Rocky Shore ecology

• Intertidal rocky habitats comprise over 50% of the shorelines of the world, supporting a diversity of marine life
and providing extensive ecosystem services worth in the region of US$ 5-10 trillion per year.
• They are valuable indicators of the impacts of climate change on the wider marine environment and ecosystems.
• Changes in species distributions, abundance and phenology have already been observed around the world in
response to recent rapid climate change.
• Species-level responses will have considerable ramifications for the structure of communities and trophic
interactions, leading to eventual changes in ecosystem functioning (e.g. less primary producing canopy-forming
algae in the North-east Atlantic).
• Whilst progress is made on the mitigation1 required to achieve goals of a lower-carbon world, much can
be done to enhance resilience to climate change. Managing the multitude of other interactive impacts on
the marine environment, over which society has greater potential control (e.g. overfishing, invasive non-native
species, coastal development, and pollution), will enable adaptation1 in the short and medium term of the next
5-50 years.

Chitons are very common molluscs on European rocky shores. They are common prey of fish and crabs and often display several colour morphs within a given habitat. Predation is one of the potential mechanisms accounting for chiton colour polymorphism. The colour variation is considered to provide a camouflage protection through a match with the substratum surface typology. However, the effectiveness of chiton polymorphism as a predation defence requires further investigation. Previously we found a relationship between chiton colour morphs and substrate characteristics, with chitons most commonly found on substrates that were of similar colour to their shells. Here, we examined whether each morph displayed an active choice for matching the substratum. Next, we assessed if the predation success of the intertidal common crab Carcinus maenas varied significantly with the absence/presence of an apparent camouflage effect created between the chiton colour morph and the substratum type. The present study indicates that chiton colour morphs probably actively choose substratum types where they blend in. Carcinus maenas was able to prey on all Lepidochitona cinereus colour morphs, regardless of the substrate camouflage effect. Surprisingly, the predation frequency was higher on camouflaged chitons than on contrasting chitons. It was concluded that chiton camouflage is probably not a defence mechanism against predation by the crab C. maenas, and that chiton colour polymorphism is probably promoted by other, more visual predators.

Tropical intertidal organisms tolerate large fluctuations in temperature and high desiccation rates when exposed during low tide. In order to withstand the short-term heat stress, intertidal organisms adopt behavioral responses to maximize their survival. Our previous research showed that tropical littorinids found at the upper and lower intertidal shores in Singapore exhibited different behavioral adaptations during low tide. Most of the upper-shore Echinolittorina malaccana kept a flat orientation, with the aperture against the substrate and the long axis of the shell towards the sun, whereas a majority of the lower-shore individuals of Echinolittorina vidua stood with the edge of the aperture perpendicular to the substrate on the rocky shore during low tide. This prompted analyses of the shells of these two species to determine whether the differences in the shell morphometry, microstructure, and thermal conductivity of shells of E. malaccana and E. vidua were associated with their respective behavioral responses to thermal stress. Analyses of shell morphometry and thermal conductivity showed that shells of E. malaccana were more likely to minimize heat gain, despite having a higher thermal conductivity on the outer surface, due to their light-gray, elongated shell. By contrast, the dark-colored, globose shells of E. vidua probably gain heat more readily through solar radiation. Scanning electron microscopy images of the shells of both littorinid species further revealed that they have cross-lamellar structure; however, only individuals of E. vidua showed the presence of disjointed rod layers and a pigmented inner shell surface. Individuals of E. malaccana had a rough outer shell surface with holes that inter-connect to form water-trapping channels that probably aid cooling. Individuals of E. vidua, however, had a smooth outer surface with rows of kidney-shaped depressions as microsculptures which probably help to stabilize shell shape. In both Echinolittorina species, behavioral responses were used to overcome thermal stress during low tide that was associated with shell morphometry and shell thermal conductivity. Such combined adaptations increase survivability of the littorinids at their respective tidal levels.

1.Current selection of marine protected areas in South Africa is based on objective criteria including biogeographic representation and habitat heterogeneity. This paper specifically examines rocky shores on the west coast of South Africa to determine whether they are divisible into discrete ‘habitats’ that need independent conservation.2.Seventeen rocky shores spanning the full spectrum of wave exposure were compared in terms of maximum wave forces, biomass, species richness and diversity among zones and sites. Three biotic assemblages were identified, characterizing sheltered, semi-exposed to exposed, and very exposed habitats. Differences among these were clear-cut low on the shore but disappeared at the top of the shore where wave action was attenuated and desiccation uniformly intense.3.The recognition of three discrete biologically-defined habitats means that rocky shores cannot be regarded as a uniform habitat for conservation purposes. All three components need protection if the full spectrum of rocky-shore communities is to be conserved.4.It is argued that this approach allows habitats to be defined in an objective manner, and that once this has been done, habitat heterogeneity constitutes a better measure of conservation value of an area than a ‘hotspot’ approach based on species richness and endemism. Copyright © 2008 John Wiley & Sons, Ltd.Current selection of marine protected areas in South Africa is based on objective criteria including biogeographic representation and habitat heterogeneity. This paper specifically examines rocky shores on the west coast of South Africa to determine whether they are divisible into discrete ‘habitats’ that need independent conservation.Seventeen rocky shores spanning the full spectrum of wave exposure were compared in terms of maximum wave forces, biomass, species richness and diversity among zones and sites. Three biotic assemblages were identified, characterizing sheltered, semi-exposed to exposed, and very exposed habitats. Differences among these were clear-cut low on the shore but disappeared at the top of the shore where wave action was attenuated and desiccation uniformly intense.The recognition of three discrete biologically-defined habitats means that rocky shores cannot be regarded as a uniform habitat for conservation purposes. All three components need protection if the full spectrum of rocky-shore communities is to be conserved.It is argued that this approach allows habitats to be defined in an objective manner, and that once this has been done, habitat heterogeneity constitutes a better measure of conservation value of an area than a ‘hotspot’ approach based on species richness and endemism.

Small basalt mounds with encrusting corals and inter-mound carbonate sandy zones with abundant rhodoliths corresponding to an ancient intertidal to shallow-water sea Xoor are exhumed from overlying volcaniclastic deposits and basalt lava Xows at Pedra de Água on Ilhéu de Cima oV Porto Santo, one of the islands of the northeastern Atlantic Madeira Archipelago (Portugal). The mounds rise above the surrounding surface to attain a height of about half a meter. The mounds exhibit an in situ assemblage of hermatypic corals, dominated by Tarbellastrae and Solenastrea. They formed as massive (4.2 £ 1.9 m average length), isolated patches in a protected bay close to shore eroded from an uneven basalt substrate dated to the Middle Miocene (14-15 Ma). The slightly deeper zones between basalt mounds, which alternate with them over a distance of more than 20 m, are covered mainly by coarse carbonate sand on which rhodoliths up to 14.8 cm in diameter are preserved in situ. Many rhodoliths have grown around a basalt core, which indicates a local, near-shore source for development. Complete burial of the elevated coral settlements and intervening low zones populated by rhodoliths occurred when volcanic lapilli and other tephra catastrophically buried this part of the rocky shore. The rhodoliths and coral assemblages exposed in an area of 12 m 2 were canvassed systematically using census quadrats to quantify community relationships.

ABSTRACT A low, rocky shoreline and attached abrasion platform of Late Pleistocene age are marked by a sharp disconformity within the Tamala Limestone Formation, exposed at Cape Burney facing the Indian Ocean near Geraldton, Western Australia. Colonization by an intertidal to shallow subtidal biota dominated by encrusting coralline red algae, oysters, and tube-dwelling worms occurs on a sandstone surface with a channeled topographic relief of 20–30 cm. The encrusting cup coral Rhizotrochus tuberculatus also is present, and this report details what is probably the first fossil occurrence of that species. The ancient rocky shore above this level retains trace fossils characteristic of a boring barnacle, probably belonging to Lithotrya. Herein named the Cape Burney sandstone, the distinctive unit on which the disconformity sits is assigned member status within the Tamala Limestone. Shell beds with a diversity of 35 species, dominated in volume by robust gastropods such as Turbo intercostalis and T. torquatus, thinly drape portions of the disconformity surface. Succeeding the shell drapes is a reef limestone with a maximum thickness of more than 2 m. The limestone is a massive accumulation of collapsed but otherwise mostly undisturbed coral fronds belonging primarily to a robust species of Acropora. Herein named the Bootenall limestone, this unit is assigned member status within the Tamala Limestone. Based on an analysis of electron spin resonance (ESR) from Acropora samples, the fringing reef developed between 120 ka and 132 ka, in the terminal stage of coastal transgression during the last interglacial period (Oxygen Isotope Substage 5e). □Ancient rocky shores, intertidal abrasion platform, hard-substrate colonization, reef succession.

Ecological forecasting on the likely impacts of climate warming is crucial at a time when several ecosystems seem to be responding to this environmental threat. Among the most important questions are: which are the most vulnerable organisms to climate warming and where are they? Recently, there has been debate on whether the tropics or temperate zones are more vulnerable to warming. Vulnerability toward higher temperatures will depend on the organisms' thermal limits and also on their acclimation capacity, which remains largely unknown for most species. The aim of the present work was to estimate (1) the upper thermal limits (Critical Thermal Maximum (CTMax)), (2) the warming tolerance (CTMax – Maximum Habitat Temperature) and (3) the acclimation capacity of tropical and temperate rocky shore organisms. Differences in biological groups (decapod crustaceans vs fish) were investigated and the effect of region (tropical vs temperate) and habitat (intertidal vs subtidal) was tested. Overall, 35 species were tested. For the assessment of the acclimation capacity, tropical-temperate pairs of closely related species of shrimp, crab and fish were selected. Warming tolerance was higher for temperate species than for tropical species and higher for subtidal species than for intertidal species, confirming that species with the highest thermal limits have the lowest warming tolerance. All species tested presented some accli-mation capacity (CTMax Trial − CTMax Control), with the exception of gobiid fish, which was not observed to acclimate. The tropical species tested showed a lower acclimation capacity than their temperate counterparts. Given that tropical rocky shore organisms are already living very close to their thermal limits and that their acclimation capacity is limited, it is likely that the impacts of global warming will be evident sooner in the tropics than in the temperate zone.

Increasing anthropogenic CO 2 emissions to the atmosphere are causing a rise in pCO 2 concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO 2 levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO 2 gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO 2 concentrations increased. CO 2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO 2 levels increased. The responses of benthic microalgae to rising anthropogenic CO 2 emissions are likely to have significant ecological ramifications for coastal systems.