Barnacle settlement:field experiments on the influence of larval supply, tidal level, biofilm quality and age on Balanus amphitrite cyprids

Abstract

A set of 3 field experiments lasting 24 h was conducted during April 1998 at the Duke University Marine Laboratory (Beaufort, North Carolina, USA) to: (1) assess the influence of larval supply, intertidal height, quantity and quality of biofilm and age of the larvae on the settlement of Balanus amphitrite Darwin and (2) examine the correspondence between small-scale planktonic distribution of larvae, the initial spatial pattern of newly settled larvae and the vertical distribution of adult barnacles. Precolonized methacrylate (Plexiglas) disks, arranged within 3 blocks and established so as to eliminate edge effects within 3 large experimental panels, were placed at 3 predetermined tidal heights (High, Medium, Low) corresponding to the upper lirmt, modal zone and the lower limit of adults of B. amphitrite. Split-split-plot ANOVAs were performed on densities of newly attached larvae (metamorphosis not completed) to test their habitat selection behavior to surfaces which had been precolonized by microbiota (bacteria and diatoms) at 3 heights (origin factor) for 0, 7, 14 or 21 d (age factor). The physical environment (salinity, temperature, current flow) was stable and comparable during the 3 experiments. B. amphitrite cyprids were uniformly distributed in the water column. Larval supply was poorly correlated with the intensity of settlement over the 1 wk experimental period. In fact, the same larval supply could induce either high (4x) or low ( l X) settlement after 2 tidal cycles, and, inversely, similar settlement intensities were associated with planktonic larval abundance varying significantly at 2 d intervals (109 to 171 cyprids 923 l-l). Settlement was homogeneous on each experimental unit (no significant block effect). Tidal height, however, was a significant factor in determining the vertical patterns of newly settled larvae during the first experiment where larvae were abundant but not during subsequent experiments for which fewer larvae were collected. The degree of microbial precolonization was the main parameter affecting the settlement of B. amphitrite. For the first 2 experiments, 'weighed cyprid settlement' significantly decreased as the age of the biofilrn increased, revealing a strong preference of settlers for clean surfaces and avoidance of biofouled surfaces of all intertidal origins. Further analysis of biofilm samples showed that free-space availability in the microbial film and bacterial densities were significantly inversely correlated to settlement intensity. Moreover, settlement to 'favorable' substrata decreased by nearly % during our experimental period, suggesting changes in the selectivity of settling larvae. Our experiments confirm the role of larval supply in determining the vertical intertidal distribution of adults of B. amphitrite, but the short-term variability in the larval supplyhettlement coupling observed over a 1 wk period must be integrated in models of recruitment dynamics of barnacles.

Physiological condition of Balanus amphitrite cyprid larvae determines habitat selection success

“…Using a field experiment designed to study habitat selectivity, Olivier et al (2000) observed a positive correlation between Balanus ampitrite cyprid settlement and the nature of the biofilm on the settlement surface, with settling mainly occurring on surfaces free of detritus. Furthermore, these authors showed a significant decrease in cyprid settlement success with successive experiments over 6 d; this decrease was associated with a loss of habitat selectivity.…”

“…An analysis of the physiological condition of these cyprids, representing their energy content and age, would be an interesting opportunity to demonstrate the role of larval physiology in controlling the habitat selection behaviour leading to permanent attachment in the field. Thus, in this study, we analyzed the energy status of cyprids collected during this earlier experiment (Olivier et al 2000) to test the hypothesis that habitat selectivity and settlement success relies more on the physiological condition of the larvae rather than on the supply of larvae. The physiological condition of the larvae was examined in relation to the abundance of both nonsettled and settled larvae, substrata of different quality and intertidal position.…”

Deep sequencing of naupliar-, cyprid- and adult-specific normalised Expressed Sequence Tag (EST) libraries of the acorn barnacleBalanus amphitrite

“…So far, however, studies have been limited to the behavioural response of larvae to settlement cues. This has created a wealth of information on the environmental stimuli that B. amphitrite respond to during surface exploration (eg Rittschof et al 1984;Holmstro¨m et al 1992;O'Connor and Richardson 1998;Olivier et al 2000;Prendergast et al 2009;Aldred et al 2010) but the molecular mechanisms underlying these responses remain unclear. In recent years, Thiyagarajan and Qian (2008) have used a proteomics approach to investigate B. amphitrite development.…”

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

“…cannibalism), and larval physiology (age, competency, energy reserves) (Olivier et al, 2000;10 Qian et al, 2000;Marshall and Keough, 2003;Koehl et al, 2007;Tremblay et al, 2007) 11…”