Investigation of Deep-Sea Ecosystems Using Marker Fatty Acids: Sources of Essential Polyunsaturated Fatty Acids in Abyssal Megafauna

Abyssal seafloor ecosystems cover more than 50% of the Earth’s surface. Being formed by mainly heterotrophic organisms, they depend on the flux of particulate organic matter (POM) photosynthetically produced in the surface layer of the ocean. As dead phytoplankton sinks from the euphotic to the abyssal zone, the trophic value of POM and the concentration of essential polyunsaturated fatty acids (PUFA) decrease. This results in pronounced food periodicity and limitations for bottom dwellers. Deep-sea invertebrate seston eaters and surface deposit feeders consume the sinking POM. Other invertebrates utilize different food items that have undergone a trophic upgrade, with PUFA synthesized from saturated and monounsaturated FA. Foraminifera and nematodes can synthesize arachidonic acid (AA), eicosapentaenoic acid (EPA), while some barophylic bacteria produce EPA and/or docosahexaenoic acid. FA analysis of deep-sea invertebrates has shown high levels of PUFA including, in particular, arachidonic acid, bacterial FA, and a vast number of new and uncommon fatty acids such as 21:4(n-7), 22:4(n-8), 23:4(n-9), and 22:5(n-5) characteristic of foraminifera. We suppose that bacteria growing on detritus having a low trophic value provide the first trophic upgrading of organic matter for foraminifera and nematodes. In turn, these metazoans perform the second-stage upgrading for megafauna invertebrates. Deep-sea megafauna, including major members of Echinodermata, Mollusca, and Polychaeta display FA markers characteristic of bacteria, foraminifera, and nematodes and reveal new markers in the food chain.

Amazing Discoveries of Benthic Fauna from the Abyssal Zone of Lake Baikal

Lake Baikal is a natural laboratory for the study of species diversity and evolution, as a unique freshwater ecosystem meeting the all of the main criteria of the World Heritage Convention. However, despite many years of research, the true biodiversity of the lake is clearly insufficiently studied, especially that of deep-water benthic sessile organisms. For the first time, plastic waste was raised from depths of 110 to 190 m of Lake Baikal. The aim of this study was to examine the biological community inhabiting the plastic substrate using morphological and molecular genetic analysis. Fragments of plastic packaging materials were densely populated: bryozoans, leeches and their cocoons, capsules of gastropod eggs, and turbellaria cocoons were found. All the data obtained as a result of an analysis of the nucleotide sequences of the standard bar-coding fragment of the mitochondrial genome turned out to be unique. Our results demonstrate the prospects for conducting comprehensive studies of artificial substrates to determine the true biodiversity of benthos in the abyssal zone of Lake Baikal.

Megafaunal Community Structure From the Abyssal to Hadal Zone in the Yap Trench

Hadal trenches remain one of the unexplored ocean ecosystems due to the challenges of sampling at great depths. It is still unclear how a faunal community changes from the abyssal to the hadal zone, and which environmental variables are the key impacting factors. In this study, nine dives of the Human Occupied Vehicle (HOV) “JIAOLONG” were conducted from abyssal to hadal depths (4,435–6,796 m) in the Yap Trench on the southeastern boundary of the Philippine Sea Plate in the western Pacific, divided into 48,200 m video transects, to describe the megafaunal communities and reveal their relationship with environmental factors. A total of 1,171 megafauna organisms was recorded, 80 morphospecies (msps) from 8 phyla were identified based on the video data, most of which were reported for the first time in the Yap Trench. Arthropoda was the most abundant phylum and Echinodermata was the most diverse phylum of the megafaunal community. The faunal abundance increased with depth, whereas the Shannon diversity index decreased with depth. Cluster analysis suggested seven assemblages, with five abyssal groups, one mixed group, and one hadal dominant group. Although megafaunal communities changed gradually from abyssal zone to hadal zone, both PERMANOVA and PERMDISP analyses revealed that the communities are significantly different between abyssal zone and hadal zone, indicating 6,000 m as the boundary between the two depth zones. Depth, substrate, slope, and latitude were identified as four important environmental factors with significant influence on megafaunal community structure. This study proposed a transition pattern from the abyssal to hadal zone in the Yap Trench, highlighted the importance of habitat heterogeneity in structuring megafaunal community in a hadal trench.

Submergence of the sublittoral-bathyal species into the abyssal zone of the Sea of Japan

The bathymetric ranges of the same deep-sea (2000 m) species in the Sea of Japan and outside it are compared. Among 85 deep-sea species of the Sea of Japan mega- and macrofauna, 25 species are known outside the sea at the depths greater than 2000 m and 45 species are known outside the sea only from the sublittoral and bathyal (2000 m). Remaining 14 species are endemic to the Sea of Japan. The species of the first group, together with eurybathic Sea of Japan endemics (8 species) are classified as pseudoabyssal. The term pseudoabyssal species is used here for eurybathic (sublittoral-abyssal or bathyal-abyssal) species, the distribution of which is restricted to a relatively small area in the abyssal, in present case, to the abyssal within the Sea of Japan. The share of pseudoabyssal species in the abyssal basin of the Sea of Japan (64%) is larger than in any other abyssal region. It is suggested that the large share of pseudoabyssal species is the result of local submergence of the sublittoral-bathyal fauna into the abyssal zone of the Sea of Japan. The abyssal basin of the Sea of Japan is distinguished as a biogeographic province within the abyssal biotic zone.

EXTRACELLULAR BIOFABRICATION OF SILVER AND GOLD NANOPARTICLES: TREASURES FROM THE ABYSSAL ZONE

The synthesis of nanoparticles can be accomplished by physical, chemical and biological strategies. Since this has become an expanding area of research in the field of medical sciences and Technology, owing to its potential applications, the need for eco-friendly, non-toxic and economical methods of synthesis have arisen. Biosynthesis of nanoparticles have become the main field of research as it is time efficient, cost effective, less toxic and has abundant resource. This review emphasizes on the biosynthesis of gold (Au) and silver nanoparticles (AgNPs) using marine sources with special reference to algae, their characterisation and its applications. The characterisation of metal nanoparticles is an essential step and can be carried out by various instruments. The various pharmacological, electrical, pest management, parasitology and medical applications of these marine source induced synthesis of nanoparticles have also been portrayed in this review.Â