On the Biology of an Intertidal Chthamalid (Crustacea, Cirripedia) from the Chukchi Sea

A Pacific-boreal species, Chthamalus dalli occurs in the narrow intertidal zone near Cape Thompson, Alaska. Diatoms and filamentous green algae, but no other animals, were associated with the barnacles, which apparently survive the winter frozen in the ice foot. Growth is less than in southern species, but continues for five or more years; maturity is reached in two years and breeding can occur at a water temperature of 6C. There appears to be only a very slight cold adaptation, shown by cirral activity, compared with C. dalli from Southeast Alaska and southern California.Sur la biologie d'un chthamalide intertidal (Crustacea, Cirripedia) de la mer de Tchoukotsk. Près du cap Thompson, Alaska, on trouve dans la zone intertidale l'espèce pacifique-boréale Chthamalus dalli. A part quelques algues éphémères, les autres organismes sont absents de la zone intertidale : la cirripède en question passe l'hiver gelée dans le pied-de-glace. La croissance, étudiée sur les anneaux de la coquille, semble plus lente que dans des localités plus méridionales, mais dure cinq ans ou plus : la maturité est atteinte en deux ans et la reproduction a lieu à une température de l'eau de mer de 6ºC. La comparaison entre les courbes de l'activité cirrale et de la température montre un léger déplacement latéral (adaptation au froid) par rapport à la même espèce dans le sud-est de l'Alaska et le sud de la Californie.Les auteurs discutent de l'absence de l'espèce boréale-arctique Balanus balanoides et concluent que pour les conditions hydrographiques existantes, la période de reproduction estivale plus longue chez C. dalli a pu lui donner un avantage sur B. balanoides dans la colonisation de l'est de la mer de Tchoukotsk

From the individual to the community and beyond: water quality, stress indicators and key species in coastal waters

This review examines water quality and stress indicators at levels of organisation from the individual to the community and beyond by means of three case studies concentrating on rocky shores within the north-east Atlantic. Responses of dogwhelks (Nucella) to tributyltin pollution from antifouling paints is examined as the main case study. There are effects at the individual level (development of male sexual characteristics in the female leading to effective sterility) and population level (reduction in juveniles, few females and eventual population disappearance of dogwhelks in badly contaminated areas) but information on community level effects of dogwhelk demise is sparse. Such effects were simulated by dogwhelk removal experiments on well studied, moderately exposed ledges on shores on the Isle of Man. The removal of dogwhelks reduced the size and longevity of newly established Fucus clumps that had escaped grazing. Removal of dogwhelks also increased the likelihood of algal escapes. In a factorial experiment dogwhelks were shown to be less important than limpets \{Patella) in structuring communities but still had a significant modifying effect by increasing the probability of algal escapes. Community level responses to stress on rocky shores are then explored by reference to catastrophic impacts such as oil spills, using the Torrey Canyon as a case study. Recovery of the system in response to this major perturbation took between 10-15 years through a series of damped oscillations. The final case study is that of indicators of ecosystem level change in response to climate fluctuations, using ratios of northern \{Semibalanus balanoides) and southern (Chthamalus spp.) barnacles. Indices derived from counts on the shore show good correlations with inshore sea-water temperatures after a 2-year lag phase. The use of barnacles to measure offshore changes is reviewed. The discussion considers the use of bioindicators at various levels of organisation

Influence of recruitment and temperature on distribution of intertidal barnacles in the English Channel.

Many warm-water (Lusitanian) species reach their limits in the central English Channel, failing to penetrateto the North Sea. We re-surveyed the eastern limits of the Lusitanian intertidal barnacles Chthamalus montaguiand C. stellatus, from 1994 to 2004, a decade of exceptionally high sea temperatures, and found range extensionson both sides of the Channel compared to the 1950s and 1970s. Annual recruitment of Chthamalus on theEnglish 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 thewarmest years. Cluster analysis showed a high degree of similarity of annual recruitment within coastal cellssuggesting that local processes are also important. In 1999 we compared recruitment in the other commonintertidal 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/orhydrographic mechanisms. Annual recruitment of Chthamalus at existing limits on the Isle of Wight was positivelycorrelated with the number of days of westerly and south-westerly winds during the summer, coincidingwith the pelagic larval phase. A ‘pulse’ of high Chthamalus recruitment on the Isle of Wight, measured duringthe warm summer of 2000, reversed population decline. Only a higher frequency of such pulses will maintainpopulations at existing limits and increase the rate of range extension towards the North Sea. Such extensionwill be limited by lack of hard substrata, but proliferation of coastal defence schemes in recent years is increasingsuitable habitat for barnacles

Advances In:Marine Biology

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Larval development of the intertidal barnacles Chthamalus stellatus and Chthamalus montagui

Two recently-distinguished species of Chthamalus (Cirripedia) are found on rocky shores in the north-eastern Atlantic: C. stellatus predominant on islands and headlands and C. montagui more abundant in bays. Larvae of the two species were produced in laboratory cultures to describe and compare the morphology and to allow identification in plankton samples. Nauplius larvae of C. stellatus are up to 30% larger than those of C. montagui. Differences in setation are minor. The two species are easily distinguishable from the size and shape of the cephalic shield. Chthamalus stellatus has a subcircular shield with longer body processes in later stages while C. montagui is more ovoid. The former develop more slowly in culture than the latter. Chthamalus stellatus larvae in a culture at 19 °C reached stage VI in 16 d compared to 11 d for larvae of C. montagui at the same temperature. The morphology and longer development time of C. stellatus larvae suggests adaptation to a more oceanic lifestyle and wider dispersal to reach more fragmented habitats than larvae of C. montagui

Seventy years' observations of changes in distribution and abundance of zooplankton and intertidal organisms in the western English Channel in relation to rising sea temperature

1. Extensive changes in marine communities in southwest Britain and the western English Channel have been recorded during the past 70 years.2. Over the same period there was a climatic warming from the early 1920s, then a cooling to the early 1980s, with recent resumption of warming; the change in annual mean temperature was approximately ±0.5°C.3. Marked changes occurred in plankton community structure; the distribution of both plankton and intertidal organisms was affected, with latitudinal shifts of up to 120 miles; there were increases or decreases of 2–3 orders of magnitude in abundance.4. Warm water species increased in abundance and extended their range during periods of warming, while cold-water species declined or retreated; the reverse occurred during the period of cooling.5. Climate change can influence marine communities by a combination of: direct effect on the organisms; effects mediated by biotic interactions; and indirectly through ocean currents.6. From climate models that indicate rises of mean temperature of 2°C in the next 50 years, and from the observed changes, we can expect future latitudinal shifts of 200–400 miles in distribution of plankton, fish and benthos, with extensive restructuring of planktonic, pelagic and benthic communities.7. Species common now in the Bay of Biscay will become common in the English Channel; those presently restricted to the western English Channel could colonise the central Irish Sea; changes in community structure could lead to lower abundances of infaunal benthos and fish.8. To fully prove the effects of global warming, future changes in the marine biota must exceed those recorded in the 1950s and 1960s