Explore the vast range of titles available.

The transition of planktonic late-stage barnacle larvae to a benthic life requires enough energy to power settlement and metamorphosis, and may be compromised by food limitation during early ontogeny. We carried out a comparative study to better understand the larval physiology of space-monopolizing barnacles exposed to contrasting regimes of primary productivity: Chthamalus bisinuatus under a meso-oligotrophic regime on the southeastern coast of Brazil, and C. montagui under a highly productive regime on the southwestern coast of the British Isles. We used an index based on lipid composition—the triacylglycerol (TAG) to phospholipid (PL) ratio—to characterize lipid allocation (energy/structure) in the tissues of cyprid larvae and anticipated depleted TAG reserves in cyprids from less productive waters. Despite the considerably different levels of primary productivity between subtropical (1.31 ± 0.4 mg chl a m−3) and temperate waters (3.09 ± 1.2 mg chl a m−3), TAG/PL ratio and settlement success were comparable for C. bisinuatus and C. montagui. Lipid allocation of daily cohorts was also comparable for both chthamalids, with cyprids equally storing TAG reserves (≥50% of total lipid content). This points to an energetic threshold below which nauplii cannot develop to a cyprid and/or selection for lipid accumulation under poor trophic conditions. We highlight the challenges of directly relating estimates of primary productivity with food supply and larval physiological status, as lower chl a concentrations do not necessarily indicate food limitation for barnacle nauplii. We propose a conceptual model to clarify the process of lipid allocation (energetic to structural lipids) in the tissues of cyprid larvae.

Biotic interactions will modulate species' responses to climate change. Many approaches to predicting the impacts of climate change on biodiversity so far have been based purely on a climate envelope approach and have not considered direct and indirect species interactions. Using a long-term observational data set (>30 years) of competing intertidal barnacle species, we built a hierarchy of age-structured two-taxa population models (Semibalanus balanoides vs. Chthamalus montagui and C. stellatus combined as one taxon) to test if the presence of a dominant competitor can mediate climatic influence on the subordinate species. Models were parameterized using data from populations on the south coast of southwest England and verified by hindcasting using independent north coast population data. Recruitment of the dominant competitor, S. balanoides, is driven by temperature. The mechanisms of competition explored included simple space preemption and temperature-driven interference competition. The results indicate that interspecific competition between juvenile barnacles is important in regulating chthamalid density but not that of the dominant competitor S. balanoides. Simulations were carried out using alternative future climate scenarios to predict barnacle population abundance over the next century. Under all emission scenarios, the cold-water S. balanoides is predicted to virtually disappear from southwest England by the 2050s, leading to the competitive release of Chthamalus throughout the entire region and thereby substantially increasing its abundance and occupied habitat (by increasing vertical range on the shore). Our results demonstrate that climate change can profoundly affect the abundance and distribution of species through both the direct effects of temperature on survival, and also by altering important negative interactions through shifting competitive balances and essentially removing dominant competitors or predators. Climate change impacts on organisms are unlikely to lead only to straightforward, easily predictable changes in population size and distribution. The complex, indirect effects of climate change need to be taken into account if we are to accurately forecast the long-term effects of global warming.

The contribution of the intertidal barnacle Chthamalus montagui to CO sub(2) fluxes via respiration and calcification was measured both in the air and underwater. The mean biomass of the species was 44.92 g ash-free dry weight (AFDW) m super(-2) on the coast of Brittany, France. Underwater respiration, determined from changes in dissolved inorganic carbon (DIC), fluctuated from 6.14 kmol g super(-1) h super(-1) in winter to 13.37 kmol g super(-1) h super(-1) in summer. The contribution of C. montagui respiration to DIC fluxes for an average daily immersion time of 8 h was 3.21 mmol m super(-2) d super(- 1). Mean aerial CO sub(2) respiration was estimated at 7.60 kmol g super(-1) h super(- 1) using an infrared gas analyser, corresponding to 5.46 mmol m super(-2) d super(-1) if the mean daily emersion time is 16 h. Net calcification was positive, with a mean value of 1.01 kmol g super(-1) h super(-1), corresponding to a CO sub(2) flux of 0.25 mmol m super(-2) d super(-1). The total mean daily emission of CO sub(2) by C. montagui populations was 8.92 mmol m super(-2) d super(-1). The annual carbon production by the species was 39.07 g m super(-2) yr super(-1) with relative contributions by aerial respiration, underwater respiration and net calcification of 61, 36 and 3%, respectively. The daily ratio of aerial:underwater carbon emission was 1.7, emphasizing the prevalence of aerial respiration and the metabolic adaptation of C. montagui to amphibious life.

Calcification, a process common to numerous marine taxa, has traditionally been considered to be a significant source of CO sub(2) in tropical waters only. A number of relatively recent studies, however, have shown that significant amounts of CO sub(2) are also produced in temperate waters, although none of these studies was carried out on rocky shores, which are considered to be very productive systems. We compared the CO sub(2) fluxes due to respiration and calcification in two temperate species, the cirripedes Chthamalus montagui and Elminius modestus. The population dynamics of both species were estimated at two sites during a 1-year experimental period in order to establish mean organic (ash-free dry weight) and CaCO sub(3) (dry shell weight) production. Based on these parameters, we estimated the CO sub(2) fluxes due to respiration and calcification. CaCO sub(3) production was estimated to be 481.0 and [Equation] at each site, representing 3.4 and [Equation] respectively, of released CO sub(2). These fluxes represent each 47% of the CO sub(2) released as a result of respiration and calcification. The production of CaCO sub(3) at the high-density site was: (1) among the highest values obtained for temperate organisms, and (2) comparable to the estimated CO sub(2) fluxes for coral reefs. As calcifying organisms are well represented in temperate ecosystems in terms of both density and biomass, our results provide clear evidence that calcification of temperate organisms should not be underestimated. Additional studies on other rocky shore taxa are needed before the relative importance of calcification in rocky intertidal carbon budgets can be generalized.

The urgency to find efficient indices and indicators to prevent further deterioration of coastal areas is one of the hot topics in today’s scientific publication. However, a detailed knowledge of community responses to anthropogenic impacts is essential to sustain those indices. The studies on the response of benthic community to sewage pollution on intertidal rocky shores are generally based on visual census and do not take into account the tidal levels. In order to fulfil this gap in this study: (i) the sampling was performed by destructive sampling, with all individuals identified to the species level; (ii) the sampling was done at all levels of the intertidal (sublittoral fringe, eulittoral, and littoral fringe). Sewage pollution changed the environmental variables and the abundance of macroinvertebrates, being Mytilus galloprovincialis, Melarhaphe neritoides, and Chthamalus montagui the species most responsible for the dissimilarities observed. Effects were different on the three intertidal zones: community structure changed in the sublittoral fringe; suspension-feeders abundances and species richness increased in the eulittoral; no differences were detected in the littoral fringe. Moreover, the results confirm that the presence of sewage discharges tended to benefit suspension feeders, and that the sensitive species were replaced by opportunistic ones.

Space is one of the primary limiting resources for organisms on the intertidal rocky shore. This paper examined the effect of reduced density on key traits (mortality and growth) on the intertidal barnacles, Chthamalus montagui and Semibalanus balanoides, on the mid-shore in Plymouth, UK. Intra- and interspecific treatments comprising of C. montagui and S. balanoides were manipulated to reduce densities at two similar sites. Changes in mortality and operculum growth were assessed over an 8-week period using digital photography. Covariates of growth included nearest neighbour distance, competition between closest pairs and initial size. Conflicting patterns were observed when comparing growth rates between treatments and sites. At Site 1, interspecific treatments had a lower growth rate than intraspecific treatments, whereas at Site 2, interspecific growth rates were higher. ANCOVA showed that nearest neighbour distance had no significant effect on growth, but when comparing differences in growth of closest neighbouring pairs, C. montagui treatment showed evidence of competition whereas S. balanoides did not. ANCOVA analysis indicated no difference in growth between each outcome of pair competition, suggesting winners are initially bigger than losers. Comparisons of mortality between treatments indicated mortality over time with no significant differences observed between treatments, but response surface methodology (RSM) revealed no effects of competition on mortality of S. balanoides, but negative effects of both intra- and interspecific competition on C. montagui survivorship. Examination of natural populations of barnacles in the mid-shore indicated there was strong spatial variation in growth rates, perhaps driven by small-scale differences within sites.

The acorn barnacle Chthamalus montagui can present strong variation in shell morphology, ranging from flat conic to a highly bent form, caused by a substantial overgrowth of the rostrum plate. Shell shape distribution was investigated between January and May 2004 from geographical to microhabitat spatial scales along the western coast of Britain. Populations studied in the north (Scotland and Isle of Man) showed a higher degree of shell variation compared to those in the south (Wales and south-west England). In the north, C. montagui living at lower tidal levels and in proximity to the predatory dogwhelk, Nucella lapillus, were more bent in profile. Laboratory experiments were conducted to examine behavioural responses, and vulnerability of bent and conic barnacles to predation by N. lapillus. Dogwhelks did not attack one morphotype more than the other, but only 15 % of attacks on bent forms were successful compared to 75 % in conic forms. Dogwhelk effluent reduced the time spent feeding by C. montagui (11 %), but there was no significant difference between conic and bent forms. Examination of barnacle morphology indicated a trade-off in investment in shell structure and feeding appendages associated with being bent, but none with egg or somatic tissue mass. These results are consistent with C. montagui showing an induced defence comparable to that found in its congeners Chthamalus anisopoma and Chthamalus fissus on the Pacific coast of North America, but further work to demonstrate inducibility is required.

The biological performance of species close to their biogeographic boundaries is of critical interest in a period of rapid climate change and can inform predictions of future patterns of distribution. The classic view is that performance attributes (reproduction, growth, survival) will gradually decline from the centre towards the edge of a species range. A persistent discontinuity in the distribution of the intertidal barnacleChthamalus montaguion the central south coast of England has enabled us to test hypotheses about its performance and recruitment as the range edge is approached. Although adult density was reduced by over 5 orders of magnitude along a 200 km distance, there was little evidence of impaired performance at the range edge. There have been fluctuations in abundance over the last 50 yr at shores approaching the border, which are associated with changes in temperature and suggest thermal sensitivities. A study of recruitment inC. montaguiand in other intertidal barnacles revealed a region of very low recruitment for all species close to the border ofC. montagui. We propose that reductions in larval supply caused by complex regional hydrography and suboptimal habitat quality, not adult performance, is most likely responsible for a steep gradient in recruitment as the border is approached, although possible reductions in larval performance cannot be totally discounted. The location of ‘low recruitment cells’ caused by oceanographic processes that obstruct the dispersal of propagules needs to be identified when modelling the rate of change of biological assemblages and the location and spacing of reserves.

The distribution of cirripede cyprids in relation to associated oceanographic conditions was obtained from a grid survey and intensive vertical sampling at a fixed station located 21 km off the northwest Portuguese coast in May 2002. Analysis of cyprid length composition allowed separation of 3 species groups.Chthamalus montagui,Pollicipes pollicipesandBalanus perforatuswere largely restricted to the neuston layer and showed only low-amplitude vertical migration. MostC. stellatuscyprids only appeared in the upper 20 m at night, a migration which did not appear to be affected by physical conditions in the water column, but some differences in the vertical migration pattern between days were probably related to varying light penetration.C. montaguiis the most abundant adult species found along the Portuguese coast, butC. stellatuscyprids, at densities of up to 8.7 ind. m–3, were the most common sampled in all depth strata at the fixed station. Cyprid horizontal distribution was mainly restricted to an offshore band along the inner shelf, where highest densities were 11 to 15 ind. m–3. This distribution pattern was considered to result from upwelling-favourable wind conditions, creating fronts along the shelf in which the cyprids become concentrated. Cyprid vertical migration, in association with current vertical shear and onshore movement of fronts during upwelling-relaxation periods, may be the mechanisms returning cyprids to the coast to settle. The regularity of these events in the region falls within the period of cyprid viability.

Many warm-water (Lusitanian) species reach their limits in the central English Channel, failing to penetrate to the North Sea. We re-surveyed the eastern limits of the Lusitanian intertidal barnacles Chthamalus montagui and C. stellatus, from 1994 to 2004, a decade of exceptionally high sea temperatures, and found range extensions on both sides of the Channel compared to the 1950s and 1970s. Annual recruitment of Chthamalus on the English coast was monitored. There was a consistent gradient of low recruitment to the east of Portland Bill, with significant reductions coinciding with prominent headlands. Highest recruitment occurred during the warmest years. Cluster analysis showed a high degree of similarity of annual recruitment within coastal cells suggesting that local processes are also important. In 1999 we compared recruitment in the other common intertidal barnacles, the boreal Semibalanus balanoides and the non-native Elminius modestus, with Chthamalus spp. All species showed low recruitment between Selsey Bill and Portland Bill, suggesting habitat limitations and/or hydrographic mechanisms. Annual recruitment of Chthamalus at existing limits on the Isle of Wight was positively correlated with the number of days of westerly and south-westerly winds during the summer, coinciding with the pelagic larval phase. A ‘pulse’ of high Chthamalus recruitment on the Isle of Wight, measured during the summer of 2000, reversed population decline. Only a higher frequency of such pulses will maintain populations at existing limits and increase the rate of range extension towards the North Sea. Such extension will be limited by lack of hard substrata, but proliferation of coastal defence schemes in recent years is increasing suitable habitat for barnacles.