Meeting Abstract
Echinoderms are characterized by boom-bust population dynamics in which species exhibit rapid outbreaks followed by drastic die-off events. These extreme density fluctuations can be driven by both bottom-up (e.g. prey availability) and top-down (e.g. predator presence) forces, and recruitment bottlenecks may occur at a variety of life history stages (e.g. poor fertilization, high larval mortality, etc.) However, few studies have considered the importance of links between life history stages, particularly the potential role larval history has in impacting juvenile recruitment dynamics of echinoderms. Laboratory studies of the sea star Asterias forbesi have shown that larvae reared on low food concentrations have lower survival to settlement and metamorphose as smaller juveniles with fewer protective spines than those reared at high food concentrations. We extended these studies to test how differing levels of phytoplankton concentration during A. forbesi larval development impacts post-metamorphic juvenile performance and whether juveniles with access to high levels of food can overcome the negative effects of low larval food background. We manipulated food availability during larval rearing (two levels: high = 22,500 cells ml-1 or low = 7,500 cells ml-1) and during juvenile rearing (four levels: fed 6 juvenile mussels week-1, 3 juvenile mussels week-1, 1 juvenile mussel week-1 or unfed) to assess the relative importance of feeding in each life history stage. Our response variables were juvenile survival and growth, number of juvenile mussels eaten week-1 and mean size of juvenile mussels eaten. We then compared the effects of larval food availability with juvenile food availability to determine whether pre- or post-metamorphic processes have a greater impact on sea star growth and survival.
