Ocean conditions and bottom-up modifications of gonad development in the sea urchin Strongylocentrotus purpuratus over space and time

Abstract

Intraspecific life history attributes of growth, survival, and reproduction can vary in response to changes in the physical environment. These changes can induce a cascading effect across trophic levels. In marine systems, shifts in ocean conditions such as warm and cold phases of ENSO can change primary production in benthic algae, which in turn modify resources avail- able to benthic omnivores. Monthly gonad samples of the purple sea urchin Strongylocentrotus purpuratus were taken from 2007 to mid-2009 at sites from Vancouver Island, Canada, to Punta Baja, Mexico. Although mean sea surface temperature (SST) changed by ~8°C from north to south, latitudinal patterns of size-specific gonad weight were not detected, although differences existed across sites. At individual sites, mean SST changed by <1°C from 2007 to 2009. Gonad index data from Yankee Point, California (USA), from 1952 to 1964 included mean annual temper- atures that varied by 2.4°C and both strong El Nino and La Nina events. Yankee Point data showed significant (p ≤ 0.01) correlations with the Multivariate ENSO Index, SST, the Northern Oscillation Index, and the Oceanic Nino Index. Dissections at other sites along the coast from mid- 1960 to 2009 showed that size-specific gonad weights were lower during periods of El Nino than during periods of La Nina.