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Benthic surveys of the historic pearl oyster beds of Qatar reveal a dramatic ecological change
... This economic activity was important in the region until 1930s, when it began its decline due to the introduction of cultured pearls, to become almost fully extinguished by the 1950s, after an economic depression in the 1930s and World War II, together with the discovery of oil and gas deposits across the Gulf (Bowen 1951;Grandcourt 2012;Al-Matar et al. 1993). Furthermore, regional and global impacts such as overfishing, extreme environmental conditions, and other anthropogenic stressors, contributed to the collapse of the oyster fishery in the region (Smyth et al. 2016). Many of the current ruling families of the UAE owe their standing to the pearling industry, either directly or indirectly through taxation as the industry was a part of their journey or historical influence (Carter 2005). ...
... The proximity of some oyster habitats to the coast and the high productivity that characterizes these areas makes UAE's oyster habitats good traditional fishing grounds (Sheppard et al. 1992;Carpenter et al. 1997;Carter 2005;Al-Khayat and Al-Ansi 2008;Smyth et al. 2016;Bento et al. 2022). Fisheries around oyster beds and oyster reefs in the UAE are both recreational and commercial in their nature. ...
... 12.6 and 12.7). Oyster habitats occupy coastal and offshore areas in the Arabian Gulf, from Iran to Kuwait, the UAE and Oman (Somer 2003;Carter 2005;Al-Khayat and Al-Ansi 2008;Smyth et al. 2016) and are present in the east Gulf of Oman as well (Grizzle et al. 2018). In the UAE, oyster habitats occur on both coasts: the Arabian Gulf and the eastern Gulf of Oman (Grizzle et al. 2018). ...
Oyster habitats in the United Arab Emirates are highly diverse marine ecosystems with fascinating historical cultural and fisheries importance for pearls, but also for provisioning local people with food and materials for direct consumption and income. Their hard structure protects coastal areas and human populations and their assets, while their strong filtering activity promotes clean waters and healthy and productive marine ecosystems. Oyster habitats in the UAE occur on both the Arabian Gulf and Gulf of Oman coasts. They form oyster beds and oyster reefs and are distributed across coastal and offshore areas. These oyster habitats support hundreds of marine species that include valuable commercial species such as hamours (groupers), emperors (Lethrinidae), and snappers (Lutjanidae). The water quality in oyster ecosystems of Sharjah, Ajman and Umm al Quwain reflects good environmental conditions, yet the presence of microplastics in the sediment and oyster tissue evidence some pollution. Phytoplankton in these areas is diverse and includes several harmful algal bloom species. The current status and extent of oyster habitats in the UAE is known only for some emirates, but there is local scientific and management interest in addressing this gap for the conservation and restoration of these valuable habitats for the nation.
... The pearl oyster as a commodity represents one of the first globally mass-exploited natural resources, and the loss of the associated ecosystem services of the species is still not fully understood (Giraldes et al., 2019;Smyth et al., 2016). Basic information about marine biodiversity in the region, such as population dynamics, taxonomic updates, and drivers for biogeographic distribution, is still a work in progress (George, 2012;Giraldes et al., 2017aGiraldes et al., , 2016Naderloo, 2017). ...
... All specimens collected at the coastal sites were identified morphologically using pertinent taxonomy references (Bosch et al., 1995). Historical descriptions of pearl oyster bed locations (Fig. 1) and the current geographic descriptions of the offshore oyster bed locations in the Gulf identified the southwestern ecoregion as possessing the highest density assemblages of oysters (Carter, 2005;Smyth et al., 2016). Distribution of pearl oyster seascapes combined with marine boundaries (Fig. 1) within the Gulf identifies the Marine Zones of Qatar, UAE, and Bahrein as accommodating most of the pearl oyster biotope (Carter, 2005;Smyth et al., 2016). ...
... Historical descriptions of pearl oyster bed locations (Fig. 1) and the current geographic descriptions of the offshore oyster bed locations in the Gulf identified the southwestern ecoregion as possessing the highest density assemblages of oysters (Carter, 2005;Smyth et al., 2016). Distribution of pearl oyster seascapes combined with marine boundaries (Fig. 1) within the Gulf identifies the Marine Zones of Qatar, UAE, and Bahrein as accommodating most of the pearl oyster biotope (Carter, 2005;Smyth et al., 2016). Using georeferencing data in conjunction with current and historical maps made measuring the coastal benthic area suitable for oyster settlement possible. ...
... These conditions have produced several distinctive ecosystems; such as the characteristic Pearl oyster beds generated by the pearl oyster Pinctada imbricata radiata (Leach, 1814 and e.g. Smyth et al., 2016). During the early part of the 20th century, nearly half of Qatar population was involved in the pearl oyster industry, which at present-day prices would have been worth an estimated $2.5 billion per annum to the nation's economy (Carter, 2005). ...
... During the early part of the 20th century, nearly half of Qatar population was involved in the pearl oyster industry, which at present-day prices would have been worth an estimated $2.5 billion per annum to the nation's economy (Carter, 2005). However, as Qatar has prospered and developed, there has been a decline in the historical P. i. radiata oyster beds (Smyth et al., 2016). A survey in 2014 showed that only one out of the five studied sites in Qatar could still be characterised as oyster dominant, even though all five sites previously corresponded to places of highly productive oyster fishery (Smyth et al., 2016). ...
... However, as Qatar has prospered and developed, there has been a decline in the historical P. i. radiata oyster beds (Smyth et al., 2016). A survey in 2014 showed that only one out of the five studied sites in Qatar could still be characterised as oyster dominant, even though all five sites previously corresponded to places of highly productive oyster fishery (Smyth et al., 2016). These results highlighted the overwhelming likelihood that a combination of anthropogenic effects (such as overfishing, water quality shifts and petrochemical industry operations) have had a negative impact on the traditional Qatari pearl oyster beds (de Mora et al., 2010;Freije, 2015;Smyth et al., 2016;Al-Maslamani et al., 2018). ...
The pearl oyster Pinctada imbricata radiata is an iconic species in Qatar, representing an integral part of the nation's cultural heritage and one of the main economic foundations upon which the nation developed. During the early part of the 20th century, nearly half the Qatar population was involved in the pearl oyster industry. However, the fishery has undergone steady decline since the 1930s, and the species is now under threat due to multiple confounding pressures. This manuscript presents the first de novo transcriptome of the Qatari pearl oyster assembled into 30,739 non-redundant coding sequences and with a BUSCO completeness score of 98.4%. Analysis of the transcriptome reveals the close evolutionary distance to the conspecific animal Pinctada imbricata fucata but also highlights differences in immune genes and the presence of distinctive transposon families, suggesting recent adaptive divergence. This data is made available for all to utilise in future studies on the species.
... Annual sea temperature variations range from 14-36˚C with salinities averaging >39 psu and in some coastal regions >60 psu [1][2][3]. As a result of these harsh environmental conditions numerous unique ecosystems exist such as; the biogenic reef structures created by the pearl oyster Pinctada imbricata radiata (Leach, 1814) [4,5]. These reefs once occurred on an immense scale. ...
... Pliny the elder in 38 AD estimated that the oyster beds of the western Gulf covered an area of >1050 Km stretching from Sharjan (in the United Arab Emirates) to Qatif (in Saudi Arabia) [5,6]. However recent research has shown that overexploitation and environmental stressors have resulted in a considerable reduction of the ecotype throughout the region [4]. ...
... The study species Pinctada imbricata radiata is a recognized bioengineering ecosystembuilder responsible for the formation of numerous seascapes within the semi-enclosed region of the western Arabian-Persian Gulf [4,5]. A marine region with naturally occurring extreme environmental conditions [1][2][3] which can be dated from the mid-Holocene [25]. ...
A number of molluscs within the Class Bivalvia are defined by their ability to secrete fine silk like threads known as byssus which are used to anchor themselves to solid substrates. With relatively few exceptions the majority of these species remain in a sedentary state throughout their life attached via their byssal threads. However, observations of adult Pinctada imbricata radiata pearl oysters made during this study revealed this species’ ability to implement active movement. Byssal threads were secreted in a sequence of attachment and detachment phases, which resulted in the active displacement of the oyster. The oyster was observed, in the laboratory over a 9 day period, travelling a distance of 28cm in a horizontal path. After horizontal displacement, a vertical climbing phase was observed until the oyster reached the water surface at which point the byssus was discarded and the animal dropped, drifting in accordance with water current intensity. It is possible that these adaptations of byssal use are a result of environmentally induced evolutionary change within P. i. radiata.
... Although the pearl sites in Qatar have been considered as barren for years (First author pers. observation) Smyth et al. (2016b) discovered fragmented assemblages of mature P. radiata during biotope surveys, however no obvious signs of large-scale recruitment were detected. This raises the question as to why recruitment is failing despite the high fecundity of P. radiata and its non-discriminatory settlement. ...
... We set out to test the hypothesis that disturbance by the combined effects of retrieving static fishing gear using grapples and the seabed drag of strings of Gargoor could interfere with recruitment by causing newly-settled oysters to become detached from the substratum, as well as reducing the available areas for settlement by damaging habitat-forming biogenic reefs (Shester and Micheli, 2011). We revisited sites previously surveyed by Al-Madfa et al. (1998), Al-Khayat and Al-Ansi (2008) and Smyth et al. (2016b), to compare changes in the ecological status and population density of P. radiata over the last two decades in both fished and protected areas. ...
... Survey site selection was based on information provided by the Qatar Fisheries Department (QFD), findings from the Qatar University biotope mapping programme (Smyth et al., 2016b) and availability of previous survey data from 1992 (Al-Madfa et al., 1998(Al-Khayat and Al-Ansi, 2008. All the selected sites were once considered as prolific oyster beds or hairãt, as confirmed from archaic maps held by the QFD showing pearl fishing activities between 1830 and 35. ...
... The most widespread habitats offshore in the Gulf are muddy and sandy substrata (Sheppard et al., 2010;Feary et al., 2011), however these are interspersed by shallower limestone outcrops (Riegl, 1999). These shallower outcrops (locally known as 'hairãt') provide a hard substrate that is typically colonised by benthic epifauna including oyster beds and corals (Riegl, 1999;Sheppard et al., 2010;Smyth et al., 2016). There are no true coral reefs in the Gulf (Sale et al., 2011), rather corals form more of a veneer over the hard substrates present (Riegl, 1999;Sheppard et al., 2010;Feary et al., 2011;Sale et al., 2011). ...
... The demersal fish most commonly targeted by the Qatar trap fishery are Lethrinus and Epinephelus spp, which together account for around 29% of the annual total catch in Qatar (Stamatopoulos and Abdallah, 2016). Demersal fishing effort tends to be focused on traditional offshore fishing grounds which include the shallow 'hairãt' habitats, which are considered highly productive and support high benthic biodiversity (Smyth et al., 2016). Such characteristics would justify the inclusion these habitats in protected areas for both biodiversity conservation and spatial management of fish stocks. ...
... These mounds are mainly located in water depths of 10-20 m and are hereon referred to as 'shallow' sites. They have more consolidated coarse and rugose substrate, and are typically colonised by oyster bed or mixed reefs communities (Smyth et al., 2016). Of the sites included in this study, there is most live coral at the site of Halul Island (site S6), where five species have been recorded in recent surveys (Sheppard et al., 2010). ...
In order to implement spatial fisheries management in the Arabian Gulf, a better understanding of the distribution of fish in relation to benthic habitats is required. To facilitate this, hydroacoustic fish surveys were conducted over oyster bed/reef (“shallow”) and surrounding soft sediment (“deep”) habitats in the offshore central Gulf, within Qatari waters. Transects at ‘shallow’ sites had significantly higher mean fish density and biomass. Mean target strength of individual fish was also significantly higher at ‘shallow’ sites. Fish positions in the water column were examined and overall there was a closer association with the seabed at the ‘shallow’ sites. Larger fish were found significantly closer to the seabed than smaller fish across all sites, but more so at ‘shallow’ sites than at ‘deep’ sites. Acoustic return from the seabed was extracted to provide information on the habitat type both using ‘Sonar5′ and ‘Visual Habitat’ software. The different site categories (‘shallow’ vs ‘deep’) were significantly different for all the measures of acoustic habitat. Fish density was significantly related to ‘Visual Habitat’ data, more so than depth alone. Our results show that fish distribution in the offshore Gulf is associated with complex, shallow oyster bed/reef habitats, and this is particularly the case for larger demersal fish that are commercially exploited. The ability to characterise benthic habitats from acoustic fish survey data shows promise, with important time saving implications for the monitoring of marine environments and developing a spatial approach to fisheries management. This may include the identification of habitats with a relatively high density of larger fish for inclusion in candidate marine protected areas.
... Oyster habitats are important ecosystems that provide valuable ecological, economic, and social benefits for the UAE (Carter, 2005). These habitats serve as home and nursery grounds for commercially important fish, promote healthy coastal environments by improving the water quality and mitigating effects of eutrophication (Smyth et al., 2016) and contribute to shoreline stabilization which helps the creation of adjacent habitats such as seagrass beds and salt marshes (Baggett et al., 2015). The spatial distribution of this habitat was determined using a recent habitat mapping exercise (Mateos-Molina et al., 2020) and LEK. ...
... The information provided can also be used to identify trends and research priorities for better mapping of key ecological features in the future, as well as guide restoration efforts of habitats such as mangroves. Over the past decade there has been substantial degradation of some habitats as a result of changing climate conditions (Bento et al., 2016;Smyth et al., 2016) as well as urban development Burt, 2014), and future research should focus on developing habitat quality metrics to use in combination with these new maps. Such an approach would strengthen prioritization during spatial planning exercises, allowing better ecosystem-based management and the effective conservation of highly important, unique, or particularly vulnerable habitats. ...
The United Arab Emirates (UAE) host valuable coastal and marine biodiversity that is subjected to multiple pressures under extreme conditions. To mitigate impacts on marine ecosystems, the UAE protects almost 12% of its Exclusive Economic Zone. This study mapped and validated the distribution of key coastal and marine habitats, species and critical areas for their life cycle in the Gulf area of the UAE. We identified gaps in the current protection of these ecological features and assessed the quality of the data used. The overall dataset showed good data quality, but deficiencies in information for the coastline of the northwestern emirates. The existing protected areas are inadequate to safeguard key ecological features such as mangroves and coastal lagoons. This study offers a solid basis to understand the spatial distribution and protection of marine biodiversity in the UAE. This information should be considered for implementing effective conservation planning and ecosystem-based management.
... The United Nation's wealth report is increasingly emphasizing these non-economic values, and has suggested that conservation and safeguarding of ecosystems is important for general well-being of populations (UNEP, 2012). Coastal ecosystem benefits for amenity, culture and heritage, and other non-market benefits to society are drawing increasing attention in the Arabian region (Burt, 2014;Campbell et al., 2015;Gladstone et al., 2013;Smyth et al., 2016). However, to date economic valuation and non-market assessment has not been used to enhance environmental decision making in Qatar, and thus represents an excellent opportunity for targeted research. ...
... Outside of Doha, impacts from development have been more recent but equally alarming. Large-scale dredging of channels and ports to support growing industries and populations over the past decade has heavily modified the seabed and degraded coral reefs, seagrass meadows, oyster beds, mangrove stands and saltmarsh systems (Al Kuwari and Kaiser, 2011;Balakrishnan, 2012;Erftemeijer and Shuail, 2012;Richer, 2008;Sheppard et al., 2012;Smyth et al., 2016). Expansion of desalination and power facilities has increased discharge of salt brines and thermal effluents that represent a chronic stress to the fragile remaining coastal communities (Darwish et al., 2013;Richer, 2008). ...
The coastline of Qatar is a rich mosaic of productive and diverse ecosystems including mangrove forests, intertidal mudflats (sabkha), seagrass beds, and coral reefs. These ecologically interconnected ecosystems contain a substantial proportion of Qatar's total biodiversity, and support an estimated 97% of the >US$ 67 million in annual commercial fisheries, the highest value resource sector after petroleum. The extreme environmental conditions that characterize Qatar has led to fauna that are robust compared with other regions, but makes them highly sensitive to further pressure from anthropogenic stress. These vulnerable ecosystems have come under increasing pressure in recent decades as a result of dramatic expansion of coastal development, and threats to these ecosystems are likely to accelerate in the coming years as Qatar's economy and population continue to grow. Although environmental regulation had historically lagged behind the rapid pace of development, in recent years Qatar's leadership has aggressively expanded environmental management as a result of the growing awareness of the importance of coastal ecosystems. While these improvements are encouraging, management remains challenged by its current sectorial, project-driven focus. Ecosystem-based management (EBM) offers an opportunity to overcome these challenges by integrating impacts from across all major activities in multiple sectors and considering their cumulative effects on ecosystem services and products. While an EBM approach would require modest reprioritizing of existing processes and attention to addressing deficiencies in data needed to support decision making, it has the potential to greatly enhance the efficiency and effectiveness of coastal zone management. The article closes by summarizing a recently initiated research project on coral reefs and seagrass beds in Qatar which can serve as a model for development of the EBM approach for other coastal ecosystems in Qatar.
... It was also listed as a priority marine species under the Review of Marine Nature Conservation UK in 2007 (Lieberknecht, Mullier, & Ardron, 2014). In England and Wales, O. edulis has been accepted as a Feature of Conservation Importance (FOCI), and in Scotland it has been recognized as a Priority Marine Feature (PMF) (Hirst, Clark, & Sanderson, 2012;Shucksmith, Gray, Kelly, & Tweddle, 2014 (Kennedy & Roberts, 1999;Smyth, Al-Maslamani, Chatting, & Giraldes, 2016). ...
... The restrictions imposed because of low-density O. edulis larval recruitment have been reduced to some extent by the advances in hydrodynamic modelling. Oyster restoration stakeholders can now strategically position small, high-density brood-stock assemblages (100 000) in locations whereby the maximum larval dispersal potential can be predicted and concentrated settlements accommodated (Kennedy & Roberts, 1999;Kregting & Elsäβer, 2014;Laing et al., 2006;Smyth, Al-Maslamani, et al., 2016). An example of low-density brood stock productivity was documented in Strangford Lough in 1997 when an oyster marketing company over-summered approximately 125 000 O. edulis on the low intertidal of the north-western shore (Kennedy & Roberts, 1999). ...
Abstract
1. Since the collapse of the Ostrea edulis stock in the mid‐1800s the oyster has struggled to
re‐establish itself in self‐sustaining assemblages in Europe.
2. It is now widely recognized that O. edulis is an integral component of a healthy biologically
functional benthic environment and, as such, the restoration of wild stocks has become a
matter of urgency.
3. A major limiting factor in O. edulis stock recovery is the availability of suitable substrate
material for oyster larvae settlement.
4. This research re‐examined the larval settlement potential of several naturally occurring in‐situ
shell materials (e.g. Mytilus edulis, Modiolus modiolus, O. edulis), with the aim of determining
which shell material is the most appropriate for large‐scale restoration projects.
5. A positive correlation between available shell material and settlement was determined, and
analysis using PERMANOVA did not identify an attachment preference by O. edulis to any
particular shell type.
6. The findings suggest that if restoration efforts were coordinated with applied hydrodynamic
and habitat suitability modelling, in conjunction with naturally occurring shell substrate
concentrations, a cost‐effective recovery for O. edulis assemblages in the wild could be
achieved.
... For centuries, the economy of Qatar was based on the pearl oyster industry and fishing activity on the historically abundant oyster bed resources [3,4]. Notwithstanding its economic and social importance, the pearl oyster was not immune to environmental pressures, linked mainly to the rapid industrial and urban growth of the Gulf countries in recent decades, and a significant decline has been observed in the historical P. radiata oyster beds of Qatar [5]. The collapse of the pearl oyster ecosystem in Qatar and the Arabian Gulf threatens long-term biological and economic functionality in this shallow marine environment. ...
The pearl oyster Pinctada radiata (Leach, 1814), a crucial ecosystem builder in the Arabian Gulf, has experienced a significant decline, mainly attributed to anthropogenic pressures. This study aimed to characterize the reproductive cycle of P. radiata in Qatar and compare the current data with historical records in the region obtained between 1992 and 1993. From May 2020 to April 2022, we found a well-defined seasonal reproductive pattern, with a narrow peak spawning period in April. This observation stands out strongly from the previous recordings of 1992–1993 for the region, where spawning extended from May to August. The observed shift in the reproductive cycle coincides with a notable increase in the maximum sea surface temperature (SST), rising from 34 °C in August (1992–1993) to 37 °C in July (2020–2022), while the minimum SST remained stable at 15–16 °C in January during both periods. Furthermore, a contraction in the duration of the main spawning period was observed, with spawning now confined to an earlier and shorter timeframe. We propose that climate change, in addition to other environmental stressors, must have played a key role in modifying the reproductive cycle of the pearl oyster P. radiata in the Arabian Gulf. These findings highlight the importance of further monitoring reproductive dynamics in the context of climate change.
... Reefs in the Persian Gulf "failed" in 1770, 1790, 1878, 1900, 1905, 1950, and 2001-that is, there were not enough oysters on the ocean floor and some reefs had no oysters at all. 115 By 1907, the shallow waters in Mergui were "practically cleared of shell" and several formerly lucrative sites no longer hosted oysters. 116 Ceylon's fishery was so intermittent that sometimes a decade would pass before a reef had a sufficient number of oysters to allow for a successful harvest. ...
At the turn of the twentieth century, most of the world’s pearls were extracted from rich oyster and coral reefs on the northern Indian Ocean rim. This paper returns to the sites of extraction, studying imperial maps made from 1889–1925 to delineate oyster reefs on the seafloor. Building from the submarine up, I draw on environmental, animal, and history of science studies to explore the work of mapping oceanic, animate space. Attending to the role of divers, whose labor was required to make the seafloor visible, and the lifecycles of oysters, which changed over time, I argue that the seafloor represents a kind of unruly terrain , out of both the reach and control of imperial authorities. The paper’s final section meditates on reading humans as part of Indian Ocean landscapes and the possibilities this offers for further comparative, transnational work in a materialist vein.
... There is very little information documenting the decline of tropical oyster reefs outside South America. Some local declines have been documented for pearl oyster reefs in Sri Lanka and Qatar (Smyth et al., 2016;Ostroff, 2020), mixed Magallana belcheri and Magallana bilineata reefs in India (Alagarswami and Narasimham, 1973;Nagi et al., 2011), and Magallana bilineata and Magallana hongkongensis reefs in Hong Kong (Lau et al., 2020). Talonostrea salpinx reefs in Kuwait have also declined, with historical photographs showing how extensive and well developed the reefs once were (Al-Kandari et al., 2021). ...
Oysters are ecosystem engineers that form biogenic reef habitats in shallow coastal and estuarine waters and provide important ecosystem services. Widespread global declines have triggered a world-wide restoration movement, however a paucity of information on tropical oyster reefs has resulted in their exclusion from existing global assessments and, consequently, restoration. In this review we quantified the known global diversity of native reef-building oysters to compare diversity between temperate and tropical regions and assessed historic oyster reef presence and declines using two tropical case studies. We then summarised the biology, ecology, and benefits of tropical oyster reefs, which have four functional differences to temperate reefs: 1) the diversity of reef-building oysters is over four times higher in tropical than in temperate regions; 2) tropical reef-building oysters can have continuous spatfall throughout the year whereas temperate species have a defined season; 3) tropical reef-building oysters are generally faster growing than temperate reef-building oysters; and 4) tropical oysters commonly create mixed-species oyster reefs whereas temperate oyster reefs are generally formed by a single oyster species. There is evidence of unsustainable and destructive harvesting that has resulted in the decline of tropical oyster reefs, and these reefs should therefore be included in restoration efforts. We highlight knowledge gaps that can guide future research to develop important foundational information that will remove barriers to tropical oyster reef restoration.
... In addition, the Arabian Gulf has high levels of anthropogenic activity [28] [15] Such activities include reclamation, industrial and domestic sewage effluent discharge, as well as hypersaline water discharge from desalination plants [49] [12] [63]. The region has also experienced significant oil pollution as a consequence of regional conflicts [4] [58]. The Gulf's vulnerability to environmental stressors led to a series of regional actions in the 1980s [3] [16] and despite recent improvements, environmental regulation and management have typically lagged behind the rapid pace of development across the region. ...
Chlorine is extensively used as a powerful oxidizing agent in the countries surrounding the Arabian Gulf for water treatment and biofouling control. Its usage has been increasing significantly as demand for water grows considerably both in industry and for domestic use. This is due to the fact that it is a well-tested technology, has had a history of long-term worldwide industrial use and is of acceptable cost. While the Arabian Gulf waters support a range of coastal and pelagic marine habitats including mangrove forests, seagrass meadows and coral reefs, marine organisms in these waters are living close to their tolerance limits due to the extreme environmental stressors like temperature and salinity. Anthropogenic stressors such as chlorine may further exacerbate these natural stressors. In seawater, chlorine produces a mixture of hypochlorous acid and hypochlorite ion. These rapidly react with the bromide ion to form a mixture of hypobromous and hypobromite ion. Total residual oxidants formed by chlorination although are short lived and not persistent in seawater, they can be quite toxic. In the present study, toxicity data were obtained from 7 acute toxicity tests and 3 chronic toxicity tests using Arabian Gulf aquatic species from different trophic levels. The study also examined the effect of temperature and developmental stages on toxicity of chlorine. Furthermore, differences in the species sensitivity distribution between native and non-native species were compared. The main finding of the study showed that there was no significant difference between native and non-native species for chlorine toxicity. This would suggest that toxicity data from different geographic region can be used in deriving site- specific ecological risk assessment of chlorine. Keywords: Chlorine; Arabian Gulf; acute toxicity; chronic toxicity; risk assessment; species sensitivity distribution;
... and Fadlallah, 1991;Riegl and Purkis, 2012;Lin et al., 2021a). Current knowledge of habitat-forming organisms in the Arabian Gulf is limited to shallow intertidal and nearshore habitats (e.g., Basson, 1979a,b;Al-Yamani et al., 2014;John and Al-Thani, 2014;Niamaimandi et al., 2017;Smyth et al., 2016;Al-Abdulkader and Manikandan, 2019;Vaughan et al., 2019;Al-Ghunaim et al., 2020). Offshore areas around seamounts or islands where the bottom depth rises to near the surface provide a pseudo-nearshore environment (Sheppard et al., 1992(Sheppard et al., , 2010Burt et al., 2013Burt et al., , 2016 and in deeper offshore waters, the seabed is mostly composed of muddy habitats (Sheppard et al., 1992(Sheppard et al., , 2010. ...
Some macro-benthic organisms, such as macroalgae, bryozoans, sponges, and gorgonian corals, can create heterogeneous frameworks of habitats in the surrounding seabed. Such frameworks are important benthic ecosystems, but knowledge of them is fairly limited in the Arabian Gulf, the hottest sea in the world. In this study, the presence of macroalgae, bryozoans, sponges, and gorgonian corals was discovered in the seabed of the western Arabian Gulf. These organisms had positive co-occurrences with a preference for depths of 20 to 50 m. A hotspot of spatial distribution of macroalgae and bryozoans was also identified, located in the northwestern part of the Arabian Gulf. These habitat-forming organisms were distributed in a patchy pattern with low to moderate levels of density. They were positively associated with several commercial fishes, suggesting their importance to fishery. Our discovery extends the distribution of marine habitat-forming organisms into the offshore waters of the subtropical Arabian Gulf.
... These species, however, may be rare and do not have a resident population directly associated with the mangroves in the study area. Alternatively, the influence of historical and recent anthropogenic impacts in the region (Sheppard et al., 2010;Riegl and Purkis, 2012;Smyth et al., 2016) may have affected the population density of these species. ...
Many species of mangrove crabs are essential in the formation of mangrove ecosystems, and the bioturbation resulting from the excavation of their underground chambers is directly correlated with substrate oxygenation and carbon and nitrogen cycling within the ecosystem. This study examines the ecological and biogeographical characteristics of bioengineering crab assemblages that inhabit the environmentally challenging arid mangroves in the southwestern Persian-Arabian Gulf. Results demonstrated that a hyper-arid environment could directly impact crab diversity, reducing it to only one species per niche or coastal zone. A biogeographic comparison revealed an exclusive divergence of species composition in each Gulf region. Variations in seasonal temperatures were found to have a direct influence on the abundance of species and how the zonation is driven by sediment composition and trophic relations. Two crabs – Nasima dotilliformis in the salt march (supratidal zone) and Macrophthalmus (Mareotis) depressus in the intertidal – were considered to be the most influential functional species for this hyper-arid ecosystem due to their abundance, size, bioturbation potential and niche specificity for the intertidal zone. The limited number of species within the arid mangrove system emphasised the biogeographic pressure and inherent importance of the few active bioengineering species present and adapted to the harsh conditions, indicating that the dominant crabs within the biotope are directly related to the successful evolutionary establishment of these hyperarid mangroves. The study highlights important implications for future forest management strategies of the only forest ecosystem that tolerates the extremes of the southwestern Persian-Arabian Gulf area.
... Our biological model, P. i. radiata, a pearl oyster, belongs to the family Pteriidae. This species can tolerate a wide range of salinity and temperature (Al-Khayat and Al-Ansi, 2008;Gervis and Sims, 1992), it carries high traditional value in the region (Smyth et al., 2016), and is considered an important environmental indicator species (Al-Madfa et al., 1998). ...
A novel approach of combining manipulative field experiments and cytogenetic endpoints was used to assess the genotoxic impact of chemical contamination on a local model bivalve species, the pearl oyster -Pinctada imbricata radiata. Baseline levels of Polycyclic Aromatic Hydrocarbons (PAHs), Total Petroleum Hydrocarbons (TPHs) and trace metals were determined from surface sediments and pearl oyster tissue collected from 3 coastal locations in Qatar (Umm Bab, Dukhan and Al-Wakra). Initial aneuploidy –numerical chromosomal abnormality-level in oysters was also assessed during the baseline survey. The oysters’ ability to adapt to new sites, with distinct signatures in terms of chemical contamination, was assessed using a reciprocal transplantation experiment among the same 3 coastal locations, from February to April 2016. Significant differences in sediment contamination levels were detected among the 3 sites. TPHs were in higher concentrations at Umm Bab (western coast), while higher concentrations of metals and PAHs were found at Dukhan (western coast) and Al-Wakra (eastern coast), respectively. Oysters transplanted between locations showed lower levels of aneuploidy, relative to those kept in the original location (controls). Transplanted oysters, regardless of the contamination levels at the origin and destination, showed recovery from initial aneuploidy levels. Moreover, there was a larger percentage of aneuploid cells with chromosomal gain than with chromosomal loss in all treatments, which contrasts with the pattern usually observed in bivalves.
... In addition, it is a great potential natural resource for extraction of new marine drugs that was still undescribed in the defaunation scenario of the Anthropocene (McCauley et al., 2015). A real extinction risk for species inhabiting a region with a large anthropogenic pressure and considered a sea in decline with several ecosystem near a collapse (Sheppard et al., 2010;Smyth et al., 2016). ...
... Bivalves are able to tolerate a wide range of turbidity, temperature and salinity. Oysters, for instance, flourish from the high sea surface temperature of Qatari Waters, Arabian Gulf to relatively cold bays of Japan's waters (Gupta et al 2017;Smyth et al 2016). They are also widespread in estuaries, where turbid fresh water flows from rivers and streams, as well as in atolls or coral reefs, where the input of fresh water and suspended matter is limited (Andréfouët et al 2012;Rahman et al 2015). ...
Bivalves are filter feeders that play important roles in providing food for local communities, as well as promoting ecosystem stability. A study of bivalve diversity, distribution and abundance, was conducted in the intertidal area of Ngemboh, Gresik, East Java, Indonesia, in March 2018, during rainy season. The aim was to investigate the ecological indices, like species richness and species abundance, as well as the environmental parameters that might influence these bivalve communities. Three replicates of 15 m transect lines with five 1x1 m quadrant plots in each line were set up seawards, perpendicular to the coastline. All bivalves in the quadrants were counted. There were 278 individual bivalves from 11 species, 8 genera, and 5 families in the research areas. On average, the species abundance was 3.08 ind/m 2. The values for Shannon's diversity index (H'), Pielou's evenness index (J'), and Simpson's dominance index (C) were 1.16, 0.82 and 0.34, respectively. The Pearson correlation showed that the dissolved oxygen (DO) had a very high correlation with both species richness and diversity index (r=0.93 and r=0.92 respectively, P<0.01). Furthermore, Gafrarium pectinatum dominated 30% of the total abundance from all stations, suggesting this species to strongly shape the ecologicall indices in most research stations.
... In areas closer to the coast, patchy corals may colonise areas of hard substrate with better developed coral reefs occurring further offshore (Sheppard et al. 2010). Pearl oyster beds (Pinctada radiata oyster beds occur mostly on hard substrata at depths of between 12 to 16 m (Al-Khayat and Al-Ansi 2008) and sometimes within patchy coral areas (Smyth et al. 2016). The literature records more than 22 named offshore limestone outcrops with coral rich areas and oyster beds in Qatar waters alone and preliminary studies report they are associated with at least 158 and 189 species respectively, with many of the species common to both habitats (Al Al-Khayat 1999, Al-Khayat andAl-Ansi 2008). ...
As with many other regions in the world, more complete information on the distribution of marine habitats in the Gulf is required to inform
environmental policy, and spatial management of fisheries resources will require better understanding of the relationships between habitat
and fish communities. Towed cameras and sediment grabs were used to investigate benthic habitats and associated epifauna, infauna and fish
communities in the central Gulf, offshore from the east coast of Qatar, in water depths of between 12 and 52 m. Six different habitats were
identified: (i) soft sediment habitats of mud and (ii) sand, and structured habitats of (iii) macro-algal reef, (iv) coral reef, (v) mixed reef, and
(vi) oyster bed. The epibenthic community assemblage of the mud habitat was significantly different to that of sand, which in turn differed
from the structured habitats of coral reef, mixed reef and oyster bed, with the macroalgal assemblage having similarities to both sand and the
other structured habitats. Fish assemblages derived from video data did not differ between habitats, although certain species were only associ-
ated with particular habitats. Epibenthic diversity indices were significantly lower in mud, sand and macro-algal habitats, with no differences
recorded for fish diversity. Soft sediment grab samples indicated that mud habitats had the highest benthic diversity, with Shannon-Weiner
values of>4, and were more diverse than sand with values of 3.3. The study demonstrates high biodiversity in benthic habitats in the central
and southwestern Gulf, which may in part be due to the absence of trawling activity in Qatari waters. There is a strong influence of depth on
benthic habitat type, so that depth can be used to predict habitat distribution with a high level of accuracy. The presence of outcrops of hard
substrata creates a mosaic of patchy shallow structured benthic habitat across extensive areas of the offshore seabed. Such heterogeneity, and
the association of commercially exploited fish species with specific habitats, indicates that this region is well suited to a spatial approach to
fisheries management.
There is scarce information on the current importance of oyster beds as fishing grounds in the United Arab Emirates (UAE). This study aims to understand the socioeconomic value of oyster bed fisheries through questionnaire based surveys with fishers. Of 106 Emirati fishers interviewed, 67 % use oyster beds due to the proximity to shore, better catch quality, and species abundance. Oyster bed fisheries are recreational and commercial, with handline and fish traps the most common used gears. They provide food for local consumption and cash income. All respondents noticed a fish abundance and size decrease throughout the last decade. Fishers suggest establishing marine protected areas and updating fishing regulations to improve fishing stock status. During the Covid-19 pandemic, oyster fisheries increased, highlighting the value of these fishing grounds for food availability. These fisheries support the local economy and heritage, and urgently need management to ensure the protection of these often-overlooked habitats.
The book includes a historical account of the Arabian Gulf and summarizes the knowledge on the oceanography and marine biology of the Gulf. It highlights the challenges that are facing the Gulf and provides recommendations to sustainably conserve the Gulf resources.
The book presents updated information on the oceanography and marine biology of the Northwestern Arabian Gulf and presents major threats to the marine environment, as well as solutions and recommendations.
Restoration of degraded ecosystems is an important societal goal, yet inadequate monitoring and the absence of clear performance metrics are common criticisms of many habitat restoration projects. Funding limitations can prevent adequate monitoring, but we suggest that the lack of accepted metrics to address the diversity of restoration objectives also presents a serious challenge to the monitoring of restoration projects. A working group with experience in designing and monitoring oyster reef projects was used to develop standardized monitoring metrics, units, and performance criteria that would allow for comparison among restoration sites and projects of various construction types. A set of four universal metrics (reef areal dimensions, reef height, oyster density, and oyster size–frequency distribution) and a set of three universal environmental variables (water temperature, salinity, and dissolved oxygen) are recommended to be monitored for all oyster habitat restoration projects regardless of their goal(s). In addition, restoration goal-based metrics specific to four commonly cited ecosystem service-based restoration goals are recommended, along with an optional set of seven supplemental ancillary metrics that could provide information useful to the interpretation of prerestoration and postrestoration monitoring data. Widespread adoption of a common set of metrics with standardized techniques and units to assess well-defined goals not only allows practitioners to gauge the performance of their own projects but also allows for comparison among projects, which is both essential to the advancement of the field of oyster restoration and can provide new knowledge about the structure and ecological function of oyster reef ecosystems.
Coral Reefs of the Gulf: Adaptation to Climatic Extremes is a complete review and reference for scientists, engineers and students concerned with the geology, biology or engineering aspects of coral reefs in the Middle East. It provides for the first time a complete review of both the geology and biology of all extant coral areas in the Gulf, the water body between Iran and the Arabian Peninsula. In summer, this area is the hottest sea with abundant coral growth on earth and already today exhibits a temperature that is predicted to occur across the topical ocean in 2100. Thus, by studying the Gulf today, much can be learned about tomorrow’s world and the capability of coral reefs to adapt to climatic extremes. This volume provides the most authoritative and up-to-date review of the coral reefs in the Gulf. It can be used as a volume of general reference or as a textbook treating recent coral reefs. Written by local and international experts, the text is richly illustrated and will remain a standard reference for the region for decades to come. Contributions stretch from climatology through geology, biology, ecological modelling and fisheries science to practical conservation aspects. The book is useful for the technical expert and casual reader alike.
Decapods play a crucial role within the reef ecosystem and the development of scuba diving as a survey tool has allowed researchers the opportunity to study the decapod–reef relationship more comprehensively. The present study describes the differences in decapod assemblages in intertidal and subtidal zones at a tropical coastal reef system in the southwestern Atlantic Ocean and reports the importance of scuba diving as a survey technique. A total of 71 decapods were recorded during the research; 42 in the intertidal zone mainly formed by small endobenthic species and 39 in the subtidal zone primarily large species only 10 were found to frequent both sample zones. The study extends the range of Brachycarpusholthuisi Fausto-Filho 1966 in Brazil; and also demonstrates how scuba diving can be used to complement traditional methodologies and vice versa. The research shows the advantages of using scuba diving when studying trade endangered decapods, as the methodology allows access to cryptic habitats such as reef caves and underwater cavities which were inaccessible when using traditional techniques. In conclusion scuba diving represents a revolutionary non-destructive survey tool allowing the researcher to directly access a specific decapod assemblage in fragile reef environments and in protected marine areas.
Fouling organisms at twelve different pearl oyster beds in the Qatari waters of the Arabian Gulf have been examined and their degree of abundance was assessed. The majority of fouling organisms were algae, sponge , bryozoans, polychaetes, crustaceans , gastropods, bivolves, amphineurans, stelleroida , hydrozoans and ascidians. The highest number recorded of fouling species was at Akraiyash site with the highest diversity index, while the least number was reported in Um Al-Cheteb with the lowest diversity index>
Experiments were performed to investigate the impact of cockle population density Cerastoderma edule on the resuspension of naturally contaminated sediments collected from the Tamar estuary (SW England). Annular flumes generated tidal-current cycles for 7 to 9 d. The suspended sediment concentration (SSC) at peak flow increased 5-fold with increasing cockle population density, although the 2 highest densities yielded similar resuspension. Polycyclic aromatic hydrocarbons (PAHs) in the sediment were analysed by gas chromatography/mass spectrometry (GC/MS) at the beginning of the experiment, and in the water column of each flume after 2 and 6 d at both the maximum and minimum current speeds. At the end of each experiment sediment erodability was measured as a function of a stepwise increase in current speed. Sediment erosion increased up to 10-fold with increasing cockle population density. However, at the highest density the SSC was lower than that observed for the medium density, probably due to binding resulting from higher mucus secretion and pseudofaeces production. Current-induced resuspension of contaminated sediment was dependent on the density of the cockles, The correlation between the suspended sediment concentrations and the concentrations of PAH was weak for low molecular weight PAHs (phenanthrene and anthracene) due to their higher water solubility. In contrast, higher molecular weight PAHs (fluoranthene, pyrene, benz(a)anthracene and chrysene) showed a strong correlation with suspended particulates as a result of their higher hydrophobicity.
Stocks of the flat oyster (Ostrea edulis) have declined throughout their entire geographical range, principally due to anthropogenic overexploitation. Strangford Lough in north-east Ireland sup- ported a productive flat oyster fishery until the population crashed at the turn of the century. A survey of flat oyster resources in Strangford Lough has revealed that a small population still exists, although the origin of the stock is not apparent. Spatfall on natural cultch occurred at low levels in 1997. Natural recruitment of oysters in Strangford Lough may be limited by the availability of suitable substratum. Although the hydrographic conditions in the north of Strangford Lough are ideal for oyster bed reclamation, any development programme would require a large-scale accumulation of broodstock and suitable substratum.
Including ecology in biodiversity data management systems requires classifications of habitat terms that provide standard definitions and indicate their relationships. In addition to data- bases, a wide range of intergovernmental, conservation and fishery organizations require classifica- tions of habitats and ecosystems to enable comparisons between areas and organize information in maps and reports. However, all of the terms used to describe habitats are concepts whose definition is context-dependent. This paper reviews the key concepts and ecological perspectives involved in classifying marine 'habitats' and 'biotopes' (habitat plus its associated species) so as to advise how they may be used in data management systems. Classifications of biotopes provide practical mea- sures of biodiversity at the ecosystem level. As an example the habitat of a benthic invertebrate is very different in spatial scale to that of a parasite, plankton, tuna or whale. Habitats can be geophys- ical and/or biogenic, and may operate at different spatial scales. For example, aggregations of deep- sea coral colonies
Bottom trawling causes widespread physical disturbance of sediments in seas and oceans and affects benthic communities by removing target and non-target species and altering habitats. One aspiration of the ecosystem approach to management is to conserve function as well as biodiversity, but trawling impacts on benthic community function need to be understood before they can be managed. Here we present the large scale and long term impact of chronic trawling on the functional composition of benthic invertebrate communities using a comprehensive set of functional traits. The effects of chronic trawling disturbance on the functional composition of faunal benthic invertebrate communities, as sampled with a small beam trawl, were investigated at 6 to 13 sites in each of 4 contrasting regions of the North Sea. Each site was subject to known levels of trawling disturbance. Information on the life history and ecological function traits of the taxa sampled was translated into fuzzy coding and used to analyse the relationship between life history and functional roles within the ecosystem. Multivariate analyses were used to examine changes in the distribution of traits over gradients of trawling intensity. Changes in the functional structure of the community due to the effects of long-term trawling were identified in 3 of the 4 areas sampled. Filter-feeding, attached and larger animals were relatively more abundant in lightly trawled areas, while areas with higher levels of trawling were characterised by a higher relative biomass of mobile animals and infaunal and scavenging invertebrates. Univariate analysis of selected traits confirmed the patterns observed in multivariate analysis. These results demonstrate that chronic bottom trawling can lead to large scale shifts in the functional composition of benthic communities, with likely effects on the functioning of coastal ecosystems.
Disturbance due to trawling reduces the biomass and production of macro-infaunal invertebrate communities, implying that their total food-consumption rate will fall, and that production (carbon) reaching the sea floor will be processed by other animals that can withstand the effects of trawling. Meiofauna may be resistant to disturbance by trawling because they are likely to be resuspended rather than killed by trawls and because their short generation times would allow them to withstand elevated mortality. We used a BACI experimental approach to investigate the short-term effects of beam trawling on the diversity, biomass and community structure of meiofauna on real fishing grounds in the southern North Sea. Experiments at two locations showed that there were no short- to medium-term (1-392 days after experimental trawling) trawling impacts on meiofaunal diversity or biomass, but that there were mild effects on community structure. Any impacts due to trawling were minor in relation to seasonal changes in the meiofaunal communities. We assessed the power of our experiments to detect the effects of trawling and recorded a 44-85% chance of detecting a 50% change in species richness and a 65% chance of detecting an order-of-magnitude change in biomass. The power to detect changes in total abundance, however, was low (between 11% and 12% power for detecting a change of 50%). We suggest that meiofauna are more resistant to disturbance by beam trawling than are macrofauna and that they have the potential to withstand the effects of chronic trawling on real fishing grounds and to retain a key role in energy cycling.
Marine environments have suffered from a lack of quantitative methods for delineating areas that are sensitive or vulnerable to particular stresses, natural and anthropogenic. We define sensitivity as the degree to which marine features respond to stresses, which are deviations of environmental conditions beyond the expected range. Vulnerability can then be defined as the probability that a feature will be exposed to a stress to which it is sensitive. Using these definitions, we provide a quantitative methodology for identifying vulnerable marine areas based on valued ecological features, defined as biological or physical features, processes, or structures deemed by humans to have environmental, social, cultural, or economic significance. The vulnerability of the valued ecological features is a function of their sensitivity to particular stresses and their vulnerability to those stresses. We used the methodology to demonstrate how vulnerable marine areas for two groups of endangered whale species (inshore and offshore) could be identified with a predictive habitat model and acoustic stress surfaces. Acoustic stress surfaces were produced for ferry traffic, commercial shipping traffic, potential offshore oil production, and small-boat traffic. The vulnerabilities of the two whale groups to the four stressors considered in this example were relatively similar; however, inshore species were more sensitive to on-shelf, coastal activities such as offshore hydrocarbon production, ferry traffic, and small-boat traffic. Our approach demonstrates how valued features can be associated with stresses and the likelihood of encountering these stresses (vulnerability) in order to identify geographic areas for management and conservation purposes. The method can be applied to any combination of valued ecological features and stressors.
Reef coral communities in a non-reef setting on shallow, flat hardgrounds were quantitatively sampled in Dubai Emirate (UAE,
Southern Arabian Gulf) before and after a coral mass mortality in 1996. The coral fauna consisted of 34 scleractinian species
before and 27 after the event, which removed virtually all Acropora. No alcyonacea were recorded. Five community types were identified and characterized by the dominant species: (A) a sparse
Porites lutea community in sandy areas, (B) a dense Acropora clathrata community in areas with little sand, (C) a faviid community in muddy areas, (D) a Siderastrea savignyana community in sandy areas, and (E) a Porites compressa community, which built a framework in sandy areas. These communities are comparable to those described from other areas of
the Gulf, where a stable pattern of community differentiation appears to exist. The spatial distribution and dynamics of the
coral communities appears to be strongly influenced by mass mortality events recurring every 15 to 20 y. A combination of
extreme water temperatures and high sedimentation/turbidity appear to be the major cause of mortality.
Coastal sediments in sheltered temperate locations are strongly modified by ecosystem engineering species such as marsh plants,
seagrass, and algae as well as by epibenthic and endobenthic invertebrates. These ecosystem engineers are shaping the coastal
sea and landscape, control particulate and dissolved material fluxes between the land and sea, and between the benthos and
the passing water or air. Above all, habitat engineering exerts facilitating and inhibiting effects on biodiversity. Despite
a strongly growing interest in the functional role of ecosystem engineering over the recent years, compared to food web analyses,
the conceptual understanding of engineering-mediated species interactions is still in its infancy. In the present paper, we
provide a concise overview on current insights and propose two hypotheses on the general mechanisms by which ecosystem engineering
may affect biodiversity in coastal sediments. We hypothesise that autogenic and allogenic ecosystem engineers have inverse
effects on epibenthic and endobenthic biodiversity in coastal sediments. The primarily autogenic structures of the epibenthos
achieve high diversity at the expense of endobenthos, whilst allogenic sediment reworking by infauna may facilitate other
infauna and inhibits epibenthos. On a larger scale, these antagonistic processes generate patchiness and habitat diversity.
Due to such interaction, anthropogenic influences can strongly modify the engineering community by removing autogenic ecosystem
engineers through coastal engineering or bottom trawling. Another source of anthropogenic influences comes from introducing
invasive engineers, from which the impact is often hard to predict. We hypothesise that the local biodiversity effects of
invasive ecosystem engineers will depend on the engineering strength of the invasive species, with engineering strength defined
as the number of habitats it can invade and the extent of modification. At a larger scale of an entire shore, biodiversity
need not be decreased by invasive engineers and may even increase. On a global scale, invasive engineers may cause shore biota
to converge, especially visually due to the presence of epibenthic structures.
The feasibility of reliably estimating percent cover of coral reef benthos by video techniques is examined. Video belt transects were recorded within study areas on Davies and John Brewer Reefs in the central Great Barrier Reef during September 1988. Two years later in September 1990, the study area at Davies Reef was resampled concurrently by video and line intercept transects. Percent cover data of major coral growth forms and non-biotic physionomic attributes were extracted from video footage by scoring the identity of items located at even or random spaced points along the transect. A cost-benefit analysis which compared increases in precision with increases in sampling effort suggested that the optimum regime for analyzing 200 m long video transects was five subsamples of 110 random points or one sample of 550. This regime resolved both spatial variability at large and smaller spatial scales (between study areas and among transects) and temporal change (within a single study area over a two year period) for total live coral and individual growth forms. The strengths of the technique lie in its cost-savings in filed expenses, and in the production of a permanent visual record. The limitations of the technique lie in reduced taxonomic resolution when compared with hands on field techniques. The results suggest that for broad taxonomic categories of coral reef benthos reliable estimates of relative abundance can be obtained by video techniques.
This review examines the substantial changes that have taken place in marine habitats and resources of the Gulf over the past decade. The habitats are especially interesting because of the naturally high levels of temperature and salinity stress they experience, which is important in a changing world climate. However, the extent of all natural habitats is changing and their condition deteriorating because of the rapid development of the region and, in some cases from severe, episodic warming episodes.Major impacts come from numerous industrial, infrastructure-based, and residential and tourism development activities, which together combine, synergistically in some cases, to cause the observed deterioration in most benthic habitats. Substantial sea bottom dredging for material and its deposition in shallow water to extend land or to form a basis for huge developments, directly removes large areas of shallow, productive habitat, though in some cases the most important effect is the accompanying sedimentation or changes to water flows and conditions. The large scale of the activities compared to the relatively shallow and small size of the water body is a particularly important issue.Important from the perspective of controlling damaging effects is the limited cross-border collaboration and even intra-country collaboration among government agencies and large projects. Along with the accumulative nature of impacts that occur, even where each project receives environmental assessment or attention, each is treated more or less alone, rarely in combination. However, their combination in such a small, biologically interacting sea exacerbates the overall deterioration. Very few similar areas exist which face such a high concentration of disturbance, and the prognosis for the Gulf continuing to provide abundant natural resources is poor.
Overfishing is a major environmental problem in the oceans. In addition to the direct loss of the exploited species, the very act of fishing, particularly with mobile bottom gear, destroys habitat and ultimately results in the loss of biodiversity. Furthermore, overfishing can create trophic cascades in marine communities that cause similar declines in species richness. These effects are compounded by indirect effects on habitat that occur through removal of ecological or ecosystem engineers. Mass removal of species that restructure the architecture of habitat and thus increase its complexity or influence the biogeochemistry of sediments could have devastating effects on local biodiversity and important water–sediment processes. The possible overexploitation of engineering species requires more attention because the consequences extend beyond their own decline to affect the rest of the ecosystem. This is particularly problematic in the deep ocean, where oil and gas exploration and fishing pressure are likely to increase.
A series of experiments investigated the potential role of microbial mats in nutrition of the early settlement stages of Penaeus semisulcatus. From 3 days post-metamorphosis, the microbial mat supported high growth and survival rates in postlarvae, equivalent to that supported by a control diet of Artemia nauplii and mussel. Examination of gut contents indicated that benthic postlarvae feed indiscriminately on the microbial mat. However, when postlarvae were fed separated size-fractions of the microbial mat, only the fraction containing a high concentration of infauna (mainly nematodes) was able to support the same growth as intact microbial mat. This appears to be due to the low nitrogen content (0.4-0.9 mmol g-1) of the various size-fractions, compared to that of infauna (4.0 mmol g-1). The stable isotope composition of the dietary size-fractions and postlarval shrimp tissue supports the hypothesis that the shrimp assimilated C and N primarily from the associated infauna. This may be due to selective feeding that is not apparent from stomach contents, due to rapid digestion of fauna soft tissues, or to differential assimilation of infaunal prey relative to other microbial mat components. The results demonstrate that microbial mats may support survival and growth in early-stage penaeid shrimp postlarvae on intertidal mud flats.
The small non-commercial oyster Ostrea stentina co-occurs with commercially important Ostrea edulis in the Mediterranean Sea, yet its disposition with respect to the destructive pathogens Bonamia ostreae and Marteilia refringens is unknown. We began an evaluation of the Bonamia spp. infection status of O. stentina from Hammamet, Tunisia, in June 2007 using polymerase chain reaction diagnostics followed by histology and in situ hybridization. Of 85 O. stentina sampled, nine were PCR-positive for a Bonamia sp. using a Bonamia genus-specific assay; of these nine, one displayed the uninucleate microcells associated with oyster hemocytes characteristic of Bonamia spp. There was no associated pathology. DNA sequencing of the parasite from this one infected individual revealed it to be of a member of the Bonamia exitiosa/Bonamia roughleyi clade, an identification supported by positive in situ hybridization results with probes specific for members of this clade, and by the morphology of the parasite cells: nuclei were central, as in B. exitiosa, not eccentric, as in B. ostreae. There is no basis for identifying the Tunisian parasite as either B. exitiosa or B. roughleyi, however, as these species are genetically indistinguishable. Likewise, there is no basis for identifying any of the other Bonamia spp. with affinities to the B. exitiosa/B. roughleyi clade, from Argentina, Australia, Spain, and the eastern USA, as one or the other of these named species. Though they are clearly distinct from Bonamia perspora and B. ostreae, justification for drawing species boundaries among the primarily austral microcells with affinities to B. exitiosa and B. roughleyi remains elusive.
Moreno, M., Vezzulli, L., Marin, V., Laconi, P., Albertelli, G., and Fabiano, M. 2008. The use of meiofauna diversity as an indicator of pollution in harbours. – ICES Journal of Marine Science, 65: 1428–1435.
We assessed several meiofaunal indices in sediments of three Mediterranean harbours differing in environmental contamination to evaluate their usefulness as indicators of pollution and to identify those that best described environmental quality. In general, indicators based on meiofaunal taxa demonstrated a significant correlation with the concentration of contaminants, especially the polycyclic aromatic hydrocarbons (PAHs). Nematode genus-based indicators correlated with contaminant concentrations at similar levels of significance, suggesting that a high taxonomic resolution does not improve the information content of meiofauna diversity indicators for assessing the environmental quality in these harbours. Notably, environmental variables that affect meiofaunal and nematode assemblages (e.g. water depth, grain size, and food sources) demonstrated a low spatial and temporal variability in the harbours investigated and did not represent important confounding factors. We conclude that the application of meiofaunal and nematode indices can be a useful tool for assessing the environmental quality of harbour ecosystems.
The aims of the present investigation were to study the feature of biotic environment of oyster beds and to study quantitatively the biodiversity of fauna and flora living within these habitats. Eighteen selected oyster beds, within the Exclusive Economic Zone of Qatar were investigated by scuba diving. Most of the oyster beds were found in the area with sandy-rocky and Coral blocks bottom forms. Pearl oysters abundance varied widely between the different beds and within the same beds due to the variations in the bottom substrates. The associated biota was composed mainly of Algae (4%), Porifera (3%), Cnidaria (8%), Polychaeta (4%), Echinodermata (13%), Mollusca (55%), Chordate (2%) and Crustacean (11%). The comparison of our findings on the occurrence and distribution of marine biota to previous studies has shown similarities between Qatar and other Gulf States particularly Saudi Arabia and Bahrain.
We employ a three-dimensional hydrodynamic model (COHERENS) in a fully prognostic mode to study the circulation and water mass properties of the Persian Gulf – a large inverse estuary. Our findings, which are in good agreement with observational evidence, suggest that the Persian Gulf experiences a distinct seasonal cycle in which a gulf-wide cyclonic overturning circulation establishes in spring and summer, but this disintegrates into mesoscale eddies in autumn and winter. Establishment of the gulf-wide circulation coincides with establishment of thermal stratification and strengthening of the baroclinic exchange circulation through the Strait of Hormuz. Winter cooling of extreme saline (>45) water in shallow regions along the coast of United Arab Emirates is a major driver of this baroclinic circulation.
The study was aimed at learning lessons from historical translocations of the European native oyster, Ostrea edulis and contributing to the debate on best practice for restoration projects. An extensive literature review of over 100 documents spanning 200 years was conducted to look at translocations of Ostrea edulis and investigate temperature related reproduction. Differences among geographical locations were assessed by multivariate analysis of reproductive data. Translocations of hundreds to millions of Ostrea edulis have taken place over the past 200 years, mainly for commercial purposes. Movements were either single actions or regular events over many years. Whilst 75 separate records of Ostrea edulis movements from within European waters were documented, it is likely that many more took place. Introductions have also been made outside Europe for aquaculture; translocations back to European waters, have led to the introduction of pathogens. The timing and duration of reproductive periods and spawning temperature thresholds of Ostrea edulis in the middle region of its distribution range were similar. Cluster analysis of documented periods of reproduction indicated that introduced and restocked populations clustered with their putative donor populations. Whilst the Irish production areas clustered together, reproductive cycles in Lough Foyle in the northwest of the island of Ireland showed greater similarity to the now extinct deeper water English Channel beds. Historically, the ability of oysters to breed after translocation was not considered important. Successful reproduction and recruitment is however fundamental to conserving the species. Where translocation of stock is used to restore Ostrea edulis in areas where it has been extirpated, this study suggests that restocking should be at high densities and carried out over several years and that harvesting should be restricted to increase the chances of establishing self-sustaining populations.
The reproductive system in bivalves is simple. The paired gonads are made up of branching tubules, and gametes are budded off the epithelial lining of the tubules. The tubules unite to form ducts that lead into larger ducts, which eventually terminate in a short gonoduct. Fertilization is external and the gametes are shed through the exhalant opening of the mantle, except in the case of brooding bivalves. The majority of bivalves are dioecious, that is the sexes are separate, and there are usually equal numbers of males and females. The act of settlement involves descent from the plankton to the sea bottom, followed by a sequence of swimming and crawling behaviour that culminates in attachment once a suitable substrate is chosen. Settlement is generally difficult to measure in the field and so it is usually inferred from recruitment data measured some days, or even weeks, after settlement has actually occurred.
The pearl oyster. Pinctada radiata, represents the most abundant marine bivalve species in Qatari waters. The population parameters of this species were investigated and compared to those obtained previously from both the Mediterranean and Red seas. Four age groups with mean lengths of 56.75, 65.84, 77.54 and 84.66 mm were obtained for P. radiata from Qatari waters. The values of asymptotic length, Brody's growth coefficient and growth performance index were 132.18 mm, 0.34 y-1 and 1.77 respectively, while the total mortality coefficient equals 2.47 y-1. The morphometric relationship between the total weight and dorso-ventral measurement was determined to be W = 0.0002606 (DVM)2.90707.
The Olympia oyster of Washington State, USA (Ostrea lurida dagger) was heavily exploited (1850 to 1940), declined dramatically. and has subsequently failed to recover, although it Still Supports small aquaculture operations. This paper documents the distribution and abundance of O. lurida in one of the last remaining locations where it forms extensive beds: the North Bay Oyster Reserve in South Puget Sound. We monitored recruitment every 2 wk between May and September 2004 and found a small recruitment peak in late July, Which Was Much later than reported for these oysters when they were abundant throughout Puget Sound, We also experimentally tested two factors that could influence recovery: tidal elevation and substrate type. We established 1 m(2) plots at three tidal elevations (-0.3, 0, +0.3 m MLLW) with six Substrates: bare. gravel. Crushed shell of Crassostrea gigas (Pacific oyster), whole C. gigas shell, whole shell of O. lurida, and live O. lurida. The Plots Were Set LIP May 21 2004 and measured for recruitment oil October 16, 2004 and April 11, 2005 by collecting material from a 0.0125-m(2) area of each plot. Recruitment improved at low tidal elevations and differed across substrates. Ostrea lurida shell consistently provided a better recruitment substrate than gravel or bare plots, but shell treatments could not be distinguished statistically. Postrecruitment mortality Occurred in all treatments; however the rates of mortality were not significantly different by elevation or substrate treatment. Habitat restoration (low intertidal and subtidal shell areas) should promote the recovery of O. lurida where natural recruitment still occurs.
Scholars often discuss marine commodities within the framework of man-made declension; indeed there are several examples in
this volume. This article expands the scope of marine environmental history into a new area, the Persian/Arabian Gulf, and
into a commodity that is often ignored, pearls. The pearl industry in the southern Persian/Arabian Gulf provides an example
of exploitation that declined for reasons other than overfishing, habitat destruction, or industrial exploitation. Specific
decisions undertaken during the last pearl boom, 1870–1930, ensured the sustained existence of this resource.
This paper describes the use and appraises the performance of acoustic ground discrimination systems (AGDS) for marine benthic biotope mapping for those who are more familiar with satellite or airborne remote sensing. The operation of AGDS is described and the nature of the data produced compared with more conventional remotely sensed data. Analysis of the AGDS data involves the interpolation of track point data to create areal coverages that can then be interpreted using classification and image processing techniques. AGDS data have been shown to be variable both within and between surveys and systems which affects the performance of interpretation. Additionally, the marine environment imposes limitations on the way that ground sampling can be undertaken and the spatial extent of information that can be obtained. In summary, the main issues that contribute to variability and uncertainty of biotope maps based on AGDS-based methodology are: (1) errors in position fixing of both AGDS and the ground samples; (2) inconsistent performance of the AGDS system; (3) single frequency of AGDS and its effect on discrimination; (4) tracking intensity of AGDS survey; (5) heterogeneity of the seabed at the scale of resolution of the system; (6) lack of vista for designating training sites and the reliance on buffers around ground samples; (7) unsuitable biotope categories. Variability due to AGDS hardware is often beyond the control of surveyors, but quality control procedures can at least alert operators to poor quality data. Performance of AGDS surveys also depends on intensity of both tracking and ground sampling in relation to heterogeneity of the sea floor. This relationship can be investigated through exploratory spatial data analysis, particularly the variogram. The performance of biotope maps can be measured using error and similarity matrices. The accuracy of the biotope maps resulting from AGDS surveys is modest when compared with the performance of satellite or airborne remote sensing and the similarity between maps derived from different datasets can be low. It is misleading to base expectations of the performance of AGDS on satellite or airborne remote sensing systems. AGDS are low resolution systems with limited powers for discrimination between different ground types. However, they afford the opportunity to map benthic biotopes in environments where electromagnetic spectra-based systems cannot operate. Thus, AGDS is a useful tool for benthic ecologists to study the spatial distribution of biotopes on the sea floor although the limitations of AGDS for mapping may preclude their use for precise and accurate survey required for some monitoring applications.
The Gulf's marine environment is becoming increasingly important in fulfilling social, economic, development and strategic objectives of the region. Human activities and their effects on the Gulf environment are analysed, together with coastal management activities, to understand the context of impacts from the 1991 Gulf War. Oil, domestic, urban and industrial pollutants are a problem in several parts of the Gulf, although effects on ecosystem structure and function are generally not well known. The coastal zone is also fast becoming the repository for solid wastes. Major ecological problems have arisen from loss/degradation of production coastal habitats, caused by coastal landfill, dredging and sedimentation. In some Gulf States (e.g. Saudi Arabia) more than 40% of the coastline has now been developed. Anchor damage to coral reefs is now a problem on Jurayd island and possibly elsewhere. In addition to fishing, hunting of bird eggs is intensive in some areas. Agriculture appears not to be causing major coastal environmental problems, but further studies are needed. Possible longer-term coastal impacts in the Gulf include effects of global climate change, acid deposition and large-scale marine ecosystem instability. The key elements of integrated coastal management are described, with special reference to Saudi Arabia. Regional conservation activities include the UNEP's Kuwait Action Plan. Upholding existing agreements is particularly important in the Gulf, whose transboundary resources constitute a valuable 'commons' shared by eight countries and utilized by many more.
Fisheries can have profound effects on epifaunal community function and structure. We analyzed the results from five dive surveys (1975–1976, 1980, 1983, 2003 and 2007), taken in a Special Area of Conservation, Strangford Lough, Northern Ireland before and after a ten year period of increased trawling activity between 1985 and 1995. There were no detectable differences in the species richness or taxonomic distinctiveness before (1975–1983) and after (2003–2007) this period. However, there was a shift in the epifaunal assemblage between the surveys in 1975–1983 and 2003–2007. In general, the slow-moving, or sessile, erect, filter-feeders were replaced by highly mobile, swimming, scavengers and predators. There were declines in the frequency of the fished bivalve Aequipecten opercularis and the non-fished bivalves Modiolus modiolus and Chlamys varia and some erect sessile invertebrates between the surveys in 1975–1983 and 2003–2007. In contrast, there were increases in the frequency of the fished and reseeded bivalves Pecten maximus and Ostrea edulis, the fished crabs Cancer pagurus and Necora puber and the non-fished sea stars Asterias rubens, Crossaster papposus and Henricia oculata between the surveys in 1975–1983 and 2003–2007. We suggest that these shifts could be directly and indirectly attributed to the long-term impacts of trawl fishing gear, although increases in the supply of discarded bait and influxes of sediment may also have contributed to changes in the frequency of some taxa. These results suggest that despite their limitations, historical surveys and repeat sampling over long periods can help to elucidate the inferred patterns in the epifaunal community. The use of commercial fishing gear was banned from two areas in Strangford Lough in 2011, making it a model ecosystem for assessing the long-term recovery of the epifaunal community from the impacts of mobile and pot fishing gear.
Biofouling is a complex, dynamic problem that globally impacts both the economy and environment. Interdisciplinary research in marine biology, polymer science, and engineering has led to the implementation of bio-inspired strategies for the development of the next generation of antifouling marine coatings. Natural fouling defense mechanisms have been mimicked through chemical, physical, and/or stimuli-responsive strategies. This review outlines the detrimental effects associated with biofouling, describes the theoretical basis for antifouling coating design, and highlights prominent advances in bio-inspired antifouling technologies.
The benthic environment of the Gulf of Maine is characterized by a thick and basin‐wide nepheloid layer, classically defined as a near‐bottom region of permanent sediment resuspension. The high frequency of commercial bottom trawling in particular regions of the Gulf of Maine, documented by records compiled by the National Marine Fisheries Service, may strongly affect measured resuspension fluxes and contribute to the maintenance of the nepheloid layer. Indirect evidence of the effects of bottom trawling on sediment resuspension is observed in the seasonal collection of large, benthic infaunal worms, along with substantial amounts of resuspended bottom sediment, in a sediment trap deployed 25 m off the bottom in the western gulf region of Wilkinson Basin. These collections appear to be coincident with seasonal periods of intensive bottom trawling in this area. By comparison, the western gulf region of Jordan Basin is typified by significantly reduced annual bottom‐trawling activity, and very few infaunal worms are found in the seasonal collections of a sediment trap located 25–30 m off the bottom. The extent to which trawling‐induced bottom sediment excavation and resuspension occurs has important implications for regional nutrient budgets in terms of the input of sedimentary nitrogen and silica into the water column via this anthropogenic activity. Sediment mixing and frequent bottom disturbance from trawling activity may also produce changes in the successional organization of soft‐sediment infaunal communities. The potential effects of trawling require serious examination and quantification to accurately determine the impact of such anthropogenic activity on the benthic ecosystems of continental margin environments.
Resuspensión de Sedimentos por Arrastres de Fondo en el Golfo de Maine y sus Consecuencias Geoquímicas Potenciales
El ambiente bentónico del Golfo de Maine esta caracterizado por una capa gruesa y amplia de nefeloide, clásicamente definida como una región de resuspensión permanente de sedimentos cercana al fondo. La alta frecuencia de arrastres comerciales de fondo en regiones particulares del Golfo de Maine documentadas por datos compliados por el Servicio Nacional de Pesquerias Marinas, puede afectar drástricamente los flujos de resuspensión de sedimentos que contribuyen con el mantenimiento de la capa nefeloide. Evidencias indirectas de los efectos de arrastres de fondo en la suspensión de sedimentos se observan en la colecta de gusanos bénticos infaunales grandes, a lo largo de una cantidad sustancial de sedimento del fondo resuspendido en una trampa de sedimentos colocada a 25 m del fondo en la región oeste del golfo de la Cuenca Wilkinson. Estas colectas aparentemente coinciden con la temporada de intensa actividad de arrastres en la zona. Como comparación, la región Este de la Cuenca Jordan es tipificada por una reducción anual significativa de arrastres de fondo con muy pocos gusanos infaunales encontrados en las colectas estacionales de una trampa colocada a 25‐30 m del fondo. La extensión de la excavación inducida por arrastres en el sedimento del fondo y la resuspensión tiene implicaciones importantes en la disponibilidad de nutrientes de la región en términos de la entrada de nitrógeno sedimentario y sílica a la columna de agua vía esta actividad antropogénica. Adicionalmente, la mezcla de sedimentos y la frecuente perturbación del fondo por arrastres puede producir cambios en la organización sucesional de las comunidades infaunales de sedimentos suaves. Los efectos potenciales del arrastre requieren de una examinación seria y su cuantificación para determinar con precisión el impacto de estas actividades antropogénicas en ecosistemas bénticos de ambientes continentales marginales.
Long-term observations and study of coral reef destruction by hurricanes in the Florida Keys show, surprisingly, that although
corals are devastated on a grand scale during storms, recovery is rapid. Recovery occurs because of the widespread scattering
of live fragments, many of which become growth sites of new colonies. Reef recovery from death by chilling in the Persian
Gulf was well under way when last observed, but it is not yet known if the recovery rate was as rapid as recovery from the
storm destruction in Florida. Recovery from death by chilling requires settlement of transported coral larvae and a substrate
suitable for larval attachment. Such resettlement is subject to the effects of currents, predators, pollution, and competition
for substrate.
A growth rate of 10 cm per year combined with geometrical progression of branch formation accounts for rapidAcropora cervicornis recovery. Although calculated coral proliferation seems unusually high, it has been confirmed by serial underwater photographs
spanning ten years. More precise measurements of growth and branching are needed, along with growth data for other common
reef-building corals. Such data would be useful for predicting standing crop of a restocked or transplanted reef.
This study aimed to investigate intra- and inter-site differences in the epibiota on the European oyster Ostrea edulis of different ages and on hard substrata to assess their contribution to biodiversity. This research has shown that shells
of O. edulis do show higher species diversity than non-living hard substrata and as oysters grow larger epibiotic diversity will increase.
This investigation has revealed that O. edulis possesses biogenic engineering qualities and the value of O. edulis as a vehicle for increasing biodiversity should not be underestimated. Relatively few studies have examined the shell surfaces
of Ostrea edulis, which, together with their associated epifauna provide a large portion of the natural hard substrata for sessile filter-feeding
organisms, including oysters, in coastal and estuarine ecosystems. It can be considered a keystone species which has an influence
on intertidal and subtidal community structures.
Keywords
Ostrea edulis
-Biodiversity-Epibiota-Succession
Nineteen of the 57 littoral rocky shore biotopes and 4 of the 26 variants as well as 1 sublittoral fringe biotope classified for Britain and Ireland have been recorded on Helgoland in this baseline study. Most of the wave-cut platform is at sublittoral and lower littoral levels and most high eulittoral biotopes are confined to narrow zones on seawalls. Large areas of gently sloping lower eulittoral and also boulder areas adjacent to seawalls are characterised by a mixture of two or more biotopes. Only 4 of the 23 littoral biotopes and variants are characterised by faunal species. Comparison with past descriptions of intertidal communities suggests continuing presence of most of the autochthonous biotopes over the past 80years but also change due to the invasion of the macroalgae Mastocarpus stellatus and Sargassum muticum over the past 20years. One previously recorded cave biotope and a sublittoral seagrass site have become extinct due to habitat loss while other biotopes probably have extended their range due to habitat increase. The presence of 4 intertidal biotopes (20%) considered rare or scarce in Britain supports the recognition of Helgoland as a site of special conservation in a regional and international context.
Photographic and video methods are frequently used to increase the efficiency of coral reef monitoring efforts. The random point count method is commonly used on still images or frame-grabbed video to estimate the community statistics of benthos. A matrix of randomly distributed points is overlaid on an image, and the species or substrate-type lying beneath each point is visually identified. Coral Point Count with Excel extensions (CPCe) is a standalone Visual Basic program which automates, facilitates, and speeds the random point count analysis process. CPCe includes automatic frame-image sequencing, single-click species/substrate labeling, auto-advancement of data point focus, zoom in/out, zoom hold, and specification of random point number, distribution type, and frame border location. Customization options include user-specified coral/substrate codes and data point shape, size, and color. CPCe can also perform image calibration and planar area and length calculation of benthic features. The ability to automatically generate analysis spreadsheets in Microsoft Excel based upon the supplied species/substrate codes is a significant feature. Data from individual frames can be combined to produce both inter- and intra-site comparisons. Spreadsheet contents include header information, statistical parameters of each species/substrate type (relative abundance, mean, standard deviation, standard error) and the calculation of the Shannon–Weaver diversity index for each species. Additional information can be found at http://www.nova.edu/ocean/cpce/.
Implementing ecosystem-based management requires methods of assessing the quality of habitats to deliver the high-level objective of achieving healthy ecosystems. 'Habitat' has been interpreted in different ways and this has confused the debate over which attributes constitute 'quality'. Three definitions of quality for habitats are advanced: 'species', 'reference' and 'functional' . Operational measures associated with these are evaluated in terms of their utility to deliver policy objectives. It is concluded that functional definitions/measures of quality are most appropriate to deliver ecosystem-based management although measures of species and reference quality may support assessment of the functional quality of habitats.
Throughout much of the UK and in Europe generally the native oyster is in a severely depleted state in the wild. In order to address and potentially to reverse this situation Ostrea edulis was designated as a named species in the UK Biodiversity Action Plan as part of a national commitment to the International Convention on Biodiversity. Amongst other initiatives, some of which are summarised in this paper, a feasibility study was carried out to evaluate all the factors, including an economic assessment, relevant to a programme of stock restoration in the UK. The study showed that there is a considerable body of data on the biology, ecology and distribution of O. edulis to inform restoration projects. Appropriate legislation is in place to allow for restoration. Non-marketable costs and benefits were estimated. They provide an idea of the high value that may be placed on biodiversity aspects. Nevertheless, this study also shows that stock restoration can be commercially viable if fishery prices and yields are sufficiently high. Restoration efforts and associated studies elsewhere have shown the potential for success of native oyster stock regeneration, especially in disease-free areas. For these, there is a very strong element of re-creating and conserving an ecological resource. The relaying of cultch is seen as an essential component of a successful oyster restoration programme and the use of sanctuaries is generally considered beneficial. The loss of the standing stock is a limiting factor and re-stocking is an effective strategy. There is a basic genetic similarity of wild European O. edulis populations such that the source of stocks is not critical. There are some problems with hatchery rearing from these, but using breeding ponds or importing part-grown oysters are viable alternatives.
The paper presents an analysis and synthesis of historical and archaeological data on pearl fishing in the Persian Gulf. The history of pearling in the region is reviewed, from the earliest possible references to the mid 20th century. Economic data from the 18th�20th centuries CE is analysed in detail, to de fine the economic course of the pearling industry during that time, and assess the impact on human settlement in the region. The archaeological data for pearl fishing are then examined, from the 6th millennium BCE onwards, and compared to the historical evidence. The results of archaeological survey in the Abu Dhabi islands region are then taken as a case study, and changes in settlement patterns are related to the historical trajectory of the pearling industry. It is observed that the regional economy became overwhelmingly dependent on the pearl trade in recent centuries, and was increasingly subject to the demands of the global market.
In Strangford Lough, Northern Ireland stocks of Ostrea edulis collapsed in the 1890s and the species was rarely recorded again until 1998 when the wild stock was estimated to be 100,000. The stock increased to 1.2 million in 2003 but declined to 650,000 by 2005. In 2007 the stock exceeded 1 million. The initial recovery of wild stocks is attributed to the combined effects of spawning commercial O. edulis stocks of and larval retention due to local hydrography. The stock decline between 2003 and 2005 is attributed to unregulated harvesting. Significant differences in abundances between sites over this period may be explained by the exploitation of more-readily accessible sites initially and of less accessible sites later. Oysters at sites where there was minimal exploitation probably contributed to widespread recruitment in 2007. Sustainable management of recovering native oyster stocks in Strangford Lough and elsewhere and will be impossible without appropriate legislation and enforcement.