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.     

A very unusual ‘groin’, the MV River Princess,Goa, India and its impacts upon tourism

On June 6, 2000, the Merchant Vessel River Princess – dead weight 114,645 tonnes and 261 m in length, grounded on the beach off the Candolim-Sinquerim coast, Goa, India, spilling some 40 tonnes of oil. In the past 10 years it has settled some 10 m into the sea bed and taken in circa 40,000 tonnes of sand. Until the ‘60’s the Goan economy centered on agriculture and fishing with very low key recreation. Over the last three decades it has become heavily reliant upon recreation, with 13 % of GDP arising from this sector. Nine million cubic metres of littoral drift occurs off this beach per annum, with the longshore current broken by rips into a series of circulating cells. The vessel acts as a massive groin so much so that downdrift, erosion of approximately 5 to 10 m/annum (dependent on the monsoon strength) is occurring at the Taj hotel site. Satellite imagery has shown that some 0.13 km² beach loss has occurred since 2001. Downdrift, the beach is circa 20 m wide compared to updrift areas where it exceeds 100 m. Embryo tombola growth has now commenced between shore and ship. In addition to this, the dune system is now seriously out of equilibrium and sand bags, geotextiles etc. are currently in use to combat dune foot erosion. Questionnaires (n?=?111) showed that 37 % of beach users ranked erosion as the top coastal problem. Sixty seven percent of beach users rated scenery as the most important quality of a beach and due to the grounded ship, >60 % rated the scenery as below average, as well as viewing the ship as a source of danger for swimming purposes.     

The ecology of two sandy beaches in south west India. II. Notes on Emerita holthuisi

The mole crab Emerita holthuisi Sankolli occurred on two beaches, at Shertallai and at Cochin, in southwest India. Observations on the size-frequency of samples for Shertallai suggest that there were two main periods of recruitment, one in the pre-monsoon,months of February and March, and one during the monsoon, although there may have been some recruitment throught the year. At Cochin, E. holthuisi was present in the pre-monsoon period, but disappeared from the beach during the monsoon.     

A natural history study of Encope grandis and Mellita grantii,two sand dollars in the northern gulf of California,Mexico

Populations of the sand dollars Encope grandis and Mellita grantii were studied at Playa Hermosa in the northern Gulf of California, Mexico. Intertidal distribution and abundance were estimated for the two species from 1969 to 1972. They occurred in the lower intertidal (-0.4 to -1.3 m) and on into the subtidal. Density of E. grandis varied from a high of 380/m² in the spring of 1970 to a low of 0.1/m² in the fall of 1971. Density of M. grantii ranged from a high of 56/m² in 1970 to a low of 0.8/m² in 1971. Growth curves were constructed based on shifts in the modes of the size distributions, and rates of mortality were estimated from the growth parameters and size distributions. It is estimated that E. grandis would attain 95% of its maximum size (74 mm) in about 6 years with an annual mortality rate of 18%. M. grantii would reach 95% of its maximum size (38 mm) in about 5 years with an annual mortality rate of 58%. The populations of these sand dollars appear to be limited by the physical environment.     

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.     

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.     

The ecology of two sandy beaches in south west India. I. Seasonal changes in physical and chemical factors,and in the macrofauna

Changes during one year in the fauna of two beaches in south India are described in relation to the nutrient content of the water and sand, and the physical changes brought about by the south-west monsoon. At both beaches, the most stable conditions were reached in the pre-monsoon months when the greatest number of species occurred and when there was marked zonation. During the monsoon, erosion took place and only actively migrating species remained to form a permanent element of the beach fauna. Data on population density and biomass indicate markedly seasonal recruitment and rapid growth of individual species, most of which are suspension feeders.     

Seasonal changes in biomass,growth rates and production of subantarctic calanoid copepods in the Bay of Morbihan,Kerguelen Islands

The present study addresses the ecology of two dominant copepod species in the Bay of Morbihan, Kerguelen Archipelago. The biomass of the herbivore Drepanopus pectinatus (from 2 mg m^?3 in winter up to 500 mg m^?3 in summer) is tightly coupled to seasonal changes in chlorophyll a concentration in the region, whereas the biomass of the predatory euchaetiid Paraeuchaeta antarctica increases during two distinct periods over the year: 250 mg m^?3 in early summer, with the recruitment of the annual generation, and 100 mg m^?3 in autumn, with the deposition of lipids as energy reserves in C5 stages and adults. The juvenile growth rates predicted by temperature-dependent models (0.09 day^?1) closely approximate those observed in D. pectinatusin summer, but are much greater than those observed in P. antarctica (from 0.001 to 0.04 day^?1 depending on developmental stages). This difference can be explained by the reproductive strategies and trophic positions of the two species and may also result from the dependence of larval growth on energy reserves in P. antarctica. The production rates are five- and tenfold greater in juvenile stages than in adults, respectively, for D. pectinatus and P. antarctica. The secondary production by D. pectinatusis insufficient to support P. antarcticaduring winter, when the predatory species probably shifts to alternate prey. In summer the predation by P. antarctica accounts for only a minor part of the mortality estimated for D. pectinatus (from 20% to 60% depending on the examined station). At two of the three stations examined in the Bay of Morbihan, the production of P. antarctica could potentially support the dietary requirements of planktivorous seabirds in the region (~2,000 kg prey day^?1 for common diving petrels, Pelecanoides urinatrix, and ~90 kg prey day^?1 for rockhopper penguins, Eudyptes chysocome filholi).     

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.     

Processing of allochthonous macrophyte subsidies by sandy beach consumers: estimates of feeding rates and impacts on food resources

Allochthonous subsidies of organic material can profoundly influence population and community structure; however, the role of consumers in the processing of these inputs is less understood but may be closely linked to community and ecosystem function. Inputs of drift macrophytes subsidize sandy beach communities and food webs in many regions. We estimated feeding rates of dominant sandy beach consumers, the talitrid amphipods (Megalorchestia corniculata, in southern California, USA, and Talitrus saltator, in southern Galicia, Spain), and their impacts on drift macrophyte subsidies in field and laboratory experiments. Feeding rate varied with macrophyte type and, for T. saltator, air temperature. Size-specific feeding rates of talitrid amphipods were greatest on brown macroalgae (Macrocystis, Egregia, Saccorhiza and Fucus). Rates for large individuals of both species ranged from ∼40 mg wet wt individual⁻¹12 h⁻¹ on brown macroalgae to negligible feeding by M. corniculata on a vascular plant (surfgrass). Amphipod growth rates were also greatest on Macrocystis and lowest on surfgrass, Phyllospadix. For a Californian beach with substantial inputs of macrophyte wrack (>70 kg wet wt m⁻¹ month⁻¹ in summer), we estimated that the population of talitrid amphipods could process an average of 55% of the palatable Macrocystis input. Our results indicate that talitrid amphipod populations can have a significant impact on drift macrophyte processing and fate and that the quantity and composition of drift macrophytes could, in turn, limit populations of beach consumers.     

Long-term trend in substratum occupation by a clonal, carbonate bryozoan in a temperate rocky reef in times of thermal anomalies

Studies over time provide opportunities to detect variations in the spatial and temporal patterns of clonal organisms and measure changes on their population dynamics related to extreme events. We assessed population dynamics for a bryozoan species dominating a subtidal rocky reef at Tino Island, in the eastern Ligurian Sea (NW Mediterranean). Using 9 years of annual photosurveys (1997–2005), rapid decline in Pentapora fascialis colony cover was shown at 11 and 22 m depths following the anomalous warming events in 1999 and 2003. An 86 % reduction in live colony portion was found after the 1999 warming event (2.3 °C higher than normal), with larger colonies being most affected. Effects from the 2003 event were delayed, and gradual cover decline occurred during the following 2 years. At the “Shallow” photostations, none of the larger colonies (>1,000 cm²) survived after the first cover decline. Availability of new substrate after the 1999 disturbance resulted in enhanced recovery through new colony production. At the “Deep” photostations, the population structure did not change over the duration of the monitoring period showing the same monomodal structure and same dominant size class (50–500 cm²). In the 4 years following the first cover decline, the deeper population regained colony cover to levels similar to pre-disturbance level, showing a good resilience. This 9-year monitoring analysis provided the temporal resolution needed to detect changes occurring in the P. fascialis population and will contribute to the assessment of long-term changes on benthic populations suffering during recent decades from dramatic increases in extreme events.     

Age-structure, recruitment, and adult mortality in populations of the Atlantic surfclam, Spisula solidissima, from 1978 to 1997

The Atlantic surfclam, Spisula solidissima (Dillwyn, 1817), is a dominant member of the benthic community on the continental shelf from Georges Bank to North Carolina, USA. This bivalve has supported a major fishery, primarily off New Jersey and the Delmarva Peninsula, since the 1960s. Early papers documented that these populations were at historical lows in the mid-1970s owing to commercial harvesting and a hypoxic event off New Jersey. It was also shown that major recruitment took place off New Jersey in 1976 and off the Delmarva Peninsula in 1977. Because the size frequencies of surfclams from federal surveys do not show distinct year classes, there has been uncertainty about the number of year classes in these populations throughout the 1980s and 1990s. The present study describes changes in population age- and size-structure from 1978 to 1997 in federal waters (≥5.5 km from shore) of the USA. Given the 30 to 35 year life span of S. solidissima, these populations could be composed of many year classes. Yet, these populations were composed of only two to three year classes in 1978. Through annual recruitment, the number of year classes increased over time, and populations off New Jersey and the Delmarva Peninsula contained at least 19 year classes in 1997. This major change in population structure over time was not evident from examination of available size-frequency data, and could only be inferred from data on age-composition. Throughout the 1980s and 1990s, the surfclam fishery was supported by multiple year classes. The mean and variance of recruitment to the New Jersey region, as indicated by the abundance of 4-year-olds over time, was greater than that off Delmarva, particularly between 1980 and 1986. The instantaneous rate of adult mortality, which includes the effect of harvesting, was approximately 0.26 yr⁻¹ in each region. Received: 11 September 1998 / Accepted: 1 February 1999     

Pesticide Residues in Water From River Kaveri,South India

The residue levels of presistent chlorinated pesticides such as HCH (hexachlorocyclo-hexane) isomers and DDT (dichlorodiphenyl trichloroethane) compounds were quantified in water samples collected from the River Kaveri and its distributor River Coleroon in Tamil Nadu, South India. HCH showed higher levels in River Kaveri during premonsoon (July to September) and monsoon (October to December) months, reflecting the HCH usage during that season for paddy crops. But in the case of DDT no clear trend in residue level was observed. the α-HCH was detected as the dominant isomer in all the three sampling sites. Among DDT compounds, p,p'-DDT and p,p'-DDE showed higher percentage of the total. International comparison of residue levels revealed that the present values are comparable to the waters from Asian and South East Asian nations, but lower than some samples from other parts of India. the value of DDT is well below the EEC's maximum acceptable concentration for surface waters and lower than the recommended limit of 2000ng 1^-1 in USA water for protection of aquatic life (Water Quality Criteria, 1972).     

Growth,production and biomass of the burrowing protobranch mollusc Yoldia limatula in the Bideford River,Prince Edward Island,Canada

Samples of the population of Yoldia limatula Say were obtained from the Bideford River, Malpeque Bay, Prince Edward Island, Canada, during the summers of 1979 and 1980 by means of a dredge and a Ponar grab sampler. Size frequency analysis demonstrated that individuals in the size range 25- to 35-mm shell length were numerically dominant in May, June and July. Recruitment of juveniles in August resulted in the dominance of individuals of 5 mm and smaller which comprised 50% of the population at that time. The overall sex ratio was 48.8% males to 51.2% females. From annual lengths measured at successive winter growth bands it was determined that one-yr olds attained a shell length of between 13.8 and 17.7 mm, two-yr olds between 26.7 and 28.0 mm, three-yr olds between 33.8 and 35.2 mm, and foru-yr olds had a mean length of 38.7 mm. Y. limatula produced a croppable annual yield of between 1.19 and 2.65 g dry tissue weight m^-2 with P/B ratios of 0.65 and 1.45 respectively.     

Evolution of a beach nourishment project using dredged sand from navigation channel,Dunkirk, northern France

The largest beach replenishment project ever in France was completed in February 2014 in Dunkirk on the coast of northern France. A volume of 1.5 × 10⁶ m³ of sand extracted from a navigation channel was placed on the beach to build up a 150 to 300 m wide supratidal platform in front of a dike, called « Digue des Alliés », which protects several residential districts of Dunkirk from marine flooding. High resolution topographic surveys were carried out during 2½ years to monitor beach morphological changes, completed by a hydrodynamic field experiment conducted in February 2016. Approximately ?138,200 m³ of sand, corresponding to 9.2% of the initial nourishment volume, were eroded over the nourishment area in about 2 years. An obvious decrease in erosion eastward with a shift from erosion to accumulation was observed, suggesting an eastward redistribution of sand. This longshore sand drift is beneficial for the eastward beach of Malo-les-Bains where most of the recreational activities are concentrated. Hydrodynamic measurements showed that waves and wave-induced currents play a major role on the longshore sand redistribution compared to tidal flows. Strong relationships were observed between cumulative offshore wave power and beach volume change during distinct beach survey periods (R² = 0.79 to 0.87), with more significant correlations for northerly waves. A slight decrease in erosion during the second year compared to the first year after nourishment suggests that the loss of sand should decrease after an initial phase of rapid readjustment of the beach shape towards equilibrium.     

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     

Demographic parameters of two populations of red coral (Corallium rubrum L. 1758) in the North Western Mediterranean

The demographic and reproductive structure of populations represents the main data set needed for conservation and management plans. Mediterranean red coral Corallium rubrum has been exploited for 2,000 years, but only recently management plans have been solicited by the international community. We examined and compared the demographic features of two red coral shallow populations located in distinct geographic locations: Portofino (Italy) and Cap de Creus (Spain). Adults and juveniles density, growth rates, population size and age structure, fecundity and fertility were examined. Juveniles were the dominant class (33 %) in both populations. The analysis of the gamete content of 653 colonies revealed that the populations have balanced sex ratios and similar fertility and polyp fecundity. The average annual growth rate, determined on 119 colonies by annual growth rings count, was similar in both populations (0.24 mm year^?1), decreasing with colony age. Maximum life span of 99 % of the colonies was 60 and 40 years at Portofino and Cap de Creus, respectively. Minimum harvestable size (7 mm basal diameter) was reached in 30–35 years, and the percentage of colonies above it was 6.7 % at Portofino and 2.1 % at Cap de Creus, where juvenile and adult colony densities were significantly lower and the percentage of commercial-sized colonies reduced by 25 % in just a few years. Notwithstanding similar growth and fecundity, the two populations showed different densities and size/age structures suggesting local factors, together with different fishing pressures, have to be taken into account in the management plans for this species.     

Environmental stability and seasonality of a harpacticoid copepod community

The southwest monsoon on the west coast of India brings about dynamic changes in estuaries and coastal waters. The response of the meiofauna to monsoonal rain is obvious, but the impact of such environmental changes on the community structure of harpacticoid copepod species and their seasonality in the estuaries influenced by the tropical monsoon is poorly understood. In this study the spatial and temporal variability in abundance and community structure of meiobenthic copepods was investigated over an annual cycle (June 1983 to June 1984), in an estuary influenced by the tropical monsoon. Total meiofaunal abundance showed wide variations in space and time. Minimum and maximum densities were observed in the monsoon and pre-monsoon seasons, respectively. Quick recovery of harpacticoid populations in the early post-monsoon season indicated their recuperative power under adverse conditions. Of the 25 species recorded from lower, middle and upper reaches, eight comprised over 70% of the total copepod population. The peak and low occurrence of dominant species displayed striking correlations with the summer and rainy seasons, respectively. While other species were restricted in distribution, Stenhelia longifurca was recorded from all salinity regimes. The harpacticoid community was greatly influenced by the onset of the monsoon period, and their spatial and temporal variabilities were related with physico-chemical parameters and the variability of these parameters in the estuary.     

A holistic evaluation of a typical coast nourishment on the Danish West Coast

The case described in this article regards 4.7 km of beach in Ferring, situated approx. 5 km south to the mouth of the Limfjord strait on the west coast of Denmark. In 2005, this section of the beach was nourished with 721,000 m³ of material in order to protect backshore properties, natural heritages and the recreational value of the beach. After the nourishment, the beach was monitored by levelling profiles on four dates to monitor and track the evolution of the nourished material. Furthermore, laboratory tests involving different gradations of nourishment material are shown which indicate solutions to different kinds of coastal protection strategies, estimate the time in between two nourishments and evaluate the cost of maintaining a beach with a high recreational value for the public.     

Contrasting life histories and secondary production of populations of Munnopsurus atlanticus (Isopoda: Asellota) from two bathyal areas of the NE Atlantic and the NW Mediterranean

The isopod Munnopsurus atlanticus occupies bathyal depths in both the Bay of Biscay (NE Atlantic; between 383 and 1022 m) and in the Catalan Sea (Northwestern Mediterranean; between 389 and 1859 m). The species was dominant in both assemblages, reaching bathymetric peaks of abundance on the upper part of the continental slope (400 m depth) in the Bay of Biscay and at ˜600 m in the Catalan Sea. Both the Atlantic and the Mediterranean populations are bivoltines. Demographic analysis of the Bay of Biscay population revealed the production of two generations per year with different potential longevity (5 mo for G₁ and 11 mo for G₂). The mean cohort-production interval (CPI) was estimated at 8 mo, and results of the demographic analysis were also used to estimate production for the Catalan Sea populations. Mean annual density (D) and biomass (B) were higher in the Bay of Biscay (D = 356.7 individuals 100 m⁻²; B = 0.803 mg dry wt m⁻² yr⁻¹) than in the Mediterranean (D = 16.3 individuals 100 m⁻²; B = 0.078 mg dry wt m⁻² yr⁻¹). Also, mean annual production was an order of magnitude higher in the Atlantic (between 4.063 and 4.812 mg dry wt 100 m⁻² yr⁻¹ depending on the method used) than in the Catalan Sea (between 0.346 and 0.519 mg dry wt 100 m⁻² yr⁻¹). M. atlanticus feeds on a wide variety of benthic and pelagic food sources. In both study areas, phytodetritus was not important in the diet of M. atlanticus. In contrast, gut-content data suggested an indirect coupling with phytoplankton production in both areas via foraminiferans. The life history and the recorded production are considered in respect to both the dynamics and levels of primary production and the total mass flux in the respective study areas. Differences in the secondary production of both populations seemed to be more consistently explained by differences in total mass flux than by differences in the primary production levels; this is also consistent with the variety of food sources exploited by M. atlanticus. Received: 22 February 1999 / Accepted: 3 February 2000