Evaluación de la vulnerabilidad ecológica de los gasterópodos bentónicos marinos del Atlántico Occidental

Assessing the extinction risk in marine invertebrates poses serious challenges to conservation biology, due to the magnitude of marine biodiversity, the inaccessibility of most of the marine realm, and the lack of appropriate data on population dynamics and ecology for most species. However, simple life history traits have a huge potential for preliminary screening criteria for assessing large numbers of species whose status is harsh or impossible to evaluate. Body size and trophic position could be strong predictors of extinction risk providing a general framework for the assessment of species vulnerability. We analyzed the Body Size-Trophic Position (BS-TP) relationship along 1,067 genera representing 4,256 nominal species of western Atlantic benthic gastropods. We found that a carnivore diet characterizes 67% of the genera and that, supporting theoretical predictions, the probability of being carnivores as a function of size showed a unimodal trend. For species with adult body sizes larger than 5 cm, a negative association between trophic position and body size was detected. This result points to an energetic restriction for the viability of large species, implying that organisms placed near the BS-TP boundary are extremely vulnerable to environmental changes. With this result, 109 genera from 42 families of carnivore gastropods and 33 genera from 19 families of herbivore gastropods that may be more vulnerable from the analyzed perspective were identified and ranked. Supporting these results, while the most vulnerable genera are not represented in global IUCN assessments, all our ‘top 10’ vulnerable families are being considered in National or Regional Red Lists. Prior to conducting regional or global conservation assessments for invertebrate taxa, screening methods should be strongly considered.Evaluar el riesgo de extinción de los invertebrados marinos plantea serios desafíos para la biología de la conservación, debido a la magnitud de la biodiversidad marina, la inaccesibilidad de la mayor parte del ámbito marino y la falta de datos apropiados sobre la dinámica de población y la ecología de la mayoría de las especies. Sin embargo, los rasgos simples de la historia de vida tienen un gran potencial como criterios preliminares de selección para evaluar un gran número de especies cuyo estado es difícil o imposible de evaluar. El tamaño del cuerpo y la posición trófica podrían ser fuertes predictores del riesgo de extinción proporcionando un marco general para la evaluación de la vulnerabilidad de las especies. Analizamos la relación Tamaño Corporal-Posición Trófica (BS-TP) a lo largo de 1.067 géneros que representan 4.256 especies nominales de gasterópodos bentónicos del Atlántico Occidental. Encontramos que una dieta carnívora caracteriza al 67% de los géneros y que, apoyando las predicciones teóricas, la probabilidad de ser carnívoros en función del tamaño mostró una tendencia unimodal. Para especies con tamaños corporales adultos mayores de 5 cm, se detectó una asociación negativa entre la posición trófica y el tamaño corporal. Este resultado apunta a una restricción energética para la viabilidad de las especies grandes, lo que implica que los organismos ubicados cerca del límite BS-TP son extremadamente vulnerables a los cambios ambientales. Con este resultado, se identificaron y clasificaron 109 géneros de 42 familias de gasterópodos carnívoros y 33 géneros de 19 familias de gasterópodos herbívoros que pueden ser más vulnerables desde la perspectiva analizada. Respaldando estos resultados, mientras que los géneros más vulnerables no están representados en las evaluaciones globales de la UICN, todas nuestras “10 principales” familias vulnerables están siendo consideradas en las Listas Rojas Nacionales o Regionales. Antes de realizar evaluaciones de conservación regionales o globales para taxones de invertebrados, se deben considerar seriamente los métodos de detección

Impactos de la pesca artesanal de la almeja Arca zebra sobre la población del neogastrópodo Voluta musica en el oriente de Venezuela

An important ark clam (Arca zebra) artisanal fishery takes place in the east region of Venezuela. Besides the target species, trawling extracts a significant bycatch of several mollusk species including the gastropod Voluta musica, a threatened species according to the Ven ezuelan Red List of Endangered Species. In this paper we evaluate: 1) the composition of mollusk species in the bycatch, 2) the number of individuals of V. musica caught as bycatch and, 3) the abundance and size structure of the exploited populati on. Each fishing night, about 27,830 m2 are trawled by each boat extracting on the average 607 kg of A. zebra meat and 19 kg of V. musica (whole shelled animal). This fishery activity potentially captures ~30,000 kg of ark clam meat and 922 kg of V. musica in one week (~95 snails/fishing night/boat). The size structure of the V. musica population at the ark clam bed is significantly smaller than in other nearby sites not impacted by trawling fishing activities. Non-targeted species extracted in the bycatch but consumed by the local inhabitants include the gastropods Chicoreus brevifrons, Phyllonotus margaritensis, P. pomum, Fasciolaria tulipa, Strombus pugilis, a few Trochidae species, and the bivalves Pinctada imbricata, Spondylus americanus, Anadara florid ana, A . notabilis, and Trachicardium muricatum. Individuals of V. musica along with several invertebrates are discarded. We recommend that V. musica should not be neglected as a conservation target, and despite that A. zebra fisheries are considered “artisanal”, that more strict regulations should be established on it.La pesca artesanal de la almeja arca (Arca zebra) es una de las pesquerías de mayor importancia en el oriente de Venezuela. En esta pesquería se capturan incidentalmente varias especies de moluscos, incluyendo el gasterópodo Voluta musica, considerada amenazada según el Libro Rojo de la Fauna Venezolana. En este trabajo se evalúa: 1) la composición de especies de moluscos en la captura incidental, 2) el número de individuos de V. musica capturados como pesca incidental y 3) la estructura de tallas y abundancia de la población explotada. En cada faena de pesca se arrastran 27.830 m 2 por cada barco, extrayendo en promedio 607 kg de A. zebra (sin concha) y 19 kg de V. musica (con concha). La flota completa captura ~30.000 kg de A. zebra y 922 kg de V. musica en una semana (~95 caracoles/noche de pesca/barco). La estructura de tallas de la población de V. musica en el banco de A. zebra es significativamente menor comparada con sitios cercanos no afectados por la pesca de arrastre. Otras especies capturadas incidentalmente son consumidas por los habitantes loca les e incluyen los gasterópodos Chicoreus brevifrons, Phyllonotus margaritensis, P. pomum, Fasciolaria tulipa, Strombus pugilis, y unas pocas especies de Trochidae, bivalvos Pinctada imbricata, Spondylus americanus, Anadara floridana, A . notabilis, Trachicardium muricatum. Los individuos de V. musica y otros invertebrados son desechados completamente. V. musica debe ser considerada como objeto de conservación, y a pesar que la captura de A. zebra es considerada "artesanal", se deberían establecer regulaciones más estrictas sobre esta especie.Fil: Peralta, Ana Carolina. Universidad Simón Bolívar; VenezuelaFil: Miloslavich, Patricia. Universidad Simón Bolívar; VenezuelaFil: Carranza, Alvar. Universidad de la República; UruguayFil: Bigatti, Gregorio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentin

¿El modo de desarrollo afecta los patrones de distribución de los gasterópodos megabentónicos de la plataforma continental uruguaya?

We analyzed the effect of development mode (direct vs. pelagic development) on the spatial structure of a megabenthic gastropod assemblage at a regional scale. The research was carried out along the bathymetric, saline and thermal gradients generated by the interaction between the shelf topography, the freshwater discharge of Río de la Plata and the presence of oceanic water masses. Direct developers dominated in terms of number of species in the entire area and when the inner and outer shelves were considered separately. Species with pelagic development were not observed to be ecologically successful (i.e. have higher abundances) on the inner shelf, which suggests that high environmental variability may not necessarily favour this strategy. No patterns were found in the relative abundance of species in each developmental mode between the inner (i.e. < 50 m) and outer shelves. However, richness patterns of the two groups were differentially affected by environmental conditions. Species richness for direct developers was affected by mean annual temperature, bathymetry and longitude while pelagic developers showed evident trends in relation to temperature range and latitude. Further studies are necessary to derive general predictions concerning the relative advantages of each developmental type in relation to these gradients in ecological time scales and local or regional spatial scales.Se analizó el efecto del modo de desarrollo (directo vs. pelágico) en la estructura espacial de una asociación de gasterópodos megabentónicos a una escala regional. Esto se hizo a lo largo de los gradientes batimétricos, salinos y de temperatura generados por la interacción entre la topografía de la plataforma, la descarga del Río de la Plata y la presencia de masas de agua oceánicas. La riqueza de especies con desarrollo directo fue mayor, tanto a lo largo de toda el área como al considerar separadamente la plataforma interna y externa. El éxito ecológico (i.e. mayores abundancias) de especies con desarrollo pelágico en la plataforma interna no fue verificado, sugiriendo que una alta variabilidad ambiental no necesariamente puede favorecer a esta estrategia. No se encontraron patrones en la abundancia relativa entre las especies con diferentes modos de desarrollo entre la plataforma interna (i.e. < 50 m) y externa. Sin embargo, los patrones de riqueza de especies de ambos grupos fueron afectados en forma diferencial por las condiciones ambientales. La riqueza de especies con desarrollo directo fue afectada por la temperatura anual promedio, la batimetría y la longitud, mientras que la riqueza de especies con desarrollo pelágico exhibió patrones evidentes en relación con el rango de temperatura y la latitud. Se insiste en la necesidad de futuros estudios para derivar predicciones generales en relación con las ventajas relativas de cada modo de desarrollo en relación con gradientes ambientales, en escalas de tiempo ecológicas y escalas espaciales locales o regionales

Comunidades macrobentónicas del intermareal rocoso a lo largo de un gradiente estuarino de gran escala

We evaluated relationships between (1) salinity and species richness and (2) frontal zones and community structure for the rocky intertidal macrobenthic community of the Uruguayan coast. A large-scale sampling design (extent ~500 km) covering 9 rocky shores across 3 intertidal levels was performed between September and November 2002. The linear relationship between salinity and species richness (minimum at the freshwater extreme) and the lack of correlation between variation in salinity and richness rejected two previous empirical models, explaining variations in species richness along the salinity gradient. Other factors (e.g. turbidity) may explain this discrepancy. The estuarine front defined two communities—freshwater and estuarine-marine—differing in species composition and richness. The freshwater community was characterised by low richness and few individuals confined to crevices or tide pools, and must be structured by physical processes (e.g. desiccation); the estuarine-marine community, with individuals occupying almost all available substrata, must be structured by both physical and biological processes. A marine front, separating estuarine and marine habitats, had a weak effect on community structure although estuarine and marine assemblages differed according to species characterising different functional groups. We conclude that the position of the estuarine frontal zones is important for explaining large-scale patterns of community structure in the study area.En este trabajo evaluamos las relaciones entre (1) la salinidad y la riqueza específica, y (2) las zonas frontales y la estructura de la comunidad macrobentónica del intermareal rocoso de la costa uruguaya. Un diseño de muestreo de gran escala, aplicado entre septiembre y noviembre de 2002, cubrió 9 puntas rocosas y 3 niveles intermareales. La relación lineal entre la riqueza específica y la salinidad (mínima riqueza hacia el extremo dulceacuícola del gradiente) y la ausencia de relación entre la riqueza y las variaciones temporales en la salinidad descartaron dos modelos previos que intentaban explicar las variaciones de riqueza a lo largo del gradiente salino. Otros factores (e.g. turbidez) podrían explicar estas discrepancias. El frente salino definió dos comunidades, de agua dulce y estuarina-marina, diferenciadas en su composición y riqueza específica. La comunidad dulceacuícola se caracterizó por pocos individuos, confinados a grietas o piletas de marea y estaría estructurada por procesos físicos (e.g. desecación). La comunidad estuarina-marina, compuesta por un mayor número de especies, ocupando casi la totalidad del sustrato disponible, estaría estructurada por procesos físicos e interacciones biológicas. El frente marino, que separa los hábitats marinos y estuarinos, tuvo un efecto reducido sobre la estructura de la comunidad, aunque se pudieron diferenciar agrupaciones marinas y estuarinas a partir de especies de diferentes grupos funcionales. A partir de estos resultados, concluimos que la posición del frente estuarino es importante para explicar los patrones de gran escala en la comunidad estudiada

Sedimentary processes in the head of the Cabo Polonio mega slide canyon (southwestern Atlantic margin off Uruguay)

The Southwestern Atlantic margin is characterized by several canyon systems incised on a huge contourite depositional system associated with the interaction of strong Antarctic water masses with the seafloor. So far, however, only one mega slide canyon (Cabo Polonio) has been described in the Uruguayan continental slope. In this work, sedimentary processes dominating the head of this mega slide canyon are described and interpreted based on the analysis of the composition (texture and fossils) and distribution of widespread gravel along its head and thalweg. This information is integrated with acoustic (multibeam and seismic) and hydrological data. Results suggest that the evolution of the head of the canyon presents retrogressive erosion related to debris and turbidity flows. This erosion is ongoing and/or has been active during the recent past and contourite deposits are involved in headwall erosion. The pathway of gravel along the canyon and the thalweg was reconstructed. The strong flow of the South Atlantic Central Water, and its interaction with the Antarctic Intermediate Water, dominates the modern hydrology, promoting highly energetic conditions enhancing headwall erosion. This work contributes to a better understanding of the sedimentary processes connected to an mega slide canyon in the upper slope off Uruguay and located in the northernmost distribution of the South Atlantic Contourite Depositional System

Physical drivers and dominant oceanographic processes on the uruguayan margin (Southwestern Atlantic): a review and a conceptual model

The Uruguayan continental margin (UCM), located in the Southwestern Atlantic margin’s subtropical region, is positioned in a critical transitional region regarding the global ocean circulation (Río de la Plata (RdlP) outflow and Brazil-Malvinas Confluence), as also reflected in seafloor features (northernmost distribution of a large depositional contourite system and RdlP paleovalley). This complex oceanographic scenario occurring in a relatively small area highlights the advantage of considering the UCM as a natural laboratory for oceanographic research. The present work provides the first conceptual “control” model of the physical drivers (i.e., climate, geomorphology) and main oceanographic processes (i.e., hydrodynamics, sediment, and carbon dynamics) occurring along the UCM, reviewing and synthesizing available relevant information based on a functional integrated approach. Despite the conspicuous knowledge gaps on critical processes, a general picture of the system’s functioning is emerging for this complex biophysical setting. This includes conceptualizations of the actual controls, main processes, feedbacks, and interactions responsible for system dynamics. The structure adopted for developing our conceptual models allows permanent improvement by empirical testing of the working hypothesis and incorporating new information as scientific knowledge advances. These models can be used as a baseline for developing quantitative models and, as representations of relatively “pristine” conditions, for stressors models by identifying sources of stress and ecological responses of key system attributes under a transboundary approach.CSIC: I + D 201

The benefits of bivalve reef restoration: a global synthesis of underrepresented species

This is the final version. Available on open access from Wiley via the DOI in this recordBivalve habitat restoration is growing in geographic extent and scale globally. While addressing the wide‐scale loss of these biogenic habitats is still a key motivation behind restoration efforts, stakeholders and funders are increasingly drawn to shellfish restoration for the many ecosystem services these habitats provide. There is clear evidence for the provision of ecosystem services from species targeted for restoration in the USA, in particular Crassostrea virginica. Ecosystem services, however, remain largely unquantified or even undescribed for the majority of other species targeted for restoration. A structured review of the literature was undertaken and supplemented by expert knowledge to identify which ecosystem services are documented in the following other bivalve species targeted for restoration: Ostrea edulis, Ostrea angasi, Crassostrea rhizophorae, Perna canaliculus, Modiolus modiolus, Mytilus edulis, Mytilus platensis, Crassostrea gigas, Ostrea denselamellosa, Crassostrea ariakensis, and Crassostrea sikamea. Key knowledge gaps in quantifying ecosystem services and the ecosystem engineering properties of habitat‐building bivalves contributing to the provision of ecosystem services were identified. Ecosystem services with the potential to be widely applicable across bivalve habitat‐building species were identified. Though there is evidence that many of the ecosystem engineering properties that underpin the provision of ecosystem services are universal, the degree to which services are provided will vary between locations and species. Species‐specific, in situ, studies are needed in order to avoid the inappropriate transfer of the ecosystem service delivery between locations, and to further build support and understanding for these emerging targets of restoration.Glenmorangie DEEP projectHWU EGISEuropean Unionerman Federal Agency for Nature ConservationEuropean Union Horizon 202

Description and life cycle of a new species of the genus Arachnanthus (Cnidaria: Anthozoa: Ceriantharia) from the Southwestern Atlantic Ocean

Background Ceriantharia is a subclass of the phylum Cnidaria, which comprises tube-dwelling marine invertebrates. This subclass is composed of three families, including Arachnactidae, with two known genera. Currently, the genus Arachnanthus has five valid species recorded from Australia, the Mediterranean Sea and both the Southern and Northern Pacific Ocean. However, at the moment, there is no record of organisms of this family from the South Atlantic Ocean. Besides that, the life cycle of any species of the genus Arachnanthus is known. The present study describes a new species of the genus Arachnanthus and its life cycle, based on specimens from Uruguay and South of Brazil. Methods Larvae were collected by plankton net in Rio Grande—Brazil and the development and external morphology of these specimens were observed in the laboratory during two years, and subsequently described. Additionally, nine adult ceriantharians correspondent to the larvae from Rio Grande were collected in Uruguay and their external and internal anatomies, and cnidome were described. Results Arachnanthus errans sp. nov. exhibited a free-swimming, short-lived cerinula larvae that spent short-time on the plankton. The larva developed into small and translucent polyps with a short actinopharynx, one pair of mesenteries attached to a siphonoglyph, and a medium first pair of metamesenteries. Further, the adult polyp displayed an unprecedented locomotion behavior in Ceriantharia that is first reported here, it can crawl under and in between the sediment

Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management

Native oyster reefs once dominated many estuaries, ecologically and economically. Centuries of resource extraction exacerbated by coastal degradation have pushed oyster reefs to the brink of functional extinction worldwide. We examined the condition of oyster reefs across 144 bays and 44 ecoregions; our comparisons of past with present abundances indicate that more than 90% of them have been lost in bays (70%) and ecoregions (63%). In many bays, more than 99% of oyster reefs have been lost and are functionally extinct. Overall, we estimate that 85% of oyster reefs have been lost globally. Most of the world\u27s remaining wild capture of native oysters (\u3e 75%) comes from just five ecoregions in North America, yet the condition of reefs in these ecoregions is poor at best, except in the Gulf of Mexico. We identify many cost-effective solutions for conservation, restoration, and the management of fisheries and nonnative species that could reverse these oyster losses and restore reef ecosystem services