Sexual Recruitment in Zostera marina: Progress toward a Predictive Model

Does the Presence of Boring Sponges Alter Timing of Sex Change in Slipper Shell Snails, Crepidula fornicata?

AbstractThe Atlantic slipper limpet, Crepidula fornicata, is a sequential hermaphrodite whose size at sex change is plastic with respect to social and population cues. As an organism allocates energy between growth, reproduction, and maintenance, the increased cost of one process may affect another. Thus, C. fornicata affected by a stressor might have to alter the balance of energy allocation, potentially leading to changes in the timing of sex change. One such biotic stressor, the boring sponge Cliona celata, has been demonstrated to affect growth and condition of numerous molluscs. In this study, we explored whether the presence of the boring sponge affected the rate of sex change for C. fornicata, using both field surveys and an in situ manipulation. Population surveys suggested that while boring sponges may reduce tissue condition of slipper limpets, this relationship is highly variable and likely confounded by site variables. Using population metrics (size at sex, L₅₀), the presence of a boring sponge did not appear to affect sex change. Likewise, during the in situ experiment where we manipulated stack sex ratios, we did not find any differences in the timing of sex change between male-male and male-female stacks, even though C. fornicata without sponges grew significantly faster. Thus, results from field surveys and our in situ experiment suggest that sex change in this species appears robust to biotic stressors. This study suggests that C. fornicata will undergo sex change when conditions dictate, even if it is experiencing some level of biotic stress, a strategy that likely allows it to maximize lifetime reproductive output.

Patterns and mechanisms of dispersal in a keystone seagrass species

Mechanisms and vectors of long-distance dispersal remain unknown for many coastal benthic species, including plants. Indications for the possibility for long-distance dispersal come from dispersal modelling and from genetic assessments, but have rarely been assessed with both methods. To this end, we assessed dispersal of the seagrass Zostera noltei, an important foundation species of the coastal zone. We investigate whether small scale seed dispersal and long-distance propagule dispersal do play a role for meta-population dynamics, using both genetic assessments based on eight microsatellite markers and physical modelling of ocean currents. Such assessments enhance our understanding of the biology and population dynamics of an important coastal foundation species. They are relevant for large scale conservation strategies as they give insights in the maintenance of genetic diversity and connectivity that may enhance resilience and resistance to stresses associated with seagrass loss.