regions, but no differences between Svalbard and the Kara Sea.DiscussionThe obtained results support our hypothesis about genetic similarity of L. helicina populations from the Kara Sea and Svalbard: the majority of haplotypes belongs to the haplotype group H2, with the H1 group representing a minority of the haplotypes present. In contrast, in the Canadian Arctic and the Pacific Ocean only haplogroup H1 is found. The negative values of Fu’s Fs indicate directed selection or expansion of the population. The reason for this pattern could be an isolation of the Limacina helicina population during the Pleistocene glaciation and a subsequent rapid expansion of this species after the last glacial maximum.