Predicted effects of climate change,vegetation and tree cover on dune slack habitats at Ainsdale on the Sefton Coast,UK

Dune slack habitats are highly dependent on the availability of water to support flora and fauna. Typically this is provided by shallow groundwater. This paper describes the seasonal and long term variation in groundwater levels in part of the Sefton coastline between 1972 and 2007. The effects of climate change, vegetation management and coastline realignment on groundwater levels are modelled. The observed annual water table levels rise and fall with an amplitude of 1.5 m, but longer term variations and trends are apparent. A stochastic water balance model was used to describe the changes in water table levels in slack floors in the open dunes and also in areas afforested with pine trees. It was found that the pine trees evaporated 214 mm/year more than open dunes vegetation, resulting in the water table being 0.5–1.0 m lower under the trees than under the open dunes. The effects of climate change on the ground water was simulated using predictions of future climate conditions based on the UKCIP02 medium high emissions scenario. The increase in temperature and change in rainfall patterns will result in a decrease in mean ground water levels by 1.0–1.5 mm in the next 90 years. Typical patterns consist of sequences of 5–10 years of low water table levels interspersed by infrequent sequences consisting of 2–5 years of relatively high or “normal” levels. These results indicate that that flora and fauna that cannot survive a 5–10 year period of water table levels >2.5 m below ground level are unlikely to survive or persist in many slack areas and a change in the ecology of these slack may become inevitable. Other effects of climate change include sea level rise which will result in a gradual rise in water table levels. Coastal erosion will increase the water table gradient to the sea and result in a slight lowering of the ground water levels. Conversely coastal accretion will reverse this process. The spatial distribution of coastal erosion and accretion along the Sefton coastline and its likely impacts on groundwater levels are discussed. The modelling work described in this paper has identified the factors which have the largest effect on groundwater levels in temperate coastal dune systems.     

Rates of shoreline change along the coast of Bangladesh

Bangladesh, at the confluence of the sediment-laden Ganges and Brahmaputra Rivers, supports an enormous and rapidly growing population (>140 million in 2011), across low-lying alluvial and delta plains that have accumulated over the past few thousand years. It has been identified as one of the most vulnerable places in the world to the impacts of climate change and sea-level rise. Although abundant sediment supply has resulted in accretion on some parts of the coast of Bangladesh, others are experiencing rapid erosion. We report a systematic assessment of rates of shoreline change over a 20-year period from 1989 to 2009, using Landsat satellite images with pixel resolution of 30 m on the ground. A Band ratio approach, using Band-5 divided by Band-2, discriminated the water line on images that were largely cloud-free, adequately registered, and at comparable tidal stages. Rates of shoreline change were calculated for >16,000 transects generated at 50 m intervals along the entire mainland coastline (>1,100 km) and major islands, using the End Point Rate (EPR) method in the Digital Shoreline Analysis System (DSAS) extension in ArcGIS®. Erosion characterises most of the seaward margin of the Sundarbans in western Bangladesh. Retreat rates of up to 20 m/yr are typical, with little evidence that local devastation of the mangrove fringe by Cyclone Sidr in November 2007 had resulted in uncharacteristic long-term rates of retreat where it made landfall. Erosion exceeded accretion in the Barguna Patuakhali coastal zone, most of which eroded at up to 20 m/yr, but with truncation of the southern tip of the Patharghata Upazila at up to 100 m/yr. In Bhola, erosion at rates of up to 120 m/yr were observed along much of the coast, but in the Noakhali Feni coastal zone, similar rates of erosion were balanced by rapid accretion of the main promontory by more than 600 m/yr. Rates of change were more subdued in the Chittagong and Cox’s Bazar coastal zones of southeast Bangladesh. Islands in the Meghna estuary were especially dynamic; Hatiya Island accreted along some of its shoreline by 50 km² between 1989 and 2009, but lost 65 km² through erosion elsewhere, resulting in the island moving south. Similar trends were observed on adjacent islands. The overall area changed relatively little across the entire coastline over the 20-year period with accretion of up to 315 km², countered by erosion of about 307 km².     

Shoreline shifting and its prediction using remote sensing and GIS techniques: a case study of Sagar Island,West Bengal (India)

The shoreline position is difficult to predict but the trend of erosion or accretion can be determined by geospatial and statistical techniques which may help in reducing the loss of property. The study aims to assess the shoreline changes and prediction in Sagar Island, a delta of the Ganges, situated in West Bengal, India. Shorelines have been delineated by using Tasseled Cap Transformation techniques from the Landsat MSS (1975), Landsat TM (1989, 1991) and Landsat ETM+ (1999, 2002, 2005, 2008, and 2011) images. The uncertainty was calculated for every year for assessing the positional error related to shoreline extraction. Total shoreline change rate/year has also been calculated and the uncertainty of total shoreline change rate was found ±3.20 m/year. In the present study, End Point Rate (EPR) and Linear Regression (LR) methods have been used for shoreline change rate calculation and prediction of shoreline. Long term (1975–2002) and short term (2002–2011) erosion and accretion rates were calculated for the study area. Sagar is the biggest island of the Sundarban region; so, it was divided into three segments in order to analyze the change on a segment basis. It was observed that the most of erosion occurred in the Segment B (south Sagar). The rate of erosion was ?7.91 and ?7.01 m/year for the periods 1975–2002 and 2002–2011 respectively. The mean shoreline change rate was high in Segment B (South Sagar) with values of ?6.46 m/year (1975–2002) but the rate was decreased into ?5.25 m/year during the later period (2002–2011). The study reveals that most of the southern part of Sagar Island is vulnerable to high rate of shoreline erosion.     

Spatial patterns and environmental correlates in leaf-associated epifaunal assemblages of temperate seagrass (<Emphasis Type="Italic">Zostera marina</Emphasis>) meadows

We estimated and tested variability of seagrass leaf-associated epifaunal assemblages at a range of scales. Sampling was performed in 36 seagrass (Zostera marina) meadows within three regions along the Swedish west coast following a hierarchical design (samples separated by 10 s m, km or 100 km). Results showed strongest variability (43–81%) at the intermediate amongst-meadow (km) scale using biomass of functional categories, while considering taxa composition the within-meadow (10 s m) scale contributed most to variability (60%). Using functional categories, we found that embayment exposure and seagrass shoot density were the most important predictor variables explaining part of the variability in biomass of suspension feeders (bivalves and barnacles) and grazers. In contrast, variability in epifaunal taxa composition was predicted mainly by sediment chemistry, substratum coverage and geographical positioning. Our findings suggest that models to develop predictive power and mechanistic understanding should focus on variables and processes varying at small and intermediate scales rather than those varying at larger scales.     

Seasonal variation in movement,aggregation and destructive grazing of the green sea urchin (<Emphasis Type="Italic">Strongylocentrotus droebachiensis</Emphasis>) in relation to wave action and sea temperature

Hydrodynamic forces are an important determinant of subtidal community structure, particularly when they limit the distribution and foraging ability of mobile consumers. We examined the effect of wave action on the rate of movement and destructive grazing of a kelp bed by the green sea urchin (Strongylocentrotus droebachiensis) under field conditions. We measured density and rate of advance at fixed intervals along ∼100 m of a grazing front over 1 year, and quantified individual movement rates in the barrens 5–10 m behind the urchin front using a time-lapse videography. Seasonal variation in the mean rate of advance of the front (range: 0–4 m month⁻¹) was explained by changes in urchin density at the front (120–360 individuals m⁻²), which in turn varied inversely with significant wave height (0.5–2 m). Water temperature (0.8–17.6°C) had no effect on the rate of advance or on urchin density (aggregation) at the front, except when temperature exceeded 17°C. Movement of individual urchins also was affected by wave action: we observed a significant decrease in speed and displacement of urchins with increasing significant wave height. Wave action had no effect on the proportion of urchins moving or the degree of linearity of their movements. We propose that the decrease in urchin density at the front associated with increased wave action, results from de-aggregation, which reduces the risk of dislodgement, combined with a reduction in urchin movement in barrens, which supplies new urchins to the front.     

Experimental study on dynamic equilibrium of headland-bay beaches

A dynamic equilibrium bay (DEB) is an embayment with continuous sediment supply and its shoreline planform can remain stable over a long period of time without erosion or accretion. For coastal conservation of sandy headland-bay beaches (HBB), the concept of using a static equilibrium bay (SEB) is well known, but that for DEB has received little attention. Moreover, an empirical equation for the stability of a DEB is not yet available. Experiments on DEB shape that aim to derive new coefficients in the parabolic bay shape equation (PBSE) for DEB are now being conducted in the laboratory. The work commences from an initial artificial HBB in static equilibrium with sediment supply source from the lee of an upcoast headland. A final equilibrium planform is obtained for the condition with a specific wave obliquity and sediment supply rate until no further shoreline change is found. In order to fit the PBSE for a DEB, a new parameter called SSR (sediment supply ratio) that represents the ratio of sediment supply rate from the source and the potential longshore sediment transport rate is introduced to quantify the balance of sediment to the bay. Alternative C coefficients in the PBSE for DEB, which include wave obliquity and the SSR, are then calculated. These new coefficients for DEB can now be used to evaluate the influence of sediment supply from a riverine source on a DEB and to classify its equilibrium status for planning sediment management strategies in coastal conservation.     

Feeding of Clausocalanids (Calanoida,Copepoda) on naturally occurring particles in the northern Gulf of Aqaba (Red Sea)

A total of 12 feeding experiments were conducted in the northern Gulf of Aqaba during spring (March/April) and autumn (September/October) 2002 at the Marine Science Station (MSS) in Aqaba. Females of three species of clausocalanids were selected: Clausocalanus farrani, C. furcatus and Ctenocalanus vanus. Natural occurring particle (NOP) larger than 5 μm were investigated as food source. The ambient chlorophyll a concentration at sampling depth (∼70 m) ranged between 0.15 and 1.00 μg chl a l⁻¹ and NOP concentrations ranged between 1.78 and 14.0 × 10³ cells l⁻¹ during the sampling periods. The division of particles into five size classes (5–10, 10–20, 20–50, 50–100 and >100 μm) revealed that most of the particles were found in the size classes below 50 μm (81–98%), while most of the natural occurring carbon (NOC) was concentrated in the size classes larger than 20 μm (70–95%). Ingestion rates were food density dependent rather than size dependent ranging between 0.02 and 1.65 × 10³ NOP ind⁻¹ day⁻¹ and 0.01 and 0.41 μg NOC ind⁻¹ day⁻¹, respectively, equivalent to a body carbon (BC) uptake between 0.4 and 51.8% BC day⁻¹. The share of the size classes to the total ingestion resembled in most cases the size class composition of the natural particle community.     

Tributyltin pollution in sediments from Alexandria's coastal areas

Presence of Tributyltin (TBT) in Alexandria’s coastal water areas has been demonstrated by measuring concentrations of this compound. The TBT was measured in sediments from three docking areas namely: Western Harbour, Eastern Harbour and Abu Qir Bay. The sediment of those areas has been affected by marine traffic and other industrial activities. This is reflected by the distribution of TBT in the sediments nearby the shipyards in the three docking areas of the region where the average values of 258.6 ηg TBT/g for Western Harbour; 126.4 ηg TBT/g dw for Abu Qir Bay and 42.3 ηg TBT/g dw for the Eastern Harbour were recorded. This fact reflects the effect of industry and marine traffic on the marine environments of the Alexandria region.     

Reproductive biology of the deep-sea octocoral Drifa glomerata in the Northwest Atlantic

The present study examined the mode and timing of reproduction of poorly understood deep-water octocorals and the environmental factors that may influence their reproductive patterns. Data on reproductive characteristics of the octocoral Drifa glomerata (Alcyonacea: Nephtheidae) collected between 2004 and 2007 at ca. 100–330 m depth off Newfoundland and Labrador (eastern Canada) were compared among years, months and depth ranges. No male gonad was ever observed during the study. The ratio of fertile colonies possessing large pinkish polyps with oocytes/planulae was >50% throughout the year. The number of brooded planula larvae within a single fertile polyp varied between 1 and 10 for a total of approximately 40–3,000 in a whole colony. The size of oocytes and/or planulae was consistently greater in the polyps than in the branchlets, indicating that the development pathway of oocytes to planulae is from the branchlets to the polyps. Although larval production seemed to persist year round, the onset of major planulation events occurred in December–January of two consecutive years, when large mature planulae were released in correlation with the first increase of photoperiod and maximum temperature at 150 m. A second peak in planulation between April and early June followed the phytoplankton bloom. Seasonal trends were more apparent in colonies from <200 m, and the planula index varied among sampling depths and years. Larval release in a live colony under laboratory conditions occurred between January and June 2008, closely following predictions based on field samples.     

Integrated shoreline management and tourism development on the cross-border World Heritage Site: A case study from the Curonian spit (Lithuania/Russia)

The varied and very dynamic landscape with a high biological diversity is a distinctive feature of the Curonian spit at the regional scale. Throughout the 20th century the main morphodynamic trend in the littoral of the Curonian spit was shoreline grading on the lagoon side, whereas on the marine side the increasing erosion at the foot of the spit, and increasing accretion at the head of the spit prevailed. The results of a discriminant analysis (Wilkes’ λ = 0.001626 and F = 29.267 when p < 0.001) show that sites with prevailing erosion, accretion and sediment input from the drifting dunes form regular inter-related spatial structures in the littoral with distinctive resulting discontinuities of the sediment drift along the lagoon coast. Dune littoral cells are characterized by Aeolian sediment input and distribution ‘down-drift’, (usually northwards) from the source. The most likely changes in the current development trends of the lagoon shore zone of the Curonian spit are related to expected climate changes and further slowing down of the dune drift. The probability of storms and ice-drift events, and their impact on coasts is expected to increase as a result of climate change. The dune advance will gradually slow down, and with it, the sand input to the coastal zone will decline. In this paper, we define integrated shoreline management as a system of long-term shoreline management measures, which is based on a littoral cell approach and aimed at harmonizing human activity in the coastal zone with the natural development of the shoreline. We propose an integrated management program for the lagoon shoreline of the Curonian spit, which is site-specific for each littoral cell as a coastal management unit. Drifting dunes and seaside beaches are the natural amenities, which are best known and best appreciated on the Curonian spit by 49% of the respondents representing the total Lithuanian population. A responsible tourism development should be considered as the key means for proper appreciation of the drifting dunes and natural coasts by society, which means to acknowledge and cherish the aesthetic and conservation values of dune and coastal landscapes of the Curonian spit as a World Heritage Site. There are at least two pre-conditions for this: (1) to provide visitors with sufficient information about diverse values and functions of the Curonian dunes and coasts within a broader regional and global heritage conservation context; (2) to enable tourists to enjoy the most impressive dune and coastal landscapes at close range. In this paper we propose to encourage active dune tourism, to reintroduce grazing into the Curonian dune areas, to restore and to preserve the most impressive landscapes of the highest white drifting dunes by bringing the blown out sand from the leeward foot of the dunes back to the crest artificially.     

Migration,distribution, and diving behavior of adult male loggerhead sea turtles (<Emphasis Type="Italic">Caretta caretta</Emphasis>) following dispersal from a major breeding aggregation in the Western North Atlantic

Sixteen satellite-tagged adult male loggerhead sea turtles (Caretta caretta) dispersed widely from an aggregation near Port Canaveral, Florida, USA (28°23′N, −80°32′W) after breeding. Northbound males migrated further (990 ± 303 km) than southbound males (577 ± 168 km) and transited more rapidly (median initial dive duration = 6 (IQR = 4–16) versus 19 (IQR = 10–31) min, respectively).. Migration occurred along a depth corridor (20–40 m) except where constricted by a narrow continental shelf width. Males foraged in areas 27 ± 41 km² day⁻¹ at locations <1–80 km from shore for 100.1 ± 60.6 days, with variability in foraging patterns not explained by turtle size or geography. Post-breeding dispersal patterns were similar to patterns reported for adult female loggerhead sea turtles in this region and adult male loggerhead sea turtles elsewhere in the northern hemisphere; however, foraging ground distributions were most similar to adult female loggerhead sea turtles in this region.     

Population structure of two deep-sea hydrothermal vent gastropods from the Juan de Fuca Ridge, NE Pacific

The gastropods Lepetodrilus fucensis and Depressigyra globulus are abundant faunal components of animal communities at deep-sea hydrothermal vents along the Juan de Fuca Ridge in the NE Pacific. The population structure and recruitment pattern of both species were studied using modal decomposition of length–frequency distributions. Gastropod populations were collected from Axial Volcano and Endeavour Segment in 2002 and 2003. Polymodal size–frequency distributions, particularly at Axial Volcano vent sites, suggest a discontinuous recruitment pattern for D. globulus. In contrast, there were no distinct peaks visible in the distributions of L. fucensis, suggesting a continuous recruitment pattern for this species. For both species, distributions were positively skewed towards the smaller length–classes, implying post-settlement mortality is high. However, variations in growth, due to short- and long-term variability in environmental conditions in the hydrothermal vent habitat, as well as biological interactions, may also be influencing the distribution and abundance of subsequent life-history stages. Using maximum shell lengths from populations of known ages, the growth rate of L. fucensis was estimated as 9.6 μm day⁻¹, indicating adulthood would be reached in ∼1 year. Our results suggest that, despite occupying the same habitat, abundance and population structure are regulated by different biotic and abiotic processes in L. fucensis and D. globulus.     

Shoreline changes in response to sea level rise along Digha Coast,Eastern India: an analytical approach of remote sensing,GIS and statistical techniques

Shoreline is one of the rapidly changing linear features of the coastal zone which is dynamic in nature. The issue of shoreline changes due to sea level rise over the next century has increasingly become a major social, economic and environmental concern to a large number of countries along the coast, where it poses a serious problem to the environment and human settlements. As a consequence, some coastal scientists have advocated analyzing and predicting coastal changes on a more local scale. The present study demonstrates the potential of remote sensing, geospatial and statistical techniques for monitoring the shoreline changes and sea level rise along Digha coast, the eastern India. In the present study, multi-resolution and multi temporal satellite images of Landsat have been utilized to demarcate shoreline positions during 1972, 1980, 1990, 2000, and 2010. The statistical techniques, linear regression, end-point rate and regression coefficient (R²) have been used to find out the shoreline change rates and sea level change during the periods of 1972–2010. Monthly and annual mean sea level data for three nearby station viz., Haldia, Paradip and Gangra from 1972 to 2006 have been used to this study. Finally, an attempt has been made to find out interactive relationship between the sea level rise and shoreline change of the study area. The results of the present study show that combined use of satellite imagery, sea level data and statistical methods can be a reliable method in correlating shoreline changes with sea level rise.     

Implications of sea level rise for coastal dune habitat conservation in Wales,UK

The potential impact of future sea level rise and climate change on 15 Welsh coastal dune systems has been investigated. Historical Trend Analysis was undertaken using Ordnance Survey maps to quantify past shoreline change and to permit extrapolation of past trends to predict possible future shoreline positions by 2080–2100. Predictions were also made using the Bruun Rule relationship between sea level rise and shoreline response and an integrated method of assessment, Expert Geomorphological Assessment (EGA), which provides a ‘best estimate’ of future coastline change, taking into account such factors as geological constraints, the nature of past, present and future environmental forcing factors, and known coastal process–response relationships. The majority of the 15 systems investigated experienced a net increase in dune area over the last 100–120 years. Only one (Whiteford Burrows) experienced significant net area loss (>5 ha). EGA predictions suggest that several systems are likely to experience significant net loss of dune habitat over the next century, whilst continued net gain is likely to occur for systems where sediment supply rates remain high. Little net change is predicted in some systems. Considering the 15 dune systems together, it is considered unlikely that net dune habitat loss will exceed net gain over the next 100 years provided that there are no major disruptions to sediment supply and natural coastal processes.     

Vertical movements, behavior, and habitat of bigeye tuna (Thunnus obesus) in the equatorial eastern Pacific Ocean, ascertained from archival tag data

The results presented in this report are based on analyses of 16,721 days of data downloaded from 96 archival tags recovered from bigeye tuna (Thunnus obesus; 54–159 cm in length, 0.97–5.44 years of age) at liberty from 31 to 1,508 days in the equatorial eastern Pacific Ocean. Analyses of daily timed depth and temperature records resulted in the classification of the data into three daily behavior types: characteristic, associative (associated with floating objects), and other. There is a significant positive correlation between the proportion of time fish exhibit characteristic behavior and increasing length, and significant negative correlations between the proportion of time bigeye exhibit associative and other behavior with increasing length. For the smallest (54–80 cm) to largest (100–159 cm) length classes, the vertical habitats utilized when exhibiting non-associative behaviors were 99 and 98% of the time above the thermocline depth (60 m) during the night, at the same average depth of 34 m, and 60 and 72% of the time below the thermocline during the day at average depths of 163 and 183 m, respectively. For the same smallest to largest length classes, when exhibiting associative behavior, the average nighttime and daytime depths were 25 and 21, and 33 and 37 m, respectively. The apparent effects of the environment on the behavior of the fish are discussed.     

Population biology of the annual grassTriplasis purpurea in relation to distance from shore on Staten Island, New York

Four populations of the native annual grassTriplasis purpurea were surveyed on coastal beaches along the south shore of Staten Island, NY, to determine the potential of this species to colonize shoreline habitats mostly devoid of other vegetation. If the species can establish and maintain dense populations, it may have conservation value for urban beaches disturbed by human activities. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites,T. purpurea occurred in >75% of all quadrats and the highest density was 1195 plants/m² at 74 m from shore in one recently disturbed site. Density generally increased with increasing distances from shore at low tide (from ca. 40 – 90 m). Plants showed the greatest growth and reproduction at close distances to shore (30 – 40 m); part of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Improved vigor nearest to shore may be due to continual sand deposition. Survivorship showed a Type I pattern, with low mortality throughout the growing season. By colonizing newly-deposited and continually shifting sands,T. purpurea can contribute to the earliest stages of ecological succession along disturbed beaches in eastern North America and may be valuable to the development and management of urban coastal plant communities.     

Shoreline rotation and response to nourishment of a gravel embayed beach using a low-cost video monitoring technique: San Michele-Sassi Neri,Central Italy

On beaches where natural shoreline variability is significant, beach nourishment is a useful engineering method to augment the dry beach and protect infrastructure and/or unstable cliffs. In this study, a low-cost video monitoring system is used to monitor the shoreline response to a nourishment operation on a dynamic gravel embayed beach in Central Italy. Video-derived shorelines were collected over a 15-month period to measure the evolution of the beach with regards to three specific parameters: the dry beach width, the dry beach area and the beach orientation. Moderate increases in the dry beach width of 3.6 m and 6.7 m across the embayment were observed in response to two different gravel nourishments of approximately 40,000 m³ and 46,000 m³ respectively. The orientation of the beach meanwhile was found to rotate rapidly in the clockwise direction and more gradually in the counter-clockwise direction. Analyses of individual storm events suggest these rapid clockwise rotations are caused by ESE storms, which result in beach retreat particularly at the southern end. The combination of an overall narrow beach width and a clockwise beach orientation is observed to cause a cliff erosion event at a vulnerable point along the embayment.     

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 μg/l (2.8–170.8 μg/l, n = 20), 393 μg/l (9–704 μg/l, n = 5), and 104.5 μg/l (2.51–543 μg/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan.     

Population biology of the annual grass Triplasis purpurea in relation to distance from shore on Staten Island, New York

Four populations of the native annual grassTriplasis purpurea were surveyed on coastal beaches along the south shore of Staten Island, NY, to determine the potential of this species to colonize shoreline habitats mostly devoid of other vegetation. If the species can establish and maintain dense populations, it may have conservation value for urban beaches disturbed by human activities. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites,T. purpurea occurred in >75% of all quadrats and the highest density was 1195 plants/m² at 74 m from shore in one recently disturbed site. Density generally increased with increasing distances from shore at low tide (from ca. 40–90 m). Plants showed the greatest growth and reproduction at close distances to shore (30–40 m); part of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Improved vigor nearest to shore may be due to continual sand deposition. Survivorship showed a Type I pattern, with low mortality throughout the growing season. By colonizing newly-deposited and continually shifting sands,T. purpurea can contribute to the earliest stages of ecological succession along disturbed beaches in eastern North America and may be valuable to the development and management of urban coastal plant communities.     

Multi-year observations on the gametogenic ecology of the Antarctic seastar <Emphasis Type="Italic">Odontaster validus</Emphasis>

This study reports the first multi-year observations on the reproductive patterns for an Antarctic predator/scavenger, Odontaster validus (Koehler 1912). Seastars were collected monthly from a shallow site (15–20 m depth) near the British Antarctic Survey (BAS) Rothera Research Station (Adelaide Island, 67°34′S 68°08′W) from July 1997 to January 2001. Reproductive condition, oocyte size frequencies and spermatogenesis were examined in at least ten seastars each month using histological and image analysis techniques. Gonad indices (GI) and pyloric caeca indices (PI) were also examined in the same samples. Female and male GIs varied seasonally, in parallel with a reduction in the proportion of large oocytes and mature sperm in the gonad in August to mid-October following winter spawning. Despite there being remarkable consistency in the timing of spawning from year to year, differences in the reproductive condition of individuals were apparent. Patterns in the digestive tissues also varied with season, peaking in December and reaching a minimum in February in two of the three study years. This weaker annual pattern may partly reflect the varied diet of this predator/scavenger species, which is not directly dependant on the timing and magnitude of the annual phytoplankton bloom. Pooled oocyte size distributions and residual analysis suggested that oogenesis progressed over 18–24 months, with the largest of the two size classes (maximum diameter = 183 μm) being spawned annually. This pattern of oocyte growth and spawning was previously reported in the early 1960s for an O. validus population from McMurdo Sound, which lies south of Rothera by 10° latitude. The extremely catholic diet of this predator/scavenger suggests the reproductive patterns of the seastar will be less susceptible to changes in food supply compared to polar suspension feeders or deposit feeders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.