Carlos Molinet

Observations of intratidal variability of flows over a sill/contraction combination in a Chilean fjord

Underway velocity measurements were carried out for the first time in a Chilean fjord using an acoustic Doppler velocimeter with the purpose of elucidating the intratidal variability of flows through a pass, Paso Galvarino. The pass included a sill, where the bottom sloped by roughly 30%, and a coastline contraction of ∼90%. The relatively small dimensions of the pass allowed for rapid sampling of the flow evolution throughout the tidal cycle. The backscattered sound signal from the velocimeter and from an echo sounder were used to describe the vertical excursions of the pycnocline throughout the domain and to identify regions of enhanced vertical mixing within the pass. The spatial variability of the flow in the pass was consistent with uniform two-layer flow. At the narrowest section of the contraction the pycnocline dropped sharply around both maximum flood and maximum ebb, while the flow accelerated downstream relative to the tidal flow. The slope of the pycnocline changed sign from flood to ebb, which was atypical of other fjord observations but could be explained by the transitions from subcritical to supercritical flow. These transitions switched location at either side of the narrowest section of the contraction. Leeward of this section, increased sound backscatter suggested intensified turbulence that extended over a greater area during ebb than during flood because the distance between the point of pycnocline drop and the end of the pass was longer during ebb. Enhanced vertical mixing within the pass was reflected in the tidally averaged fields by a three-layer flow that consisted of near-surface and near-bottom flow converging toward the pass and flow around the pycnocline diverging away from the pass.

Patterns of larval distribution and settlement of Concholepas concholepas (Bruguiere, 1789) (Gastropoda, Muricidae) in fjords and channels of southern Chile

Concholepas concholepas (Mollusca, Gastropoda, Muricidae) se distribuye entre las costas del sur de Peru y extremo sur de Chile. Practicamente todos los estudios sobre este gastropodo han sido realizados en costas expuestas, sin considerar los fiordos y canales del sur de Chile, a pesar de que estos representan aproximadamente el 95 % de la linea costera de este pais. Aunque se ha publicado un importante volumen de literatura sobre C. concholepas, existen escasos antecedentes acerca de su desarrollo larval temprano en condiciones naturales, principalmente debido a que estos estadios han sido escasamente recolectados en la naturaleza. Este estudio es el primer intento por determinar los patrones de abundancia espacial y temporal de larvas de C. concholepas a traves de su desarrollo hasta el asentamiento, en su ambiente natural. Para ello, fueron recolectadas muestras de plancton semanalmente en superficie y 8 m de profundidad en cuatro canales del sur de Chile. Temperatura y salinidad fueron registradas simultaneamente en cada sector. El asentamiento fue cuantificado usando un sustrato artificial en los cuatro sectores. En este estudio se observo que el desarrollo larval de C. concholepas ocurre durante todo el ano en las aguas interiores del sur de Chile, observandose estados tempranos principalmente entre agosto y marzo, estados competentes entre junio y agosto, y asentamiento entre julio y agosto. Asi, C. concholepas parece tener un largo periodo de desarrollo larval cuya duracion fue estimada entre 6 a 12 meses en este estudio. Finalmente se sugiere que la hidrologia local puede afectar el desarrollo larval de C. concholepas en esta region. Nuevas investigaciones oceanograficas y ecologicas son necesarias para responder las interrogantes e hipotesis surgidas de este estudio

Variabilidad espacial y temporal del suministro larval de mitílidos en el Seno de Reloncaví, sur de Chile

El suministro larval en especies bentonicas es un componente importante que contribuye al exito del reclutamiento y por lo tanto su conocimiento permite entender la dinamica de las poblaciones. En el presente trabajo se estudio la variacion temporal y espacial del suministro larval de Mytilus chilensis y Choromytilus chorus en 3 localidades en la costa del Seno de Reloncavi y su relacion con variables ambientales (temperatura, salinidad y componente del viento). La presencia de larvas competentes de M. chilensis y Ch. chorus presento variabilidad temporal y espacial, la que fue explicada por las variables ano, mes y localidad, y adicionalmente para M. chilensis por el componente de viento este-oeste. La magnitud de la disponibilidad de larvas para ambas especies, fue explicada tambien por las variables ano, mes y localidad, sugiriendo esta variable, efectos de escala local. Una mayor abundancia de larvas competentes observada en la costa noreste del Seno de Reloncavi fue asociada a bajos valores de salinidad y temperatura, lo que sugiere la intrusion de agua del estuario del Reloncavi. En esta zona se han identificado extensos bancos de mitilidos que podrian estar actuando como fuente de larvas para el Seno de Reloncavi.

Reproduction of the sea urchin Loxechinus albus across a bathymetric gradient in the Chilean Inland Sea

La distribucion batimetrica reportada para erizos de interes comercial va desde el intermareal hasta cientos de metros, aunque estudios reportados a profundidades mayores que 25 m son escasos. Se espera que erizos que habitan sitios someros tengan acceso a mas alimento y desplegar un mayor desarrollo gonadico que aquellos erizos de habitat mas profundos. Los erizos en habitat profundo pueden jugar un rol importante para mejorar la resiliencia de las poblaciones explotadas ubicadas en habitat someros. El objetivo de este estudio fue verificar la existencia de parches del erizo Loxechinus albus reproductivamente activos en un gradiente batimetrico desde 0 a 100 m de profundidad en dos areas de pesca del mar interior chileno. Para esto se evaluo el indice gonadico (IG) y el desove inducido con KCl en ejemplares adultos de L. albus recolectados entre la superficie y los 100 m de profundidad entre septiembre de 2008 y marzo de 2009. Los erizos fueron relativamente abundantes hasta 15 m de profundidad, escasos hasta 60 m de profundidad y solo un parche de erizos fue encontrado entre 60 y 100 m de profundidad. Se observo una asincronia en el IG y el desove inducido entre estratos y areas de muestreo, lo que sugiere que los erizos ubicados entre 30 y 100 m podrian estar reproductivamente activos y desovar en distintos periodos, aunque se desconoce su potencial aporte en la dinamica poblacional de L. albus. Futuros estudios deberian enfocarse en estudiar el rol de las escasas agregaciones profundas de L. albus sobre la dinamica de la poblacion de este recurso, particularmente en areas donde la presion de pesca es intensa.

Trends of natural accumulation and detoxification of paralytic shellfish poison in two bivalves from the Northwest Patagonian inland sea

The accumulation of marine toxins in aquatic filterers is a recurrent event that imposes serious risks to human health and important economic losses. While d...

Using Drift Video Transects and Maximum Likelihood Geostatistics for Quantifying and Monitoring Exploited Subpopulations of Loxechinus albus at a Mesoscale

Abstract Population monitoring of benthic species has been complicated by difficulties in defining appropriate spatial units for making observations that are relevant to the management of these fisheries. In many cases, this has led to the application of indirect models of stock evaluation using catch and effort information for estimating global quotas, in spite of the fact that experience suggests that limit reference points should be used. The aim of this study was to research the spatial distribution pattern of the Chilean sea urchin Loxechinus albus at sites identified as fishing beds through direct evaluation. Thus, video transect recordings were used and geostatistical methods were applied to determine the presence of significant spatial units. We found significant spatial structures represented by beds of 1–120 ha with 20,000–2,300,000 sea urchins that revealed fragmentation of the exploited L. albus populations within the study area. Smaller beds were observed close to the landing ports, suggesting that, in the extreme north of the study area, the beds were “in transition” toward becoming unoccupied habitats. This fragmentation is influenced by first-order (habitat availability) and second-order (principally fishing and recruitment) effects. The bed structure observed can be classified as mesoscale, where contraction and expansion dynamics operate. This can lead to persistence, extinction, and reemergence over periods that span more than a generation. Observing the expansion—contraction of these beds can, therefore, be extremely informative when interpreting population and large-scale fishery dynamics. Our hypothesis is that the structure of beds observed is associated with local fishery indicators and therefore can be used to monitor and improve management on a regional scale. This would be particularly useful for such complex regions as the Chilean inland sea, although the methodology requires further adjustment.

Estados tempranos de Echinoidea en canal Lagreze, Islas Guaitecas, sur de Chile

The limited publications on the dynamics of Echinoids on the coast of Chile, despite its ecological significance to marine benthic communities, have hindered...

Species diversity and abundance of dinoflagellate resting cysts seven months after a bloom of Alexandrium catenella in two contrasting coastal systems of the Chilean Inland Sea

ABSTRACT In Chile, 90% of the fish farms and major natural shellfish beds are located in the region surrounding the Inland Sea, where over the last few decades harmful phytoplankton blooms have often been observed. The onset and recurrence of bloom events are often related to the resuspension and germination of resting cysts that have accumulated in the sediments. The degree of cyst settling, accumulation and germination is highly variable between areas and depends on physical and environmental factors. To learn how differences in oceanographic exposure, amount of river runoff and bathymetry affect dinoflagellate cyst deposition, we examined the diversity and abundance of dinoflagellate resting cysts from two hydrographically contrasting coastal areas (oceanic Guaitecas Archipelago and estuarine Pitipalena Fjord) of the Chilean Inland Sea in September 2006, seven months after a bloom of Alexandrium catenella, a producer of paralytic shellfish toxin. Cyst species diversity consisted of 18 taxa, including A. catenella and the noxious species Protoceratium reticulatum, both of which have caused blooms in the study area. Our results revealed significant differences between the two study sites in terms of the abundance and diversity of resting cysts, suggesting that in the specific case of A. catenella, only Guaitecas stations have potential for cyst accumulation and successful growth of cells. However, there was no evidence of long-term resting cyst beds of A. catenella at either study site.

Cadmium determination in Chilean blue mussels Mytilus chilensis: Implications for environmental and agronomic interest

Cadmium is present in agricultural soil composition and is assimilated by plants. The mussel industry generates large volumes of calcareous valves as a byproduct of processing in factories. This solid waste is ground, stored and disposed of in the form of agricultural supplies near production areas in almost all regions of the world. Cd content was recorded in these calcareous substrate by-products of industrial processes. In this study, mussel shells were investigated in three areas in the sea of Chile; two areas with high aquaculture activity and one in a non-production area. Mass Spectrometry was used for [Cd] readings. There are no significant differences (p=0.92) in [Cd] between the studied areas. Additionally, the [Cd] observed in valves was also similar relative to different depths. The low [Cd] observed in valves (~0.014±0.0049mgCdkg-1 dry) suggests the potential use of this industrial byproduct in agricultural applications.