the humboldt current system of northern and central chile - figema

MARTIN THIEL ET AL.the dynamics of the benthos communities along the continental shelf and also the remineralisationof OM. There is indication that the upper depth limits of the low-oxygen fauna oscillates withupwelling strength (and EN). In parallel with these oscillations, the lower depth limit of benthoscommunities from the upper sublittoral zone shifts up and down. This community experiences atits upper depth limit the impact of EN events, where individual species or the whole communitymay temporarily disappear (due to water temperature, wave action or burial under terrigenoussediments). These extinction events affect the shallow sublittoral and intertidal biota along the HCSin northern and central Chile, but their intensity varies between events, often resulting in differentialelimination of particular species, while leaving others unaffected or favouring them. Similar variationin effect size is seen along the latitudinal gradient, where EN impacts (which may occur atall trophic levels) attenuate toward higher latitudes. This leads to different constellations in theinteraction webs found in pelagic and benthic communities. Spatial variability in upwelling, whichmitigates EN effects, further enhances the variability in the ecological responses. The diffuse patternof biogeographic limits observed in northern-central Chile is expression of this high variability.Studies of individual growth, reproductive potential, dispersal, recruitment, physiology and populationconnectivity of organisms from the HCS demonstrate the importance of life-history traits forimproving predictability of ecological processes in this area. The high temporal and spatial variabilityin oceanographic conditions and ecological processes in the HCS of northern-central Chilecomplicates management and conservation decisions (such as calculation of catch quotas or identificationof important areas for recruitment or growth). Recent studies have revealed small-scalevariability in reproductive potential, larval supply, recruitment and growth. This indicates thatspatially explicit conservation measures (e.g., MPAs) require information of high temporal andspatial resolution. For most parts of the coast of northern and central Chile such data are notavailable. Given this present gap in information and the urgent need for efficient conservation ofthis large marine ecosystem, a large-scale approach is proposed. Future conservation measuresshould also include terrestrial environments such as seabird breeding sites, dune fields and estuarinehabitats. Research and administration activities along the HCS face important challenges that requiresubstantial efforts, in particular a continuous and fluent communication among all involved parties.In order to achieve this, a common umbrella organisation that co-ordinates all these activities (andpermits rapid exchange of opinion and information) appears to be highly desirable.AcknowledgementsWe acknowledge the continuing financial support from FONDECYT, FONDAP, FONDEF, FIP,SHOA, MECESUP and DAAD. We are especially grateful to Jim Atkinson for his patience andcareful editing of the manuscript. We also would like to thank all our colleagues who allowed usto refer to their unpublished data and manuscripts.ReferencesAburto, J. & Stotz, W. 2003. Una experiencia de co-manejo de bivalvos en el marco de una nueva herramientade administración pesquera en Chile: las áreas de manejo. Policy Matters 12, 200–204.Acuña, E., Arancibia, A., Mujica, A., Cid, L. & Roa, R. 1998. Análisis de la pesquería y evaluación indirectadel stock de langostino amarillo en la III y IV Regiones. Informe Final FIP No. 96-08. Coquimbo,Chile.Acuña, E., Arancibia, A., Roa, R., Alarcón, R., Díaz, C., Mujica, A., Winkler, F.M. & Lépez, I. 1997. Análisisde la pesquería y evaluación indirecta del stock del camarón nailon (II a VIII Regiones). InformeFinal FIP No. 95-06. Coquimbo, Chile.304