Marine Benthic Assemblages Research Articles

Porifera Associated with Deep-Water Stylasterids (Cnidaria, Hydrozoa): New Species and Records from the Ross Sea (Antarctica)

Stylasterid corals are known to be fundamental habitat-formers in both deep and shallow waters. Their tridimensional structure enhances habitat complexity by creating refuges for a variety of organisms and by acting as basibionts for many other invertebrates, including sponges. Porifera represent crucial components of marine benthic assemblages and, in Antarctica, they often dominate benthic communities. Here, we explore the sponge community associated with thanatocoenosis, mostly composed of dead stylasterid skeletons, collected along the Western and Northern edges of the Ross Sea continental shelf. Overall, 37 sponge species were identified from 278 fragments of the stylasterid Inferiolabiata labiata, of which 7 are first records for the Ross Sea, 1 is first record for Antarctic waters and 2 are proposed as new species. Despite the high biodiversity recorded in this and previous studies on Antarctic deep-sea communities, we are still far from capturing the true richness of Antarctic benthic assemblages. Long-term research programs designed to improve the knowledge of the deep-sea fauna inhabiting Antarctic waters are needed to support successful management and conservation plans, especially in this area, considered one of the main marine diversity hotspots worldwide.

Spatial patterns of beta diversity in marine benthic assemblages from coastal areas of southern Brazil and their implications for conservation

Beta diversity helps to understand changes in species composition over space and time, with two key components: nestedness (hierarchical pattern in richer sites) and turnover (species replacement due to niche or dispersal differences). It measures the loss or gain of species (nestedness) and species replacement (turnover) when comparing two or more spatial/temporal/environmental units. As both components require different species conservation strategies, assessing which of them the communities are organized is an important tool for this purpose. Our study aimed to evaluate which two components of beta diversity (nestedness or turnover) are responsible for structuring invertebrate and fish assemblages on the southern coast of Brazil. This region is historically recognized as a shrimp trawling area, a type of fishing with negative impacts on marine biota, such as the removal of species and habitat destruction. Our results suggest that the overall beta diversity values demonstrated a high environmental heterogeneity among the sampled areas. The most significant fraction of the general beta diversity for both assemblages is explained by the spatial turnover component. As depth increased, there was a significant rise in overall beta diversity and species turnover for fish and invertebrate assemblages. In contrast, there were no significant correlations among the nestedness component, the geographical distance and depth. In water mass conditions, fish assemblage decreased with rising chlorophyll and decreasing temperature. Elevated marine phosphate and thick sediments adversely impacted invertebrate composition. Additionally, invertebrate richness showed a positive correlation with fine sand grains. The research conducted along the southern coast of Brazil suggests the utmost importance of these regions in terms of species conservation. Here, the dominant influence of the turnover component shapes the organization of subtropical marine benthic assemblages. Furthermore, these areas receive frequent visits from migratory species, further accentuating their ecological significance.

Chemical fractionation in benthic fauna from Saya de Malha Bank (Mascarene Plateau, western Indian Ocean): Vital and habitat effects

The temperature, salinity, nutrient availability and dissolved oxygen characterizing ocean water-masses and circulation patterns are essential environmental controlling parameters of marine benthic assemblages. This work presents for the first time the geochemical composition of different taxonomic groups of benthic assemblages from the Saya de Malha Bank, Mascarene Plateau (Indian Ocean). The studied stations, located in water masses at different water depths, are perfect spots for studying biogeochemical proxies of diverse taxonomic groups to elucidate the impact of the vital factor as opposed to environmental or oceanographic factors. Forty-two specimens were studied, including scleractinian corals, bryozoans, brachiopods, bivalves, gastropods, scaphopods, and echinoids. Specimens were taphonomically analyzed in order to discard those with a poor preservation that might affect the geochemical assays. Geochemical analyses of the specimens involved high resolution inductively coupled plasma-mass spectrometry for main and trace elements. According to the results, (1) the content of trace elements in the shells is primarily controlled by their mineralogy: i.e. aragonitic, low-Mg calcite, and high-Mg calcite. (2) Vital effects related to metabolism play a major role in the co-precipitation and adsorption of trace elements in the shells, especially for Ca, Mg, Sr, Ba, and Zn. (3) The environmental parameters (habitat effect) such as oxygenation, primary productivity, salinity, but mainly temperature, at different water depths were found to be related to the growth rate of the specimens and the incorporation of trace elements. In the shallower station, the Li/Mg ratio is lower and the content in U is higher among the selected taxa, which is related to an increased growth rate in warmer waters.

Substrate Heterogeneity as a Trigger for Species Diversity in Marine Benthic Assemblages.

Many studies show that habitat complexity or habitat diversity plays a major role in biodiversity throughout different spatial scales: as structural heterogeneity increases, so does the number of available (micro-) habitats for the potential species inventory. The capability of housing species (even rare species) increases rapidly with increasing habitat heterogeneity. However, habitat complexity is not easy to measure in marine sublittoral sediments. In our study, we came up with a proposal to estimate sublittoral benthic habitat complexity using standard underwater video techniques. This tool was subsequently used to investigate the effect of habitat complexity on species richness in comparison to other environmental parameters in a marine protected area situated in the Fehmarn Belt, a narrow strait in the southwestern Baltic Sea. Our results show that species richness is significantly higher in heterogeneous substrates throughout all considered sediment types. Congruently, the presence of rare species increases with structural complexity. Our findings highlight the importance of the availability of microhabitats for benthic biodiversity as well as of the study area for regional ecosystem functioning.

The relative contribution of non-selection and selection processes in marine benthic assemblages

We tested the hypothesis that the ubiquity of marine meiofaunal nematodes and their indiscriminate passive dispersal create assemblages that are less limited by its environment; whereas the relatively smaller population sizes of macrofauna, associated with their ability to track environmental conditions before settlement, renders their distribution more environmentally-restricted. We compared the empirical distribution of macrofauna and nematode species with that of communities simulated under different assumptions of selection (e.g. environmental filtering) and non-selection (e.g. dispersal limitation) processes. Selection processes were the prime driver of both meio- and macrofauna assemblages, with rare species strongly contributing to this component. The total number of species explained by non-selection processes was 27% higher in nematodes than in macrofauna. Our results underline the importance of a species-level approach to determine the contribution of selection and non-selection assembly processes. Moreover, they highlight the important yet overlooked role of dispersal and stochastic processes in determining species dynamics.

Nestedness and turnover unveil inverse spatial patterns of compositional and functional β‐diversity at varying depth in marine benthos

AbstractAimThe two additive components of β‐diversity, namely turnover and nestedness, reflect the two basic mechanisms underlying the overall change in species identities across the landscape, the replacement of species or their loss, respectively. Analogously, functional turnover and nestedness express the replacement or loss of functional traits associated with variations in community composition. However, the extent to which patterns of compositional and functional nestedness and turnover may overlap, or diverge, is still uncertain in marine environments. Here, patterns of turnover and nestedness were quantified in marine benthic assemblages in order to assess their relative contribution to spatial patterns of compositional and functional β‐diversity.LocationMediterranean Sea, NE Ionian Sea, Ionian Archipelago.MethodsIn this study, we investigated patterns of dissimilarity in species and functional trait composition in subtidal macrobenthic assemblages from Mediterranean islands in order to quantify compositional and functional β‐diversity among islands, determine the relative contributions of turnover and nestedness, and compare β‐diversity patterns occurring in shallow and deeper reefs.ResultsWe found a complex relationship between functional and compositional β‐diversity at varying depth. At 5 m, species and functional trait dissimilarity largely overlapped, with turnover being the dominant component in both cases. At 15 m, compositional β‐diversity was mostly due to turnover, with a negligible contribution of nestedness, whereas the opposite occurred for functional β‐diversity. Partitioning β‐diversity components revealed this discrepancy and the presence of functional hotspots, which would remain unnoticed analysing the overall compositional and functional β‐diversity.Main conclusionsOur findings may have profound implications for the optimization of conservation planning, stressing the need for assessing habitat‐dependent idiosyncrasies in components of functional and compositional β‐diversity for a more comprehensive picture of possible protection scenarios that, besides structure, may also allow preserving the functioning of marine communities.

Marine benthic diatoms in the newly discovered coral reefs, off Basra coast, Southern Iraq<p align="center"><br />

The recent discovery of coral reefs off Basra, Southern Iraq, have prompted the investigation of marine benthic assemblages in this unexplored ecosystem. These corals are thriving in an environment with conditions not usually considered typical for reefs, such as increased turbidity, temperature fluctuation, and currents. This study documents 96 diatom taxa belonging to 33 genera, 18 of which were not previously known from the Arabian (Persian) Gulf including six taxa of Amphora and five of Campylodiscus. The most common genera were Amphora with 17 taxa, Nitzschia with 10 taxa, and Navicula with nine taxa. Most notably is the very rare occurrence of Mastogloia, which has been previously documented as speciose in coral reef habitats. Similarly, araphid and monoraphid species were uncommon in these diatom communities. The large species of the epipelic diatom Trachyneis are well represented and appeared commonly in all samples examined.

Comunidades de equinodermos en la región de Tunantal, Golfo de Cariaco, Venezuela

Echinoderms are relevant in the structure of marine benthic assemblages, both due their diversity and their ecological niche. However, studies related with occurrence, abundance and patterns of distribution of echinoderms in Venezuela are still scarce. In the present study we describe the echinoderms in shallow-waters habitats (corals patches, Thalassia beds, sandy bottom, rocky subtidal shore, and mouth of river) at Tunantal bay, Golfo de Cariaco, Venezuela, an area that face threats related with the increase of urban development. Samples were performed during September - October 2010 and February - April 2011, using quantitative (1 m2 plots) and qualitative diving observations. Measurements include density, number of species, evenness, Shannon diversity and similarities between habitats based on Bray-Curtis and Sorensen Indexes. Differences in the structure of echinoderm assemblages were detected between habitats. The overall number of echinoderm species in the area was estimated in 40 ± 3.02. Coral patches and rocky shores showed more species and abundance, evenness and Shannon diversity than others habitats. Although the former habitats are similar in evenness and Shannon diversity, differences in the structure of the assemblages were detected. In coral habitats Echinometra viridis, Ophiactis savignyi and Ophiothrix angulata were the dominants species of the assemblages, meanwhile in rocky shores E. lucunter and Ophiocoma echinata were dominants in abundance followed by Ophionereis reticulata. Other habitats of the bay (Thalassia beds, sandy bottom and mouth of river) showed very low diversity and abundance of echinoderms, in some cases only occasional occurrence. Substrate heterogeneity is proposed as the main driving factor of the diversity and structure of the echinoderms assemblages in the bay. Moreover coral patches and rocky shores offer a substratum to dominant species (E. viridis, E. lucunter and O. echinata), but habitat differences in terms of substratum, depth and wave stress could explain the differences in the echinoderm assemblage. The overall echinoderm diversity is promoted by the differences of habitats in the bay and the changes of species composition between habitats.

Fine-scale benthic biodiversity patterns inferred from image processing

Despite potentially considerable advantages over traditional sampling techniques, image-derived indices of habitat complexity have rarely been used to predict patterns in marine biodiversity. Advantages include increased speed and coverage of sampling, avoidance of destructive sampling, and substantially reduced processing time compared to traditional taxonomic approaches, thus providing a starting point for more detailed analysis if warranted. In this study, we test the idea that the mean information gain (MIG) and mean mutual information (MMI), two indices of image heterogeneity that we derived from photographs of marine benthic assemblages, represent good preliminary predictors of biodiversity patterns for 133 benthic invertebrate and algal taxa on jetty pylons in Gulf St Vincent, South Australia. Both MIG and MMI were spatially structured, with evidence of among-site differences that were also evident in the benthic data. When combined with information on the spatial structure within the dataset (site and depth), MIG and MMI explained ∼35% of deviance in invertebrate species richness, ∼43% in Shannon's evenness and up to 50% of dissimilarity in species composition. This explanatory power is of a similar magnitude to many other, less readily available, surrogate measures of biodiversity. These results corroborate the idea that indices of image heterogeneity can provide useful and cost-effective complements to traditional methods used for describing (or predicting) marine epibiota biodiversity patterns. This approach can be applied to many case studies for which photographic data are available, and has the potential to result in substantial time and cost savings.

Relationships between biodiversity and the stability of marine ecosystems: Comparisons at a European scale using meta-analysis

The relationship between biodiversity and stability of marine benthic assemblages was investigated through meta-analyses using existing data sets (n=28) covering various spatial (m–km) and temporal (1973–2006; ranging from 5 to >250months) scales in different benthic habitats (emergent rock, rock pools and sedimentary habitats) over different European marine systems (North Atlantic and western Mediterranean). Stability was measured by a lower variability in time, and variability was estimated as temporal variance of species richness, total abundance (density or % cover) and community structure (using Bray–Curtis dissimilarities on species composition and abundance). Stability generally decreased with species richness. Temporal variability in species richness increased with the number of species at both quadrat (<1m2) and site (~100m2) scales, while no relationship was observed by multivariate analyses. Positive relationships were also observed at the scale of site between temporal variability in species richness and variability in community structure with evenness estimates. This implies that the relationship between species richness or evenness and species richness variability is slightly positive and depends on the scale of observation. Thus, species richness does not stabilize temporal fluctuations in species number, rather species rich assemblages are those most likely to undergo the largest fluctuations in species numbers and abundance from time to time. Changes within community assemblages in terms of structure are, however, generally independent of biodiversity. Except for sedimentary and rock pool habitats, no relationship was observed between temporal variation of total abundances and diversity at either scale. Overall, our results emphasize that the relation between species richness and species-level measures of temporal variability depends on scale of measurements, type of habitats and the marine system (North Atlantic and Mediterranean) considered.

Reproductive ecology of a hippolytid shrimp, Lebbeus virentova (Caridea: Hippolytidae) at the Von Damm Vent Field, Mid-Cayman Spreading Centre

Elucidation of life-history traits is essential to understand larval dispersal and population dynamics in marine benthic assemblages. This study is the first investigation of the life history of a recently described hippolytid shrimp from a deep-sea chemosynthetic environment, Lebbeus virentova Nye, Copley, Plouviez and Van Dover, 2013 at the Von Damm Vent Field (18°22N, 81°47W, ~2,300 m depth, Mid-Cayman Spreading Centre, Caribbean), using samples collected in February and June 2013. Lebbeus virentova is gonochoric and iteroparous. The sex ratio of L. virentova was significantly female biased (1:3) in February and June. The sampled population of L. virentova had a unimodal size–frequency distribution pattern in February and June, consistent with continuous recruitment and mortality. Continuous reproduction is indicated by a lack of synchrony in oocyte size–frequency distributions within both months, and asynchronous development of embryos among females, which may result in asynchronous larval release. A large embryo size in this species (2.65 ± 0.28 mm diameter) compared with other caridean shrimps suggests possible abbreviated larval development, as described in other species of the genus from non-chemosynthetic environments. Fecundity (26–94 embryos female−1) was lower and embryo size larger in L. virentova compared with alvinocaridids at chemosynthetic environments. This suggests that there are phylogenetic constraints on reproductive features of decapods at hydrothermal vents.

Changes in biological traits of macro-benthic communities subjected to different intensities of demersal trawling along the west coast of southern Africa

Biological traits analysis (BTA) is considered to be a powerful technique for describing the ecological functioning of marine benthic assemblages. This study is the first to apply BTA to assess differences in the traits of benthic faunal assemblages between areas exposed to heavy and light trawling in a major upwelling ecosystem along the west coast of southern Africa. The data were collected from two sampling locations in Namibia and six sampling locations in South Africa. The intensity of trawling varied from area to area. Significant differences in biological traits (BT) were detected between heavily and lightly trawled areas. Weighted infaunal traits showed significant differences between heavily and lightly trawled areas for 17% of the traits investigated, while 24% of epifaunal traits investigated were significantly different between areas of different trawling intensities. This suggests that the measured BTs of the epifauna might be more sensitive to trawling disturbances than BTs of the infauna. The infaunal traits differed significantly between areas with larger or smaller proportions of sand and mud. Nevertheless, more of the significant differences in infaunal BTs were related to variations in trawling intensity than to variations in sediment composition. Significant modifications of BTs are likely to lead to modified functioning of the community and provide more general potential indicators for management than those based on species. The study confirms the need for more basic biological and life history data on macro-benthic invertebrates but nevertheless shows that BTA detected specific features that correlate with trawling intensity and that these features may be important for epifaunal assemblage functioning.

Long-term temporal and spatial variation of macrobenthos in the intertidal soft-bottom flats of two small bights (Chupa Inlet, Kandalaksha Bay, White Sea)

Despite the dynamic nature of spatial pattern, the temporal variation of spatial structure of marine benthic assemblages is rarely assessed using several temporal scales. We quantified the variability of density and biomass of main benthic species in the intertidal soft-bottom flats at two bights in Chupa Inlet (Kandalaksha Bay, the White Sea). The data cover the 21-year period (1987–2008) of a long-term monitoring survey (1987–present) using a hierarchical sampling design with two temporal (year, season within a year) and three spatial scales (bights—7 km, stations within a bight—10–100 m, and replicate samples—10 s cm apart). We used nested ANOVA to test significance and variance components to compare the relative contribution of different scales of variability of density and biomass of 18 most occurring macrobenthic species. Some species demonstrated high large-scale variability, however, the majority showed high small-scale variability and residual variance. The interactive variability was at least as important as the temporal effects, indicating that the spatial pattern changes through time. The assemblages were more variable at small scales and more stable at larger scales. Potential implications for sampling design are discussed.

Measuring more of β-diversity: Quantifying patterns of variation in assemblage heterogeneity. An insight from marine benthic assemblages

β-Diversity is currently receiving increasing attention, after being neglected for a long time, especially in marine environments. Recent works introduced the distinction within β-diversity between turnover and variation. The former relates to directional changes in β-diversity along any gradient, the latter to non-directional changes, or, in other words, to the heterogeneity of assemblages within any spatial, temporal, or environmental extent. However, the quantification of assemblage heterogeneity in assessing patterns of β-diversity is still largely unexplored. Here, we investigate the potential of classical and multivariate measures of β-diversity in highlighting patterns of assemblage heterogeneity examining eight cases of study from Mediterranean Sea, involving different marine organisms and a variety of environmental settings. Multivariate analyses were employed to assess differences in assemblage structure imputable to the investigated source of variability. ANOVAs on a set of diversity indices were also performed to test for effects on patterns of α-diversity. Differences in assemblage heterogeneity were tested using both classical and distance-based multivariate dispersion measures of β-diversity as variation. Mean values of classical β-diversity metrics were analyzed using ANOVA, whereas, for distance-based multivariate dispersion, permutational tests based on a set of resemblance measures were carried out. In all study cases, analyses of β-diversity as variation showed significant effects of the investigated source of variability in modifying patterns of assemblage heterogeneity, even when no effects on the multivariate structure of assemblages and/or α-diversity were detected. The assessment of β-diversity as variation could potentially unveil patterns of change in assemblages that could remain unnoticed analyzing other components of diversity, providing complementary information crucial to the understanding of the effects of natural and anthropogenic disturbances on natural assemblages.

Functional structure of marine benthic assemblages using Biological Traits Analysis (BTA): A study along the Emilia-Romagna coastline (Italy, North-West Adriatic Sea)

The functional diversity index has shown that the functional diversity of the macrobenthic community increased along a spatial gradient of distance from the Po river delta (Emilia-Romagna coast, Italy, North-Adriatic Sea), which suggests that riverine inputs have a detrimental effect on community functioning. This study focuses on two different depths along a southward gradient of increasing distance from the Po river delta where the Po river is the main source of freshwater and nutrient inputs in the North-Adriatic Sea. A Biological Traits Analysis (BTA) was used to examine a dataset of 156 soft-bottom macrobenthic species that were collected at eight stations in this area. Instead of comparing communities on the basis of their taxonomic composition, BTA uses a series of life history, morphological and behavioural characteristics of species to indicate aspects of their ecological functioning. The variability of the Emilia-Romagna dataset was governed by relatively few biological traits: growth form, trophic group, type of movement, habit, adult mobility and bioturbation activity. The community closer to the coastline was mainly composed of moderately mobile vermiform organisms with burrowing or tube-dwelling behaviour, and deposit feeding behaviour. However, the offshore community was mainly characterized by organisms with a laterally compressed or globose body and tube-dwelling behaviour; filter feeders and deposit feeders were dominant.

Influence of rare species on beta diversity estimates in marine benthic assemblages

Beta diversity measures the variability in species composition, and Whittaker's index has become the most widely used measure of β-diversity. However, on soft bottom benthic assemblages Whittaker's index is heavily influenced by the number of species recorded in a single sample (defined as rare species). This over-weighting of rare species induces biased estimates of the heterogeneity, so it becomes difficult to compare assemblages containing an high proportion of rare species. In benthic communities the unusual large number of rare species is frequently attributed to a combination of sampling errors and insufficient sampling effort. In order to reduce the influence of rare species on the measure of beta diversity, we developed an alternative index based on simple probabilistic considerations. It turns out that our probability index is an ordinary Michaelis-Menten transformation of Whittaker's index but behaves more favourably when species heterogeneity increases. Our suggested index therefore seems appropriate when comparing patterns of complexity in marine benthic assemblages.

Patterns of higher taxon colonisation and development in sessile marine benthic assemblages at Casey Station, Antarctica, and their use in environmental monitoring

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 365:77-89 (2008) - DOI: https://doi.org/10.3354/meps07559 Patterns of higher taxon colonisation and development in sessile marine benthic assemblages at Casey Station, Antarctica, and their use in environmental monitoring Jonathan S. Stark* Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia *Email: jonny.stark@aad.gov.au ABSTRACT: Colonisation and development of sessile epibiotic assemblages on tiles was studied at Casey Station, East Antarctica, using a mix of higher taxon classifications (family to phylum). Tiles were deployed for 1 and 3 yr at 3 control and 2 impacted locations. Assemblages on upper and lower surfaces of tiles were very different, with little colonisation of upper surfaces (0 to 11% after 3 yr) and extensive colonisation of lower surfaces (60 to 91% after 3 yr), which is greater than previously reported from Antarctica. Hypotheses were tested relating to spatial variation, depth, human impacts (a sewage outfall and a waste disposal site) and period of deployment. Differences between control locations were only apparent after 3 yr, but there were significant differences between control and impacted locations after 1 yr. There were differences between assemblages at 7 to 10 m and 19 to 22 m. Assemblages were initially dominated by spirorbid polychaetes and bryozoans, but by 3 yr there was significant sponge cover at some locations. Both impacted locations had significantly greater cover on upper surfaces than controls. The waste disposal site had the least cover on lower surfaces, with almost no sponge and less bryozoans than controls. The outfall had the greatest cover on the lower surfaces, the greatest cover of spirorbids and sponges but the least cover of bryozoans. Higher taxa assemblage patterns of colonisation on settlement panels are potentially useful as a medium- to long-term monitoring tool for sheltered Antarctic nearshore waters. KEY WORDS: Marine benthos · Colonisation · Settlement panels · Environmental impact · Assemblage succession · Monitoring Full text in pdf format PreviousNextCite this article as: Stark JS (2008) Patterns of higher taxon colonisation and development in sessile marine benthic assemblages at Casey Station, Antarctica, and their use in environmental monitoring. Mar Ecol Prog Ser 365:77-89. https://doi.org/10.3354/meps07559 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 365. Online publication date: August 18, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

The impact of rare species on natural assemblages

Summary Compared with most terrestrial data sets used in development of theoretical models, what characterizes data sets from marine soft sediments is that they have a very high number of species. Marine data also show large numbers of rare species, even if the extent of the study is greatly increased from a few square metres to hundreds of square kilometres. Fitting log‐normal distributions to data on species abundance distributions (SADs) for marine benthic assemblages from the continental shelf of Norway, and for the well‐studied tropical tree data of Barro Colorado Island, Panama (BCI), show patterns suggesting that more than one log‐normal distribution occurs. We have developed a simple model of SADs comprising two groups of log‐normally distributed species, a group of rare species and a group of common species. The model appears to fit the marine data and also applies to the BCI tropical tree data and yet is simpler than Hubbell's Zero‐Sum Multinomial (ZSM) distribution model. The plots of the model results show that the marine data are dominated by the rare group of species at all scales studied. In the tropical tree assemblage a similar pattern to that in the marine data is apparent only at small spatial scales (5 and 10 ha), but not at the larger extent (25–50 ha). It is important to note, however, that marine data at all the scales studied are samples from a given area, whereas the terrestrial data are exact counts of all species of tree within the total 50 ha plot studied. Most ecological data are likely to be based on samples rather than exact counts so the patterns found with the marine data are likely to be common, and our findings general ones. A biological explanation for the two‐group log‐normal model is that recruitment of rare species from outside the studied area dominates benthic assemblages of soft sediments at all sampled scales. Within the tropical forest the dominance of recruitment processes are only apparent at small scales. Thus, the interpretation of SAD patterns depends greatly on the type of data collected, i.e. whether they are exact counts or samples. We believe that structuring processes are similar in marine and many terrestrial systems and these processes probably conform to the mass‐effects paradigm of the newly termed meta‐community concept.

Methods for describing ecological functioning of marine benthic assemblages using biological traits analysis (BTA)

Biological traits analysis (BTA) is a method recently proposed for describing ecological functioning of marine benthic assemblages. It incorporates information on species’ distributions and the biological characteristics they exhibit, to produce a summary of the biological trait composition of assemblages. The approach provides a link between species, environments and ecosystem processes, and is potentially useful for the investigation of anthropogenic impacts on ecological functioning. As part of the development of BTA for application to marine systems, two aspects of the approach were investigated here: (1) the comparative applicability of three analytical tools proposed for conducting BTA and (2) the sensitivity of the approach to the number and type of traits selected for analysis. The three tools, fuzzy correspondence analysis (FCA), co-inertia analysis (CoI) and non-metric multidimensional scaling (nmMDS) portrayed trait composition of benthic assemblages in similar ways, however nmMDS had less power to discriminate between assemblages with varying trait composition than FCA or CoI. For the thirteen biological traits considered, the number of traits selected for analysis affected the ability of BTA to describe relationships between assemblages, more so than the identity of the traits themselves. Ultimately, selection of biological traits for inclusion in BTA will be based on a trade-off between their efficacy for describing variability in ecological functioning and the time and effort required to gather information on the biological characteristics of the taxa studied. The choice of analytical tool is a balance between the power of the tool to describe changes in trait composition and the ease with which results can be interpreted. nmMDS is appropriate for providing a general picture of functioning in marine assemblages, whereas FCA and CoI have greater power to detect the effects of human impacts, but are more difficult to interpret. Including as many traits as possible will lead to the most useful description of ecological functioning, as will selecting traits sensitive to anthropogenic impacts or closely linked to important ecosystem processes.

Spatial variation in the recruitment of benthic assemblages to artificial substrata

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 290:67-78 (2005) - doi:10.3354/meps290067 Spatial variation in the recruitment of benthic assemblages to artificial substrata Michael J. Rule*, Stephen D. A. Smith School of Environmental Science and Natural Resources Management, University of New England, National Marine Science Centre, PO Box J321, Coffs Harbour, New South Wales 2450, Australia *Email: mrule@nmsc.edu.au ABSTRACT: Artificial substrata have repeatedly been advocated as useful tools for monitoring environmental change; however, the spatial scales of recruitment to these substrata are mostly unknown. Nests of nylon pan scourers were used to examine variation in the recruitment of marine benthic assemblages over a range of spatial scales (metres, 10s of metres, 100s of metres, kilometres), within the Solitary Islands Marine Park (SIMP), NSW, Australia. Using a nested design, artificial substratum units (ASUs) were anchored to rocky reef for a period of 5 mo, at a depth of 6 to 8 m, at 2 island sites. Data were subjected to both univariate and multivariate analyses to determine the similarity of assemblages between all hierarchical levels. Artificial substrata were colonised predominantly by motile fauna. Large-scale patterns of recruitment were obvious, with samples from NW Solitary Island numerically dominated by the bivalve Hiatella australis, and samples from North Solitary Island by the amphipod Mallacoota euroka. Significant differences in the mean abundance of individual faunal groups (amphipods, bivalves, polychaetes, decapods) were identified over all spatial scales. Multivariate analyses revealed the structure of recruiting assemblages varied over all scales although differences at the smallest spatial scale were uncommon. The results highlight the importance of variation over both small and large spatial scales for assemblages of motile fauna recruiting to artificial substrata, and suggest that this variation needs to be considered when conducting experiments with these types of artificial substrata. KEY WORDS: Spatial scale · Recruitment · Motile invertebrates · Artificial substrata Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 290. Online publication date: April 13, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.