ALBERT

Description: The Laptev Sea and the East Siberian Sea are remote areas of the Arctic region where detailed data on phytoplankton composition and spatial distribution remain limited. In the context of the ongoing environmental changes (increasing warming and ice melting) and prospective exploration activities (oil and gas production) on the Arctic shelves, understanding of the seasonal and interannual phytoplankton community dynamics is of critical importance. Our study provides new specifying data on species composition of phytoplankton over the vast area of the Laptev Sea shelf and the East Siberian Sea shelf. We found that the outer shelf of the Laptev and East Siberian seas was characterized by typical late spring diatom species (Chaetoceros furcellatus, Chaetoceros diadema, Chaetoceros debilis, Chaetoceros constrictus). On the inner shelf of the Laptev Sea, which is strongly affected by the Lena River water masses, the phytoplankton were characterized by the transition from the summer to an autumn stage of development. Local algal assemblages were composed by mixo- and heterotrophic dinoflagellates (Dinophysis and Protoperidinium genera) together with marine and brackish water-marine diatoms (Thalassiosira hyperborea, Thalassiosira baltica, Thalassiosira gravida, Thalassiosira nordenskioeldii) accompanied by sporadically occurring freshwater riverine planktonic diatom species (Aulacoseira granulata, Aulacoseira italica, Asterionella formosa). These variations in species composition over the Laptev Sea shelf were attributed to differences in the hydrography, marine chemical conditions, and the sea-ice regime.

Description: We collected filtered seawater samples from full water column profiles conducted near the Lena River delta during a winter expedition to the Laptev Sea. The samples were recovered during TRANSDRIFT XX Expedition in March and April 2012 using 2-l-Niskin bottles mounted on a frame equipped with a SBE 19plus CTD profiler (Sea-Bird Electronics Inc.). The dataset includes silicate, phosphate and oxygen concentration data of 28 seawater samples, which provide important information on nutrient sources and cycling in the Laptev Sea.

Description: We collected seawater samples during TRANSDRIFT XXII Expedition in September and October 2014 along with CTD (conductivity, temperature, depth) profiles with a SBE 32 rosette water sampler equipped with 12 Niskin bottles (2.5 L) under ice-free conditions onboard the Russian research vessel RV Viktor Buynitskiy on the entire Laptev Sea shelf and above the shelf slope. The dataset includes nitrate, nitrite, ammonia, total nitrogen, phosphate, silicate and oxygen concentration data, as well as pH and total alkalinity, which provide important information on the geochemical state of the Laptev Sea.

Description: We collected seawater samples during TRANSDRIFT XXI Expedition in August and September 2013 along with CTD (conductivity, temperature, depth) profiles with a SBE 32 rosette water sampler equipped with 12 Niskin bottles (2.5 L) under ice-free conditions onboard the Russian research vessel RV Viktor Buynitskiy on the entire Laptev Sea shelf and above the shelf slope (down to ∼310 m depth). The dataset includes nitrate, nitrite, phosphate, silicate and oxygen concentration data , which provide important information on nutrient sources and cycling in the Laptev Sea.

Description: We determined dissolved stable silicon isotopes along with silicic acid concentrations in geochemically well-characterized seawater samples recovered during the expeditions TRANSDRIFT-XX (TI12, March and April 2012), TRANSDRIFT-XXI (VB13, August and September 2013) and TRANSDRIFT-XXII (VB14, September and October 2014) to the Laptev Sea. During the winter TRANSDRIFT-XX expedition, samples were collected using 2-l-Niskin bottles mounted on a frame at several helicopter stations to the sea ice, while during the summer expeditions TRANSDRIFT-XXI and TRANSDRIFT-XXII the samples were recovered with a carousel water sampler equipped with 12 Niskin bottles (2.5 L) under ice-free conditions onboard the Russian research vessel RV Viktor Buynitskiy on the entire Laptev Sea shelf and above the shelf slope. The dataset includes dissolved stable silicon isotope and silicic acid concentration data, which provide important information on the distribution and biogeochemical cycling of silicon and other nutrients in the Laptev Sea.