Water Assemblages Research Articles

Long-term monitoring dataset of plankton assemblages in western Taiwan coastal water

Plankton plays important roles in the marine ecosystems as important producers for primary production, major components in the global biogeochemical cycles, and the foundation of the marine food web. Despite their importance, long-term monitoring data about marine plankton are fairly limited, especially in the Asia-Pacific region. We fill this knowledge gap by providing a 29-year long-term monitoring data on the coastal areas of western Taiwan quarterly from 1993 to 2021. This long-term monitoring data can be used to set proper baseline for detecting human-induced impacts on the plankton, as well as modelling future scenarios under global changes.

A High-Resolution Digital Bathymetric Elevation Model Derived from ICESat-2 for Adam’s Bridge

This data descriptor elaborates the details of a high-resolution digital bathymetric elevation model generated for the region, namely, Adam’s Bridge, which encompasses a chain of shoals between Rameswaram Island, off the southeastern coast of Tamil Nadu, India, and Mannar Island, off the northwestern coast of Sri Lanka. The proposed dataset has taken advantage of the photon penetrability in the shallow waters by the green laser of ICESat-2 LiDAR to derive the seabed topography. Seafloor depths from ~0.2 million geolocated photons of ICESat-2 for the study area were accrued and interpolated to generate a 10 m digital bathymetric elevation model. Adam’s Bridge, an isthmus and submerged reefal assemblage in shallow and super-shallow waters, is a feature of scientific curiosity. Our dataset has the potential to enhance the understanding of Adam’s Bridge structure by providing substantial information to reconstruct its evolution.

Porewater microbiomes in buried wetland soils: Synergic effects of water chemistry and redox gradients associated with hydrological processes

Abstract Interstitial water or pore water occupies the space between soil particles and provides “hotspots” and “fluvial networks” for microbial activities in floodplain soil. However, to date, we know very little about the microorganisms living in pore water and how they respond to environmental changes. This study aimed to understand microbial distribution and assemblage in riparian pore waters, and how they respond to water chemistry and redox gradients associated with hydrological processes. We analysed the annual changes of porewater microbial communities from the east and west banks of the White Clay Creek, a site at the Christina River Basin – Critical Zone Observatory, Pennsylvania, USA. Microbial abundances were quantified by epifluorescence microscopy and detailed community structures were characterised by high‐throughput sequencing. Water chemistry and redox gradients were also monitored and recorded, and their interactions with porewater microbiomes were analysed using correlations and multivariate analyses. Abundance of microbial cells increased during summer and late autumn. Wetland porewater microbiomes mainly contained Acidobacteria, Bacteroidetes, Nitrospirae and Proteobacteria, and microbiome structures were easily distinguishable from those in the underlying hyporheic gravel layer. Seasonal dynamics of bacterial community structure in the east and west wetlands were distinct, responding to floodplain topography and associated hydrological/geochemical processes. Iron (Fe)‐cycling bacteria (mainly Gallionellaceae and Rhodoferax spp.) dominated the porewater microbiome, and their relative abundance was significantly higher in the east than the west wetland. Furthermore, Fe‐oxidising bacteria (Gallionellaceae) were negatively correlated with Fe‐reducing bacteria (Rhodoferax spp.) at the east wetland. Microbial abundances (cell density) in pore waters showed similar seasonal patterns across stream banks, but microbial community structure did not. Microbiome assembly in pore water is correlated with water chemistry and redox gradients primarily associated with local hydrological processes. As a consequence of their significance for carbon (C) mineralisation and Fe reduction at terrestrial–aquatic interfaces, microbiomes in riparian pore waters and associated microbial activity play an essential role in C and mineral dynamics. These findings will inform future studies of the response of freshwater ecosystems to hydrological dynamics influenced by global climate change.

EDNA metabarcoding reveals biodiversity and depth stratification patterns of dinoflagellate assemblages within the epipelagic zone of the western Coral Sea

BackgroundDinoflagellates play critical roles in the functioning of marine ecosystems but also may pose a hazard to human and ecosystem health by causing harmful algal blooms (HABs). The Coral Sea is a biodiversity hotspot, but its dinoflagellate assemblages in pelagic waters have not been studied by modern sequencing methods. We used metabarcoding of the 18 S rRNA V4 amplicon to assess the diversity and structure of dinoflagellate assemblages throughout the water column to a depth of 150 m at three stations in the Western Coral Sea. Additionally, at one station we compared metabarcoding with morphological methods to optimise identification and detection of dinoflagellates.ResultsStratification of dinoflagellate assemblages was evident in depth-specific relative abundances of taxonomic groups; the greatest difference was between the 5–30 m assemblages and the 130–150 m assemblages. The relative abundance of Dinophyceae (photosynthetic and heterotrophic) decreased with increasing depth, whereas that of Syndiniales (parasitic) increased with increasing depth. The composition of major taxonomic groups was similar among stations. Taxonomic richness and diversity of amplicon sequence variants (ASVs) were similar among depths and stations; however, the abundance of dominant taxa was highest within 0–30 m, and the abundance of rare taxa was highest within 130–150 m, indicating adaptations to specific depth strata. The number of unclassified ASVs at the family and species levels was very high, particularly for Syndinian representatives.ConclusionsDinoflagellate assemblages in open water of the Coral Sea are highly diverse and taxonomically stratified by depth; patterns of relative abundance along the depth gradient reflect environmental factors and ecological processes. Metabarcoding detects more species richness than does traditional microscopical methods of sample analysis, yet the methods are complementary, with morphological analysis revealing additional richness. The large number of unclassified dinoflagellate-ASVs indicates a need for improved taxonomic reference databases and suggests presence of dinoflagellate-crypto and–morphospecies.

Long term variations of fish assemblage in the coastal waters Bukchon-ri, northern part of Jeju Island from 2012 to 2022

Long term variations of fish assemblage in the coastal waters Bukchon-ri, northern part of Jeju Island from 2012 to 2022

Freshwater supply as sociotechnical tinkering: the co-creation of water knowledge and assemblages in New Caledonia

This article aims to show that in-depth ethnography of processes and acts of sociotechnical tinkering provide a useful starting point for understanding how water knowledge co-creation works. This is even more relevant in countries with a strong legacy of settler colonization and continued power asymmetries between holders of different water-related knowledges and ontologies. Analyzing infrastructural and sociotechnical forms of tinkering helps understand how various water assemblages interact with official norms, strategies and laws. Drawing on the study of this tinkering practice, this article looks at how the people of Touho, in New Caledonia, assemble different forms of knowledge to understand, access and drink water.

Metaphyton contributes to open water phytoplankton diversity

In contrast to pelagic and benthic realms of the aquatic ecosystems, studies on the metaphytic habitats remain underrepresented in the literature. However, this realm may have a potential impact on composition and diversity of the open water assemblages through metacommunity processes (source-sink dynamics, mass-effect) especially in small ponds with extended littoral zone. Using a limnocorral experiment we studied how metaphyton affects diversity and composition of open water phytoplankton in a small eutrophic pond in the vegetation period. The three habitats (metaphyton, isolated and non-isolated open water) showed considerable differences in their taxa and functional group composition. Abundance-based diversity measures did not reveal remarkable differences among the assemblages of the three habitats. However, taxonomic and functional richness of the metaphyton and the non-isolated part of the pelagial significantly exceeded that of the limnocorral. Incidence-based similarity index values also showed closer resemblance of the metaphyton and plankton samples compared to that of the limnocorral. In the case of several functional groups, their functional redundancy in the metaphyton exceeded that in the open water areas. These results suggest that the metaphyton provides a refuge for several euplanktic elements that survive in the littoral and occasionally enrich the phytoplankton of the open water areas, representing that a within–lake metacommunity processes shape the composition and functioning of the open water areas in standing waters.

Spatial and Temporal Variations in Autumn Fish Assemblages in the Offshore Waters of the Yangtze Estuary

The offshore waters of the Yangtze Estuary are an important fish habitat, and the large gradient of environmental conditions leads to different fish assemblages. We studied the spatial and temporal variations in fish assemblages and their relationships with environmental factors in the offshore waters of the Yangtze Estuary during the autumns of 2012–2016. The fish assemblage consisted of 64 fish species from 39 families, of which 6 species were dominant. There were significant interannual differences in fish abundance, biomass, and species composition, with the highest abundance and biomass in 2013, the lowest abundance in 2016, and the lowest biomass in 2015. Redundancy analysis revealed that total suspended particles and dissolved oxygen drove interannual variation in fish abundance, biomass, and species composition, and depth drove spatial variation in the fish assemblage. According to the depth, the fish were classified as shallow assemblage and deep assemblage. Understanding the spatial and temporal patterns of fish assemblage in the offshore waters of the Yangtze Estuary is beneficial to the conservation of fish and the sustainable use of fishery resources in the offshore waters of the Yangtze Estuary.

Coastal Fish Fauna in the Cystoseira s.l. Algal Belts: Experiences from the Northern Adriatic Sea

Cystoseira s.l. forests are recognised as important habitats which host diverse coastal fish assemblages. Many fish species use such habitats as feeding, breeding, and nursery grounds. Since the coastal fish community depends on the availability of dense macroalgal belts, the decline of these habitats in the Mediterranean Sea also affects the density of coastal fish species. We studied the coastal fish assemblage in Cystoseira s.l. forests in three consecutive years 2019–2021 in the Gulf of Trieste (Adriatic Sea). Data on coastal fish fauna were collected by visual counts conducted by SCUBA diving. Data on algal cover and habitat types were obtained by recording with a video camera. Similarities and differences in the fish community were analysed in terms of habitat and substrate preferences. A total of 34 species were recorded in Cystoseira forests. The results of the present study show that the different algal cover and associated depth gradient have different effects on the fish assemblage in coastal waters, affecting species composition and abundance. For many species, particularly labrids and sea breams, there is a decreasing temporal trend in frequency of occurrence and density. However, fish community trends can be used as a good “proxy” to evaluate the algal belt status. Our results indicate that rapid conservation and restoration actions are needed to stem the decline of Cystoseira s.l. forests.

Planktonic foraminiferal assemblages reflect warming during two recent mid-latitude marine heatwaves

Under future climate scenarios, ocean temperatures that are presently extreme and qualify as marine heatwaves (MHW) are forecasted to increase in frequency and intensity, but little is known about the impact of these events on one of the most common paleoproxies, planktonic foraminifera. Planktonic foraminifera are globally ubiquitous, shelled marine protists. Their abundances and geochemistry vary with ocean conditions and fossil specimens are commonly used to reconstruct ancient ocean conditions. Planktonic foraminiferal assemblages are known to vary globally with sea surface temperature, primary productivity, and other hydrographic conditions, but have not been studied in the context of mid-latitude MHWs. For this study, the community composition and abundance of planktonic foraminifera were quantified for 2010-2019 along the Newport Hydrographic Line, a long-term monitoring transect at 44.6°N in the Northern California Current (NCC). Samples were obtained from archived plankton tows spanning 46 to 370 km offshore during annual autumn (August – October) cruises. Two MHWs impacted the region during this timeframe: the first during 2014-2016 and a second, shorter duration MHW in 2019. During the 2014-2016 MHW, warm water subtropical and tropical foraminifera species were more prevalent than the typical polar, subpolar, and transitional species common to this region. Cold water species were abundant again after the first MHW dissipated in late 2016. During the second, shorter-duration MHW in 2019, the assemblage consisted of a warm water assemblage but did not include tropical species. The foraminiferal assemblage variability correlated with changes in temperature and salinity in the upper 100 meters and was not correlated with distance offshore or upwelling. These results suggest that fossil foraminiferal assemblages from deep sea sediment cores may provide insight into the magnitude and frequency of past MHWs.

Чужорідні види риб атлантично-середземноморського походження в Азовському морі в межах акваторії України (огляд за останні 50 років)

The article is devoted to alien fish species that have appeared over the past 50 years off the coast of Ukraine in the Sea of Azov. The coastal waters of the Sea of Azov are analysed within the waters of Ukraine from Cape Tarkhan of the Kerch Peninsula to the Kryva Spit in Taganrog Bay with the selection of three areas: the southern part—from Cape Tarkhan to Cape Kazantip; the western part—from Arabatska Bay to the Tonka Strait, including Syvash Bay; the northern part—from the Utlyutsky Estuary to the Kryva Spit. According to generalised data from numerous literature sources, from the time of the publication of the work of K. F. Kessler in 1877 and A. Ostroumov in 1897 to the present time, 53 species of fish from 43 genera and 32 families of Atlantic–Mediterranean origin have been registered in the Sea of Azov. During the same period of time, 37 species from 32 genera and 25 families were recorded in the waters of Ukraine. From this list currently disappeared 4 species from 2 families. Since the 1970s, 6 alien species of Atlantic–Mediterranean origin (or complex) have been found in the waters of the Sea of Azov in Ukraine (11.3% of the total number of species registered in the sea since 1897), belonging to 6 genera of 6 families. At species level, aliens make up 16.2% of the number of representatives of the Atlantic–Mediterranean assemblage in Ukrainian waters, at the genus level—18.7%, and at family level—24.0%. According to ecological groups, 3 species belong to benthic species, 2 to bentho-pelagic species, and 1 to pelagic species. Brief information on these species is given (synonymy, presence of material in the fish collection of the National Museum of Natural History NAS of Ukraine, description, distribution, record localities). A table is provided with a complete list of species of this assemblage in Ukrainian waters and the entire Sea of Azov. Unlike other areas of the Azov–Black Sea Basin (Crimean waters, north-western part of the Black Sea), where a share of aliens has also occurred constantly and sporadically, all alien species of the Sea of Azov of Atlantic–Mediterranean origin over the past 50 years are random in the area that have entered the sea during intensive advection of saline Black Sea waters through the Kerch Strait.

Temporal and spatial patterns of demersal fish assemblages in the coastal water of Sierra Leone

Information on the temporal and spatial patterns of fish community is key to further understand the functioning of marine ecosystem and protect marine organism resources efficiently. 6 demersal trawl surveys were carried out in the coast water of Sierra Leone during Sep 2019∼May 2021. Obvious temporal and spatial heterogeneity of oceanographic condition were observed in the survey area, the water temperature and salinity were usually higher in dry season and lower in rainy season. A total of 195 species belong to 79 families were identified. Offshore Sciaenid sub-community and Inshore sparid sub-community were the 2 common and major groups identified from 6 surveys, but the composition of dominant species may have changed. Less abundant of some traditional economic species (P. Typ, P. qui, Epinephelus, Arius and Lutjanus) and more abundant of T. myo were caught The Offshore sciaenid sub-community distributed mainly in southeast part or closed to shoreline in north part of survey area. The Inshore sparid sub-community distributed mainly in northwest part. Bottom sediment type (Btype) and depth were the common significant factors for the special pattern of fish community in all surveys. Offshore sciaenid sub-community was always associated with mud substrate and shallow water; Inshore sparid sub-community was associated with sand substrate and most of sites distributed in deeper water. The significant effect of sea surface salinity (SSS) were only observed in Oct, Dec, Jan and May. SSS was filtered as significant environment parameter, may not just base on the effect of salinity on fish community, but SSS was also a better characteristic parameter for monthly fluctuation of oceanographic condition. The increasing fishing activities maybe the one of major disturbance factors to the structure change of fish community. In order to promote the biodiversity conservation, strengthen fishery management based on ecosystem approach and developing sustainable fishery should be advocated.

Water assemblages in hydrosocial territories: Connecting place, space, and time through the cultural-material signification of water in coastal Peru

This article analyzes how smallholders of Subtanjalla, in coastal Peru, conceive irrigation water as a central element and carrier of hydrosocial relations and territories. We base our analysis on an exploration of the local notions of agua nueva and yocle. These two notions bind together time, space, nature and culture into specific understandings of territorial connections and reciprocities. Through these understandings water is much more than H2O. Instead of just representing an economic good or a material input for irrigated agriculture water is seen as a binding element that bridges and brings together the Andean world with that of Subtanjalla in the Peruvian coast. Water is, from this perspective, a lively and always in-the-making composition of humans, non-humans, and more-than-humans in which there is no clear distinction between nature and culture, past and present, object and subject. We argue that water as an assemblage opens up now lines of inquiry into hydrosocial territories and relations across time and space through the departure of a fundamentally relational understandings of water, its use and governance.

Spatio-temporal variations of phytoplankton assemblage in coastal waters of Maharashtra, north-eastern Arabian Sea

Seasonal variations in phytoplankton species and abundance along the coast of Maharashtra from two different locations (Mumbai and Ratnagiri) and depths were investigated during August 2014-May 2017. A total of 84 species of phytoplankton were recorded from the region out of which 67 were diatoms, 16 dinoflagellates and one blue green alga. Seventy-five and 60 species of phytoplankton were recorded from Ratnagiri and Mumbai respectively. Diatoms dominated the phytoplankton community (81.7-93.3%) followed by dinoflagellates (4.7-7.2%) and blue green algae in both locations. Maximum phytoplankton density was recorded during post-monsoon season followed by pre-monsoon and monsoon seasons at Mumbai and Ratnagiri. Highest average phytoplankton cell density recorded was 9.09 x 104 cells l-1 and 4.06 x 104 cells l-1 during post-monsoon season at Ratnagiri and Mumbai respectively. Maximum cell density was observed at 20 m depth from Mumbai and Ratnagiri. Thalassiosira subtilis, Trieres mobiliensis, Skeletonema costatum, Coscinodiscus centralis and Ditylum brightwelli were the most abundant phytoplankton species recorded at Mumbai, whereas Chaetoceros curvisetus, S. costatum, Trichodesmium erythraeum, Chaetoceros lorenzianus and Ditylum brightwelli were abundant in Ratnagiri waters. The blue green alga, T. erythraeum was abundantly recorded during pre-monsoon season. Species diversity index (H’) ranged from 4.72 to 5.52 and was higher during post-monsoon season compared to pre-monsoon and monsoon. Highest phytoplankton diversity was observed at 20 m depth compared to 40 m depth.Keywords: Arabian Sea, Diversity, Mumbai, Phytoplankton, Ratnagiri

A biogeographic assessment of phytoplankton richness and composition in the Andaman Archipelago and the potential links to anthropogenic and environmental impacts: A multivariate approach

We report here a year-round baseline assessment on phytoplankton diversity and abundance from the pristine coastal waters of the Andaman Islands (September 2011–October 2012). A total of 84 phytoplankton species belonging to 47 genera were recorded from the North to South Andaman Islands. The maximum number of phytoplankton diversity (84 species under 47 genera) was recorded during the northeast monsoon (NEM) at a highly urbanized coastal environment like South Andaman Islands, whereas the minimum diversity (53 species under 34 genera) was recorded during the inter-monsoon (IM) period at the less anthropogenic activity sites viz. North and Middle Andaman Islands. All over seasons, the community composition of phytoplankton was mostly dominated by diatoms (45%–87%) followed by dinoflagellates (11%–46%) and blue–green algae (1%–35%). Besides, the abundance of phytoplankton was recorded as a gradual decrease from South Andaman to North Andaman Islands. The Canonical Correspondence Analysis (CCA) revealed the impact of physicochemical variables on phytoplankton assemblages. Thus, the temperature, salinity, and nitrite were the major environmental variables that influenced phytoplankton assemblage and distribution in the coastal waters of the Andaman Islands. The Principal Component Analysis (PCA) showed a strong variability of phytoplankton diversity in the South Andaman Islands (PC1: 32.6–36.2% variance). In addition, the Metric-multidimensional Scaling analysis also showed the gradual species intensity in the South Andaman than the Middle and North Andaman Islands.

Copepods of the off-shore waters of Caribbean Colombian Sea and their response to oceanographic regulators

AbstractSeven oceanographic expeditions were conducted between the years 2013 and 2018 to determine the horizontal and vertical distribution schemes in the epipelagic and mesopelagic copepod community structure of the Caribbean Oceanic ecoregion (CAO) and the oceanographic variables that regulate it. Four indicator species are suggested for the North Equatorial Current and the Caribbean Surface Water (CSW) mass (Clausocalanus furcatus, Oncaea venusta, Temora stylifera and T. turbinate) and two indicator species for deep-water masses such as the Western North Atlantic Central Water (NACW) and the Antarctic Intermediate Water (AAIW) (Mormonilla phasma and Conaea rapax). The copepod assemblage responds to local oceanographic patterns that are regulated (24%) by the variability of dissolved oxygen and temperature in the water column. The horizontal structure of the copepod assemblage in offshore waters presented a spatial sectorization. Three zones were differentiated: (1) oceanic Colombian zone; (2) influence of the Magdalena River zone; and (3) offshore north-east zone. Water mass mixing processes and migration mechanisms favour the homogeneity of the vertical assemblage of copepods in the CAO ecoregion. This study provides relevant information on the structure and density of copepod species, providing key information to describe the ecological processes and the different responses to the oceanographic factors that modulate them.

Multiple Ecological Parameters Affect Living Benthic Foraminifera in the River-Influenced West-Central Bay of Bengal

The huge riverine influx and associated processes decrease the ambient salinity, stratify the water column, modulate the oxygen-deficient zone, and are also responsible for the recent acidification in the Bay of Bengal. Here, we have studied the effect of these riverine influx-dominated ecological parameters on living benthic foraminifera in the west-central Bay of Bengal. We report that the pH below 7.6 in front of the Krishna river, reduces the diversity and the richness of living benthic foraminifera on the adjacent shelf and the slope. A similar decreased diversity and richness is also observed in front of the Godavari River. We delineate three prominent assemblages, representing different depth zones with associated distinct physico-chemical conditions. The shallow water assemblage (∼27–100 m) is represented by Nonionella labradorica, Hanzawaia nipponica, Brizalina dilatata, Ammonia tepida, and Nonionella limbato-striata. These species are adapted to relatively warmer temperatures and more oxygenated waters. The deepwater assemblage (∼1,940–2,494 m) includes Bulimina cf. delreyensis, Bulimina marginata, Hormosinella guttifera, Cassidulina laevigata, and Gyroidinoides subzelandica and can tolerate a relatively colder temperature. The intermediate-depth assemblage (∼145–1,500 m) dominated by Eubuliminella exilis, Bolivinellina earlandi, Fursenkoina spinosa, Bolivinellina lucidopunctata, Globobulimina globosa, Fursenkoina spinosa, Eubuliminella cassandrae, Uvigerina peregrina, Rotaliatinopsis semiinvoluta, and Cassidulina laevigata, represents oxygen-deficient and organic carbon-rich environment. Besides the pH, temperature, dissolved oxygen and organic matter, we also report a strong influence of bathymetry, coarse fraction (CF) and the type of organic matter on a few living benthic foraminifera. The ecological preferences of 40 such dominant living benthic foraminifera, each representing a specific environment, have also been reported for site-specific proxy. We conclude that although the huge riverine influx affects living benthic foraminifera on the shelf, the dissolved oxygen and organic carbon mostly control benthic foraminiferal distribution in the deeper west-central Bay of Bengal.

Paleoceanographic insights on meridional ventilation variations in the Japan Sea since the Last Glacial Maximum: A radiolarian assemblage perspective

The Japan Sea is ideal for investigating deep water formation due to its unique topography and hydrography. However, because of the scarcity of reliable indicator and high-resolution ventilation records, the driving mechanisms behind ventilation changes in the entire Japan Sea since the Last Glacial Maximum (LGM) remain elusive. In this study, we analyze the radiolarian assemblage in three sediment cores from the southwestern, central, and northwestern Japan Sea to reveal ventilation variations over the last 25 ka. Our results suggest that weak ventilation was a widespread phenomenon in the Japan Sea during the LGM. This is inferred by the low relative abundances of species belonging into the Japan Sea Proper Water (JSPW) Assemblage, which are indicative of deep water ventilation in the Japan Sea. The JSPW Assemblage have gradually become the predominant species in studied cores from the last deglaciation to the early Holocene, suggesting an abrupt transition from oxygen poorer to oxygen richer conditions. All investigated regions show re-ventilation during the deglaciation, albeit at different times. The JSPW ventilation in the central Japan Sea started during the 19 ka Melt-water Pulse (MWP) and remained in an interglacial mode after MWP-1A (~14.7 ka), presumably due to the opening of the Tsushima Strait and intrusion of the Tsushima Warm Current (TWC). An abrupt increase in productive shallow water export during the Bølling-Allerød (B/A) was likely the key factor causing poorly oxygenated deep-water conditions in the southwestern Japan Sea. In contrast, the weakening ventilation in the northwestern Japan Sea during the B/A and Younger Dryas was probably caused by the blocking effect of the sea ice.

Thanatocoenoses of mollusc shells in the north-western part of the Black Sea

Following death, mollusc shells become elements of thanatocoenoses of bottom and coastal deposits. At the early stages of succession of storm strands, the conservation of mollusc shells in the coastal deposits is high, which allows to obtain a larger number of shells to determine their traits. The probability of finding shells of rare mollusc species in the coastal strands is significantly higher than in bottom grab samples. Therefore, the taxonomic composition of the thanatocoenoses may correspond to the actual composition of mollusc assemblage in the adjacent coastal waters. Determination of the maximum age of molluscs from coastal emissions by sclerochronological methods can be more accurate characteristics of the lifespan of the considered mollusc species. Wind waves are one of the hydrodynamic processes influencing the formation of coastal emissions. The maximum wave activity in the coastal zone of the sea contributes to an increase in the deposition of storm emissions in the coastal zone. Studies of thanatocoenoses of marine molluscs in storm emissions in the north-western part of the Black Sea were carried out at three test sites, differing in the degree of wave load on the coastal zone. Analysis of coastal emissions in different parts of the coastal zone — various distance from the water's edge—allows us to determine the frequency and power of wave activity, as well as to identify the dominant species of macrozoobenthos in each area. The composition and quantitative characteristics of storm emissions created by wave activity of various intensities demonstrates the relationship between benthic biocoenoses of molluscs and thanatocoenoses of the coastal zone. The dominance of bivalve mollusc shells in emissions corresponds to the ruling species of molluscs in benthic biocoenoses. Shells of molluscs of the family Mytilidae were dominant in coastal emissions of the analysed areas. The maximum concentration of aquatic organisms is presented in emissions located near the edge of seawater. A dependence between the total mass of biogenic components in coastal sediments and different distances from the water edge has been revealed for the north-western part of the Black Sea.

Northward Migration of Antarctic Polar Front during the Quaternary: Planktic Foraminiferal Record from Southeast Indian Ocean

The ODP Hole 763A is influenced by the northward-flowing cold West Australian Current (WAC) and Southward flowing warm Leeuwin Current (LC). LC is a branch of the South Equatorial Current (SEC), which brings relatively warmer waters from the tropical Pacific Ocean into the Indian Ocean via Indonesian Throughflow (ITF). The modern planktic foraminiferal fauna thrives along the western margin of Australia. It consists mainly of warm water assemblages brought by the LC. The present study provides planktic foraminiferal census data from ODP Hole 763A, influenced by the LC and WAC, to document the history of cold water influence at the site during the quaternary. The northward migration of the Antarctic Polar Front (APF) and resultant intensification of the cold West Australian Current have been inferred based on the dramatic increase in the relative abundance of temperate water species group Globoconella at Hole 763A situated in the low latitude region. The Quaternary planktic foraminiferal census data shows several episodes of invasion of Globoconella. These intervals of high abundance of Globoconella group have been attributed to the intensification of WAC, probably due to Antarctic ice volume expansion and resultant northward migration of the APF at 0.05 Ma, 0.2 Ma, 0.45 Ma, 0.7 Ma and 1.2 Ma. We have documented that the amplitude of fluctuations in cold/warm events has increased after the Mid-Pleistocene Transition (MPT). LC is a heat supplier to the higher latitudes, its weakening during such intervals might have contributed to the ice volume expansion over Antarctica. Thus, the study proposes that the Antarctic ice cap formation creates a positive feedback mechanism by lowering sea level, reduced strength of LC due to a decrease in ITF and less heat supply towards the South Pole. All these phenomena add to further cooling.