Intraspecific variation in reproductive traits and embryo elemental composition of the crab Hemigrapsus crenulatus (Milne Edwards, 1837) across fluctuating coastal environments along Chilean coasts.

The estuarine crab Hemigrapsus crenulatus has a wide distribution range along the coast of the South Pacific Ocean (from 20 °S to 53 S°). This decapod is abundant in these coastal and estuarine habitats and plays a key ecological role as prey of the snook fish (Eleginops maclovinus) and kelp gull (Larus dominicanus). Its diet consists of detritus, dead fish, and crustaceans, and the macroalgae Ulva sp. In response to contrasting environmental conditions and anthropogenic impacts along the Chilean coast, H. crenulatus may present intraspecific variations in its reproductive traits and changes in the elemental composition of its embryos, directly affecting its biological fitness. Along the Chilean coast, female individuals were collected during late spring 2019 and early summer 2020 (from November 2019 to February 2020) in six areas of Chile (north: Tongoy (30°S); south-central: Lenga (36°S), Tubul (37°S); south austral: Calbuco (41°S), Castro (42°S), Quellón (43°S). The environmental conditions (i.e. sea surface temperature, precipitation and chlorophyll α) present during each sampling event were also recorded. We evaluated the reproductive parameters of females (fecundity, reproductive output (RO)) as well as their body size (carapace width and dry weight), volume, water content, dry weight, elemental composition (carbon, hydrogen, nitrogen: CHN), and finally the energy content of their embryos. Our results indicated that the environmental conditions of the sea water temperature, precipitation (proxy of water salinity) and chlorophyll α (proxy of food availability) have direct effects on the reproductive parameters of females and the characteristics of their embryos. We observed a low fecundity and high RO in Calbuco and Quellón, where precipitation was high (i.e. diluted salinity) and temperatures and productivity was low. For embryo traits, the highest values of volume and water content were observed in female crabs from the estuarine areas (i.e. Tongoy, Lenga, Tubul), values much higher than those found in the internal sea of Chile (i.e. Calbuco, Castro, Quellón). For the elemental composition, we observed high nitrogen levels and a low C:N proportion in embryos from female crabs from Lenga (a nitrogen enriched area). Fluctuating environmental variables among localities proved to modulate intraspecific variations in females and embryos of H. crenulatus, revealing different reproductive strategies, particularly in the quality and energy investment per embryo, which subsequently influenced successful embryogenesis and larval survival.

Mollusk death assemblages in 210Pb-dated marine sediment cores reveal recent biotic changes in the Gulf of Guanahacabibes, NW Cuba.

We investigated stratigraphic changes in mollusk death assemblages and geochemistry in sediment cores from four seagrass beds and one unvegetated site in the Gulf of Guanahacabibes (GG), NW Cuba. There was a transition from mangrove to seagrass beds, associated with sea level rise ∼6000 years ago. Sediment accumulation rates during the last century showed a general rise, but increased sharply after ∼1980, likely because of human activities. The GG displayed overall high mollusk γ-diversity, and our estimate of 189 species is biased toward the low end. High ß-diversity was driven by inter-site differences in grain size, vegetation cover, and nutrient input. Spatial heterogeneity within the basin influenced downcore abundance and diversity metrics, highlighting the influence of local drivers. Herbivorous gastropods dominated in seagrass beds and suspension feeder bivalves were dominant on sandy bottom. In the top parts of cores, species richness declined at two sites that were subject to high, human-mediated bulk sedimentation rates and eutrophication. Conservation measures are needed to preserve this hotspot of marine diversity.

Taxonomic and functional diversity of mollusk assemblages in a tropical rocky intertidal zone / Diversidade taxonômica e funcional das assembleias de moluscos em uma zona entre marés rochosa tropical

We investigated the spatial variation of molluscan assemblages with different habitat-forming species and bare rock habitat in a rocky intertidal zone in northeastern Brazil. The high intertidal zone substrate was covered predominantly of barnacles [Chthamalus bisinuatus (Pilsbry, 1916)], the mid-intertidal of mussels [Brachidontes exustus (Linnaeus, 1758)] and the low intertidal of macroalgae chlorophytes [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], phaeophytes [Sargassum vulgare C. Agardh] and rhodophytes [Palisada flagellifera (J.Agardh) K. W. Nam, 2007]. A total of 3,861 mollusks were recorded, belonging to the classes Gastropoda (9 species; 3,800 individuals), Bivalvia (3 spp.; 54 ind.), and Polyplacophora (1 sp.; 7 ind.). Functional diversity was accessed through the trophic structure, in which we identified food guilds: suspension feeders, grazers, herbivores, and carnivores. The analysis revealed significant differences in mollusk abundance, species richness, diversity indices, and trophic diversity among barnacle belts, mussel beds, algae habitat, and bare rock habitats. The highest species richness and trophic diversity were detected in algae habitat and mussel beds, which showed low abundance. In contrast, barnacle belts registered low species richness and trophic diversity and a high number of individuals. Bare rock recorded low values in all surveyed indices. This result points to the effect of environmental modification caused by habitat-forming species in this system. These species increase environmental complexity and enable the establishment of organisms through facilitation processes. The various food guilds found in this study reaffirm the role of habitat-forming species in providing niches that support different occupation patterns.

Nós investigamos a variação espacial das assembleias de moluscos em função de diferentes habitats formados por fauna séssil e substrato rochoso em uma zona entre marés rochosa no nordeste do Brasil. O substrato da zona entre marés superior era predominantemente recoberto por cracas [Chthamalus bisinuatus (Pilsbry, 1916)], da zona entre marés média por mexilhões [Brachidontes exustus (Linnaeus, 1758)] e da zona entre marés inferior por macroalgas clorofíceas [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], feofíceas [Sargassum vulgare C. Agardh, 1820] e rodofíceas [Palisada flagellifera (J. Agardh) K. W. Nam, 2007]. Foram registrados 3861 moluscos pertecentes às classes Gastropoda (9 espécies; 3800 indivíduos), Bivalvia (3 spp.; 54 ind.), e Polyplacophora (1 sp.; 7 ind.). A diversidade funcional foi analisada através da estrutura trófica, na qual identificamos as guildas alimentares: suspensívoros, raspadores, herbívoros e carnívoros. Abundância, riqueza de espécies, diversidade de Shannon, uniformidade de Pielou e diversidade trófica variaram em função dos habitats formados por cracas, mexilhões, algas e substrato rochoso. Habitats formados por algas e mexilhões apresentaram elevada riqueza de espécies e diversidade trófica, entretanto, apresentaram baixa abundância. Ao contrário, o habitat formado por cracas registrou baixa riqueza e diversidade trófica e elevado número de indivíduos. O substrato rochoso apresentou valores baixos em todos os índices investigados. Esse resultado mostra o efeito da modificação ambiental provocada pela fauna séssil nesse sistema. Esses organismos aumentam a complexidade ambiental e viabilizam o estabelecimento de organismos por meio de processos de facilitação. As diferentes guildas alimentares encontradas neste estudo reafirmam o papel dos substratos biológicos no fornecimento de nichos capazes de suportar diferentes padrões de ocupação.

Taxonomic and functional diversity of mollusk assemblages in a tropical rocky intertidal zone

ABSTRACT We investigated the spatial variation of molluscan assemblages with different habitat-forming species and bare rock habitat in a rocky intertidal zone in northeastern Brazil. The high intertidal zone substrate was covered predominantly of barnacles [Chthamalus bisinuatus (Pilsbry, 1916)], the mid-intertidal of mussels [Brachidontes exustus (Linnaeus, 1758)] and the low intertidal of macroalgae chlorophytes [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], phaeophytes [Sargassum vulgare C. Agardh] and rhodophytes [Palisada flagellifera (J.Agardh) K. W. Nam, 2007]. A total of 3,861 mollusks were recorded, belonging to the classes Gastropoda (9 species; 3,800 individuals), Bivalvia (3 spp.; 54 ind.), and Polyplacophora (1 sp.; 7 ind.). Functional diversity was accessed through the trophic structure, in which we identified food guilds: suspension feeders, grazers, herbivores, and carnivores. The analysis revealed significant differences in mollusk abundance, species richness, diversity indices, and trophic diversity among barnacle belts, mussel beds, algae habitat, and bare rock habitats. The highest species richness and trophic diversity were detected in algae habitat and mussel beds, which showed low abundance. In contrast, barnacle belts registered low species richness and trophic diversity and a high number of individuals. Bare rock recorded low values in all surveyed indices. This result points to the effect of environmental modification caused by habitat-forming species in this system. These species increase environmental complexity and enable the establishment of organisms through facilitation processes. The various food guilds found in this study reaffirm the role of habitat-forming species in providing niches that support different occupation patterns.

RESUMO Nós investigamos a variação espacial das assembleias de moluscos em função de diferentes habitats formados por fauna séssil e substrato rochoso em uma zona entre marés rochosa no nordeste do Brasil. O substrato da zona entre marés superior era predominantemente recoberto por cracas [Chthamalus bisinuatus (Pilsbry, 1916)], da zona entre marés média por mexilhões [Brachidontes exustus (Linnaeus, 1758)] e da zona entre marés inferior por macroalgas clorofíceas [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], feofíceas [Sargassum vulgare C. Agardh, 1820] e rodofíceas [Palisada flagellifera (J. Agardh) K. W. Nam, 2007]. Foram registrados 3861 moluscos pertecentes às classes Gastropoda (9 espécies; 3800 indivíduos), Bivalvia (3 spp.; 54 ind.), e Polyplacophora (1 sp.; 7 ind.). A diversidade funcional foi analisada através da estrutura trófica, na qual identificamos as guildas alimentares: suspensívoros, raspadores, herbívoros e carnívoros. Abundância, riqueza de espécies, diversidade de Shannon, uniformidade de Pielou e diversidade trófica variaram em função dos habitats formados por cracas, mexilhões, algas e substrato rochoso. Habitats formados por algas e mexilhões apresentaram elevada riqueza de espécies e diversidade trófica, entretanto, apresentaram baixa abundância. Ao contrário, o habitat formado por cracas registrou baixa riqueza e diversidade trófica e elevado número de indivíduos. O substrato rochoso apresentou valores baixos em todos os índices investigados. Esse resultado mostra o efeito da modificação ambiental provocada pela fauna séssil nesse sistema. Esses organismos aumentam a complexidade ambiental e viabilizam o estabelecimento de organismos por meio de processos de facilitação. As diferentes guildas alimentares encontradas neste estudo reafirmam o papel dos substratos biológicos no fornecimento de nichos capazes de suportar diferentes padrões de ocupação.

Taxonomic and functional diversity of mollusk assemblages in a tropical rocky intertidal zone / Diversidade taxonômica e funcional das assembleias de moluscos em uma zona entre marés rochosa tropical

We investigated the spatial variation of molluscan assemblages with different habitat-forming species and bare rock habitat in a rocky intertidal zone in northeastern Brazil. The high intertidal zone substrate was covered predominantly of barnacles [Chthamalus bisinuatus (Pilsbry, 1916)], the mid-intertidal of mussels [Brachidontes exustus (Linnaeus, 1758)] and the low intertidal of macroalgae chlorophytes [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], phaeophytes [Sargassum vulgare C. Agardh] and rhodophytes [Palisada flagellifera (J.Agardh) K. W. Nam, 2007]. A total of 3,861 mollusks were recorded, belonging to the classes Gastropoda (9 species; 3,800 individuals), Bivalvia (3 spp.; 54 ind.), and Polyplacophora (1 sp.; 7 ind.). Functional diversity was accessed through the trophic structure, in which we identified food guilds: suspension feeders, grazers, herbivores, and carnivores. The analysis revealed significant differences in mollusk abundance, species richness, diversity indices, and trophic diversity among barnacle belts, mussel beds, algae habitat, and bare rock habitats. The highest species richness and trophic diversity were detected in algae habitat and mussel beds, which showed low abundance. In contrast, barnacle belts registered low species richness and trophic diversity and a high number of individuals. Bare rock recorded low values in all surveyed indices. This result points to the effect of environmental modification caused by habitat-forming species in this system. These species increase environmental complexity and enable the establishment of organisms through facilitation processes. The various food guilds found in this study reaffirm the role of habitat-forming species in providing niches that support different occupation patterns.(AU)

Nós investigamos a variação espacial das assembleias de moluscos em função de diferentes habitats formados por fauna séssil e substrato rochoso em uma zona entre marés rochosa no nordeste do Brasil. O substrato da zona entre marés superior era predominantemente recoberto por cracas [Chthamalus bisinuatus (Pilsbry, 1916)], da zona entre marés média por mexilhões [Brachidontes exustus (Linnaeus, 1758)] e da zona entre marés inferior por macroalgas clorofíceas [Gayralia oxysperma (Kützing) K. L. Vinogradova ex Scagel et al., 1989 and Ulva lactuca Linnaeus, 1753], feofíceas [Sargassum vulgare C. Agardh, 1820] e rodofíceas [Palisada flagellifera (J. Agardh) K. W. Nam, 2007]. Foram registrados 3861 moluscos pertecentes às classes Gastropoda (9 espécies; 3800 indivíduos), Bivalvia (3 spp.; 54 ind.), e Polyplacophora (1 sp.; 7 ind.). A diversidade funcional foi analisada através da estrutura trófica, na qual identificamos as guildas alimentares: suspensívoros, raspadores, herbívoros e carnívoros. Abundância, riqueza de espécies, diversidade de Shannon, uniformidade de Pielou e diversidade trófica variaram em função dos habitats formados por cracas, mexilhões, algas e substrato rochoso. Habitats formados por algas e mexilhões apresentaram elevada riqueza de espécies e diversidade trófica, entretanto, apresentaram baixa abundância. Ao contrário, o habitat formado por cracas registrou baixa riqueza e diversidade trófica e elevado número de indivíduos. O substrato rochoso apresentou valores baixos em todos os índices investigados. Esse resultado mostra o efeito da modificação ambiental provocada pela fauna séssil nesse sistema. Esses organismos aumentam a complexidade ambiental e viabilizam o estabelecimento de organismos por meio de processos de facilitação. As diferentes guildas alimentares encontradas neste estudo reafirmam o papel dos substratos biológicos no fornecimento de nichos capazes de suportar diferentes padrões de ocupação.(AU)

Physiological damages of Sargassum cymosum and Hypnea pseudomusciformis exposed to trace metals from mining tailing.

The damages of Mariana's mining mud in the physiology of the brown algae Sargassum cymosum and its main epiphytic, the red algae Hypnea pseudomusciformis, were evaluated by controlled essays. Seaweeds were exposed to presence or absence of mud, isolated or in biological association, for 5 and 15 days. Measured parameters were growth rates, biochemical descriptors, and the chemical investigation of concentration and metal profile of the mud dissolved in seawater. Results showed that the highest values for metals were Al > Fe > Mn > Zn in both exposure periods. The mud also affected the growth rate with lethality in both isolated and associative treatments with H. pseudomusciformis after 15 days. According to our redundancy analysis (RDA), the profile and concentration of all metallic elements can induce different physiological responses of the organisms. We were able to observe a higher physiological adaptive ability of S. cymosum against the long-term presence of metals by the synthesis of phenolic compounds, while the deviation of metabolic routes in H. pseudomusciformis can be addressed as the main responsible for its lethality. Moreover, the presence of Hypnea in associative treatments reduces Sargassum's detoxification ability. The present results reinforce the importance of biological interaction studies in a context of physiological resilience against mining mud pollution and mutual influences of species over the individual ability to avoid oxidative stress.

Meta-analysis of the effects of organic matter on polychaetes of the east coast of South America.

Polychaetes play a key role in benthic functioning and organic matter recirculation. We performed a meta-analysis to investigate the effects of organic matter on polychaetes, considering its origin, type and measurement along the east coast of South America. We summarize 276 effect sizes, mostly representing the Tropical Southwestern Atlantic and Warm Temperate Southwestern Atlantic provinces. We observed that the effect of organic matter depends on its origin and type. We also reveal that the predominance of tolerant species of Capitellidae, Nereididae and Spionidae explains the great variability in effect sizes and non-significant effects. Organic matter negatively affected assessment of polychaete assemblages, such as aspects of diversity and trophic groups. This result suggests that the impact of organic matter can be more intense for communities than for individual species. We suggest that researchers should investigate more complex ecological scales to understand the overall effect of organic matter on polychaetes.

Marine benthic communities affected by the Doce River (southwestern Atlantic): Baseline before a mining disaster.

Prior to Brazil's worst environmental disaster, caused by a mining dam collapse, we had carried out a study of the marine benthic macrofauna (11-51 m depth) under the influence of the Doce River. Our results showed significant diversity, in which mollusks, polychaetes, and crustaceans had the highest frequency, density, and abundance, represented by 162 families in summer and 173 in winter. Our results suggested that richness, abundance, and diversity increase with distance from the coast. Furthermore, with increasing distance from the coast and river mouth, in addition to increasing depth, there was a differentiation in composition and abundance. Multivariate analyses showed depth, carbonate, and organic matter as important factors that explain variations in composition and diversity across the continental shelf. The results could provide an invaluable baseline for measuring the effects on shallow and mesophotic communities of one of the largest tailings dam failures worldwide.

The use of metabarcoding for meiofauna ecological patterns assessment.

Marine meiofauna comprises up to 22 phyla. Its morphological identification requires time and taxonomists' expertise, and molecular tools can make this task faster. We aim to disentangle meiofaunal diversity patterns at Araçá Bay by applying a model selection approach and estimating the effectiveness of metabarcoding (18S rDNA) and morphological methods for estimating the response of meiofauna diversity in small-scale interactions with environmental variables. A rarefaction curve indicated that ten samples were sufficient for estimating the total number of meiofauna OTUs in a tidal flat. In both approaches, richness was predicted by mean sand percentage, sediment sorting, and bacteria concentration. Nematode genera composition differed significantly between approaches, the result of taxonomic mismatch in the genetic database. The similarity between the model selected for diversity descriptors, the richness of nematode genera and meiofauna composition emphasized the utility of predictive models for metabarcoding estimates to detect small-scale interactions of these organisms.

Benthic macrofaunal structure and secondary production in tropical estuaries on the Eastern Marine Ecoregion of Brazil.

Tropical estuaries are highly productive and support diverse benthic assemblages within mangroves and tidal flats habitats. Determining differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support for management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition were evident, with mangrove forests being dominated by annelids (Oligochaeta and Capitellidae) whereas peracarid crustaceans were also abundant on tidal flats. Macrofaunal biomass, density and secondary production also differed between habitats and among estuaries. Those differences were related both to the composition of benthic assemblages and to random spatial variability, underscoring the importance of hierarchical sampling in estuarine ecological studies. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.

Structuring effects of chemicals from the sea fan Phyllogorgia dilatata on benthic communities.

Despite advances in understanding the ecological functions of secondary metabolites from marine organisms, there has been little focus on the influence of chemically-defended species at the community level. Several compounds have been isolated from the gorgonian octocoral Phyllogorgia dilatata, a conspicuous species that forms dense canopies on rocky reefs of northern Rio de Janeiro State, Brazil. Manipulative experiments were performed to study: (1) the effects of live colonies of P. dilatata (physical presence and chemistry) on recruitment of sympatric benthic organisms; (2) the allelopathic effects of its chemicals on competitors; and (3) chemotactic responses of the non-indigenous brittle star, Ophiothela mirabilis. Early establishment of benthic species was influenced on substrates around live P. dilatata colonies and some effects could be attributed to the gorgonian's secondary metabolites.In addition, the gorgonian chemicals also exerted an allelopathic effect on the sympatric zoanthid Palythoa caribaeorum, and positive chemotaxis upon O. mirabilis. These results indicate multiple ecological roles of a chemically-defended gorgonian on settlement, sympatric competitors, and non-indigenous species.

Sewage input reduces the consumption of Rhizophora mangle propagules by crabs in a subtropical mangrove system.

Mangrove forests are highly productive and play a major role in global carbon cycling. Their carbon accumulation can be influenced through the consumption of nutrient-poor leaves and propagules by herbivore crabs. Anthropogenic nutrient input from sewage contamination is widespread in these often naturally nutrient-limited ecosystems. We hypothesised that sewage-mediated nutrient input to mangrove stands of Paranaguá Bay (southern Brazil), would alter the nutrient sources available for crabs, e.g. through microphytobenthos increase, and that this would reflect in their feeding behaviour. We predicted that propagules of Rhizophora mangle in contaminated stands would experience lower grazing pressure from their two main local consumers (Ucides cordatus and Goniopsis cruentata). We compared herbivory rates on R. mangle propagules in sewage contaminated and uncontaminated mangrove stands. We found that herbivory rates were significantly lower in contaminated than uncontaminated forests, but this pattern could not be clearly attributed to increased nutrient availability.

Ecological Niche Model used to examine the distribution of an invasive, non-indigenous coral.

All organisms have a set of ecological conditions (or niche) which they depend on to survive and establish in a given habitat. The ecological niche of a species limits its geographical distribution. In the particular case of non-indigenous species (NIS), the ecological requirements of the species impose boundaries on the potential distribution of the organism in the new receptor regions. This is a theoretical assumption implicit when Ecological Niche Models (ENMs) are used to assess the potential distribution of NIS. This assumption has been questioned, given that in some cases niche shift may occur during the process of invasion. We used ENMs to investigate whether the model fit with data from the native range of the coral Tubastraea coccinea Lesson, 1829 successfully predicts its invasion in the Atlantic. We also identified which factors best explain the distribution of this NIS. The broad native distributional range of T. coccinea predicted the invaded sites well, especially along the Brazilian coast, the Caribbean Sea and Gulf of Mexico. The occurrence of T. coccinea was positively related to calcite levels and negatively to eutrophy, but was rather unaffected to other variables that often limit other marine organisms, suggesting that this NIS has wide ecological limits, a trait typical of invasive species.

Analysis of large-scale spatio-temporal trends of Ostrea puelchana beds in Northern Patagonian gulfs, Argentina.

Wild oyster populations have declined severely worldwide, however fluctuations of South Atlantic populations are poorly documented. We explored the changes in the abundance of Ostrea puelchana population of Northern Patagonia, Argentina, by linking data from paleontological, archaeological and informal sources, with time series data from fishing, ecological and studies of oyster pathology. The present work is the first study which includes a South Atlantic time series concerning oyster beds. The focal area for this study is the San Matías Gulf (SMG, 40° 50'-42° 15' S, 63° 5'-65° 10' W). Populations of O. puelchana were inferred from sub-fossil deposits (>700 years ago) throughout the gulf, but were documented in surveys a century ago only in the NW coast. The population has declined in the last decades. However, new populations have established recently in the NE and southern regions of the gulf. A Bonamia exitiosa epizootic was coincident with the declining trend of the abundance provided by the time series, suggesting that beds declined as a consequence of parasite infections. Dredging fisheries for scallops took place in the 1970s and 1980s on the NE coast of the gulf, in areas adjacent to the NE oyster beds. We proposed that fishing activities might have had a low impact on oyster beds, since NE beds expanded and increased during that period. The southward expansion of oyster population at latitudes beyond the historical distribution range might reflect long-term adequate environmental conditions for larval survival on the NE and S of the SMG.