Barnacle Recruitment and Population Dynamics Predicted from Coastal Upwelling

Abstract

Statistical models were developed to predict upwelling intensity and barnacle recruitment in central California. Coastal sea surface temperature (SST) is used as an indicator of upwelling intensity. SST is predicted for 1984-92 with time series models. These models predict SST one day ahead, from present values of SST and from wind stress estimates that were obtained either directly from coastal buoys (WS) or indirectly from the Bakun Index (BI). The time series models can explain nearly 80% of the variance in SST. Recruitment was then predicted from upwelling intensity with regression models. Recruitment was observed every second day during the summer of 1988 in 6 sites in central California. Nearly 60% of the variance in recruitment is explained by variance in SST. A model for the dynamics of an open, space-limited benthic population was used to study the importance of time-varying recruitment on the population dynamics of barnacles. The input to the population model is a recruitment time series derived from a stochastic SST time series, and its output is a time series of free space. Due to the relatively slow individual growth of barnacles, the signature of an environmental signal (SST) on the dynamics of barnacles populations may last for many years, especially at low recruitment rates. At high recruitment rates post-recruitment processes dominate the population dynamics of barnacles and tend to erase environmental signals. Also, the biological processes filter the SST signal in a way that causes free space to oscillate in certain frequencies.