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Tracking the effects of habitat attributes on species distribution is pivotal to the understanding of community assembly across space and time. We used the elements of metacommunity (EMS), which evaluates coherence, turnover, and boundary clumping of species, to access the spatial patterns of nematodes from three coastal habitats with increasing degree to wave exposure, namely, mangroves, estuarine unvegetated tidal flats, and sandy beaches. Each habitat was sampled in four locations, hundreds of kilometers apart from each other. We hypothesized that (1) coastal habitats act as metacommunity boundaries and drive positive turnover and clumped distribution of species and (2) metacommunity structure within coastal habitats depends on the habitats’ degree to wave exposure since wave energy generally decreases sediment heterogeneity and favors connectivity among locations. Habitats were the main drivers of species turnover, with tidal flats harboring a transitional assemblage between mangrove and sandy beach. Metacommunities from the different habitats showed distinct patterns of organization among locations. Mangroves were characterized by species loss, with smaller areas of mangroves harboring a subset of the species pool present on larger areas of mangroves. Tidal flats showed positive species turnover among the different estuaries, with co-occurring species responding as a group to environmental variations. Both patterns indicate environmental filtering as the main driver at these less wave-exposed habitats. At sandy beaches, in contrast, metacommunity displayed a random pattern, suggesting high connectivity among locations. Our study confirmed that habitat attributes may induce distinct mechanisms of metacommunity assembly at coastal soft-bottom ecosystems.

Species responses to stress are expected to be dependent on their life-history strategy. In this study, we compare the responses of two free-living marine nematodes, Litoditis marina and Diplolaimella dievengatensis, both considered opportunistic, fast-growing, and stress-tolerant species, to the exposure to sublethal concentrations of sodium dodecyl sulfate (SDS) surfactant. Specifically, we evaluated the growth and reproduction rates, as well as the survival of individuals exposed from eggs and/or juveniles (J1) onwards. Exposure to SDS significantly affected the growth and reproduction rates of both species. However, whereas growth and reproduction rates of D. dievengatensis were significantly enhanced at low and intermediate concentrations of SDS (0.001% and 0.003%), for L. marina both parameters were significantly reduced by all SDS concentrations tested (0.001%, 0.003% and 0.006%). Exposure to SDS did not affect the survival of adult nematodes of D. dievengatensis, while for L. marina, survival of males exposed to 0.006% SDS was significantly reduced compared to the control. Responses of the life-history traits growth, fecundity and survival did not exhibit clear trade-offs. The contrasting responses of D. dievengatensis and L. marina indicate that biologically and ecologically similar species can have remarkably distinct tolerances to stress, and that, in agreement with recent studies, rhabditid nematodes cannot a priori be considered very stress tolerant. Consequently, single species traits and phylogenetic relatedness are poor predictors of nematode responses to toxic stress posed by anthropogenic activities.

The potential effects of perturbations by Polycyclic Aromatic Hydrocarbons (PAHs) on nematode and macrobenthos assemblages were investigated using the Biological Traits Analysis (BTA). We sampled at tidal flats near an oil refinery and in a reference estuary. Morphological and ecological traits of benthic fauna were selected and analyzed in order to assess the contribution of PAHs concentrations, the proximity to the oil refinery, the sediment characteristics and interaction between these predictor variables on benthic fauna. Multivariate analyses (DISTLM and db-RDA), showed that a large fraction of functional and taxonomic variation of benthic assemblages was explained by the interaction between location and sediment characteristics. The interaction between ∑PAHs and sediment characteristics was relatively low but significant. The results showed that taxonomic and functional variability of benthic assemblages were driven by natural and anthropogenic variables and BTA was an important auxiliary tool for distinguishing these responses. The amount of variability explained by the model was higher for nematode assemblages than to macrofaunal assemblages, showing a potential higher sensitivity of this group to the predictor variables.

Natural pH values in coastal waters vary largely among locations, ecosystems, and time periods; still, there is an ongoing acidification trend. In this scenario, more acidic pH values can alter bioavailability of organic contaminants, to organisms. Despite this, interactive effects between pH and chemical substances are not usually considered in Ecological Risk Assessment protocols. This study investigated the effects of pH on the toxicity of a hydrophobic organic compound on a benthic community using a microcosm experiment setup to assess the response of nematode assemblages exposed to environmentally relevant concentrations of Irgarol at two natural pH conditions. Estuarine nematode assemblages were exposed to two concentrations of Irgarol at pH 7.0 and 8.0 for periods of 7 and 35 days. Lower diversity of nematode genera was observed at the highest tested Irgarol concentration (1281 ± 65 ng.g

Made available in DSpace on 2018-11-26T17:42:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The usual approaches used in ecological risk assessment have been based on individual and population level standard procedures. Although these have been important tools to assess adverse effects on ecosystems, they are generally simplified and therefore lack ecological realism. Microcosm studies using meiobenthic communities offer a good compromise between the complexity of the ecosystem and the often highly artificial settings of laboratory experiments. An experiment was designed to investigate the potential of the microcosm approach using meiofauna as a tool for ecotoxicological studies. The experiment tested the ecological effects of exposure to sewage-impacted pore water simultaneously at the community level using meiofauna microcosms and at the individual level using laboratory fecundity tests with the copepod Nitokra sp. Specifically, the experiment tested the toxicity of pore water from three sites according to a contamination gradient. Both approaches were efficient in detecting differences in toxicity between the less and more contaminated sites. However, only multivariate data from community analysis detected differences in the gradient of contamination. In addition to information about toxicity, the community level microcosm experiment gave indications about sensitive and tolerant species, indirect ecological effects, as well as raised hypothesis about contamination routes and bioavailability to be tested. Considering the importance of meiofauna for benthic ecosystems, the microcosm approach using natural meiobenthic communities might be a valuable addition as a higher tier approach in ecological risk assessment, providing highly relevant ecological information on the toxicity of contaminated sediments. Univ Fed Parana, Ctr Estudos Mar, Av Beira Mar S-N, BR-83255976 Pontal Do Sul, PR, Brazil Univ Sao Paulo, Ctr Biol Marinha, Rodovia Manoel Hypolito Rego,Km 131-5, BR-11600000 Sao Sebastiao, SP, Brazil Univ Fed Sao Paulo, Inst Mar, Rua Carvalho de Mendonca 144, BR-11070100 Santos, SP, Brazil Univ Estadual Paulista, Campus Litoral Paulista, BR-11330900 Sao Vicente Vicente, SP, Brazil Univ Estadual Paulista, Campus Litoral Paulista, BR-11330900 Sao Vicente Vicente, SP, Brazil CNPq: CNPq 308079/2015-9 FAPESP: 2009/11808-3

Cross-taxon congruence has been suggested as an efficient tool in conservation planning and biodiversity monitoring. It corresponds to the degree to which patterns in assemblage structure in a set of sites are similar among different taxonomic groups. If different groups ordinate the sampling sites similarly, they are concordant and this information is frequently used as an indicative that one group could be used as a surrogate for the other. Using spatiotemporal benthic data from a biodiverse coastal ecosystem (the Araca Bay in southeast Brazil), we first assessed if macro- and meiofaunal assemblages inhabiting marine soft-sediments show concordant patterns. Then, we used multi- and univariate analysis to examine the relationship of both groups with the environment. Macro- and meiofaunal assemblages exhibited strong congruent patterns in all periods analyzed. Moreover, both groups responded to similar environmental features and their ordination patterns matched those generated by the environmental data. These results show that the patterns of concordance are probably mediated by similar responses to environmental gradients. Overall, our results suggest the potential for use of the surrogacy approach in conservation planning and monitoring purposes of marine benthic biodiversity, and that macro- and meiofauna can be used as a surrogate for each other.

For marine benthic communities, environmental heterogeneity at small spatial scales are mostly due to biologically produced habitat heterogeneity and biotic interactions, while at larger spatial scales environmental factors may prevails over biotic features. In this study, we investigated how community structure and &beta, diversity of hard-bottom-associated meio- and macrofauna varied in relation to small-scale (cm&ndash, m) changes in biological substrate (an algae &ldquo, turf&rdquo, dominated by the macroalgae Gelidium sp., the macroalgae Caulerpa racemosa and the sponge Hymeniacidon heliophile) in a rocky shore and in relation to larger-scale (10&rsquo, s m) changes in environmental conditions of the same biological substrate (the macroalgae Bostrychia sp) in different habitats (rocky shore vs. mangrove roots). Results showed that both substrate identity and the surrounding environment were important in structuring the smaller-sized meiofauna, particularly the nematode assemblages, whereas the larger and more motile macrofauna was influenced only by larger-scale changes in the surrounding ecosystem. This implies that the macrofauna explores the environment in a larger spatial scale compared to the meiofauna, suggesting that effects of spatial heterogeneity on communities are dependent on organism size and mobility. Changes in taxa composition between environments and substrates highlight the importance of habitat diversity at different scales for maintaining the diversity of the associated fauna.

Studies which showed the influence of organic carbon on the toxicity of sediment-associated contaminants on benthic invertebrates suggest this was primarily due to its influence on the interstitial water concentrations of the contaminant. A higher organic content offers more binding sites for organic contaminants, which means lower toxicity for organisms whose exposure route is mainly through contaminated interstitial water. However, a higher organic content in the sediment could mean a higher toxicity for deposit-feeding organisms, which can assimilate the contaminant by ingestion of contaminated particles. To investigate the influence of sedimentary organic carbon content on the toxicity of an organic contaminant on a benthic community, a microcosm experiment was carried out where natural nematode assemblages were exposed to three concentrations of Irgarol in sediments with two different levels of organic carbon for 7 and 35 days. The response of the nematode assemblage to sediment contamination by Irgarol differed between organically “Lower organic carbon” and “Higher organic carbon” sediments. Responses were genus specific and although community composition was the same in both sediments in the beginning of the assay, contamination by Irgarol affected different genera at each sediment type. Also, the differential amount of organic carbon promoted responses of different functional groups. In Lower organic carbon sediments, contaminated treatments showed lower abundances of the genus Viscosia and the group of predacious nematodes, which were probably affected by an increased availability of Irgarol in the interstitial water in this treatment. In Higher organic carbon sediments, the group of deposit-feeders were mainly affected, suggesting the ingestion of contaminated food as the main route of contamination in this condition. These results indicate that the bioavailability of toxic substances in sediments is not only determined by their partitioning between the different phases of the sediment but also by the organism’s trophic ecology.

The present study compared the short-term effects of a diesel oil spill on the strucure and function of nematode and macrobenthic assemblages between tidal flats with different history of exposure to oil perturbation. A manipulative field experiment was conducted, where oil exposed treatments were contrasted with controls, during four successive times, two before and two after the oil spills. During the oil spill the death and the presence of diverse debilitated macrofaunal organisms were observed in the oil treatments. However, 24 h later no significant changes were identified, suggesting that the impacted plots were quickly recolonized. Nematode assemblages showed a decrease in overall density and an increase of r-strategist traits such as non-selective deposit feeders and colonizers at perturbed treatments from one of the historically non-perturbed tidal flats. We discuss the mechanisms responsible by distinctive patterns of response observed between the two benthic components.

The literature on the use of marine nematodes as bioindicators of anthropogenic impact is extensive. Nevertheless, review studies have reported a high degree of variability among results and no consistent overall pattern has so far emerged. This lack of congruence might be partially because hypotheses formulation in environmental assessment studies has been largely inductive or abductive and not deductive or hypothesis-driven. In the present study, we emphasize the need of using hypothesis-driven designs and conceptual models in impact assessment studies. Hypotheses for individual and population level studies can be derived from the dynamic energy budget model (DEB). By means of differential equations, DEB model can infer whether a stressor promotes a shift in energy allocation along the life history of the individuals. For community/assemblage level studies, the predictions of the dynamic equilibrium model (DEM) for species richness is presented and extended for abundance, evenness, taxonomic distinctness, and changes in assemblage structure and sample dispersion. While it is predicted that species richness peaks at intermediate levels of disturbances and enrichment, evenness decreases with increasing disturbances and reducing enrichment/pollutant concentrations. Based on DEM,enrichment and pollutants may promote change in community structure by favoring the tolerant species, while physical disturbances may promote sample dispersion as a result of unselective mortality. Finally, we discuss the benefits of using niche-based models to select the indicator species, instead of using classical ordination methods, twinspan and similarity percentage analysis. The selection of indicator species have to be independent from the other species and must consider the set of environmental conditions. The use of conceptual models to select the best ecological indicators is highly recommended. It allows a logical way of testing for causalities and of scaling the different studies for comparisons.

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.

Made available in DSpace on 2022-04-29T07:26:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-08 After the Tributyltin world ban, Irgarol 1051 and Diuron have been the most commonly used biocides in antifouling paints. When adsorbed to suspended particulate matter or introduced as paint particles, these compounds accumulate in marine sediments and potentially cause ecological damage to benthic organisms. Therefore, a microcosm experiment was designed to evaluate the effects of Irgarol 1051 and Diuron, individually, on a meiofaunal community with emphasis on the dominant nematode assemblages. The experiment tested two factors: Treatment (two types of controls and three environmentally relevant concentrations of each contaminant) and Exposure time (5, 15 and 30 days). Significant declines in meiofauna density, nematode species richness and diversity, and changes in multivariate community structure were observed for both biocides at all exposure levels when compared to controls. Decreases occurred early on, within five days of exposure, which suggests that mortality, and not sub-lethal effects, has befallen upon the organisms. Sediment chlorophyll a and pheopigment concentrations, and redox potential were monitored to verify any indirect effects to the fauna through changes in the environment and results gave no indications of such mediated effects pointing to a direct toxic effect of both Irgarol and Diuron on the meiofauna. Although contaminated treatments showed a significant decline in the relative abundances of a particular functional group represented by the larger, longer-lived species, we did not observe the typical expected switch to smaller, more opportunistic taxa. Indeed, differences between controls and contaminated treatments were mainly due to an overall reduction in densities of the most abundant species in contaminated treatments. The high mortality (ca. 50% decline in total abundances), changes in community structure and species loss observed at biocide levels frequently encountered in the field suggest Irgarol and Diuron as a threat to benthic communities. Such severe effects contrast to other studies that have detected lower impacts, suggesting the free-living nematodes as potential indicators of marine pollution and the microcosm approach using natural communities as an impending tool for ecotoxicological studies. Instituto Do Mar da Universidade Federal de São Paulo, Av. Alm. Saldanha da Gama, 89 Centro de Biologia Marinha da Universidade de São Paulo, Rodovia Manoel Hypólito Do Rego, km 131.5 Instituto Oceanografico da Universidade de Sao Paulo, Praca Do Oceanografico, 191, Cidade Universitária Universidade Estadual de São Paulo, Campus Experimental Do Litoral Paulista, Praça Infante Dom Henrique, s/n Centro de Estudos Do Mar da Universidade Federal Do Paraná, Av. Beira-mar, s/n Universidade Estadual de São Paulo, Campus Experimental Do Litoral Paulista, Praça Infante Dom Henrique, s/n

The majority of studies have advocated that diversity of marine nematodes increases with increasing sediment grain size, although the opposite trend has also been suggested. The controversy is partially caused by not taking into account the effect of density on patterns of diversity and by analyzing datasets from different environments. The present study investigated nematode assemblages from sediments varying from very fine sand (mean grain size of 0.12 mm) to very coarse sand (1 mm) in shallow sublittoral marine environments. Contrary to previous studies, species richness was constant along the granulometric spectrum, despite significant changes in composition. The dominant genera were separated into five groups according to their optimum distribution and there was little overlap between these groups. Concepts from the niche theory explain to some extent the observed patterns. For instance, some of the coexisting genera were from different feeding types.

The impact of large food falls and carrion on meiobenthic communities remains little understood. The objective of the present study was to investigate whether the carcass of a stingray, encountered fortuitously in an Australian estuary, affects the underlying meiobenthic community, in particular nematode assemblages. The integrity of the skeleton and the low redox values observed under the carcass suggest that the cadaver had been slowly and chiefly decomposed by microbes. The abundance and number of meiofaunal taxa, as well as nematode abundance and nematode- species richness, were significantly lower under the carcass when compared to samples outside the carcass. Nonetheless, a few nematode species, typical of hypoxic/anoxic sediments, were more abun- dant under the carcass. Interestingly, all these species were absent or rare in samples near, but not under, the carcass, suggesting that they may take advantage of the reduced environment created by the carcass and the consequent lack of competition to prosper. As observed for other marine environ- ments, carcasses in estuaries create a microhabitat that supports a characteristic meiobenthic fauna, distinct from those inhabiting the surrounding sediments, but similar to those of reduced habitats.

Seagrass beds have higher biomass, abundance, diversity and productivity of benthic organisms than unvegetated sediments. However, to date most studies have analysed only the macrofaunal component and ignored the abundant meiofauna present in seagrass meadows. This study was designed to test if meiobenthic communities, especially the free-living nematodes, differed between seagrass beds and unvegetated sediments. Sediment samples from beds of the eelgrass Zostera capricorni and nearby unvegetated sediments were collected in three estuaries along the coast of New South Wales, Australia. Results showed that sediments below the seagrass were finer, with a higher content of organic material and were less oxygenated than sediments without seagrass. Univariate measures of the fauna (i.e. abundance, diversity and taxa richness of total meiofauna and nematode assemblages) did not differ between vegetated and unvegetated sediments. However multivariate analysis of meiofaunal higher taxa showed significant differences between the two habitats, largely due to the presence and absence of certain taxa. Amphipods, tanaidacea, ostracods, hydrozoans and isopods occurred mainly in unvegetated sediments, while kinorhyncs, polychaetes, gastrotrichs and turbellarians were more abundant in vegetated sediments. Regarding the nematode assemblages, 32.4% of the species were restricted to Z. capricorni and 25% only occurred in unvegetated sediments, this suggests that each habitat is characterized by a particular suite of species. Epistrate feeding nematodes were more abundant in seagrass beds, and it is suggested that they graze on the microphytobenthos which accumulates underneath the seagrass. Most of the genera that characterized these estuarine unvegetated sediments are also commonly found on exposed sandy beaches. This may be explained by the fact that Australian estuaries have very little input of freshwater and experience marine conditions for most of the year. This study demonstrates that the seagrass and unvegetated sediments have discrete meiofaunal communities, with little overlap in species composition.

A variety of analytical techniques were used to quantify and describe small-scale (centimetre to decimetre) spatial patterns of meiofauna taxa, with emphasis on nematode species, at a bathyal site in the Arctic deep sea. Three cores (10-cm diameter) taken from the same multicorer were each subsampled as 12 contiguous subcores(1.2-cm diameter) for meiofauna and 16 contiguous subcores (0.9-cm diameter) for bacteria (eight subcores) and phytodetritus (chl a and phaeopigment concentration) (eight subcores). Coefficients of variation and the variance component from PERMANOVA were estimated to compare variability between cores (20–50 cm) versus within cores (=10 cm). Both methods showed that spatial variation within cores contributed the main part of total heterogeneity for all parameters, while differences between cores were less important. To further investigate distribution patterns at this small scale (=10 cm), indices of dispersion were calculated and autocorrelation analyses were performed on the complete data set. Abundances of nematodes, naupliiand 65.5% of the nematode species were significantly aggregated at the scale of subcores (2 cm). Nematode species aggregations were discordant on the small scale, suggesting that processes maintaining diversity in the deep sea can be expected to operate at scales smaller than 10 cm. Autocorrelograms suggested that nematode patch sizes were smaller than 4 cm2, while adult harpacticoid copepods and nauplii showed aggregations of ca. 9–25 cm2 and 64 cm2, respectively. Significant spatial autocorrelation at the core scale was also observed for 24 nematode species. These species were grouped in ten different spatial patterns according to their scale of heterogeneity. The spatial patterns observed for the meiobenthos were neither explained by the concentration of chloroplastic pigments nor by bacterial densities. Nevertheless, observations on nematode morphology suggest that morphological characters linked to their locomotion and feeding behaviour may be involved in pattern formation. Finally, our data provide evidence that studies based on few replicates to characterise large-scale or long-term patterns of deep-sea benthic communities may be confounded by inadequate assessment of small-scale variability.

The response of the meiofauna communities to the discharge of synthetic-based mud (SBM) cuttings from an exploratory drill was analyzed in a deep-sea site (mean depth of 890 m) in the Campos Basin, southeast Brazil. A total of 159 samples were taken on three sampling cruises: one pre- and two post-drilling (1 month and 1 year after drilling). One month after drilling, significant decreases in the meiofauna density and number of taxa were observed, as well as in nematode density and richness (number of families and genera); conversely, relative abundances of non-selective deposit-feeding nematodes, particularly the genus Sabatieria, increased significantly. Univariate and multivariate analyses indicate that the impacts on meiofauna were not restricted to a potential area of impact predicted by a model of cuttings dispersal; meiofauna changes just after the drilling agreed with the model in showing northward dispersal but over a larger area. The meiofauna, however, showed a weak correlation with the analyzed chemical parameters, such as hydrocarbon and metal concentrations. The results suggest that the effects of SBM drill cutting discharge on the meiofauna were probably related to physical changes in the substrate. Twelve months after drilling, most of the values of the meiofauna descriptors had returned to pre-impact period values. Nonetheless, the multivariate structure of meiofauna community was still significantly different, and the number of meiofauna taxa, densities of copepods, and epigrowth-feeder nematodes increased significantly. The increase of superficial forms of meiofauna in the deep sea may last until complete disaggregation of the cuttings.

Caging experiments were performed at the Arctic deep-sea long-term observatory HAUSGARTEN to investigate the effects of megafauna exclusion on nematode assemblages. Six experimental cages were deployed at 2500 m water depth and sampled after 4 years for meiofauna and a series of sediment parameters. With the exception of chlorophyll a and phaeopigments, which were significantly higher inside the cages, sediment parameters did not differ between inside and outside the cages. Yet multivariate analysis of the sedimentary environment showed a higher variability outside the cages, indicating higher environmental heterogeneity in the presence of megafauna. Nematode densities (aver. 1516 ind 10 cm −2 ) were significantly higher in sediments from inside the cages, whereas total number of species (aver. 70 sp.), Shannon–Wiener diversity (aver. 3.4) and Pielou evenness (aver. 0.8) did not differ between the two treatments. Also differences in faunal multivariate structure between cage and control samples were not significant. Nevertheless, Fisher's alpha diversity, the number of nematode genera and taxonomic distinctness showed significantly higher values outside the cages. Since univariate measures are often insensitive to changes in community structure, and interpretation of the multivariate analysis was confounded by the large number of rare species, we further analysed our data by dividing the species into three groups of frequency (frequent, intermediate and occasional) and into three groups of abundance (dominant, sub-dominant and scarce). Results from this analysis revealed that the higher nematode abundances inside the cages were mainly due to an increase in density of scarce species that were either frequent or intermediate in frequency. In contrast, occasional species were adversely affected. These results lead us to believe that it is mainly the frequent species occurring in low densities that take advantage of favourable conditions (i.e. lack of disturbance or increased phytodetritus) in the deep sea. The higher taxonomic distinctness, Fisher's diversity, and number of genera at the control sites, together with the fact that they were environmentally more heterogeneous, suggest that megafaunal organisms play an important role in creating microhabitats in the sediment and significantly influence deep-sea nematode assemblages. However, the lack of any changes in species richness inside the cages after 4 years suggests that they cannot fully account for the maintenance of the remarkable high levels of species coexistence in the deep sea. The key is more likely to be found in evolutionary history than actual ecology.

Present theories of deep-sea community organization recognize the importance of small-scale biological disturbances, originated partly from the activities of epibenthic megafaunal organisms, in maintaining high benthic biodiversity in the deep sea. However, due to technical difficulties, in situ experimental studies to test hypotheses in the deep sea are lacking. The objective of the present study was to evaluate the potential of cages as tools for studying the importance of epibenthic megafauna for deep-sea benthic communities. Using the deep-diving Remotely Operated Vehicle (ROV) “VICTOR 6000”, six experimental cages were deployed at the sea floor at 2500 m water depth and sampled after 2 years (2y) and 4 years (4y) for a variety of sediment parameters in order to test for caging artefacts. Photo and video footage from both experiments showed that the cages were efficient at excluding the targeted fauna. The cage also proved to be appropriate to deep-sea studies considering the fact that there was no fouling on the cages and no evidence of any organism establishing residence on or adjacent to it. Environmental changes inside the cages were dependent on the experimental period analysed. In the 4y experiment, chlorophyll a concentrations were higher in the uppermost centimeter of sediment inside cages whereas in the 2y experiment, it did not differ between inside and outside. Although the cages caused some changes to the sedimentary regime, they are relatively minor compared to similar studies in shallow water. The only parameter that was significantly higher under cages at both experiments was the concentration of phaeopigments. Since the epibenthic megafauna at our study site can potentially affect phytodetritus distribution and availability at the seafloor (e.g. via consumption, disaggregation and burial), we suggest that their exclusion was, at least in part, responsible for the increases in pigment concentrations. Cages might be suitable tools to study the long-term effects of disturbances caused by megafaunal organisms on the diversity and community structure of smaller-sized organisms in the deep sea, although further work employing partial cage controls, greater replication, and evaluating faunal components will be essential to unequivocally establish their utility. © 2007 Elsevier B.V. All rights reserved.

Studies on cannibalism in harpacticoid copepods are restricted to predation on naupliar larvae in rock-pool harpacticoids of the genus Tigriopus. An earlier experimental study on the Mediterranean copepod Tigriopus fulvus indicated that females recognized their own larvae and preferentially preyed on nauplii other than their own. In a series of laboratory experiments, we tested if there were differences in naupliar predation as a function of crowding, food level and sex in Tigriopus brevicornis and T. fulvus. Results show that cannibalism was restricted to the first larval stages (N1 and N2). Both food availability and adult density significantly affected the predation rate. Contrary to earlier suggestions, adult males also preyed on the nauplii. We found no evidence that adults spare their own offspring, for neither T. fulvus nor T. brevicornis.This is in accordance with what one would expect for species having the life history characteristics of Tigriopus, i.e.: multiple broods and large number of offspring. Earlier results indicating parental care in Tigriopus must be taken with caution.

There is little meiofauna data from the southwest Atlantic, and especially lacking are studies examining deep-sea communities. In this study, the structure of meiofauna communities, particularly nematodes, was analyzed from data derived from 101 samples (48 samples on the continental-slope and 53 samples at a deep-sea site) collected at Campos Basin, SE Brazil. Differences in the meiofauna densities and in the number of taxa between continental slope and deep-sea sites depended on the taxonomic level examined. While total meiofauna abundance did not differ significantly between sites, nematode densities were significantly higher in the deep sea (mean of 157 inds.10 cm−2) than on the slope (mean of 129 inds.10 cm−2). The number of meiofauna taxa was significantly higher at the continental slope site. Yet for the most abundant meiofaunal group, the nematodes, whilst the number of families did not differ between continental slope and deep sites, the number of genera was significantly higher in the deep sea. The remarkable resemblance between the dominant nematodes (Halalaimus, Acantholaimus, Daptonema, Theristus and Sabatieria) from SE Brazil and other deep sea studies confirmed earlier suggestions of a typical deep-sea nematode community with a broad geographical distribution. Multivariate analysis derived from meiofauna and nematode data showed that the structure of the fauna differed significantly between sites. Correlations detected between meiofauna and some sediment properties, such as grain size and sediment heterogeneity, although significant, were very low.

The effects of cold fronts in a shallow sublittoral system at the Island of Santa Catarina, S Brazil, were investigated in June 2002. Atmospheric, pelagic and benthic data were taken daily covering the days before, during and after the passage of two cold fronts, summing 8 days of sampling. The results clearly showed that the passage of cold fronts, a short-term event, promote changes in the whole shallow sublittoral system, from the pelagic to the benthic one. At the pelagic system, both the cold fronts changed seston, nutrients and chlorophyll a concentrations. The increase in chlorophyll a just after the cold fronts probably resulted from phytoplankton retention and accumulation next to the coast, the microphytobenthos resuspension and the increase in nutrients availability. At the benthic system, sediment features and all of the three benthic components studied- microphytobenthos, meiofauna and macrofauna were also affected by the passage of the cold fronts. The sediments from the studied site suffered a clear homogenizing process. While medium grain size decreased, fine sand percentages gradually increased after the cold front passage. In contrast, sediment organic content was significantly higher just after the first cold front. The effects of the passage of cold fronts in the benthos were dependent on the biological component, the vertical distribution and on the cold front magnitude. The sediment chlorophyll a concentration was lower exactly one day after both cold fronts passage while phaeopigments were significantly higher. The results of the study showed that both macrofauna and meiofauna, particularly nematodes, of the upper layer of the sediment exhibited a decrease in density and number of taxa during the passage of the first frontal system. The nematodes, more than suffering erosion and transport, showed a vertical migration process to the deeper layers of the sediment during the passage of the cold fronts.

The composition and abundance of the meiofauna and macrofauna were studied in a survey carried out within 6 locations in a mangrove at the Island of Santa Catarina, South Brazil. Nine meiofaunal taxa were registered with densities ranging between 77 and 1589 inds.10 cm−2. The nematodes, composed by 94 putative species (86 genera), largely dominated the meiofauna. The most abundant genera were Haliplectus (Haliplectidae), Anoplostoma (Anoplostomatidae) and Terschillingia (Linhomoidae). Contrary to the meiofauna, the macrofauna showed a low number of taxa (only 17 recorded) and abundance (up 7250 inds.m−2). The macrofauna was mainly composed by deposit feeders, and numerically dominated by oligochaetes and capitellid polychaetes. For both components, differences in the composition and abundance along the sampling sites were significant but not primarily related to the typical variations along estuaries, such as salinity. The results of the stepwise multiple regression analyses showed that the detritus biomass (ash-free dry weight) was the most important predictor of faunal densities and diversity. The clear relationship between detritus and fauna, together with the contrasting community structure of the two component of the benthos suggest that the meiofauna showed a high efficiency in exploiting the micro-habitat created by the presence of the detritus. Yet the macrofauna, potentially the main consumer of the debris, is negatively affected by their low palatability and poor nutritive value.

We investigated the effects of the habitat-modifying green algae Caulerpa taxifolia on meiobenthic communities along the coast of New South Wales, Australia. Samples were taken from unvegetated sediments, sediments underneath the native seagrass Zostera capricorni, and sediments invaded by C. taxifolia at 3 sites along the coast. Meiofaunal responses to invasion varied in type and magnitude depending on the site, ranging from a slight increase to a substantial reduction in meiofauna and nematode abundances and diversity. The multivariate structure of meiofauna communities and nematode assemblages, in particular, differed significantly in sediments invaded by C. taxifolia when compared to native habitats, but the magnitude of this dissimilarity differed between the sites. These differential responses of meiofauna to C. taxifolia were explained by different sediment redox potentials. Sediments with low redox potential showed significantly lower fauna abundances, lower numbers of meiofaunal taxa and nematode species and more distinct assemblages. The response of meiofauna to C. taxifolia also depended on spatial scale. Whereas significant loss of benthic biodiversity was observed locally at one of the sites, at the larger scale C. taxifolia promoted an overall increase in nematode species richness by favouring species that were absent from the native environments. Finally, we suggest there might be some time-lags associated with the impacts of C. taxifolia and point to the importance of considering the time since invasion when evaluating the impact of invasive species.

The present study investigates the effects of drill cutting discharges on the structure of meiofauna communities in an area of the shelf break at Campos Basin, Southeast Brazil. Drilling activities were operated, in a first phase, with water-based fluid and, in a second phase, with synthetic fluid paraffin-based (NAF-III). A total of 135 samples taken at a pre-drilling situation (MS1) and two post-drilling moments (MS2 and MS3—3 and 22 months post-drilling, respectively) were analyzed. Effects on meiofauna were dependent on two main factors: 1—the impact received during drilling operation, if water-based or synthetic/water-based drilling fluid and 2—the background state, if it already presented signs of previous drilling activities or not. Based on univariate and multivariate analysis, there were evidences that the most affected area after drilling was those under the influence of synthetic-based fluid and that already had signs of previous drillings activities. The region impacted only by water-based fluid was less affected and the only one that completely recovered after 22 months. Nematodes and copepods had different responses to the impact. While copepods flourish in the impacted area and recovered 22 months after drilling, nematodes were adversely affected shortly after drilling and the community structure only recovered where hydrocarbons had been depleted.

An on-board experiment was performed during a research cruise to investigate the abil- ity of deep-sea nematode species to actively colonise defaunated sediments. Small cylinders of 500 µm wire mesh filled with defaunated sediment were inserted into microcosms containing sediment with indigenous meiofauna collected from 1300 m depth in the Arctic Ocean. The defaunated sediments were either enriched with the diatom Thalassiosira weissflogii, or remained unenriched. Samples from the defaunated sediment were taken after 9 and 17 d. As controls, microcosms with sediment contain- ing the indigenous meiofauna but without an internal cylinder were also sampled at each time inter- val. Nematodes colonised both enriched and unenriched sediments with abundances of up to 20% of the controls. Irrespective of the time of sampling, abundance and number of species were significantly higher in the enriched treatment, suggesting that the presence of food enhances colonisation and re- silience. Nematode assemblages in the defaunated sediments were species-rich and differed from the controls. The majority of colonising species were rare or undetectable in the controls, suggesting that episodic disturbances may be necessary for their persistence in deep sea sediments. Colonisation was in part determined by species characteristics such as size and motility. At the same time, a large number of different species colonised the empty cylinders, resulting in poor similarity in community composition between replicates, particularly between samples enriched with diatoms. Our results in- dicate a poor predictability of community composition of recently disturbed sediments despite highly reproducible abundance and diversity patterns and lends experimental support to the existence of a spatio-temporal mosaic that emerges from highly localised colonisation patterns.

The role and quantitative importance of free-living nematodes in marine and estuarine soft sediments remain enigmatic for lack of empirical evidence on the feeding habits and trophic position of most nematode species. Here we use natural abundances of carbon and nitrogen stable isotopes of some abundant nematode species/genera from estuarine intertidal sediments to assess their trophic level and major food sources. In all stations, δ15N of different dominant nematode species/genera spanned a range of 3.6 to 6.3 ppt, indicating that at least two trophic levels were represented. The large nematodes Enoplus brevis, Enoploides longispiculosus and Adoncholaimus fuscus consistently had high δ15N, in line with mouth-morphology based predictions and empirical evidence on their predacious feeding modes. Daptonema sp., Metachromadora remanei, Praeacanthonchus punctatus and ‘Chromadoridae’ (dominated by Ptycholaimellus ponticus) had comparatively lower δ15N, and δ13C suggesting that microphytobenthos (MPB) is their major carbon source, although freshly sedimented particulate organic matter may also contribute to their nutrition in silty sediments. The trophic position of Sphaerolaimus sp., a genus with documented predacious feeding mode, was ambiguous. Ascolaimus elongatus had δ15N signatures indicating a predacious ecology, which is at variance with expectations from existing feeding type classifications. Our study shows that—despite limitations imposed by the biomass requirements for EA-IRMS (elemental analyser—isotope ratio mass spectrometry)—natural isotope abundances of carbon and nitrogen are powerful tools to unravel trophic structure within nematode communities. At the same time, the prominence of different trophic levels results in a large span of δ15N, largely invalidating the use of nitrogen isotope abundances to assess food sources and trophic level of whole nematode communities.

Canopy-forming algae may provide trophic resources and structural complexity for a wide array of mobile invertebrates, which in turn may sustain pelagic consumers of higher trophic levels. However, algal canopies are declining worldwide and replaced by less-complex macroalgal turfs which may dominate reefscapes. Here, we first compare the assemblages of mobile invertebrates associated to main canopy-forming (Sargassum spp. and Galaxaura marginata) and turf-forming algae (filamentous and articulated coralline turf), and then assess if, and how, canopy-dwelling invertebrate assemblages drift away from the turf baseline during the blooming season of the main canopy habitat (Sargassum). Abundance, biomass and diversity almost always differed between canopies and turfs at sampling sites, while differences within main functional algal types were nearly absent. But, surprisingly, none of those overall metrics varied in any consistent way across sampling sites. Differently, the assemblage structure consistently differed between canopies and turfs, with hard-bodied (as gastropods and brachyuran crabs), and soft-bodied (mainly polychaetes and flatworms) invertebrates characterizing canopy and turf assemblages, respectively. The divergence between invertebrate assemblages at canopies and turfs increased as the canopy-blooming season advanced. Notably, while the invertebrate assemblage structure remained unaltered at turfs, early-successional brittle stars and amphipods were followed by hard-shelled gastropods, bivalves and ostracods in Sargassum, where they become dominant and decreased diversity later on within the season. As hard-shelled prey are preferred items for the main invertivore fish species in the area, results indicate that canopies play a particularly important role in the provisioning of trophic resources to pelagic consumers. As algas formadoras de dossel podem fornecer recursos tróficos e complexidade estrutural para uma ampla gama de invertebrados móveis, que por sua vez podem sustentar consumidores pelágicos de níveis tróficos mais altos. No entanto, os dosséis de algas estão declinando em todo o mundo e substituídos por tapetes de macroalgas menos complexos, que podem dominar as paisagens dos recifes. Aqui, comparamos primeiro associações de invertebrados móveis associadas às principais algas formadoras de dossel (Sargassum spp. e Galaxaura marginata) e algas formadoras de tapetes (filamentoso e calcário articulado) e depois avaliamos se, e como, as associações de invertebrados que habitam o dossel flutuam afastando da linha de base dos tapetes durante a estação de floração do principal habitat de dossel (Sargassum). Abundância, biomassa e diversidade quase sempre diferiram entre dosséis e tapetes nos locais de amostragem, enquanto as diferenças nos principais tipos de algas funcionais estavam quase ausentes. Surpreendentemente, porém, nenhuma dessas métricas gerais variou de maneira consistente nos locais de amostragem. Diferentemente, a estrutura da associação diferia consistentemente entre dosséis e tapetes, com invertebrados de exoesqueleto rígido (como gastrópodes e caranguejos braquiúros) e de corpo mole (principalmente poliquetas e platelmintos) caracterizando associações de dossel e tapete, respectivamente. A divergência entre associações de invertebrados em dosséis e tapetes aumentou à medida que a estação de floração do dossel avançava. Notavelmente, enquanto a estrutura da associação de invertebrados permaneceu inalterada nos tapetes, a sucessão rápida de ofiuróides e anfípodes foram seguidos por gastrópodes, bivalves e ostracodas de concha rígida em Sargassum, onde se tornaram dominantes e diminuíram a diversidade mais tarde na temporada. Como presas de exoesqueleto rígido são itens preferenciais para as principais espécies de peixes invertívoros da região, os resultados indicam que os dosséis desempenham um papel particularmente importante no fornecimento de recursos tróficos aos consumidores pelágicos.

Free-living marine nematodes are the most ubiquitous, abundant and diverse meiofaunal component of benthic communities. These are excellent model organisms, due to its short life span, wide availability and feasibility to cultivate with minimum laboratory facilities. In this study, a population of Diplolaimella dievengatensis Jacobs 1991 (Nematoda, Monhysteridae) from the relatively Pristine estuary of the Guaratuba River in São Paulo, Brazil was isolated and cultivated. The goals were; i- to apply an integrative taxonomic approach in order to compare this population from Brazil with another from the species type-locality in the Belgian Coast, with regard to morphological, life-cycle and the 18S gene of the rDNA molecular data; and ii- to compare, at the light of life history theory, the responses of life history parameters such as; fecundity, growth and survivorship of D. dievengatensis (here as a slower species) and Litoditis marina (Bastian, 1865) (Nematoda, Rhabditidae) (as a faster species) under sublethal exposition to the sodium dodecyl sulfate (SDS) surfactant. The population from Brazil was similar to that from Belgium coast in all parameters. Although morphometric analyses considered the Brazilian D. dievengatensis isometrically larger than the Belgian population regarding some characters, the presence of all diagnostic characters confirmed the similarity of both species. The life-cycle, hatching time, final body length, and biomass parameters were similar in both populations, in which females were larger than males. The population growth, measured as intrinsic rate of natural increase was slightly higher for the D. dievengatensis from Brazil (rm=0.41), than the European population (rm =0.348). Molecular comparison on Genbank showed 99.4% of similarity between both populations, indicating therefore, that D. dievengatensis from Brazil is similar to those from Belgium. In the chapter ii, both species responded differently to SDS exposition. Growth and reproduction rate of D. dievengatensis surprisingly were enhanced at low and intermediate concentrations of SDS (0.001 and 0.003%), while for L. marina these parameters were reduced in all SDS concentrations tested (0.001, 0.003 and 0.006%). The SDS did not affect the survivorship of adults of the slower specie. On the other hand, survivorship of adults of the fast species was significantly affected by SDS and this effect was dependent on adult gender, with reduced rates of males exposed to 0.006% SDS. Although both species are located nearby along the fast-slow continuum, they responded distinctly to of the toxic SDS effect. Effects over L. marina met the trend of faster species in allocating fewer investments in defenses against physiological injuries and on their own somatic maintenance. We propose that the apparent lower resistance of this faster species under stress at the individual level is balanced by their higher reproductive rates, conferring higher resilience to this species at the population level. Finally, it was demonstrated that the marine nematode D. dievengatensis is an important native model organism which can be used in a wide range of studies and experimental tests. Identifying and understanding differential effects of stress in the context of life-history theory is an important aspect which enhanced our understanding about the threats posed by anthropogenic activities on natural communities Nematodas marinhos de vida livre são o mais onipresentes, abundantes e diversos componentes da meiofauna em comunidades bênticas. São excelentes organismos modelo devido a seu curto ciclo de vida, ampla disponibilidade e viabilidade de cultivo com mínima estrutura laboratorial. Neste estudo, uma população de Diplolaimella dievengatensis Jacobs 1991 (Nematoda, Monhysteridae) do estuário relativamente prístino do rio Guaratuba, São Paulo, Brasil foi isolada e cultivada. Os objetivos foram: ii- aplicar uma abordagem taxonômica integrativa a fim de comparar esta população do Brasil com outra da localidade tipo dessa espécie, da costa da Bélgica, com relação à dados morfológicos, do ciclo de vida e molecular do gene 18S do rDNA; e ii-comparar, à luz da teoria da historia de vida, repostas de parâmetros do ciclo de vida tais como: fecundidade, crescimento e sobrevivência de D. dievengatensis (aqui como espécies mais lenta) e Litoditis marina (Bastian, 1865) (Nematoda, Rhabditidae) (como espécie rápida) sob exposição subletal ao surfactante dodecil sulfato de sódio (DSS) . A população do Brasil foi similar a da costa da Bélgica em todos os parâmetros. Embora analises morfométricas consideraram D. dievengatensis do Brasil isometricamente maior que a população belga em relação em algumas características, a presença de todos os caracteres diagnósticos confirmaram a similaridade de ambas as espécies. Os parâmetros de ciclo de vida, tempo de eclosão, comprimento corporal final e biomassa foram similares em ambas as populações, nas quais fêmeas foram maiores que machos. Crescimento populacional, mensurado como taxa intrínseca de crescimento natural foi ligeiramente mais alta para D. dievengatensisdo Brasil (rm=0.41), que para a população europeia (rm=0.348). Comparações moleculares no Genbank mostraram 99.4% de similaridade entre ambas populações, indicando portanto que a população do Brasil é similar a D. dievengatensis belga. No capítulo ii, ambas as espécies responderam distintamente a exposição ao SDS. Supreendentemente as taxas de crescimento e de reprodução de D. dievengatensis foram incrementadas sob concentrações mais baixas e intermediárias (0.001 e 0.003%), enquanto para L. marina esses parâmetros foram reduzidos em todas as concentrações de DSS testadas (0.001, 0.003 e 0.006%). O DSS não afetou a sobrevivência de adultos da espécie mais lenta. Por outro lado, a sobrevivência de adultos da espécie mais rápida foi significativamente afetada pelo SDS e esse efeito foi dependente do sexo, com taxas reduzidas em machos expostos a 0.006 % de DSS. Embora ambas as espécies estejam proximamente dispostas ao longo do gradiente \"rápido-lento\", elas responderam diferentemente ao efeito tóxico do DSS. Efeitos sobre L marina se enquadram no padrão de espécies mais rápidas ao alocar menores investimentos para as defesas contra danos fisiológicos e para sua própria manutenção somática. Nós propomos que a aparente menor resistência desta espécie rápida sob estresse ao nível individual é balanceada por suas altas taxas reprodutivas, conferindo mais alta resiliência a essa espécie ao nível populacional. Por fim, foi demonstrado que D. dievengatensis é um importante organismo modelo nativo que pode ser usado em uma ampla diversidade estudos e testes experimentais. Identificar e compreender diferentes efeitos do estresse dentro do contexto da teoria da história de vida é um aspecto importante, o qual tem aumentado nosso conhecimento sobre as ameaças de atividades antropogênicas sobre comunidades naturais

A região da península Antártica possui uma plataforma profunda com características similares ao mar profundo e é uma região muito afetada pela variabilidade climática. Abaixo dos 60 m de profundidade, a meiofauna da baía do Almirantado e do talude adjacente no estreito de Bransfield é desconhecida. Este trabalho visa caracterizar a comunidade da meiofauna, gerando um conhecimento de base sobre sua biodiversidade e estrutura, relacionando com as variáveis ambientais (tipo de sedimento e quantidade/qualidade do alimento). Foi avaliado como a composição e a densidade da meiofauna variaram com a profundidade (100 e 1100 m), verticalmente no sedimento (0-6 cm) e entre dois anos com características climáticas contrastantes (dez/2008 e dez/2009). Também foi analisada a biomassa e diversidade dos Nematoda em nível específico em dez/2008. A densidade da meiofauna e a biomassa de Nematoda foram altas em comparação com outros locais. Houve grande variação na densidade da meiofauna entre os anos. Em dez/2008, ano mais quente, com pouca influência da cobertura de gelo e maior produtividade primária, a densidade variou com a profundidade, sendo alta dentro da baía, com maior concentração de fitodetritos, e baixa no estreito de Bransfield, onde o sedimento foi mais grosso indicando maior hidrodinamismo. Já em dez/2009, ano muito frio, com cobertura de gelo extensa e prolongada, com baixa produtividade primária não houve variação batimétrica da densidade ou das variáveis ambientais. A densidade e diversidade foram mais altas no estrato superficial do sedimento. Foram identificados 83 gêneros de Nematoda, que foram distinguidos em 185 morfoespécies, sendo que a maioria é espécie nova. A diversidade de espécies de Nematoda foi alta, como tem sido reportado para outras regiões antárticas e de mar profundo. A biomassa total de Nematoda foi cinco vezes mais alta que a média mundial, e variou entre as profundidades da mesma forma que a densidade. A biomassa individual, no estrato 0-2 cm, foi baixa na baía e alta no estreito. A morfometria mostrou que os indivíduos são mais longos e finos nas maiores profundidades, tanto batimétrica quanto vertical. A distribuição da meiofauna e da biomassa de Nematoda na área pareceu ser mais afetada por processos físicos (correntes, ressuspensão, topografia íngreme) do que pela quantidade de alimento disponível. The Antarctic Peninsula has a deep shelf featuring similar conditions to the deep sea and it is highly affected by climatic variations. At Admiralty Bay and the adjacent slope in the Bransfield Strait, the meiofauna below 60 m depth is unknown. The present study aims to characterize the meiofauna community, and so generate a database on biodiversity and structure through the linkage to environmental variables (sediment type and quantity/quality of food). Composition and density of meiofauna have been evaluated across depth gradient (100 and 1100 m), sediment column (0-6 cm) and two years of contrasting climatic conditions (dec/2008 and dec/2009). Nematode biomass and diversity in specific level have been analyzed exclusively in the dec/2008 samples. Meiofauna density and nematode biomass were higher than in other localities. There was great variation of meiofauna density between the years. In dec/2008, density varied along the depth gradient: higher at the Admiralty Bay and lower at the Bransfield Strait, where the sediment was coarser (indicating high hydrodynamics). This year was the warmest, with weak influence of ice cover, high primary productivity and high phytodetritus concentration. Distinctively, in dec/2009, no bathymetric variation in meiofauna density or environmental variables was observed. This year was the coldest, with an extensive and enduring ice cover and low primary productivity. Density and diversity were higher in the superficial layer of the sediment. In total 83 nematode genera were found, comprising 185 morphospecies, mostly of new species. Species diversity of nematodes was elevated as reported in other Antarctic regions and in the deep sea. Nematode total biomass was five times higher than the global mean values, showing variation along the depth gradient. Individual biomass of layer 0-2 cm was low at the bay and high at the strait. Individuals were longer and thinner in deeper depths and sediment layers. Meiofauna and nematode biomass distributions seem to be more influenced by physical processes (currents, sediment ressuspension, steep topography) than by food availability.

O objetivo deste trabalho foi analisar a distribuição espaço-temporal de um representante da macrofauna de praias arenosas protegidas. As abordagens em diferentes escalas (mesoescala, microescala e escala temporal) foram empregadas. O gastrópode Olivella minuta, abundante na região entremarés da Baía do Araçá, foi utilizado para essas análises. Para o estudo em mesoescala, 16 estações foram demarcadas na região entremarés (julho/2009) e, em cada uma, foram coletadas 8 amostras biológicas e 3 de sedimento. Alguns fatores abióticos (carbonato de cálcio, matéria orgânica e coeficiente de seleção) influenciaram negativamente a abundância do gastrópode, enquanto relações entre O. minuta e as demais espécies da macrofauna não foram evidentes. Em microescala, em poças de maré (metros) e em \"ripple marks\" (centímetros) verificou-se que em escala de centímetros, o gastrópode foi mais abundante em locais com maior conteúdo de água no sedimento, enquanto em escala de metros a abundância não diferiu dentro e fora das poças. Em escala temporal, foram observadas flutuações mensais da densidade da população de O. minuta, com diminuição/ausência de indivíduos entre fevereiro e março, o que sugere a ocorrência de migrações e mortalidade. O presente trabalho mostrou que a distribuição desse gastrópode é influenciada por diferentes fatores que atuam em diferentes escalas. The objective of this study was to analyze the temporal and spatial distribution of one of the species representative of the macrofauna of sheltered sandy beaches. Measurements using different scales (mesoscale, microscale and time scale) were utilized. The gastropod Olivella minuta, which is abundant in the intertidal region of Baía do Araçá, was used for these analyses. For the mesoscale study, 16 stations were determined within the intertidal region (July/2009) and, in each station, 8 biological samples and 3 samples of sediment were collected. Some abiotic factors (calcium carbonate, organic matter and selection coefficient) had a negative influence on the abundance of the gastropod, while relationship between the O. minuta and other species of the macrofauna were not evident. In a microscale study of tidal ponds (meters) and ripple marks (centimeters), it was observed that, in a centimeter scale, the gastropod was more abundant in places where there was more water in the sediment, whereas in a meter scale the abundance didn\'t vary in or out of the ponds. In a temporal scale, monthly fluctuations of the O. minuta population\'s density were observed, with reduction/absence of individuals between February and March, which suggests that migration and mortality occurred. This study showed that the distribution of O. minuta is influenced by different factors which act in different scales.

A fim de avaliar a influência do sistema estuarino de Santos sobre os Nematoda da plataforma continental adjacente, a densidade, composição genérica e diversidade desse grupo foram analisadas e relacionadas com o tipo de sedimento, teor de matéria orgânica e biomassa de fitopigmentos. Para isso, o sedimento foi coletado em seis estações, no inverno/2005 e verão/2006, com um amostrador do tipo box-corer, do qual foram retiradas amostras para a meiofauna com um tubo de 4,9 cm2 de área superficial e 10 cm de altura. Os Nematoda representaram mais de 95% da meiofauna, com densidades médias de 2472±1794 ind.10cm-2 no inverno/2005 e de 2606±2017 ind.10cm-2 no verão/2006. A influência do sistema estuarino de Santos restringiu-se às áreas na saída da baía de Santos e do canal de Bertioga e deu-se através do aporte de sedimentos finos e de matéria orgânica, que foi mais evidente no verão devido à maior pluviosidade. Nessas áreas foram observadas menores densidades e maior abundância de gêneros depositívoros, como Sabatieria e Terschellingia e da família Xyalidae. Nas outras estações rasas com sedimento arenoso, bem selecionado e com biomassa de clorofila-a relativamente alta, as densidades foram as mais altas e predominaram Chromadorita e Microlaimus, herbívoros/comedores de epistrato. Nas estações mais profundas, com sedimento mais finos, a densidade e diversidade foram menores e Sabatieria foi dominante. Portanto, além do sistema estuarino, a profundidade e o hidrodinamismo local, que determinam as condições sedimentares e tróficas, foram fatores importantes para as associações dos Nematoda. To assess the influence of Santos estuarine system on the nematodes of the adjacent continental shelf, the density, composition and generic diversity of this group were analyzed and related to the sediment type, organic matter content and phytopigments biomass. The sediment was collected at six stations, in the winter of 2005 and summer of 2006, with a box-corer from which meiofauna samples were taken with a 4.9 cm2 superficial area and 10 cm height corer. Nematodes represented more than 95% of the total meiofauna, and their average densities were 2,472±1,794 ind.10cm-2 in the winter/2005 and 2,606±2,017 ind.10cm-2 in the summer/2006. The influence of Santos estuarine system was restricted to the closest areas to Santos bay and Bertioga channel and it was observed through the contribution of fine sediments and organic matter, which was more evident in the summer due to higher rainfall. In these areas, lower nematodes densities were found as higher abundance of deposit feeders genera, like Sabatieria and Terschellingia, and from the Xyalidae family. In the other shallow stations with well sorted sands and relatively high chlorophyll-a biomasses, densities were the highest and Chromadorita and Microlaimus, herbivorous/epistrate feeders, were predominant. In the deepest stations with finer sediments, the densities and diversities were the lowest and Sabatieria was dominant. Therefore, apart from the estuarine system, the depth and local hydrodynamics, which determines the sediment and trophic conditions, were important factors for the nematodes assemblages.