Seawater carbonate chemistry and survival of mollusks: Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica during experiments, 2009

We present experiments that examined the metamorphosis, growth, and survivorship of larvae from three species of commercially and ecologically valuable shellfish (Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica) at the levels of CO2 projected to occur during the 21st century and beyond. Under CO2 concentrations estimated to occur later this century (~66 Pa, 650 ppm), M. mercenaria and A. irradians larvae exhibited dramatic declines (>50%) in survivorship as well as significantly delayed metamorphosis and significantly smaller sizes. Although C. virginica larvae also experienced lowered growth and delayed metamorphosis at ~66 Pa CO2, their survival was only diminished at ~152 Pa CO2. The extreme sensitivity of larval stages of shellfish to enhanced levels of CO2 indicates that current and future increases in pelagic CO2 concentrations may deplete or alter the composition of shellfish populations in coastal ecosystems.

Seawater carbonate chemistry and biological processes of bivalve shellfish Mercenaria mercenaria and Argopecten irradians during experiments, 2011

The combustion of fossil fuels has enriched levels of CO2 in the world's oceans and decreased ocean pH. Although the continuation of these processes may alter the growth, survival, and diversity of marine organisms that synthesize CaCO3shells, the effects of ocean acidification since the dawn of the industrial revolution are not clear. Here we present experiments that examined the effects of the ocean's past, present, and future (21st and 22nd centuries) CO2concentrations on the growth, survival, and condition of larvae of two species of commercially and ecologically valuable bivalve shellfish (Mercenaria mercenariaand Argopecten irradians). Larvae grown under near preindustrial CO2concentrations (250 ppm) displayed significantly faster growth and metamorphosis as well as higher survival and lipid accumulation rates compared with individuals reared under modern day CO2 levels. Bivalves grown under near preindustrial CO2 levels displayed thicker, more robust shells than individuals grown at present CO2 concentrations, whereas bivalves exposed to CO2 levels expected later this century had shells that were malformed and eroded. These results suggest that the ocean acidification that has occurred during the past two centuries may be inhibiting the development and survival of larval shellfish and contributing to global declines of some bivalve populations.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

Evaluación poblacional de concha de abanico Argopecten purpuratus, Bahía Independencia – Pisco (10-21 Octubre 2012)

Entre el 10 y 21 de octubre 2012, se evaluó concha de abanico Argopecten purpuratus en los bancos naturales de Bahía Independencia. Temperatura superficial del mar presentó isotermas de 15, 16 y 17 °C desde Morro Quemado hasta Canastones. Densidad poblacional de adultos no superó 6 ind/m2. Biomasa estimada 422,514 t, la población 10,99 millones de individuos; el 19,2% de la población y 51,2% de la biomasa fueron ejemplares de talla comercial (≥ 65 mm). Se midieron 203 ejemplares, entre 3 y 101 mm de altura valvar, moda 49 mm y talla media 44,9 mm. Sexualmente se presentaron estadíos madurante (33,5%), inmaduro (31,5 %), desovante (28,6%) y desovado (5,9 %).

Evaluación poblacional de concha de abanico Argopecten purpuratus en Bahía Independencia-Pisco, 2012

Entre el 10 y 21 de octubre 2012, se evaluó la población de concha de abanico en los bancos naturales de la bahía Independencia. Entre Morro Quemado y Canastones se registraron las isotermas 15, 16 y 17 °C. A pesar de la presencia de “El Niño” “débil”, los resultados mostraron baja densidad poblacional de la especie que no superaron los 6 ind/ m2. La biomasa total estimada fue 422,514 t (±23,15%) y la población 10,99 millones de individuos (±23,09%), de los cuales el 19,2% de la población y 51,17% de la biomasa correspondieron a ejemplares de tamaño comercial (≥65 mm). Se midieron 203 ejemplares de concha de abanico, con tallas entre 3 y 101 mm de altura valvar, con moda en 49 mm y talla media 44,88 mm. Sexualmente predominaron los estadios madurante (33,5%), inmaduro (31,5%), desovante (28,6%) y desovado (5,9%).

Evaluación poblacional de Argopecten purpuratus (Lamarck, 1819) en bahía Independencia. Pisco, diciembre 2010

En diciembre 2010, se realizó una evaluación poblacional de la concha de abanico (Argopecten purpuratus) con la finalidad de determinar la distribución, abundancia y estructura poblacional en los bancos naturales de bahía Independencia, se empleó el muestreo al azar estratificado por profundidad. Las tallas fluctuaron entre 4 y 101 mm de altura valvar, media en 61,4 mm y se registró el 58,2% de ejemplares con tallas mayores a la mínima de extracción (≥65 mm). Predominaron ejemplares desovantes (92,1%). Se distribuyó formando agregaciones con concentraciones entre 1 y 5 ind.m-2. La población y biomasa total se estimó en 12,47 millones (±25,6%) y 948,2 t (±27,7%), respectivamente. Tunga y La Pampa se constituyeron como las áreas más importantes en población y biomasa.

Water temperature measured in Independence Bay, Pisco, Peru

Independencia Bay can be considered as one of the most productive invertebratc fishing grounds worldwide. One of the most important exploited species is the scallop (Argopecten purpuratus) with strong catching fluctuations related to El Nino and La Nina events and to inadequate Management strategies. During strong warming periods annual landings reach up to 50000 t in an area of about 150 km**2 and during cold years they remain around 500 to 1000 t. This study analyses the changes in scallop landings at Independencia Bay observed during the last two decades and discusses the main factors affecting the scallop proliferations during the EI Nino events. In this way data on landings, sea surface temperature and those related to growth, reproduction, predation, mean density and oxygen concentration from published and unpublished Papers are used. The relationship between annual catches and average water temperature over the preceding reproductive period of the scallop over the past 20 year's period, showed that scallop production is affected positively only with strong EI Nino such as those of 1983 and 1998. Our review showed that the scallop stock proliferation can be traced to the combined effect of (1) an increase in reproductive output through an acceleration of gonad maturation and a higher spawning frequency; (2) a shortening of the larval period and an increase in larval survival; (3) an increase in the individual growth performance; (4) an increase in the juvenile and adult survival through reduction of predator biomass; (5) an increase in carrying capacity of the scallop banks due to elevated oxygen levels.

Protocolo para la evaluación de concha de abanico Argopecten purpuratus (LAMARCK, 1819)

La Unidad de Investigaciones de Invertebrados Marinos en conjunto con las sedes descentralizadas del Instituto del Mar del Perú, IMARPE, con fines de establecer y estandarizar los procedimientos para la estimación de la población y biomasa de concha de abanico (Argopecten purpuratus) en áreas silvestres, elaboró este protocolo que describe los pasos a seguir desde la planificación en escritorio, la ejecución a bordo de embarcaciones, pasando por los cálculos estadísticos, hasta la elaboración del informe ejecutivo. La estimación de la población y biomasa de concha de abanico, en áreas silvestres se realiza dentro del contexto de evaluación poblacional, que involucra este primer aspecto e incorpora: estructura poblacional por tallas y madurez gonadal, relaciones biométricas y biológicas, y las condiciones ambientales predominantes del ambiente marino. La correcta aplicación de estos procedimientos conducirá a la obtención de información confiable.

Experiencias en sistema controlado para la obtención de semillas de concha de abanico Argopecten purpuratus (Lamarck, 1819) . Ilo, Moquegua

IMARPE Ilo obtuvo financiamiento del Gobierno Regional de Moquegua en base al proyecto "Mejoramiento de infraestructura e implementació n de laboratorio de investigació n de molusc"os, para construir un laboratorio experimental con el objetivo de desarrollar técnicas de reproducción artificial de moluscos nativos de la Región, para la obtención de semillas principalmente de macha Mesodesma donacium, chanque Concholepas concholepas y pulpo Octopus mimus. Este informe contiene el resultado de las actividades realizadas el 2007,en relación a la aplicación de técnicas de cultivo de microalgas (alimento vivo) y obtención de semillas de concha de abanico.

Evaluación poblacional de concha de abanico Argopecten purpuratus (Lamarck, 1819) en la isla Lobos de Tierra, 2010

Entre el 14 y 23 de diciembre 2010, se efectuó la evaluación poblacional de la concha de abanico en la isla Lobos de Tierra, su distribución se registró entre 6°21’12,6”S y 6°24’12,6”S, (noreste de Cabo Cruz y sur de Juanchuquita) y entre 6°26’38,8”S y 6°27’18,4”S (sur de Roca Blanca y norte de El Ñopo) a profundidades de 14,3 a 26,3 m. La altura valvar varió entre 7 y 107 mm. El rango más amplio de tallas y la mayor talla media (69,9 mm), se presentó en el estrato III. Predominaron los ejemplares desovados (37,50%) y desovantes (28,41%). Las densidades fluctuaron entre 1 y 77 ejem.m-2, predominando el rango entre 1 a 10 ind.m-2. La biomasa total fue estimada en 4962,716 t y la población en 87,61 millones de individuos El stock de juveniles (≤25 mm) fue de 0,18 millones de ejemplares y 0,012 t. El stock explotable (≥65 mm) estuvo constituido por 53,81 millones de individuos (61,42%) y 3.725,81 t (75,08%) de la biomasa. Se observó alta mortandad de individuos entre 14 y 77 mm de altura valvar, distribuidos en áreas con niveles de oxígeno menores a 0,1 mL/L, que coincidieron con sustratos reducidos localizados frente a La Grama.

Model parameter

Interannual environmental variability in Peru is dominated by the El Niño Southern Oscillation (ENSO). The most dramatic changes are associated with the warm El Niño (EN) phase (opposite the cold La Niña phase), which disrupts the normal coastal upwelling and affects the dynamics of many coastal marine and terrestrial resources. This study presents a trophic model for Sechura Bay, located at the northern extension of the Peruvian upwelling system, where ENSO-induced environmental variability is most extreme. Using an initial steady-state model for the year 1996, we explore the dynamics of the ecosystem through the year 2003 (including the strong EN of 1997/98 and the weaker EN of 2002/03). Based on support from literature, we force biomass of several non-trophically-mediated 'drivers' (e.g. Scallops, Benthic detritivores, Octopus, and Littoral fish) to observe whether the fit between historical and simulated changes (by the trophic model) is improved. The results indicate that the Sechura Bay Ecosystem is a relatively inefficient system from a community energetics point of view, likely due to the periodic perturbations of ENSO. A combination of high system productivity and low trophic level target species of invertebrates (i.e. scallops) and fish (i.e. anchoveta) results in high catches and an efficient fishery. The importance of environmental drivers is suggested, given the relatively small improvements in the fit of the simulation with the addition of trophic drivers on remaining functional groups' dynamics. An additional multivariate regression model is presented for the scallop Argopecten purpuratus, which demonstrates a significant correlation between both spawning stock size and riverine discharge-mediated mortality on catch levels. These results are discussed in the context of the appropriateness of trophodynamic modeling in relatively open systems, and how management strategies may be focused given the highly environmentally influenced marine resources of the region.

Biomineralization changes with food supply confer juvenile scallops (Argopecten purpuratus) resistance to ocean acidification

Future ocean acidification (OA) will affect physiological traits of marine species, with calcifying species being particularly vulnerable. As OA entails high energy demands, particularly during the rapid juvenile growth phase, food supply may play a key role in the response of marine organisms to OA. We experimentally evaluated the role of food supply in modulating physiological responses and biomineralization processes in juveniles of the Chilean scallop, Argopecten purpuratus, that were exposed to control (pH 8.0) and low pH (pH 7.6) conditions using three food supply treatments (high, intermediate, and low). We found that pH and food levels had additive effects on the physiological response of the juvenile scallops. Metabolic rates, shell growth, net calcification, and ingestion rates increased significantly at low pH conditions, independent of food. These physiological responses increased significantly in organisms exposed to intermediate and high levels of food supply. Hence, food supply seems to play a major role modulating organismal response by providing the energetic means to bolster the physiological response of OA stress. On the contrary, the relative expression of chitin synthase, a functional molecule for biomineralization, increased significantly in scallops exposed to low food supply and low pH, which resulted in a thicker periostracum enriched with chitin polysaccharides. Under reduced food and low pH conditions, the adaptive organismal response was to trade-off growth for the expression of biomineralization molecules and altering of the organic composition of shell periostracum, suggesting that the future performance of these calcifiers will depend on the trajectories of both OA and food supply. Thus, incorporating a suite of traits and multiple stressors in future studies of the adaptive organismal response may provide key insights on OA impacts on marine calcifiers.

Evaluación de bancos naturales de concha de abanico (Argopecten purpuratus) y de pulpo (Octopus mimus). Isla Lobos de Tierra (Noviembre 2009)

Se efectuó la evaluación de bancos naturales de concha de abanico y pulpo del 7 al 16 de noviembre del 2009. La concha de abanico se distribuyó entre 06°21’07,8’’ y 06°26’04,4’’S al noreste de Cabo Cruz y sur de Peña Negra, con densidades absolutas de 1 a 178 ejem.m-2, en profundidades de 12 a 27 m; las tallas variaron entre 2 y 100 mm de altura valvar, media 41 mm, presentando moda principal en 37 mm y dos modas secundarias en 4 y 79 mm; predominaron ejemplares desovantes (37%) y madurantes (29%), se detectó el 26% de inmaduros. La biomasa de concha de abanico fue estimada en 8.877 t y la población en 865 millones de individuos. El stock de juveniles (<25 mm) fue 96 millones de ejemplares (11% de la población) y 36 t, el stock explotable (≥65 mm) fue 83 millones de individuos y 4.376 t. El pulpo se encontró pobremente distribuido en los alrededores de la isla; la talla varió entre 85 y 150 mm de longitud del manto. El 100% de lo capturado tuvo peso inferior al mínimo legal de extracción (1 kg). Hembras y machos estuvieron en estadios en desarrollo y maduros (66,67%).