Zonation of the interstitial polychaeteStygocapitella subterranea (Stygocapitellidae) in European sandy beaches

The zonation ofStygocapitella subterranea Knoellner (Polychaeta, Stygocapitellidae) in sandy beaches is compared for several localities along the European coasts. In tidal beaches the species occupies a zone near average high tide level (AHTL), whereas in non-tidal beaches it is found at a fairly long distance from the water line. The regularities observed inS. subterranea indicate that the interstitial fauna may prove well suited for the establishment of a general scheme of zonation in sandy beaches analogous to that for rocky shores proposed byStephenson andStephenson (1949).     

Environmental stresses and intertidal assemblages on hard substrates in the port of Long Beach,California, USA

Nine intertidal stations within the Port of Long Beach, California, USA, were sampled during September and October 1975 using the random point method and the scraping technique. A total of 96,168 individuals belonging to 55 taxa were recorded in the quantitative survey; qualitative scrapings included 136 taxa. The protected outer coast intertidal assemblages were found at all but three stations along the shoreline. The shoreline, being situated in between the more environmentally stressed inner harbor and the less stressed open ocean, supported assemblages characterized by an instability in species composition. The upper midlittoral zone was typically dominated by Chthamalus dalli, C. fissus and Balanus glandula. The lower midlittoral was colonized either by Anthopleura elegantissima-Prionotis lanceolata facies along the outer breakwater or by A. elegantissima-Tetraclita squamosa rubescens facies along the inner breakwater. The mussel bed, which is the characteristic assemblage of the Californian lower midlittoral zone was obscured by the competitors P. lanceolata, T. squamosa rubescens and A. elegantissima, and was thinned out by predators, of which Pisaster ochraceus was the most voracious. Suspension feeders were dominant in the upper midlittoral and producers and grazers in the lower midlittoral. Predators were few in number and restricted to levels below mean lower low water. There was a gradual increase in numbers of intertidal species and individual abundance from level +5 ft (1.5 m) to level +1 ft (0.3 m) and from shoreline to outer breakwater. This may be attributable to the decrease in environmental stresses in the lower water levels and the improvement in water quality from the inner to outer harbor area.     

Ecology of sandy beaches in Oman

The benthic macrofauna and physical features of 10 sandy beaches along the coast of Oman were surveyed quantitatively. This is a mesotidal regime mostly subject to low to moderate wave energy but more exposed in the south. Five northern beaches are tide-dominated, with low wave energy, and their profiles consist of a berm, a steep, swash-dominated upper shore and a broad tide-dominated terrace from mid-shore downwards. They are composed of moderately sorted fine to medium sands. Southern beaches experience greater wave energy, particularly during the summer southwest monsoon, and exhibit smoother, concave profiles with fine, fairly well sorted carbonate sand. 58 species and species groups were recorded, with crustanceans, polychaetes and molluscs dominant. In general species richness was high, at least 19–25 species per beach, but dry biomass moderate to low at 26–90g/m shoreline, with one high value of 450g/m. Total abundance was moderate at 3–73×10³ organisms/m of beach. Some zonation was evident with ocypodid crabs andTylos in the supralittoral, cirolanid isopods on the upper shore and a variety of species on the lower shore. The coast of Oman appears to constitute a single zoogeographic region, but with some regional differentiation between north and south due to varying physical conditions. Thus, OmanÕs beaches are characterized by tide-dominated morphodynamics and exceptionally high species richness.     

Long-shore distribution of morphodynamic beach states along an apparently homogeneous coast in SW Spain

We present a morphodynamic study of an apparently homogeneous rectilinear coast in SW Spain. The study area covers 14 km of mesotidal sandy beaches, interrupted in some places by rocky-shore platforms. The method used consisted of a monthly monitoring of 12 beach profiles during two years. According to the results obtained from the study, which also include granulometric analyses andin situ determination of the beach disturbance depth, three main beach classes have been differentiated: low-reflective beaches, dissipative beaches and rocky-shore platform beaches. Their longitudinal distribution is not linked to their distance to the main source of sediments in the area (mouth of the river Guadalquivir). Instead, a very irregular long-shore variation of morphodynamic beach states appears. It is deduced that this long-shore variation is mainly linked to local contouring conditions (e.g. the presence of rocky shoals which affect wave-breaking processes), and not to the regional long-shore currents prevailing in the zone.     

Quantitative Untersuchungen zur Ökologie der Gastrotrichen in Gezeiten-Sandstrand der Insel Sylt

Quantitative investigations were made on the distribution of 21 species of Gastrotricha Macrodasyoidea and 2 species of Chaetonotoidea in 10 different tidal beach areas of the island Sylt (North Sea). Most species live in the upper few centimeters of sandy flats near the low tide level. We counted up to 989 Gastrotricha in 50 cm³ of sediment. This group comprises up to 24% of the total interstitial fauna in about 25 samples. The beach slopes are inhabited by different species which are much less abundant (up to 165 animals per 50 cm³ sediment, and up to 7% of the total interstitial fauna). Each species inhabits a distinct zone of the sand flat or the beach slope. These zones run parallel to the water line and follow one another in a characteristic succession from the sublittoral to the supralittoral. It is assumed that several factors, controlled by exposure — e.g. variations of temperature and salinity as well as oxygen avilability — are responsible for the distribution patterns observed.     

Hydrodynamic patterns in lotic intertidal sands and their bioclimatological implications

Water movement is probably the most important factor influencing life in the interstices of sandy beaches. In order to better understand this ecosystem, e.g. the distribution and migration of interstitial fauna and overall energy transfer, measurements of water flow through high energy beaches were made on the Atlantic coast of the USA. Special hot thermistor-probes and associated electronic circuits were built, capable of measuring water-flow velocity down to less than 10 m/sec. These were buried in the sand at various depths and locations in the intertidal zone and the flow velocity recorded continuously for one or more tidal cycles. In addition, an orientation sensor was constructed and used together with the flow probe so that a picture of the flow patterns in the intertidal zone of a beach and their changes during a tidal pattern could be developed and defined quantitatively.     

Comparative species composition and relative abundance of decapod crustaceans in marine habitats of Panamá

The community structure of the decapod crustacean fauna of 7 tropical, shallowwater, marine habitats (sandy beaches, mangrove swamps and rocky intertidal habitats on both the Pacific and Caribbean coasts of Panama, and Pocillopora damicornis coral habitat of the Bay of Panama) were examined and analyzed for species composition and relative abundances. Collections from the 7 habitats yielded 4361 individuals, representing 236 species. The number of species per habitat was (Pacific, Caribbean): sandy beach (16, 7); mangrove (20, 17); P. damicornis (53); rocky intertidal (78, 67). There were more species represented by more individuals in the Pacific habitats. An index of faunal similarity was calculated for each pair (Pacific-Caribbean) of habitats. This index is the number of ecologically similar congeneric species which occurred in both habitats expressed as a percentage of the total number of species present in the pair of habitats. For the sandy beach communities there were three Pacific species which were similar to three Caribbean species, a similarity of 6/23 or 26%. The index of similarity for the mangrove communities is 54% and for the rocky intertidal communities it is 37%. The P. damicornis community has affinities with the Pacific rocky intertidal community (18%), with that of the Caribbean rocky intertidal (16%) and with that of Indo-West Pacific pocilloporid corals (20%). A few specialized species dominated each of the communities. The habitats and the number of species accounting for over half of the individuals present are (Pacific, Caribbean): sandy beach (1, 1); mangrove (4, 4); P. damicornis (5); and rocky intertidal (3, 6). Most of the species in each community were represented by one or a few individuals.     

Activity rhythms of two cirolanid isopods from an exposed microtidal sandy beach in Uruguay

Activity rhythms of two cirolanid isopods, Excirolana armata and Excirolana braziliensis, were studied based on both seasonal field observations and laboratory experiments, at an exposed microtidal sandy beach in Uruguay. The natural emergence patterns of both species were observed in the field for 1 year, twice in each season, and correlated to sea level, expected tidal cycles and diel cycles. Laboratory experiments were carried out in order to detect endogenous rhythms of activity and observe how emergence of both species was affected by changes in light and/or sediment thixotropy. We also compared behavioral strategies of sympatric species that occupy different beach levels. Sea level (and thus swash zone position) during field sampling did not follow expected tidal cycles for most sampling occasions. E. armata was observed in activity most of the time, but activity only correlated with sea level on three out of eight occasions, and only once was correlated to expected tidal cycle. Laboratory results showed that emergence under constant conditions was rare; changes in sediment thixotropy stimulated emergence, but the response was not cyclical; light had little effect on this response. On the other hand, E. braziliensis was fairly scarce in the water column, but swimming individuals were observed always during the night. They displayed an endogenous circadian activity pattern in the laboratory which augmented in response to changes in sediment thixotropy. The natural light/dark cycle modulated both spontaneous and response emergence by increasing day/night differences in activity. In this study E. armata, a midlittoral species more exposed to sea level variations, seemed to rely entirely on different physical and/or biological cues to trigger emergence at the appropriate time. E. braziliensis, found mostly in the upper intertidal zone, emerged in a circadian rhythm, which was stimulated by changes in sediment thixotropy and reinforced by light cycles. The results of this study led us to conclude that on microtidal, unpredictable beaches, local physical and biological factors can combine to determine different activity strategies in organisms from different intertidal levels. Received: 23 March 2000 / Accepted: 30 August 2000     

Diel eclosion rhythm of a sublittoral population of the marine insect Pontomyia pacifica

Within the scope of studies on adaptation of insects to intertidal and sublittoral environments, correlations between the reproduction period of the short-lived chironomid Pontomyia pacifica Tokunaga and tidal conditions were examined at the only known Japanese location of this species in 1980. The larval habitat is situated, except for deeper tide pools in the lower midlittoral zone, mainly within the inner sublittoral zone, whose upper area is covered by Hypnea choroides, the dominating algae during the summer. The aerial adults emerge on the surface of the open sea and swarm there independent of the tidal situation above the submersed sublittoral habitat. Eclosion always started during dusk and all reproductive activities were ended within 2.5 h after sunset. The adaptation of P. pacifica (sublittoral habitat, diel eclosion after sunset with mass concentration of the adults on the water surface, no semilunar or lunar timing of the reproduction period and sinking egg masses) corresponds with those of the convergent marine chironomid Clunio balticus from Europe. On the basis of a few laboratory observations with P. pacifica and detailed experiments with C. balticus, it is supposed that the diel eclosion of P. pacifica is also controlled by an endogenous, circadian timing mechanism and the 24-h light-dark cycle as an environmental time cue.Communicated by O. Kinne, Oldendorf/Luhe     

Room to move? Threatened shorebird habitat in the path of sea level rise—dynamic beaches, multiple users, and mixed ownership: a case study from Rhode Island, USA

Accelerated sea level rise (slr) is expected to transform vulnerable Atlantic coastal habitats in the United States during this century. Low-elevation sandy beaches, important nesting habitat for the continued recovery of the federally threatened piping plover (Charadrius melodus) in Rhode Island, are especially vulnerable. These beaches, under a mix of private and public ownership, exist in a heterogeneous landscape of dunes, rocky headlands, salt ponds, and heavily developed areas. Understanding the extent to which piping plover nesting beaches can retreat landward under projected slr is important for prioritizing future conservation actions across multiple jurisdictions. This research examines habitat change in response to slr (0.5, 1.0, and 1.5 m) under stationary and migration beach responses and whether development blocks habitat migration for five productive piping plover nesting beaches. We found that under the stationary habitat model, all beaches lose area under all slr scenarios. For the habitat migration model, future habitat availability differs by beach depending on elevation, landward topography, and presence of development. However, across the majority of beach area, piping plover habitat will be able to migrate landward if unconstrained by future development. A coalition of public and private stakeholders already supports management efforts to help ensure plover population recovery in the area. With emerging habitat change prediction tools, these stakeholders and other partners can engage in innovative, local-level planning needed to protect wildlife habitat and commercial, residential, and infrastructure assets from sea level rise.     

Responses of fish assemblage structures to sandy beach types in Kyushu Island, southern Japan

To determine differences in fish assemblage structures between beach morphodynamic types on an exposed sandy shore, three beach types (reflective, intermediate, and dissipative) were sampled at Fukiagehama Beach, Kyushu Island, southern Japan, in May, August, and November 2006 and 2007. Distinct differences in physical conditions and the amount of major prey invertebrates, such as copepods, mysids, and amphipods, were recognized between the three beach types. The reflective beach was characterized mainly by turbulent swashes, coarse sediment, and a low abundance of major prey invertebrates. In contrast, the dissipative beach was characterized mostly by benign swashes, fine sediment, and a high abundance of prey invertebrates. The intermediate beach tended toward an intermediate condition between the reflective and dissipative beaches. The fish assemblage structures also differed clearly between the three beach types, with species and individual numbers being greatest on the dissipative beach and lowest on the reflective beach. A similarity index indicated differences in species composition of the assemblages between the beach types. Such differences arose primarily from the differential distributions of two dominant trophic groups, zooplankton (mostly copepods) and epibenthic crustacean (mainly mysids and amphipods) feeders, between the beach types, both groups tending to increase in species and individual numbers from the reflective beach to the dissipative beach. In addition, the mean standard length of all fish collected in each month tended to decrease toward the dissipative beach. These results suggested that beach types strongly influence sandy beach fish assemblage structures.     

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.     

Beach erosion and geochemical factors: Influence on spawning success of horseshoe crabs (Limulus polyphemus) in Delaware Bay

Horseshoe crab spawning activity is spatially patchy within the Delaware Estuary. This study investigated the importance of geochemical and erosional factors to the selection of breeding beaches. Two sandy beaches in Cape May county, New Jersey, USA, were studied; one beach had been subjected to considerable erosion, exposing underlying peat; the second beach, less than 1 km away, had only traces of peat. Reduced sediments with high levels of hydrogen sulfide were correlated with the presence of peat, and significantly fewer crabs utilized sediments in the proximity of peat beds for reproduction. The lower spawning activity on the beach in the vicinity of exposed peat, suggests that crabs may detect, at a distance, the nature of sediments and the quality of beach for spawning activity. Active salt marsh and peat-bank sediments dominate the upper bay shore; these sediments are unsuitable, or at best marginal, for horseshoe crab reproduction. Extensive bulkheading of eroding sandy beach along several New Jersey shore communities has further restricted the availability of suitable spawning habitat, making the remaining stretches of optimal sandy beach critical to the reproductive success of this species.     

A mathematical model of competition and colonization in a community of marine benthic algae

A mathematical model has been constructed for the algal community on the rocky shores of a Norwegian fjord. We report here on the studies of competition and colonization along a vertical transect from the upper intertidal to the sublittoral habiats. Results on species abundance and distribution (patterns of zonation) and time to reach maturity have been compared to observations both in the fjord area and in other rocky shore areas.Competition coefficients for the algae were inferred from plant morphology and shown to be in agreement with observations of algal abundance and their zone-forming ability. Competition restricts the distribution of the species, especially at the lower elevations, but does not alter their relative position. However, increasing uniform competition prolongs the time in which zone-forming can occur, and it also decreases the overall biomass which an area can sustain. Colonization by a single species may create transient stages in community development of the same order of magnitude as algae longevity, and probably also alters the zonation pattern to some degree.The simulation results indicate that the large-scale algal distribution pattern in the Hardangerfjord area results from global stability of the rocky shore community.     

Analysis of lipid components for determining the condition of anchovy larvae,Engraulis mordax

It has been presumed that intertidal spawning by Limulus polyphemus minimizes the loss of egges to subtidal predators; however, this strategy involves considerable risks. Massive beach strandings of adults accompany seasonal spawning migrations of crabs along Cape May in Delaware Bay, (USA). At least 190000 horseshoe crabs, approximating 10% of the adult population, died from beach stranding along the New Jersey shore of Delaware Bay during the 1986 (May to June) spawning season. Abnormalities of the telson (which is used in righting behavior) were significantly more common among stranded crabs than among individuals actively spawning on the intertidal beach. The number of stranded crabs per day was not correlated with tidal height or environmental variables (wind speed, wave height) which characterized the conditions at spawning. A complex suite of factors, including the size of the available spawning population, tidal and weather conditions, and beach slope, influence the number stranded during the breeding season. Horseshoe crab stranding results in a large loss of gravid females from the population, and may represent a major input of organic matter to intertidal sandy beaches in certain regions of Delaware Bay.     

Food availability and diet composition of three coexisting Mediterranean limpets (Patella spp.)

The gut contents of three intertidal patellid limpets were analysed by collecting foraging specimens on a breakwater on the Tyrrhenian coast (central Italy) between May 1988 and October 1989. The three species coexist there showing a different, but partially overlapping zonation: Patella aspera dominates the infralittoral fringe; the majority of P. caerulea inhabits the lower midlittoral, while P. rustica is most abundant in the upper midlittoral. The algae present on slivers of substratum over which each limpet collected was moving were identified. Moreover, floristic surveys were made along the shore in order to characterize the algal cover of the different zonal belts. The floristic study revealed that the basic elements of algal communities typical of western Mediterranean rocky shores are present in the study area. The algae found on the slivers under the foraging limpets were generally representative of the algal community typical of the same zone. There was a marked difference between the diets of P. rustica and P. aspera due to the fact that the first species forages on a few low lying epilithic and endolithic Cyanophyceae, while P. aspera feeds on a large number of species belonging to all the main algal classes and life forms considered, including frondose epilithics and epiphytics. The diet of P. caerulea resembles that of P. aspera in algal heterogeneity, but is dominated by Cyanophyceae as in P. rustica. A detailed analysis of the differences between gut contents of each limpet species and the relative slivers showed an obvious general correspondence, but revealed also that the diets of the three species do not completely reflect the availability of algae. These findings suggest that the basic diet segregation mechanism between the three populations is their zonal separation. However, the difference in gut contents of heterospecific limpets foraging in the same zone suggests the existence of supplementary morphy-functional or behavioural mechanisms for diet segregation between the three species.     

Intertidal slope of coral sand beach as a unique habitat for fish: meiobenthic diet of the transparent sand dart, <Emphasis Type="Italic">Kraemeria cunicularia</Emphasis> (Gobiidae)

Coral sand beaches harbor gobiid sand darts (genus Kraemeria), the only fish known to live in the sand throughout their adult life. Despite the uniqueness of sand-dwelling habitat as a vertebrate, the biology of this fish remains unclear. To explore how this unique fish utilize an unusual habitat, we investigated diurnal patterns of microhabitat use and prey consumption by the transparent sand dart, Kraemeria cunicularia, at a sandy beach on Iriomote Island, the Ryukyu Archipelago, Japan. Sand darts were found in sediment in the lower intertidal zone throughout the daytime regardless of changes in tidal level, whereas at nighttime these fish were found swimming. Gut content analyses revealed that the sand dart diet was dominated by harpacticoid copepods throughout the day. Analyses of meiobenthic distribution indicated that these copepods were most abundant at lower intertidal zones where highest numbers of sand darts were found during the daytime; thus, it is possible that microhabitat use of the fish is largely determined by food availability. An extensive distributional survey throughout the Ryukyu Archipelago further indicated that sand darts prefer sandy beaches with well-sorted, coarse sand. These results provide novel insights into how sand darts respond to the tidal rhythm and highlight putative key environmental factors that determine their distribution at both regional and microhabitat scales. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Microhabitat segregation of the amphipod genus Gammarus (Crustacea: Amphipoda) in the Northern Baltic Sea

Closely related species may occupy very similar niches but are often found to diverge by one or more traits when they share the same habitat. Five indigenous and sympatric Gammarus species are characteristic for the Baltic rocky littoral ecosystem. Yet, the species-specific distribution of these sympatric gammarids has not been well studied in the northern Baltic Sea. This study was undertaken to assess the spatial distribution of gammarid amphipods along wave exposure and depth gradients to study whether they show segregation in their microhabitat use. We sampled 12 rocky sublittoral shores along a wave exposure gradient over a period of 5 years. Samples differed with respect to depth and macroalgal type. Three of the five gammarid species occurred mainly in different depth zones and among different macroalgae at the exposed shores. In contrast, on protected shores, where algal zonation is weaker, a link to zonation and macroalgal type was almost absent. Moreover, the microhabitat use was strongest during the reproductive seasons of the species. The observed microhabitats of the three gammarid species fit well to their species-specific mean body sizes.     

Habitat harshness and morphodynamics: life history traits of the mole crab Emerita brasiliensis in Uruguayan sandy beaches

The habitat harshness hypothesis (HHH) postulates that in reflective beaches the harsh environment forces organisms to divert more energy towards maintenance and they therefore have lower abundance, fecundity, growth and survival rates than in dissipative beaches. Recent investigations have tested this hypothesis through single comparisons of only two beaches, and thus the observed trends in population level variables cannot be attributed incontestably to the beach state, but only to location. Here, abundance, reproduction, recruitment, population structure and body size of the intertidal mole crab Emerita brasiliensis were compared between populations from eight microtidal exposed sandy beaches with contrasting morphodynamics, sampled bimonthly during 22 months throughout the 180 km Uruguayan Atlantic coast. Physical variables and compound indices of the beach state were used to categorize sandy beaches. The results of this bi-annual large-scale analysis were fully consistent with the predictions of the HHH: abundance (total and population components), duration of the reproduction and recruitment seasons and the individual size of megalops and females of the mole crab E. brasiliensis decreased from dissipative to reflective beaches. This was reflected by linear or, mostly, nonlinear relationships between biological and both physical variables and compound indices of beach state. In conclusion, this multi-beach sampling provides compelling evidence of a consistent response of demographic and life history traits of an intertidal beach species to morphodynamic characteristics.     

Geographical patterns in reproductive biology of the Pan-American sandy beach isopod<Emphasis Type="Italic"> Excirolana braziliensis</Emphasis>

Eleven populations of the Pan-American sandy beach isopod Excirolana braziliensis, distributed from tropical (9°N) to temperate (39°S) sandy beaches in Atlantic and Pacific Oceans, were analyzed to determine latitudinal variations in: breeding and recruitment patterns, sex ratios, size of ovigerous females and of juveniles and length–fecundity relationships. E. braziliensis exhibited strong latitudinal patterns in all reproductive traits throughout its distribution range. Breeding and recruitment shifted from continuous to seasonal from tropical to temperate beaches, having a predominance of females at higher latitudes. In agreement with the latitudinal gradient hypothesis, ovigerous females inhabiting tropical sandy beaches (low latitudes) were smaller, became sexually mature at smaller sizes and had lower individual fecundity than on temperate beaches. Juveniles were also smallest at low latitudes. Between-ocean comparisons showed very similar reproductive characteristics for roughly the same latitude. These linked reproductive parameters suggest that the intensity of breeding effort is associated with the duration of the breeding season and geographically size-related characteristics of the species. Geographic variations in the breeding and recruitment seasons, as well as in individual fecundity, size structure of mature females and sex ratios, are proposed to have major consequences in explaining local variations in population demography. Our paper also reinforces the notion that sandy beach animals are highly plastic.Communicated by O. Kinne, Oldendorf/Luhe