Hábitats biogénicos como reguladores de la variabilidad de las comunidades bentónicas de invertebrados en la bahía de Tongoy (costa del Pacífico SE): implicaciones de la cosecha de macroalgas

Habitat biogenic complexity is thought to exert a significant positive influence on benthic communities. We examined the link between the seasonal variability of macroinvertebrate community structure (species and trophic richness, diversity and biomass) and habitats with different macroalgal assemblages. We identified macroinvertebrates and algae from 336 samples spread over four types of habitat: sand, mud, sand-gravel and seagrass meadows. Considering the whole macroalgal and macroinvertebrate assemblage, we confirmed that macroinvertebrate community variability within and among habitats can be mainly (but not only) explained by a few macroalgal structuring species. The variability of macroinvertebrate communities between habitats and seasons depended on the changes in the relative contribution of the explanatory biostructuring species in the overall algal community. Biomass, trophic behaviour and species richness remained stable in habitats with conspicuous macroalgal communities in contrast with habitats devoid of macroalgae. However, invertebrate species richness and biomass remained stable only in habitats whose dominant species did not change between seasons and not in those where dominant structuring species shifted. The seasonal change in a key structuring macroalgal species (Condracanthus chamissoi), probably as a result of harvesting, led to a major reduction in invertebrate community biomass and richness both in the particular habitat and in those nearby at species level. These consequences are especially important for invertebrates linked by trophic relationships and targeted by fisheries.La complejidad biogénica del hábitat ejercería una importante influencia positiva sobre las comunidades bentónicas. Examinamos la relación entre la variabilidad estacional de la estructura de las comunidades de macroinvertebrados (riqueza, diversidad y biomasa de especies y grupos tróficos) en hábitats con diferentes ensambles de macroalgas. Identificamos macroinvertebrados y algas en 336 muestras distribuidas en cuatro tipos de hábitats: arena, lodo, arena-grava y praderas de pastos marinos. En este estudio, considerando todo el conjunto de macroalgas y macroinvertebrados, confirmamos que la variabilidad de la comunidad de macroinvertebrados dentro y entre los hábitats puede ser explicada principalmente (pero no sólo) por unas pocas especies estructurantes de macroalgas. La variabilidad de la comunidad de macroinvertebrados entre hábitats y estaciones dependió de los cambios de la contribución relativa de las especies biostructurales explicativas en la comunidad algal. La biomasa, el comportamiento trófico y la riqueza de especies permanecieron estables en los hábitats con comunidades de macroalgas conspicuas, en contraste con los hábitats desprovistos de macroalgas. Sin embargo, la riqueza de especies de invertebrados y la biomasa sólo se mantuvieron estables en los hábitats cuyas especies dominantes no cambiaron entre estaciones, pero no en aquellos en los que las especies estructurantes dominantes cambiaron. El cambio estacional de una especie de macroalga estructurante clave (Condracanthus chamissoi), probablemente debido a su cosecha, tuvo importantes consecuencias en la reducción de la biomasa y la riqueza de la comunidad de invertebrados, tanto en su hábitat como en los hábitats adyacentes. Estas consecuencias son especialmente relevantes para los invertebrados vinculados por relaciones tróficas y que además son recursos pesqueros

Vertical Distribution of Decapod Larvae in the Entrance of an Equatorward Facing Bay of Central Chile: Implications for Transport

Two short biophysical surveys were carried out in order to assess how the decapod crustacean larvae vertical distribution and circulation patterns in an equatorward facing embayment (Gulf of Arauco, 37° S; 73° W) influenced larval transport into and out of the Gulf. The embayment is located at the upwelling area of south central Chile and features a deep (60 m) and a shallow (25 m) pathway of communication with the adjacent coastal ocean. Profiles of zooplankton, temperature, salinity, dissolved oxygen and current velocity were measured during a 22-h period at the shallow entrance to the gulf. In addition, three zooplankton profiles were carried out at the deep entrance to the gulf on the basis of observed changes in hydrographic structure. At the shallow entrance to the gulf, current velocities showed a clear semidiurnal tidal signal, with stronger ebb than flood at the surface and stronger flood at depth. Decapod larval abundances showed a bimodal distribution through time, with a maximum during night-time ebb, and a smaller, second peak at day-time ebb. Larval transport in and out of the Gulf depended on larval vertical distribution and the timing of higher densities. Export was reduced when larvae deepened during ebbing tides or when larvae remained deeper throughout the day. Export was enhanced when larger numbers of individuals occupied ebbing surface waters. At the deep entrance, two groups of crustacean larvae were found associated with two different water types: a surface high oxygen water and a deeper suboxic equatorial subsurface water. A group of larvae that originates in the shelf area appeared entering the Gulf in the deeper waters of this entrance but was absent from the shallower one. Larval vertical distribution in the two layer circulation at the embayment entrances can enhance or preclude retention within the bay. The motion of these layers was determined remotely by upwelling dynamics and modified by local wind (sea breeze) and tides. Overall, high frequency processes (semidiurnal tides, diurnal fluctuations) superimposed onto others of lower frequency (3-8 d period of wind-driven upwelling), may contribute significantly to variations in the transport of individuals from bays in upwelling areas

Influence of Biological Factors on Connectivity Patterns for Concholepas concholepas (loco) in Chile

In marine benthic ecosystems, larval connectivity is a major process influencing the maintenance and distribution of invertebrate populations. Larval connectivity is a complex process to study as it is determined by several interacting factors. Here we use an individual-based, biophysical model, to disentangle the effects of such factors, namely larval vertical migration, larval growth, larval mortality, adults fecundity, and habitat availability, for the marine gastropod Concholepas concholepas (loco) in Chile. Lower transport success and higher dispersal distances are observed including larval vertical migration in the model. We find an overall decrease in larval transport success to settlement areas from northern to southern Chile. This spatial gradient results from the combination of current direction and intensity, seawater temperature, and available habitat. From our simulated connectivity patterns we then identify subpopulations of loco along the Chilean coast, which could serve as a basis for spatial management of this resource in the future

In search for the sources of plastic marine litter that contaminates the Easter Island Ecoregion

Subtropical gyres are the oceanic regions where plastic litter accumulates over long timescales, exposing surrounding oceanic islands to plastic contamination, with potentially severe consequences on marine life. Islands’ exposure to such contaminants, littered over long distances in marine or terrestrial habitats, is due to the ocean currents that can transport plastic over long ranges. Here, this issue is addressed for the Easter Island ecoregion (EIE). High-resolution ocean circulation models are used with a Lagrangian particle-tracking tool to identify the connectivity patterns of the EIE with industrial fishing areas and coastline regions of the Pacific basin. Connectivity patterns for “virtual” particles either floating (such as buoyant macroplastics) or neutrally-buoyant (smaller microplastics) are investigated. We find that the South American shoreline between 20°S and 40°S, and the fishing zone within international waters off Peru (20°S, 80°W) are associated with the highest probability for debris to reach the EIE, with transit times under 2 years. These regions coincide with the most-densely populated coastal region of Chile and the most-intensely fished region in the South Pacific. The findings offer potential for mitigating plastic contamination reaching the EIE through better upstream waste management. Results also highlight the need for international action plans on this important issue

Floración excepcional de cianobacterias tóxicas en la costa de Uruguay, verano 2019

Cyanobacterial toxic blooms are a worldwide problem. In Rio de la Plata basin, anthropic eutrophication and dam construction have promoted an increase in cyanobacteria blooms, especially those of the Microcystis aeruginosa complex (CMA). Here, we describe the exceptional blooms observed in the summer of 2019 on the coast of Río de la Plata and Atlantic coast of Uruguay. We discuss the main driving mechanisms using biological, meteorological and oceanographic sampling data, satellite images and reanalysis. The blooms covered a wide surface (Carmelo to Rocha; 500 km) and were persistent in time (ca. 4 months). Blooms were generated by CMA organisms having similar genetic structure and were associated to quantifiable and high microcystin concentrations. Given the observed oceanographic conditions and the similarity in organisms traits, we hypothesized that blooms had a common origin, probably associated with zones with high nutrient concentrations and high water residence time in the lower Rio de la Plata basin. Extreme precipitations induced high water flows that transported cyanobacteria blooms downstream. In addition, anomalous wind and temperature conditions facilitated their arrival to the Atlantic coast along Rocha, to environments with particular relevance for biodiversity and conservation (e.g. Rocha coastal lagoon).Las floraciones de cianobacterias tóxicas son un problema mundial. La eutrofización antrópica y la generación de embalses han promovido su desarrollo en la Cuenca del Plata, favoreciendo principalmente al complejo Microcystis aeruginosa (CMA). En este trabajo describimos las floraciones excepcionales de CMA ocurridas en el verano 2019 en la costa del Río de la Plata y Atlántica de Uruguay y discutimos sus mecanismos moduladores en base a datos biológicos, meteorológicos y oceanográficos de muestreos, imágenes satelitales y re-análisis. Las floraciones fueron extensas (Carmelo a Rocha; 500 km) y persistentes (ca.: 4 meses). En todos los casos fueron organismos del CMA con estructura genética similar y su presencia estuvo asociada a niveles cuantificables y elevados de microcistina. En base a las características oceanográficas y la similitud genética entre los organismos, se hipotetiza que las floraciones tienen un origen común, probablemente asociado a tributarios con alta carga de nutrientes y alto tiempo de residencia del agua en la Cuenca baja del Plata. Las precipitaciones extremas generaron caudales récord que transportaron las cianobacterias hasta el Río de la Plata, donde las condiciones de viento y temperatura particulares facilitaron su transporte y arribo a la costa de Rocha, llegando a ambientes de relevancia para la conservación (e.g. Laguna de Rocha)

Oceanografía biológica de Cabo Polonio: apuntes sobre investigaciones recientes

Los resultados presentados en esta publicación se enmarcan dentro del proyecto financiado por ANII, código: ANII_FCE_2017_136372.Oceanografía biológica de Cabo Polonio: apuntes sobre investigaciones recientes ofrece una muy rápida recorrida por los orígenes de la oceanografía como área del conocimiento científico y las actividades que investigadores de la Facultad de Ciencias y del Centro Universitario Regional Este, ambos de la Universidad de la República, desarrollan en la zona marina costera de Cabo Polonio. Cabo Polonio es interesante desde diversos puntos de vista: histórico, arqueológico, sociológico, paisajístico, ecológico. Durante el siglo XX fue epicentro de la explotación de la mayor población de lobos marinos del Atlántico Sur. Rastros de ese pasado se conservan en la infraestructura de la Base que alojaba a los trabajadores: comedor-cocina, galpones y dormitorios, caldera industrial y un gran bote a remo; implementos para la faena: garrotes, cuchillas, estaqueaderos de cueros... Aún es posible encontrar en ciertos boliches o almacenes del Cabo a veteranos de aquellas lides y - con un poco de suerte - aprender sus historias. El valor paisajístico de Cabo Polonio ha impulsado el crecimiento del centro poblado gracias al influjo del turismo estival y de no pocos que llegaron de visita y decidieron quedarse. Esto plantea enormes desafíos para la conservación de un sitio que no dispone de facilidades como agua potable y saneamiento, electricidad, caminería y cuya biodiversidad - uno de sus grandes atractivos - es muy sensible a cambios en el paisaje. La biodiversidad es uno de los elementos que llevó a incluir a Cabo Polonio en el Sistema Nacional de Areas Protegidas. Sin embargo, el conocimiento de la fauna y flora marinas, así como de los procesos bio-físicos que sustentan esa biodiversidad son muy poco conocidos. El trabajo que aquí se presenta busca contribuir a dicho conocimiento e - indirectamente- al buen uso y manejo del sitio

Distribution of Pleuroncodes monodon larvae over the continental shelf of south-central Chile: Field and modeling evidence for partial local retention and transport

International audienceIn situ and modeled spatial distribution of squat lobster (Pleuroncodes monodon) larvae over the continental shelf off south central Chile (35-37°S) was analyzed along with currents and hydrography. We aimed to identify the main larval transport/retention characteristics in the study area, which constitutes the southernmost P. monodon fishing grounds embedded in the Humboldt Current System. We hypothesized that the main contribution to population renewal originates in the two persistent adult aggregations close to the nursery ground that occurs over a continental shelf terrace limited by two submarine canyons. Two extensive bio-physical field campaigns were carried out during the main 2001-2002 upwelling season field data indicated that larvae were released from late austral winter to spring from spots to the north and south of the nursery. Zoea I were found mainly below 50 m depth in southward-flowing waters, whereas older zoea dominated in northward flowing layers above 50 m. Larvae were circumscribed between the coast and the shelf break front and pelagic retention areas were identified over the widest shelf area. Megalopa and juveniles during March, were only found over the nursery area. Individual based simulations coupled to the output of a hydrodynamic model (climatological configuration) for the studied area, showed that the release sites close to the nursery made the largest contribution to recruitment. Sites further north could also contribute to recruitment if hatching occurred later in the upwelling season. The contribution of vertical behavior to larval success was also important, as was the former's interaction with the site and time of larval release. Our results support the relevance of coastal circulation (affected by topography) on the persistence of P. monodon populations off southern Chile, and the modulation of temporal variability. These results might apply to other abundant species in the area

Identifying appropriate spatial scales for marine conservation and management using a larval dispersal model: The case of Concholepas concholepas (loco) in Chile

International audienc

Life on the edge: Incubation behaviour and physiological performance of squat lobsters in oxygen-minimum conditions

Squat lobsters frequently inhabit low-oxygen waters, facing particular physiological challenges. Pleuroncodes monodon inhabits one of the most extreme oxygen minimum zones in the world’s oceans at low temperatures, but avoids high temperature hypoxic waters. The present study aimed to determine whether the maternally dependent reproductive outcome is compromised under realistic oxygen/temperature conditions (normoxia and 0.7 mg l−1 at 11 and 15°C) and to evaluate some potential metabolic bases. Females incubated for a significantly longer time at low as compared to high temperatures, but reproductive success was only compromised under hypoxic conditions. Brood viability and synchrony were affected by temperature and its interaction with oxygen concentration (especially under hypoxic conditions and 15°C). Non-viable larvae were hatched at hypoxia-15°C, and larvae hatched in hypoxia-11°C did not survive until moulting. Under normoxic conditions, ventilation of the brood mass decreased with advancing embryo development, but remained high or increased under hypoxic conditions, especially at high temperatures. After releasing their broods, females from all treatments had developing oocytes in their ovaries, but the proportion of oocytes in secondary vitellogenesis was larger at 15°C. The diameter of oocytes in secondary vitellogenesis was significantly smaller in hypoxia treatments. Oxygen consumption of ovigerous P. monodon was generally higher at 15°C, especially at normoxia, and their critical point was significantly larger at 15°C. Under hypoxic conditions, ovigerous females compensated their energetic requirements using anaerobic pathways (increase of pyruvate kinase:citrate synthase ratio and lactate). This suggests that this and other species living in hypoxic waters might suffer severe challenges in a warming ocean.Fil: de los Ángeles Gallardo, María. Centro de Estudios Avanzados En Zonas Áridas; Chile. Universidad Católica del Norte; ChileFil: Rojas, Isis. Universidad Católica del Norte; ChileFil: Brokordt, Katherina. Centro de Estudios Avanzados En Zonas Áridas; Chile. Universidad Católica del Norte; ChileFil: Lovrich, Gustavo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Nuñez, Valentina. Universidad Católica del Norte; ChileFil: Paschke, Kurt. Universidad Austral de Chile; ChileFil: Thiel, Martin. Universidad Católica del Norte; ChileFil: Yannicelli, Beatriz. Universidad Católica del Norte; Chile. Universidad de la República; Urugua

Number of settled larvae per depth for (a.) model configuration M0 (passive transport; figure is obtained using the results from Garavelli <i>et al</i>. [33]) and (b) model configuration M2 (with growth).

<p>Number of settled larvae per depth for (a.) model configuration M0 (passive transport; figure is obtained using the results from Garavelli <i>et al</i>. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146418#pone.0146418.ref033" target="_blank">33</a>]) and (b) model configuration M2 (with growth).</p