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... During mining operations, sand is extracted from dunes, intertidal and subtidal environments and used for construction purposes (Masalu 2002), to obtain heavy minerals (Ghosh and Prasad 2006) or diamonds . Heavy machines are employed, which traverse on the beach impacting directly on beach fauna and the organisms erosion scarp is accentuated (Jonah et al. 2015). Sediment depletion caused by Besides recreation, there are other human activities related to resource exploitation Besides recreation, there are other human activities related to resource exploitation Sand is, together with gravel, the most exploited solid material worldwide and Sand is, together with gravel, the most exploited solid material worldwide and which generally leads to overexploitation (Torres et al. 2017). ...
... An independent 20 years work demonstrated a 4-fold decline in shorebirds density due to the same diamond mine and suggested that it was associated with a decrease in the abundance of shorebird preys (Simmons 2005). Sand extraction by mining operations can also lead to coarser sediment grain size which has been linked to decreased ghost crabs densities and burrows diameter (Jonah et al. 2015). In this case, coarser sand could be avoided by crabs due to less resistance of burrows or less water holding capacity of sediments. ...
... Indeed, the density of Ocypode spp. has been used as an indicator of anthropogenic impact on beaches across their range, and has been found to decrease as a result of human impacts (Wolcott and Wolcott 1984;Barros 2001;Moss and McPhee 2006;Neves and Bemvenuti 2006;Lucrezi et al. 2009b;Schlacher and Lucrezi 2010;Aheto et al. 2011;Jonah et al. 2015; but see Schlacher et al. 2016). The density of Ocypode populations can be measured using a variety of methods, including visual census, physical collection of specimens, and counts of the number of burrows as a proxy for the number of individual ghost crabs (Schlacher et al. 2016). ...
... The significantly lower Ocypode burrow density found at beaches adjoining the hotel sites compared to the residential housing sites confirms previous findings that showed a negative impact of various types of human disturbance on ghost crab density (i.e. Barros 2001;Moss and McPhee 2006;Lucrezi et al. 2009b;Aheto et al. 2011;Lucrezi and Schlacher 2014;Jonah et al. 2015). Hotel sites undoubtedly have a greater negative impact on coastal sites than residential housing due to the increased number of people attracted to the beach sites, with consequential increases in habitat disturbance, such as through destruction, fragmentation or modification (including beach cleaning), trampling and pollution (Reyes-Martínez et al. 2015). ...
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Ghost crab (Ocypode species) burrow densities have previously been used as an indicator of anthropogenic impact. This study aimed to assess the burrow density of Ocypode species (O. ryderi and O. cordimanus) at four sites across Watamu Marine National Park, Kenya. Two sites were in front of hotel complexes (denoting a high degree of urbanisation), and two were in front of residential housing among coastal scrub (denoting a low degree of urbanisation). The findings reveal significantly higher burrow densities at sites in front of residential housing, which was the less developed area. This provides further evidence that Ocypode burrow densities can be used, where other methods would be impractical, to estimate the impact of some human activities along beach fronts, such as at Watamu Marine National Park.
... On sandy beaches, ghost crabs (Crustacea: Brachyura: Ocypodidae) are a widely used indicator species for the health of sandy beach ecosystems (Schlacher et al., 2016), and previous studies have found that their populations are susceptible to human activities on beaches around the world (e.g. Jonah et al., 2015;Schlacher et al., 2011). They are key consumers on sandy beaches (Schlacher et al., 2013b), playing the important ecological role of being apex invertebrate predator and scavenger in these systems, whilst also being important prey for many higher order vertebrate consumers from nearby terrestrial ecosystems (Lucrezi and Schlacher, 2014). ...
... While the using of proxy measures is common in the literature, its accuracy is limited given that discrete classifications of human usage may not reflect likely variation in beach visitation through time in response to weather, local events of seasonality. In spite of these possible limitations, Jonah et al. (2015) found similar results to Noriega et al. (2012) using a direct measure of trampling, with low use beaches having higher numbers of burrows and larger burrow sizes compared to medium use and high use beaches. Similarly, Reyes-Martínez et al. (2015) found a dramatic reduction in abundance and a significant change in community structure in periods before and after trampling (although this study did not include ghost crabs). ...
Article
Sandy beaches in highly urbanised areas are subject to a wide range of human impacts. Ghost crabs are a commonly used ecological indicator on sandy beaches, as they are key consumers in these systems and counting burrow openings allows for rapid assessment of population size. This study assessed the pressures of urbanisation on sandy beaches in the highly urbanised estuary of Sydney Harbour. Across 38 beaches, we examined which physical beach properties, management practices and human induced habitat modification best predicted ghost crab distributions. Of all variables measured, the frequency of mechanical beach cleaning was the most important predictor of crab abundance, with low burrow densities at the highest cleaning frequency and the highest densities at beaches cleaned at the intermediate frequency (≤3 times per week). These results indicate that ghost crab populations in Sydney Harbour are more robust to the impacts of urbanisation than previously thought.
... Not surprisingly, removing often large volumes of sand from beaches can lead to significant changes in landforms and sediment properties, and can accelerate erosion (Jonah et al., 2015) to the point where mining on sandy-shores has been labelled as effectively constituting "active destruction" of beaches (Pilkey and Cooper, 2014). Further geo-morphological impacts arise from the disposal of tailings or slurries on the beach or into the nearshore zone (Castilla, 1983). ...
... Habitat alterations caused by mining operations on beaches and in dunes translate into significant ecological harm, generally manifested as reductions in abundance, biomass, and diversity of beach-associated species, local extirpations, and major shifts in the species composition of assemblages exposed to mining (Pulfrich and Branch, 2014;Simmons, 2005). Ghost crabs can respond in a similar pattern to habitat changes arising from sand extraction, but the generalisations about biological impacts are impossible to make from a single study (Jonah et al., 2015). Thus, ecological cause-and-effect studies of beach and dune mining using ghost crabs as ecological indicator species in more locations, and using more response variables, have future potential. ...
... This approach is often perceived by coastal authorities in developing countries as expensive due to the labourintensive nature of estimating beach biodiversity. However, recent studies such as Aheto et al. (2011) andJonah et al. (2015b) have established this technique to be inexpensive, simple to undertake and easily funded by coastal authorities in developing nations taking cognisance of the useful ecological benefits of such programmes. ...
... In this study, beaches with the highest human use and modification had the lowest ghost crab populations. Similar observations of the effects of various human activities on Ocypode spp have been documented in several recent studies, such as trampling (Noriega et al., 2012;Reyes-Martínez et al., 2015), beach sand mining (Jonah et al., 2015b), off-road vehicles Schlacher and Lucrezi, 2010), beach sweeping (Yong and Lim, 2009) and dune modification and shoreline armouring (Lucrezi et al., 2009b;Hubbard et al., 2013). Such activities cause direct changes to the habitat, destroy the dune systems, change the natural physical characteristics of the beaches, eliminate food sources, and reduce habitats and shelter areas (Reyes-Martínez et al., 2015). ...
Article
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The increasing urbanization of much of the world’s coasts threatens irreversible damages to beach ecosystems, if unchecked. Unfortunately, beach monitoring programmes for remediation actions are uncommon, especially for less developed nationswhere infrastructural development and socio-economic goals are regarded more important than environmental goals. This study aimed at obtaining information about the effects of themodification and use of beaches and dunes on beach biota using ghost crab burrow density and size as variables. The study tested a hypothesis that themean densities and sizes of ghost crab burrows on six beaches under three categories of human use in the Central Region of Ghana are different. Results indicated that low use beaches had significantly higher numbers of burrows and larger burrow sizes compared tomediumuse and high use beaches. Since physical and environmental parameters were consistently the same amongst the six surveyed beaches, the paper concluded that the differences in the observed beach use and dune modifications were responsible for the observed differences in ghost crab abundance and sizes. Major beach use such as intense trampling levels and clearing of dune vegetation for infrastructural developments are most likely responsible for the observed differences. On account of ecological considerations, it is recommended that beach land use reforms by coastalmunicipal authorities inGhana should ensure that infrastructure development along undeveloped sections of the coast is limited to a safe distance from the shoreline. There should also be consideration of natural vegetation barriers between development and the beach to enhance natural beach–dune ecosystem interaction.
... All these activities disrupt coastal the protection function of sandy ecosystem types because they destabilise sensitive dunes and can cause sand blowouts leading to erosion, flattening and loss of dunes (Hesp, 2002). Sand, mineral and diamond mining occur in the South African seashore zone and, as for coastal development, change and reduce coastal habitats (Jonah et al., 2015;Pulfrich and Branch, 2014;Thornton et al., 2006). The reduced kelp density through kelp harvesting probably impacts the ecosystem function to slow down currents and dampen waves (Jackson and Winant, 1983;Mork, 1996). ...
... Les méthodes les plus communément et anciennement mises au point reposent sur des suivis présence/absence, abondance, structure d'âge/taille. Concernant les crabes, l'abondance des populations est souvent utilisée comme un indicateur face à des pressions anthropiques telles que l'activité minière, l'urbanisation ou encore la présence de contaminants Jonah et al., 2015;Schlacher et al., 2016;Wildsmith et al., 2009). ...
Thesis
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Parmi les phénomènes d'origine anthropique impactant les écosystèmes de mangrove, l'apport d'éléments nutritifs issus des eaux usées domestiques est souvent associé à une meilleure productivité végétale. D'autres compartiments du système sont pourtant parfois négativement impactés, notamment la macrofaune benthique dont les représentants sont souvent considérés comme des espèces ingénieurs de l’écosystème. Au cours de cette thèse, nous avons cherché à étudier les réponses écophysiologiques de trois espèces de crabes de mangroves présents dans le Canal du Mozambique, exposés aux apports d’eau usée domestique ou à de l’ammonium, étudié en tant que potentiel proxy d’enrichissement azoté. Différents marqueurs physiologiques et comportementaux ont été mis en place pour répondre à trois objectifs s’appuyant sur des niveaux intégratifs et des échelles spatiales différentes. Dans une première partie, nous avons cherché à compléter les connaissances sur les réponses physiologiques d’une espèce de crabe, Neosarmatium africanum, Sesarmidae occupant la partie haute de la mangrove, parfois directement exposée aux apports d’effluents domestiques sur l’un site d’étude (mangrove de Malamani, Mayotte) en nous focalisant sur un organe métabolique majeur, l’hépatopancréas. Dans une deuxième partie, nous avons cherché à mieux comprendre quelles potentielles réponses physiologiques et comportementales à l’échelle individuelle pouvaient être impliquées dans la modification des communautés de crabes observées dans des zones régulièrement impactées par l’apport d’eau usée domestique. Nous avons pour cela étudié une espèce de crabe violoniste, Paraleptuca chlorophthalmus, Ocypodidae, dont l’abondance diminue drastiquement sur les zones impactées de la mangrove de Malamani. Nos résultats montrent des réponses à court terme (explosion de la consommation d’oxygène, comportement de fuite et d’émersion) qui pourraient devenir délétères lors d’expositions ponctuelles mais chroniques, comme c’est souvent le cas dans le milieu naturel. Enfin, nous avons cherché à comprendre s’il existait une vulnérabilité différentielle face à des variations de salinités et des apports d’éléments nutritifs (ammonium) sur deux espèces de crabes violonistes génétiquement proches mais vivant dans des conditions environnementales opposées : mangrove de Malamani à Mayotte considéré comme écosystème anthropisé et la mangrove d’Europa (îles Eparses, Sud du Canal du Mozambique) considérée comme écosystème pristine. Les résultats indiquent que les crabes de Mayotte, régulièrement exposés à l’eau douce et aux effluents domestiques, semblent plus tolérants aux variations de salinité et développent des acclimatations physiologiques face à l’exposition à l’ammonium, ce que les crabes d’Europa ne développent pas. L’ensemble des résultats renforcent d’une part les connaissances sur la physiologie de ces ingénieurs de l’écosystème, mais permettent également de mieux lier les réponses individuelles obtenues en laboratoire, à celles observées à l’échelle des populations ou des communautés en milieu naturel. Ils encouragent la mise en place d’études concernant le suivi des écosystèmes de mangroves du Canal du Mozambique à travers l’étude d’espèces potentiellement bioindicatrices et permettent de proposer une approche écophysiologique dans le domaine du suivi et de la conservation des milieux naturels.
... The impact of sediment movements on vegetation, macro-fauna (e.g., benthic species and communities), habitats and diverse ecosystems is part of the focus of some of the papers sampled for this review. GRADISTAT was applied in examining, determining the patterns of, and the relationship between grain size parameter and the fauna community structure (Witmer et al., 2018;Amao et al., 2019;Bertocci et al., 2019;Cabral et al., 2020;Callaway et al., 2020;Greene et al., 2020), the influence of particle size statistics on sediment gradient and vegetation (Connolly et al., 2016;Ha et al., 2018), the relationship between physical datasets (sediment particle sizes) and nearshore habitat (Dean et al., 2013;Bessa et al., 2013;Barik et al., 2014;Jonah et al., 2015;Degli et al. 2021), and on invertebrate assemblages (Witmer et al., 2019;Pryor et al., 2020), among others. Many factors threaten the survival of biodiversity globally, the eutrophication of surface water and high concentration of phosphorus is considered as among the most significant causes (Crocker et al., 2021). ...
Article
The study of sediment dynamics using grain size parameters is well established in sedimentology and earth sciences. To help the wide-ranging needs of researchers in the fields of earth and depositional sciences, Blott & Pye (2001) wrote a GRADISTAT program that is integrated into a Microsoft Excel spreadsheet. This study reviewed 66 scientific articles principally found in ScienceDirect. Sampled research papers are categorised into six general groups and summarised in terms of the most environmental themes addressed. The themes covered in this paper are: the understanding of land-sea interactions and processes; sediment contaminations and pollution; impacts of sediment variables and transportation on macrofauna, vegetation and habitat; microplastics; soil genesis and movement; and, palaeontology. The ubiquitous nature of this application has shown it applied in many parts of the world. The GRADISTAT will continue to be a relevant environmental advance that is essential in classifying sediments in depositional environments.
... In general, these beaches are ecologically relevant, since they are the sites of various processes such as filtration and purification of water, storage and transport of sediments, mineralization and recycling of nutrients. They are also nesting sites for turtles and birds, favor the decomposition of organic materials and pollutants, and allow functional links between terrestrial and marinecoastal environments [6,7,8]. ...
Article
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Coastal zones are highly dynamic environments that provide a range of ecosystem services. They are influenced by natural and anthropogenic factors, leading to increasingly drastic changes which have negative impacts on biological diversity and human communities. The present study characterizes the beaches of the Southern Caribbean of Costa Rica (SC-CR) to provide a baseline for marine-coastal management. Eight beaches of the SC-CR were studied, and 47 transects were defined in which the following information was obtained: beach width, scarp width and height, average particle size in dunes, plant species, and vegetation cover and height. Puerto Viejo and Vizcaya were determined to have the greatest average width, while Manzanillo and Gandoca had the smallest. In 25.24% of the sampled points there were signs of erosion. The width of the scarp varied from 3.90 m to 43.70 m and the height between 15 cm and 70 cm. The sand particles in 87.5% of the beaches were medium-sized. A total of 283 trees or shrubs from 11 families and 11 species were counted. In conclusion, the characterization of the SC-CR beaches allowed generating baseline information on the state of the physical and biological aspects of these ecosystems, as well as showing that these beaches are exposed to change. However, it is necessary to establish whether these are related to the dynamics of the beaches themselves or due to the interactions of elements such as sea level rise, thermal expansion and changes in current patterns due to climate change or global change.
... Unsustainable sand mining has adverse effects on the environment, human beings, and even managing disasters [7][8][9][10][11][12][13]. Based on the research by Thornton, Sallenger [14], one of the primary causes of erosion rates in bays' shoreline was sand mining. The biological assessment of several beaches by Jonah, Agbo [15] detects that sand mining has negative ecological impacts. Lai, Shankman [16] demonstrated that the decline in some lakes levels resulted from the extensive sand mining. ...
Chapter
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In the past two decades, sand and gravel are the most significant portion of primary material inputs used in building and transport infrastructure and are the most-extracted group of raw material in the world, exceeding both fossil fuels and biomass. Sand is an essential ingredient for many industries, including concrete, glass, and electronics. There is a growing demand for sand where there is rapid economic development. Scientists have been studying the effects of building new infrastructure systems on habitats but have overlooked the impact of extracting sand to make those new systems. This lack of focus on the effects of mineral extraction, is probably due to lack of awareness. The absence of data on aggregates sand mining leads to lack of awareness and makes observations, about its impact, very difficult. This study proposes a systematic monitoring mechanism for the sand extractions and trade that can bridge the current data and knowledge gap. The main goal of the study is to develop a sand governance framework to regulate sand extraction, use, and trade. First, space imagery technology is employed to analyze the sand resource; then a business framework is developed applying blockchain technology, which generates trusted decentralized network and bypasses central authorities.
... Although anthropogenic impacts are considered to have negative effects on crab abundance, and some authors have used ghost crabs as ecological indicators (Neves and Bemvenuti, 2006;Lucrezi et al., 2009b;Lucrezi et al., 2009a;Schlacher et al., 2011;Noriega et al., 2012;Jonah et al., 2015), the massive presence of O. cursor in several Sicilian urban beaches suggests that the species is rather tolerant to human presence, and may even benefit from food supplementation due to human presence. This tolerance can be explained by the nocturnal habits of the species. ...
Article
The tufted ghost crab, Ocypode cursor, was recorded for the first time on the coast of Sicily mainland in 2009, however no ecological studies were conducted so far. In this study, we provide the first ecological data, based on massive data collection of the ghost crab in Sicily. In particular, we studied the spatio-temporal distribution of the species in the recently colonized urban beach of Avola. Our results showed that this species' activity is mainly affected by temperature (crabs were more active during warmer months), while distance from the shoreline affected size distribution (larger crabs were usually found farther away from the shoreline). Crabs feed on a great variety of food items, and are undergoing northward range expansion.
... However, changes in behavior may also be used as a bioindicator, as species may change their behavior and daily activities under altered conditions due to direct and indirect human disturbances (Sih, Stamps, Yang, McElreath, & Ramenofsky, 2011;Sih, 2013;Wong & Candolin, 2015;Fontúrbel, Candia, Malebrán, Salazar, González-Browne, & Medel, 2015;Costa, Madureira, & Zalmon, 2019). For example, population abundance of some crab species is commonly used as bioindicators of various human disturbances such as urbanization, mining, and contamination Jonah, Agbo, Agbeti, Adjei-Boateng, & Shimba, 2015;Schlacher et al., 2016;Wildsmith et al., 2009), and some of these species additionally alter burrowing behaviors in disturbed sites (Weis & Perlmutter, 1987;Bartolini, Penha-Lopes, Limbu, Paula, & Cannicci, 2009;Culbertson et al., 2007;Gül & Griffen, 2018a). Species may also alter their feeding habits (Griffiths et al., 2017;Jokimäki, Suhonen, Jokimäki-Kaisanlahti, & Carbó-Ramírez, 2016) and trophic interactions (Costa, Tavares, Suciu, Rangel, & Zalmon, 2017;Gray, Baldauf, Mayhew, & Hill, 2007) in areas with human disturbance, and thus these changes in behavior and daily activities can result in changes to the energy balance and physiological state (Chandurvelan, Marsden, Glover, & Gaw, 2015;Spellerberg, 2005). ...
Article
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Bioindicator species are extensively used for rapid assessment of ecological changes. Their use commonly focuses on changes in population abundance and individual sizes in response to environmental change. These numerical and demographic shifts likely have behavioral and physiological mechanistic drivers that, if understood, could provide additional insights into the use of these species as bioindicators of habitat health. The Atlantic ghost crab, Ocypode quadrata, is a global bioindicator species of human disturbance on sandy shores. Individual size and population abundance of O. quadrata decline dramatically at sites with human disturbance, and the causes of this phenomenon remain unclear. Here, we test the hypothesis that individual and population‐level changes at disturbed sites reflect changes in burrowing behavior and energetics. Specifically, we examine whether or not the burrowing behavior (e.g., burrow fidelity and longevity) of O. quadrata changes because of human disturbance. We also examine energy required for burrowing by O. quadrata across different levels of human disturbance. We show that O. quadrata have the highest burrow fidelity and longevity at sites with low level of human impact, and weakest burrow fidelity and longevity at pristine sites. O. quadrata reduce the burrowing energy allocation by manipulating the burrow dimension and increasing the burrow longevity even under low levels of human disturbance. Overall, this study shows that human disturbances not only change the behavior of organisms, but also shift energetic balance. Our results support the use of a bioenergetic approach to better understand how human disturbances influence natural populations, and the specific use of this approach with this bioindicator species. Human disturbance alter the behavior and therefore shift the energetic balance of the organisms.
... Other emerging economic activities include charcoal burning which involves cutting of trees (Akrasi 2005) and salt production (Barry et al. 2005). Furthermore, coastal sand mining which mainly feeds the booming construction industry in the nearby cities of Accra and Tema, despite being illegal, is a common activity (Mensah 2002;Anim et al. 2013;Wiafe et al. 2013;Jonah et al. 2015). Indeed, this practice negatively influences the sediment budget and has contributed significantly to increased erosion along the coast (Appeaning Addo 2015). ...
Chapter
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The Volta Delta has fragile biophysical features affected by damming the Volta River and sand mining among other anthropogenic activities. The disrupted ecosystem adversely impacts livelihoods although efforts have been employed to reduce these impacts including both infrastructure and policies. This chapter describes the biophysical and socio-ecological evolution of the delta using data and information from sources including surveys, censuses and stakeholder engagements. It focuses on the interactions between biophysical processes and human activities. It further describes adaptation practices, migration and resettlement in response to these changes. Finally, the chapter explains governance and response to environmental challenges. Though no explicit delta policy exists, national policies and international treaties are gradually replacing customary laws and taboos to help manage and protect environmental resources in the delta.
... Among these, ghost crabs (genus: Ocypode) are most common (Barros, 2001;Gul and Griffen, 2018), predominantly due to their dynamic role in the beach ecosystem. Off-road vehicle traffic (Lucrezi et al., 2014;Moss and McPhee, 2006), camping (Schlacher et al., 2011), sand mining (Jonah et al., 2015), beach armouring (Lucrezi et al., 2009), and climate change (Schoeman et al., 2015) are some examples of studies utilising ghost crabs to measure environmental and ecological response to short-and long-term effects of anthropogenic actions. ...
... However, studies have revealed that sand mining negatively affects crustacean and fish populations due to removal of juveniles (e.g. Sheeba, 2009;Jonah et al., 2015). Although previously sand mining has been considered an extreme, but irregular event, it is now clear that it should be perceived as a regular stress towards which adaptive actions should be established. ...
... Ghost crabs have been widely used as a bio-indicator species to determine the ecological impacts of human use of sandy beaches globally ( [20] and citations) because of their strong responses to anthropogenic [23] and natural impacts [24], as well as their relatively large size and characteristic behaviors [11]. Also, their burrowing behavior provides an advantage for a low-cost and efficient monitoring technique [25] that has been applied to many sandy beaches in various locations around the world such as in North Carolina [4,24], Virginia and Mary- land [10] Ghana [26,27], Brazil [23], South Africa [28], as well as in Australia [11,[29][30][31]. ...
Article
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Ghost crabs have been widely used as a bio-indicator species of human impacts on sandy beaches to obtain reliable biological data for management and conservation purposes. Ghost crab population densities and individual sizes decline dramatically under human pressure. However, distribution within a beach and the factors that determine this distribution of ghost crabs is still an open question. These factors may provide valuable information for understanding human impacts on sandy beaches. Here we examine ghost crab burrows on 20 sandy beaches of South Carolina, USA under various levels of human impacts to understand the response in terms of spatial distribution of this species to human impacts. We also examine the burrow characteristics and environmental properties of the burrows to determine whether these factors alter burrow characteristics. We show that crabs on heavily impacted beaches altered their spatial distribution to mostly occupy the edges of impacted beaches. Further, this change in spatial distribution was influenced by the size distribution of the population on a beach (i.e. larger individuals occupy upper parts on the beaches). We also found that ghost crabs altered the morphology of their burrows on heavily impacted beaches. Ghost crabs create deeper, steeper and smaller burrows under human impacts. These patterns were also influenced by physical characteristics of the beach. Our results suggest that human impacts can directly influence the spatial distribution of ghost crab populations within a beach and therefore sampling at upper parts of the beaches overestimates the population density and individual sizes. Our results support the use of ghost crabs as indicator species in effective beach management, but suggest that assessments would benefit from examining the morphology and distribution of burrows as opposed to simply using burrow counts to assess the health of sandy shores.
... Based on the study by Thornton et al. (2006) sand mining was one of the main causes of erosion rates in bays' shoreline. Jonah, Agbo, Agbeti, Adjei-Boateng, and Shimba (2015) assessed the ecological impacts of beach sand mining on three beaches of Ghana over a four-month period. Lai et al. (2014) demonstrated extensive sand mining, which resulted in the wider and deeper outflow channel of a lake in China, caused the decline in the lake levels. ...
Conference Paper
Sand is a key ingredient for many industries, including concrete, glass, and electronics. Sand extraction is now exceeding fossil fuels and biomass. The absence of data on aggregates sand mining makes assessments difficult and has contributed to the lack of awareness about this issue. A sand governance business framework is developed applying the blockchain technology as the main goal of this study to regulate the sand extraction and trade. Blockchain technology provides a distributed concurrency monitoring system for the supply management. Agent-Based Modeling and Simulation (ABMS) as an effective bottom-up tool is applied to demonstrate the application of the model. The sand providers and users are modeled as a collection of autonomous decision-making entities called agents. The agents interact with each other, the regulators participate in making decisions on the basis of a set of rules that are defined within the blockchain network.
... Based on the study by Thornton et al. (2006) sand mining was one of the main causes of erosion rates in bays' shoreline. Jonah, Agbo, Agbeti, Adjei-Boateng, and Shimba (2015) assessed the ecological impacts of beach sand mining on three beaches of Ghana over a four-month period. Lai et al. (2014) demonstrated extensive sand mining, which resulted in the wider and deeper outflow channel of a lake in China, caused the decline in the lake levels. ...
Conference Paper
Full-text available
Sand is a key ingredient for many industries, including concrete, glass, and electronics. Sand extraction is now exceeding fossil fuels and biomass. The absence of data on aggregates sand mining makes assessments difficult and has contributed to the lack of awareness about this issue. A sand governance business framework is developed applying the blockchain technology as the main goal of this study to regulate the sand extraction and trade. Blockchain technology provides a distributed concurrency monitoring system for the supply management. Agent-Based Modeling and Simulation (ABMS) as an effective bottom-up tool is applied to demonstrate the application of the model. The sand providers and users are modeled as a collection of autonomous decision-making entities called agents. The agents interact with each other, the regulators participate in making decisions on the basis of a set of rules that are defined within the blockchain network.
... Based on the study by Thornton et al. (2006) sand mining was one of the main causes of erosion rates in bays' shoreline. Jonah, Agbo, Agbeti, Adjei-Boateng, and Shimba (2015) assessed the ecological impacts of beach sand mining on three beaches of Ghana over a four-month period. Lai et al. (2014) demonstrated extensive sand mining, which resulted in the wider and deeper outflow channel of a lake in China, caused the decline in the lake levels. ...
... Other emerging economic activities in the region are charcoal burning, which involves cutting of wood (Akrasi, 2005), and salt production (Barry et al., 2005). Coastal sand mining is a major activity practiced along the entire coast of Ghana and more widely in West Africa (Angnuureng, Appeaning Addo, and Wiafe, 2013;Anim, Nkrumah, and David, 2013;Appeaning Addo, Walkden, and Mills, 2008;Jonah et al., 2015;Wiafe et al., 2013). Although the practice is illegal, lack of enforcement has failed to stop this activity. ...
Article
Full-text available
Delta regions are dynamic and rich environments with diverse economic activities and are often densely populated.Deltas are being shaped by multiple drivers, including changes in sediment delivery to the coastal zone due to catchment changes, especially construction of dams on major rivers, intensified agriculture and/or aquaculture, mining, urbanisation, human-induced subsidence, climate change, and sea-level rise. These environmental challenges have significant implications for the livelihoods of delta residents. Thus, the integrated assessment of deltas is now attracting the attention of the scientific research community to analyse and understand deltas as coupled biophysical and socioeconomic systems. Most attention has been focussed on the major deltas. This review focusses on the smaller but regionally significant Volta delta, Ghana. Previous scientific studies are limited, with more focus upstream on the Volta River basin. Many contemporary problems are recognised in the Volta delta, especially erosion and flooding of the open coast fringe, such as at the town of Keta. However, these problems are treated independently, which may hinder identifying the root causes and the most effective solutions. Equally, the emergence of new problems might be anticipated and hence better managed or even avoided. This paper reviews the present delta with emphasis on biophysical processes and socioeconomic characteristics and considers in particular the current drivers and challenges.With this information, a research agenda will be established for a more systemic approach to understanding the Volta delta, including its residents and development.
... Representatives of the brachyuran subfamily Ocypodinae, family Ocypodidae (see Sakai & Türkay, 2013), commonly known as ghost crabs, are found on sandy beaches in the tropics and subtropics around the globe (Milne & Milne, 1946). The group is a promising bioindicator on sandy beaches because their assessment is non-invasive (indirect assessment using burrows) and distribution is worldwide, among other factors (Neves & Bemvenuti, 2006;Hobbs et al., 2008;Lucrezi et al., 2009;Jonah et al., 2015;Schlacher et al., 2016). ...
Article
Several studies have used the abundance of ghost crabs (Ocypodidae) as an indicator of human impacts on sandy beaches. Such studies have used assessment of burrows, even if the ratio between the number of burrows and crabs might not be consistent across beaches over time. The activity period of crabs frequently mentioned in such studies is always assumed to be during daylight. The few published studies on the daily activity of OcypodeWeber, 1795 preclude generalizations. Our study assessed the activity of O. quadrataFabricius, 1787 over six 24-hour cycles, using the most affordable filming devices on a restricted-access beach, thus excluding the influence of observers and tourists. The number of individual crabs and the time spent outside the burrows were calculated for every ten minutes of filming. These variables were assessed for correlation to each other, tidal height, temperature, and time of day. Both activity variables were significantly related to tide height, regardless of temperature or time of day. Peaks of activity in O. quadrata occurred during both day and night, and were mostly influenced by circatidal rhythms.
... Removal of habitat (Noriega et al., 2012), human trampling (Lucrezi et al., 2009), mining (Jonah et al., 2015), and vehicular traffic (Wolcott and Wolcott, 1984;Schlacher et al., 2007;Magalhães et al., 2009) are the main causes of damage to populations of ghost crabs, which are affected even when inside their burrows (Steiner, 1981). The effect of these impacts can be further amplified due to the seasonality of the reproductive cycle (Haley, 1972;Alberto and Fontoura, 1999;Graf et al., 2008;Oliveira et al., 2016) and the high life expectancy (circa three years) (Haley, 1972;Alberto and Fontoura, 1999), since once the populations are damaged, it is not known if they can quickly recover. ...
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Despite controversies, the non-destructive indirect method of counting and measuring the burrows of ghost crabs remains the best option for assessing the environmental quality of beaches. In order to better conserve and manage local populations and their environments, we evaluated the occurrence of the ghost crab Ocypode quadrata at 39 beaches, characterized according to the degree of human presence and by physical factors. Three main groups of beach variables-low, moderate and high – were identified according to the degree of human presence coupled with natural factors. The modes of access and cleaning best discriminated the beaches. Amongst physical features, only “trail beaches” and “restricted access beaches” significantly differed from other beaches. The drift and effluent beach zones with lesser human presence showed the highest numbers/densities of burrows. Older crabs, inferred by the largest burrows, were found less frequently at all beaches, the drift zone being the major aspect for their presence. Despite the great variability in the distribution of ghost crabs, they are sensitive to low environmental quality and their adequacy for assessing environmental quality was confirmed.
... Commonly known as ghost crabs due to their nocturnality and their generally pale colouration that blends in well with the sand (Karleskint et al. 2009), they are predators of small animals, including early juveniles of turtles, and generalist scavengers, whose cleaning activity makes them important components of sandy beach food webs (Trott 1999;Valero-Pacheco et al. 2007;Türeli et al. 2009;Lucrezi & Schlacher 2014;Marco et al. 2015). Being negatively affected by human activities, they also constitute valuable ecological indicators for quickly assessing the impact of disturbance on beach habitats (Branco et al. 2010;Schlacher et al. 2011;Noriega et al. 2012;Jonah et al. 2015;Lucrezi 2015). ...
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Ocypode cursor (Linnaeus, 1758) is the only Ocypode species present in the Mediterranean Sea, and one of the nine marine crustacean species protected in the basin. It is widely distributed in the eastern Mediterranean, but knowledge about its presence in the central Mediterranean is very limited so far. We hereby first document the established presence of O. cursor in the central Mediterranean (Sicily and Malta), backdate the known presence of this taxon in Italy, and offer preliminary observations on the main known Maltese population. In Sicily, O. cursor is distributed along most of the southwestern coast of the island of Sicily, whilst at least three beaches in the Maltese Islands are known to support populations of this species. The main Maltese population exhibits numerous similarities (e.g. burrow width, zonation along the beach) to another Mediterranean population studied in northern Cyprus, although occurring at lower densities. We conclude that the species has been probably present within the study area for a long period, but went undetected in view of the low population densities at which it previously occurred, the lack of a comprehensive census for the species within the same study area, and its nocturnal habits. The presence of this species in the central Mediterranean seems to be attributable to secondary natural spreading.
... Further, using ghost crabs (Ocypode species) as biological indicators, Jonah et al. [40] studied the ecological effects of beach sand mining in Ghana. They reported that ghost crab densities and sizes were negatively affected by both small-and large-scale beach sand mining. ...
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Increasing population levels, growing economies, rapid urbanization and changes in consumption patterns have increased the demand for raw materials such as base and precious metals, leading to growing concerns regarding their availability and the global efficiency of the mine supply chain. Mine tailings, consisting of process effluents that are generated in a mineral processing plant, are generally transferred to tailings ponds /impoundments to meet environmental regulations and site specific factors before discharge. Most mining activities induce an impact on their geo-chemical environment (e.g., water, groundwater) due to the presence of metal-rich tailing deposits. The need for a comprehensive framework for mine tailings management that promotes sustainable development is therefore becoming increasingly recognised by the mining industry. Therefore, for sustainable rehabilitation and disposal of mining waste, the sources and mechanisms of pollutant generation and their subsequent effect on environment and sustainable treatment methods is critical. This review includes information on different sources of mining waters and its effect on groundwater contamination and ecological effects. The review also encompasses a broad range of mine water treatment strategies available for innovative management of mining tailings with a specific emphasis on the role of nanoparticles in the management of mine waters. Keywords: Mining wastes; Water contamination; Ecological effects; Sustainable management; Nanoparticles
... The method of counting burrows considering occupation signs (Wolcott 1978), broadly used to guide the decision of whether burrows should be considered in ghost crab assessments, has proved to be prone to relevant bia ses, especially regarding comparisons among areas (Pombo & Turra 2013). Many studies of the effects of anthropogenic activities on ghost crab populations have been carried out recently using burrow counts (Barros 2001, Neves & Bemvenuti 2006, Hobbs et al. 2008, Jonah et al. 2015; therefore, understanding the potential divergence between conclusions derived from data on individuals and burrows, including res ponses to natural environmental features, becomes essential. ...
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Ghost crabs are important sandy beach dwellers whose bioindicator potential depends on a broader understanding of the relationship between environmental and biological parameters. We analyzed variations in ghost crab populations both directly (abundance, size, and sex ratio) and indirectly (burrow occupation rate and size differences between crabs and burrows) in relation to their across-shore distribution and their relationship with beach features. Nine pristine areas with distinct morphodynamics and wave exposure levels were sampled quarterly over 1 yr. Across-shore variability was recorded with larger crab sizes, lower occupation rates, and proportionally more females landwards. Storm surge period was a determining factor with respect to ghost crab populations, causing individuals to contract their distribution landwards and increases in burrow occupation rate and mean crab size estimates. Beach features influenced population parameters, with crab density and mean size tending to increase towards smaller grain sizes and with steeper slopes in the crab’s range of occurrence favoring crab abundance. Burrow occupation rate differed according to slope and crab density. Our results revealed an intrinsic variability of ghost crab populations over time and among and within beaches that may be a source of bias in environmental studies. Therefore, these phenomena should be considered in the design of monitoring strategies and impact assessment protocols. This study also emphasizes the need for a cautionary approach in data interpretation of crab number and size based on burrow estimates.
... Such eco-friendly construction will aid reduction of the environmental effects of sand mining and dredging such as coastal land recession, destruction of coastal ecosystem services, resuspension and dispersion of fine sand sediments and diminishing sand for exploitation (Jonah, Agbo, Agbeti, Adjei-Boateng, & Shimba, 2015;Kim, 2009;Kim & Lim, 2009;Lai, Chau, & Lorne, 2016;Liu et al., 2016;Tang, Zhang, & Xing, 2011;Thornton et al., 2006). ...
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Testing ghost crabs as indicator species usually fail to depict the mechanisms behind low burrow densities in urban coasts, neglecting individual traits as diagnostic variables. We conducted metaanalyses to compare the diameter of ghost crab burrow openings across gradients of human disturbances. Length–weight regressions were calculated, hypothesizing that crabs condition difer between beaches with high and low disturbance. The dataset regarding burrow opening diameter included 78 beaches (latitudes between 36° N and 30° S), and length–weight regressions were calculated based on 1,172 crabs data from 11 beaches (latitudes between 23° N and 30° S). Mean burrow diameter was smaller in high disturbance beaches, but a linear relationship with the level of human modifcation was not found in our gradient analysis. The higher the number of stressors acting locally, the greater the negative efects on burrow diameter. The body condition of ghost crabs was lower in high disturbance beaches; this result challenges the hypothesis that ghost crabs are smaller on disturbed beaches merely because individuals die before reaching adult ages. Our results have implications within the scope of ghost crab ecology, particularly regarding the inclusion of trait variation in investigations of mechanisms underlying spatial contrasts and in application of ecological-disturbance indicators.
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A problemática atual da produção e destinação inadequada de Resíduos Sólidos se tornauma ameaça devido ao tempo de persistência de seus componentes no meio, em especial ao ecossitema praiano.Este artigo tem o objetivo de compreender a dinâmica da distribuição dos resíduos sólidos na orla Ilha do Maranhão, situadano nordeste brasileiro e investigar os possíveis riscos ligados a fauna associada, com ênfase aoOcypode quadrata, um indicador de qualidade ambiental de praia bastante pesquisado em todo o mundo. Para tanto, amostras foram coletadas em 2 seções divididas em menor e maior fluxo antrópico, em 2 praias arenosas da ilha e em 2 períodos distintos, um chuvoso e o outro de estiagem. Os resultados mostraram uma predominância do plástico em relação aos outros materiais coletados nos períodos de chuva e de estiagem. Os processos de urbanização do litoral da ilha do Maranhão também mostraram influência sobre a frequência das tocas de O. quadratae sobre a dinâmica dos resíduos sólidos de forma geral, além de proporcionarem mudanças significativas no habitat natural das espécies estudadas afetando a sua abundância bem como as funções ecológicas que as mesmas desempenham
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We applied a rapid assessment methodology to estimate the degree of human impact of exposed sandy beaches in Ghana using ghost crabs as ecological indicators. The use of size ranges of ghost crab burrows and their population density as ecological indicators to assess extent of anthropogenic impacts on beaches was explored in this study. For each site, three transects were laid perpendicular to the shoreline over a 100 meter distance at 50 m intervals, i.e., at reference points 0, 50 and 100 meter points. Sampling locations were randomly selected along the three transects using a 1 m x 1 m quadrat. Measurements were done twice weekly for a period of four weeks. The results showed that even though the moderately disturbed beach had higher burrow density than the disturbed beach on the average, the difference is not statistically significant (T-test; p > 0.01). However, mean burrow diameter at the moderately disturbed site was statistically found to be significantly larger than for the disturbed site (T-test; p < 0.01). We conclude that burrow sizes is a good estimator for verification of human impacts of exposed sandy beaches. It confirms that burrow density even though an important factor, may not necessarily be a significant estimator of the impacts of human activity on beaches. On this basis, it appears that the estimations of the diameter of burrows of crabs of the Ocypode genera provides a rapid tool for impact verification of sandy beaches and for use in environmental quality monitoring of beach programs in coastal areas.
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ISSN 0749-0208. This study explores impacts of off-road vehicles on ghost crab populations as a measure of impact from recreational beach use on two beaches of the Cape Hatteras National Seashore and assesses the effectiveness of several alternatives for the use of off-road vehicles (ORVs) on the beach. Ghost crab population size and density have been used as indicators of the environmental quality of beaches and dunes. Data on the creation of an ''ORV corridor'' in which ORVs can drive on the landward portion of the berm, but not on the beach crest, indicate that it may be possible to preserve ghost crab populations on the beach while still permitting the use of ORVs. Closing the beach crest 24 hours a day may be the optimal solution for preservation of ghost crab populations. High-energy weather events, however, resulted in larger changes to the population dynamics of the ghost crabs. After storms, ghost crabs were able to (re)inhabit areas where their numbers previously had been reduced by the operation of ORVs. While temporary closures of the beach crest may be used to reduce the short-term impacts of ORVs on ghost crab populations on the outer banks of North Carolina, long-term impacts ultimately are controlled by the strength and frequency of storms that reset the system.
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The abundance, distribution and morphometry of Ocypode quadrata (Fabricius, 1787) burrows were analyzed in twelve sandy beaches of Pernambuco (NE-Brazil; 7º51'-8º45'30" S; 34º49' 35º06' W), with different grades of anthropic impact. This species is typical of the supralittoral fringe, which are the more impacted beach´s area due to the recreational activities. The density of O. quadrata burrows was higher at non-urban beaches, and near the strand line. The burrow diameter increases land ward, with strong correlation with organic matter mass. This analysis was a quick and easy way to identify anthropic impact, but other studies specifying the impacts and the local factors that are influencing the distribution of ghost crabs are necessary.
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Coastal erosion poses serious threat to life and properties along Ghana’s coast. This is because major industries, urban settlements, recreational facilities, heritage and conservation sites are located few metres from the coast. In spite of this threat, management strategies, both past and present, remain an “ad hoc” and site specific. Limited attention has been given to large scale assessment and investigation to detect the rate of coastal recession and the size of land lost to the sea to inform integrated management plan and to formulate sustainable management strategies to deal with the problem. This paper provides large scale assessment of coastal recession in Ghana through field investigation, applied coastal geomorphology and GIS techniques to selected case study areas. The assessment covered 203 km out of the 540 km coastline of Ghana. Results of the assessment indicate that coastal erosion is very substantial and wide spread along the coast, but the rate of recession varies across the entire coastline. Significant amounts of losses of settlements have been experienced in some localities in the eastern coast (Keta and Ada) and the central coast (Accra, Shama and Sekondi-Takoradi). In some areas, coastal defences have been built to reduce the impacts, yet many areas are still very vulnerable. Interestingly, the paper identified that the high rates of retreat recorded in many areas have yet to cause major risks in some local communities because of the presence of a buffer of largely undeveloped land that has existed historically between the shoreline and the developments. However, recent increase in coastal tourism in Ghana has led to “scramble” for purchase of these buffer lands for development, which increase the risk. Ghana has the opportunity to use education and land use planning to keep the coastline clear of major developments and avoid the temptation of engaging in costly cycle of development-risk-defence experienced in many countries including the UK and the Netherlands. The paper recommends that Ghana should adopt the UK SMP, which has progressively moved away from the traditional re-active and parochial approaches of providing localised hard-engineered coastal defence work to solve what was perceived to be a local problem, to a more pro-active and holistic approach that take full account of coastal dynamics, interrelationships of coastal systems, knock-on effects, environment concerns and developments at the backshore.
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SUMMARY This paper assesses the potential for the adaptation of UK Shoreline Management Planning to address Ghana's problems of coastal erosion and resultant shoreline retreat in an environmentally acceptable and sustainable way. Management strategies, past and existing, have largely focussed upon provision of hard protection at specific locations where risk levels to life and economic assets are high. There has been little commitment to the concepts of integration of management interventions with wider natural processes and longer-term sustainability. In most cases, such 'ad hoc' management interventions classically tend to stabilise the shoreline at the protected section and aggravate the situation elsewhere along the shoreline ("knock-on effects"). Such problems have occurred previously on many other developed coastlines leading in recent decades to more holistic and potentially sustainable shoreline management methods (Hooke, 1999). For example, UK shoreline management planning since the mid 1990s has achieved success in reducing the occurrence of "knock on effects." It has altered thinking away from the basic provision of defences towards a more holistic management of risks at the coast, setting out clearly locations where protection is likely to be required and others where alternative options are more sustainable. This paper reviews the progress achieved in the UK and assesses the extent to which the methods devised could be adapted towards the requirements of Ghana's shoreline. It concludes that many of the concepts and methods should be transferable provided that a sound understanding is developed of the physical coastal processes based on application of littoral cell and sediment budget methodology.
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The most common anthropogenic disturbance on exposed sandy beaches are recreational activities and destruction of sand dunes. To take decisions on manegment of this ecosystems, we must have effective environmental tools, to reduce impacts. The numbers of open burrows of the ghost crab Ocypode quadrata (Fabricius, 1787) should indicate the presence of animals, and in recent years it had been shown that this species is usefull as a tool in rapid assessment of human impacts. To test the hypotesis that anthropogenic impact on sandy beaches reduce the abundance of ghost crabs, the relative abundance (number of burrows/m2; N = 60) of the ghost crab O. quadrata were compared in three beaches of Santa Catarina Is., southern Brazil. In each one of the beaches, low and strong conditions of human impact were selected. Two levels in the intertidal were analysed, lower and upper midlittoral. The samples were taken in winter/2002 and summer/2003. In winter and summer there were significantly fewer burrows on that beaches with the higher levels of impact. Ingleses beach showed the higher abundances of the ghost crab in both winter and summer. In winter and summer there were significantly fewer burrows at Barra da Lagoa beach. In the summer the lower intertidal showed significantly higher abundances of the ghost crab. The results evidenced that Ingleses beach with high recreational impact had more ghost crabs, probably due to the nocturnal behavior and the fortuitous use of the food detritus left in the beach. In the beach with strong impact of cars and fisheries activities there were no ghost crabs. This study discuss the utility of the world-wide genus Ocypode for a rapid assessment tool of human impacts on exposed sandy beaches.
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Spatial distribution and activity pattern of Ocypode cursor (L., 1758) were studied for 2 years (2000-2001) in 40x15 m sand beach of Yumurtalik Bay in Turkey. Analysis of frequency distributions of the ghost crab population was based on indirect census, with burrow diameter measurement. Burrow diameter was a good estimator of crab size. Burrow diameter/carapace length and length/width relationships were estimated from samples obtained by excavating burrows and individual capture by trap. These relationship were adjusted by the following equations, respectively: BD = 0.25+1.13 CL; CW = 2.44+1.13 CL (BD is burrow diameter; CL is carapace length; CW is carapace width). Spatial distribution analysis was performed based on distance and altitude to water line. Most small burrows were found close to the sea, while larger burrows were mostly found in places higher up the beach. O. cursor was absent from the dry portion of the beach next to the dunes. The activity pattern showed that crabs are more activity during night than day-time. Burrow shape also was analysed. These burrows were in L-or j-shapes.
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Physical processes and biological data were collected and analyzed for eight sand resource areas on the New Jersey Outer Continental Shelf to address environmental concerns raised by the potential for mining sand for beach replenishment. Nearshore wave and sediment transport patterns were modeled for existing and post-dredging conditions, with borrow site sand volumes ranging from 2.1 to 8.8 × 106 m3. Wave transformation modeling indicated that minor changes will occur to wave fields under dominant directional conditions and selected sand extraction scenarios. Localized seafloor changes at borrow sites are expected to result in negligible impacts to the prevailing wave climate at the coast. At potential impact areas along the New Jersey coast, wave height changes averaged approximately ±3 to 15% when compared with wave heights for existing conditions. For all selected sand borrow sites offshore New Jersey, average variation in annual littoral transport was approximately 10% of existing values. Because borrow site geometries and excavation depths are similar to natural ridge and swale topographic characteristics on the New Jersey OCS, infilling rates and sediment types are expected to reflect natural variations within sand resource areas. Infaunal distribution and abundance correlated best with the relative percentages of gravel and sand in surficial sediments. In addition to sediment regime, other physical environmental differences between northern and southern portions of the study area also may have affected infaunal community patterns. Impacts to the benthic community are expected from physical removal of sediments and infauna. Based on previous studies, levels of infaunal abundance and diversity may recover within 1 to 3 years, but recovery of species composition may take longer. The nature and duration of benthic effects may differ with location of mined sites, due to physical and biological differences between northern and southern portions of the New Jersey shelf.
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We provide a brief synopsis of the unique physical and ecological attributes of sandy beach ecosystems and review the main anthropogenic pressures acting on the world's single largest type of open shoreline. Threats to beaches arise from a range of stressors which span a spectrum of impact scales from localised effects (e.g. trampling) to a truly global reach (e.g. sea-level rise). These pressures act at multiple temporal and spatial scales, translating into ecological impacts that are manifested across several dimensions in time and space so that today almost every beach on every coastline is threatened by human activities. Press disturbances (whatever the impact source involved) are becoming increasingly common, operating on time scales of years to decades. However, long-term data sets that describe either the natural dynamics of beach systems or the human impacts on beaches are scarce and fragmentary. A top priority is to implement long-term field experiments and monitoring programmes that quantify the dynamics of key ecological attributes on sandy beaches. Because of the inertia associated with global climate change and human population growth, no realistic management scenario will alleviate these threats in the short term. The immediate priority is to avoid further development of coastal areas likely to be directly impacted by retreating shorelines. There is also scope for improvement in experimental design to better distinguish natural variability from anthropogenic impacts. Sea-level rise and other effects of global warming are expected to intensify other anthropogenic pressures, and could cause unprecedented ecological impacts. The definition of the relevant scales of analysis, which will vary according to the magnitude of the impact and the organisational level under analysis, and the recog-nition of a physical–biological coupling at different scales, should be included in approaches to quantify impacts. Zoning strategies and marine reserves, which have not been widely implemented in sandy beaches, could be a key tool for biodiversity conservation and should also facilitate spillover effects into adjacent beach habitats. Setback and zoning strategies need to be enforced through legislation, and all relevant stakeholders should be included in the design, implementation and institutionalisation of these initiatives. New perspectives for rational management of sandy beaches require paradigm shifts, by including not only basic ecosystem principles, but also incentives for effective governance and sharing of management roles between government and local stakeholders.
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There is increasing concern regarding the impacts of recreational four-wheel driving (4WDing) on sandy beach environments. The ghost crab Ocypode cordimanus is a widely distributed Australian species that utilizes beaches and dunes for constructing burrows and for foraging. Comparisons of ghost crab abundances (using burrow counts) in areas “open” and “closed” to recreational 4WDing were conducted on exposed sandy beaches on North Stradbroke Island, off the coast of southeast Queensland. Beaches where recreational 4WD activity is present had significantly lower ghost crab abundances than beaches where it is absent. The most plausible reason for this difference in abundance is that ghost crabs are highly vulnerable to being crushed by beach traffic when feeding on the beach at night. To mitigate the impacts of recreational 4WDing on ghost crab population management intervention is needed. Possible changes to the management of recreational 4WD activity include the setting aside of areas free of recreational 4WD activity for the conservation of biodiversity, or a prohibition on driving on the beaches between dusk and dawn. There is also a need for a consistent and transparent approach in Queensland for quantifying and monitoring 4WD activity in sandy beach environments.
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Sandy beaches comprise one of the most important coastal resources worldwide, providing habitats to threatened vertebrates, supporting underappreciated invertebrate biodiversity, and delivering crucial ecosystem services and economic benefits to mankind. Monitoring of the natural resource condition of sandy beaches and assessments of the ecological impacts of human disturbance are, however, rare on sandy shores. Because a crucial step in developing beach monitoring is to identify and test biological indicators, we evaluated the utility of using population densities of ghost crabs (genus Ocypode) to measure how beach biota respond to human pressures. Densities of crabs--estimated via burrow counts--were quantified at two sites exposed to high and low levels of human disturbance on an urban beach in eastern Australia. Human disturbance consisted of pedestrian trampling and shoreline armouring which led to the loss of dune habitat. Overall, crab numbers were halved in disturbed areas, but contrasts between impact and control sites were not necessarily consistent over time and varied between different levels of the shore: stronger and more consistent effect sizes were recorded on the upper shore than further seawards. In addition to lowering crab densities, human disturbance also caused shifts in intertidal distributions, with a greater proportion of individuals occurring lower on the shore in the impacted beach sections. The number of visible burrow openings also changed in response to weather conditions (temperature and wind). We demonstrate that spatial contrasts of burrow counts are broadly useful to indicate the existence of a human-induced disturbance effect on urban beaches; we also highlight a number of critical, hitherto unknown, issues in the application of this monitoring technique; these encompass three broad dimensions: (1) a need for standardised protocols; (2) unresolved causal links between observed patterns and putative pressures; and (3) uncertainties of how organisms responds specifically to both natural and human changes of environmental conditions on sandy shores.
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The distribution and population density of the ghost crab, Ocypode cursor were studied in Yumurtalik Beach, Turkey during summer, 2009. Burrow densities of ghost crab were measured at three beach zones in relation to the Reference Datum (RD) with middle heights of 2, 4, and 9 m, which were located at medi-olittoral, supra-littoral, and sub-terrestrial fringe, respectively. Generally, individuals occurred above 1 m in height in relation to RD and peaked between 2 and 4 m. A range from 0 to 4.2 burrows/m² was obtained, and the total number of crabs on this beach (approximately is 2256 km²) ranging from 18.99 burrows/m² to 56.41 burrows/m². Significant differences in the mean burrow density were found among three zones. Low densities were recorded in the sub-terrestrial zone in September and peak density in the supralittoral zone in August. In general crabs followed a clumped dispersion on Yumurtalik beach. In total 986 burrow diameters were measured where diameter ranged from 3 to 97.8 mm. The results provided evidence that Yumurtalik Beach can provide suitable habitats for O. cursor population. Ocypode cursor is not vulnerable to the anthropogenic disturbances and environmental alterations found at Yumurtalik Beach.
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Rio Grande do Sul is the southernmost state in Brazil. Open sandy beaches dominate the 630-km long shoreline that is 76% still undeveloped. Less than 5% of the state's population (totalling 9.7 million people) live in coastal cities. However, the coastal population is growing faster than the state's average since 1990. Although intense erosion is widely accepted along the beaches of Conceicao lighthouse and Hermenegildo, the extent of erosion along the Rio Grande do Sul shoreline is still a controversial issue. Discussions arise from the contrasting results presented by studies addressing coastal erosion in Rio Grande do Sul. Recent DGPS monitoring indicates that about 80% of the Rio Grande do Sul shoreline is eroding; wave refraction studies indicate that it is mainly stable, and long-term coastal evolution modelling reveals a predominantly prograding shore for the last 5 ka. This work critically evaluates published data on long- and short-term causes of coastal erosion in Rio Grande do Sul, hi an attempt to highlight the unanswered questions that could minimize the debate. The analysis includes sea-level rise, concentration of wave energy due to large-scale coastal topography, sand deficit as the long-term causes of erosion, storm surges, concentration of wave energy due to small-scale submerged features, interference in the longshore sediment transport, and human activities as the short-term causes. Discrepancies in shoreline change results are a matter of the temporal scale in question and what are the causes that play a significant role in it. For coastal management purposes short-time events represent a far greater hazard than long-term trends. It is therefore reasonable to state that in order to support decision-making mechanisms in Rio Grande do Sul a better understanding of the relationship of storms, sand budget, and beach erosion is necessary.
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The most common anthropogenic disturbance on exposed sandy beaches are recreational activities and destruction of sand dunes. To take decisions on manegment of this ecosystems, we must have effective environmental tools, to reduce impacts. The numbers of open burrows of the ghost crab Ocypode quadrata (Fabricius, 1787) should indicate the presence of animals, and in recent years it had been shown that this species is usefull as a tool in rapid assessment of human impacts. To test the hypotesis that anthropogenic impact on sandy beaches reduce the abundance of ghost crabs, the relative abundance (number of burrows/m2; N = 60) of the ghost crab O. quadrata were compared in three beaches of Santa Catarina Is., southern Brazil. In each one of the beaches, low and strong conditions of human impact were selected. Two levels in the intertidal were analysed, lower and upper midlittoral. The samples were taken in winter/2002 and summer/2003. In winter and summer there were significantly fewer burrows on that beaches with the higher levels of impact. Ingleses beach showed the higher abundances of the ghost crab in both winter and summer. In winter and summer there were significantly fewer burrows at Barra da Lagoa beach. In the summer the lower intertidal showed significantly higher abundances of the ghost crab. The results evidenced that Ingleses beach with high recreational impact had more ghost crabs, probably due to the nocturnal behavior and the fortuitous use of the food detritus left in the beach. In the beach with strong impact of cars and fisheries activities there were no ghost crabs. This study discuss the utility of the world-wide genus Ocypode for a rapid assessment tool of human impacts on exposed sandy beaches.
Article
Ghost crabs are the largest invertebrates on ocean shores. They are globally abundant on many sandy beaches from the tropics to temperate latitudes. A defining ecological trait of the group is its fossorial habit: The crabs excavate deep, voluminous, and complex burrows, alternating between activity on the beach surface (e.g., foraging, mating, and dispersion) and underground microhabitats. Although not true land crabs, they have evolved a range of physiological, morphological, and behavioural adaptations to semi-terrestrial habitats and hence occupy a broad spatial gradient from coastal dunes to the swash zone. Ghost crabs are the fastest crustaceans on land and have acute senses of sight, smell, and hearing. Functionally, ghost crabs are pivotal in littoral food webs as mesopredators: They are often the apex invertebrate consumers on beaches while being predated by a diversity of reptiles, birds, and mammals that forage at the land-sea interface. As consumers, ghost crabs display extraordinary trophic plasticity, occupying several trophic levels, obtaining food through a variety of strategies, and consuming a wide diversity of prey. Their diet is broad-including predation on the eggs and young of sea turtles and shorebirds-and frequently encompasses efficient scavenging of animal carcasses.
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Mining of sand and stone from the coasts provides an inexpensive source of materials for the construction industry while providing income to contractors. However, these activities come at a cost to the coastal environment and pose a threat to the tourism industry along the Ghanaian coast. This paper identified the various types of coastal sand and stone mining activities, the level at which they are undertaken and covers the trends in coastal erosion along the coast of Cape Coast, Ghana. ArcGIS (ESRI, Redlands, CA, USA) and Digital Shoreline Analysis System (DSAS; ESRI) tools were used to determine short-term (2005–2012) coastline changes using 2005 and 2012 coastlines data. This study estimates that tipper-truck-based beach sand mining activities alone account for the loss of about 285,376 m/year of sand from the littoral zone in the Cape Coast area. It was also established that the average erosion rate for the Cape Coast area within the seven year period is 0.85 m/year with two areas recording high erosion rates of 4.35 m/year and 4.25 m/year. The study concludes that sand mining is the main cause of erosion along the coastline of Cape Coast.
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Like most coastlines the world over, Ghana's coast has been receding, requiring management interventions to protect coastal communities and assets of national importance. In order to adopt sound management interventions that would have a long lasting positive impact on the coastal zone, an understanding of the historic pattern of coastline change and coastal dynamics is required. This paper presents an analysis of the historic trends in coastline changes along the Elmina, Cape Coast and Moree area of Ghana using three shoreline data that spans a period of 38 years using ArcGIS and Digital Shoreline Analysis System tools. The study found that the Elmina, Cape Coast and Moree area had been eroding at a rate of 1.22 m/year ± 0.16 m from 1974 to 2012. It was identified that the widespread practice of beach sand mining in the area has significantly contributed to the erosion of several sections of the coastline. The study also identified the lack of an existing coastline management plan for Ghana's coast as the reason for the poor coastal erosion management techniques often used by coastal managers in response to the threat of coastal erosion, which eventually causes an acceleration of local erosion rates. The study finally makes a case for the adoption of a proactive and coordinated coastline management plan for Ghana's coast similar to that of the United Kingdom shoreline management plans because of the numerous known advantages.
Article
1. Adults of the burrowing crab Ocypode ceratophthalmus are nocturnal at Inhaca but some juveniles are active during the daylight. 2. The chelipeds are unequal in size in both sexes and the larger cheliped may be on either side of the body. Crabs with the larger cheliped on the right construct burrows which spiral to the right; and vice versa. A distinction is made between emergence holes and true burrows. 3. Burrows and emergence holes are distributed within a zone on the wave beach below H.W.S.T. level. The distribution of burrows within this zone changes from night to night and these changes appear to be related to differences in tidal cover between spring and neap tides. 4. Nocturnal activity may be considerably limited by the tides. There may be an aggregation of crabs on the wave beach or a migration on to the tidal flats. 5. Numbers along a stretch of shore were estimated from the number of emergence holes in the wave beach on one night following a spring tide. These indicated a population of x = 10.556+-3.834 per metre transect (1 m wide from H.W.S.T. to the lower edge of the wave beach).
Article
Biological responses of the dominant beach macro-invertebrates to beach nourish_ment.aI!4JmIldozing, two widely practiced stl'J.lcture-free methods.oL~p9!1_d5.QK-~0_~horeJine erosion, were evaluatedalong BogueBanks, North Car-olina. Sediments taken from maintenance dredging of a channel in Bogue Sound' andused for beach nourishment in a replicated design were substantially finer (3.67 vs 2.33 4» than those of untreated beaches and contained large concentrations of shell hash. In response to nonris:hmp.nt densities of Emerita taLpoida and Donax sI?~.!"~ lower by 86-99% on nourished beaches in early-mid July. 5-10 weeks after cessation of the nourishment Droie~. Beach hnl1~o7.ini done to augment the primary dunEt..!,,~duc.!.dth~~~th.ofl1!~ i!l.~~rtidaJbeach by about 7 m and replaced it with a wedg!LQ[~oJJ.~~~~{1Jt~~J~~n.lr.9~!Ltb..e-1o~e_r_be~ch,. In late July-early August about 3 months after termination of bulldozing, counts of active burrows of ~host crab~ Q.CY2Q(;iequAAr:~a'JI.ex~5~_5% loweron bulldozed beaches, with m<?stof the reduction oc~urrin2 on the 7 m of higb,J)ea~h occupied by .the,new:ly formed,dune face. Despite no detectable difference in slope of the lower beach, Emerita taLpoida densities were 35-37% lower on bull-dozed beach segments of 0.5-and 3-km, and, while Donax spp. exhibited no consistent residual response to bulldozing, two of three contrasts showed increased abundances of> 100% on bulldozed segments. Failure of Emerita and Donax to recover from nourishment b.Lmi!Ls...q,mID~~r wlten t!1.e~E1!YEL~_a,-pMmary-prey base fo!:.important_surf fishes, ghost crabs. and some shorebirds mav be a conS~Quence of the DOOrmatch in_mlJ1 si~8J!.(thigh~b,eJl_coIlte'"t of source ~ediments and/or extension of th~_.P!-9j~(;t~gJar iIl~o th~uval111-season. Effects of bulldozing on ghost crabs may conceivably be mitigated by measures to stabilize the dune face after bulldozing, but the effects on Emerita and Donax are not easily interpreted so potential mitigation measures for mole crabs and bean clams are unclear.
Article
Sand mining is a type of open-cast mining that provides material for the construction sector in Ghana. The construction sector in the coastal areas of Ghana relies heavily on coastal sand and pebbles in the building of houses, bridges and roads. Its contribution to Ghana's industrial output has increased from 17.4 per cent in 1986 to 20.8 per cent in 1993. However, the process of sand mining has accelerated coastal environmental degradation to an alarming rate in many areas. As a result the government has been compelled to spend millions of dollars to combat sea erosion. This paper examines the causes and effects of coastal sand mining in three communities in the Ahanta West District of Ghana. It argues that coastal sand needs to be exploited to satisfy human demands but this requires efficient and effective resource management to ensure sustainable development. It also calls for a concerted effort by policy makers, sand contractors, engineers, traditional rulers and local residents to find a solution to the coastal environmental crisis.
Article
Coastal management is being challenged to develop and implement measures that safeguard the ecological values of beach and dune ecosystems, particularly in urban settings. Monitoring the efficacy of such interventions requires reliable indicators of ecological change. Here, we tested the efficacy of ghost crabs (Genus Ocypode) to reflect changes in the degree of human beach use and habitat modifications. This was done across six beaches that differed in the degree of "urbanization" on Australia's Gold Coast, which ranks amongst the country's most intensively developed coastal areas. Population densities of crabs closely match the levels of beach use and human disturbance: Beaches with fewer visitors are less likely to be raked mechanically, thereby, supporting significantly higher numbers of crabs than do beaches with more visitors, which are cleaned more frequently. These spatial differences were consistent across eight surveys. Beaches backed by wider dunes that were more densely vegetated were better habitats than were the beaches with severely modified dunes. From a management perspective, our findings emphasize the critical role of maintaining—and possibly restoring—all remnant dune habitats. A premium on conserving dunes should be complemented by continued visitor management and new initiatives to develop and use more ecologically sensitive beach cleaning techniques.
Book
This volume discusses the role of humans in transforming the coastal landscape. The book details the many ways beaches and dunes are eliminated, altered and replaced and the differences between natural landforms and the human artefacts that replace them. Emphasis is placed on the importance of retaining naturally functioning beaches and dunes in ways that achieve natural values while accommodating development and use. The issues dealt with in this book will be of interest to practising coastal engineers and research scientists, as well as to planners and managers of coastal resources at all levels of government. It will be of particular value to investigators planning for the future of coastal development under accelerated sea level rise. The book will also be useful as a reference text for graduate and advanced undergraduate courses in geography, geology, ecology and other disciplines dealing with the interaction between science, technology and society.
Article
This paper reports on the disposal of diamond mine tailings on a Namibian sandy beach. Coarse sand in the tailings greatly increases the grain size of the affected parts of the beach and thereby provides the opportunity to assess the effects of changing sand grain size on a beach when other physical variables are kept constant. Elizabeth Bay (Namibia) is 4 km long and was originally composed of fine sand which, exposed to moderate to heavy wave action, produced a log spiral bay with a dissipative beach. Tailings disposal in the centre of the bay has increased mean sand particle size from original values of 110 to 160 mu m to present values of 500 to 800 mu m with a concomitant conversion of beach morphodynamic state from dissipative to intermediate. Surveys of the 2 ends of the bay, which are relatively unaffected by disposal, and of an undisturbed similar bay nearby revealed intertidal benthic macrofauna communities with 15 to 20 species occurring in high abundance (24120 to 129 276 m(-1)). In 3 transects in the affected area, species richness was 8 to 12 per transect and abundance was 640 to 4710 m(-1). Beds of the large sand mussel Donax serra have disappeared from the affected sector of the bay and peracarids typical of finer sands have been replaced by a more robust species. Regression analysis revealed Significant correlations between community parameters (species richness and abundance) and both beach slope and particle size; ANOVA confirmed the significantly lower abundances of fauna in the affected areas. Smothering effects appeared to be localised and limited. This study has supported the hypothesis that an increase in sand particle size (on a beach where tide range and wave energy have remained constant) results in a change in beach slate and a decrease in species richness and abundance.
Article
Potential and actual impacts of off-road vehicle (ORV) use on beach macroinvertebrates were examined on the Cape Lookout National Seashore (North Carolina). Mole crabs Emerita talpoida and coquinas Donax variabilis were not damaged. Ghost crabs Ocypode quadrata were completely protected by burrows as shallow as 5 cm, and therefore were not subject to injury during the day, but they could be killed in large numbers by vehicles while feeding on the foreshore at night. Ghost crab populations on the Seashore were large (10 000 km−1 of beach) and a small proportion of the population would be killed by a single vehicle pass. Nevertheless, predicted population mortalities calculated from observed kills of ghost crabs per vehicle-km ranged from 14–98% for 100 vehicle passes. Currently vehicle use on this beach is light and essentially none occurs on the foreshore after dark. Little impact on beach macroinvertebrates would be expected from this usage pattern. Actual impact on ghost crab populations, assessed by burrow censuses, was negligible. No differences were detected between heavy-use and light-use sites in total population size, average crab size or population change through the heaviest traffic season. However, increases in traffic to levels seen on other beaches, especially night driving, would probably have devastating effects on ghost crab populations. In heavily used areas, banning of ORVs from the foreshore between dusk and dawn may be required to protect this species.
Article
On exposed sandy beaches, the destruction of sand dunes and intense recreational activities are often the most common anthro-pogenic disturbances. It was proposed that such disturbances should have important e€ects on animals such as ghost crabs. Num-bers of burrows of ghost crabs, Ocypode cordimana, were compared between urban and non-urban beaches at di€erent levels on the shore. Overall, there were more burrows at high levels near sand dunes. There were signi®cantly fewer burrows at high levels on urban than on non-urban beaches. These di€erences are discussed in terms of destruction of habitat and possible changes in behaviour of crabs. This study suggests that the world-wide genus Ocypode may be useful as a tool in rapid assessment of human impacts on exposed sandy beaches. #
Article
The population density of the ghost crab, Ocypode quadrata and its activity pattern were studied in Montepio Beach, Veracruz, Mexico, which is considered a relatively undisturbed beach. Population density estimates were obtained using Wiegert's quadrat method in six samplings from June 2002 to March 2004, and the activity pattern was determined through direct observations during 24 h periods. Preliminary observations indicated that O. quadrata is absent from the dry portion of the beach next to the dunes and is present along an 18 m wide band adjacent to the high water mark, thus censuses were conducted on this portion of the beach. A range from 0.49 to 1.79 burrows/m2 was obtained throughout the censuses, and the total number of crabs on this beach (112,000 m2) ranged from 55,222 to 200,667. The relationship burrow diameter: carapace width was determined to verify that burrow diameter was a good estimator of crab size. Burrow diameter varied significantly among samplings. The activity pattern shows that crabs were active for 19-19.5 h during a 24 h cycle, the activity period mostly covering the night with two pulses of high activity during sunrise and sunset. Crabs remained inactive from 11:00 to 16:00 h, coinciding with the highest temperatures. La densidad poblacional del cangrejo fantasma Ocypode quadrata y su patrón de actividad fueron estudiados en la playa de Montepio, Veracruz, México, que se considera poco perturbada. Las estimaciones de densidad se obtuvieron utilizando el método de cuadrantes de Wiegert en seis muestreos entre junio de 2002 y marzo de 2004, y el patrón de actividad se determinó a través de observaciones directas durante periodos de 24 h. Observaciones preliminares indicaron que O. quadrata esta ausente de la porción seca de la playa adyacente a las dunas y que está presente sobre una franja de 18 m de ancho a lo largo de la playa a partir de la marca de marea alta, por lo tanto los censos se efectuaron en esta zona de la playa. Se obtuvo una variación de 0,49 a 1,79 hoyos/m2 en todos los censos, el número total de cangrejos en la playa (112.000 m2) varió de 55.222 a 200.667. La relación en diámetro del hoyo y ancho del caparazón se determinó para verificar que éste era un buen estimador de la talla de los cangrejos. El diámetro de los hoyos varió significativamente a través de los muestreos. El patrón de actividad mostró que los cangrejos estuvieron activos de 1919,5 h durante los ciclos de 24 h, el periodo de actividad cubrió la noche con dos pulsos de alta actividad al amanecer y al anochecer. Los cangrejos se mantuvieron inactivos de 11:00 a las 16:00 h, coincidiendo con las temperaturas más altas. La densidad poblacional del cangrejo fantasma Ocypode quadrata y su patrón de actividad fueron estudiados en la playa de Montepio, Veracruz, México, que se considera poco perturbada. Las estimaciones de densidad se obtuvieron utilizando el método de cuadrantes de Wiegert en seis muestreos entre junio de 2002 y marzo de 2004, y el patrón de actividad se determinó a través de observaciones directas durante periodos de 24 h. Observaciones preliminares indicaron que O. quadrata esta ausente de la porción seca de la playa adyacente a las dunas y que está presente sobre una franja de 18 m de ancho a lo largo de la playa a partir de la marca de marea alta, por lo tanto los censos se efectuaron en esta zona de la playa. Se obtuvo una variación de 0,49 a 1,79 hoyos/m2 en todos los censos, el número total de cangrejos en la playa (112.000 m2) varió de 55.222 a 200.667. La relación en diámetro del hoyo y ancho del caparazón se determinó para verificar que éste era un buen estimador de la talla de los cangrejos. El diámetro de los hoyos varió significativamente a través de los muestreos. El patrón de actividad mostró que los cangrejos estuvieron activos de 1919,5 h durante los ciclos de 24 h, el periodo de actividad cubrió la noche con dos pulsos de alta actividad al amanecer y al anochecer. Los cangrejos se mantuvieron inactivos de 11:00 a las 16:00 h, coincidiendo con las temperaturas más altas.
Article
Ten sandy beaches along the coast of northern Chile (20-23 degreesS) were studied in December 1998, to examine the distribution, abundance, and habitat characteristics of the crab Ocypode gaudichaudii. Beach width. slope, and intertidal fringes were identified, and Dean's parameter, describing beach morphodynamic status, was calculated. Crabs were collected and burrows and physical characteristics of the burrow zones analysed. The burrow zone extended primarily across the dry and retention zones. Physical properties across the burrow areas did not influence burrow characteristics. Significant differences in burrow density were detected both within and among the 10 sandy beaches. These differences were not related to morphodynamic beach types, but could be explained by related aspects, such as the height of the drift line, and the width and slope of dry and retention zones. We linked these results to behavioural and not just to physical causes.
Article
Sand mining is a type of open-cast mining that provides material for the construction sector in Ghana. The construction sector in the coastal areas of Ghana relies heavily on coastal sand and pebbles in the building of houses, bridges and roads. Its contribution to Ghana’s industrial output has increased from 17.4 per cent in 1986 to 20.8 per cent in 1993. However, the process of sand mining has accelerated coastal environmental degradation to an alarming rate in many areas. As a result the government has been compelled to spend millions of dollars to combat sea erosion. This paper examines the causes and effects of coastal sand mining in three communities in the Ahanta West District of Ghana. It argues that coastal sand needs to be exploited to satisfy human demands but this requires efficient and effective resource management to ensure sustainable development. It also calls for a concerted effort by policy makers, sand contractors, engineers, traditional rulers and local residents to find a solution to the coastal environmental crisis.
Article
Driving of off-road vehicles (ORVs) on sandy beaches is common and widespread, but is not universally embraced due to putative environmental impacts on beach biota. For ORVs to impact the beach fauna, traffic areas must overlap with faunal habitat: a fundamental pre-requisite for impact assessments but as yet un-quantified for sandy beaches. Thus, this study quantified the spatial and temporal patterns of ORV traffic on five Australian beaches, and measured the degree to which the distribution of intertidal macro-invertebrates overlaps with traffic zones. Traffic volumes on beaches can be considerable (up to 500 vehicles per day). The position of beach traffic across the beach-face is principally governed by tides and driver behavior. Despite driver education campaigns to the contrary, a considerable fraction of vehicles (16–67%) traverses the soft, upper shore near the foredunes. The majority (65%) of burrowing invertebrate species of the intertidal zone is directly exposed to traffic, save for species inhabiting the swash zone. Because beach traffic presents a formidable management challenge, a fundamental first step in identifying whether ecological impacts are indeed likely, is to assess the potential for spatial and temporal conflict between human pressures (e.g., ORVs) and biological resources (e.g., beach fauna). Although this potential is certainly substantial for sandy shores used by ORVs, the actual ecological impacts on the intertidal fauna can only be predicted in situations where the responses (e.g., direct mortality, behavioral changes) of individual species to beach traffic are known.
Article
From a physical geography perspective, tropical coasts are characterised by coral reefs, mangroves and carbonate beaches on atolls and low reef islands. They face threats not only from sea level rise, but also from human activities that destroy mangroves, degrade coral reefs and accelerate beach erosion. Physical conditions in the tropics are suitable for the ideal tourist beach. Conceptually, the tourist coast can be considered as the integration of a physical system (the coast) and a human system (tourism). Studies have been carried out on various types of tourist coasts in Southeast Asia. For many atoll island states, sea level rise is more than just a threat to their tourism; it also determines their survival. In recent years, assessments of their vulnerability and adaptation have favoured a more integrative approach of physical and human sciences. Hopefully, this should result in a better analytical tropical geography that could play an important role in reducing coastal erosion and assist the small island states.
Article
Estimation of absolute (or true) abundances of intertidal burrowing crabs is a difficult problem in some estuarine habitats because the nature of the substratum and behaviour of crabs can restrict researchers to the use of sampling methods which at best estimate only apparent, or relative, abundances. One method that has been used is to count open burrows to estimate population densities. This paper discusses the results of a test examining the validity of using burrows to estimate apparent abundances of a temperate ocypodid crab, Heloecius cordiformis. inhabiting mangrove forests of south-eastern Australia. Under appropriate circumstances, this method may provide a quick and reliable estimate of abundance of crabs.
Article
Sandy beaches face increasing anthropogenic pressures, with vehicle traffic being ecologically highly harmful. Ghost crabs (Fam. Ocypodidae) are conspicuous on many beaches, and they have been used as a bio-monitoring tool to measure the ecological responses to human disturbance. However, the mechanisms causing declines in crab numbers are unknown, yet conservation must target the actual impact mechanisms. Therefore, we quantified the magnitude and mechanisms of off-road vehicle (ORV) impacts on ghost crabs, addressing three key questions: (i) Does abundance of ghost crabs respond to traffic intensity?; (ii) Can burrows protect crabs from vehicles? and (iii) Can mortalities caused by vehicles contribute to population declines? ORV-impacts were measured on North Stradbroke Island (Australia) for Ocypode cordimanus and Ocypode ceratophthalma. Crab densities were significantly lower in areas subjected to heavy beach traffic, suggesting direct crushing by vehicles. Burrows only partially protect crabs against cars: all individuals buried shallow (5 cm) are killed by 10 vehicle passes. Mortality declines with depth of burrows, but remains considerable (10–30% killed) at 20 cm and only those crabs buried at least 30 cm are not killed by ORVs: these ‘deep-living’ crabs represent about half of the population. After crabs emerge at dusk they are killed in large numbers on the beach surface. A single vehicle can crush up to 0.75% of the intertidal population. While conservation measures should primarily regulate night traffic, our results also emphasise that the fossorial life habits of sandy beach animals cannot off-set the impacts caused by ORVs.
Article
Grain size analysis is an essential tool for classifying sedimentary environments. The calculation of statistics for many samples can, however, be a laborious process. A computer program called GRADISTAT has been written for the rapid analysis of grain size statistics from any of the standard measuring techniques, such as sieving and laser granulometry. Mean, mode, sorting, skewness and other statistics are calculated arithmetically and geometrically (in metric units) and logarithmically (in phi units) using moment and Folk and Ward graphical methods. Method comparison has allowed Folk and Ward descriptive terms to be assigned to moments statistics. Results indicate that Folk and Ward measures, expressed in metric units, appear to provide the most robust basis for routine comparisons of compositionally variable sediments. The program runs within the Microsoft Excel spreadsheet package and is extremely versatile, accepting standard and non-standard size data, and producing a range of graphical outputs including frequency and ternary plots. Copyright © 2001 John Wiley & Sons, Ltd.
Article
The aim of this study is to compare the density and vertical distribution of ghost crab Ocypode quadrata burrows at three beaches with different degrees of anthropic impact. In order to achieve this, 12 1 m2 quadrants were laid out at random daily on each beach, over a 100 m wide strip stretching from the dunes to the waterline, in order to estimate the density of the burrows. The results showed that the density of O. quadrata burrows was lower at beaches with higher anthropic impact – Tramandaí and Harmonia. Jardim do Éden beach, which suffers little impact, had the highest density of burrows. Vertical distribution of the burrows at Tramandaí beach was restricted by the presence of a strip which cars drive along. The burrows along this beach tended to be distributed over a strip where there are kiosks which offer protection from the traffic. At Jardim do Éden and Harmonia beaches, vertical distribution of the burrows was affected only by the dynamics of the rise and ebb of the waterline, caused by two storm events. The results showed that the density of ghost crab O. quadrata burrows is a tool of quick and easy use in diagnosing anthropic impact in coastal areas.
Article
Food habits and ecological rôle of the ghost crab. Ocypode quadrata ( Fabricius) on a North Carolina barrier beach have been investigated in field and laboratory studies. Despite previous reports that they are scavengers, the crabs spent little time in ureas where drifted material accumulated. Dead material accounted for less than 10% of the food in the field. The crabs did. however, give evidence of being facultative scavengers, readily consuming virtually any form of organic matter. Live prey, consisting almost exclusively of mole crabs, Emerita talpoida (Say), and coquina clams, Donax variabilis Say, made up more than 90% of the diet. Handling times indicate that about equal weights of E. talpoida and D. variabilis are consumed. Because of its higher caloric content E. talpoida provides ≈60% of the energy and D. variabilis ≈25%.The effect of O. quadrata on the prey species was assessed by comparing the estimated rates of its feeding (based on resting metabolism) with estimated production of E. talpoida and D. variabilis. Calculations indicate that ghost crabs consume most of the production of both species.Ghost crabs have essentially no terrestrial competitors or predators on the beaches concerned and the stability of this simple food web in such a physically unstable environment may be attributed to the flexible feeding behavior of the predators and their ability to endure long periods of starvation, and to the prey having high biotic potential and dispersal rates. Ghost crabs are the top carnivores in a simple, filter-feeding based food chain.
Article
Studies were conducted at Assateague Island, Maryland-Virginia, to determine the relative number of ghost crabs Ocypode quadrata Fab. on beaches subject to different recreational uses. The mean density of crabs per 0·1 ha plots was found to be 10 on an undisturbed beach, 19 on a pedestrian-impacted beach, 1 on a light off-road vehicle (ORV)-and pedestrian-impacted beach, and 0·3 in a heavy ORV-use beach. ORVs could be adversely affecting the crabs directly by crushing or burying them or indirectly by interfering with their reproductive cycle or altering their environment. Vehicular disturbance probably results in fewer crabs or no reproduction at all, with new inhabitants migrating from undisturbed areas. Pedestrians appear to have no harmful effects on ghost crabs; instead the crabs may be capitalising on the food scraps scattered across the beach by bathers.
Article
Thesis (M.Sc.)--College of William and Mary. Vita. Includes bibliographical references (leaves 106-109)
Coastal Erosion in Ghana: the Case of Elmina-Cape Coast-moree Area. A Thesis Submitted to the Department of Fisheries and Watershed Management
  • F E Jonah
Jonah, F.E., 2014. Coastal Erosion in Ghana: the Case of Elmina-Cape Coast-moree Area. A Thesis Submitted to the Department of Fisheries and Watershed Management. Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
Long-and shortterm coastal erosion in Southern Brazil
  • L S Esteves
  • Toldo Jr
  • E E Dillenburg
  • S R Tomazelli
Esteves, L.S., Toldo Jr., E.E., Dillenburg, S.R., Tomazelli, L.J., 2002. Long-and shortterm coastal erosion in Southern Brazil. J. Coast. Res. ISSN: 0749-0208 36, 273e282. Special Issue.
Population dynamics and reproductive aspects of the ghost crab Ocypoda saratan at Jeddah Coast, Saudi Arabia
  • M Al-Solamy
  • H Hussein
Al-Solamy, M., Hussein, H., 2012. Population dynamics and reproductive aspects of the ghost crab Ocypoda saratan at Jeddah Coast, Saudi Arabia. Glob. Adv. Res. J. Environ. Sci. Toxicol. 1 (4), 052e059.
Coastal Erosion Management in the Mediterranean: an Overview. Priority Actions Programme Regional Activity Centre
  • E Ozhan
Ozhan, E., 2002. Coastal Erosion Management in the Mediterranean: an Overview. Priority Actions Programme Regional Activity Centre, Ankara.
Sustainable Development of Nourished Shorelines
  • S Aarninkhof
  • J V Dalfsen
  • J Mulder
  • D Rijks
Aarninkhof, S., Dalfsen, J.V., Mulder, J., Rijks, D., 2010. Sustainable Development of Nourished Shorelines; Innovations in Project Design and Realization (The Netherlands).
Tide Tables. Ghana Ports and Harbours Authority
GHAPOHA, 2014. Tide Tables. Ghana Ports and Harbours Authority, Tema.