Macrofaunal Species Research Articles

Development of macrofaunal community structure in mussel beds on the northern East Pacific Rise

Comparisons of macrofaunal community structure (species composition, abundance, biovolume, rank order, species richness, diversity) in hydrothermal vent mussel beds at 9° 50' N (9N) on the East Pacific Rise were made from analysis of multiple quantitative samples collected in 1999 and 2001 from each of 3 mussel beds of known age (4 to 8 yr in 1999). In addition to this time series approach, a chronosequence based on 2001 samples from 4 mussel beds at 9N and 1 mussel bed at 11° 25' N (11N) allowed comparison of macrofaunal community structure for mussel beds ranging in age from 6 to >14 yr. Many aspects of community structure (rank abundance patterns, dominant species, and diversity) were similar in 1999 and 2001 samples. Young (6 to 7 yr) and old (10 to 14 yr) mussel beds sampled in 2001 could be distinguished using multivariate analyses, based on species abundance and species biovolume matrices, but the differences were in the relative abundance of the dominant species rather than in any substantial changes in the identity of the dominant species. The limpet Lepetodrilus elevatus was the dominant species at all sites in terms of abundance and bio- volume; it and other dominant species may have slightly greater fitness compared to other species that allows them to persist as dominants regardless of the age or location of mussel beds. Decreasing biovolume of macrofaunal communities sampled at 9N and 11N in 2001 was correlated with in- creasing age of the mussel beds and is postulated to be largely a response to biological processes; including competition for inorganic substrates by free living and symbiotic chemoautotrophs and mussel induced mortality of larvae of macrofaunal species, rather than the result of waning hydro- thermal activity.

Mussels matter: postlarval dispersal dynamics altered by a spatially complex ecosystem engineer

This study investigated postlarval dispersal of soft-bottom macrofauna at a spatially complex intertidal mudflat comprising patches of bare sediment and an ecosystem engineer, the mussel Mytilus edulis. At each of four sites in Guard Point Cove, Maine, USA, we took core samples and deployed bedload traps in bare sediment and mussel bed habitats to estimate ambient densities, rates of sediment flux, and several measures of postlarval dispersal. Univariate and multivariate nonmetric multidimensional scaling (nMDS) results showed few significant site effects and no habitat×site interactions. In contrast, there were numerous significant habitat effects. Compared to the bare sediment, the mussel bed habitat had: fewer species; higher ambient density and proportional abundance of the oligochaete Tubificoides benedeni (the dominant species in both habitats); lower ambient densities and proportional abundances of major taxa and the nonoligochaetes as a group; and higher sediment flux and relative (i.e., per capita) dispersal of nonoligochaetes. Macrofauna species dispersed in relative proportions that were different from those in the ambient assemblage. Per capita T. benedeni transport rates were low in mussel beds compared to those for nonoligochaetes, consistent with the view that beds represent favorable habitat for oligochaetes. The number of total macrofauna individuals trap −1 day −1 was negatively correlated with ambient density and positively correlated with sediment flux in both habitats, but these relationships were significant only in the mussel bed. The results indicate that altered transport rates of sediment and postlarvae are important mechanisms by which mussels act as ecosystem engineers to modify soft-bottom habitats. Differential transport rates caused by aggregations of mussels and other foundation species must be considered in explanations of spatial pattern in soft-bottom communities.

Abundance – occupancy relationships in macrofauna on exposed sandy beaches: patterns and mechanisms

We studied the relationship between abundance and extent of occupancy of 158 species of macrofauna inhabiting 66 sandy beaches around the coast of Great Britain. We also used these data to test the predictions of two hypotheses proposed to explain positive abundance‐occupancy relationships. We found a strong positive relationship between abundance and extent of occupancy; this pattern was apparent in taxonomic subsets of organisms which have contrasting reproductive and dispersal traits such as planktotrophic/lecithotrophic development in the plankton vs brood development under parental care. Moreover, the abundance‐occupancy relationships in these taxonomic subsets had statistically indistinguishable slopes, and elevation. We propose that this lends support to the notion that differences in population structure such as the tendency to form metapopulations may not be primary determinants of the abundance‐occupancy pattern in these taxa as proposed by the rescue/metapopulation hypothesis. To test the predictions of the niche‐breadth hypothesis we derived values describing the range of sediment grain‐sizes exploited by members of two taxonomic subgroups: amphipods and bivalves. We found a weak, statistically non‐significant relationship between this niche‐breadth measure and occupancy in bivalves which have been shown to respond to grain‐size in previous studies, however this was negated after correction for possible artefacts of sampling effort. All other relationships between abundance or occupancy and grain‐size range were non‐significant. The consistency of the demonstrated abundance‐occupancy relationship with those demonstrated in other studies of primarily terrestrial fauna indicates some shared mechanistic explanation, but our data fail to provide support for the two mechanistic hypotheses investigated.

Seasonal changes in the distribution and abundance of benthic invertebrates in six headwater streams in central Florida

Seasonal variations in invertebrate assemblages at two sites (upstream and downstream) on six central Florida headwater streams were compared by sampling at quarterly intervals with core and dip net samplers. Two of the streams were reclaimed following phosphate mining (∼6 yr prior to this study), two received runoff from mined lands, and two were disturbed by agriculture and/or residential developments. Physical and chemical characteristics of the reclaimed streams differed markedly from those of the non-reclaimed streams; principal differences between the streams were in current velocity, percent organic matter (POM), Mn, conductivity and alkalinity. Annual mean densities of meiofauna and smaller macrofauna for the 12 stream sites ranged from 20 896 to 175 212 m−2 and the mean for all sites was 56 492 m−2. The reclaimed streams and one of the streams influenced by agriculture had annual means of less than 40 000 m−2, 3- to 5-fold lower than the other streams. Fall and winter core densities were ∼2.4-fold greater than those for spring or summer when drought and low dissolved oxygen prevailed. Meiofauna comprised 68–91% of the core sample invertebrates in reclaimed streams but only 43–62% in the non-reclaimed streams; principal functional groups were: gathering collectors – 61.5%, predators – 19.3% and filtering collectors – 15%. The taxonomic composition of the reclaimed streams was predominated by crustaceans (60–71%) while chironomids and annelids were more abundant (71–92%) in the non-reclaimed streams. Dip net sampling added 21 larger macrofauna species (Odonata, Hemiptera and Coleoptera) to our list of taxa, producing a total of 209 species. Species richness and diversity (H′ and N2) indices were lower in the reclaimed streams, but evenness was more variable. The Czekanowski–Dice–Sorensen similarity index showed that the reclaimed stream sites were quite similar to each other, but differed markedly from the other stream types; there was large variation both within and between seasons. For central Florida headwater streams, drought appears to have a larger influence on invertebrates than the type of land use, however this relationship should be confirmed using streams of similar hydrology.

Structure and taxonomic composition of subtidal nematode and macrofauna assemblages at four stations around the UK coast

The diversity and structure of meiobenthic nematodes and macrobenthic infauna were studied at four widely spaced subtidal sites around the UK coast in relation to a number of measured environmental variables. The stations were situated on soft sediments at water depths of 53 to 95 m and are intended as long-term monitoring locations as part of the UK National Marine Monitoring Programme. Similar benthic assemblages were encountered in comparable environmental conditions. The distribution of nematode and macrofauna species was mainly governed by the geographical location of the habitat and the granulometric composition of the substrate. There was no evidence of any adverse effect on the measures of benthic assemblage structure arising from trace metal concentrations in the sediment, indicating the relatively unpolluted nature of the offshore locations under investigation. Nematode and macrofauna assemblages exhibited stable patterns over time periods of three years.

Structure and dynamics of the macrobenthic communities of Ubatuba Bay, southeastern Brazilian Coast

Species composition, distribution, density, biomass, diversity and trophic relationships of the macrobenthic communities in Ubatuba Bay, southeastern Brazilian coast, were investigated seasonally from August 1995 to June 1996. Sampling was carried out at 9 stations of between 4 and 13 m depth and taken in duplicate with a 0.1m² van Veen grab. Two hundred and five macrofaunal species were identified, presenting low dominance and frequency. Polychaetes and nematodes dominated, representing 89% of the whole fauna. Spatial variations in the structure of the communities were correlated to sediment type whereas seasonal variations were correlated to the increase in wave size and current disturbance over the substrate during the rainy period. Carnivore and surface deposit-feeder polychaetes were dominant, totalling 81% of the species. Mean grain size, fine sand, very fine sand, silt and clay contents were among the main factors related to the patterns of macrofaunal distribution, density and diversity and to the dominance of trophic groups. Multivariate analysis showed that the area may be divided into two groups of stations each of them characterized, respectively, by the presence of Magelona papillicornis and Mediomastus capensis.

Community structure in Florida Escarpment seep and Snake Pit (Mid-Atlantic Ridge) vent mussel beds

Comparisons between invertebrate communities hosted by similar foundation species under different environmental conditions permit identification of patterns of species distributions that might be characteristic of the different ecosystems. Similarities and differences in community structure between two major types of chemosynthetic ecosystems were assessed by analyzing samples of invertebrates associated with Bathymodiolus heckerae Gustafson et al. mussel beds at the Florida Escarpment seep (Gulf of Mexico, 26°01.8′N; 84°54.9′W; October 2000) and B. puteoserpentis von Cosel et al. mussel beds at the Snake Pit vent (Mid-Atlantic Ridge, 23°22.1′N; 44°56.9′W; July 2001). Macrofaunal species richness was nearly twice as high in the seep mussel bed compared to the vent mussel bed, and only a single morphospecies, the ophiuroid Ophioctenella acies Tyler et al., was shared between the sites. Similarities between the two faunas at higher taxonomic levels (genus and family) were evident for only a small percentage of the total number of taxa, suggesting that evolutionary histories of many of these seep and vent macrofaunal taxa are not shared. The taxonomic distinctiveness of the seep and vent mussel-bed macrofaunal communities supports the hypothesis that environmental and oceanographic barriers prevent most taxa from occupying both types of habitats. Macrofaunal community heterogeneity among samples was similar in seep and vent mussel beds, indicating that spatial scales of processes regulating community variability may be similar in the two types of ecosystems. Suspension feeders were not represented in the macrofauna of seep or vent mussel beds. Primary consumers (deposit feeders and grazers) contributed more to the total abundance of macrofauna of seep mussel beds than vent mussel beds; secondary consumers (polychaetes and shrimp) were more abundant in the vent mussel beds.

Soft-bottom macrobenthic faunal associations and factors affecting species distributions in an Arctic glacial fjord (Kongsfjord, Spitsbergen)

The Kongsfjord (west Spitsbergen) hosts the most active glacier on the island. Therefore the glacial impact on the marine ecosystem is very pronounced and easily recognisable. The study examines the influence of the steep glacier-derived environmental gradients on dominant macrofaunal species distributions and faunal associations in the fjord. The macrobenthic fauna was sampled by van Veen grab at 30 stations situated throughout the fjord (at depths 38–380 m). Two major communities were recognised. An inner basin receives the outflows from three glaciers and is occupied by a Glacial Bay Community dominated by small, surface detritus-feeders, with Chone paucibranchiata and a set of thyasirid and nuculanid bivalves (Thyasira dunbari, Yoldiella solidula, Y. lenticula) as characteristic species. An outer basin of the fjord is characterised by a common set of dominant species, including Heteromastus filiformis, Maldane sarsi, Levinsenia gracilis, Lumbrineris sp. and Leitoscoloplos sp. Three associations may be distinguished within the Outer Basin Community. Association TRANS is of transitional character, with Nuculoma tenuis and Terebellides stroemi. Association CENTR is the most typical for the community. It is dominated by tube-dwelling Prionospio sp., Clymenura polaris, Galathowenia oculata and Spiochaetopterus typicus. Association ENTR contains shelf benthos elements, e.g. Ophiura robusta and Lepeta caeca. An opportunistic eurytopic Chaetozone group is present throughout the fjord and its density and dominance increase with proximity to the glaciers. Dominant species distribution is discussed in relation to environmental factors, of which sediment stability, inorganic particle concentration, sedimentation rate and amount of organic matter in sediments are considered to be most important in structuring the communities.

Bacterial nitrification activity directly associated with isolated benthic marine animals

Potential nitrification rates (PNR) directly associated with isolated marine macrobenthic invertebrates were measured for a range of benthic epifaunal and infaunal species (bivalves, gastropods, polychaetes and crustaceans) collected from the Sacca di Goro, Po River delta, Italy. In the case of the filter-feeding bivalves, Tapes philippinarum and Mytilus galloprovicialis the PNR associated with the shell surfaces and dissected animal tissues (gills, siphons and residual tissue) were determined separately, in order to assess the distribution of the nitrifier populations. Significant PNR was found associated with all the tested macrofaunal species with activities ranging between 12 and 2,250 nmol ind.−1 day−1 and specific activities between 150 and 18,400 nmol g−1 dry weight day−1. However, no simple relationships were observed between PNR and the animals’ taxonomic or functional group, or with animal comportment (infaunal or epifaunal) or size class, indicating that more complex interactions may regulate the degree of colonisation of the animals by nitrifier populations. Incubations of shells alone and dissected tissues of the bivalves T. philippinarum and M. galloprovicialis demonstrated that approximately 50% of the total PNR activity was associated with the shell surfaces and 50% with the internal animal tissues, with the highest specific activities of 950 and 1,970 nmol g−1 dry weight day−1 determined for the gills of T. philippinarum and M. galloprovicialis, respectively. Thus, specific relationships may exist between the nitrifiers and their animal hosts. Overall, our data indicate that the macrofaunal stimulation of nitrification and/or coupled nitrification–denitrification observed in previous studies may not be solely due to the animals’ burrow walls serving as sites for nitrification, but also to the fact that the internal and external surfaces of the animals themselves are also colonised by nitrifying bacteria. Tentative calculations based on reported animal densities in the Sacca di Goro and the determined PNRs indicate that animal-associated nitrifier populations could contribute significantly to overall nitrification rates in situ, although further experiments are required to determine to what extent the potential rates measured in this study are realised under in situ conditions.

Low faunal diversity on Maltese sandy beaches: fact or artefact?

Eight sandy beaches on Malta and two on Gozo were sampled for macrofauna to test the hypothesis that Maltese beaches have an intrinsically low diversity. Stations distributed in the supralittoral (dry zone), mediolittoral (wet zone) and upper infralittoral (submerged zone to 1 m water depth) were sampled by sieving core samples and standardised searching during daytime, and pitfall trapping and standardised sweeping of the water column using a hand-net at night, as appropriate. Physical parameters of the sediment were measured and human occupancy of the beaches was estimated. From the supralittoral and mediolittoral, 39 species represented by 1584 individuals were collected by the combined techniques of pitfall trapping, sieving and standard searching. For Ramla beach, which had the highest diversity, 267 individuals representing 25 infaunal species were collected by sieving from a combined volume of 1.175 m 3 of sand, and 149 individuals representing 28 epifaunal species were collected by standardised searching from a combined area of 700 m 2 of sand during two winter and two summer sampling sessions between 1992 and 1993. For nine other beaches sampled during the summer of 2000, only six macrofaunal species were collected from core samples, with overall population densities ranging from 4.13 to 45.45 individuals m −2. Only 92 individuals belonging to 12 species were collected by hand-net from the uppermost infralittoral of five beaches sampled using this method during the summer of 2000. Taxa of gastropods, bivalves, decapods, mysids and staphylinid beetles generally abundant on Mediterranean sandy beaches, were entirely absent from the beaches sampled. Few correlations that could explain the impoverishment of Maltese sandy beaches were found between physical parameters and faunal abundances, and other factors such as inadequate sampling effort, human disturbance and marine pollution were also excluded; however, seasonally biased sampling may partly explain the results obtained. One factor that may explain why certain species are missing could be lack of recruitment, due to Malta's geographical isolation from the European and African mainlands.

Effect of the brittle star Amphiura filiformis (Amphiuridae, Echinodermata) on oxygen flux into the sediment

O2 plays a key role in early sedimentary diagenetic processes, but the effect of most macrofaunal species on the pathways and rates of supply of O2 into the seabed are not well known. We investigated the effect of the ophiuroid Amphiura filiformis, one of the dominant macrobenthic species on soft bottoms in the northeast Atlantic, at depths of ~15–100 m, in a laboratory environment. We determined how the presence of the ophiuroid changed the total O2 uptake of macrofauna‐free sediment by combining measurements from a microcosm approach and an approach that uses microelectrodes and a flushed aquarium. We suggest that natural populations of A. filiformis can account for 80% of the total flux of O2 into the soft bottom. At least 67% of this portion is due to the diffusion of O2 across additional sediment‐water interfaces excavated by the brittle star.

Preliminary observations of the effects of dredging intensity on the re-colonisation of dredged sediments off the southeast coast of England (Area 222)

The re-colonisation of a site used for the extraction of sand and gravel for ca. 25 years off the southeast coast of the UK was examined 4 years after the cessation of dredging. Effects of different levels of dredging intensity on the rate of macrofaunal re-colonisation were investigated. Values of abundance and total numbers of species were significantly lower ( p<0.05) in an area most recently exposed to the highest level of dredging intensity compared with samples taken from an area of low intensity, and those from a reference site. Differences between previously dredged sediments and the reference location were due to the reduced abundance of a range of macrofaunal species characterising nearby sediments. Multivariate measures of community structure also indicated that there were significant differences ( p<0.01) between the macrofaunal assemblages in the areas exposed to different dredging intensities. Sediment from the area exposed to the highest dredging intensity contained proportionally more sand than other sampled sediments. The extent to which dredging intensity contributed to these differences was difficult to determine owing to the absence of any baseline data. Despite this, univariate and multivariate analyses indicated a strong relationship between macrofaunal community structure and dredging intensity at this site. Correlation analyses also demonstrated that the predominant influence on the macrofaunal community was that of the level of dredging that took place in 1995, the last year that the licensed site was dredged heavily. Preliminary observations indicated that the fauna remained in a perturbed state some 4 years after cessation of dredging. Therefore, relatively rapid ‘recovery’ rates, commonly cited as 2–3 years for European coastal gravelly areas, should not be assumed to be universally applicable. Implications for the future management and scientific study of marine aggregate extraction arising from preliminary observations on the physical and biological status of this site are discussed together with the options for selecting a reference site in the absence of baseline information.

The habitat harshness hypothesis revisited: life history of the isopod Excirolana braziliensis in sandy beaches with contrasting morphodynamics

Demographic and life history characteristics of the intertidal isopod Excirolana braziliensis (Isopoda: Cirolanidae) were compared between populations of two exposed sandy beaches with contrasting morphodynamics (reflective vs dissipative) during 22 consecutive months. Most population processes and life history traits did not give support for the ‘habitat harshness hypothesis’ (HHH): abundance of males, females, ovigerous females and juveniles was significantly higher at the reflective beach population, which also presented higher growth rates in size and weight with respect to the dissipative beach population. No significant differences in weight-at-length were found between beaches. Among the compared parameters, only the lower natural mortality rates at the dissipative beach gave support for the HHH. The results were not consistent with a previous analysis of Excirolana braziliensis along Pan-American beaches, which showed that this isopod occurs almost invariably in fine sands of tropical and temperate beaches. The results give strong support to recent findings that show that in macrofauna species capable of sustaining large populations across a wide spectrum of physical conditions, such as Excirolana braziliensis, beach morphodynamics should not be considered the primary factor affecting abundance and life history traits. Instead, our results reinforce the view that sandy beach populations are controlled by the intertwined forces of biotic and abiotic factors operating together.

Habitat change in estuaries: predicting broad-scale responses of intertidal macrofauna to sediment mud content

There is a growing threat of habitat change in estuarine and coastal regions, yet there are few models that enable ecologists and resource managers to forecast the response of macrofaunal species to long-term changes in sediment type. This study details a novel strategy that enabled us to rapidly collect data on macrofaunal densities and sediment characteristics by sampling mud-to-sand transition zones in 19 estuaries. Species-specific models that predict probability of occurrence rela- tive to sediment mud content were developed for 13 common macrofaunal species. However, the roles played by many macrofaunal species are influenced by density, not just occurrence. Over broad spatial scales, the constraint an environmental variable places on density can be represented by the upper (or lower) limit on density. Thus, the distribution of maximum density along the gradient from mud to sand was modelled as another indicator of a species' preference. Both the maximum and min- imum values for number of taxa, number of individuals, Shannon-Wiener diversity and taxonomic distinctness were also modelled. For most variables, good models (r 2 > 0.6) were developed. The mod- els developed for the different species exhibited a wide variety of functional forms, highlighting the potential variation in response to habitat change even for closely related species with similar natural history characteristics. Probability-of-occurrence models and maximum-density models for a specific species also varied in functional form, emphasising that changes in both occurrence and density need to be considered when predicting likely responses to changes in habitat.

Distribution of a tetrabrominated diphenyl ether and its metabolites in soft-bottom sediment and macrofauna species

Sediment spiked with 14 C-2,2', 4, 4'-tetrabrominated diphenyl ether (BDE-47) was added as a single pulse, at a low or a high concentration, to intact soft-bottom sediments in a box-cosm system. The vertical distribution of the pollutant and the bioaccumulation in 39 different taxa of macro- fauna were analysed after 10, 20 and 29 wk exposure. Throughout the experimental period, 90% of the recovered BDE-47-derived radioactivity in the sediment was found within the upper 5 cm. The BSAF (biota-sediment accumulation factor) in the different taxa after 29 wk exposure varied between 0.4 and 16.3. The correlation between bioaccumulation and lipid content of all individual specimens in each box-cosm was significantly positive and explained between 11 and 64% of the variation. When the fauna was divided into groups with different feeding strategies, it was found that the mean BSAF was significantly higher for the surface deposit-feeders than for the suspension-feeders, subsurface feeders and the predators. The difference increased with time and was larger after 29 wk exposure than after 10 wk. We also tested whether there was a correlation between 15 N enrichment, i.e. trophic position, in the analysed species and bioaccumulation, but no such correlation was found. Water-soluble metabolites of BDE-47 were detected in 15 of the 39 macrofaunal species. There was no observable correlation between the presence of metabolites in the macrofauna and bioaccumulation of the pollutant.

Comparative study of two maerl beds with different otter trawling history, southeast Iberian Peninsula

1. A comparative study of the characteristics of sediment structure and associated assemblages was conducted in two areas with different trawling histories, one with low trawling pressure and protected since 1989 (Marine Reserve of Tabarca), and another with a high frequency of trawling (Benidorm). 2. The study was based on seasonal quantitative and qualitative sampling of macrofauna, megafauna and algae, over a period of 1 year, using scuba diving and dredging. 3. Sediment composition differed between sites. Overall Tabarca had a coarser sediment than Benidorm where there was a higher mud content and no vertical stratification. At Tabarca there was a differential vertical profile, with a higher percentage of coarse sediment in the surficial horizon, which corresponded mostly to rhodoliths. Benidorm had more mineral gravel, and Tabarca a higher percentage of biogenic gravel. 4. There were no differences between sites in the percentages of live and dead rhodoliths in the sediment. Cover of rhodoliths, however, was four times greater at Tabarca. Maximum size of rhodoliths was greater at Tabarca ( mean 16.18 mm S.D. 5.73) than at Benidorm (mean 7.64 mm S.D. 2.16). 5. The number of species of algae did not differ significantly between sites: 155 species were found at Tabarca, and 153 at Benidorm, with 13 and 10 exclusive species respectively. Although both algal assemblages were qualitatively similar, there were significant differences in the cover of the main species. At Tabarca, the cover of Corallinales was around 50% of total algal cover, while at Benidorm approximately 90% of the cover was due to non-Corallinales algae, mainly species from the genus Peysonnelia. 6. The number of macrofaunal species at Tabarca was greater than at Benidorm, with 293 (144 exclusive spp.) and 204 (53 exclusive spp.) species, respectively. Density and biomass of macrofauna was also greater at Tabarca. 7. Based on our observations, well preserved Mediterranean maerl grounds are sites with a high diversity and also support a high macrobenthic secondary production which may be important for species of commercial interest. High trawling pressure on maerl areas may affect assemblages negatively by breaking up rhodoliths, diminishing their cover and hence affecting the associated biota. Copyright © 2003 John Wiley & Sons, Ltd.

High species richness in deep-sea chemoautotrophic whale skeleton communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 260:109-114 (2003) - doi:10.3354/meps260109 High species richness in deep-sea chemoautotrophic whale skeleton communities Amy R. Baco1,2,*, Craig R. Smith1 1Department of Oceanography, 1000 Pope Road, Honolulu, Hawaii 96822, USA 2Present address: Woods Hole Oceanographic Institution, Biology Department, MS#33 2-14 Redfield, Woods Hole, Massachusetts 02543, USA *Email: abaco@whoi.edu ABSTRACT: While biodiversity in deep-sea soft sediments appears to be high, little is known about diversity levels on deep-sea hard substrates. To determine the contribution of potentially abundant whale-skeleton habitats to deep-sea biodiversity, we compare the local macrofaunal species richness and composition on 3 sulfide-rich whale skeletons to assemblages from vents, seeps, and other deep-sea hard substrates. Based on rarefaction curves, whale skeleton diversity is higher than diversity in any other deep-sea hard substrate habitat. The average local species richness (185 spp.) on single chemoautotrophic whale skeletons approaches known levels of global cold-seep macrofaunal species richness (229 spp.), and exceeds the richness of the most speciose vent field known (121 spp.). Species richness on the whale skeletons is also substantially higher than on other deep-sea non-reducing hard substrates, such as manganese nodules and rocks. Richness levels approach those in deep-sea soft sediments and exceed some shallow-water hard substrates. This high species richness may be explained by unusually high trophic diversity on whale bones due to the presence of sulphophiles, generalized organic-enrichment respondents, whale-bone consumers, and background hard-substrate fauna such as suspension and deposit feeders. High species richness levels on whale skeletons and deep-sea sponge stalks suggest deep-sea hard substrates may harbor higher levels of diversity than previously recognized. KEY WORDS: Whale fall · Species richness · Biodiversity · Deep sea · Hard substrate Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 260. Online publication date: September 30, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

The North-American amphipods, Melita nitida Smith, 1873 and Incisocalliope aestuarius (Watling and Maurer, 1973) (Crustacea: Amphipoda: Gammaridea), introduced to the Western Scheldt estuary (The Netherlands)

The American amphipod species Melita nitida andIncisocalliope aestuarius have been found in the WesternScheldt estuary (the Netherlands). This is the first record of these species inthe north-east Atlantic. Shipping is the most likely vector of introduction.Thedistribution of both species is investigated and compared with the distributionand the microhabitat of co-occurring amphipod species. Melitanitida is known from both the east and west coast of North Americaand I. aestuarius originates from the east coast of NorthAmerica. Until now neither has been reported from other parts of the world. Inthe Netherlands both species are restricted to the mesohaline part of theWestern Scheldt. Melita nitida occurs predominantly underPacific oysters at the underside of boulders, mainly sublittorally.Incisocalliope aestuarius is associated to hydrozoans.Bothmicrohabitats are hardly utilized by other amphipod species. Therefore, thetheory that the existence of many empty niches in north-western Europeanbrackish waters make this environment particularly susceptible to invasions ofalien species is corroborated. The application of hard substrates in a regionoriginally predominated by soft bottoms moreover facilitates the introductionofexotic species. The species community on hard substrates in the mesohaline partof the Western Scheldt contains a high proportion of introduced species:approximately one third of the macrofauna species is of allochthonous origin.

Site-specific features influence sediment stability of intertidal flats

Abstract. The factors that influence the sediment stability and the transport of estuarine mudflats are not yet fully understood but knowledge of them is essential in coastal engineering applications and pollution ecology studies. The suggestion that variation in predictive models of sediment stability might be due to site-specific characteristics is investigated using data from four estuarine mudflats (Eden Estuary, Scotland, the Biezelingsche Ham, Zandkreek, and Molenplaat mudflats in The Netherlands). These estuaries differ in their environmental conditions, macrofaunal species composition and local features (e.g. Enteromorpha mats, migratory biofilms). Stable and unstable sediments were compared, and mean chlorophyll-a concentrations and granulometry of the sediments were significantly different between the two groups. Step-wise multiple linear regressions were applied to the sediment stability data of all sites to establish the influences on erosion threshold of microphytobenthic biomass, water content, granulometry, organic carbon content and the abundance of dominant macrofaunal species. The stability of each site was influenced by different factors. Sediment stability of the Eden Estuary was affected by the Enteromorpha bloom; Biezelingsche Ham was influenced by the highly migratory nature of the diatom biofilms and the abundance of Corophium volutator; the polychaete worm Arenicola marina had a net negative effect on sediment stability of the Zandkreek; and the Molenplaat was influenced by microphytobenthic biomass. This research highlights the need for site-specific calibration of models and suggests that a universal proxy parameter for sediment stability is unlikely to be obtained. Keywords: sediment stability; erosion threshold; cohesive strength meter; microphytobenthos; Enteromorpha spp.

Bioturbation, ecosystem functioning and community structure

Abstract. The effect of community structure on the functioning of the ecosystem is an important issue in ecology due to continuing global species loss. The influence of infaunal community structure on the functioning of marine systems is proposed here to act primarily through bioturbation of the sediment. Nutrient concentration in the water column, generated by release from the sediment, was used as a measure of ecosystem functioning. In situ and laboratory experiments showed a significant difference in nutrient concentrations with different species treatments. Bioturbation profiles showing the incorporation of tracer particles also differed between communities with different dominant species. The behavioural differences between infaunal species, generating different modes and rates of bioturbation, are therefore proposed to influence nutrient release. The presence and quantity of bioturbating infauna also influenced the amount of sediment suspended in the water column. The increase in surface area available for microbial activity may generate an increase in nutrient cycling. Abiotic influences on sediment structure, such as flow, may have a similar effect on nutrient concentration. Annular flumes used in both laboratory and in situ experiments to generate flow conditions produced a significant increase in ammonia (NH4-N) production in macrofaunal treatments. Flow may influence the behaviour of macrofaunal species, causing changes in NH4-N production through modifying bioturbation of the sediment. Keywords: bioturbation, community structure, ccosystem functioning, estuaries, flow, infauna