Periodicity in Chthamalus fissus reproduction does not guarantee periodicity in settlement

Abstract

The timing of life history events can have profound implications for populations and communities, especially those events that influence species dispersal and recruitment. In benthic invertebrates, the majority of dispersal occurs during the larval phase of life. Yet the extent to which timing of reproduction (the beginning of the larval phase) directly influences timing of settlement (the end of the larval phase) is unclear, because biological and hydrodynamic processes can act to decouple these 2 events, and because reproduction and settlement are seldom studied together. Here, we used long-term (2014-2019) daily and weekly data from Bird Rock, La Jolla, California, USA, to look for lunar and seasonal cycles in reproduction and settlement timing of the acorn barnacle Chthamalus fissus, and we incorporated measurements of nearshore currents to examine the implications of reproduction timing on alongshore larval transport distances. We found evidence of lunar and seasonal cycles in reproduction but only limited cyclicality in settlement, possibly due to plasticity in larval development coupled with variable larval transport and dispersal. Our results demonstrate the complex nature of relationships between reproduction, larval transport, and settlement, which must be disentangled before accurate predictions can be made regarding the impacts of climate change on the population dynamics of marine species.