Bryozoa of the Laptev and East Siberian seas: modern research

The new data about bryozoan fauna of the Siberian seas (Laptev Sea and East Siberian Sea) are obtained. 48 species of Bryozoa were identified in the samples, collected in the MMBI RAS expedition (2014) at 50 stations: 45 – in the Laptev Sea and 16 – in the East Siberian Sea. The taxonomic and biogeographic composition, the features of distribution of Bryozoa are analyzed. A comparative analysis of the studies of the end of the 20th century (1986, 1987 and 1993–1998) based on literature data is carried out (Gontar, 1990, 1994, 2004, 2015а,б, 2016). There was a significant increase 60 in the share of boreal-arctic species due to a significant decrease of arctic species (by almost a third), which probably reflects the climate change towards warming , observed at the beginning of the 21st century.

Spatial distribution of Icelus bicornis (Reinhardt, 1840) and Icelus spatula Gilbert & Burke, 1912 in the russian Arctic seas

This article provides data on distribution of two circumpolar species – twohorn sculpin Icelus bicornis and spatulate sculpin Icelus spatula in the Russian Arctic seas (Barents Sea, Kara Sea, Laptev Sea, East Siberian Sea) in the period from 2014 to 2019. The abundance of the twohorn sculpin varied from 2 to 18 ind/km2, and the biomass varied within 0.002–0.089 kg/km2. For the spatulate sculpin, these parameters were 2–21 ind/km2 and 0.002–0.699 kg/km2. The maximum and minimum values of these parameters for Icelus bicornis were recorded in the Laptev Sea, and for Icelus spatula in the East Siberian Sea. Information on the vertical spatial distribution of these species is also given, confirming the information given earlier that the spatulate sculpin occurs at shallower depths in contrast to the twohorn sculpin.

Bioindication of the water salinity dynamics by the microalgae communities in the Lena River Delta, Laptev Sea, Russian Arctic

The Lena River in the Laptev Sea forms a vast delta, one of the largest in the world. The Ust-Lensky State Nature Reserve saves biodiversity on the Lena Delta territory beyond the Arctic Circle, in the zone of continuous permafrost. In recent years, large-scale plans for the development of extractive industries are implemented in this Russian Arctic sector. In this regard, the study of biodiversity and bioindication properties of aquatic organisms in the Lena River estuary area is becoming more and more relevant. This study aims to identify the species composition of microalgae in lotic and lentic water bodies of the Lena River Delta and use their indicator property for water salinity. It was a trace indicator of species distribution over the delta and their dynamics along the delta main watercourses to assess the impact of river waters on the Laptev Sea coastal areas. For this, all previously published materials on algae and chemical composition of the region waters as well as data obtained in recent years for the waters of the lower Lena reach were involved. In total, 700 species considered to 10 phyla were analyzed: Cyanobacteria (83), Euglenozoa (13), Ochrophyta (Chrysophyta, Xanthophyta) (41), Eustigmatophyta (4), Bacillariophyta (297), Miozoa (20), Cryptophyta (3), Rhodophyta (1), Chlorophyta (125), and Charophyta (111). The available materials of the field and reference observations were analyzed using several statistical methods. The study results indicate that hydrological conditions are the main factor regulating the spatial structure of the species composition of the microalgae communities in the Lena River Delta. The distribution of groups of salinity indicators across flowing water bodies reflects the effect of water salinity, and this allows suggesting possible sources of this effect. The mechanism of tracking the distribution of environmental indicators itself is a sensitive method, that reveals even their subtle changes in them; therefore, as an integral method, it can be helpful for further monitoring.

At the Interface of Marine Disciplines: Use of Autonomous Seafloor Equipment for Studies of Biofouling Below the Shallow-Water Zone

Biofouling of artificial substrates is a well-known phenomenon that can negatively impact offshore industry operations as well as data collection in the ocean. Fouling communities worldwide have mostly been studied within the top 50 m of the ocean surface, while biofouling below this depth remains largely underreported. Existing methods used to study biofouling are labor intensive and expensive when applied to the deep sea. Here, we propose a simple and cost-effective modification of traditional methods for studying biofouling by mounting test plates on autonomous seafloor equipment and preserving them in ethanol upon retrieval for transport to the laboratory. This method can greatly advance our understanding of biofouling processes in the deeper ocean, including fouling community biodiversity, recruitment, and seasonality. We present two case studies from the Laptev Sea and the Sea of Okhotsk in support of this method. In the first study, we looked at fouling communities on the surfaces of ocean-bottom seismometers deployed for one year in the 36–350 m depth range. In the second study, we tested metal and plexiglass (poly(methyl methacrylate) plates mounted on autonomous bottom stations and found evidence of both micro- and macrofouling after three months of deployment. Our results demonstrate that various autonomous seafloor equipment can be used as supporting platforms for biofouling studies.

Methane-Derived Authigenic Carbonates on the Seafloor of the Laptev Sea Shelf

Seafloor authigenic carbonate crusts are widespread in various oceanic and marine settings, excluding high-latitude basins that are corrosive to carbonate precipitation. Newly formed carbonate formations are relatively rare in modern Arctic marine sediments. Although the first-order principles of seep carbonate formation are currently quite well constrained, little is known regarding the duration or mode of carbonate formation in the Siberian Arctic shelf. Large (massive slabs or blocks) and small crusts that were micrite cemented have been recently discovered on the seafloor of the Siberian Arctic seas within the area of known seep activity in the outer Laptev Sea shelf. Cold methane seeps were detected in the area due to the presence of an acoustic anomaly in the water column (gas flares). Microbial mats, methane gas bubbles, and carbonate crusts were observed using a towed camera platform. Here, we report new geochemical and mineralogical data on authigenic shallow Siberian Arctic cold-seep carbonate crusts to elucidate its genesis. The Laptev Sea carbonate crusts mainly consist of high-Mg calcite (up to 23 mol % MgCO3). The δ13C values in carbonates range significantly (from –40.1 to –25.9‰ VPDB), while the δ18O values vary in a narrow range (+4.4 ± 0.2‰ VPDB). The δ13C values of Corg that was determined from carbonates range from –40.2 to –31.1‰ VPDB. Using the isotope data and taking into account the geological setting, we consider that not only microbial but possibly thermogenic methane participated in the authigenic carbonate precipitation. Carbonate crust formation occurred below the water/sediment interface of the shallow Siberian Arctic shelf as a result of gas hydrate dissociation during Holocene warming events. The studied carbonate crusts were exhumated after precipitation into shallow subsurface shelf sediments.