Temporal variation in intertidal community recruitment and its relationships to physical forcings, chlorophyll-a concentration and sea surface temperature

We investigated the recruitment of intertidal barnacles and mussels at three temporal scales (months, weeks and days), and its relationships to physical forcings, chlorophyll-a concentration (Chla) and sea surface temperature (SST), at both a local (km) and a regional (10–100 km) resolution. The study was conducted in the South Brazilian Bight, a subtropical region influenced by upwelling and meteorological fronts, where recruitment rates were measured monthly, biweekly and daily, from 2012 to 2013 using artificial substrates fixed in the intertidal zone. The strength of the relationship between recruitment and physical forcings, Chla and SST depended on the temporal scale, with different trends observed for barnacles and mussels. Barnacle recruitment was positively correlated with wind speed and SST and negatively related to the wind direction, cold front events and Chla. Wind direction was positively correlated with mussel recruitment and negatively covaried with SST. We calculated net recruitment (NR) to estimate the differences in recruitment rates observed at longer time scales (months and weeks), with recruitment rates observed at shorter time scales (weeks and days), and found that NR varied in time and among taxa. These results suggest that wind-driven oceanographic processes might affect onshore abundance of barnacle larvae, causing the observed variation in recruitment. This study highlights the importance of oceanic–climatic variables as predictors of intertidal invertebrate recruitment and shows that climatic fluctuations might have different effects on rocky shore communities.