Natural Rocky Shores Research Articles

Floating seaweed in the neustonic environment: A case study from Belgian coastal waters

Floating seaweeds form the most important natural component of all floating material found on the surface of oceans and seas. Notwithstanding the absence of natural rocky shores, ephemeral floating seaweed clumps are frequently encountered along the Belgian coast. From October 2002 to April 2003, seaweed samples and control samples (i.e. surface water samples from a seaweed-free area) were collected every other week. Multivariate analysis on neustonic macrofaunal abundances showed significant differences between seaweed and control samples in the fraction > 1 mm. Differences were less conspicuous in the 0.5–1 mm fraction. Seaweed samples were characterised by the presence of seaweed fauna e.g. Acari, Idotea baltica, Gammarus sp ., while control samples mainly contained Calanoida, Larvacea, Chaetognatha, and planktonic larvae of crustaceans and polychaetes. Seaweed samples (1 mm fraction) harboured considerably higher diversities (× 3), densities (× 18) and biomasses (× 49) compared to the surrounding water column (control samples). The impact of floating seaweeds on the neustonic environment was quantified by the calculation of the added values of seaweed samples considering biomass and density. These calculations resulted in mean added values of 311 ind m − 2 in density and 305 mg ADW m − 2 in biomass. The association degree per species was expressed as the mean percentage of individuals found in seaweed samples in proportion to the total density and biomass of that species (seaweed samples + control samples). Thirteen species showed an association percentage > 95%, and can therefore be considered members of the floating seaweed fauna.

Low-crested coastal defence structures as artificial habitats for marine life: Using ecological criteria in design

Coastal defence structures to protect sedimentary coastlines from erosion and flooding are increasingly common throughout Europe. They will become more widespread over the next 10–30 years in response to rising and stormier seas and accelerating economic development of the coastal zone. Building coastal defences results in the loss and fragmentation of sedimentary habitats and their replacement by artificial rocky habitats that become colonised by algae and marine animals. The engineering design and construction of these structures have received considerable attention. However, the ecological consequences of coastal defences have been less extensively investigated. Furthermore, due to their rapid proliferation, there is a growing need to understand the role of these man-made habitats in the coastal ecosystems in order to implement impact minimisation and/or mitigation measures. As part of the DELOS project, targeted studies were carried out throughout Europe to assess the ecological similarity of low-crested coastal defence structures (LCS) to natural rocky shores and to investigate the influence of LCS design features on the colonising marine epibiota. LCSs can be considered as a relatively poor surrogate of natural rocky shores. Epibiotic communities were qualitatively similar to those on natural rocky shores as both habitats are regulated by the same physical and biological factors. However, there were quantitative differences in the diversity and abundance of epibiota on artificial structures. Typically, epibiotic assemblages were less diverse than rocky shore communities. Also, LCSs offered less structurally complex habitats for colonisation and in some locations experienced higher disturbance than natural shores. We propose several criteria that can be integrated into the design and construction of LCSs to minimise ecological impacts and allow targeted management of diversity and natural living resources.

Extending the generality of ecological models to artificial floating habitats

Marine assemblages on natural hard substrata are generally different from those on artificial habitats. There is, however, the potential for certain ecological processes to operate on both types of structures. On the sides of floating pontoons in Sydney Harbour, there were strong patterns of vertical distribution of sessile epibiotic organisms and molluscan grazers across relatively small spatial scales (in three defined zones, namely splash, shallow and deep). Patterns of vertical distribution of the tubeworms Hydroides spp. were reversed depending on the cover of mussels. A manipulative experiment was done to test if patterns of vertical distribution of Hydroides spp. were due to (1) the functioning of mussels or (2) the structure provided by mussels. Neither the functioning nor structure of mussels accounted for the patterns of distribution of Hydroides spp. Mussels increased recruitment of Hydroides spp., in the shallow and deep zones, and this was not due to increased surface area of the mussel shells. Manipulation of numbers of grazers and covers of sessile epibiota showed that the observed negative relationship between grazers and epibiota was due to grazers reducing recruitment of epibiota and epibiota decreasing survival of grazers. Most importantly, processes that accounted for patterns of distribution of mobile and sessile organisms on artificial floating structures were similar to those repeatedly shown to create such patterns on natural rocky shores.

Assessing habitat use of the endangered marine mollusc Patella ferruginea (Gastropoda, Patellidae) in northern Africa: preliminary results and implications for conservation

The limpet Patella ferruginea Gmelin, 1791, endemic to the Mediterranean, is the most endangered marine species on the list of the European Council Directive 92/43/EEC on the Conservation of Natural Habitat of Wild Fauna and Flora (1992). Its Mediterranean range has progressively contracted to a few restricted areas and the species is now threatened with extinction. Seventeen stations were sampled along the littoral zone on the coast of Ceuta, North Africa, for quantifying environmental factors (water movement, siltation and suspended solids), and 70 transects were selected for P. ferruginea sampling. The study revealed the presence of a well-established population of P. ferruginea with values of density and size of 0.67 individuals m −1 ±0.96 and 48.94 mm±11.61 respectively (mean±standard error of mean). The biggest densities of P. ferruginea were found inside the harbour of Ceuta. The limpets were more abundant on artificial harbour stones than on natural rocky shores, and the areas under the highest human pressure were characterised by the lowest densities and the smallest specimens probably due mainly to the predation for food and fishing. Human pressure is probably the main contributing factor to the currently endangered status of P. ferruginea. Programmes of environmental education to avoid its collection for fishing, food or for fun as decorative objects should be conducted, and further experimental studies dealing with the reproductive biology of this species are needed to properly assess the future programmes of conservation.

Patterns of Variation in Levels of Hsp70 in Natural Rocky Shore Populations from Microscales to Mesoscales

An important step in connecting the organismal response to thermal stress to patterns of community structure is determining at what scale discernable levels of variation are manifested. The temperature signal to which organisms may potentially respond varies at many spatial scales including microhabitat, tidal height, site and latitude. A number of studies have taken physiological assessment of the heat shock response (HSR) into the intertidal both as a tool for examining the HSR in nature and for examining the utility of HSR molecules as population or community level indicators. Most commonly, immunodetection of the total pool of the Hsp70 family of isoforms is used. Here we present data on levels of Hsp70 in intertidal organisms from microhabitat to the mesoscale. Our data and previously published work show that Hsp70 levels vary at all scales examined, similar to other physical and biological variables of interest. This demonstrates both the potential utility of Hsp70 detection as a molecular tool for field biologists and to the care that must be taken in assessing scale of variation when looking for potential bioindicator molecules.

Grazing by two species of limpets on artificial reefs in the northwest Mediterranean.

The extensive presence of artificial reefs in marine coastal habitats demands a better understanding of the extent to which these structures can be considered surrogates of natural rocky shores for populations of plants and animals. The primary aim of this study was to test the hypothesis that removing limpets from the midlittoral of artificial breakwaters in the northwest Mediterranean led to changes in assemblages similar to those observed on rocky shores in the same area. Orthogonal combinations of the presence/absence of two species of limpets, P. aspera and P rustica, were produced using manual removals from June 1997 to February 1998. To test the hypothesis that the effects of limpets were variable at spatial scales comparable to those investigated on rocky shores, we repeated the experiment at two locations tens of kilometres apart, and on two reefs within each location a few kilometres apart. The results revealed strong and relatively consistent negative effects of limpets on filamentous algae, whereas interactions with other members of assemblages were complex and variable. Several taxa (Cyanophyta, encrusting and articulated coralline algae, Ralfsia and Rissoella) were abundant at one location but nearly absent at the other. This large-scale variability in patterns of distribution generated inconsistencies in the effects of limpets between locations. Within locations, several effects of P. aspera and P. rustica were observed, ranging from independent effects on some organisms, to additive or interactive effects on others. Apparently, the removal of filamentous algae by limpets resulted in positive indirect effects on Ralfsia and Rissoella. Collectively, these effects were comparable to those described for rocky shores in the northwest Mediterranean. The processes accounting for large-scale variation in grazing, however, appeared different between the natural and the artificial habitat.

State Coastal Program Effectiveness in Protecting Natural Beaches, Dunes, Bluffs, and Rocky Shores

This article reports on state coastal zone management (CZM) effectiveness in meeting the national goal of protecting natural shoreline resources. The research focuses on efforts to protect beaches, dunes, bluffs, and rocky shores. This study concludes that state CZM programs are effective overall in addressing the protection objective of the Coastal Zone Management Act of 1972 (CZMA). This conclusion recognizes that the CZMA requires states to balance competing needs and demands such as protection of natural resources from hazards and overdevelopment, promotion of recreational use, and respect for private property rights. Determination of CZM program effectiveness is based on process indicators and case examples. Outcome indicators were too sparse to allow an outcome effectiveness determination. All coastal states and territories use a wide variety of tools and processes to achieve resource protection, including regulatory, planning, state land management, acquisition, nonregulatory, and research tools. Regulatory tools are the most significant tools employed nationwide, because the majority of the oceanfront shoreline is in private ownership and is subject to significant shoreline change and development pressures. Over 60 significant upgrades to coastal management programs have been implemented over the years to protect natural shoreline resources. "Process indicators" of effectiveness show increased resource protection from CZM efforts. Of the 29 coastal states and territories studied, most (23) employ setbacks from the shoreline to provide a natural buffer between development and the water. All (27) but a few regulate shoreline activities to protect critical habitat and minimize adverse impacts on resources. All (28) but one regulate shoreline stabilizations to minimize adverse impacts on beach systems. Most (23) restrict pedestrian and vehicular access to channel human encroachment along boardwalks or dune crossovers, minimizing dune destabilization and impacts on fragile resources. All (28) but one use planning tools to designate and protect specific shoreline resources. Within state coastal parks, most (25) have designated natural protection areas and guided accessways. Many (21) have acquired additional coastal land holdings. Almost half use boardwalks or dune crossovers to protect dune vegetation and minimize adverse impacts on natural resources, and sand fencing and dune creation to restore the natural function of damaged dune systems. Over half (17) use beach nourishment to recreate eroding recreational beaches. Greater attention is needed to document on-theground results of CZM resource protection efforts through in-depth case studies and long-term monitoring of resource indicators of program success.