Early post-settlement mortality of an intertidal barnacle:a critical period for survival

Abstract

To determine ~f the onset of intertidal 11fe is a critical time for survival, we examined the fate of newly settled Balanus glandula, an intertidal barnacle, on natural rocky substrata in Barkley Sound, Br~tish Columbia, Canada. In total, 552 indiv~dual settlers were mapped and followed daily during their first 3 to 5 d after settlement in May 1992 and were then periodically re-examined over a 45 d period. A sharp decline in survivorship occurred during the first day after settlement. For settlers arriving on 16 and 17 May, mortality during the first day after settlement (38.0%) was almost as high as all mortality during the following 44 d (40.1 %). Mortality during the first day after settlement was 1.5 to 6.0 times higher than during the second day for settlers arriving on 16, 17 and 18 May. There was no relationship, however, between percent first day mortality and densities of recruits or of grazers (limpets, litto~ines). The elevated levels of first day mortality were also not consistent with desiccation stress, wave exposure, or size-specific changes in vulnerab~l~ty. The first moments after settlement may const~tute a bottleneck for the surv~val of barnacles settllng In the intert~dal zone. For organisms such as B glandula, selective pressures for traits such as t~m e of settlement relative to the tidal cycle, selection of settlement micro-site, and energy reserves at settlement could be most Intense during the first day in the benthic habitat.

Attachment of the peritrich epibiont Zoothamnium intermedium Precht, 1935 (Ciliophora, Peritrichia) to artificial substrates in a natural environment

“…In general, invertebrate larvae show a pattern of extensive initial exploration of the substrate, finally settling where more individuals of their own species are found (Knight-Jones and Crisp, 1953). This searching and settlement behavior would help avoid unfavorable environments where the adult will have a lower chance of survival, since early post-settlement mortality can sometimes be extremely high (Gosselin and Qian, 1996). This similar pattern of settling next to conspecifics displayed by different species of invertebrate larvae was suggested to be convergent (Knight-Jones and Crisp, 1953), and might be the same utilized by telotrochs of peritrich ciliates (Langlois, 1975).…”

Complexity and simplification in understanding recruitment in benthic populations

“…Stommel 1963), such as Ekman upwelling relaxation. Finally, researchers have paid little attention to small-temporal scales after settlement, yet for some systems, processes at very fine temporal scales are most important in influencing recruitment (Gosselin & Qian 1996, Pineda et al 2006). …”

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

“…Although settlement and recruitment 14 are straightforwardly defined, they are often confused (see Connell, 1985 for definitions and 15 discussion). It is possible to measure settlement of sessile species over short time intervals with 16 little error, because settlers accumulate on a given substrate area and do not move afterwards, 17 although mortality shortly after settlement is great (Gosselin and Qian, 1996). There is some 18 consensus that daily sampling of settlement is a good compromise between logistical difficulty 19 and accuracy of estimate (Connell, 1985), but some researchers have sampled every semidiurnal 20 tide (12.4 h, Wethey, 1986;Cruz et al, 2005;Jacinto and Cruz, 2008), and automated sampling 1 devices can sample for even shorter intervals (Whitlatch and Osman, 1998).…”