Human-induced metals accumulation in sediments of an industrialized bay of northern Chile. An enrichment and ecological risk assessment based on preindustrial values.

Environmental assessment in marine systems is difficult because most of the time their preindustrial characteristics are not available. Four sediment cores taken in Mejillones bay (northern Chile) were used to establish preindustrial metals concentrations, and to assess the environmental status of this industrialized zone. According to historical documents, the beginning of the industrial era start in 1850 CE. Considering this, the preindustrial concentration of some metals was established, by mean of a statistical approach. Most of the metals increase their concentration from the preindustrial to the industrial period. Environmental assessment showed an enrichment of Zr and Cr, a moderately polluted condition, and a low probability of toxic effect on the biological communities. The preindustrial values derived from sediment cores are a good tool to evaluate the environmental condition of Mejillones bay. However new information (backgrounds with a higher spatial representativity, toxicological threshold, and others) it is necessary to improve the environmental assessment of this environment.

Multifarious anchovy and sardine regimes in the Humboldt Current System during the last 150 years.

The Humboldt Current System (HCS) has the highest production of forage fish in the world, although it is highly variable and the future of the primary component, anchovy, is uncertain in the context of global warming. Paradigms based on late 20th century observations suggest that large-scale forcing controls decadal-scale fluctuations of anchovy and sardine across different boundary currents of the Pacific. We develop records of anchovy and sardine fluctuations since 1860 AD using fish scales from multiple sites containing laminated sediments and compare them with Pacific basin-scale and regional indices of ocean climate variability. Our records reveal two main anchovy and sardine phases with a timescale that is not consistent with previously proposed periodicities. Rather, the regime shifts in the HCS are related to 3D habitat changes driven by changes in upwelling intensity from both regional and large-scale forcing. Moreover, we show that a long-term increase in coastal upwelling translates via a bottom-up mechanism to top predators suggesting that the warming climate, at least up to the start of the 21st century, was favorable for fishery productivity in the HCS.

Long-term parasitic association between the boring polychaete Polydora bioccipitalis and Mesodesma donacium.

Polydora and related genera are common pests for molluscs. Establishing differences between native species and recent invaders provides the basis for understanding the effect of parasites and has implications for resource management. P. biocipitalis has been reported as a recently introduced species to the Chilean-Peruvian coast, raising concerns about its threat to native bivalve species. In contrast, studies on the infestation of P. bioccipitalis on the surf clam Mesodesma donacium, one of the most important species for shellfisheries, suggest a long-term parasitic relationship. The present study analyses infested (i.e. blistered) fossil shells of M. donacium deposited during the Holocene and Middle Pleistocene epochs and critically reviews evidence supporting the hypothesis of the recent introduction of P. bioccipitalis to the Chilean-Peruvian coast. The blistering pattern seen on fossil and recent shells can be considered species-specific for the infestation of M. donacium by P. bioccipitalis. No evidence was actually found on vectors, introduction pathways or distribution range to support the status of P. bioccipitalis as an introduced species. On the contrary, our findings point to a long-term association, at least for several hundred thousand years, between M. donacium and P. bioccipitalis.

Subdaily growth patterns and organo-mineral nanostructure of the growth layers in the calcitic prisms of the shell of Concholepas concholepas Bruguière, 1789 (Gastropoda, Muricidae).

Fluorochrome marking of the gastropod Concholepas concholepas has shown that the prismatic units of the shell are built by superimposition of isochronic growth layers of about 2 mum. Fluorescent growth marks make it possible to establish the high periodicity of the cyclic biomineralization process at a standard growth rhythm of about 45 layers a day. Sulphated polysaccharides have been identified within the growth layers by using synchrotron radiation, whereas high resolution mapping enables the banding pattern of the mineral phase to be correlated with the layered distribution of polysaccharides. Atomic force microscopy has shown that the layers are made of nanograins densely packed in an organic component.

Registros del fenómeno El Niño en el Perú

El Niño es un fenómeno característico de la variabilidad climática interanual del Perú. A la par con los estudios de monitoreo y modelaje de los parámetros oceano atmosféricos actuales, la comprensión de este fenómeno requiere una recosntrucción detallada de sus ocurrencias en el pasado. El el Perú, tales eventos han sido registrado en los archivos paleoclimáticos cuyas características: extensión, fiabilidad y resolución son aquí analizados (AU)

El fenómeno de "El Niño" y los moluscos de la costa peruana

Entre otros bioindicadores del fenómeno el Niño, los moluscos litorales presentan la ventaja de tener un esqueleto carbonatado que suelen preservarse tanto en conchales de origen antrópico, como en depósitos geológicos naturales. Por la distribución de las provincias zoogeográficas en las costas del Perú y por el fuerte impacto de las anomalías oceáno climáticas del Niño en esta región, es de esperarse que las conchas de moluscos subactuales o fósiles puedan jugar un papel importante en la identificación de ocurrencias de eventos, El Niño es el pasado. Se analizan, pues, las evidencias de presencia/ausencia de ciertas especies de bivalvos y gastrópodos en depósitos arqueológicos y geológicos, a la luz de las observaciones realizadas sobre el impacto de los eventos recientes de 1982-1983 y 1986-1987. Esta recopilación de datos realizados a eventos El Niño de los últimos años y a posibles ocurrencias de fenómenos en épocas más remotas, muestran que todavía quedan muchas incognitas en cuanto a la dinómica poblacional y la ecología de los moluscos en respuesta a la anomalía oceanográfica. Por lo tanto, una cierta prudencia es necesaria al pretender reconstituir este tipo de anomalías en el pasado. En algunos casos sin embargo, se presume la ocurrencia de condiciones de tipo El Niño, durante el holoceno como en ciertos interglaciales del Pleistoceno, las que aparentemente permitieron el traslado delarvas de organismos de la provincia panameña, o de la Zona de Transiciñn de paita, hasta las costas del Centro y sur del Perú (provincia Peruana) (AU)

Beach - ridge series in northern Peru : Chronology, correlation, and relationship with major late Holocene El Niño events

It has previously been hypothesized that the sequences of beach ridges observed at the mouth of the major rivers of the northern coast of Peru (Santa, Chira and Piura Rivers) might record the most intense events of the El Niño phenomenon that occurred in the second half of the holocene. The purpose of this paper is to reexamine this interpretation through a comparative study of the two sequences preserved north and south of the Chira rivers mouth. The beach ridges of the two sequences are different sedimentologically and geomorphologically but in both cases required, for the formation, particular meteorologic and oceanic conditions that correspond to very strong El Niño events. Special attention is paid to the radiochronologic data available for these two sequences (AU)