Substratum as a structuring influence on assemblages of Arctic bryozoans

The nature of the substratum is a fundamental factor determining the types of organisms and communities found in many terrestrial and benthic habitats. The extent to which this is true in extreme environments was investigated using bryozoan assemblages as model organisms in an Arctic fjord (Kongsfjorden 79°N, 12°E) in summer 2001 using SCUBA. Twenty-seven substrate samples of 0.25 m² were taken at 10 m depth from the inner glacial basin to the mouth of the fjord. Multivariate analyses revealed four different bryozoan assemblages. The sea floor of the inner basin of Kongsfjorden near the glacial fronts was characterized by low diversity and dominance of the ctenostome species Alcyonidium disciforme Smitt. Highest richness and diversity occurred on rock substratum with mean size >10 cm², on which the most common species was the pioneer Harmeria scutulata Busk (abundance: 15%). On smaller rocks with mean size <2 cm², the runner-like pioneer species Electra arctica Borg comprised most individuals of the assemblage (98%). Yet another pioneer, Celleporella hyalina Linnaeus, was the most abundant species (49%) on substratum dominated by algae. Thus, in each habitat type, pioneers dominated but different species and to different extents. There was much variation in species composition and abundance within assemblages of heterogeneous habitats, and this study emphasizes the importance of microhabitats and physical conditions. Heterogeneity was evident at scales of <1 m.     

Distribution patterns in the biomass of macrozoobenthic communities in Admiralty Bay (King George Island, South Shetlands, Antarctic)

The distribution patterns of macrozoobenthic communities as shown by the biomass of the higher taxa were investigated in Admiralty Bay. Material was collected at depths ranging from 4 to 500 m (102 quantitative samples), representing the full depth range of this basin and including areas characterized by the different levels of glacial influence. Five community groups were distinguished by multivariate analysis (clustering, MDS) based on the Bray--Curtis similarity index. In the Ezcurra Inlet, the area characterized by intensive glacial processes resulting in a high sedimentation rate, the distribution of biomass was not depth related, but was associated with the intensity of glacial disturbance along the axis of the fjord. The innermost part of this fjord, which receives strong outflows from glaciers, had a low biomass value (2.9 g/0.1 m²) and was dominated by polychaetes. The middle part of the fjord which is not so heavily disturbed had higher biomass values (46.1 g/0.1 m²) due to the dominance of bivalves. A clear depth gradient of biomass distribution was observed in bottom areas located far from glaciers, in the central basin of the bay, with three zones within the depth ranges 4–30, 40–380, and 400–500 m. The highest mean biomass values (92.5 g/0.1 m²) were found in the middle sublittoral (40–380 m) dominated by ascidians. In the shallow and deep assemblages, the biomass was lower (33.8 g/0.1 and 30.9 g/0.1 m² respectively), most probably associated with the ice disturbance in the shallows and lower food supply in the deepest part of the shelf.     

Ostracods in a cold-temperate coastal environment, Western Troms, Northern Norway: Sedimentary aspects and assemblages

Summary This study presents sedimentological and micropaleontological data on ostracods from a cold-temperate inner shelf setting in the Troms District, northern Norway. The coarse fraction analyses carried out on sediment surface samples from coastal platforms and adjacent outer fjord troughs reveal a considerable contribution from ostracods to the accumulation of skeletal carbonates in distinct depositional settings. Ostracod accumulation is highest along wave-sheltered areas of coastal platforms where fleshy seaweed and coralline algal communities thrive in 10 to 30 m water depth. Current-exposed slopes of outer fjord troughs show a highly mixed ostracod assemblage consisting of imported species from the shallow coastal platform which is mixed with the trough assemblage. The hydrodynamic transport of ostracods into deeper areas results from the strong tidal current regime. Because of this mixing process, only the end members, the coastal platform and the fjord trough assemblages can be defined. The former is characterized byBaffinicythere emarginata, Cythere lutea, Finmarchinella angulata, Hemicytherura clathrata, Robertsonites tuberculatus, Sclerochilus rudjakovi, Semicytherura undata andXestoleberis cf.depressa. The outer fjord trough assemblage is characterized byCluthia cluthae, Cytherella abyssorum, Cytheropteron alatum, Krithe cf.adelspergi, Muellerina abyssicola, Cytherella cf.vulgatella andCytheropteron testudo. Members of the northern Norwegian trough assemblage are known to occur in deeper open shelf environments of the NE-Atlantic.     

Controls on the distribution of calcareous Foraminifera in the Lower Carboniferous of Ireland

Microfacies analyses of thin sections from over 650 samples of Asbian and Brigantian (late Viséan) platform carbonates from Ireland shows that foraminiferal assemblages are controlled by the relative abundance of echinoderms (mainly crinoids), bryozoans and calcareous algae: Koninckopora, Ungdarella and palaeoberesellids. Archaediscidae, Valvulinella and Tetrataxidae thrived in algal-poor crinoid and bryozoan thickets at or below fair-weather wavebase. Late Viséan algal limestones contain abundant Endothyridae and Palaeotextulariidae, and are interpreted to have been deposited at depths between 5 and 10 m. The morphology of the Foraminifera studied is related closely to their facies distribution. Many taxa inhabited high energy shallow marine algal meadow facies, these include: Bibradya, Cribrospira, Nevillella and Bradyina with cribrate apertures and other specialised test features that protected the protoplasm from damage, Gigasbia, Omphalotis, Globoendothyra and Pseudoendothyra with large, rotund or keeled, multilayered tests and Forschiidae with large thick-walled tests. Infaunal taxa such as the Lituotubella, Nevillella, Gigasbia and the palaeotextulariids are recorded from algal facies and appear to have been unable to survive on bryozoan and crinoidal substrates. Pseudoammodiscus and Earlandia, characterized by simple morphologies and single layered walls, and Endothyranopsis, Endothyra and Eostaffella, planispirally coiled with multilayered micritic tests, are regarded as the least facies-controlled of the taxa studied. The encrusting nature of Pseudolituotuba and Scalebrina ensured survival in a wide range of platformal palaeoenvironments, though algal meadows were not generally suitable substrates for the Pseudolituotubidae. The secondary deposits in the umbilical region of the Asteroarchaediscinae may have been an adaptation for survival in the dense crinoidal bryozoan thickets where they lived. Delicate Planoarchaediscus occurs in algal-poor wackestone to packstone facies typical of low energy palaeoenvironments possibly at depths below 20 m. Howchinia, which occurs with Fasciella (a probable alga) in intraclastic wackestone facies may also have lived in water deeper than 20 m. Major changes in foraminiferal assemblages through the Asbian and Brigantian stages of the late Viséan are attributed to changes in associated biotic constituents. Early Asbian endothyrid and forschiid dominated assemblages were controlled by the relative abundance of bryozoans, Koninckopora and palaeoberesellids. By the late Asbian, the foraminiferal assemblages were controlled by the presence or absence of palaeoberesellids, Ungdarella and to a lesser extent bryozoans. Asbian assemblages were similar, although foraminifers such as bradyinids, Cribrospira and Globoendothyra became abundant in the late Asbian. A switch to predominantly echinoderm (mainly crinoid) and bryozoan substrates in the Brigantian may have caused the major change from late Asbian endothyrid and palaeotextulariid assemblages to archaediscid and tetrataxid dominated assemblages.     

Macrobenthic species composition and diversity in the Godthaabsfjord system, SW Greenland

The southwest Greenland coast is made up of large and deep sill fjords. On the shelf, a number of shallow banks separated by deep troughs are located 20–50 km from the coast. We collected three 0.1-m² van Veen grabs at nine stations along a transect spanning from the inner Godthaabsfjord influenced by glaciers, across the shallow Fyllas Bank and out to the slope of the continental shelf at approximately 1,000 m depth. Along this transect, we explored patterns of macrobenthic diversity, species composition, abundance and biomass. The sampled stations were very different in terms of environmental variables, resulting in large differences in species composition primarily related to differences in depth, silt–clay fraction and chl a content of the sediment (BIO-ENV analysis). Habitat differences also reduced species spatial ranges and the majority of species were found at only one (49%) or two (20%) stations and, consequently, species turnover or beta diversity was high and correlated to differences in depth, silt–clay fraction and median sediment grain size. Species richness and diversity were lowest in sites exposed to sediment disturbance: near the glaciers in the inner fjord (physical disturbance by mineral sedimentation) and at selected stations on the shelf (bioturbation by burrowing sand eel). Alpha diversity and richness were only weakly correlated to environmental parameters, indicating that alpha richness and diversity are influenced by several factors or that relationships are non-linear as was found for species richness and silt–clay fraction.     

Structure of bryozoan communities in an Antarctic glacial fjord (Admiralty Bay,South Shetlands)

Bryozoans are among the most important groups of the Southern Ocean benthic macrofauna, both in terms of species richness and abundance. However, there is a considerable lack of ecological research focused on their distribution patterns and species richness on smaller scale, especially in the soft bottom habitats of Antarctic glacial fjords. The aim of this study was to describe those patterns in the Admiralty Bay. Forty-nine Van Veen grab samples were collected at the depth range from 15 to 265 m, in the summer season of 1979/1980, at three sites distributed along the main axis of the fjord. Among 53 identified species of bryozoans, 32 were recorded in the Admiralty Bay for the first time. The most common and abundant species were Himantozoum antarcticum, Inversiula nutrix and Nematoflustra flagellata. Genera such as Arachnopusia, Cellarinella and Osthimosia were the most speciose taxa. It was demonstrated that depth was important for the distribution of the bryozoans. More than half of the recorded species were found only below 70 m. An influence of glacial disturbance was reflected in the dominance structure of colony growth-forms. The inner region of the fjord was dominated almost entirely by encrusting species, while the diversity of bryozoan growth-forms in less disturbed areas was much higher. In those sites the highest percentage of branched, tuft like species represented by buguliform and flustriform zoaria was observed.     

Monthly to interannual variability of microbial eukaryote assemblages at four depths in the eastern North Pacific

The monthly, seasonal and interannual variability of microbial eukaryote assemblages were examined at 5 m, the deep chlorophyll maximum, 150 m and 500 m at the San Pedro Ocean Time-series station (eastern North Pacific). The depths spanned transitions in temperature, light, nutrients and oxygen, and included a persistently hypoxic environment at 500 m. Terminal restriction fragment length polymorphism was used for the analysis of 237 samples that were collected between September 2000 and December 2010. Spatiotemporal variability patterns of microeukaryote assemblages indicated the presence of distinct shallow and deep communities at the SPOT station, presumably reflecting taxa that were specifically adapted for the conditions in those environments. Community similarity values between assemblages collected 1 month apart at each depth ranged between ∼20% and ∼84% (averages were ∼50–59%). The assemblage at 5 m was temporally more dynamic than deeper assemblages and also displayed substantial interannual variability during the first ∼3 years of the study. Evidence of seasonality was detected for the microbial eukaryote assemblage at 5 m between January 2008 and December 2010 and at 150 m between September 2000 and December 2003. Seasonality was not detected for assemblages at the deep chlorophyll a maximum, which varied in depth seasonally, or at 500 m. Microbial eukaryote assemblages exhibited cyclical patterns in at least 1 year at each depth, implying an annual resetting of communities. Substantial interannual variability was detected for assemblages at all depths and represented the largest source of temporal variability in this temperate coastal ecosystem.     

Patterns of hydroid (Cnidaria, Hydrozoa) species richness and distribution in an Arctic glaciated fjord

The consequences of global warming are particularly evident in high polar areas. Deglaciation phenomenon—negative mass balance of Svalbard glaciers and recession of tidal glaciers—results in landscape and shoreline change. These areas of very dynamic conditions are now open for primary colonists, among them hydroids, typical early colonists of the vacant substratum. This study aims to explore the patterns of Hydrozoan diversity and distribution in Hornsund (west Spitsbergen). Hydroids associated with shallow water kelp beds as well as those occurring on deeper subtidal soft bottom were collected at sites located along gradients of glacial disturbance (i.e., high mineral sedimentation, ice-berg scouring). Samples were collected by scuba diving (three sites of different distance to active tidal glaciers), van Veen grabs (two sites located in the inner and outer fjord basin), and dredges taken from along a fjord transect. Hydroid diversity differed significantly between sites located in the vicinity of glaciers fronts in glaciated bays and sites comparatively free from glacier disturbance. Glacial disturbance results in low frequencies of occurrence and high levels of rarity of hydroids at sites located close to glacier fronts. The species richness of hydroids colonizing the hard substrate elements present in deeper subtidal decreases along the fjord axis (i.e., along the glacial sedimentation gradient).     

The surface ocean productivity response of deeper water benthic foraminifera in the Atlantic Ocean

We test the relationship of deep sea benthic foraminiferal assemblage composition to the surface ocean productivity gradient in the low latitude Atlantic Ocean using 81 surface sediment samples from a water depth range between 2800 and 3500 m. The samples are selected so that the surface ocean productivity gradient, controlling the flux of organic carbon to the seabed, will be the most important environmental variable. The first two principal components of the assemblage data account for 73% of data variance and are clearly linked to the productivity gradient across the Atlantic. These components show that under higher productivity the assemblages contain a higher abundance of Uvigerina peregrina, Melonis barleeanum, Globobulimina spp. and other taxa with probable infaunal microhabitats. Alabaminella weddellensis, a species linked to episodic phytoplankton debris falls, is also important in these assemblages. As productivity decreases there is a regular shift in assemblage composition so that low productivity assemblages are dominated by Globocassidulina subglobosa and several Cassidulina species along with Epistominella exigua. We hypothesize that these taxa are epifaunal to very shallow infaunal since nearly all organic carbon oxidation occurs near the sediment-water interface in low productivity settings. Discriminant function analysis of the foraminiferal assemblages, with groups selected on the basis of surface ocean productivity, shows clear separation among five productivity levels we used. This analysis demonstrates that productivity variations have a strong influence on assemblage composition. Finally, we used two groups of samples from the Rio-Grande Rise representing water depths from 2007 to 2340 m and 2739 to 3454 m to test for effects produced by changing water depth. All these samples are from a low productivity region and represent nearly identical environmental conditions. Although the low productivity nature of all the Rio-Grande Rise samples is obvious, there are assemblage differences between our depth groups. We cannot account for the assemblage differences with changes in organic carbon flux, dissolution effects or other physical/chemical properties of the ocean. Thus there are as yet unidentified factors related to water depth which cause some assemblage variation in the low productivity setting we investigated.     

Changes in fossil chironomid remains along a depth gradient: evidence for common faunal thresholds within lakes

Many environmental variables that are important for the development of chironomid larvae (such as water temperature, oxygen availability, and food quantity) are related to water depth, and a statistically strong relationship between chironomid distribution and water depth is therefore expected. This study focuses on the distribution of fossil chironomids in seven shallow lakes and one deep lake from the Plymouth Aquifer (Massachusetts, USA) and aims to assess the influence of water depth on chironomid assemblages within a lake. Multiple samples were taken per lake in order to study the distribution of fossil chironomid head capsules within a lake. Within each lake, the chironomid assemblages are diverse and the changes that are seen in the assemblages are strongly related to changes in water depth. Several thresholds (i.e., where species turnover abruptly changes) are identified in the assemblages, and most lakes show abrupt changes at about 1–2 and 5–7 m water depth. In the deep lake, changes also occur at 9.6 and 15 m depth. The distribution of many individual taxa is significantly correlated to water depth, and we show that the identification of different taxa within the genus Tanytarsus is important because different morphotypes show different responses to water depth. We conclude that the chironomid fauna is sensitive to changes in lake level, indicating that fossil chironomid assemblages can be used as a tool for quantitative reconstruction of lake level changes.     

Vertical gradients in species richness and community composition across the twilight zone in the North Pacific Subtropical Gyre

Although metazoan animals in the mesopelagic zone play critical roles in deep pelagic food webs and in the attenuation of carbon in midwaters, the diversity of these assemblages is not fully known. A metabarcoding survey of mesozooplankton diversity across the epipelagic, mesopelagic and upper bathypelagic zones (0–1500 m) in the North Pacific Subtropical Gyre revealed far higher estimates of species richness than expected given prior morphology‐based studies in the region (4,024 OTUs, 10‐fold increase), despite conservative bioinformatic processing. Operational taxonomic unit (OTU) richness of the full assemblage peaked at lower epipelagic–upper mesopelagic depths (100–300 m), with slight shoaling of maximal richness at night due to diel vertical migration, in contrast to expectations of a deep mesopelagic diversity maximum as reported for several plankton groups in early systematic and zoogeographic studies. Four distinct depth‐stratified species assemblages were identified, with faunal transitions occurring at 100 m, 300 m and 500 m. Highest diversity occurred in the smallest zooplankton size fractions (0.2–0.5 mm), which had significantly lower % OTUs classified due to poor representation in reference databases, suggesting a deep reservoir of poorly understood diversity in the smallest metazoan animals. A diverse meroplankton assemblage also was detected (350 OTUs), including larvae of both shallow and deep living benthic species. Our results provide some of the first insights into the hidden diversity present in zooplankton assemblages in midwaters, and a molecular reappraisal of vertical gradients in species richness, depth distributions and community composition for the full zooplankton assemblage across the epipelagic, mesopelagic and upper bathypelagic zones.     

Free-living nematodes and macrobenthos in a high-latitude glacial fjord

Kongsfjord is an open glacial fjord on the west coast of Svalbard, where the influence of the West Spitzbergen current ameliorates the effects of high latitude (79°N). The fjord is heavily influenced by glacial discharges of meltwater, ice and till, and related environmental gradients in sediments from the glaciers to the open sea include sediment deposition, organic content and disturbance. Other factors, such as the formation and break up of sea ice, also affect benthic communities. In this study spatial patterns in nematode and macrofaunal communities, in samples collected using box-corers and van Veen grabs during a cruise in September 1997, are described, compared and contrasted. Non-parametric multivariate analyses demonstrate that there were clear differences in community structure between stations in both macrofaunal and nematode assemblages. At stations where macrofauna were sampled using both box-cores and grabs there were also significant differences between samples collected by different methods, although there is evidence that these were influenced in part by slight differences in sampling location. Some evidence of disturbance to macrofaunal assemblages in the centre of the fjord is apparent. Macrofaunal community composition varied most closely with a combination of depth and sediment C : N ratio, whereas that of nematodes varied most closely with C : N alone. Proportions of feeding groups of nematodes showed little variation along the fjord. There is no evidence of a specialised nematode assemblage inhabiting the part of the fjord subject to the heaviest deposition of sediment. The taxonomic distinctness of nematodes decreased with increasing distance from the source of disturbance. This is in contrast to studies showing that the taxonomic distinctness of nematodes tends to decrease with increasing anthropogenic stress.     

Consistent patterns in diatom assemblages and diversity measures across water‐depth gradients from eight Boreal lakes from north‐western Ontario (Canada)

1. Until recently, the distribution of diatom species assemblages and their attributes (e.g. species richness and evenness) in relation to water depth have been identified but not quantified, especially across several lakes in a region. Here, we examined diatom assemblages in the surface sediment across a water‐depth gradient in eight small, boreal lakes in north‐western Ontario, minimally disturbed by human activities. 2. Surface‐sediment diatom assemblages were collected within each lake along a gentle slope from near‐shore to the centre deep basin of the lake, at a resolution of ～1 m water depth. Analysis of sedimentary samples provided an integrated view of assemblages that were living in the lake over several years and enabled a high‐resolution analysis of many lakes. The study lakes ranged in water chemistry, morphology and size and are located along an east–west transect approximately 250 km long in north‐western Ontario (Canada). 3. The majority of diatom species were distributed along a continuum of depth, with those taxa having similar habitat requirements forming distinct, though overlapping, assemblages. Three major zones of diatom assemblages in each lake were consistently identified: (i) a near‐shore assemblage of Achnanthes (sensu lato), Nitzschia, Cymbella (sensu lato) and other benthic species; (ii) a mid‐depth assemblage of small Fragilaria (sensu lato)/small Aulacoseira and various Navicula taxa; and (iii) a deep‐water assemblage of planktonic origin (mainly Discotella spp.). 4. The depth of the transition between assemblage zones varied between the eight lakes. The boundary between the deep‐water planktonic zone and the mid‐depth benthic zone varied according to water chemistry and was probably related to light attenuation. The boundary was deeper in lakes with the lower dissolved organic carbon and total phosphorus (TP) (i.e. less light attenuation) and vice versa. 5. Generally, species richness, species evenness and turnover rate of species as a function of depth were significantly lower in the planktonic assemblage zone in comparison with the two zones nearer the shore. Reproducibility of species and assemblage distributions across the depth gradient of the lakes illustrated that, despite potential for sediment transport, detailed ecological characterisation of diatom species can be gleaned from sedimentary data. Such data are often lacking, particularly for near‐shore benthic species.     

Larger foraminifera as a substratum for encrusting bryozoans (Late Oligocene,Tethyan Seaway,Iran)

Considering the diversity and abundance of larger foraminifera examined from a wide range of Late Oligocene to Early Miocene palaeoenvironments in the Tethyan Seaway, encrusting bryozoans make extremely little use of their tests as substratum. Significant encrustations by bryozoans were exclusively found on large (ø c. 6 cm), undulating tests of Lepidocyclina spp., on which, however, a remarkable 34 taxa of encrusting bryozoans were recorded. This shallow-water fauna of Chattian age was analyzed in respect of the bryozoan taxa present, colony growth type, and mode of budding, colony size, as well as onset of reproduction. Taxic and morphological similarities between the fossil assemblage and modern faunas encrusting mobile substrata indicate a long history of bryozoans as part of the interstitial habitat, while the tests of certain larger foraminifera may have played a significant role in the evolution of shallow-water bryozoans by providing substrata for encrusting species in otherwise unfavorable environments.     

Patterns of taxonomic diversity and relatedness among native and non-indigenous bryozoans

Aim The likelihood of a species successfully passing through all stages of the human‐mediated invasion process and becoming established at new locations is often determined by phenotypic characteristics. Among species, phenotypic similarity is negatively correlated with phylogenetic distance, but examples of independent evolution of traits in unrelated taxa do exist. Using marine bryozoans as model organisms we predict that, given the selectivity of the invasion process, the phylogenetic relatedness among established non‐indigenous species in a region is either higher or lower than that among the native assemblage, but not the same. Location Sixteen port and marina environments around New Zealand (the principal sites of establishment of most non‐indigenous bryozoans), and coastal habitats of the entire New Zealand coastline. Methods We use average taxonomic distinctness (avTD) as a measure of phylogenetic relatedness and taxonomic ‘breadth’ of species assemblages. We compare values of avTD between native and non‐indigenous bryozoan assemblages at two spatial scales and examine whether assemblages in port environments represent phylogenetically restricted and morphologically distinct subsets of the regional coastal bryofauna. Results At a nationwide and a local scale, the phylogenetic relatedness among non‐indigenous bryozoans was no different from that among members of the native assemblage. However, native bryozoans inhabiting port and marina environments had a significantly reduced taxonomic breadth and higher phylogenetic relatedness than the pool of ‘available’ native bryozoans from surrounding coastal habitats. Non‐indigenous species were on average six times more prevalent than native species in ports. There were no differences in morphological characteristics between native and non‐indigenous bryozoans from ports and natural environments. Main conclusion We found no evidence that a successful passage through the stages of the invasion process results in a taxonomically distinct non‐indigenous assemblage. However, patterns of relatedness among native and among non‐indigenous species may be influenced by the nature of the study environment.     

Epilithozoan fauna associated with ferromanganese crustgrounds on the continental slope segment between Capri and Li Galli Islands (Bay of Salerno, Northern Tyrrhenian Sea, Italy)

The epilithozoan fauna associated with Quaternary Fe–Mn crustgrounds sampled off Capri and Li Galli Islands is described. During the Quaternary, the interplay among the tectonically induced topography, sea-current patterns, and the changing physical-chemical properties of the water column promoted conditions favouring Fe–Mn oxide accumulation. In the samples dredged between 510–263 m depth (DRA 7), 207–201 m depth (DRA 5) and 358–65 m depth (DRA 4), where the Fe–Mn coating covers all rock surfaces, the distribution of the epilithozoan taxa is polarized: on the upper smooth surface of the crustgrounds the most abundant inhabitants are foraminifers, while on the lower rough surface corals, bivalves, bryozoans and brachiopods occur. Sponges are mainly able to bioerode the rough lower surfaces. Samples are riddled by boring ichnogenera including Entobia and Maeandropolydora. Fe–Mn oxide precipitation is still active today as shown by the frontal shield preservation of the bryozoan Puellina cf. pseudoradiata Harmelin and Aristegui, 1988, where it is possible to identify different stages of accretion. Botryoidal ongoing accretion is evident only in some taxa, namely Bryozoa and Polychaeta species, and Foraminifera morphotypes, which appear to keep pace with precipitation when it occurs.     

Early Ordovician bryozoans from north-western Russia

ABSTRACT. A bryozoan assemblage from the Billingen Stage of north-western Russia (Ingria) is apparently the oldest known in the world. It consists of six species distributed among the trepostomate genera Esthoniopora Dianulites, Revalotrypa Phragmophora and Hemiphragma . Two species are new: Phragmophora lavaense Pushkin, sp. nov. and Hemiphragma priscum Pushkin, sp. nov. The bryozoans are characteristic of the medium diversity benthic fauna of uncertain origin which migrated into the Baltic Basin during Billingen time (late Prioniodus elegans — early Oepikodus evae zones). The Billingen bryozoans have a close similarity to the late Arenig bryozoan faunas of Baltoscandia that are also dominated by trepostomates, but differ significantly from the low diversity late Arenig bryozoan assemblages of North America, Ireland, North China, Vajgach and Novaja Zemlja.     

Depth-related changes to density,diversity and structure of benthic megafaunal assemblages in the Fimbul ice shelf region,Weddell Sea,Antarctica

The depth-related patterns in the benthic megafauna of the NE Weddell Sea shelf at the edge of the Fimbul Ice Shelf were investigated at seven sites using towed camera platform photographs. Megafaunal density decreased with depth from 77,939 ha⁻¹ at 245 m to 8,895 ha⁻¹ at 510 m. While diversity was variable, with H′ ranging between 1.34 and 2.28, there were no depth related patterns. Multivariate analyses revealed two distinct assemblages; a shallow assemblage with dense patches of suspension feeders in undisturbed areas and a deep assemblage where these were not present. Disturbance from icebergs explained many observed patterns in faunal distribution. In shallow waters probable effects of disturbance were observed as changes in successional stages; in deeper waters changes in habitat as a result of past disturbance explained faunal distributions. In deeper areas ice ploughing created a mosaic landscape of fine and coarse sediments. Total megafaunal density was highest in areas of coarse sediment (up to 2.9 higher than in finer sediment areas) but diversity was highest in intermediate areas (H′ = 2.35).     

Distribution and environmental control of coral assemblages in northern Safaga Bay (Red Sea, Egypt)

Summary Coral assemblages in northern Safaga Bay, Red Sea, Egypt, are qualitatively described. Nine distinct assemblages were found, which correspond to quantitatively defined community types previously described from the area off Hurghada, northern Red Sea. Their distribution within northern Safaga Bay was mapped. Strong gradient and/or steep relief assemblages were:Acropora assemblage on windward (exposed) reefs,Porites assemblage on leeward (sheltered) reefs,Millepora assemblage on current exposed reefs,Stylophora assemblage on reef flats. Low gradient and/or low relief assemblages were:Acropora dominated coral patches in areas of good circulation to a depth of 15 m,Stylophora/Acropora coral patch assemblages in shallow sheltered environments, faviid carpet in low relief areas between 10 and 25 m which with increasing turbidity turns into a depauperate faviid carpet,Porites carpet in low relief areas between 5 and 15 m with clearest water,Sarcophyton carpet in low relief areas with high suspension load, platy scleractinian assemblage in deeper water (>25 m) with low light intensity. The distribution of coral assemblages depends basically on 1) topography 2) hydrodynamics 3) light and 4) suspension load.     

Oyster Reef Restoration in the Northern Gulf of Mexico: Effect of Artificial Substrate and Age on Nekton and Benthic Macroinvertebrate Assemblage Use

In the northern Gulf of Mexico (GOM), reefs built by eastern oysters, Crassostrea virginica, provide critical habitat within shallow estuaries, and recent efforts have focused on restoring reefs to benefit nekton and benthic macroinvertebrates. We compared nekton and benthic macroinvertebrate assemblages at historic, newly created (<5 years) and old (>6 years) shell and rock substrate reefs. Using crab traps, gill‐nets, otter trawls, cast nets, and benthic macroinvertebrate collectors, 20 shallow reefs (<5 m) in the northern GOM were sampled throughout the summer of 2011. We compared nekton and benthic assemblage abundance, diversity and composition across reef types. Except for benthic macroinvertebrate abundance, which was significantly higher on old rock reefs as compared to historic reefs, all reefs were similar to historic reefs, suggesting created reefs provide similar support of nekton and benthic assemblages as historic reefs. To determine refuge value of oyster structure for benthic macroinvertebrates compared to bare bottom, we tested preferences of juvenile crabs across depth and refuge complexity in the presence and absence of adult blue crabs (Callinectes sapidus). Juveniles were more likely to use deep water with predators present only when provided oyster structure. Provision of structural material to support and sustain development of benthic and mobile reef communities may be the most important factor in determining reef value to these assemblages, with biophysical characteristics related to reef location influencing assemblage patterns in areas with structure; if so, appropriately locating created reefs is critical.