Orientation of sandhoppers at different points along a dynamic shoreline in southern Tuscany

Orientation experiments were carried out on Talitrus saltator (Crustacea Amphipoda) at four points along 3 km on a dynamic sandy beach inside the Maremma Regional Park (Grosseto, Italy) to highlight behavioural variation related to distance from a river mouth, to erosion or accretion of shoreline, and to human trampling on the beach. Tests were performed using circular transparent Plexiglas arenas, contemporaneously at the four points. Replicates were made in 2 different months (September 2002 and May 2003), on 2–3 successive days, in the morning and afternoon. The distributions of the angles of orientation were compared for the different points and seasons, and multiple regression analysis was performed to test the effects of environmental and intrinsic variables on orientation. Sandhoppers showed the highest scatter at the eroded shoreline, intermediate scatter at the accreting beach most distant from the river mouth, and consistent orientation seaward at the least disturbed point. Orientation of sandhoppers was significantly affected by season, global radiation, time of day, distance from the river mouth, and human trampling. Sex and air humidity were of minor significance in the multiple regression model. The results, on the one hand, confirm plasticity in orientation of sandhoppers living on a dynamic shoreline, and on the other hand, show that variation in orientation could potentially be used as a bioindicator of shoreline changes.Communicated by R. Cattanevo-Vietti, Genova     

Indications of sodium,chloride, and water exchange across the gills of the striped dogfish Poroderma africanum

The ecology of a large sandy beach at Calangute, Goa, Central West India over a 22-month period is described from the point of view of changes in the distribution and abundance of the macrofauna, and of the physical environment of the beach; the dominant effect of the annual monsoon is clearly shown. The results from Calangute are compared with a nearby beach (Colva) and from earlier studies in Southern India. The biology of the dominant wedge-clam Donax incarnatus Gmelin is described, in particular its more rapid breeding-cycle and smaller size at Calangute, compared with other populations studied. The annual production of D. incarnatus has been calculated as 14.7 kcal/m²/year, and has been shown to be relatively low in comparison with other bivalve populations, due to high mortality and the extensive environmental disruption caused by the annual monsoon. It is suggested that the conditions at Calangute are most suitable for settlement, and that the small size of D. incarnatus here is related to the short life span of 6 to 7 months of all individuals.     

Tisular and population level responses to habitat harshness in sandy beaches: the reproductive strategy of <Emphasis Type="Italic">Donax hanleyanus</Emphasis>

Microscopic analysis and field sampling procedures were used to compare demographic and reproductive strategies of the intertidal wedge clam Donax hanleyanus (Bivalvia: Donacidae) in two exposed sandy beaches with contrasting morphodynamics (reflective vs. dissipative) during 13 consecutive months. Histological analysis showed that: (1) the reproductive cycle of D. hanleyanus was more extended in the dissipative beach, and this was true for all the three pre-active (beginning of gonadal activity), active (maturation) and spawning stages; and (2) males and females showed significantly smaller sizes at sexual maturity at the reflective beach. Even though successive increments in proportion and mature at size were observed, the sigmoid function was significantly steeper at the reflective Arachania for both sexes, suggesting an abrupt transition to maturity. Field sampling revealed a more extended recruitment period at the dissipative beach, where recruits were also significantly more abundant than at the reflective beach. These results give support for the habitat harshness hypothesis, which predicts that in intertidal species capable of sustaining populations across a wide spectrum of physical conditions, such as D. hanleyanus, abundance, recruitment, size at maturity and extent of reproductive and recruitment seasons increase from reflective to dissipative beaches. However, a recent hypothesis suggests that reflective beaches acting as sink populations were not sustained, because mature and spawning individuals of both sexes were found in the reflective beach throughout the study period. Thus, we suggest that post-settlement processes are critical in modulating population patterns for this bivalve.     

Recovery after trampling disturbance in a canopy-forming seaweed population

The recovery of Ascophyllum nodosum, and the associated benthic community, was followed after repeated trampling disturbance at different intensities, from 2005 to 2010, at its southern limit (41°41′27″N; 8°50′57″W). The cover of A. nodosum and associated organisms and the demography of A. nodosum individuals in the most disturbed areas were followed over a recovery period of 54 months. Recovery of A. nodosum assemblages was negatively affected by increasing trampling intensity. After 54 months, the highest intensity plots were still significantly different from control plots. Growth and mortality rates of A. nodosum increased shortly after disturbance but progressively recovered to levels close to control plots. The results of this study demonstrate the sensitivity of this habitat-building species to human trampling and also show its plasticity to cope with disturbance events.     

Carbon and nitrogen exchange between sandy beach clams (Donax serra) and kelp beds in the Benguela coastal upwelling region

Carbon consumption and nitrogen requirements were estimated for populations of the sandy beach bivalve Donax serra on nine beaches of the west coast of South Africa. Subtidal populations composed mainly of adult clams were responsible for the bulk of standing stock (3538 g C m⁻¹), annual carbon consumption (13 444 g C m⁻¹ yr⁻¹), faeces production (6478 g C m⁻¹ yr⁻¹ ) and nitrogen regeneration (2525 g N m⁻¹ yr⁻¹). Kelp detritus, bacteria and kelp consumers' faeces available in the water column surpass several times the carbon and nitrogen requirements of intertidal and subtidal clam populations. Individual Donax serra pop ulations, in turn, may regenerate up to 3.2% of the total nitrogen requirements of all primary producers from kelp beds and 14% of the requirements of phytoplankton. These high standing stocks of clams are presumably supported mainly by organic matter originating from kelp which, in contrast to phytoplankton, is in constant supply and comprises the largest proportion of the annual production of particulate organic matter on this coast. Wide and shallow continental shelves with gentle slopes probably limit the penetration of upwelled waters to the nearshore waters, decreasing the influence of external inputs and increasing the importance of internal flows of nutrients and carbon within the nearshore zone. In this context, sandy beaches, rocky shores and kelp beds may be more closely interlinked compartments of a larger ecosystem encompassing the whole nearshore than traditionally thought. Received: 28 August 1996 / Accepted: 7 October 1996     

Human trampling as short-term disturbance on intertidal mudflats: effects on macrofauna biodiversity and population dynamics of bivalves

The effect of physical disturbance in the form of trampling on the benthic environment of an intertidal mudflat was investigated. Intense trampling was created as unintended side-effect by benthic ecologists during field experiments in spring and summer 2005, when a mid-shore area of 25 × 25 m was visited twice per month by on average five researchers for a period of 8 months. At the putatively-impacted location (I) (25 × 25 m) and two nearby control locations (Cs) (25 × 25 m each), three sites (4 × 4 m) were randomly selected and at each site, three plots (50 × 50 cm) were sampled after 18 and 40 days from the end of the disturbance. Multivariate and univariate asymmetrical analyses tested for changes in the macrofaunal assemblage, biomass of microphytobenthos and various sediment properties (grain-size, water content, NH₄ and NO₃ concentrations in the pore water) between the two control locations (Cs) and the putatively-impacted location (I). There were no detectable changes in the sediment properties and microphytobenthos biomass, but variability at small scale was observed. Microphytobenthos and NH₄ were correlated at I to the number of footprints, as estimated by the percentage cover of physical depressions. This indicated that trampling could have an impact at small scales, but more investigation is needed. Trampling, instead, clearly modified the abundance and population dynamics of the clam Macoma balthica (L.) and the cockle Cerastoderma edule (L.). There was a negative impact on adults of both species, probably because footsteps directly killed or buried the animals, provoking asphyxia. Conversely, trampling indirectly enhanced recruitment rate of M. balthica, while small-sized C. edule did not react to the trampling. It was likely that small animals could recover more quickly because trampling occurred during the growing season and there was a continuous supply of larvae and juveniles. In addition, trampling might have weakened negative adult-juvenile interactions between adult cockles and juvenile M. balthica, thus facilitating the recruitment. Our findings indicated that human trampling is a relevant source of disturbance for the conservation and management of mudflats. During the growing season recovery can be fast, but in the long-term it might lead towards the dominance of M. balthica to the cost of C. edule, thereby affecting ecosystem functioning.     

The ecology of two sandy beaches in south west India. III. Observations on the population of Donax incarnatus and D. spiculum

The biology of two species of Donax, D. incarnatus Gmelin and D. spiculum Reeve on two beaches in south west India is described. Two year groups of D. incarnatus were present on both beaches, from settlements during the monsoon period in 1967 and 1968. At Shertallai, both groups were studied through the year, and data on growth, mortality and production are presented. At Cochin, the rate of growth was slower and the maximum size attained smaller, but mortality during the early monsoon precluded study of D. incarnatus through a full year. D. spiculum occurred at Cochin mainly during the pre-monsoon period, and at Shertallai during the post-monsoon. The species has a shorter life-span than D. incarnatus, but its irregular occurrence did not allow detailed production estimates.     

Donax trunculus and Venus verrucosa as bioindicators of trace metal concentrations in Mauritanian coastal waters

Trace-metal concentrations (Cd, Cu, Fe, Mn and Zn) were investigated in two species of abundant filter-feeding molluscs from Mauritania, the wedge shell Donax trunculus L. and the clam Venus verrucosa L. D. trunculus were collected on the beach of Nouakchott at low tide and V. verrucosa were sampled at the Banc d'Arguin at depths varying from 10 to 20 m, in mid-February 1987. D. trunculus contains significantly higher Fe and Zn concentrations than the clam. Total trace-metal content per individual (Y) in D. trunculus could be related to body weight (W) as the power function Y=aW ^b . The subsequent regression coefficient b was >1 for Cu, Fe, Mn and Zn and >1 for Cd. Metal concentrations in both species decreased in the order: Fe>Zn>Mn>Cu>Cd. Comparison of trace-metal concentrations in the small D. trunculus and the large V. verrucosa revealed lower contents in V. verrucosa, except for Cd. The trace-metal distribution in the various organs of V. verrucosa indicates that gills seem to concentrate metals, except Cu, to a greater degree than the other organs (visceral mass and remainder). The relatively elevated content of Fe in D. trunculus and of Cd, Fe and Zn in the gills of V. verrucosa seem to be of natural origin. In view of the scarcity of Mytilus sp. along the Mauritania coast, the molluscs D. trunculus and V. verrucosa are proposed as useful bioindicators of trace-metal concentrations.     

Video panorama assessment of beach landscape aesthetics on the coast of Wales

70 beaches in Wales, UK, were investigated with regard to the quality of beach scenery using video panoramas. Beaches were given a score from zero to 20 by a panel of 24 coastal managers (National Park and Heritage Coast Wardens, etc.) and 42 final year Degree or Master of Science students specializing in environmental sciences. Mean scores of coastal managers ranged from 16.1 (Broadhaven, S. Pembrokeshire; 80%) to 3.8 (Prestatyn, North Wales; 19%), while scores of students ranged from 16.0 (Barafundle, S. Pembrokeshire; 80%) to 6.1 (Trecco Bay, Porthcawl; 31%). Wave height, number of people present on the beach and position on the final videotape did not have significant effects on mean scores generated by either group. With both groups a strong preference was observed for undeveloped beaches over those where anthropogenic structures were prominent (p=0.00), but beach commercialization level had an independent effect only on scores from the student group (p=0.02). Cloud cover at time of filming had a significant effect (p=0.00) on scoring, so a correction was applied for final score calculation and ranking. The findings contribute to management of coastal aesthetic resources by providing a quantitative evaluation scheme. It is proposed to use these scores for beach scenery/aesthetic quality in a novel, comprehensive beach rating system.     

Effects of river sediment addition to the beach microbial communities

During the processes of claiming land from the sea, river sediments are used to fill and transform the sea area along the margin of islands and lands into new lands. These activities would probably affect microbial ecosystems of the beach sediment. However, little is known about these effects. In this study, a simulation test was conducted to evaluate these effects. Pyrosequencing technique was employed to assess the effects of river sediment addition to the beach bacterial communities. The used river sediments were collected from different rivers. The results indicated that river sediment addition greatly impacted microbial ecosystems of the beach and caused a clear shift in the beach bacterial community composition. These processes remarkably increased toxic metals and decreased the bacterial diversity in the beach sediment, mainly including the phyla of Bacteroidetes, Cyanobacteria, Proteobacteria, and Spirochaetes. River sediment addition caused an increase in potentially pathogenic bacterial genera of the beach sediment. Bacterial phylotype richness in the beach without river sediment addition was higher than that in the beach with river sediment input. There were significant differences in bacterial communities between beach sediments with and without river sediment addition, and the most dominant classes were Gammaproteobacteria and Flavobacteria.     

A preliminary account of two sandy beaches in South West India

Observations were made on 2 beaches during the premonsoon period (January to March) when conditions were relatively stable. The beach below the berm at Cochin is 14 m wide with a slope of 1 in 8.5, and at Shertallai 40 m wide with a slope of 1 in 16. The well-sorted sand has a mean particle size of 275 at Cochin and 175 at Shertallai. The amount of chlorophyll attached to sand grains is very small. Chlorophyll in the water varies between 0.9 and 13.0 g/l. Carbon in the sand amounts to 210 to 630 g/g, and in the water to 355 to 3660 g/l. Throughout observations, the water temperature remained about 31°C, but on the dry sand surface it reached 50°C. Fauna zonation on the 2 beaches is similar to that of other tropical beaches; crabs of the genus Ocypode and the isopod Eurydice sp. occur at high water mark, the polychaetes of the genera Glycera, Onuphis, Scoloplos and Lumbrinereis in the mid-intertidal region and below; the tidal migrants Bullia melanoides (Gastropoda), Donax incarnatus and D. spiculum (Bivalvia) and Emerita holthuisi (Crustacea) inhabit the wash zone of the surf. The average biomass is 0.73 g carbon/m² at Shertallai and 0.85 g C/m² at Cochin, where fewer species are present. This compares with a value of 0.63 g C/m² for a sandy beach on the west coast of Scotland.     

Compression of home ranges in ghost crabs on sandy beaches impacted by vehicle traffic

Animal movement is a pivotal element of many ecological processes, and on ocean-exposed sandy shores, ghost crabs (genus Ocypode) undertake extensive nocturnal forays on the beach surface. Because crab populations are also threatened by vehicle traffic, indicators that can detect sublethal effects before population declines are manifest are important. To this end, we tested on a barrier island in Eastern Australia whether movement patterns of crabs respond predictably to disturbance by vehicles; this was done by tracking (using the spool-and-line technique) crabs at night in beach sections open and closed to traffic. Beach traffic not only halved population densities of crabs on the unvegetated beach seawards of the dunes, but it also fundamentally changed crab behaviour and movement: individuals from beach areas rutted by tyre tracks travelled shorter distances in a more erratic zigzag pattern, and they had significantly compressed home ranges. Such behavioural changes linked to human pressures could be well suited as an early warning signal for wider negative ecological impacts (as demonstrated by reduced abundances). They also emphasize the need to incorporate sublethal effects into the assessment and management of ecological changes resulting from beach recreation.     

The relative significance of bacteria,meio- and macrofauna on an exposed sandy beach

A survey of the intertidal biota of a sandy beach on the west coast of South Africa has shown standing stocks of macrofauna, meiofauna and bacteria of 241.23, 200.17 and 663.07 g dry wt m^-1 of shoreline respectively, an approximate biomass ratio of 1:1:3. The distribution of the macrofauna was the reverse of the usual pattern, with highest biomass occurring at the level of the current driftline. This appears to be related directly to the ready availability of food in the form of drift algae. Peak meiofaunal numbers were also found below the driftline and it is proposed that meiofaunal distribution is governed by dissolved organic matter (DOM) levels in the interstitial environment. Bacteria were abundant up to 1.2 m below the sediment surface, with the highest concentrations occurring at low tidal levels. The significance of the various biotic components in the energetics of the sandy intertidal is discussed. Turnover estimates suggest that bacteria may account for about 87% of annual production, with meiofauna and macrofauna making up 10 and 3% respectively. Despite this overwhelming importance of bacteria, the macro-and meiofauna probably play a vital role in making small organic particles available to bacteria for mineralization and in optimising conditions for microbial growth.     

Burrowing behaviour inferred from feeding traces of the opheliid polychaete <Emphasis Type="Italic">Euzonus</Emphasis> sp. as response to beach morphodynamics

The distribution of the opheliid polychate Euzonus sp. and the orientation of its feeding traces were examined in a wave-dominated Pacific sandy beach of central Japan by periodical sampling from June to December 2006. This species occurred constantly within sediments at mid-intertidal level, although its horizontal distributions were variable depending on changes of the beach profiles. These facts indicate that Euzonus sp. moved horizontally seaward or landward within the substratum in response to the shifting beach face due to changes of wave conditions from the ocean. By analysing the orientation of feeding traces, the adaptive burrowing behaviour of this species in response to beach topographical changes was revealed: Euzonus worms burrowed horizontally to various directions in a relatively stable condition of beach topography, whereas they moved preferentially landward under a heavy erosion of the beach face by a storm. These findings indicate that the burrowing behaviour prevents Euzonus sp. from excessive burial and washing out due to the beach morphodynamics.     

Use of red algae as hosts by kelp-associated amphipods

To what extent densities of amphipods associated with red algae are related to food value or habitat form and architecture were investigated. Four epiphytic red algae common on kelp stipes (Laminaria hyperborea) were sampled, and the densities of three species of associated amphipods were analysed. The algae were chosen to represent different structures and levels of architectural complexity. Palmaria palmata and Delesseria sanguinea are leaf-shaped, and Ptilota gunneri and Polysiphonia elongata are branched. The algae were later fed to the common epiphyte-associated amphipods Ampithoe rubricata, Jassa falcata and Caprella septentrionalis in no-choice laboratory experiments. Survival and growth were measured. J. falcata was found at the highest densities on P. gunneri and D. sanguinea, C. septentrionalis was found in highest densities on P. elongata, and P. gunneri and A. rubricata were found at the highest densities on P. gunneri. The survival and growth were highest on P. palmata for all amphipods. This indicates that the form and function of the algal host is more important for the distributions of amphipods than the food value. Interspecific distribution differences between amphipods may have been related to differences in their body form and size, as well as to crypsis.Communicated by L. Hagerman, Helsingør     

Experimental evidence for the effects of the thalassinidean sandprawn <Emphasis Type="Italic">Callianassa kraussi</Emphasis> on macrobenthic communities

Bioturbation by thalassinidean sandprawns is known to structure soft-bottom communities, and field observations have suggested that the sandprawn Callianassa kraussi is a significant force influencing macrofaunal communities. To investigate causal relationships, a field experiment was undertaken in Durban Bay, South Africa, in which experimental cages were used to exclude or include C. kraussi and the abundance of macrofauna in these treatments documented. Cage effects were assessed by comparing macrofauna in inclusion cages with that of unmanipulated areas containing high densities of C. kraussi equivalent to those in inclusion cages. Measurements were made in 3 months, in March, June and September 2005. Total abundance and species richness of macrofauna were significantly greater in exclusion cages than in inclusion treatments during all sampling seasons, while diversity differed between these treatments in June and September only. Ordinations indicated that macrofaunal assemblages in exclusion cages differed statistically from inclusion and control treatments in all three sampling seasons. In general, the surface-grazing gastropod Nassarius kraussianus and suspension and deposit-feeding species such as the polychaetes Prionospio sexoculata and Desdemona ornata, cumaceans, and the bivalves Dosinia hepatica and Eumarcia paupercula were significantly more abundant in prawn-exclusion plots, implying that they are negatively affected by bioturbation by C. kraussi, whereas burrowing infauna were not affected.     

Diel variation in chlorophyll a,carbohydrate and protein content of the marine diatom Skeletonema costatum

Skeletonema costatum (Greville) Cleve isolated from Narragansett Bay, USA, was incubated at 3 light intensities (ca. 0.008, 0.040 and 0.075 ly min^-1) under a 12 h light: 12 h dark (12L:12D) photoperiod at 2°, 10° and 20°C. Cellular chlorophyll a increased at intensities less than ca. 0.040 ly min^-1; increases occured within one photoperiod at temperatures above 10°C. Cellular carbohydrate increased with light intensity at all temperatures; increases during the photophase were due to net production of the dilute acid-soluble fraction. Cellular protein increased during the photoperiod at 10° and 20°C; there was little difference in cellular protein among all cultures after one photoperiod. The rate at which cellular chlorophyll a increased in response to a decrease in light suggests that diel variation in cellular chlorophyll a is temperature-dependent in S. costatum. Protein: carbohydrate ratios ranged from ca. 0.5 to 2.0 over a diel cycle; ratios increased at lower intensities and higher temperatures. The diel range in protein:carbohydrate ratios equals that in cultures developing nitrogen deficiency; thus, use of this ratio as an index to phytoplankton physiological state must account for diel light effects.     

Factors regulating annual mating success and reproductive success in spotted sandpipers (Actitis macularia)

Summary We investigated factors affecting annual mating success (MS) and reproductive success (RS) of spotted sandpipers (Actitis macularia) from 13 years of a 17-year study at Little Pelican Island, Leech Lake, Minnesota. Analyses were restricted to ages 1–3. Mean annual female MS varied from 1.3 to 2.7 mates, and the MS pattern was indistinguishable from random. However, female MS increased with age and was affected by arrival date, territory size, and beach size. Female RS also increased with age, and number of mates and year effects were the most significant explanatory variables in each age. Older female RS was increased by priority on a territory and presence of a previous mate. Territory size and beach size varied with population density and did not predictably affect RS. The strong year affect on RS was associated with annual variation in sex ratio and predation. Males produce only one successful clutch per year, so MS greater than one is a result of nest loss and does not increase RS. Neither male MS nor RS changed with age. Male reproductive failure rate varied by year. Given that a male produced young, the degree of RS was affected by year, arrival date, priority on a territory, territory size, and beach size. In years with early-season predation, late arrivals had higher RS; territory and beach size effects varied by year. Neither the presence, nor degree, of female care was associated with male RS. Male RS was more subject to annual environmental variability than was female RS, probably because of relatively low annual potential RS among males.Offprint requests to: L.W. Oring at the current address     

Temporal and spatial distribution of three supralittoral amphipod species on a sandy beach of central Italy

The distribution of three talitrid species—Talitrus saltator (Montagu, 1808), Orchestia gammarella (Pallas, 1766), Platorchestia platensis (Kroyer, 1845)—in the beach-dune system at the mouth of the Mignone River (central Italy) was analysed. It was related to the variations of the following abiotic factors: temperature, penetrability, pH, conductivity and moisture of the sediment. The beach-dune system is influenced by human impact and natural erosion. All species showed a maximum capture frequency in November, while the abundance decreased to a minimum in July. T. saltator was dominant on the beach, the other two along the riverbank. Juveniles were abundant along the riverbank; they were most abundant in November and almost disappeared in summer. T. saltator was more abundant near the waterline during the hottest months and occupied the inner beach in winter, with occasional presences on the dune. Regression analysis between the abiotic factors and species abundance showed a positive relationship with pH and temperature for T. saltator, while O. gammarella was negatively related to pH. Canonical correspondence analysis (CCA) showed that penetrability, moisture and temperature had the greatest influence on the species. T. saltator was almost entirely confined to the beach transects and strongly associated with penetrability, temperature and pH values. O. gammarella was mostly associated with the riverbank and P. platensis only found there and on a nearby pool. The two species were mainly influenced by moisture and variations in grain sizes of the sediment.     

Inhibitory effects of red algal extracts on larval settlement of the barnacle Balanus improvisus

We examined the chemical antifouling properties of four sublittoral red algae, Chondrus crispus, Delesseria sanguinea, Osmundea ramosissima, and Polyides rotundus, which are all rarely fouled in the field. Two different approaches were used. Firstly, we tested the effects of lipophilic crude extracts on the settlement behaviour of cyprid larvae of the co-existing barnacle Balanus improvisus. Secondly, in a settlement preference experiment, we tested whether B. improvisus cyprid larvae settle on living algae when given a choice between natural algal surfaces and control surfaces. With this procedure, we were able to test both if the algae inhibit recruitment of cyprids, and if this inhibition is a result of chemistry. The settlement of B. improvisus larvae was strongly inhibited at concentrations estimated to be potentially ecologically relevant for all of the tested extracts. However, only C. crispus significantly inhibited settlement in the preference experiment, even though there was also a tendency for settlement inhibition on P. rotundus and O. ramosissima. In contrast, D. sanguinea seemed to stimulate settlement. This contradiction probably resulted from an extraction of metabolites that naturally occur only inside the alga. However, as this study shows, a combination of settlement assays with whole-cell extracts and preference tests of ecologically relevant fouling organisms on natural algal and control surfaces may be a useful procedure to avoid erroneous conclusions regarding natural antifouling roles of compounds based on settlement assays with only whole-cell extracts. Furthermore, this study also shows that production of inhibitory metabolites may explain the low degree of fouling, especially by B. improvisus, on C. crispus.Communicated by L. Hagerman, Helsingør