Spatial and temporal variation in recruitment can be the leading determinant of population fluctuations in species with pelagic larval stages. Characterizing and identifying the causes of such variation is, therefore, necessary to understand population dynamics, and to develop conservation and management strategies. We examined spatial patterns in settlement and recruitment of the intertidal barnacles Jehlius cirratus, Notochthamalus scabrosus and Notobalanus flosculus, and their relationships with environmental variables operating at meso-(sea surface temperature, SST) and small (local topography) scales. Settlement and recruitment were studied over 6 mo at biweekly intervals at 16 sites along 120 km of coastline in central Chile. All species showed similar temporal patterns, with a peak in settlement and recruitment during austral spring. We decomposed the spatial patterns into their corresponding meso-scale trend (from a few to 10s of kilometers) and into their small-scale (site) residual variation. Recruitment of chthamaloid species was highly and positively correlated at meso-and small-scales, and the among-site rankings showed consistency of the spatial structure throughout the recruitment season. SST explained a significant fraction of the variance in recruitment of the chthamaloids at the meso-scale, and spatial analysis showed coincident decorrelation scales of about 35 km for SST and recruitment. In contrast, recruitment of balanoid species did not show a clear spatial structure, was not associated with meso-scale variation in SST, and local topography seemed to play a significant role in their settlement. Topographically modified upwelling dynamics over scales of 10s of kilometers is the most plausible factor shaping meso-scale variation in recruitment of chthamaloid barnacles, whereas settlement and recruitment of balanoid species seem more strongly influenced by processes acting at local scales. The spatial scale and structure of recruitment provide guidelines for the placement and spacing of protected areas in the region.

Phytoplankton and particulate organic matter constitute the primary food source for adult filter-feeders, as well as for larval stages of many benthic and pelagic organisms. The structure and dynamics of nearshore benthic communities may be associated with variation in nearshore primary production. However, we know little about the scales of variability in phytoplankton in nearshore waters along open coasts, or about their causes. To characterize spatial and temporal patterns of chl a concentration, we conducted 2.5 yr of daily, shore-based monitoring at 3 sites separated by 10s of km within an upwelling region in central Chile. We found that: (1) peaks in chl a concentration were typically short-lived, persisting no longer than 4 d, (2) blooms occurred in spring to early summer months at all sites, but also during autumn months at 1 site (Las Cruces), and (3) the intensity and frequency of blooms were consistently different among sites; highest concentrations were at Las Cruces, lower at El Quisco, and the lowest at Quintay. Analyses of wind data and surface temperature, and inspection of Advanced Very High Resolution Radiometer (AVHRR) satellite images, suggested that among-site differences were due, at least in part, to alongshore variation in upwelling intensity and the formation of warm-water pockets or upwelling shadows in sections of the coast, such as Las Cruces. In contrast to the spatial pattern described offshore and over larger spatial scales, chl a concentrations were significantly lower at the coldest site, Quintay, located at the core of an upwelling center (Pta. Curaumilla), than at the warmer site of Las Cruces, which lies downstream from upwelling. Day-to-day variation in chl a levels during spring at Las Cruces seems related to the alongshore intrusion of waters upwelled upstream. Overall, the pattern observed at our 3 sites, together with previous studies at other upwelling systems, suggests that sections of the coast around 15 to 20 km downstream (equatorward) from upwelling centers could exhibit consistently higher phytoplankton concentrations than sites located in front of upwelling centers, generating a source-sink type of geographic pattern of nearshore nutrients and phytoplankton along the coast.

Along the coast of central Chile, geographic trends of diversity have been inferred from literature compilations and museum collections based on species range limits for some taxonomic groups. However, spatially-intensive fieldbased assessments of macrobenthic species richness are largely missing. Over the course of a multiyear study (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005), we characterized latitudinal patterns of rocky intertidal diversity at 18 sites along the coast of central Chile (29-36º S). At each site, the number of sessile and mobile macrobenthic species was quantified in 0.25 m 2 quadrats. Two estimators of local (alpha) diversity were used: observed local species richness, calculated from the asymptote of a species-rarefaction curve, and the Chao2 index, which takes into account the effect of rare species on estimates of local richness. We identified a total of 71 species belonging to 66 genera for a total of 86 taxa. The most diverse groups were herbivorous mollusks (27 taxa) and macroalgae (43 taxa). Diversity showed a complex spatial pattern with areas of high species richness interspersed with areas of low richness. In accordance with previous work, we found no trend in the number of herbivorous mollusks and an inverse and significant latitudinal gradient in the number of algal species. Our results highlight the need for taxonomically diverse assessments of biodiversity of the dominant taxa that conform intertidal communities.