Soft Bottom Sediments Research Articles

Echinoderm diversity in the soft bottom of Wulan Estuary, Demak, Indonesia

The majority of research on echinoderms in the tropics has involved coral reefs. There are relatively few studies on echinoderms connected to soft bottoms and estuaries. This work describes echinoderm species found in the soft-bottom sediments of the Wulan estuary in Demak, Indonesia, are described. Twelve species from Holothuroidea, Ophiuroidea, Asteroidea, and Echinoidea were identified. The three most prevalent species identified were Astropecten sp., P. chilensis, and Paracaudina sp. The species found differ depending on the sampling sites. Still, this knowledge expands our understanding of the richness of soft-bottom megabenthic fauna, especially the echinoderm. It could be used as a baseline to track the consequences of potential changes on this heavily sedimented river.

Main trends and results of 300-years anthropogenic impact on the geological environment and ecosystem of the Eastern Gulf of Finland

The seafloor of the eastern Gulf of Finland (the Baltic Sea), especially its easternmost part – Neva Bay – has experienced anthropogenic impacts since the beginning of the XVIII century. The aim of this paper is: i) to analyze results of different stages of anthropogenic impact on the geological environment and ecosystem, ii) to assess the influence of dredging, dumping, and aggregates (sand, gravel) and ferromanganese concretions extraction on bottom relief and sedimentation processes, and iii) to establish the major spatial and temporal trends of heavy metal accumulation in the soft bottom sediments. Since the establishment of St. Petersburg, and into the 1960s, there was a physical impact on the seabed through the construction of artificial islands, dredging, and dumping. From 1960s to the 1990s, these types of activity became even more intense, as nearshore submarine terraces were used for sand and gravel extraction, and sediment pollution (e.g., heavy metals) has become one of the main environmental problems of the region. Based on extensive geochemical data collected for the first time in the study area, we examined a vertical distribution of heavy metals in cores obtained from different sedimentary basins. Results demonstrate a trend of increasing concentration values from the 1940s to the 1990s. Background concentrations of heavy metals are based on the geochemistry of catchment areas, decreasing in concentrations from the northwest to the southeast, while the maximum concentrations of hazardous substances deposited from the 1970s to the 1990s were observed in the easternmost part of the gulf. Since the 1990s the heavy metal input to the Gulf of Finland has significantly decreased, so the concentration of these hazardous substances in the surface sediments dropped as well, demonstrating a spatial distribution corresponding more to background (natural, pre-industrial) values. On the other hand, big hydrotechnical projects, realized during the last 20 years – artificial territories and new harbors construction, accompanying with dredging and dumping, ferromanganese concretion extraction, etc. – led to resuspension and secondary pollution of water. The other problem is the expansion of anoxic areas, caused both by climate change and human-stimulated eutrophication. Near-bottom anoxic conditions stimulate heavy metal migration from bottom sediments into the water column. All these processes impacted benthic communities as our review of previously published studies reveals. Geological and geophysical research revealed that within some areas anthropogenic impact caused a complete change of the sedimentation processes such as direction and rates of transport, which led to the total transformation of bottom relief, surface sediment distribution, and the benthic communities.

Predicting sea pen (Pennatulacea) distribution on the UK continental shelf: evidence of range modification by benthic trawling

Sea pen communities are United Nations General Assembly-designated Vulnerable Marine Ecosystems which occur worldwide in soft-bottom sediments where trawling often occurs. However, the ability of marine managers to assess, monitor and mitigate impacts to sea pens at national scales has been constrained by a limited understanding of their environmental requirements, geographical distribution and responses to trawling. In this study, we used random forest species distribution modelling (SDM) to predict the distribution of suitable habitat for 3 sea pen species (tall sea pen Funiculina quadrangularis, slender sea pen Virgularia mirabilis and phosphorescent sea pen Pennatula phosphorea) on the UK continental shelf, exploring the results relative to the distribution of fishing activity. Occurrence of all 3 species corresponded to areas of low current and wave velocity, where suspended matter in the water column was also low. However, for F. quadrangularis, the largest species, the models indicated substantially different drivers of distribution between the Greater North Sea and Celtic Seas ICES Ecoregions. This disparity appears to reflect modification to the range and realised niche of this species in the Greater North Sea, due to trawling impacts. P. phosphorea and V. mirabilis appear to be more resilient to trawling, with no clear negative relationships observed. Our findings illustrate the value of broadscale qualitative comparisons between SDMs and human activity data for insights on pressure-state relationships. When combined with robust distribution maps, this improved understanding of vulnerability will enable marine managers to make ecologically sound, defensible decisions and deliver tangible conservation outcomes for sea pen communities.

Utilizing benthic foraminifera to explore the environmental condition of the Laizhou Bay (Bohai Sea, China)

Through the analysis of benthic foraminifera in the soft bottom sediments of the Laizhou Bay – Yellow River Delta system, this study characterized the foraminiferal biotopes and explored the possibility of obtaining an index of ecological quality comparable with other estuarine and coastal environments of the world. Five foraminiferal biotopes have been identified and their distribution patterns highlight the ecological stress from the marine-fluvial water mixing and pollution. The foraminiferal species were analyzed as a function of organic carbon gradients, and the main species were assigned to four ecological groups based on their sensitivity/tolerance towards an increasing stress gradient. Finally, the relative proportions of the species assigned to the four different ecological groups were used for the definition of a marine biotic index based on foraminifera, i.e. the Foram-AMBI, and thus the assessment of the ecological quality status of marine soft-bottom habitats.

Distribution and extent of benthic habitats in Puck Bay (Gulf of Gdańsk, southern Baltic Sea)

The majority of the southern Baltic Sea seabed encompasses homogenous soft-bottom sediments of limited productivity and low biological diversity, but shallow productive areas in the coastal zone such as wetlands, vegetated lagoons and sheltered bays show a high variety of benthic habitat types offering favourable biotopic conditions for benthic fauna. Within Polish marine areas, semi-enclosed Puck Bay (the western part of the Gulf of Gdańsk) features an exceptionally diverse environment covering a range of benthic habitats which underscores its unique biological value and aesthetic quality and providing an impetus for conservation and ecosystem-based development. Full-coverages maps on benthic habitats in this area are therefore a necessary foundation for maritime spatial planning and implementation of strategies for sustainable management and protection of the coastal environment. This study presents the first comprehensive description and distribution of benthic habitats in Puck Bay which were categorised using the revised EUNIS 2019 classification system. Typological analyses were carried out based on inventory datasets from 1995 to 2019 including scientific publications, satellite images, open databases, topographic and geological maps, reports, theses, information available on websites and unpublished data shared willingly by individual researchers and administrative institutions. Collating various spatial data sources, that were first georeferenced and then visualized using techniques available in ArcMap 10.4.1 software (Esri), resulted in the mapping of benthic habitats and sites of important and protected plant species, which can contribute to the high confidence in environmental assessments and monitoring activities.

Distribution of Alien Polychaetes in Biotopes of the Northern Part of the Black Sea

The article analyzes the distribution of alien polychaetes in the northern part of the Black Sea using the original material collected in 1998–2019, which includes ten species from five families, and published data. The family Spionidae is represented by five species; two species belong to the family Serpulidae; and the families Pilargiidae, Scalibregmatidae, and Sabellidae are represented by one species each. The distribution of polychaetes across the biotopes of the northern part of the Black Sea is as follows: Polydora cornuta Bosc, 1802 and Streblospio gynobranchiata Rise & Levin, 1998 are widely distributed on soft bottom sediments in the shallow area of semi-enclosed bays, lagoons and ports. Similarly, Sigambra tentaculata (Treadwell, 1941) is recorded from soft substrates in shallow waters, but largely occurs at the coast that fronts on the open waters. Dipolydora quadrilobata (Jacobi, 1883) is the only representative of the deep-water area of the Black Sea. The species Marenzelleria neglecta Sikorski & Bick, 2004 and Hyboscolex cf. pacificus (Moore, 1909) are occasionally encountered on soft bottom sediments. Hydroides dianthus (Verrill, 1873) and Pseudopotamilla cf. reniformis (Bruguiere, 1789) are recorded from fouling (or other styles of attachment) on hard substrates, as well as Ficopomatus enigmaticus (Fauvel, 1923), whose status of an introduced species needs clarification. Two species, Polydora websteri Hartman in Loosanoff & Engle, 1943 and H. dianthus, which settle on the shells of mollusks, while negatively affecting them, can be classified as invasive species. In the Black Sea basin, polychaetes were probably introduced at the pelagic stage with ballast waters or in fouling of ships. The species F. enigmaticus, P. cornuta, and S. tentaculata introduced to the Black Sea more than 60 years ago can be considered fully naturalized.

Integrative assessment of ecological responses and chemical contamination of urban wastewater outfalls on soft bottom sediments of an estuarine system

Sewage outfalls are one of the main anthropogenic impacts to coastal systems. Linking the chemical analysis in sediment, and changes in the ecological responses is one of the main tasks in ecosystem assessment for the protection of the marine environment. A three-tiered approach to evaluate the impact of the sewage of a recently built and obsolete Urban Waste Water Treatment Plants (UWWTPs) was performed. The sewage from each UWWTP differentially affected surrounding sediments. Macrobenthic community changes were influenced by the chemical composition in the sediments but also by grain size and organic matter. Abundance of the different families of the macrobenthic communities were correlated with most of the chemicals analyzed. On the contrary, toxicity bioassays were correlated with Zn and PCB concentrations but not with environmental variables. The toxicity tests linked the effect of chemical contamination on macrobenthic communities. A joint assessment of both chemical concentrations and their ecological effects is recommended.

Invasive ecosystem engineers threaten benthic nitrogen cycling by altering native infaunal and biofouling communities

Predicting the effects of invasive ecosystem engineering species in new bioregions has proved elusive. In part this is because separating biological effects from purely physical mechanisms has been little studied and yet could help predict potentially damaging bioinvasions. Here we tested the effects of a large bio-engineering fanworm Sabella spallanzanii (Sabella) versus worm-like structures (mimics) on gas and nutrient fluxes in a marine soft bottom sediment. Experimental plots of sediment in Hauraki Gulf (New Zealand) were used to test the hypothesis that ecosystem engineers negatively influence benthic ecosystem function through autogenic mechanisms, facilitating activity by biofouling organisms and competitive exclusion of native infauna. Enhanced physical structure associated with Sabella and mimics increased nitrogen fluxes, community metabolism and reduced denitrification from 23 μmol m−2 h−1 to zero at densities greater than 25 m2. Sabella plots on average had greater respiration (29%), NH4 release (33%), and greater NO3 release (52%) compared to mimics, suggesting allogenic (biological) mechanisms occur, but play a secondary role to autogenic (physical) mechanisms. The dominance of autogenic mechanisms indicates that bio-engineers are likely to cause significant impacts when established, regardless of fundamental differences in recipient regions or identity of the introduced bio-engineer. In the case of Sabella spallanzanii, compromised denitrification has the potential to tip the balance of net solute and gas exchanges and cause further ecological degradation in an already eutrophic system.

Silica Storage, Fluxes, and Nutrient Stoichiometry in Different Benthic Primary Producer Communities in the Littoral Zone of a Deep Subalpine Lake (Lake Iseo, Italy)

Benthic vegetation at the land-water interface is recognized as a filter for silica fluxes, which represents an important but under-investigated subject. This paper aims to analyze stocks and fluxes of biogenic (BSi) and dissolved (DSi) silica in relation to nitrogen (N) and phosphorus (P) in the littoral zone of a deep lake. Specifically, we evaluated how different primary producers can influence BSi retention and DSi release. The study was performed from April to October in 2017, in three different benthic communities: submerged aquatic vegetation (SAV) and microphytobenthos (MPB), both occurring in soft bottom sediments, and epilithic macro- and microalgae (EA) on rocky substrates. The main result was that SAV and MPB were a DSi source and a N and P sink with the DSi efflux from SAV nearly three times as much as in MPB patches. These findings corroborate the hypothesis that SAV mediates the DSi transport from pore water to the water column. Conversely, EA communities were a DSi sink and a N and P source. Overall, these results highlight the fact that the littoral zone of lakes plays a key role in regulating aquatic Si cycling, which is likely to depend on the health status of SAV communities.

A New Technology of Coring for Bottom Soft Sediments

A new technology for coring of weakly consolidated sediment is proposed. The technology includes the original coring system and the way it is operated. The technology is based on a number of original solutions: (1) unification of the elements of the drill string, where household pipes made of PVC are used as a sampler and rods; (2) the use of the valve mechanism of a simple conical construction; (3) the method of vertical freezing of the core in open air. The coring system makes it possible to obtain the cores of the soft bottom sediment in winter from ice at a water depth of up to 7–10 m. Field tests have shown that the proposed system is inexpensive, easy to assemble and operate, very effective, and reliable. The new system can be used as an alternative or complement to existing systems for coring of bottom sediments.

Distribution of soft bottom macrobenthic communities in tropical marinas of Singapore

The establishment of marinas alters physico-chemical conditions and affects distribution of resident epibiotic and pelagic communities along coastal areas. However, information on the soft bottom macrobenthos within and around these boating facilities in the tropics is limited. Here, we investigated if macrobenthic communities differed among three representative tropical marinas, and whether the communities inhabiting the marinas differed from those outside the marinas. Ekman grab sampling of the soft bottom sediment at three Singapore marinas – Raffles Marina (RM), ONEo15 Marina (OMC), Marina at Keppel Bay (MKB) – yielded a total of 73 taxa from eight phyla. Accounting for temporal variations, taxonomic richness did not differ among marinas, while Shannon index (MKB > RM = OMC) and abundance (RM > OMC > MKB) did. Macrobenthic community composition differed among the marinas, with RM dominated by a high proportion of opportunistic species and OMC supporting species that were sensitive to pollution. The surveys also revealed that communities within and outside marinas differed. Unlike RM which is more enclosed, diversity was higher within MKB than outside it, likely because the latter marina had a layout that encouraged flushing which maintained good water quality. The study showed that while Singapore’s tropical marinas can support diverse groups of macrobenthic taxa, the presence of high proportions of opportunistic species suggested that pollution within the marinas was still significant. Macrofaunal diversity in tropical marinas, such as those in Singapore, may be promoted by designs that improve water exchange.

COASTAL RESOURCE ENVIRONMENT PROFILE OF CATARMAN NORTHERN SAMAR

The coastline of the municipality of Catarman, Northern Samar stretches about 13.32 kilometers and its municipal waters has an estimated area of 66.304 square kilometers. Generally it has a plain bottom topography, consisting of coarse sand and muddy terrigenous soil that is carried and deposited by the fresh water that gush out from Catarman River, the major tributary of ‘sweet water’ which enriched the substrate with nutrients that eventually give rise to algal and plankton blooms that invite schooling pelagic fishes jacking up the commercial value of the municipal water. The soft bottom sediment gently slopes on the average of 3 degrees from the intertidal zone and stretches up to 60 meters deep seaward.
 The municipality has an estimated aggregate coral reef area of 2,558 square meters with only 20% live coral cover that is mostly concentrated at the seaward side of reef edge, and with massive coral as its dominant life-form structure.
 The death of coral reefs (60 percent of the cover) is generally presumed to be an aftermath of heavy siltation that is brought about by the influx of fresh water from Catarman river and other tributaries as evidenced by the brownish color of the silted coral heads. However, sites of coral rubbles (about 10%) believed to be a remnant of the blast fishing in the area had been noticed. Non-biodegradable Solid wastes such as cellophanes and plastics were also observed neck-tied on some coral heads.
 Most of the fishes observed within 1-4 depth range along UEP- Cawayan Fringing reef and Puputihon patch reef are non-commercial reef fish species, such as Palata, Gono, Alibang-bang, lubayan while those fish species that are most preferred by fishermen are in least abundance and can only be observed at greater depth range (Molmol, Baraka, Mayamaya). Commonly, the sizes of the reef fish that were observed ranges from 6- 30 centimeters fork length suggesting that the fish stock in the area is still young. The volume of the fish stock within the reef system of Puputihon and UEP-Cawayan area is estimated to be at 15 kilograms per hectare. The high importance value of the” non-target” reef species connotes that the surrounding reef habitat has still the capability to carry out the necessary ecological processes of reef fish reproduction.
 There are 5 species of seagrasses that thrives in Puputihon islet and UEP-Cawayan fringing reef. Ecologically, these seagrass areas serve as breeding and feeding grounds for some seagrass- specific fishes and mollusks. The Turtle Grass, Thallassia Hemprichii and Cymodocea sp.dominates the seagrass community (constituting about 85 % of the area). The Eel grass (Enhalus acoroides), Spoon Grass (Halophila sp.), Needle Grass (Halodule sp.) are noted to be less occurring. Though, this macrophyte community could well serve the reef system ecologically because of its high diversity, its environmental importance is not much due to its negligible area. Approximately, the seagrass community cover an aggregate of 500 square meter.
 Of the twenty one (21) species of marine algae, ten (10) of which are chlorophytes or green algae, (four)4 phaeophytes, brown algae and Seven (7) Rhodophytes or algae that gives off red color. Only Gelidiella acerosa, a Rhodophyte and Caulerpa spp.a chlorophyte are harvested by the fisherfolks for commercial purpose. Gelidiella acerosa or gulaman dagat have a density of 98.9 square meters per hectare during the conduct of the survey.
 There are about 37 species of mollusks that are present along the UEP- Cawayan sampling sites, most of which are considered for commerce and domestic food.
 Findings revealed the species composition of mangroves in all sampling stations. There were seven (7) families, nine (9) genera, comprising fifteen (15) species of true mangroves that are found in sampling stations. A total of 654 number of individuals were identified, counted, and measured. According to number of individual (ni), api-api (Avicennia officinalis) of the family Avicenniaceae registered to be the most abundant among other species and present in all sampling stations followed by bakauan-lalake (Rhizophora apiculata) and bakauan-babae (Rhizophora mucronata) of the family Rhizophoraceae with 73 and 66 number of individuals, respectively. The least encountered species were tangal (Ceriops tagal) and pototat (Bruguiera sexangula) with 2 and 1 number of individuals, respectively.

Geochemistry and grain size distribution of surface sediments of a large semi-enclosed lagoon connected to the western Bay of Bengal

Batticaloa is a large (135.5 km2), semi-enclosed, micro-tidal lagoon that formed by barrier deposits in eastern Sri Lanka and has a unique geographic position due to its tropical monsoonal climate and absence of tectonics. The recent soft bottom sediments of Batticaloa lagoon were studied on the basis of geochemistry and grain size distribution in order to interpret their characteristics and provenance. Poor to moderately sorted medium sands are the dominant sedimentary deposits for the lagoon; therefore, a medium energy condition is suggested for sediment deposition. The average silt and clay fraction of the lagoon sediments is less than 3%, indicating medium or high energy flows. Coarser deposits are restricted to channel and lagoon mouths. The scatter plots of Nb, Zr, Cr and Sc vs. Th and Cr/V vs. Y/Ni show a felsic provenance for the sediments. The normalized diagrams of major element oxides and trace elements for the regional rocks (Vijayan Complex of Sri Lanka) indicate high country rock influence for the sedimentation for the semi-enclosed setting. The enrichment and distribution of Zr, Th, Nb, Cr and TiO2 suggest the possibility of mineral sands that are fractionated with hydrodynamic setting of the lagoon.

More amoebae from the deep-sea: Two new marine species of Vexillifera (Amoebozoa, Dactylopodida) with notes on taxonomy of the genus

Two marine members of the genus Vexillifera Schaeffer, 1926 (Amoebozoa, Dactylopodida) are described. Vexillifera abyssalis n. sp. originates from an abyssal sample of the Western Atlantic 4.5 km deep, which is the first unambiguous record of a deep-sea Vexillifera. The second species, V. kereti n. sp. was isolated from the soft bottom sediments of the White Sea (depth 106 m). An analysis of available data on the genus Vexillifera shows that it comprises many different species, yet they are very unevenly studied. The majority of species have only been described using light microscopy, and their phylogenetic relationships with other amoebae are unclear. However, available small-subunit (SSU) rRNA gene sequences of Vexillifera spp. form a robust, yet very heterogeneous clade in the phylogenetic tree. These species demonstrate a wide range of morphological and ultrastructural characters and originate from diverse habitats, suggesting that Vexillifera may need to be subdivided into several genera in the future. In addition to the described species, we sequenced the COI gene of original CCAP strains of Vexillifera bacillipedes, V. minutissima and Pseudoparamoeba pagei, thereby performing a phylogenetic reconstruction of the Dactylopodida based on a decent taxonomic sampling.

Submerged benthic macrophytes in Mediterranean lagoons: distribution patterns in relation to water chemistry and depth

A large spectrum of coastal lagoon types with a wide range of environmental conditions is observed along the French Mediterranean coast. These comprise wide trophic and salinity gradients, ranging from oligotrophic to hypertrophic status, and from nearly freshwater to slightly above marine Mediterranean Sea water salinities, respectively. The statistical analysis of a long-term dataset, including water column variables and observations of macrophyte genera, showed that salinity, depth, and then trophic status, were important factors explaining the distribution of benthic macrophytes for the soft-bottom sediments in the 34 studied French Mediterranean lagoons. Based on this, we assumed that the vegetation succession along the eutrophication gradient was different according to the lagoon salinity ranges. Euhaline and polyhaline lagoons follow the well-known Schramm schematic model, where aquatic angiosperm such as seagrasses dominate under oligotrophic conditions, and opportunistic macroalgae and phytoplankton dominate under eutrophic and hypertrophic conditions. In oligohaline and mesohaline lagoons, the succession is probably an intermediate scheme between the successions observed in small temperate lakes and in marine coastal ecosystems due to the presence of both brackish and freshwater species. We thus propose a conceptual scheme for the oligohaline and mesohaline lagoons.

A new species of Victoriopisa bantenensis (Crustacea: Amphipoda: Eriopisidae) from West Java, Indonesia

Victoriopisa bantenensis sp. nov. has not been previously reported and also the first record of the genus in Indonesian waters. It was collected from soft-bottom subtidal sediment in Banten Bay, West Java, Indonesia and is one of two Victoriopisa which has a notch on the anteroventral margin of the head. Victoriopisa bantenensis is characterized by the absence of eyes, the lateral cephalic lobes elongate and the absence of excavation on the gnathopod 2 propodus palm. Male and female of Victoriopisa bantenensis sp. nov shows sexually dimorphic characters on gnathopods 2. Male gnathopod 2 propodus palm without excavation while female with one excavation. Previously, 13 species of Victoriopisa has been described, and this one is the 14 species of the genus.

Structural and functional changes of soft-bottom ecosystems in northern fjords invaded by the red king crab (Paralithodes camtschaticus)

Abstract The red king crab invaded Norwegian coastal waters in the early 1990s after having been introduced from the northern Pacific to the Russian Barents Sea coast. The crab stock increased rapidly in NE northern Norway in the latter half of the 1990s, and since 2002 there has been a commercial fishery in the eastern invaded areas. The crab is an active predator on benthic fauna especially feeding in deep soft-bottom environments. The present study is a follow-up of previous studies (2007–09) to assess the effects of the king crab predation on soft bottom species composition, ecological functioning and sediment quality. Macroinfauna (> 1 mm) was investigated in three fjord areas in the Varanger region with low, moderate and very high crab abundances, respectively. Compared with data from 1994, most benthic species were markedly reduced in abundance, in particular non-moving burrowing and tube-dwelling polychaetes, bivalves and echinoderms. However, a few species appeared to recover from 2007–09 to 2012. Changes in ecological functioning were assessed using ‘biological traits analysis (BTA)’. Following the crab invasion there was a relative reduction of suspension and surface deposit feeding species, an increase in mobile and predatory organisms and an increase in those with planktotrophic larval development. From low to high crab abundances functioning changed from tube-building, deep deposit feeding and fairly large size to free-living, shallow burrowing and rather small size. With regard to sediment reworking, downward and upward conveyors were reduced whereas surficial modifiers increased. The changes imply that sediment biomixing and bioirrigation were reduced leading to a degraded sedimentary environment. It is suggested that establishing relationships between ecosystem functioning and crab abundances may form the basis for estimating ecological costs of the crab invasion. Such knowledge is important for managing the crab in the Barents Sea area being both a non-indigenous species affecting native ecosystems as well as a valuable resource for commercial fishery.

Echinoderm diversity of a tropical estuary in the largest river basin of the Costa Rican Pacific, Eastern Tropical Pacific

Echinoderms within the Eastern Tropical Pacific have mainly been studied in association with coral reefs. Investigations on echinoderms associated with soft-bottoms and estuaries are still scarce. The present study reports on the echinoderm species inhabiting the soft-bottom sediments of shallow-brackish waters adjacent to the largest river basin along the Pacific coast of Costa Rica, Térraba-Sierpe wetland. Nine species were recorded, three of them new records for Costa Rica: Luidia columbia, L. latiradiata, and L. superba. The most common species were L. columbia, Astropecten armatus, A. regalis, and L. latiradiata. This contributes towards current knowledge on the biodiversity of Térraba-Sierpe wetland and should be considered as a baseline upon which to monitor the effects of future impacts on this important mangrove area.

Caulleriella mediterranea, a new species of polychaete (Annelida: Cirratulidae) from the central Mediterranean Sea

A new species belonging to the genus Caulleriella Chamberlin, 1919 (Polychaeta: Cirratulidae) is described from coastal soft bottom sediments off the northwest Italy coast in fine sand at around 8 m depth. Caulleriella mediterranea sp. nov. is characterized by a slightly biannulate elongate peristomium, bidentate hooks with main fang slightly curved, a long apical tooth, and a narrow wing on the convex side and absence of capillary chaetae in neuropodia. A comparison is made with specimens that fit with the congeneric species C. alata, probably confused in the past with C. mediterranea sp. nov. Morphological characters important for differentiation of these species are discussed. The description of C. mediterranea sp. nov. testifies to an increasing trend of knowledge on cirratulid diversity in the Mediterranean Sea, a family characterized by many species considered early indicators of organic enrichmenthttp://www.zoobank.org/?lsid=urn:lsid:zoobank.org:act:227C3794-DD91-4747-900F-9308E59C0D33http://www.zoobank.org/?lsid=urn:lsid:zoobank.org:pub:0F35B814-A61D-4705-AEE0-E5A5D8C69B0C

Extension of the geographical distribution of the crab Asthenognathus atlanticus Monod, 1932, in the eastern English Channel through its commensal relationship with the polychaete Chaetopterus variopedatus (Renier, 1804)

Asthenognathus atlanticus Monod, 1932, is reported here for the first time in the area around Dieppe-Le Treport (Normandy coast in the eastern part of the English Channel). A total of 26 specimens were collected in 2015–2016 from fine and coarse sands at water depths between 12 and 25 m. Two specimens were found in the stomach of two thornback rays Raja clavata. The eastward progression of A. atlanticus is consistent with tidal residual currents in the English Channel. The period of global warming is likely favorable for this easterly progression, and the species could reach the southern part of the North Sea in a few years. Our observations in the eastern part of the English Channel also illustrate a new commensal association between the tubicolous polychaete C. variopedatus and the crab A. atlanticus, the latter being found in a variety of soft-bottom sediments ranging from muddy to coarse sands, in agreement with reports of its presence in the Rade de Cherbourg and the Bay of Seine.