Muddy Sand Research Articles

Baseline seabed habitat and biotope mapping for a proposed marine reserve.

Seabed mapping can quantify the extent of benthic habitats that comprise marine ecosystems, and assess the impact of fisheries on an ecosystem. In this study, the distribution of seabed habitats in a proposed no-take Marine Reserve along the northeast coast of Great Barrier Island, New Zealand, was mapped using underwater video combined with bathymetry and substratum data. As a result of the boundary extending to the 12 nautical mile Territorial Limit, it would have been the largest coastal Marine Reserve in the country. Recreational and commercial fisheries occur in the region and would be expected to affect species’ abundance. The seabed of the study area and adjacent coastal waters has been trawled up to five times per year. Benthic communities were grouped by multivariate cluster analysis into four biotope classes; namely (1) shallow water macroalgae Ecklonia sp. and Ulva sp. on rocky substrata (Eck.Ulv); and deeper (2) diverse epifauna of sponges and bryozoans on rocky substrata (Por.Bry), (3) brittle star Amphiura sp. and sea anemone Edwardsia sp. on muddy sand (Amph.Edw), and (4) hydroids on mud (Hyd). In biotopes Por.Bry, Amph.Edw and Hyd, there where boulders and rocks were present, and diverse sponge, bryozoan and coral communities. Fifty species were recorded in the deep water survey including significant numbers of the shallow-water hexactinellid glass sponges Symplectella rowi Dendy, 1924 and Rossella ijimai Dendy, 1924, the giant pipe demosponge Isodictya cavicornuta Dendy, 1924, black corals, and locally endemic gorgonians. The habitats identified in the waters to the northeast of Great Barrier Island are likely to be representative of similar depth ranges in northeast New Zealand. This study provides a baseline of the benthic habitats so that should the area become a Marine Reserve, any habitat change might be related to protection from fishing activities and impacts, such as recovery of epifauna following cessation of trawling. The habitat map may also be used to stratify future sampling that would aim to collect and identify epifauna and infauna for identification, and thus better describe the biodiversity of the area.

낙동강 퇴적물에서 영양염류 용출특성에 관한 연구

AbstractIn this study the releasing of nutrients from sediments of Nak-dong River were investigated. We perfomed lab-scale simulation experiments using field sediment and ware. Nutrients, orgarni matter, particle size of the sediments and nutrients of released water were analyzed. Analyzed results of the sediments, mainly composed of mS(muddy Sand) sedimentary facies and IL were 2.46~6.83%, T-N were 1.189~2.492mg/kg, and T-P were 333~726mg/kg in the study area. Analyzed results of the nutrients of released water, pH and TOC were each 7.8~9.2% and 31.7~40.8% decreased after 20 days. T-N increased steadily, and NH 3 -N increased steadily then decreased, at this time NO 3 -N increase. Also NH 3 -N increased steadily, then decreased at this time. Furthermore release of phosphorus were mostly decreased.Key words:Nak-dong River, Nutrient, Phosphorus, Sediment, Release, Water quality 1.Introduction 1)다양한경로를통해수계로유입되는오염물질은최종적으로퇴적물에축적된다. 유역으로부터유입되어수저에쌓이는모래, 점토, 유기물질, 광물질등의퇴적물은하상의변화와유속의저하에의해운반력이약화된곳에쌓이거나화학적으로침전되는것으로이러한퇴적물의이동과퇴적은주로유수에의해일어난다. 특히우리나라의하천과같이강우에의한유량변동이큰수계는집중강우시많은양의퇴적물이하천하류나호소바닥층으로이동하여축적되고, 이과정에서홍수나준설등으로인해퇴적물이재부유, 침식, 교란등의활동에의해오염물질이용출되어하천및호소의수질에심각한영향을미칠수있다(NIER, 2012).우리나라는기후변화에따른수해예방과부족한수자원확보를위해2011년부터4대강의정비사업을실시하였고, 그일환으로4대강에16개의보가건설되었다(MOLIT, 2009). 그러나이와같이하천의체류시간을늘려유량을확보하

Mollusc Species Composition in Shell Bearing Sites At Kalamatiya, Southern Sri Lanka

This paper discusses the mollusc species composition as revealed from the mid-late holocene coastal shell bearing formations, which have not yet been widely considered. The primary goal of the research was to study shell middens located in association with shell beds at Kalamatiya in the southern Province. The range of species recorded from the site was employed as a criterion for define shell middens in the study. Excavation of a 1 m2 test unit was employed to gather data while soil samples from each layer were sieved to obtain micro remains. Total of 18 mollusc species recorded from the nine layers of a single site at Kalamatiya (Named site 01) are discussed here. The most frequent species recorded was Meretrix sp. The layer six (shell midden) of site 01 displays a greater species diversity within the site in comparison to low numbers identified beneath layers. Layer six itself contained 12 species, i.e., Meretrix sp., Anadara sp., Donax cuneata, Saccostrea sp., Cerithedia cingulate, Acavus heamestoma, Aulopoma hofmeisteri, Beddoma trifasiatus, Papyridea soleniformis, Eunaticina sp., and two unidentified bivalve species (nacreous and calcareous). Therefore it seems that none of the middens in these formations is consisted of only one species. Total number of shells obtained from this layer was 2,393, whereas 96.5% is Meretrix sp. and other 11 species share 3.5%. Species identified from other layers are Umbonium vestiarium, Oigospera polei, Lissachatina fullica, Tapes sulcarius, Purpura persica and Cryptonatica operculata. In general, the shell bearing sites tend to produce a good approximation of the range of species indicating that the pre historic inhabitants gathered whatever was available. These species are from a wide range of environments as littoral muddy sand, coastal sands, terrestrial and arboreal. Four of the species have one occurrence (n=1) while another four species appear less than eight in number. Apart from building a taxonomical list, these data aid to study subsistence strategies of prehistoric communities and reconstruct their environment. Further these data can be used for palaeo-environmental reconstructions as well. Keywords: Shells, Molluscs, Middens, Palaeo-environment

Abundance of non-native crabs in intertidal habitats of New England with natural and artificial structure.

Marine habitats containing complex physical structure (e.g., crevices) can provide shelter from predation for benthic invertebrates. To examine effects of natural and artificial structure on the abundance of intertidal juvenile crabs, 2 experiments were conducted in Kingston Bay, Massachusetts, USA, from July to September, 2012. In the first experiment, structure was manipulated in a two-factor design that was placed in the high intertidal for 3 one-week periods to test for both substrate type (sand vs. rock) and the presence or absence of artificial structure (mesh grow-out bags used in aquaculture, ∼0.5 m2 with 62 mm2 mesh openings). The Asian shore crab, Hemigrapsus sanguineus, and small individuals of the green crab, Carcinus maenas, were observed only in the treatments of rocks and mesh bag plus rocks. Most green crabs were small (<6 mm in carapace width) whereas H. sanguineus occurred in a wide range of sizes. In the second experiment, 3 levels of oyster-shell treatments were established using grow-out bags placed on a muddy sand substrate in the low intertidal zone: mesh grow-out bags without shells, grow-out bags with oyster shells, and grow-out bags containing live oysters. Replicate bags were deployed weekly for 7 weeks in a randomized complete block design. All crabs collected in the bags were juvenile C. maenas (1–15 mm carapace width), and numbers of crabs differed 6-fold among treatments, with most crabs present in bags with live oysters (29.5 ± 10.6 m−2 [mean ± S.D.]) and fewest in bags without shells (4.9 ± 3.7 m−2). Both C. maenas and H. sanguineus occurred in habitats with natural structure (cobble rocks). The attraction of juvenile C. maenas to artificial structure consisting of plastic mesh bags containing both oyster shells and living oysters could potentially impact oyster aquaculture operations.

Surface sediment dynamics along the Tunisian coast at Skhira (Gulf of Gabès, south-eastern Tunisia)

An investigation was conducted in the summer of 2012 at 24 study stations along the Tunisian coast near Skhira (south-eastern Mediterranean Sea) through high resolution of analyses, grain size and mineral composition of surface sediment. An Acoustic Doppler Current Profiler showed Skhira's main coastal current to follow a direction 60°E, with its main axis south-west/north-east parallel to the coastline and its minor axis east-west. Current speeds were approximately 13 cm s−1 and 4.5 cm s−1 for the major and minor axes, respectively. Parallel to the coast, currents were generally mild to moderate, but often exceeded 20 cm s−1. An Argonaut meter recorded the dominant current direction as north/north-east with a speed not exceeding 18 cm s−1. Orthogonal Empirical Function analysis of tidal currents showed that the major axis velocity dispersion was north-east/south-west, the water mass flow parallel to the shoreline being almost unidirectional, driving littoral drift parallel to the coast. Spatial distribution of particle size, along with speed and current direction analysis, furnish an overview of the Skhira area's sediment dynamics and transport. Average sand grain size shows that the bottom consists of fine and especially of medium sands near the coast, with muddy sands offshore. The fine fraction percentage (<63 microns) as opposed to the coarse fraction (>63 microns) is higher at the two offshore study stations, 20 m deep. Fine particles are discharged into the sea by rip currents.Sediment dynamics along the Skhira coast are complex, being subject to the combined effect of swell and tide. Sediments are permanently re-suspended and in constant movement, especially during storms.

Sebaran Fraksi Sedimen Dasar Permukaan di Perairan Pantai Pulau Topang Provinsi Riau

A study was conducted in december 2013 in coastal waters Topang Island RiauProvince, with a view to learn the environmental conditions under the deposition ofoceanography and physics. The method used is a method of surveys carried out at 12 stationswithout repetition and 2 times repetition on calculations of the quality of the waters .Theresults of research shows that bottom sediment surface waters can be grouped into threefaction sediment is sandy mud , muddy sand and sand .Sand faction dominating at anyresearch station with type 2 is sand and muddy sand .Based on the parameter of sediment asthe diameter of average (Mz), sorting ( ), skewness (Sk1) and kurtosis (KG), physicaloceanographic conditions in Western and Eastern parts of the island tend to be stablecompared to the North and South. Current speed of surface affect the distribution of thebottom sediment surface.

Triggering larval settlement behaviour and metamorphosis of the burrowing ghost shrimp, Lepidophthalmus siriboia (Callianassidae): do cues matter?

Larval settlement and metamorphosis of many estuarine decapod crustaceans are triggered by environmental cues and chemical substances produced by the conspecific population. Here, we examined the influence of substrata and conspecific cues on the stimulation of the megalopal stage of the burrowing ghost shrimp (Lepidophthalmus siriboia) in the following five treatments: (1) adult-conditioned seawater (ACSW), (2) filtered seawater (FSW) + sand, (3) FSW + muddy sand (MS), (4) ACSW + MS and (5) FSW without cues (control). All megalopae settled and exhibited burrowing behaviour in the treatments containing substratum. The percentage of metamorphosis to juvenile was high (≥96%) in all treatments. Megalopae developed significantly faster in the control (5.7days, ±0.9s.d.) than in the remaining treatments (6.8–7.3 days). These findings demonstrated that settlement of L. siriboia megalopae is strongly induced by substrata, whereas their metamorphosis occurs irrespective of the presence or type of exogenous cues associated with estuarine habitat and conspecific adults. This suggests certain flexibility concerning the ontogenetic stage at which recruitment to the benthos occurs. The independence of metamorphic inducers should be important for colonisation of new estuarine areas as well as for recovery and maintenance of viable populations in disturbed habitats where callianassid ghost shrimps are heavily exploited.

Confessions of an ambidextrous fiddler crab

Confessions of an ambidextrous fiddler crab

Three New distributional records of Pen Shells (Bivalvia: Pinnidae) from Seagrass beds of Palk Bay Area in Tamil Nadu

The new occurrence of Three species of bivalves from Pinnidae family is recorded for the first time from Palk Bay area based on a live and dead shells collected from the Intertidal area . All the three species are under the family of Pinnidae, Pinna bicolor, Pinna deltodes and Pinna incurva . In seagrass bed of Thondi Coast, all the species of Pen shells Pinna bicolor, Pinna deltodes and Pinna incurva were embedded in muddy sand and found associated with seagrasses at inter-tidal area. It was also found buried in hard substratum associated with living zoanthids and soft coral. The collected specimens were identified as, (1) Pinna bicolor, (2) Pinna deltodes and (3) Pinna Incurva by using both morphometric and meristic characters. The paper described the taxonomic status and the description of the three species of bivalves collected from Palk Bay areas.

Actuopaleontological characterization and molluscan biodiversity of a protected tidal flat and shallow subtidal at the northern Red Sea

Tidal flats are abundantly developed throughout the Phanerozoic but actualistic studies on subtropical‒tropical tidal flats are rare. This study of a tidal flat and shallow subtidal of a lagoon protected behind a fringing reef at the northern Red Sea is therefore aimed to contribute to the understanding of the distribution and abundance of paleontologically relevant fauna and its lebensspuren. Muddy sands to sands and beachrock are the predominating benthic habitats. Important ecosystem engineers are the oyster Saccostrea cucullata, which forms decimeter- to meter-scale bioherms in the lower intertidal, the ocypodid crab Dotilla sulcata, which reaches highest abundances on the tidal flat, some tens of meters from the low-tide line, and the callianassid decapod Paratrypaea bouvieri, which is very abundant in the subtidal. The sediment surface in the intertidal was densely covered with lebensspuren of gastropods. Quantitative and qualitative samples revealed 130 species of molluscs from 51 families. Most species found belong to the Veneridae, Lucinidae, Turridae, Cardiidae, Trochidae, and Pyramidellidae in the subtidal and to the Cerithiidae in the intertidal, but overall only 32 species were found alive (13 on the tidal flat, 28 in the subtidal). Distinct assemblages of living and dead molluscs characterized the intertidal and subtidal, which suggests that dead shells can be used to assess regional biodiversity. Numerically, the living assemblage on the tidal flat was strongly dominated by the deposit-feeding potamidid gastropod Pirenella conica, and in the subtidal by infaunal bivalves (Glycymerididae, Lucinidae, Tellinidae, and Veneridae). Predatory gastropods (Naticidae, Melongenidae, Fasciolariidae, Muricidae, and Conidae) were accessory components that were mostly present in qualitative samples in the subtidal and lower intertidal. Accordingly, frequencies of drilling predation for the total assemblage are significantly higher in the subtidal (25.7 %) than in the intertidal (1.2 %). We conclude that the preservable fauna and its lebensspuren are characteristically developed along an environmental gradient and suitable to distinguish intertidal from subtidal habitats in a potential fossil record.

Ice sheet extension to the Celtic Sea shelf edge at the Last Glacial Maximum

Previous reconstructions of the British–Irish Ice Sheet (BIIS) envisage ice streaming from the Irish Sea to the Celtic Sea at the Last Glacial Maximum, to a limit on the mid-shelf of the Irish-UK sectors. We present evidence from sediment cores and geophysical profiles that the BIIS extended 150 km farther seaward to reach the continental shelf edge. Three cores recently acquired from the flank of outer Cockburn Bank, a shelf-crossing sediment ridge, terminated in an eroded glacigenic layer including two facies: overconsolidated stratified diamicts; and finely-bedded muddy sand containing micro- and macrofossil species of cold water affinities. We interpret these facies to result from subglacial deformation and glacimarine deposition from turbid meltwater plumes. A date of 24,265 ± 195 cal BP on a chipped but unabraded mollusc valve in the glacimarine sediments indicates withdrawal of a tidewater ice sheet margin from the shelf edge by this time, consistent with evidence from deep-sea cores for ice-rafted debris peaks of Celtic Sea provenance between 25.5 and 23.4 ka BP. Together with terrestrial evidence, this supports rapid (ca 2 ka) purging of the BIIS by an ice stream that advanced from the Irish Sea to the shelf edge and collapsed back during Heinrich event 2.

Recruitment facilitation and spatial pattern formation in soft‐bottom mussel beds

Mussels (Mytilus edulis) build massive, spatially complex, biogenic structures that alter the biotic and abiotic environment and provide a variety of ecosystem services. Unlike rocky shores, where mussels can attach to the primary substrate, soft sediments are unsuitable for mussel attachment. We used a simple lattice model, field sampling, and field and laboratory experiments to examine facilitation of recruitment (i.e., preferential larval, juvenile, and adult attachment to mussel biogenic structure) and its role in the development of power‐law spatial patterns observed in Maine, USA, soft‐bottom mussel beds. The model demonstrated that recruitment facilitation produces power‐law spatial structure similar to that in natural beds. Field results provided strong evidence for facilitation of recruitment to other mussels—they do not simply map onto a hard‐substrate template of gravel and shell hash. Mussels were spatially decoupled from non‐mussel hard substrates to which they can potentially recruit. Recent larval recruits were positively correlated with adult mussels, but not with other hard substrates. Mussels made byssal thread attachments to other mussels in much higher proportions than to other hard substrates. In a field experiment, mussel recruitment was highest to live mussels, followed by mussel shell hash and gravel, with almost no recruitment to muddy sand. In a laboratory experiment, evenly dispersed mussels rapidly self‐organized into power‐law clusters similar to those observed in nature. Collectively, the results indicate that facilitation of recruitment to existing mussels plays a major role in soft‐bottom spatial pattern development. The interaction between large‐scale resource availability (hard substrate) and local‐scale recruitment facilitation may be responsible for creating complex power‐law spatial structure in soft‐bottom mussel beds.

First Zoeal Stage of Camptandrium sexdentatum (Crustacea: Decapoda: Camptandriidae)

The first zoea of Camptandrium sexdentatum is described for the first time with a digital image of live zoeas. An ovigerous crab of C. sexdentatum was collected at the muddy sand flat in Namhaedo Island on 2 June 2012 and hatched in the laboratory on 6 June 2012. In Camptandriidae, the first zoea of C. sexdentatum is distinguished from the first zoeas of Cleistostoma dilatatum and Deiratonotus cristatum by having no dorsal and lateral carapace spines, an abdomen significantly broadened posteriorly, and a subovoid telson without forks. Especially, the finding of a subovoid telson without forks is the first report in brachyuran zoeas.

Core and sediment physical property correlation of the second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) results in the East Sea (Japan Sea)

We analyzed the data consist of core digital images and X-rays, core-logs, LWD (logging-while-drilling), and sediment grain-size from the second Ulleung Basin Gas Hydrate Expedition (UBGH2) in the East Sea. Core digital images and X-rays were spliced as a complete composite core in meters below seafloor (mbsf) for five sites; UBGH2-1_1 (Hole D), 2_1 (B), 2_2 (B), 2-6 (B) and 2-10 (C–D), and were correlated with the core-log and LWD measurements showing that possible gas hydrate bearing layers are between the depths of about 60–180 mbsf at these sites. Bulk densities generally increase with depth from 1.3 to 2.0 g/cm3 in LWD data, and from 1.1 to 1.8 g/cm3 onboard which measured lower than in-situ. Gas hydrate bearing sediments respond with an increase of LWD densities (1.4–1.6 g/cm3) and a decrease in core-logs (1.1–1.4 g/cm3). P-wave velocity values of LWD increase (1400 to 1700 m/s) with depth for non-reservoirs, and are high (1500 and 2000 m/s) within the gas hydrate bearing intervals depending on the hydrate saturations.Resistivity values logged onboard range from less than 1.0 to over 10.0 Ω-m, while LWD records are around 1.0 Ω-m and between 5.0 and 30.0 Ω-m in background sediments and possible gas hydrate reservoirs, respectively. High resistivity values were observed (5.0–30.0 Ω-m) within coarse-grained turbidites (mean grain-size between 2.9 and 5.1 ϕ; laminated sandy mud or muddy sands). Medium resistivities were observed (5.0 Ω-m) within the silt-dominant hemi-pelagic and turbiditic sediments (5.1–7.4 ϕ; crudely laminated, bioturbated, homogeneous sand, and disintegrated sand and sandy mud facies) bearing pore-filling gas hydrates, or disseminated gas hydrates either formed in pores or small fractures of fine-grained sediments. Core-log measurements are highly fluctuating and sensitive but mostly lower (e.g., density and resistivity) than LWD records.

Atlantic Rock Crab, unlike American Lobster, Is Important to Ecosystem Functioning in Northumberland Strait

AbstractTo compare the roles of American lobster Homarus americanus and Atlantic rock crab Cancer irroratus in the food web processes of a coastal ecosystem, distribution, abundance, stomach contents, diet overlap, and occurrence in stomachs of predators were described for the two species collected during July–August trawl surveys in Northumberland Strait, southern Gulf of St. Lawrence. Atlantic rock crab was more widely distributed, was more numerous on mud and muddy sand substrates, and occurred in deeper water than American lobster. Atlantic rock crab was the principal prey of American lobster while American lobster was almost never eaten by Atlantic rock crab. American lobster (benthic and pelagic stages) was a trace item in all fish and decapod stomachs examined except in those of the Shorthorn Sculpin Myoxocephalus scorpius and other American lobsters. In contrast, Atlantic rock crab larvae commonly occurred in stomachs of many pelagic fishes while small (&lt;40 mm carapace width) benthic individuals were important prey of demersal fish species such as Winter Skate Leucoraja ocellata, Cunner Tautogolabrus adspersus, Longhorn Sculpin M. octodecemspinosus, and Shorthorn Sculpin. Atlantic rock crab had a broad diet consisting of fish, sevenspine bay shrimp Crangon septemspinosa, Atlantic rock crab (mostly cannibalism), bivalves, and polychaetes. American lobster had a narrow diet consisting mainly of Atlantic rock crab with lesser amounts of American lobster (old carapaces and cannibalism) and sea stars. Diet overlap between the two species was moderate and mainly due to joint consumption of Atlantic rock crab. Thus, Atlantic rock crab play a prominent role in the southern Gulf of St. Lawrence food web (and therefore energy cycling) while American lobster serves mostly as an energy sink whose loss from the ecosystem would mainly affect people dependent upon the fishery.Received January 3, 2014; accepted May 30, 2014

The surface sediment types and their rare earth element characteristics from the continental shelf of the northern south China sea

The grain size as well as some major and trace elements, including rare earth element (REE), for 273 surface sediment samples collected from the continental shelf of the northern South China Sea were analyzed in this study. The sediment types are mainly sandy silt and silt, making up 60% of the whole samples, and secondly are mud, sandy mud, muddy sand and silty sand, making up 28% of the whole samples, based on grain-size in which the Folk׳s classification was used. The total REE content (ΣREE) show a wide variation from 21ppm to 244ppm with an average value of 155ppm, which similar to the average ΣREE of the China loess, but much different from that in deep-sea clay, showing a significant terrigenous succession. The REE contents in different sediment types vary greatly, mainly enriching in silt, sandy silt, mud and sandy mud. The REE distribution contours parallel to the coastal, presenting like strips and their contents gradually reduce with increasing distance from the coast. The high content of the western Pearl River Mouth, Shang/Xiachuan Islands and Hailing Bay might be regarded to the coastal current developed from the east to the west along to the Pearl River Mouth in the northern South China Sea. But the chondrite-normalized REE patterns in various sediment types have no difference, basically same as those of coastal rivers and upper crust. They all show relative enrichments in light rare earth element (LREE), noticeable negative Eu anomaly and no Ce anomaly, indicating that those sediments are terrigenous sediments and from the same source region. Further analysis suggest that the sedimentary environment in the study area is relatively stable and granite widely distributed in the South China mainland is the main source of REE, which are transported mainly by the Pearl River. The late diagenesis has little effect on the REE.

Response of multi-metric indices to anthropogenic pressures in distinct marine habitats: The need for recalibration to allow wider applicability

Sustainable exploitation of coastal ecosystems is facilitated by tools which allow reliable assessment of their response to anthropogenic pressures. The Infaunal Quality Index (IQI) and Multivariate-AMBI (M-AMBI) were developed to classify the ecological status (ES) of benthos for the Water Framework Directive (WFD). The indices respond reliably to the impacts of organic enrichment in muddy sand habitats, but their applicability across a range of pressures and habitats is less well understood. The ability of the indices to predict changes in response to pressures in three distinct habitats, intertidal muddy sand, maerl and inshore gravel, was tested using pre-existing datasets. Both responded following the same patterns of variation as previously reported. The IQI was more conservative when responding to environmental conditions so may have greater predictive value in dynamic habitats to provide an early-warning system to managers’. Re-calibration of reference conditions is necessary to reliably reflect ES in different habitats.

Intertidal and nearshore Nereididae (Annelida) of the Falkland Islands, southwestern Atlantic, including a new species of Gymnonereis.

The intertidal and nearshore Nereididae of the Falkland Islands are detailed and a new species of Gymnonereis described. The new species, Gymnonereis tenera sp. n., is the first record of the genus for the Falkland Islands. It is, so far, only known from a few intertidal locations in fine and muddy sands. Main distinguishing characters are: jaw teeth absent (in adults), 3 papillae in Area V–VI, falcigers absent, second ventral cirrus present throughout. Nereis atlantica McIntosh, 1885, known only from the description of a single specimen and one doubtful record from the Falkland Islands, is reviewed and transferred to Perinereis on the basis of the presence of shield-shaped bars in Area VI of the proboscis and the absence of notopodial falcigers. A key to all seven species discussed is provided.

Similar diversity-disturbance responses to different physical impacts: Three cases of small-scale biodiversity increase in the Belgian part of the North Sea

Human activities at sea are still increasing. As biodiversity is a central topic in the management of our seas, it is important to understand how diversity responds to different disturbances related with physical impacts. We investigated the effects of three impacts, i.e. sand extraction, dredge disposal and offshore wind energy exploitation, on the soft-bottom macrobenthic assemblages in the Belgian part of the North Sea. We found similar diversity-disturbance responses, mainly related to the fact that different impacts caused similar environmental changes. We observed a sediment refinement which triggered a shift towards a heterogenic, dynamic (transitional) soft-bottom macrobenthic assemblage, with several species typically associated with muddy sands. This led to a local unexpected biodiversity increase in the impacted area. On a wider regional scale, the ever increasing human impacts might lead to a homogenization of the sediment, resulting in a more uniform, yet less diverse benthic ecosystem.

Occurrence and activity of anammox bacteria in surface sediments of the southern North Sea

We investigated the occurrence and activity of anaerobic ammonia oxidation (anammox) bacteria in sandy and muddy sand sediments of the southern North Sea. The presence of anammox bacteria was established through the detection of specific phosphocholine-monoether ladderane lipids, 16S rRNA gene, and hydrazine synthase (hzsA) genes. Anammox activity was measured in intact sediment cores (in situ rate) and in sediment slurries (potential rate) as the rate of N2 evolution from (15) N-labeled substrates and compared to the transcriptional activity of genes of anammox bacteria. The contribution of anammox to N2 production ranged between 0% and 29%. The potential rate of anammox agreed well with the abundance of anammox bacteria 16S rRNA and hzsA gene copies and the transcriptional activity of the anammox bacteria 16S rRNA gene. We found a higher abundance and activity of anammox bacteria in sediments with higher organic carbon content and also higher activity in summer than in winter. The abundance of anammox bacteria and their potential anammox rates were similar to those reported for other marine coastal sediments, suggesting that potentially they are important contributors to the nitrogen cycle in sandy sediments of shallow continental shelf areas.