Vol 43, No 3 (2017)

Based on the available literature data, museum collections, and our own material, a review is presented on sipunculan species of the northwestern Pacific that occur at depths greater than 500 m. Brief morphological descriptions showing the main characters used in taxonomy and a key for the identification of deep-sea sipunculans of the northwestern Pacific to species level are proposed. The key includes 22 valid species representing 7 genera and 5 families of Sipuncula.

The morphology of the potentially toxic dinoflagellate Prorocentrum foraminosum was examined in detail using light and scanning electron microscopy for the first time for the seas of Russia. New morphological features of this species were found and documented. Long-term observations showed that P. foraminosum occurred regularly from April to November in the epiphytic assemblages of Peter the Great Bay. The highest cell abundance was recorded in June (1.5 × 10³ cells/g macrophyte dry weight). This dinoflagellate was also found rarely at a low cell densities in coastal sands.

Using the example of three morphologically similar species of the Far Eastern redfins of the genus Tribolodon, it has been shown that an analysis of scale structure allows species identification of not only adults, when they are not in their characteristic spawning dress, but also immature individuals. The most distinct interspecies differences of redfins have been found in the case of the combined use of three basic parameters of scales: lesser diameter, greater diameter, and number of radii. The differences between redfins in the shape and structure of their scales can be explained by the features of ecology of these species, e.g. the velocity of water flow in the breeding grounds and during overwintering in rivers.

In July 2015, the assimilation number (An) of phytoplankton in Amursky Bay was measured using optical dissolved oxygen sensors (Rinko). The primary production (PP) in the photic layer of Amursky Bay was calculated based on the measured An and chlorophyll vertical profiles obtained during a hydrochemical survey on August 23−28, 2008. The total production in the bay at that period was 840 tC/day. During a phytoplankton bloom, the excess production of biomass leading to the hypoxia of the bottom water was estimated to be approximately (1.0−2.0) × 10³ tC/day.

The chemical structures and contents of 68 molecular species of ethanolamine glycerophospholipids (PE), choline glycerophospholipids (PC), serine glycerophospholipids (PS), and inositol glycerophospholipids (PI) were determined in the asymbiotic soft coral Gercemia rubiformis (Ehrenberg, 1834) from the Sea of Okhotsk by the method of tandem high-resolution mass spectrometry. The major molecular species were 16:1e/20:4 PE, 16:0e/20:4 PC, 20:1/24:5 PS, and 16:0/24:5 PI. This study showed a significant similarity of the polar lipidomes of G. rubiformis and tropical species of alcyonarians with symbiotic microalgae and revealed the basic characteristic of the polar lipidome of these alcyonarians. It was found that the 24:5n-6 and 24:6n-3 acids (chemotaxonomic markers of soft corals) concentrate in the acyl groups of the molecular species of PS and PI, which can be used as molecular lipid markers in the study of the symbiotic and trophic relationships of soft corals.

The biology of the Cuvier’s beaked whale, Ziphius cavirostris Cuvier, 1823, in Russian waters remains almost unstudied. The species is encountered rarely elsewhere in the seas of Russia, except for the waters off the Commander Islands. Currently, some researchers express doubt about the accuracy of the known Cuvier’s beaked whale records in the region. This report provides information on the confirmed encounters with Cuvier’s beaked whale off the Commander Islands and eastern Kamchatka.