Soft-bottom Habitats Research Articles

Pseudopataecus carnatobarbatus, a new species of velvetfish (Teleostei: Scorpaeniformes: Aploactinidae) from the Kimberley coast of Western Australia

Pseudopataecus carnatobarbatus, new species, is described from 12 specimens collected on shallow coastal reefs of northernWestern Australia, between the Monte Bello Islands and Adele Island. It is distinguished from its sole congener, P. taenianotusJohnson 2004, by branched (versus simple) tips to most fin rays, last soft dorsal-fin ray joined by membrane more fully toupper caudal-fin ray, spinous dorsal fin more distinctly notched, pelvic fins more robust, anterior face of lower lip smooth (ver-sus profusely covered with cirri), and a narrow quadrangular pit on the forehead, bounded by frontal, supraorbital, ocular andpreocular ridges (versus pit and preocular ridge absent). It also has modally fewer anal-fin rays and modally greater numbers ofgill rakers. Pseudopataecus carnatobarbatus is found in an extremely high tidal range area of Australia, where movement of upto 11 m occurs during spring tides. Specimens were collected in rocky tide pools with coral rubble and thick stands of brownmacroalgae, especially Padina species. The new species has been found in intertidal areas up to only 13 m deep, whereas P. taenianotus has been collected by trawling soft bottom habitats in depths of 20 to 63 m.

First record of Spurilla neapolitana (Mollusca: Nudibranchia: Aeolidiidae) on the central coast of Peru (Humboldt Current Upwelling Ecosystem)

Members of the genus Spurilla are nudibranchs with circumtropical distribution. Spurilla neapolitana is reported for the first time inhabiting subtidal soft-bottom habitats of the central coast of Peru. Adult specimens were found in Bahia Ferrol (09°04′S 78°35′W) at 10 m depth in November of 2009. Spurilla neapolitana is characterized by the presence of a long body with numerous cerata along the dorsal side of the body and a distinctive orange colouring with white dots. This finding extends the geographical range of Spurilla spp. into the south-eastern Pacific and adds a new contribution to the macro-mollusc diversity thriving in the Humboldt Current Upwelling Ecosystem.

Bedload Transport of Newly-Settled Juveniles of the Manila ClamRuditapes philippinarumObservedin situat Banzu Tidal Flat, Tokyo Bay

There have been numerous attempts to create and/or develop harvestable tidal areas where juveniles of the natural Manila clam Ruditapes philippinarum may be abundantly stocked. To prevent erosion and/or promote the colonization of natural juveniles through improving the physical stability of bottom sediment, it is important to understand the mechanisms that regulate dispersal and recolonization of benthic juveniles. The physical transport of bottom sediment is known to have a substantial effect on the spatial distribution patterns of infaunal bivalves in intertidal soft-bottom habitats. During the summers of 2004 and 2005, we conducted field experiments to identify the physical transport mechanisms for newly-settled postlarval Manila clams until growth to a size of 1 mm shell length at the Banzu tidal flat of Tokyo Bay in Japan. We used sediment traps to collect natural and released hatchery-reared juveniles, in parallel to acquiring measurements of seawater flow and observations of the spatial distribution of newly-settled natural juveniles. There was a sharp increase in the number of clams that were collected in the traps placed on the soft-bottom surface when τw (wave shear stress) exceeded 0.3 N m-2. Because the τc (advection shear stress) was far lower than τw (τc/τw =1/60–1/130), the initiation of juvenile transport appeared to depend primarily on wave-generated oscillatory flow. The number of trapped juveniles regressed linearly to the weight of the sediment that was simultaneously collected in the trap (R2 = 0.99, 0.81), which indicated that clams were transported in a similar way to that of sediment grains, despite juveniles and sand particles exhibiting different physical properties (size and specific gravity). Hence bedload transport may have resulted from the biologically induced adhesion of juvenile clams to sediment grains and/or their burrowing behavior. In the release-recovery experiment of marked juveniles, a larger number of clams were recovered from traps that had been placed downstream of the water current from the release point. A denser distribution of the natural Manila clam population settled in mid-July 2004, and subsequently moved several hundreds of meters inshore within a one month period. The concurrent monitoring of bottom flow during a total 4 wk period in the summer of 2004 indicated that τw frequently exceeded the incipient threshold of bedload transport (assumed to be 0.3 N m-2). Consequently, the bedload movement of Manila clam juveniles in the study area was expected to be initiated at a wave shear stress that was greater than the incipient threshold, and in a downstream direction of the advection current. Because juvenile clams in the summer population appeared to be frequently subjected to hydrodynamic stress, which forces juveniles to move and halt incidentally in the early benthic stages, physical transport is likely to contribute to the changing pattern of juvenile distribution at the Banzu tidal flat of Tokyo Bay in Japan.

Effect of vertical planktonic distribution of competent larvae on spat location in a soft-bottom intertidal zone: A case study for the softshell clam ( Mya arenaria) and the blue mussel ( Mytilus edulis)

Larval behavior and hydrodynamics may affect the vertical distribution of planktonic larvae and, in turn, spat location in the intertidal zone. This study describes the vertical profile of competent larvae in the water column and the distribution of spat on soft-bottoms, and quantifies the relationship between both distributions for the softshell clam ( Mya arenaria) and the blue mussel ( Mytilus edulis). Sampling was carried out in 2007 and 2008 along the coast of New Brunswick (Canada) in two tidally contrasted regions: Bay of Fundy (high tidal amplitude) and Northumberland Strait (low tidal amplitude). The planktonic larvae were collected with a pump at three depths. Spats were collected directly from the top layer of sediments as well as with two types of collectors. Sampling in the Bay of Fundy site took the day/night cycle into account. The distribution of planktonic larvae and spats in the intertidal zone was highly variable for both species. Overall, no general pattern in the larvae distribution was observed. The day/night cycle did not affect the distribution and abundance of planktonic larvae and spats. Only a few statistically significant relationships were observed between the abundance of spats in the intertidal zone and the abundance of planktonic larvae. Soft-bottom habitats are highly unstable and this characteristic may explain, in part, the absence of relationship between spat location and the vertical profile of planktonic larvae.

Direction of evolution within Annelida and the definition of Pleistoannelida

The direction of evolution within Annelida has been a long and contentious debate since the middle of the last century. Based on functional morphology two hypotheses were predominantly discussed. The first hypothesis proposed an earthworm-like ancestor and the evolution of a segmented coelom as an aid for peristaltic burrowing, whereas the second one postulated that the ancestral annelid resembled more an errant polychaete and the segmented coelom evolved as a requirement for blood transportation to the parapodia. A recent phylogenomic study of annelids as well as new fossil records of early annelids provide new insights to this debate, which will be discussed in this paper. Based on these data the ancestral annelid is most likely a mixture of sedentary and errant annelid features indicating an evolutionary origin of Annelida as a microphagous surface deposit-feeder crawling upon and through soft-bottom habitats. Hence, the evolution of iterative parapodia as locomotive devices most likely drove the evolution of segmentation in Annelida. Moreover, as Struck et al. (2011) did not provide a proper definition and name for their clade 1 this clade shall be named Pleistoannelida and is defined by the last common ancestor of Sedentaria and Errantia sensu Struck et al. (2011), and all the descendants of that ancestor.

Gradient effects on structuring of soft-bottom benthic infauna: Macoma balthica and predation, recruitment, and food availability

Infaunal benthic community structure can be affected by factors that operate locally (e.g., predation, competition, and disturbance) and regionally (e.g., recruitment, nutrient delivery). To determine the mechanisms driving distribution of a dominant infaunal clam, Macoma balthica, along a salinity (i.e., stress) gradient in the York River, Chesapeake Bay, I experimentally examined the effects of predation, recruitment, and food availability in shallow, subtidal, soft-bottom habitats. Specifically, in upriver and downriver zones I quantified: (1) the abundance of M. balthica; (2) the effect of predation on survival of M. balthica; (3) the abundance and foraging efficiency of major epibenthic predators; (4) the recruitment of M. balthica; and (5) the food availability for clams (sedimentary carbon). Consumer stress models predict that predators are more stressed in zones where salinity is lower and more variable (i.e., upriver); thus, predator-induced mortality should be lower upriver, potentially elevating the density of infaunal prey. In contrast to these models, in the York River, (1) natural abundance of M. balthica was higher upriver, (2) both predation-induced mortality in manipulative field experiments as well as field measurements of natural mortality of clams over time were higher upriver, though per capita foraging efficiency was lower, (3) predator abundance but not size was greater upriver where predation intensity was higher, (4) recruitment was lower upriver, and (5) food availability (sedimentary carbon) was greater upriver. Clam density, environmental stress, and per capita foraging efficiency were in accord with a consumer stress model of community regulation, whereas higher predator abundance and predation intensity in zones of higher environmental stress were contrary to the model's predictions. Recruitment did not dictate overall patterns of clam abundance, but habitat quality and nutrients appeared to drive prey and predator abundances. The patterns in this soft-bottom community are explained best by a productivity model, as reflected in a community governed principally by resource availability (i.e., bottom–up control), at a broad scale. This research suggests that structuring forces are similar for rocky intertidal, salt marsh, and soft-bottom communities at broad spatial scales.

Regenerative capacity and biochemical composition of the sea star Luidia clathrata (Say) (Echinodermata: Asteroidea) under conditions of near-future ocean acidification

The present study examines sublethal effects of near-future (year 2100) ocean acidification (OA) on regenerative capacity, biochemical composition, and behavior of the sea star Luidia clathrata, a predominant predator in sub-tropical soft-bottom habitats. Two groups of sea stars, each with two arms excised, were maintained on a formulated diet in seawater bubbled with air alone (pH 8.2, approximating a pCO2 of 380μatm) or with a controlled mixture of air/C02 (pH 7.8, approximating a pCO2 of 780μatm). Arm length, total body wet weight, and righting responses were measured weekly. After 97days, a period of time sufficient for 80% arm regeneration, pyloric caecal indices, and protein, carbohydrate, lipid, and ash levels were determined for body wall and pyloric caecal tissues of intact and regenerating arms of individuals held in both seawater pH treatments. The present study indicates that predicted near-term levels of ocean acidification (seawater pH 7.8) do not significantly impact whole animal growth, arm regeneration rates, biochemical composition, or righting behavior in this common soft bottom sea star.

Phosphoproteome analysis during larval development and metamorphosis in the spionid polychaete Pseudopolydora vexillosa

BackgroundThe metamorphosis of the spionid polychaete Pseudopolydora vexillosa includes spontaneous settlement onto soft-bottom habitats and morphogenesis that can be completed in a very short time. A previous study on the total changes to the proteome during the various developmental stages of P. vexillosa suggested that little or no de novo protein synthesis occurs during metamorphosis. In this study, we used multicolor fluorescence detection of proteins in 2-D gels for differential analysis of proteins and phosphoproteins to reveal the dynamics of post-translational modification proteins in this species. A combination of affinity chromatography, 2D-PAGE, and mass spectrometry was used to identify the phosphoproteins in pre-competent larvae, competent larvae, and newly metamorphosed juveniles.ResultsWe reproducibly detected 210, 492, and 172 phosphoproteins in pre-competent larvae, competent larvae, and newly metamorphosed juveniles, respectively. The highest percentage of phosphorylation was observed during the competent larval stage. About 64 stage-specific phosphoprotein spots were detected in the competent stage, and 32 phosphoproteins were found to be significantly differentially expressed in the three stages. We identified 38 phosphoproteins, 10 of which were differentially expressed during metamorphosis. These phosphoproteins belonged to six categories of biological processes: (1) development, (2) cell differentiation and integrity, (3) transcription and translation, (4) metabolism, (5) protein-protein interaction and proteolysis, and (6) receptors and enzymes.ConclusionThis is the first study to report changes in phosphoprotein expression patterns during the metamorphosis of the marine polychaete P. vexillosa. The higher degree of phosphorylation during the process of attaining competence to settle and metamorphose may be due to fast morphological transitions regulated by various mechanisms. Our data are consistent with previous studies showing a high percentage of phosphorylation during competency in the barnacle Balanus amphitrite and the bryozoan Bugula neritina. The identified phosphoproteins may play an important role during metamorphosis, and further studies on the location and functions of important proteins during metamorphosis are warranted.

Environmentally associated spatial changes of a macrozoobenthic community in the Saemangeum tidal flat, Korea

Estuarine tidal flats are both ecologically and economically important, hence developing methods to reliably measure ecosystem health is essential. Because benthic fauna play a central role in the food web of tidal flats, in this study we set out to quantitatively describe the intertidal zonation of macro-invertebrates and their associations with specific environmental parameters along three transects in the Saemangeum tidal flat, Korea. The abundance and biomass of intertidal fauna with respect to five environmental parameters (i.e., shore level, mud content, coarse sand content, water content, and organic content) were measured, to identify environmental factors that influence macrofaunal distribution in intertidal soft bottom habitats. A total of 75 species were identified, with dominant species showing distinct zones of distribution along all transects. The number of species recorded in each transect was found to be dependent on sediment characteristics and salinity. Cluster analysis classified the entire study area into three faunal assemblages (i.e., location groups), which were delineated by characteristic species, including (A) ‘ Periserrula–Macrophthalmus’, (B) ‘ Umbonium–Meretrix’, and (C) ‘ Prionospio–Potamocorbula’. Four environmental variables (i.e., shore level, water content, mud content, and organic content) appeared to determine factors that distinguished the three faunal assemblages, based on the discriminant analysis. The faunal assemblage types of the sampled locations were accurately predicted from environmental variables in two discriminant functions, with a prediction accuracy of 98%. It should be noted that the zonation of benthos in the lower section (C) of Sandong had been affected by the construction of a nearby dike, while this parameter had remained essentially unchanged at the other two location groups (A–B). Overall, the zonation of benthos from the Saemangeum tidal flat was explained adequately by the measured environmental variables, implying that faunal assemblages are closely associated with certain combinations of abiotic factors. The identification of such reliable associations may facilitate the development of statistical models to predict faunal distributions based on environmental variables at both local and regional scales. The entire study area was embanked in 2006 (one year after this study), and an integrated plan was set into force to develop claimed land into industrial, residential and agricultural districts, which also included a partial restoration program of the tidal flats located near to the study area.

Spatio-temporal variations in macrozoobenthic assemblage structures in a river-affected lagoon (Idoura Lagoon, Sendai Bay, Japan): Influences of freshwater inflow

Spatio-temporal changes in macrozoobenthic assemblage structure were monitored at 8 stations in a river-affected temperate lagoon (Idoura Lagoon, Japan) from May 1997 to May 1998 to assess animal–environment relationships in estuarine soft-bottom habitats. A total of 29 taxa occurred with a predominance of a few polychaete species including Heteromastus cf. similis, Hediste spp., Pseudopolydora cf. kempi and Prionospio japonica. The community structure differed significantly among four habitat types that were characterized by different salinity, sediment characteristics, and/or bottom elevation. For each habitat, macrozoobenthic community structure changed significantly with time, which was discriminated mostly by the lower density of polyhaline opportunistic species such as P. cf. kempi in warmer period. The salinity in the study area was much lower from May to September, mainly due to irrigation discharge from paddy fields, which seemed to be a lethal factor for the polyhaline species. C/N ratio and δ 13C value of the sediment implied the accumulation of river-derived organic matters during the high river flow period. Present results showed the significant effects of fluctuating river discharge on the estuarine soft-bottom habitats, suggesting a linkage among terrestrial, riverine and estuarine ecosystems.

A preliminary study on fish and macroinvertebrate enhancement in artificial reef area around Sanheng Isle, Shengsi, China

Fishes and macroinvertebrates(FM) were sampled respectively in ShangSanheng artificial reef area (marked by B) in May,Sept. of 2007 and Mar. ,May,Jul. of 2009 by trawl-net,and XiaSanheng artificial reef area(marked by A) from Jan. to Aug. of 2009 by multi-mesh gill-nets around Sanheng artificial reef waters,in order to assess resource enhancement effects of the deployed artificial reefs(ARs). Several control sites were chosen for better explanation on habitat restoration function by ARs. CPUE,Margalef species richness index,commercial species variation and Whilm species diversity index were used to discuss the change of FM resource. Result shows that:(1) A area: average CPUE’s significant differences were found neither between ARs and soft bottom habitat nor between ARs and rocky reef habitat(P 0. 05). However, the same index value from Feb. to Aug. between ARs and soft bottom habitat,was quite different(P 0. 05). Species richness level of ARs was obviously higher than that of the soft bottom habitat by 60. 2% (P 0. 05),no differences existed between ARs habitat and Rocky reef habitat(P 0. 05). Both ARs habitat and Rocky reef habitat share more commercial species than soft bottom habitat(P 0. 05),and they seemed to be equal by chance to attract commercial species(P 0. 05). As to species diversity,it was exactly the same as commercial species differences explained above,namely,which is equal between ARs habitat and Rocky reef habitat,and better than soft bottom habitat. (2) B area: CPUE in AR area was obviously improved by 2. 05 times after deployment(P 0. 05) and 2 times higher than that of control site(P 0. 05). Species richness level has been improved by 25. 3% after reef deployment,though no significant differences were found between them. However,it did have a better level than control site by 31. 3% higher(P 0. 05). 5 more commercial species were sampled in AR area after reef deployment compared to its original number(P 0. 05),and about 4 more species were sampled in AR area than control site after reefs were set. The diversity index in AR area has improved to a certain level,better than before and control site,though they appeared to be not so quite different(0. 05 P 0. 1). It is concluded that resource level and community structure have been improved a lot in both AR areas by comparison to its original level and control site level. The Sanheng artificial reefs have become a new habitat for more species and more individuals.

Biomass, Density, and Size Distributions of Fishes Associated with a Large-Scale Artificial Reef Complex in the Gulf of Mexico

The Freeport Sulphur Mine Artificial Reef (FSMAR) is a decommissioned oil and gas platform and serves as the largest artificial reef complex in the northern Gulf of Mexico (NGOM). Given the increasing numbers of artificial reefs in the NGOM, yet the paucity of information that exists, the goals of this study were to evaluate the biomass, density, and size structure of fishes associated with FSMAR. Mobile acoustic surveys were used to assess both horizontal and vertical distribution and abundance of fishes associated with the shallow water (16 m depth) reef complex and adjacent soft-bottom habitats extending 1 km from the reef complex. Highest acoustic estimates of fish biomass and density were found directly over the reef with a five-fold and 16-fold decrease at 10 and 30 m distances from the structure, respectively. In addition, fish biomass and density were highest in the bottom water column (> 10 m), followed by mid-water (6.1–10 m), and lowest in the upper water column (1.5–6 m). Findings suggest that fish distribution at the FSMAR is much greater than previously surveyed decommissioned oil and gas platforms and natural reef habitats in the NGOM. We consider the potential importance of this unique nearshore complex as an important habitat to fishes utilizing nearby estuarine and inner shelf systems in the NGOM.

Effects of wave energy converters on the surrounding soft-bottom macrofauna (west coast of Sweden)

Offshore wave energy conversion is expected to develop, thus contributing to an increase in submerged constructions on the seabed. An essential concern related to the deployment of wave energy converters (WECs) is their possible impact on the surrounding soft-bottom habitats. In this study, the macrofaunal assemblages in the seabed around the wave energy converters in the Lysekil research site on the Swedish west coast and a neighbouring reference site were examined yearly during a period of 5 years (2004-2008). Macrobenthic communities living in the WECs' surrounding seabed were mainly composed by organisms typical for the area and depth off the Swedish west coast. At both sites the number of individuals, number of species and biodiversity were low, and were mostly small, juvenile organisms. The species assemblages during the first years of sampling were significantly different between the Lysekil research site and the nearby reference site with higher species abundance in the research site. The high contribution to dissimilarities was mostly due to polychaetes. Sparse macrofaunal densities can be explained by strong hydrodynamic forces and/or earlier trawling. WECs may alter the surrounding seabed with an accumulation of organic matter inside the research area. This indicates that the deployment of WECs in the Lysekil research site tends to have rather minor direct ecological impacts on the surrounding benthic community relative to the natural high variances.

Proposals for aquatic reserves at Jervis Bay.

Jervis Bay is a large, marine-dominated embayment located about 180km by road to the south of Sydney. The Bay displays a wide array of ecosystems, such as subtidal rocky reefs, extensive seagrass beds, mangrove stands and a variety of soft-bottom habitats. In addition, Jervis Bay offers considerable amenity in terms of its scenic beauty, clear waters and predominantly undeveloped shores. Although these ecosystems are generally not unique, it is unusual to find such a large area containing a wide variety of aquatic and coastal habitats remaining relatively undisturbed despite its close proximity to several major urban centres. This situation can, at least in part, be attributed to the presence of the Royal Australian Navy, which owns and/or has used large tracts of land bordering the Bay for many years.

Phylogeography of the diamond turbot (Hypsopsetta guttulata) across the Baja California Peninsula

We compared morphology and sequenced nuclear and mitochondrial genes from 11 populations of a previously genetically unstudied “Baja California disjunct” species, the diamond turbot (Hypsopsetta guttulata). This species exhibits very limited adult movement and restriction to soft-bottom habitats but has a moderately long pelagic larval duration. Therefore, if pelagic larval duration is correlated with gene flow between Gulf of California and Pacific populations, we expect a reduced level of genetic and morphological differentiation. However, if adult habitat and ecology have more effect on gene flow, we expect the populations in the two bodies of water to be more highly differentiated. We used logistic regression to compare morphological features and phylogenetic and population genetic analyses to compare nucleotide sequence data. Gulf of California H. guttulata are different from Pacific populations in morphology and both mitochondrial and nuclear gene sequences. MtDNA shows reciprocal monophyly, and nuclear sequences from the Gulf of California formed a monophyletic group. Population genetic analyses also suggest further population subdivision within the Pacific and within the Gulf of California. We argue that adult ecology has a significant effect on migration rates among populations in the Pacific Ocean and the Gulf of California.

A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), from the eastern North Pacific

A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the eastern North Pacific. It is distinct from other eastern Pacific chimaeroids by the following characteristics: a large slightly curved dorsal fin spine extending beyond dorsal fin apex, a long second dorsal fin of uniform height throughout, large pectoral fins extending beyond the pelvic fin insertion when laid flat, trifid claspers forked for approximately one-quarter the total clasper length and a uniform black coloration throughout. The new species is compared to other eastern Pacific members of the genus Hydrolagus including H. alphus, H. colliei, H. macrophthalmus, and H. mccoskeri. Remote Operated Vehicle (ROV) video footage has identified and documented Hydrolagus melanophasma from the Gulf of California. ROV observations suggest that individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. This is in contrast to other eastern Pacific Hydrolagus species that tend to occur in areas of high rocky relief. The known distribution of this new species at present extends from southern California, U.S.A., along the Pacific coast of Baja California, Mexico, and into the Gulf of California.

Distances of dispersal of juvenile bivalves ( Mya arenaria (Linnaeus), Mercenaria mercenaria (Linnaeus) , Gemma gemma (Totten))

Although it is recognized that many species of benthic invertebrates continue to disperse after settlement, particularly in soft-bottom habitats, the scale over which movements of juveniles occur is not well known. This study combined laboratory flume experiments assessing the effects of clam size, species, and water velocity on rates and distances of dispersal of three species of juvenile bivalves with field measurements of loss rates and distances of dispersal of transplanted bivalves in the Navesink River estuary in New Jersey, USA. Dispersal distances measured in the laboratory ranged from an average of 1.6 to 40 cm h − 1 depending on clam size, species, and flow speed. Distances and likelihood of dispersal were generally greater for Mya arenaria than for Mercenaria mercenaria or Gemma gemma, although differences between species were not consistent. As predicted, smaller (1.3 mm) M. arenaria tended to disperse more than larger (3.7 mm) ones, although no significant differences were detected between two sizes (1.8 and 3.4 mm) of M. mercenaria. The similarity of the erosion thresholds of dead clams across sizes and species suggests that burrowing behaviour plays an important role in determining variation in dispersal due to clam size and species. In the field, densities of clams ( M . arenaria and M . mercenaria) were reduced to half of that in controls after 3.5–5 h, indicating high levels of dispersal and/or mortality. Some individuals were recovered up to 50 cm away from their initial locations. Overall, our results suggest that dispersal distances of these three species due to bedload transport are likely to be on the order of centimeters per hour. Although these dispersal distances are small, such movements are likely to occur frequently due to tidal currents and, consequently, may have profound impacts on patterns of abundance and distribution.

Density, biomass and productivity of small mobile invertebrates in a wide range of coastal habitats

Density, biomass and productivity of small (0.5 to 8.0 mm) mobile invertebrates were estimated within 34 diverse coastal habitats occurring along 80 km of coastline in temperate north- eastern New Zealand. These habitats ranged from the high shore to 20 m depth and included hard, soft and macroalgal substrates. The structurally complex and food-rich coralline algal turf and sandy beach seaweed wrack were the most densely populated and productive habitats, while intertidal sands tended to be most depauperate in mobile fauna. Temporal consistency in results was demon- strated for 4 habitats sampled seasonally for 2 yr. After adjusting for habitat extents, rankings of den- sity, biomass and productivity of fine-scale habitats amalgamated into broad-scale habitats were: sub- tidal rocky reef > intertidal rocky reef > subtidal soft sediments or intertidal estuary > sandy beach. Total productivity of mobile invertebrates was greater in hard- than soft-bottom habitats. Gastropods numerically dominated most hard-bottom habitats, and gammarid amphipods dominated most soft- bottom habitats. Communities of broad habitat types were reasonably discrete in multivariate space.

Epibenthic colonization of concrete and steel pilings in a cold-temperate embayment: a field experiment

With large-scale development of offshore wind farms, vertical structures are becoming more common in open water areas. To examine how vertical structures of different materials may be colonized by epibenthic organisms, an experiment was carried out using steel and concrete pilings constructed to resemble those commonly used in wind farm constructions as well as in bridges, jetties and oil platforms. The early recruitment and succession of the epibenthic communities were sampled once a month for the first 5 months and then again after 1 year. Further, the fish assemblages associated with the pillars were sampled and compared to natural areas. The main epibenthic species groups, in terms of coverage, differed between the two materials at five out of six sampling occasions. Dominant organisms on steel pillars were the barnacle Balanus improvisus, the calcareous tubeworm Pomatoceros triqueter and the tunicate Ciona intestinalis. On the concrete pillars, the hydroid Laomedea sp. and the tunicates Corella parallelogramma and Ascidiella spp. dominated. However, there was no different in coverage at different heights on the pillars or in biomass and species abundance at different directions (north-east or south-west) 5 months after submergence. Fish showed overall higher abundances and species numbers on the pillars (but no difference between steel and concrete) compared to the surrounding soft bottom habitats but not compared to natural vertical rock walls. Two species were attracted to the pillars, indicating a reef effect; Gobiusculus flavescens and Ctenolabrus rupestris. The bottom-dwelling gobies, Pomatoschistus spp., did not show such preferences.

Is sediment mud content a significant predictor of macrobenthos abundance in low-mud-content tidal flats?

Sediment mud content is a significant predictor of macrobenthos abundance in marine soft-bottom habitats. However, the mechanisms behind the non-linearity generally shown in mud–macrobenthos relationships have not been examined. The present study analysed spatial distributions of sediment properties and macrobenthos in a tidal flat system of the north-east coast of Japan and tested the hypothesis: the non-linearity of mud–macrobenthos relationship corresponds to changes in bed elevation variability and sediment cohesiveness. For two macrobenthos species studied, Nuttallia olivacea (Bivalvia) and Hediste spp. (Polychaeta), the relationships between mud content (<75 μm) and their density showed discontinuities at ~0.1% and ~20% mud contents. In stations with <0.1% mud content, the densities of both species were related positively to mud content and negatively to bed elevation variability, suggesting that mud content reflected negative effects of bed elevation variability on macrobenthos abundance. The stations where distinct changes were observed in macrobenthos densities below or above ~20% mud content were within an area where a shift between non-cohesive and cohesive sediments was found. Hence, the results of the present study support the hypothesis and also suggest that sediment mud content can be a sensitive predictor of macrobenthos abundance even within a relatively low and narrow range of mud content.