Juan Tarazona

Benthos communities in oxygen deficient shelf and upper slope areas of the Peruvian and Chilean Pacific coast, and changes caused by El Niño

Abstract Besides a well oxygenated shallow water area characterized by an extremely rich benthic life, most of the Peruvian and Chilean continental shelf and upper slope lies within an oxygen minimum zone (omz), the poor macrobenthic colonization of which is in striking contrast to the abundant pelagic life in the overlying waters. However, the eukaryotic benthos in this zone shares the seafloor with an important prokaryotic component of filamentous (‘sphagetti’) bacteria belonging mainly to the genus Thioploca. Under ‘normal’, non-Niño conditions, near-seafloor oxygen saturation values in this area rarely exceed 0.5 ml 1−1, and in some cases the bottoms are even anoxic. During strong El Niños, saturation periodically increases to >3.5 ml l−1, and higher oxygenation may persist for more than a year after the end of the event proper (which is characterized by increased water temperatures). In the shallow parts of the omz, the changes induced by El Niño cause drastic increases of macrobenthic density, biomass and diversity; immigration of benthos and fish species from (sub)tropical equatorial and oceanic areas; changes in trophic structure; and reduction of ‘spaghetti’ bacteria. In the case of the particularly strong 1982–83 El Niño, the communities of the shallower part of the omz had shifted back into their pre-Niño state about 13 months after the end of the warming event. In the deeper part of the omz, despite a similarly strong increase of oxygen saturation, a clearly positive development of macrobenthos during El Niño could not be observed. The reasons that may be responsible for this difference are discussed.

Changes in the structure of a shallow sandy-beach community in Peru during an El Niño event

Many infaunal sandy-bottom communities in shallow waters of the Peruvian upwelling system are inhabited by large coexisting populations of the surf clams Mesodesma donacium and Donax peruvianus as well as by the anomuran mole crab Emerita analoga. Under normal conditions, equilibrium states are possible with any one of these species dominating. A Mesodesma community south of Lima in Peru was investigated over 2,5 years, covering periods prior to, during and after the El Nino (EN) of 1982–83. It was revisited several times later. Growth, recruitment and mortality and, therefore, production of Mesodesma and Donax varied to some extent before EN. However, during the event Mesodesma became locally extinct and had not recolonized the area by July 1986, three years after the return of normal temperatures. Donax, which took over immediately after EN, never reached the densities of the former dominant Mesodesma. Emerita remained a rare species as well, whereas spionid polychaetes increased in importance. The medi...

The Peruvian Coastal Upwelling System

The Peruvian coastal upwelling ecosystem is part of an upwelling area that extends between 4°S and about 40°S along the western coast of South America (Guillen 1983), with high productivity originating from equatorial upwelling south of the Galapagos Islands. Peruvian coastal upwelling is peculiar because winds sustain the upwelling process throughout the year (Zuta and Guillen 1970) and the El Nino-Southern Oscillation (ENSO) cycle induces distinct interannual ecosystem variability. The coastal upwelling system, which hardly comprises 0.02% of the total ocean surface, is of great significance because it determines the enormous productivity of Peruvian coastal waters, representing almost 20% of the world’s landings of industrial fish.

Positive effects of “El Niño” on macrozoobenthos inhabiting hypoxic areas of the Peruvian upwelling system

SummarySoft-bottom macrozoobenthos was sampled at monthly intervals between September 1981 and September 1984 at a normally hypoxic site (34 m depth) in Ancón Bay (Peru). Temperature, salinity, and dissolved oxygen were measured and related to changes in community structure. Large increases in the number of species, density, biomass, and diversity of macrozoobenthos were observed during the 1982–1983 El Niño (EN) thermal anomaly and for 1 year afterwards. These favourable changes were mainly associated with increased oxygen concentrations found in water masses near the bottom. Results are consistent with the hypothesis that the processes of post-catastrophic recovery of macrozoobenthos on marine soft bottoms are largely predictable, although certain particular mechanisms seem to exist for post-hypoxic recovery during El Niño in areas of the Peruvian coastal upwelling.

Overview and challenges of Marine Biodiversity Research in Peru

El presente trabajo es una revision panoramica, aunque incompleta, de la biodiversidad biologica marina del Peru, que incluye el ecosistema de surgencias costeras peruano, las areas marinas someras de la costa peruana y el ecosistema de manglar del norte del Peru. Incluye un analisis de los avances en conservacion y manejo, y de los recursos con que se dispone para la investigacion. El analisis mostro principalmente la escasez de recursos humanos y las limitadas facilidades de laboratorios y de estaciones costeras de investigacion de que disponen las instituciones. Tambien se hizo un analisis de los vacios de informacion a nivel taxonomico y de estudios ecosistemicos, que reflejo una escasez de estudios en la mayoria de grupos taxonomicos y comunidades biologicas. Finalmente, las consultas y discusiones promovidas en el seno de la comunidad cientifica, permitieron identificar como principales retos para las investigaciones futuras a: la formacion y capacitacion de recursos humanos, el desarrollo de inventarios taxonomicos, el estudio de endemismos y areas de especiacion, la aplicacion de nuevas tecnologias en el monitoreo biotico y abiotico del ecosistema y la evaluacion de los impactos del cambio global sobre la biodiversidad marina.

Grazing effects of the periwinkle Echinolittorina peruviana at a central Peruvian high rocky intertidal

Echinolittorina peruviana is the most common gastropod in the high intertidal zone of Peru, representing more than 80% of the individuals present at that zone. Experimental removal of snails was used to evaluate their effects on (a) abundance of epilithic biofilm, (b) barnacle recruitment, and (c) abundance of macroalgae under “normal” conditions of the El Niño Southern Oscillation (ENSO). Experiments were carried out from October 2005 to April 2007 at two intertidal levels of a semi-protected rocky shore of central Peru. Results demonstrated that E. peruviana is able to control biofilm abundance and barnacle recruitment at both heights investigated, with marked effects in the lower zone. Erect macroalgae (Ulva spp. and Gelidium spp.) were less affected by grazing; but negative effects were observed on macroalgal crusts. Season and physical stress seem to play a more important role in the abundance of macroalgae in the high intertidal. Our results are similar to those reported elsewhere for high shore littorinids and represent baseline data to understand how the role of intertidal consumers will vary under the cold (La Niña) and warm (El Niño) phases of ENSO on these shores.

Crecimiento y producción somática de la concha de abanico (Argopecten purpuratus) en Bahía Independencia, Pisco (Perú) comparados entre eventos El Niño y La Niña

Resumen es: Argopecten purpuratus es el marisco de mayor importancia economica en la costa central del Peru, por su elevado volumen de extraccion en la pesca artesan...

Coastal upwelling may overwhelm the effect of sewage discharges in rocky intertidal communities of the Peruvian coast

In coastal productive environments, such as upwelling systems, sewage effluents might represent an important input of nutrients affecting intertidal community development and structure. Using descriptive and experimental approaches, the community spatial variation and early succession in relation to a point-source effluent discharge in a rocky intertidal of an upwelling affected area (Ancon Bay, Peru) was analysed. The relative contribution of herbivory to the observed patterns was also analysed. Dissolved nutrient concentrations, macroalgal isotopic signatures and N content revealed a significant input of nutrients at the outfall, although this contribution was not reflected in the algal assemblage, but in higher abundances of mytilids, ophiuroids and limpets. Cover of most sessile organisms (biofilm, Ulva spp., mytilids and barnacles) varied among sites throughout early succession, and grazers only enhanced the cover of the red algae Gelidium spp. Differences in succession patterns could not be attributed to discharge effects. The results of this study suggest that the community development is bottom-up controlled in the entire bay, which is likely to be due to the upwelling that operates at larger temporal and spatial scales. If so, nutrient input derived from coastal upwelling may sometimes overwhelm the role of anthropogenic nutrient loadings in shaping intertidal communities.