Shallow-water Sea Research Articles

Adaptation and evolution of the sea anemone Alvinactis sp. to deep-sea hydrothermal vents: A comparison using transcriptomes.

Sea anemones are diverse and ecologically successful members of Anthozoa. They are often found in intertidal and shallow waters, although a few of them inhabit harsher living conditions, such as deep‐sea hydrothermal vents. Here, we sequenced the transcriptome of the vent sea anemone Alvinactis sp., which was collected from Edmond vent along the central Indian Ocean ridge at a depth of 3275 m, to explore the molecular mechanisms related to adaptation to vents. Compared with another deep‐sea anemone (Paraphelliactis xishaensis) and five shallow water sea anemones, a total of 117 positively selected genes and 46 significantly expanded gene families were found in Alvinactis sp. specifically that may be related to its vent‐specific aspect of adaptation. In addition, 127 positively selected genes and 23 significantly expanded gene families that were found in both Alvinactis sp. and P. xishaensis. Among these, vent‐specific adaptations of Alvinactis sp. may involve genetic alterations in peroxisome, ubiquitin‐mediated protein degradation, oxidative phosphorylation, and endocytosis, and its deep‐sea adaptation may involve changes in genetic information processing. Differentially expressed genes between Alvinactis sp. and the deep‐sea anemone P. xishaensis were enriched in a variety of pathways related to adaptation, such as energy metabolism, genetic information processing, endocytosis, and peroxisomes. Overall, we provided the first transcriptome of sea anemones that inhabit vents, which enriches our knowledge of deep‐sea hydrothermal vent adaptation and the diversity of sea anemones.

A Low-Complexity Underwater Acoustic Coherent Communication System for Small AUV

While underwater acoustic (UWA) communication offers a practical way to establish a wireless link with underwater vehicles, designing a UWA communication system onboard a small autonomous underwater vehicle (AUV) still poses significant challenges. As the adoption of the low-complexity, robust noncoherent communication technology is limited by low bandwidth efficiency and a low data rate, coherent UWA communication requires Doppler mitigation and channel equalization measures to achieve a relatively high data rate in a moving state. Due to the strict constraints of a small-scale AUV in terms of resources and energy consumption, it is not appropriate to use high-complexity Doppler/multipath compensation technology from the prospect of system implementation. In this paper, an efficient and low-complexity UWA differential binary phase-shift keying (DBPSK) system onboard a small AUV is proposed by simplifying the Doppler and multipath compensation. Specifically, for Doppler, the delay of the adjacent DBPSK symbols is calculated according to the Doppler estimate to facilitate delay-tuning Doppler correction. For multipath, low-complexity LMS channel equalization is incorporated with error correction coding to enable multipath mitigation. With a simple structure and low computational complexity, the proposed scheme facilitates the practical hardware implementation and system integration in the small AUV platform. The numerical simulations are conducted to assess the validity of the proposed scheme under different channel conditions and the effectiveness of the proposed scheme is further verified by two UWA communication field tests, which are performed at a practical shallow water sea and lake, respectively.

Designing and testing of Bluetooth Low Energy (BLE) system for small wooden boat identification and e-certification

This paper presented the implementation of Bluetooth low energy (BLE) devices implanted on 7 small wooden boats. The BLE implantation is aimed at boat identification and certification. We use four parameters to measure the performance of BLE signal strength, e.g., solar panel usage (with/without solar panel usage), weather effect (sunny/rain), sea wave form (shallow/tidal waters), and distance. The specification of BLE and boat identification system is also presented. From the experiment, we found that BLE signal strength performance is impacted by four parameters including its combined parameters: (a) the highest hour of the detected signal is generated when the boats are connected to the solar panel; (b) the boats transmitting the signal in sunny weather; (c) the boats are in shallow water sea wave; (d) the boats are in sunny weather and connected to solar panel will have a detectable distance for up to 30 m compared to without solar panel connection, it will only have a detectable distance for up to 15 m. It is suggested for future recommendations to expand this study with the newest BLE version and better solar panel equipment to get higher signal strength performance.

A truncated, translated Weibull distribution for shallow water sea states

Reliable probabilistic information of the long-term ocean wave climate is important in many coastal and ocean engineering applications such as the design of marine and coastal structures. There is therefore a need to establish accurate models for the long-term distribution of relevant metocean variables. One of the most important wave parameters in marine design is the significant wave height, which is a measure of the severity of the sea state, and wave loads are typically described in terms of this and other variables. Hence, a lot of effort has been put on the proper probabilistic modelling of significant wave height. However, probability distributions proposed to model significant wave height have mostly focused on deep water conditions and less efforts have been put on shallow water conditions. This paper proposes a truncated, translated Weibull distribution for the long-time distribution of significant wave height in shallow waters and demonstrates that the model fit shallow water data quite well. In particular, the proposed model describes shallow-water wave data better than the commonly used 3-parameter Weibull distribution, which is often the preferred distribution for deep water locations.

Development of a Robot for In-service Radiography Inspection of Subsea Flexible Risers

The extreme operational environmental conditions and aging conditions of subsea structures pose a risk to their structural integrity and is critical to their safety. Nondestructive testing is essential to identify defects developing within the structure, allowing repair in a timely manner to mitigate against failures that cause damage to the environment and pose a hazard to human operators. However, to be cost effective, inspections must be carried out without taking the risers out of service. This poses significant safety risks if undertaken manually. This paper presents the development of an automated inspection system for flexible risers that are used to connect wellheads on the seafloor to the offshore production and storage facility. Due to the complex structure of risers, radiography is considered as the best technique to inspect multiple layers of the risers. However, radiography inspection, in turn, requires a robotic system for in-situ inspection with higher payload capacity, precise movement of source and detector which is able to withstand an extreme operational environment. The deployment of a radiography inspection system has been achieved by developing a customized subsea robotic system called RiserSure that can provide precise scanning motion of a gamma ray source and digital detector moving in alignment. The prototype has been tested on a flexible riser during shallow water sea trials with the system placed around a riser by a remotely operated vehicle. The results from the trials show that the internal inner and outer tensile armor layer and defects in the riser can be successfully imaged in real operational conditions.

A comprehensive study of the tides around the Welsh coastal waters

A computational model has been used to explore characteristics of the barotropic tide around the Welsh coast in detail for the first time. Proper understanding of tidal characteristics is vital for the sustainable use of marine resources; particularly for industries such as marine energy extraction, aggregate mining, aquaculture, as well as regulators and agencies with responsibilities for the resource management and public safety. In shallow water areas, the influence of bathymetry and energy dissipation leads to the generation of higher harmonics that cause complex tidal phenomena. The Celtic and Irish seas, which enclose the Welsh coast (UK), are heavily industrialised shallow water seas with macro-to mega-tidal semi-diurnal tides. It is shown that tidal distortion is significant in the Bristol Channel (S. Wales) and in the large shallow estuaries of the N. Wales coast; for much of the west coast this is only significant in localised areas around headlands and islands. Tidal dominance switches from flood dominant in the south and north to ebb dominant on the west coast. Highly complex patterns of vorticity in the tidal residual flow are noted. All these factors mean that careful siting of industry and coastal management interventions is required to avoid disruption of the natural system.

Oceanographic conditions and diversity of sea stars (Echinodermata: Asteroidea) in the Gulf of California, México.

Species richness is one of the best indicators of biodiversity. However, there are few investigations on concordance of diversity patterns and environmental settings for marine regions. The objectives of this study were to correlate species richness of shallow water (< 200 m deep) sea stars with key oceanographic factors in the Gulf of California, México, and to predict species richness of Asteroidea using multiple regressions. In these analyses the Gulf was divided into nine sections of one degree in latitude (from 23-31 degrees N), at each section we recorded: continental shelf area (at 100 and 200 m depth), temperature mean and range at three depth levels (0, 60 and 120 m), thermocline depth, surface nutrient concentrations (nitrates, phosphates and silicates), surface photosynthetic pigment concentration, and integrated productivity. Sea star species richness at each latitudinal section was estimated from literature data, new collections and museum records. Species were assigned to one of the following feeding guilds: predators of small mobile invertebrates (I), detritivores (D), predators of colonial organisms (C), generalist carnivores (G), and planktivores (P). There are 47 shallow water asteroid species in the Gulf of California (16 I, 15 D, eight C, six G, one P and one not assigned). Total species richness and guild species richness showed strong latitudinal attenuation patterns and were higher in the southernmost Gulf, an area characterized by a narrow shelf, high temperature, and low nutrient concentrations. Species diversity for each guild was correlated to a set of oceanographic parameters: temperature, nitrate concentration, and integrated productivity were linked to richness in must cases. We detected that nutrients and surface pigments always presented negative relationships with species richness, indicating that productive environments limit asteroid diversity in the study area. Finally, the postulated regression models to estimate species richness from oceanographic data were significant and highly precise. We conclude that species richness of Asteroidea in the Gulf of California is related to oceanographic conditions and can be estimated from regional oceanographic information.

Distribution of sea anemones in the Southwest Atlantic: biogeographical patterns and environmental drivers

In this paper, we explore spatial patterns of shallow-water sea anemones in the Southwest Atlantic (SWA). The following hypotheses were tested: (1) the distribution of sea anemones (Actiniaria and Corallimorpharia) corroborates SWA biogeographic provinces, (2) their distribution presents a richness peak at mid-latitudes, and (3) temperature is the main abiotic driver that structures their species composition. Occurrences/registries were obtained mainly from published sources. We adopted Sorensen dissimilarity and cluster analyses to compare fauna compositions. To verify latitudinal richness patterns, we used a Hill’s numbers approach through rarefaction and extrapolation techniques. Partial redundancy analysis was performed to identify which drivers contribute more to the distribution. The sea anemone faunas are congruent with the following SWA provinces: Brazilian province (BP, 0 to 33° S), Argentinian province (36 to 43° S), and Patagonian province (43 to 56° S), and all differ from the Caribbean province (CP). Although there is a high similarity among the BP and the CP, they form significant clusters with well-supported endemism levels (> 19%). An elevated richness was found at 19–23° S, in the BP southeast (34 spp. and 13% of endemism), supporting an SWA biodiversity center. Temperature explained 64% of the distribution, and the Amazonas-Orinoco and La Plata estuaries act as soft barriers. The sea anemone distribution can be explained by features of the local current systems, combined with isolation through barriers and different ecological tolerances. Furthermore, the patterns reported herein (unprecedented for the group) are similar to those of other marine taxa. A transition zone between tropical and subtropical waters indicates diversity and species accumulation in the SWA.

Molecular Response to High Hydrostatic Pressure: Time-Series Transcriptomic Analysis of Shallow-Water Sea Cucumber Apostichopus japonicus.

Hydrostatic pressure is a key environmental factor constraining the benthic migration of shallow-water invertebrates. Although many studies have examined the physiological effects of high hydrostatic pressure on shallow-water invertebrates, the molecular response to high pressure is not fully understood. This question has received increasing attention because ocean warming is forcing the bathymetric migrations of shallow-water invertebrates. Here, we applied time-series transcriptomic analysis to high-pressure incubated and atmospheric pressure-recovered shallow-water sea cucumber (Apostichopus japonicus) to address this question. A total of 44 samples from 15 experimental groups were sequenced. Our results showed that most genes responded to pressure stress at the beginning when pressure was changed, but significant differences of gene expression appeared after 4 to 6 h. Transcription was the most sensitive biological process responding to high-pressure exposure, which was enriched among up-regulated genes after 2 h, followed by ubiquitination (4 h), endocytosis (6 h), stress response (6 h), methylation regulation (24 h), and transmembrane transportation (24 h). After high-pressure incubation, all these biological processes remained up-regulated within 4–6 h at atmospheric pressure. Overall, our results revealed the dynamic transcriptional response of A. japonicus to high-pressure exposure. Additionally, few quantitative or functional responses related to A. japonicus on transcriptional level were introduced by hydrostatic pressure changes after 1 h, and main biological responses were introduced after 4 h, suggesting that, when hydrostatic pressure is the mainly changed environmental factor, it will be better to fix sea cucumber samples for transcriptomic analysis within 1 h, but 4 h will be also acceptable.

On the Average Shape of the Largest Waves in Finite Water Depths

AbstractThis paper investigates the average shape of the largest waves arising in finite water depths. Specifically, the largest waves recorded in time histories of the water surface elevation at a single point have been examined. These are compared to commonly applied theories in engineering and oceanographic practice. To achieve this both field observations and a new set of laboratory measurements are considered. The latter concern long random simulations of directionally spread sea states generated using realistic Joint North Sea Wave Project (JONSWAP) frequency spectra. It is shown that approximations related to the linear theory of quasi-determinism (QD) cannot describe some key characteristics of the largest waves. While second-order corrections to the QD predictions provide an improvement, key effects arising in very steep or shallow water sea states are not captured. While studies involving idealized wave groups have demonstrated significant changes arising as a result of higher-order nonlinear wave–wave interactions, these have not been observed in random sea states. The present paper addresses this discrepancy by decomposing random wave measurements into separate populations of breaking and nonbreaking waves. The characteristics of average wave shapes in the two populations are examined and their key differences discussed. These explain the mismatch between findings in earlier random and deterministic wave studies.

Asteroidea (Echinodermata) from shallow-waters of the remote oceanic archipelago Trindade and Martin Vaz, southeastern Atlantic, with taxonomic and zoogeographical notes.

Trindade and Martin Vaz (TMV) is a highly isolated, oceanic volcanic archipelago located approximately 1200 km off the Brazilian coast and about 4200 km away from the nearest African coast. It has been almost 70 years since the first sea star, "Astropecten sp.", was recorded from Trindade in 1951. In the following years (1955-1971; 2006) six sea star species were added to the archipelago's fauna. After that period, however, research on shallow water echinoderms has not been conducted in TMV and no further sea star species have been recorded from there since. From 2012 to 2019, 263 daytime SCUBA diving and intertidal samplings conducted at TMV yielded 91 lots of sea stars in 7 species: Linckia guildingi Gray, 1840; Oreaster reticulatus (Linnaeus, 1758); Astropecten aff. antillensis Lütken, 1859; Copidaster lymani A. H. Clark, 1948; Luidia alternata alternata (Say, 1825); Mithrodia clavigera (Lamarck, 1816); and Ophidiaster guildingi Gray, 1840. The last five species in this list represent new records to the archipelago, with C. lymani also being the first record of the species in the southwestern Atlantic. Five shallow water species previously known from TMV have not been observed in the present survey: Asterinides folium (Lütken, 1860), Astropecten brasiliensis Müller Troschel, 1842, Astropecten cingulatus Sladen, 1883, Linckia nodosa Perrier, 1875, and Ophidiaster alexandri Verrill, 1915. Twelve sea star species are currently known from shallow waters of TMV. A list of all sea star species known from shallow waters (intertidal down to 100 meters) of the tropical southern-central Atlantic oceanic archipelagoes and islands (Ascension, Cape Verde, Fernando de Noronha, Gulf of Guinea, Rocas Atoll, Saint Helena, Trindade and Martin Vaz) with their gross distribution in the Atlantic Ocean was compiled in order to explore the existence of patterns of geographic distribution for the shallow water sea star species in the tropical southern-central Atlantic oceanic islands. It has been found that 44% of the species from TMV are of western Atlantic affinity, 33% amphi-Atlantic, and 22% circumtropical in distribution. No endemic sea star species are known from TMV to date. The even more remote Ascension (ASC) and Saint Helena (STH) are more of a mosaic than TMV. The ASC and STH fauna consist of 8 and 11 sea star species, respectively. Their endemic component totals to 25% and 27%, respectively. STH has more amphi-Atlantic and eastern Atlantic sea star species (27% each) than ASC (25% and 12.5%, respectively). Twenty-five percent of the sea star species in ASC are circumtropical in distribution, whereas no circumtropical species have been found in STH. The western Atlantic (WA) component comparatively to the eastern Atlantic (EA) one is of minor significance in STH (18% versus 27%, respectively), whereas the WA and EA components contribute equally to the taxonomic composition in ASC (12.5% each). However, patterns of faunal affinities in both islands are actually taxon-dependent.

Insights into high-pressure acclimation: comparative transcriptome analysis of sea cucumber Apostichopus japonicus at different hydrostatic pressure exposures

BackgroundGlobal climate change is predicted to force the bathymetric migrations of shallow-water marine invertebrates. Hydrostatic pressure is proposed to be one of the major environmental factors limiting the vertical distribution of extant marine invertebrates. However, the high-pressure acclimation mechanisms are not yet fully understood.ResultsIn this study, the shallow-water sea cucumber Apostichopus japonicus was incubated at 15 and 25 MPa at 15 °C for 24 h, and subjected to comparative transcriptome analysis. Nine samples were sequenced and assembled into 553,507 unigenes with a N50 length of 1204 bp. Three groups of differentially expressed genes (DEGs) were identified according to their gene expression patterns, including 38 linearly related DEGs whose expression patterns were linearly correlated with hydrostatic pressure, 244 pressure-sensitive DEGs which were up-regulated at both 15 and 25 MPa, and 257 high-pressure-induced DEGs which were up-regulated at 25 MPa but not up-regulated at 15 MPa.ConclusionsOur results indicated that the genes and biological processes involving high-pressure acclimation are similar to those related to deep-sea adaptation. In addition to representative biological processes involving deep-sea adaptation (such as antioxidation, immune response, genetic information processing, and DNA repair), two biological processes, namely, ubiquitination and endocytosis, which can collaborate with each other and regulate the elimination of misfolded proteins, also responded to high-pressure exposure in our study. The up-regulation of these two processes suggested that high hydrostatic pressure would lead to the increase of misfolded protein synthesis, and this may result in the death of shallow-water sea cucumber under high-pressure exposure.

Host recognition behaviour and its specificity in pontoniine shrimp Zenopontonia soror (Nobili, 1904) (Decapoda: Caridea: Palaemonidae) associated with shallow-water sea stars

Host recognition is characteristic of many symbiotic invertebrates, including decapods. It was previously shown that, as a rule, the wider the range of hosts the less specific is the symbiont's recognition reaction. To test this hypothesis, we investigated pattern of host use, host recognition behavior and its specificity in an obligate generalist symbiont, pontoniine shrimp Zenopontonia soror. Worldwide this symbiont inhabits at least 23 species of shallow-water tropical sea stars, 10 species of which are in the studied area, the Bay of Nhatrang, Vietnam. The main part of the Z. soror population in the Bay is unevenly distributed between 4 abundant sea star species, Acanthaster planci, Culcita novaeguineae, Choriaster granulatus and Linckia laevigata. However, the prevalence of infestation of the latter species was very low despite its abundance. Such distribution across the hosts may be related to their relative size and morphological complexity. It seems that the distribution and the number of Z. soror shrimp in the Bay are controlled not only by the number, but also by species composition of the hosts. Host selection experiment in aquaria showed that Z. soror is able to recognize and distinguish the host species with which they were associated in the sea (C. novaeguineae or A. planci) among other sea stars including species recorded as possible hosts (L. laevigata, A. planci, and C. novaeguineae). Experimental results demonstrated that the symbiont-host relationship is based on host chemical and visual cues, however, symbionts' reaction to visual cues and their ability to recognize objects visually was low. Our data show that even generalists symbionts have specificity, which is probably supported by the habit forming to a specific species of host (host-imprinting).

Paleobiogeographic distribution of rudist bivalves (Hippuritida) in the Oxfordian–early Aptian (Late Jurassic–Early Cretaceous)

In the Late Jurassic and Cretaceous the warm shallow water seas were characterized, within benthic marine organisms, by rudist bivalves, a peculiar group of mollusks that originated in the Late Jurassic and became extinct at the end of the Cretaceous. In this paper their global distribution in neritic carbonates is considered since their first appearance in the middle Oxfordian up to the first main extinction event at the end of the early Aptian. The information and data regarding global rudist occurrences throughout neo-Tethys and paleo-Pacific oceans are critically reprised from literature and organized in an Oxfordian-early Aptian Rudist database (OXAP_RDB) that encompasses 235 rudist-bearing localities all across the world, with 845 total rudist occurrences, 34 valid genera and 148 species. Actual rudist geographic distribution is investigated in order to contribute to the identification of the paleobiogeographic pattern of these benthic organisms in the paleoclimatic and paleogeographic setting of neo-Tethys and paleo-Pacific oceans, allowing to reconstruct dispersal patterns and to define four broad paleobiogeographic Provinces in the Barremian–early Aptian.

Microbial Diversity of the Red Sea Urchin Loxechinus albus during Controlled Farming in Puerto Montt, Chile, Using 16S rRNA Gene Amplicon Sequencing.

Loxechinus albus is a shallow-water sea urchin, and its distribution is related to the cold water of the Southern Hemisphere. Recently, bacterial communities, also called microbiota, in sea urchins have started being explored. In this report, we have characterized the surface, testa, and gonad microbiota using 16S rRNA sequencing.

The Fossil Cypraeidae of the Buckingham Member (Unit 10), Tamiami Formation of Southern Florida: (Mollusca: Gastropoda: Cypraeidae)

The oldest recorded fossil Cypraeidae from southern Florida date from the late Zanclean-early Piacenzian Pliocene (circa 3.8-3.6 million years ago - hereinafter “mya”) in the Myakka Lagoon System, a shallow water estuary that lies beneath the present day Sarasota area. Shallow water sea grass beds and nascent shoreline mangrove forests hosted seven Cypraeidae species in five genera. Determining the origins of these species is challenging as only steinkern casts have been found in adjacent lower layers. However, enough features are present in two of the casts to infer the ancestral presence of two of the genera. For the other genera and species, a comparison of features with the northern Florida Panhandle Cypraeidae populations dating from the Burgdigalian Miocene (16-20 mya) does suggest certain affinities. However, no direct lineage can be asserted with any confidence. The sea bed deposit layer of this period has been designated the Buckingham Member of the Tamiami Formation of southern Florida.

Method of MAI cancellation in asynchronous underwater acoustic CDMA system

In the underwater passive positioning systems (UPPS), it involves a key technology of multi-user communication that the beacons synchronously send positioning messages to the targets. Interferences from other users, referred to multi-access interferences (MAIs), can induce significant bit errors for the desired user. In this paper, we designed an underwater acoustic Code Division Multiple Access (CDMA) system using the coded cyclic shift key (CCSK) modulation, and proposed a hybrid MAI cancellation scheme based on cyclic shift inverse matrix transform (CSIMT) and recursive least square (RLS) in the CDMA system. The hybrid scheme can suppress MAI better than RLS or CSIMT, and meets the requirements of strong stability to support reliable transmission for UPPS. The CSIMT interference cancellation performs well under the far-near effects, which doesn’t depend on the accuracy of the estimation of transmitted data, and the strong MAI can be reduced by transformation of the zero-forcing correlation values using m sequence cyclic shift inverse matrix. The RLS interference cancellation is used to mitigate MAI form the detected users with comparable power, by using the estimated the channel impulse response between the receiver and the detected users, and the regenerated signal of detected users form decoder output, which allows of strong error-correcting codes, and it’s robust in an asynchronous environment. The theoretical analysis and experimental result show that the hybrid MAI cancellation scheme can effectively suppress MAI better. The shallow water sea trial was carried out near Dalian Tiger Beach Ocean Park in China, at a distance of about 5 km, the data rates of 100bps, where three users could communicate asynchronously with low failure ratio and can match the UPPS application.

Mapping of Spinochromes in the Body of Three Tropical Shallow Water Sea Urchins

Sea urchin pigments, also known as spinochromes or polyhydroxynaphthoquinones (PHNQ) have been well studied for their bioactive properties like anti-bacterial, fungicidal, antioxidant and pro-inflammatory effects. Moreover, many studies have analyzed and identified these pigments in sea urchin tests and spines but, and to the best of our knowledge, never in their body compartments or in a quantitative manner. The aim of this work was to investigate the diversity and concentration of pigments in three sea urchins localized in the same coral reef in Madagascar ( Diadema savignyi, Tripneustes gratilla and Toxopneustes pileolus). Their pigment distribution patterns were compared and linked to their behavior in order to understand better the implication of spinochromes in a sea urchin's life. Analyses and quantifications by LC-MS showed the presence of 11 different spinochromes with principally two kinds of patterns. First, D. savignyi showed a high concentration in all its body compartments with a predominance for Echinochrome A and Spinochrome D – Iso 3, a pattern close to the E. mathaei distribution found in our previous study. The presence of these pigments has been linked to their bioactive properties and suggested their implications in UV radiation protection, in reproduction, in feeding as well as in their immune systems. Secondly, T. gratilla and T. pileolus presented few spinochromes, which could explain their restricted diet and their covering behavior facing sunlight. Moreover, the absence of pigments in their gonads could be explained by their seasonal spawning occurring before our collection period. Nevertheless, the near absence of spinochromes may be counterbalanced by other bioactive compounds like their toxic proteins, which may act as either a defense mechanism or immune agents, or like carotenoid pigments already shown in sea urchin and acting as defense agents. In conclusion, spinochromes, and pigments in general, seem to play many roles in sea urchin ecology. Their highly reactive structures confer them with strong bioactive properties involved in most parts of their metabolic system and clearly participate in the survival of the sea urchins.

Ascidian spicules of Quaternary sediments from the lower slope of the Campos Basin (Brazil)

Piston core GL-77 was collected in the lower slope of the northern Campos Basin, Brazil, and consists essentially of muds that have been deposited in turbiditic currents over the last 130 ka, at least, which corresponds to the Upper Pleistocene-Holocene interval. The identified ascidian spicules belong to the Didemnidae Family and are represented by species Micrascidites vulgaris, Bonetia brevis, Rigaudia multiradiata and Monniotia fasciculata. These species have irregular abundance and distribution, with Micrascidites vulgaris being the most common. Their occurrence is interpreted as resulting from transport to the depositional site in response to climate fluctuations (glacial and interglacial periods). The transport of ascidian spicules from a shallow-water sea is supported by the presence of terrestrial organic matter, mainly phytoclasts, sporomorphs and microphytoplankton, which were transported to the slope by the river systems. The results found in this study show that the relative frequency distribution pattern of didemnid spicules is a useful tool for monitoring sediment transport in the slope.

Regional Peculiarities of Hydrobiont Bioluminescence Intensity and Chlorophyll a Concentration in Black Sea Waters

Variability in the vertical distribution of the hydrobiont bioluminescence intensity and chlorophyll a concentration in autumn along the coast of Crimea and its causes are analyzed based on expedition data and satellite information. It is shown that minimum bioluminescence intensities of marine organisms and chlorophyll a concentration were observed in the abyssal sea of the water area under study in the region of a cyclonic mesoscale eddy, where the upwelling was detected, and the thickness of the upper mixed layer did not exceed 20 m. The maximum values of the chlorophyll a concentration and bioluminescence intensity were observed at stations positioned in the shallow-water littoral sea which is rich in biogenic elements.