Shallow Marine Areas Research Articles

Preliminary Study on Floral Distribution, Abundance and Diversity of Mangroves in Vankalai, North-west Coast of Sri Lanka

Sri Lanka harbors a remarkable amount of mangrove habitats. Northern Province shares about 16% of the total mangrove extent of the country. Vankalai consists of several ecosystems which range from arid-zone thorn scrubland, arid-zone pastures and maritime grasslands, sand dunes, mangroves, salt marshes, lagoons, tidal flats, sea-grass beds and shallow marine areas. Due to the integrated nature of shallow wetland and terrestrial coastal habitats, this sanctuary is highly productive, supporting high ecosystem and species diversity. The research was aimed to identify the distribution, abundance and diversity of mangroves in Vankalai of the Northern Province, Sri Lanka. Ten 25m wide belt transects with 10m intervals were randomly arranged in the small patch of mangrove vegetation perpendicular to the 350m of shoreline across the water-land gradient. Each transect was divided into five 5mx5m subplots for convenience of sampling. True mangrove species in each transect were identified and counted. The quantitative data has been used to compute the Shannon diversity index (H), Simpson Index (D) and Shannon Evenness (E), which were used to compare the diversity of the study sites. Ten different mangrove species including Avicennia marina (n=115), Avicennia officinalis (n=73), Rhizophora apiculate (n=33), Rhizophora mucronata (n=102), Sonneratia alba (n=3), Pemphis acidula (n=4), Excoecaria agallocha (n=40), Lumnitzera racemose (n=91), Bruguiera cylindrical (n=97), Ceriops tagal (n=31) were identified and they were belonging to five families; Avicenniaceae (n=2), Rhizophoraceae (n=5), Lythraceae (n=1), Euphorbiaceae (n=1) and Combretaceae (n=1). Further, based on the IUCN status, two mangrove species (Sonneratia alba and Bruguiera cylindrical) were identified as endangered species. The highest Shannon diversity index (H=2.21) and the lowest Simpson index value (D=0.14) were observed in the transects of point 1 due to minimal disturbances. The least Shannon diversity index and evenness were recorded in the point 5 as 1.65 and 0.85 respectively at the point 5 since fishing and tourism activities take place in the proximity of this place. The Shannon diversity index varied at the points of 1 (H=2.21)>2 (H=2.10)>3 (H=1.89)>4 (H=1.84)>5 (H=1.65) whereas Simpson index value were varied at the points of 1 (D=0.14)<2 (D=0.17)<3,4 (D=0.18)<5 (D=0.19) respectively. Pollution and human interaction would have degraded the environmental quality of the mangrove habitats. Based on the observations it was found that the extent of disturbances was minimum at the points of 1 and 2 whereas anthropogenic influence was increased at the points of 3<4<5 respectively. Further, use of mangrove poles and sticks to build fish baits and fishing rods by the anglers could possibly destroy these small patches of mangroves. Hence, actions should be taken for conservation of existing patch and replenishment of new mangroves. 
 Keywords: Mangroves, Diversity, Shannon Diversity Index (H), Simpson Index (D) and Shannon Evenness (E)

A Report on the Artificial Reef Use in Grenada, West Indies

Coral reef rehabilitation in the Caribbean is of major ecological and economic importance in the West Indies. Local organizations in Grenada constructed a cement pyramid artificial reef structure with rugosity (termed “The Pyramid”) and placed a number of these artificial reefs in a shallow marine area fringing two major natural reefs in the southwest coastal region of Grenada. Benthic data for two nearby natural reefs were compared to the benthic evaluation of the artificial reef pyramids. This comparison demonstrated that the artificial reef pyramids were similar in many respects to the natural reefs but were significantly different in macro- and coralline algae cover, two key indicators of reef health. This report is the first benthic evaluation of an artificial reef through comparison to natural reefs in Grenada.

Satellite bathymetry estimation in the optically complex northern Baltic Sea

Satellite bathymetry estimation (SBE) is a cost-effective method for producing depth information for shallow marine and aquatic areas. However, most SBE methods have been developed and are refined in clear water conditions and their feasibility in optically complex waters is poorly understood. This hinders the use of SBE in optically complex waters.To test the feasibility of SBE in optically complex waters, we used multi-temporal Sentinel-2 (S-2) imagery and in-situ measured depth information from dive computers to fit bathymetric models for 14 study areas in the northern Baltic Sea. We compared different methods of using multi-temporal S2-scenes, atmospheric correction, and statistical modeling, as well as different band combinations to define the optimal model for each study area. We tested the dependence of the depth estimation on 13 environmental variables with potential influence on the accuracy of the SBE.The optimal bathymetric models differed among the study sites, with the differences manifested in different requirements for atmospheric correction, band combination, statistical model, and the use of multiple S2-scenes. The coefficients of determination (R2) of the optimal models varied between 0.42 and 0.79, with mean (X) R2 equaling to 0.65. The coefficients of determination were positively related to the proportion of sea within the 5 km search kernel and to the exposure of the study site. At the predicted depth of 2 m, the differences between observed and predicted depths varied between 0.11 and 0.60 m (X = 0.35 m). At the predicted depth of 1 m, the differences varied between 0.04 and 0.34 m (X = 0.21 m).SBE provides accurate depth estimates in optically complex waters, even when in-situ calibration data are limited. However, the maximum detectable depth obtained with SBE in optically complex waters is significantly lower than in clear water conditions. The SBE process can be fine-tuned to the specific characteristics of an area, improving its performance in optically complex conditions. In particular, the identification of the optimal band combination is critical for successful SBE. The depth estimates produced in this study can be used in a variety of applications that require accurate information on the seafloor bathymetry.

Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay

The coupling mechanism between natural and anthropogenic noise in shallow marine areas is of great significance for maintaining the ecological safety of these regions. In this study, a section of Zhanjiang Bay’s entrance was selected as a typical research area, and environmental noise data at different depths were collected during the spring and autumn seasons. The spectral characteristics, sound pressure levels, and underwater noise frequency correlation matrices of environmental noise were analyzed to reveal the underwater noise characteristics of tidal channels in Zhanjiang Bay and their main influencing factors. The results show that underwater noise in this study area had a stable frequency band distribution. In the low-frequency range of 20–50 Hz, the main source of noise was the flow noise influenced by tides and topography, with a peak sound pressure level of approximately 97 dB. In the frequency range of 50 Hz to 500 Hz, the main noise sources were ships at sea, followed by wind-generated noise. At frequencies above 500 Hz, the noise intensity decreased. In addition, it was found that the sound pressure level in the low-frequency range had a significant correlation with the tidal level, increasing with the rise of the tide and decreasing during low tides. This study provides a research case on the impact that human noise activity has on environmental noise in shallow marine bays. These research findings can support the selection of sites and reduce construction noise from offshore wind farms, as well as ensure the acoustic ecological environment in the vicinity of marine ranches.

Late Jurassic rift physiography of the Froan Basin and Frøya High, offshore Mid‐Norway: Development of a syn‐rift shallow marine system

AbstractThe Froan Basin and Frøya High are two major structural elements located on the Mid‐Norwegian Continental Shelf and are separated from the Halten Terrace by major west‐dipping normal fault zones. Compared to the Halten Terrace, the Froan Basin and Frøya High are relatively under‐explored and remain poorly understood in terms of their Late Jurassic tectono‐stratigraphic evolution. Upper Jurassic, shallow marine, syn‐rift deposits (i.e. Rogn Formation) are present locally, but their source, delivery system and depositional environment are not yet well understood. Improving our understanding of how fault activity and rift‐shoulder uplift influenced rift physiography and paleowater depths is crucial when developing depositional models in this region. In this study, we present a model of the Late Jurassic rift physiography of the Froan Basin and Frøya High based on seismic reflection and well data and reverse subsidence modelling. We show that during the Late Jurassic to Early Cretaceous, major footwall uplift caused the Frøya High and the western margin of the central Froan Basin to be subaerially exposed, forming an intra‐rift footwall island. Shallow marine areas to the east, immediately adjacent to the footwall island, accumulated sediment supplied from the uplifted and partially eroded footwall. In contrast, the Trøndelag Platform, north of the Froan Basin and Frøya High, remained submerged throughout the rift episode. We therefore suggest that the extent of the shallow marine system was controlled by the magnitude of footwall uplift along the western margin of the basin and that sediment dispersal was influenced by the coastal paleogeomorphology of the back‐tilted footwall.

Foraging behaviour of black guillemots at three Norwegian sites during the breeding season

The intensification of coastal development poses potential threats for coastal seabirds, and understanding their habitat use is a key factor to guide conservation and management. In sub-arctic areas, black guillemots (Cepphus grylle) use coastal habitats year-round, which makes them vulnerable to the increasing human activities in these areas. In mainland Norway, one of the species’ strongholds, black guillemots are red-listed after substantial population declines. However, their fine-scale foraging behaviour has received little attention to date. We collected and analysed GPS tracking data from adult black guillemots at three sites located over a latitudinal gradient of 250 km in central/northern Norway. Maximum foraging ranges of 33 km at Sklinna (65°12′N) for incubating birds, and 18 km at both Vega (65°34′N) and Sklinna for chick-rearing birds, are among the longest reported for this species. At all three sites, foraging probability was highest in shallow waters (< 50 m depth) close to the colony and declined with increasing water depth and distance from colony. However, birds from Vega also foraged over deeper waters. Kelp presence was of high importance at Sklinna, but apparently less important at Røst (67°26’N) and Vega. We also found distinct differences in foraging activity across the day and with tidal height among the sites. Inter-site differences in habitat use and foraging activity may be explained by differences in the availability of habitats and suitable prey. Our study highlights the importance of shallow marine areas for black guillemots and shows that habitat use can vary substantially between sites.

Mixed depositional processes in coastal to shelf environments: Towards acknowledging their complexity

The intricate development of coastal to shelf environments and their deposits is dominantly driven by the interplay of river, wave and tide hydrodynamic processes. These processes are, in turn, impacted by several additional factors including aeolian processes, contour currents, seasonal ice cover, the nature and mechanical characteristics of the substrate, confinement and physiography of the basin, climate oscillation and relative sea-level fluctuations. Consequently, the depositional record of these mixed-process interactions is complex and challenging to decipher. Because coastal and shallow-marine areas around the world are densely populated and subject to intense and increasing natural and anthropogenic stresses, a better understanding of these depositional systems will benefit their sustainable protection and development. In this special issue, contributors present their newest research on mixed-energy depositional processes and how they control the dynamics and sedimentary record of coastal to shelf environments.

Coarse‐grained, marine, sub‐wave base, high‐angle clinoform sets: A little‐known outcrop facies illustrated by Jurassic examples from East Greenland

AbstractOutcrops of coarse‐grained, high‐angle clinoform sets are mainly thought to represent Gilbert‐type deltas. Superficially similar clinoform sets may, however, form in marine, sub‐wave base settings. They are interpreted to have formed as a result of storms where downwelling, seaward‐directed currents transported sand from the coastal area and shoreface across the shelf in suspension or as bedload to be deposited as clinothems. An additional transport of sand took place by strong coast‐parallel currents. The clinoform sets appear to be associated with rift events, the creation of accommodation space and an increasing supply of coarse‐grained sediment. A major protracted rift phase was initiated in East Greenland in Middle Jurassic times and intensified through the Late Jurassic to reach a climax close to the Jurassic–Cretaceous boundary. Rifting caused uplift of borderlands, creation of accommodation space and development of shallow marine shelves passing offshore into submarine slopes and deeper basinal areas. Each rift event was accompanied by the formation of clinoform sets prograding seawards towards the east and southeast away from the cratonic coastline in water depths below the wave base. The clinoform sets are interpreted as typical motifs for rift events in the relatively shallow epeiric Jurassic seaway between East Greenland and Norway. Outcrops of such sets represent a little‐known, commonly misinterpreted sedimentary system and may serve as motifs for rifting in shallow marine areas elsewhere in the geological record. Similar sets have been recorded in outcrop from the Mediterranean, and elsewhere and are probably more common than hitherto realized.

High-Precision Inversion of Shallow Bathymetry under Complex Hydrographic Conditions Using VGG19—A Case Study of the Taiwan Banks

Shallow bathymetry is important for ocean exploration, and the development of high-precision bathymetry inversion methods, especially for shallow waters with poor quality, is a major research aim. Synthetic aperture radar (SAR) image data benefit from a wide coverage, high measurement density, rapidity, and low consumption but are limited by low accuracy. Alternatively, multibeam data have low coverage and are difficult to obtain but have a high measurement accuracy. In this paper, taking advantage of the complementary properties, we use SAR image data as the content map and multibeam images as the migrated style map, applying the VGG19 neural network (optimizing the loss function formula) for bathymetric inversion. The model was universal and highly accurate for bathymetric inversion of shallow marine areas, such as turbid water in Taiwan. There was a strong correlation between bathymetric inversion data and measured data (R2 = 0.8822; RMSE = 1.86 m). The relative error was refined by 9.22% over those of previous studies. Values for different bathymetric regions were extremely correlated in the region of 20–40 m. The newly developed approach is highly accurate over 20 m in the open ocean, providing an efficient, precise shallow bathymetry inversion method for complex hydrographic conditions.

The Ordovician System in the Levant region (Middle East) and southern Turkey: review of depositional facies, fauna and stratigraphy

Abstract This contribution addresses the current state of knowledge of the mainly siliciclastic Ordovician rocks in Jordan, Syria and southern Turkey, including advances in palaeontology, stratigraphy, depositional facies analysis and supra-regional correlation. The extensive and excellent exposures of the sedimentary succession in southern Jordan represent the regional reference for the Ordovician System in the southern Levant. We discuss the sedimentological and faunal characteristics as well as the stratigraphy and correlation of the succession. For the northern Levant (especially southeastern Turkey) and the western and eastern Taurides, the Ordovician succession and an updated sedimentary architecture is explained, and a comprehensive correlation for the region is presented. Increased knowledge on the fossil content from these regions enables correlation across the southern parts of the Arabian Plate to southern Turkey, and with the greater Gondwanan regions, far field as southwestern Europe and northern Africa. The depositional environments in the southern and northern Levant and southern Turkey encompass non-marine to shallow-marine areas in the lower part of the Ordovician that are followed upsection by shelf deposits of variable proximity up to the glacial episode in the Late Ordovician that is traceable in each of the areas. Characteristic signals in the Ordovician succession are represented by the trans-regional early Darriwilian unconformity and by the base of the Hirnantian glacial-related deposits followed by lower Silurian strata, visible across the entire region. New data from zircon-based provenance analysis clearly implicate the Arabian Shield as the main source of a huge amount of the clastic detritus within the Ordovician succession. In the course of the entire Cambrian–Ordovician interval, progressive deeper erosion of the Arabian Shield occurred. Sediment sources from regions farther away indicate long time of exposure and resedimentation, and some long-distance transportation, but their sedimentary influence was only of minor extent. The excellent outcrops mainly in southern Jordan, in southeastern Turkey and in the Taurides represent potential regions for further research.

Satellite tracking and field assessment highlight major foraging site for green turtles in the Banc d'Arguin, Mauritania

There is a remarkable paucity of estimates of the numeric importance of sea turtles at foraging grounds. The Banc d'Arguin (BA) is a vast shallow marine area off the coast of Mauritania, known as a site of world importance for coastal migratory birds and other biodiversity, including extensive seagrass beds. We sampled foraging green turtles on the BA, and extensively tracked adult female green turtles from the Bijagós archipelago, the only significant nesting aggregation within 3000 km of the BA, to estimate the abundance of this foraging aggregation. Additionally, we used a demographic simulation to support our findings. Based on satellite tracking of adult females (n = 46), we estimate that 50 % of the nesting population from the Bijagós migrate to the BA post-nesting. We combine data on numbers nesting in the Bijagós with information on proportion migrating to the BA in the same years to conservatively estimate that 8285 adult female green turtles forage at this site. We also estimate that adult females represent only 5.6 % of the green turtles in the BA, implying that the number of turtles there is of the order of 150,000 individuals. Most of the BA enjoys effective protection as part of the Parc National du Banc d'Arguin where significant fisheries regulations are well enforced by a marine surveillance program. We show that the BA is one of the major foraging sites for green turtles nesting in the Bijagós and a site of critical importance for immature and adult green turtles in a global context.

Airborne electromagnetics as a tool to image the land-to-sea sedimentary continuum: A complementary geophysical approach to improve coastal characterization

Geophysical investigation of the entire coastal zone, including emerged and shallow marine areas, is difficult to conduct especially due to method limitations. Therefore, the land to sea transition zone is often few or not surveyed consequently blanked areas subsist in the backshore, foreshore and upper shoreface domains. This study aims to evaluate the capacity of airborne electromagnetics to image the coastal zone and particularly the land-to-sea sedimentary continuum. It focuses on the Galion and Robert Bays of the Martinique island and is based on the regional survey MarTEM, conducted in 2013 with the SkyTEM 304 system. This survey offers coverage of the whole island and provides information on the subsurface every 30 m along flightlines. Airborne electromagnetics results were compared to topo-bathymetric data, seafloor sediment surface map, ortho-photographs, cores, as well very high-resolution seismic profiles from the CARQUAKES French research program.The seafloor appears to be relatively well imaged by the electromagnetic technique and corresponds to a resistivity contrast around 0.3 Ω.m. The soft sediment deposits corresponds to the resistivity values between 0.3 and 0.8 Ω.m. The top and the bottom of the soft sediment layer were extracted from the resistivity model and thickness of sediment deposit was then calculated. Grids of the top of the basement and of the sediment thickness were obtained (130 m pixel) for the two bays. Thus, airborne electromagnetics allows imaging the land to sea continuum and giving a continuous view of the emerged part of the coast as well as shallow water area, over the whole bays and up to the penetration limit of the method (around 20 m for the system used in 2013). This is especially advantageous close to rocky coast and over turbid areas, where marine surveys are difficult to carry out. Advantages and disadvantages of the method are discussed. From this case study, it appears that airborne electromagnetics is an efficient method to investigate sediment bodies lying in the land-to-sea transition zone to complement to the other methods traditionally carried out.

Variations in pink-shrimps Farfantepenaeus brasiliensis and F. paulensis juvenile abundance: clarifying ecological patterns and providing subsidies to management in shallow marine ecosystems

In Brazilian marine ecosystems, Farfantepenaeus brasiliensis and F. paulensis are caught around 40-meter isobath, whereas in shallower waters (<20 m), juveniles are caught as bycatch in fisheries targeting other shrimp species. Despite their importance in fisheries, the ecology of the two Farfantepenaeus species is not well understood. Their recruitment patterns still are not clear and both species in adult phase are landed as pink shrimp, making evaluations impossible. In this study, we focused on evaluating a 23-year fisheries-independent dataset, seeking to clarify recruitment patterns and to relate them to El Niño Southern Oscillation events and environmental factors in the Ubatuba Bay, a traditional trawling area in Southeast Brazil. Generalized Additive Models indicated that both species shared some patterns in early life stages, being more abundant between January to April, when granulometry presented Phi ≤ 4.5, and salinities and temperatures are higher than 35 and 25 ºC, respectively. Also F. paulensis abundance increased under El Niño events. The higher capture of Farfantepenaeus spp. in a period with intense trawling activity and prior to the closed season (March to May) indicated that populations are not adequately protected in the study area. Beyond highlighting the role of shallow marine areas as potential nursery ecosystems for species of pink shrimp, these results provide evidence to support the fishing closed season in the southeastern and southern regions of Brazil.

Co-occurrence and diversity patterns of benthonic and planktonic communities in a shallow marine ecosystem

Marine microorganisms are involved in a variety of biogeochemical cycles and live in diverse ecological communities where they interact with each other and with other organisms to guarantee ecosystem functions. The present study focused on a shallow marine environment located in Ría de Vigo (NW, Spain), where sediment and size-fractionated plankton samples were collected from 2016 to 2018. DNA metabarcoding was used to describe the eukaryote and prokaryote composition and diversity in sediments and plankton and to depict possible associations among the most frequent and abundant organisms by co-occurrence network analysis. High eukaryote and prokaryote diversity indices were obtained in all compartments. Significant differences among eukaryote and prokaryote communities were found between sediment and plankton samples, with a high percentage of exclusive operational taxonomic units (OTUs) associated with each compartment, especially from sediment. Despite these differences, shared taxa between water and sediment were also obtained, suggesting a relatively meaningful exchange of organisms between both environmental compartments. Significant co-occurrences were mainly obtained between prokaryotes (41%), followed by eukaryotes–prokaryotes (32%) and between eukaryotes (27%). The abundant and strong positive correlations between organisms, including representatives from the sediment and the water column, suggested an essential role of biotic interactions as community-structuring factors in shallow waters where beneficial associations likely prevail. This study provides a novel approach for the detailed description of the eukaryote and prokaryote diversity and co-occurrence patterns in a shallow marine area, including both the sediment and different water-size fractions. The high diversity obtained and the detection of predominantly coexisting interactions among organisms from sediment and the overlying water column suggest a movement of species between both habitats and therefore confirm the importance of integratively studying shallow marine ecosystems.

Where ecologically ‘tis better to go brown than green: enhanced seagrass macrobenthic biodiversity within the canals of a brownfield coastal marina

At the start of the 21st century, a coastal residential-estate marina was developed on a previously degraded and polluted brownfield island site within Knysna estuarine bay, Garden Route National Park, South Africa, including the creation of 25 ha of new flow-through tidal canals. Canals near the larger entrance to this system now support permanently submerged beds of seagrass, which in turn support abundant macrobenthic invertebrates. In comparison with equivalent seagrass-associated assemblages present in natural channels around the island, those in the artificial marina canals were similarly structured and dominated by the same species, but the marina assemblages were significantly more species-rich (1.4 x on average) and were more abundant. Indeed, this area of marina supports the richest seagrass-associated macrofaunal biodiversity yet recorded from South Africa. The canals created de novo therefore now form a valuable addition to the bay’s marine habitat, in marked contrast to the generality that marinas developed on greenfield sites represent a net reduction in intertidal and shallow marine area and associated seagrass-associated benthos. If located and constructed appropriately, brownfield marina development and conservation of coastal marine biodiversity clearly need not be antithetical, and brownfield sites may provide opportunity for the location and management of ‘artificial marine micro-reserves’ or for the action of ‘other effective area-based conservation measures’ for soft-sediment faunas.

Conspecific Density as a Driver of Offspring Body Condition in Three Cormorant Colonies in Denmark

Density-dependent depletion of prey during the breeding season may affect breeding performance and colony development in seabirds and colonial waterbirds. Breeding Great Cormorants Phalacrocorax carbo sinensis are central place foragers, so parental flight distances to profitable foraging grounds and thus parental provisioning of offspring are likely affected by local food availability. Chick body condition in a given colony may therefore be influenced by the distance to feeding areas, changes in fish stocks and fish distribution as well as the number of Cormorants from neighbouring colonies using the same feeding areas. At three Danish Great Cormorant colonies with overlapping foraging ranges and variable access to shallow marine areas, Vorsø (VO), Mågeøerne (MA) and Stavns Fjord (SF), we investigated variation in mean chick body condition (n = 9697) in relation to colony location, year, colony size and estimated density of foraging conspecifics during 1993–2007. Foraging areas available to VO colony parents had the highest theoretical densities of conspecifics and the VO chicks were invariably in poorer condition than the chicks at the other two colonies. Chick body condition was negatively correlated with estimated foraging density, especially within a foraging range of 20 km. Body condition between all three colonies was weakly correlated over the years, suggesting that changes in macro-environmental conditions (e.g. fish density) only had moderate impacts on food availability, independently of Cormorant numbers. We conclude that both the geographical location of colonies, the size of the colony itself and the nearest neighbouring colonies and the associated variation in density of foraging Cormorants were major drivers of variation in chick body condition between colonies and years.

PREDATION ON NEOGENE OSTRACODS OF SOUTHWESTERN SPAIN

This paper analyzes the evidence for predation on ostracods observed in Neogene sediments of southwestern Spain. Eighty bored valves were extracted from the analysis of more than 2000 specimens collected in shallow marine to upper bathyal palaeoenvironments. Bored specimens are more abundant in Neogene shallow marine areas, although very high percentages can be obtained in deeper sediments with very low ostracod densities. Two main types of boreholes can be distinguished, being concentrated mainly in the central areas of the valves, and drilled mainly by the gastropods: a) Oichnus paraboloides Bromley, with more of 70% of the total boreholes; and b) Oichnus simplex Bromley. Borehole diameter shows a positive but no significant correlation with the dimensions of the predated valves. Ornamentation seems to be secondary in the predatory selection.

Possible Tsunami-Induced Sediment Transport From Coral Reef to Deep Sea Through Submarine Canyons on the Southern Ryukyu Forearc, Japan

Submarine canyons are efficient sediment transport pathways from shallow marine areas to deep sea. Along active margins, large tsunamis are a trigger for sediment transport to deep sea. However, sediment transport through submarine canyons by such extreme wave events in the carbonate depositional environments has not been fully understood. Large tsunamis have repeatedly struck the coral reef islands of the southern Ryukyu Islands and have transported large boulders composed of coral from the reef to shore. In this study, we examined sediment cores collected near the mouths of submarine canyons and basin floor on the southern Ryukyu arc’s forearc. The presence of coarse calciturbidites containing coral, molluskan fragments, and coral reef benthic foraminifera was limited on the submarine fan formed at the mouth of the reef-connected and shelf-incised submarine canyon. In cores collected near the mouth of shelf-incised submarine canyons with no reef connection and slope-confined canyons, no coarse calciturbidite is observed. Few calciturbidites were found in more downslope cores, implying that most calcareous grains derived from shallow marine areas were deposited on this fan. Depositional intervals of turbidites were calculated to be several hundred–a few thousand years, which agree with the recurrence intervals of large tsunamis estimated from onshore tsunami deposits, based on radiocarbon dates in hemipelagic mud intervals. No temporal change in the depositional intervals of calciturbidites in the cores from the submarine fan since the last glacial maximum. Therefore, the tsunamis may be an important mechanism for surface sediment reworking in coral reefs, and shelf-incised and reef-connected submarine canyons can play an important role in the efficient transport of shallow marine calcareous grains to the deep sea.

Neopleistocene aqifer sistem in the astrakhan gas condensate field: specifics, structure and models of formation

The paper presents an analysis of materials from studies of the Neopleistocene sedimentary complexes and aquifer system: lithological, mineralogical-geochemical, hydrogeochemical, hydrogeofiltration and hydrogeomigration in the region of development of the Astrakhan gas condensate field (AGCF). The main provisions of the model of the formation of groundwater, the specifics of their balance, the chemical composition of hydrogeodynamics, hydrogeomigration, and the main governing factors are formulated. The predominance of marine sediments in complexly constructed strata of the Neopleistocene, with a significant role of clay layers and fragmentary traces of continental development, was revealed. Facies and sedimentary environments characteristic of large deltas and shallow marine areas, like the modern North Caspian, have been identified. The system of deltas and deltas of large and small streams is considered with the involvement of geomorphological, landscape-climatic and geodynamic factors for the development of a model for the formation of the studied strata.In the upper part of the litho-hydrosphere of the AGKM region, a specific landscape-geomorphological pattern was revealed, reflecting the systems of zones of geodynamic instability on a scale of the first hundreds of meters-kilometers. In a significant part of the study area, an association of areas of the greatest thickness and conductivity of aquifers of the Neopleistocene complex with interdome depressions of deep halogenetic structures was revealed. The results obtained are relevant for the development of a model for the formation of aquatic-rock complexes of the Neopleistocene and management of the development of AGCF: identifying ways of spreading pollution; reducing the risk of accidents due to the instability of the foundations of the gas complex facilities and many others.

Sabellaria alveolata versus Sabellaria spinulosa Reefs along the Italian Coasts: A New Methodological Proposal to Compare Different Growth Models

Sabellaria species are among the most important frame-builders in temperate, shallow marine areas. These polychaetes are suspension feeders able to build bioconstructions using sand and shell fragments cemented with a sticky mucous. Such feature makes these invertebrates “unusual bioconstructors”, as they do not produce calcium carbonate. Sabellaridae reefs are widespread in the Mediterranean and along the Atlantic coast of Europe, but their sedimentological aspects are still poorly known. Over short time intervals, these bioconstructions can rapidly alternate between phases of growth, stasis and destruction during different seasons. In this paper, we compare reefs of two Sabellaria species (S. alveolata—Ostia, Roma and Tyrrhenian Sea; S. spinulosa—Torre Mileto, Foggia and Adriatic Sea) found at two different sites along the Italian coast. We describe the morphology of worm tubes at the macro- and microscale. Similarities and differences are discussed based on eco-biological features and physical environmental conditions. This work shows a measurement and observation scheme for this type of bioconstructions that has been verified at both the macro- and microscale and which was shown to be useful for defining evolutionary trends of sabellarian bioconstructions. The monitoring parameters were identified and verified over a long period.