Limpet disturbance effects on barnacle recruitment are related to recruitment intensity but not recruit size

Abstract

Intertidal limpets are important grazers along rocky coastlines worldwide that not only control algae but also influence invertebrates such as common barnacles. For instance, grazing limpets ingest settling barnacle cyprid larvae (hereafter cyprids) and push cyprids and barnacle recruits off the substrate. Such limpet disturbance effects (LDEs) can limit barnacle recruitment, a key demographic variable affecting barnacle population establishment and persistence. In this study, we examined limpet (Lottia cassis) disturbance to barnacle (Chthamalus dalli, Balanus glandula) recruitment on the Pacific coast of Hokkaido, Japan, as information on limpet-barnacle interactions from this region is missing. We investigated, for the first time, whether barnacle size and recruitment intensity influence LDEs on barnacle recruitment. Small barnacles may be less susceptible to LDEs than larger barnacles, because small size may reduce the propbability of limpet disturbance. Moreover, recruitment intensity can influence LDEs, as high recruitment can compensate for LDEs on barnacle recruitment density. In Hokkaido, C. dalli cyprids are smaller than B. glandula cyprids, and C. dalli recruitment is higher than B. glandula recruitment. Thus, we hypothesized that LDEs on C. dalli recruitment would be weaker than those on B. glandula recruitment. To test our hypothesis, we conducted a field experiment during which we manipulated limpet presence/absence on the interior surfaces of ring-shaped cages. After four weeks, we measured barnacle recruitment and recruit size on the interior surfaces of the cages and found negative LDEs on C. dalli and B. glandula recruitment and recruit size. As hypothesized, the LDEs on C. dalli recruitment were weaker than the LDEs on B. glandula recruitment. Additionally, C. dalli recruits were smaller than B. glandula recruits. However, the LDEs on C. dalli recruit size were as strong as the LDEs on B. glandula recruit size, indicating that the smaller C. dalli recruits are not less susceptible to LDEs than B. glandula recruits. Since C. dalli recruitment was higher than B. glandula recruitment, we propose that the higher C. dalli recruitment compensated for the LDEs on C. dalli recruitment. Our findings indicate that the detected differences in LDEs on barnacle recruitment are related to barnacle recruitment intensity but not recruit size.

Complex interplays between limpets and alien species in South Africa: multispecies interactions, zonation and size effects

“…Our results show that the barnacle B. glandula has negative effects on S. granularis but positive effects on littorinids. There are many other examples of negative barnacle-limpet interactions (Dayton, 1971;Branch, 1976;Hawkins, 1983;Dungan, 1986;Santini et al, 2019;Ellrich et al, 2020), but in New South Wales, Creese (1982) showed that a small species of limpet, Patelloida latistrigata, benefits from the presence of barnacles that provide a refuge from competition with a larger species of limpet, Cellana tramoserica, which is excluded because it cannot move over and feed effectively on barnacles. Again, size matters.…”

“…Added to this, limpets can act is 'bulldozers', reducing the abundance of small settlers of species such as barnacles (Menge et al, 2010;Ellrich et al, 2020). The situation is even more complex when other members of the community indirectly influence the outcome of interactions.…”