Ecological interactions in the provision of habitat by urban development: whelks and engineering by oysters on artificial seawalls

Abstract Increases in human population cause increased urbanization of most habitats, including the shoreline. This has many consequences for coastal environments, in particular the trend for artificial structures, such as seawalls, to replace natural habitats. Seawalls and natural shores support many of the common intertidal species, but others important on rocky shores are absent from or rare on many seawalls. The whelk Morula marginalba Blainville is an abundant and important predator on rocky shores of south‐eastern Australia, but is infrequently recorded on artificial substrata. In Sydney Harbour, where the Sydney rock oyster (Saccostrea glomerata Gould) was locally abundant, densities of M. marginalba on some seawalls appeared to be similar to those on rocky shores and to be larger than where there were few oysters. We sampled densities and sizes of whelks in four habitats, predicting and corroborating that: (i) on seawalls with many oysters, there would be more whelks than on seawalls with few oysters; (ii) where there are many oysters, densities of whelks would be similar on seawalls and rocky shores; and (iii) whelks would be larger where oysters were abundant. Growth and survival of whelks were measured to test hypotheses from the observed differences in size and density. Survival was greater in habitats with many oysters, which could explain differences in density, but size‐specific differences in survival could not explain differences in size among habitats. On seawalls but not on rocky shores, slower growth could explain the smaller size of whelks where there were few oysters. Seawalls provide important habitat for M. marginalba, but only via their indirect effects, mediated by oysters. These interactions cannot be predicted from those on natural rocky shores. Predicting how developed areas provide suitable habitat, either in management of conservation or in assessments of potential impacts clearly depends on understanding the roles of biogenic habitats.     

The effects of exposure and predation on the shell of two British winkles

Changes in shell size and shell shape of the two British winkles Littorina nigrolineata and L. rudis were studied in relation to exposure and to crab-size. In both species, shells from exposed shores are smaller and more globose than those from sheltered shores. Also, in rudis of exposed shores the mouth is relatively wider. In shores of equally sheltered conditions, shells are bigger at those localities where crabs are large than at those localities where they are small. The largest shells are found in those localities where it is extremely sheltered, and the crabs are very large.
It is argued that on exposed shores, small shells are favoured because they have more possibilities than large ones to shelter in crevices and in barnacle interspaces, from the impact of winds and waves. A globose shell could accommodate more foot muscle and thus enable a stronger adherence to the rock; and an increased mouth diameter would increase the area of foot adherence to the rock. On sheltered shores, on the other hand, large, narrow-mouthed shells are favoured because they discourage crab predation, large crabs being abundant mainly on sheltered shores.
The possible significance of shell size and shape in relation to zonation is discussed, in view of the different predatory and physical conditions which prevail in different zones of the shore, and the different shell specializations which these conditions would require.     

Detergents as tools for the purification and classification of lipid rafts

The relative insolubility of lipid rafts in cold non-ionic detergents is the most widely used method to purify these fascinating membrane domains from intact cells or membranes. Most of what we know about lipid raft function has been derived from experiments utilising detergent insolubility as the basis for raft purification. Recently, a wider range of detergents have been used to purify 'rafts', and rafts have been subclassified based on their differential solubility in different detergents. This minireview critically examines the use of detergents as tools for raft isolation and for the subclassification of rafts.     

Distribution and environmental synchronization of the marine insect, Halobates robustus, in the Galapagos islands.

The following three aspects of the biology of the marine insect Halobates robustus were studied, during a two week observation period, at several sites in the Galapagos Islands: distribution, aggregation behaviour and rhythmicity of locomotory activity. H. robustus occurred in highest numbers on the water surface at shores fringed with mangroves. The aggregations of H. robustus varied according to their location and density. Copulating adults formed dense, floating aggregations, which tended to be close to rocks or mangroves. Late instar nymphs were less aggregated and, in lagoons (where there was some shelter from direct tidal forces), were furthest from the shore. In two types of habitat (mangrove-fringed, sandy shores and rocky shores) the aggregations of H. robustus showed a pronounced ability to maintain a floating station in relation to the surrounding environment, irrespective of tidal movements (in one case at 34 m from the nearest fixed objects). Evidence of the ability of the aggregations to maintain station on the water surface was also obtained by comparing the movements of H. robustus with those of floating polystyrene particles, which move passively with wind and tide. Laboratory observations and experiments indicated no clear periodicity in locomotory movements throughout a 24 h period. However, the frequency of encounters between individuals showed two daily peaks, post-dawn and pre-dusk, with fewer encounters during the day and only occasional encounters during the night. By shifting the light-dark cycle it was demonstrated that the daily bimodal rhythm of encounters is triggered by dawn and, since it is not maintained in constant light or dark, an 'hour-glass' mechanism is suggested. The contributions of single adults, of copulating pairs and of immature stages to the overall pattern of activity were also determined. Immature stages did not affect the overall rate of encounters significantly and the interactions between single and copulating pairs of adults appear to have been responsible for the bimodal pattern.     

Predicting impacts of climate-induced range expansion: an experimental framework and a test involving key grazers on temperate rocky shores

Climate change has strong potential to modify the structure and functioning of ecosystems, but experimental field studies into its effects are rare. On rocky shores, grazing limpets strongly affect ecosystem structure and their distribution in NW Europe is changing in response to climate change. Three limpet species co-occur in SW Britain ( Patella vulgata, Patella ulyssiponensis and Patella depressa ) on open rock and in pools. Shores in Ireland are similar, but currently lack P. depressa . It is anticipated that P. depressa will expand its range into Ireland as the climate warms, but we currently lack an empirical basis to predict the consequences of this change. Recent studies show that increasing abundance of P. depressa on British shores has been accompanied by a decline of P. vulgata suggesting interspecific competition. In this study, a new experimental framework was used to examine the potential for P. depressa to affect P. vulgata on Irish shores. P. vulgata was experimentally transplanted into enclosures on open rock and in pools in both Ireland and Britain. In pools, treatments also included transplanted P. ulyssiponensis to mimic natural assemblages. Growth and mortality of P. vulgata were measured over 6 months with no differences between Ireland and Britain. In Britain, P. vulgata caged in pools with transplanted P. depressa and P. ulyssiponensis showed reduced growth, compared with when caged in pools with P. ulyssiponensis alone. There was no effect of P. depressa on the growth rate of P. vulgata on open rock. Results indicate that if the range of P. depressa extends into Ireland, it would reduce the growth of P. vulgata where it co-occurs with P. ulyssiponensis in pools. The framework used here provides a field-based approach that could be used to examine the impacts of climate-induced range expansions on the structure and functioning of other ecosystems.     

Deuterated detergents for structural and functional studies of membrane proteins: Properties,chemical synthesis and applications

Abstract

Detergents are amphiphilic compounds that have crucial roles in the extraction, purification and stabilization of integral membrane proteins and in experimental studies of their structure and function. One technique that is highly dependent on detergents for solubilization of membrane proteins is solution-state NMR spectroscopy, where detergent micelles often serve as the best membrane mimetic for achieving particle sizes that tumble fast enough to produce high-resolution and high-sensitivity spectra, although not necessarily the best mimetic for a biomembrane. For achieving the best quality NMR spectra, detergents with partial or complete deuteration can be used, which eliminate interfering proton signals coming from the detergent itself and also eliminate potential proton relaxation pathways and strong dipole-dipole interactions that contribute line broadening effects. Deuterated detergents have also been used to solubilize membrane proteins for other experimental techniques including small angle neutron scattering and single-crystal neutron diffraction and for studying membrane proteins immobilized on gold electrodes. This is a review of the properties, chemical synthesis and applications of detergents that are currently commercially available and/or that have been synthesized with partial or complete deuteration. Specifically, the detergents are sodium dodecyl sulphate (SDS), lauryldimethylamine-oxide (LDAO), n-octyl-β-D-glucoside (β-OG), n-dodecyl-β-D-maltoside (DDM) and fos-cholines including dodecylphosphocholine (DPC). The review also considers effects of deuteration, detergent screening and guidelines for detergent selection. Although deuterated detergents are relatively expensive and not always commercially available due to challenges associated with their chemical synthesis, they will continue to play important roles in structural and functional studies of membrane proteins, especially using solution-state NMR.     

The ecomechanics of mussel attachment: from molecules to ecosystems

One aspect of the physiological ecology of intertidal organismsis their mechanical design, which can be explored at many hierarchicallevels, from molecules to ecosystems. Mechanical structures,as with any other physiological feature, require energy to constructand maintain, are subject to manufacturing and evolutionaryconstraints, and influence ecological performance. This contributionfocuses on the ecomechanics of mussel attachment, which contributesto the competitive dominance of mussels on many wave-swept shores.Examples are presented to illustrate the hierarchical natureof mussel attachment, how levels of the hierarchy are interrelated,and where gaps in our knowledge remain. For example, water motiongenerates forces that mechanically deform byssal threads, butmay also enhance the rate at which threads subsequently restoretheir original toughness. Furthermore, the ability of musselsto sense and respond to changes in their flow environment byproducing a stronger attachment may be subject to physiologicalconstraints, which in turn may have important consequences forthe ecological response of mussels to shifts in wave climate.Thus an integrative approach to the study of byssal attachmentis needed to fully understand this important aspect of the physiologicalecology of mussels on rocky intertidal shores.     

Quantification of radular marks as a method for estimating grazing of intertidal gastropods on rocky shores

Wax discs have been used previously on intertidal rocky shores to record the grazing activity of gastropods. This study has evaluated this methodology for recording grazing of four common intertidal microalgal grazers on intertidal shores in New South Wales, Australia. In the laboratory, the four species examined-the patellid limpet, Cellana tramoserica (Sowerby), the trochid, Austrocochlea porcata (A. Adams), the neritid, Nerita atramentosa Reeve and the littorinid, Bembicium nanum (Lamarck)-made distinctive marks in the wax. These allowed identification of each species or combinations of species grazing over the different discs. Field experiments showed that the intensity of grazing, as indicated by the mean number of scratches per disc, was positively related to the number of gastropods in the surrounding area during low tide for C. tramoserica. The number of scratches per disc in any area was correlated with the percentage of discs scratched. The relationship for C. tramoserica was found at two scales-in sites (approximately 3x3 m) and also in plots (50x50 cm) within sites. Therefore, densities that were measured when these limpets were inactive during low tide provided good estimates of grazing activity during high tide. This is largely because these limpets do not move far between where they rest and where they feed. The amount of microalgal food in the vicinity was not correlated with density, nor with grazing intensity. No relationship between density and grazing intensity was found for N. atramentosa, although experiments were only done in the field at one spatial scale (in sites, 3x3 m). Results obtained in the laboratory and in the field show that wax discs are useful to distinguish grazing by different species of gastropods on Australian rocky shores and allow tests of hypotheses about grazing activity at different spatial scales.     

Dispersal mode and assessments of recovery on the shores of Gruinard,the ‘anthrax island’

Formaldehyde run-off was an unintended impact of the anthrax decontamination procedure on the island of Gruinard. The death of intertidal organisms was observed where formaldehyde reached the shore during 1986. The extent to which shores on Gruinard have recovered was assessed with survey work in 2000. Recovery estimates were based on the hypothesis that the process of recolonization is partly dependent on species’ dispersal capability. Underdevelopment of the assemblage of species lacking planktonic dispersal stages (direct developers) is therefore evidence that the process of recolonization is ongoing, rather than complete. A novel multivariate test showed that, when comparing quadrats from Gruinard and nearby mainland shores, assemblages of direct developing molluscs were significantly more distinct than assemblages of molluscs with planktonic dispersal stages. The average densities of species with direct development were generally lower on Gruinard than on mainland shores. While some species with direct development have similar densities on Gruinard and on the surrounding shores, the recovery of the overall assemblage was still incomplete after 14 years. In contrast, the harvested species, Littorina littorea, appeared to benefit from the absence of humans visiting Gruinard’s shores. Populations of L. littorea on Gruinard contained significantly higher proportions of large individuals. Depending on the dispersal capabilities of different species, Gruinard is either still in recovery or acts as a reserve.     

Some observations on shell shape variation in Pacific Nucella

This paper considers the patterns of shell shape variation shown by Nucella canalicuata, N. emarginata and N. lamellosa from two areas of the Pacific Northwest: the shores near Friday Harbour on San Juan Island and near Bamfield on the west coast of Vancouver Island. No clear pattern of variation in association with changes in exposure was seen in either N. canaliculata or N. lamellosa . It appears that genetic influences are more important controls of shell shape than environmental selection in both these species. Nucella emarginata shows the nearest approximation to the pattern shown by the Atlantic species, N. lapillus , but only at the exposed end of the wave-action gradient. On those shores, enclaves from the most surf-washed open coast headlands have shells with proportionally larger apertures (and thus a shorter, squatter form) than their equivalents in local shelter. But, unlike in N. lapillus , the trend does not continue onto genuinely sheltered shores. Under these circumstances the species is generally rare and, where enclaves do occur, their shells are of much the same shape (although of a much larger size) as in more exposed situations.     

Sympatric speciation as a by-product of ecological adaptation in the Galician Littorina saxatilis hybrid zone

On exposed rocky shores in northwestern Spain there is a strikingpolymorphism of Littorina saxatilis that has been claimed asan example of a putative sympatric ecological speciation process.Two ecotypes of this species have evolved that are adapted todifferent shore levels and habitats, although they meet andhybridize on the mid shore where their two habitats overlap.As a by-product of adaptation these ecotypes have evolved anincomplete premating reproductive isolation where they meeton the mid shore. Although they are not yet true species, andthe final outcome of the process cannot be predicted, the ecologicalmechanisms responsible for this polymorphism could cause sympatricspeciation in similar situations. Here, I review all data insupport of these claims and discuss the interest of such a modelsystem in microevolutionary studies. (Received 13 February 2006; accepted 25 October 2006)     

Spatial subsidies in spider diets vary with shoreline structure: Complementary evidence from molecular diet analysis and stable isotopes

Inflow of matter and organisms may strongly affect the local density and diversity of organisms. This effect is particularly evident on shores where organisms with aquatic larval stages enter the terrestrial food web. The identities of such trophic links are not easily estimated as spiders, a dominant group of shoreline predator, have external digestion. We compared trophic links and the prey diversity of spiders on different shore types along the Baltic Sea: on open shores and on shores with a reed belt bordering the water. A priori, we hypothesized that the physical structure of the shoreline reduces the flow between ecosystem and the subsidies across the sea–land interface. To circumvent the lack of morphologically detectable remains of spider prey, we used a combination of stable isotope and molecular gut content analyses. The two tools used for diet analysis revealed complementary information on spider diets. The stable isotope analysis indicated that spiders on open shores had a marine signal of carbon isotopes, while spiders on reedy shores had a terrestrial signal. The molecular analysis revealed a diverse array of dipteran and lepidopteran prey, where spiders on open and reedy shores shared a similar diet with a comparable proportion of chironomids, the larvae of which live in the marine system. Comparing the methods suggests that differences in isotope composition of the two spider groups occurred because of differences in the chironomid diets: as larvae, chironomids of reedy shores likely fed on terrestrial detritus and acquired a terrestrial isotope signature, while chironomids of open shores utilized an algal diet and acquired a marine isotope signature. Our results illustrate how different methods of diet reconstruction may shed light on complementary aspects of nutrient transfer. Overall, they reveal that reed belts can reduce connectivity between habitats, but also function as a source of food for predators.     

SPATIAL PATTERNS OF SHELL SHAPE OF THREE SPECIES OF CO-EXISTING LITTORINID SNAILS IN NEW SOUTH WALES, AUSTRALIA

The shape and relative weight of the shell have been shown tovary intraspecifically and interspecifically in a number ofspecies of gastropods, including many different littorinids.These differences give rise to different shell forms in differenthabitats. In those species which have non-planktotrophic development,differences in shell form among shores have been usually explainedin terms of natural selection because exposure to waves supposedlyfavours light shells with large apertures, while predation bycrabs on sheltered shores favours elongated, thick shells withsmaller apertures. Differences in shell shape among speciesfound at different heights on the shore have been explainedin terms of resistance to desiccation and temperature. Suchvariables would tend to act on a relatively broad-scale, i.e.causing differences among heights on a shore or among shores.Rates of growth, which might vary at much smaller scales withina shore, have also been shown to affect the shapes of many shells. In this study, the shape and relative weight of shells of threespecies of co-existing littorinids (Littorina unifasciata, Bembiciumnanum and Nodilittorina pyramidalis) were measured. These speciesall haveplanktotrophic development and they are found on manyshores where there is no evidence that they are preyed uponby crabs. Before explanations of shell shape are proposed, itis necessary that patterns of variation, within different partsof ashore and among different shores are clearly documented.These patterns were measured at a number of different spatialscales within and among replicate shores with different amountsof wave exposure. Large and small specimens were included toallow intraspecific comparisons among snails of different sizesfound at different heights on the shore. The results showedsignificant differences among shores in shape and relative weightof shells, but these differences could not be explained by exposureto waves. In addition, snails of different sizes and differentspecies did not show the same patterns although they were collectedfrom the same sites. Importantly, the shell shape of Liuorinaunifasciata varied significantly among sites at approximatelythe same height within a shore. These differences could notbe clearly correlated with density, mean size nor exposure towaves. The only consistent pattern was a decrease in relativeaperture size in specimens living higher on the shore. Modelsthat have commonly been proposed to explain shape and relativeweight of shells in other species of gastropods are not adequateto explain the small- and large-scale variation of the measurementsdescribed here. It is proposed that any selective advantageof shell morphology and the effects of any variables on thedevelopment of shell morphology in these species can only beidentified after appropriately designed and replicated fieldexperiments. (Received 4 March 1994; accepted 13 September 1994)     

Are the opposing selection pressures on exposed and protected shores sufficient to maintain genetic differentiation between gastropod populations with high intermigration rates?

Throughout the world intertidal gastropods living on exposed rocky shores differ strikingly in a number of morphological and life history traits from those on protected shores. Where surf is heavy gastropods tend to be smaller and to have thinner and smoother shells with larger apertures than do those from sheltered areas where crab predation is more intense. These morphological differences can occur within a species and there is evidence that they can be partially genetic and partially environmental. In addition the convergence of shell features in each habitat suggests that there are consistent differences between the selective pressures on exposed shores and the selective pressures on protected shores. I constructed a simulation model for a polygenic trait that experiences different selective pressures on exposed and sheltered shores. The results show that genetic differences can be maintained between the two populations despite high intermigration rates. Replacement of a portion of the random environmental variance with adaptive environmental variance reduces the effect of selection and thus the size of the difference maintained between the two populations. Genetic differentiation between exposed and protected populations can persist for significant periods of time and may have sometimes been the first step in speciation.     

HAS THE POPULATION DECLINE DUE TO TBT POLLUTION AFFECTED SHELL-SHAPE VARIATION IN THE DOG-WHELK, NUCELLA LAPILLUS (L.)?

The number of dog-whelks on sheltered rocky shores of southernBritain has greatly declined during the last twenty years, followingthe use of TBT antifouling paints on the hulls of yachts andother small craft. In July 1988, dogwhelks were apparently absentfrom some sites around Dale Roads (Milford Haven: South Wales)where, formerly, they had been common. But, where animals couldbe found, there had been no detectable changes in mean shellshape since 1966/1971. That is, the survivors appear to representa random selection of the shell shapes shown by the former largepopulations. In a smaller inlet. Water-mouth Cove (N. Devon),the true sheltered shore form was apparently extinct: all thesurvivors, living on shores of intermediate exposure in theentrance to the cove, have less elongated shells. It will beinteresting to monitor the recolonisation process. (Received 5 October 1988; accepted 18 October 1988)     

Novel characteristics of a 33KDa protein (pp33) rapidly phosphorylated in IL3 dependent cells by stimulation with IL3

We report the novel properties of a 33 KDa cellular protein rapidly phosphorylated by stimulation of growth by IL3 in IL3 dependent lines. Although pp33 is readily soluble in SDS, SDS-solubilised pp33 is insoluble in non-ionic detergents and is excluded from electrophoretic analysis (IEF, NEPHGE) employing such detergents. Native pp33 is not extracted by non-ionic detergents with or without cation chelation. pp33 is concentrated in a cell fraction containing endoplasmic reticulum where it is associated with a specific trypsin-sensitive degredative enzyme, active at 4 degrees. Its unusual characteristics and kinetics of phosphorylation suggest pp33 may be a novel molecule, explain its absence in studies elsewhere where non-ionic detergent extraction has been exclusively used and suggest it is intimately related to the signal transduced by IL3.     

Status of the Nile crocodile in the Sahara desert

Middle Holocene remains and rock paintings show that the Nile crocodile (Crocodylus niloticus Laurenti) used to occur across the whole Sahara. It also occurred at the South Mediterranean shores, in swamps and rivers and it may even have been circum-mediterranean. Until the beginning of this century, many permanent waters in the Sahara still housed relict populations. Nowadays, only few specimens survive in pools in few river canyons of the Ennedi plateau (N. Chad), where they are threatened with extinction. Another relict population, in the Tagant hills of Mauretania, was found to be probably extinct in 1996.     

Destabilization of collagen structure by amides and detergents in solution

The effects of amides and detergents on collagen to gelatin transition have been studied at neutral pH. Simple amides denature the protein. The substitution of H-atoms by the alkyl groups at the nonpolar end of amide increases the effectiveness of the compounds in destabilizing the collagen structure whereas substitution of the H-atom at the polar amide end shows marginal effects on the collagen transition. The capabilities of these reagents to denature collagen are much less pronounced than their effects on denaturing globular proteins. Anionic detergents are found to destabilize collagen at very low concentrations (below their cmc values). In this respect, the effects of the detergents on collagen are comparable to the denaturing effects of the detergents on globular proteins. The effect of detergents increases with the increase in the length of the alkyl chain. The structure of the anion in the detergent is also important as seen from the lower potency of the sulfonate containing detergent compared to the sulfate containing detergent in denaturing collagen. Cationic and nonionic detergents do not denature collagen.     

Engineering novel habitats on urban infrastructure to increase intertidal biodiversity

Urbanization replaces natural shorelines with built infrastructure, seriously impacting species living on these “new” shores. Understanding the ecology of developed shorelines and reducing the consequences of urban development to fauna and flora cannot advance by simply documenting changes to diversity. It needs a robust experimental programme to develop ways in which biodiversity can be sustained in urbanized environments. There have, however, been few such experiments despite wholesale changes to shorelines in urbanized areas. Seawalls––the most extensive artificial infrastructure––are generally featureless, vertical habitats that support reduced levels of local biodiversity. Here, a mimic of an important habitat on natural rocky shores (rock-pools) was experimentally added to a seawall and its impact on diversity assessed. The mimics created shaded vertical substratum and pools that retained water during low tide. These novel habitats increased diversity of foliose algae and sessile and mobile animals, especially higher on the shore. Many species that are generally confined to lowshore levels, expanded their distribution over a greater tidal range. In fact, there were more species in the constructed pools than in natural pools of similar size on nearby shores. There was less effect on the abundances of mobile animals, which may be due to the limited time available for recruitment, or because these structures did not provide appropriate habitat. With increasing anthropogenic intrusion into natural areas and concomitant loss of species, it is essential to learn how to build urban infrastructure that can maintain or enhance biodiversity while meeting societal and engineering criteria. Success requires melding engineering skills and ecological understanding. This paper demonstrates one cost-effective way of addressing this important issue for urban infrastructure affecting nearshore habitats. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Improvements in the application of the 4,4-N,N-dimethylaminoazobenzene-4'-isothiocyanate micromethod to the sequence analysis of proteins

Different experimental conditions have been tested to improve the sequence determination of peptides and proteins by the DABITC (4,4-N,N-dimethylaminoazobenzene-4'-isothiocyanate) method and to facilitate automation in the analysis of the released 4,4-N,N-dimethylaminoazobenzene-4'-thiohydantoin derivatives (DABTHs). Conditions for a complete and rapid separation of all amino acid derivatives have been optimized by using different reversed-phase columns. The stability of the DABTHs in several water-organic solvent mixtures was determined by quantitative analysis and permitted the selection of the appropriate solvents for use in autosamplers. Also the amino acid side-products specific to individual residues which may be observed during thin-layer chromatography of DABTHs can be completely resolved by HPLC and are helpful for a safe assignment of the amino acid residues. The analytical procedures developed have been used to examine the influence of oxygen and detergents on the efficiency of the application of the DABITC manual micromethod on proteins. In the presence of oxygen the recovery of DABTHs is lower in most cases than when the operation is carried out in an inert atmosphere. The presence of a limited amount of detergents does not interfere in the HPLC analysis of DABTHs and, moreover, can increase the efficiency of the sequence analysis of proteins depending on their nature and concentration. In particular, it has been observed that sodium dodecyl sulfate at a concentration of 0.1% can in some cases produce a threefold increase in the recovery of DABTHs.