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Marine Molluscs (marine + mollusc)

Distribution by Scientific Domains
Earth and Environmental Science57%

Selected Abstracts

Effects of natural barriers on the spillover of a marine mollusc: implications for fisheries reserves

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2003
Alexander Tewfik
Abstract 1.The movement of organisms and dispersal of propagules is fundamental to the maintenance of populations over time. However, the existence of barriers, created through the spatial configuration of habitats, may significantly affect dispersal patterns and thus influence community dynamics and resource sustainability. 2.Within marine environments unstructured or open habitats may form partial or complete ecological barriers due to elevated risk of predation or physical stresses associated with them. The existence and effects of such barriers may be of particular importance when considering the establishment of marine protected areas with a fisheries enhancement focus. 3.In this paper, the spillover of post-settlement queen conch (Strombus gigas) from a protected area in the Turks and Caicos Islands is investigated. It is hypothesized that the reserve boundaries overlap with a series of shallow, sand habitats that effectively enclose the protected population, reducing the spillover of conch into the adjacent fished areas. 4.To test this, density gradient maps for juvenile and adult conch populations were constructed using underwater visual survey data at 68 sites within and surrounding the protected area. These maps illustrate very low densities coinciding with poor, shallow sand habitats along the two marine boundaries of the reserve where spillover is expected to take place. 5.These sand habitats are thought to create ecological barriers to a slow, sedentary gastropod largely due to their shallowness (physical stresses of solar exposure or anoxia) and lack of food reducing the tendency of individuals to move across these areas, despite the 10-times higher density of adult queen conch observed in the protected area compared with outside. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Molecular identification and expression study of differentially regulated genes in the Pacific oyster Crassostrea gigas in response to pesticide exposure

FEBS JOURNAL, Issue 2 2005
Arnaud Tanguy
The effects of pesticide contamination on the metabolism of marine molluscs are poorly documented. We investigated the response of a marine bivalve, the Pacific oyster, Crassostrea gigas, using a suppression subtractive hybridization method to identify up- and down-regulated genes after a 30-day exposure period to herbicides (a cocktail of atrazine, diuron and isoproturon, and to the single herbicide glyphosate). A total of 137 unique differentially expressed gene sequences was identified, as well as their associated physiological process. The expression of 18 of these genes was analyzed by RT-PCR under laboratory experimental conditions. The metabolic functions they are associated with include xenobiotic detoxification, energy production, immune system response and transcription. This study provides a preliminary basis for studying the response of marine bivalves to long-term herbicide exposure in terms of regulated gene expression and characterizes new potential genetic markers of herbicide contamination. [source]

STEPHEN HISLOP AND HIS 1860 CRETACEOUS CONTINENTAL MOLLUSCAN NEW SPECIES DESCRIPTIONS IN LATIN FROM THE DECCAN PLATEAU, INDIA

PALAEONTOLOGY, Issue 6 2008
JOSEPH H. HARTMAN
Abstract:, In 1860, Stephen Hislop published a data-rich document on the infra- and intertrappean strata of the Deccan Plateau of central India, along with numerous new taxa of continental and marine molluscs. His scholarship interestingly blended antiquated, contemporary, and ahead-of-his-time palaeontological methods. Although his work established a completely adequate foundation upon which to build future end-Cretaceous Deccan molluscan studies, effectively no substantive work ensued, with only incidental subsequent reference to his effort. [source]

Discoveries of Neolithic prehistoric sites at Pleistocene carbonate rock shelters on the east coast of the UAE

ARABIAN ARCHAEOLOGY AND EPIGRAPHY, Issue 2 2006
Cajus G. Diedrich Dr.Article first published online: 8 DEC 200
Three newly discovered prehistoric sites on the east coast of the United Emirates (UAE) are described. All are located on surfaces of Pleistocene carbonates or rock shelters that are generally rare along the eastern coast of the Gulf of Oman. Aqqah 1 (Le Meridien al Aqqah Beach Resort), the most important and best preserved of these sites, is a partially collapsed rock shelter with an exposed section, lithic finds and marine molluscs. Deriving an exact date from the material present is difficult because of a lack of comparanda. A bifacial fletched arrowhead made of yellow jasper and the lithic debris of five different raw materials as well as an undecorated ceramic fragment might suggest a date in the Late Neolithic or Early Bronze Age. The presence of many marine bivalves and snails with operculae, which differ from recent coastal species, indicates the collection and consumption of living molluscs by the prehistoric population of Aqqah. Nearby burials may be related to the rock shelters. [source]

Late- and postglacial history of the Great Belt, Denmark

BOREAS, Issue 1 2004
OLE BENNIKE
On the basis of shallow seismic records, vibrocoring, macrofossil analyses and AMS radiocarbon-dating, five stratigraphical units have been distinguished from the deepest parts of the central Great Belt (Storebælt) in southern Scandinavia. Widespread glacial deposits are followed by two lateglacial units confined to deeply incised channels and separated by an erosional boundary. Lateglacial Unit I dates from the time interval from the last deglaciation to the Allerød; lateglacial Unit II is of Younger Dryas age. Early Holocene deposits show a development from river deposits and lake-shore deposits to large lake deposits, corresponding to a rising shore level. Lake deposits are found up to 20 m below the sea floor, and the lake extended over some 200,300 km2. The early Holocene freshwater deposits are dated to the time interval c. 10900 to c. 8800 cal. yr BP and the oldest shells of marine molluscs from the Great Belt are dated to c. 8100 cal. yr BP. [source]

Late Quaternary history around Nioghalvfjerdsfjorden and Jøkelbugten, North-East Greenland

BOREAS, Issue 3 2001
OLE BENNIKE
Nioghalvfjerdsfjorden in North-East Greenland is at present covered by a floating glacier. Raised marine deposits in the surrounding area contain shells of marine molluscs, bones of marine mammals and pieces of driftwood. A fairly systematic sampling of such material has been conducted, followed by extensive radiocarbon dating. We suggest that the Greenland ice sheet extended onto the shelf offshore North-East Greenland during isotope stage 2, perhaps even reaching the shelf break. During the subsequent recession of the ice sheet, the entrance of Nioghalvfjerdsfjorden had become ice-free by 9.7 cal. ka BP. The recession culminated between 7.7 and 4.5 cal. ka BP, during which time the fjord was glacier-free along its entire 80 km length. No dates younger than 4.5 cal. ka BP are available on marine material from the fjord, and it seems probable that the fjord has been continuously covered by the floating glacier since this time. The maximum glaciation was attained around AD 1900, after which thinning and recession took place. The marine limit increases from c. 40 m above sea level near the present margin of the Inland Ice to c. 65 m above sea level at the outer coast. These figures fit into the regional pattern of the marine limit for areas both to the south and north. The marine fauna comprise two bivalves, Macoma calcarea and Serripes groenlandicus, that may represent a southern element present during the Holocene temperature optimum. Remains of three taxa of southern extralimital terrestrial and limnic plants were dated to 5.1 cal. ka BP, and remains of another extralimital plant were dated to 8.8 and 8.5 cal. ka BP. The known Holocene time ranges of the willow Salix arctica and the lemming Dicrostonyx torquatus have been extended back to 8.8 and 6.4 cal. ka BP, respectively, providing minimum dates for their immigration to Greenland. [source]

Early Holocene drowned lagoonal deposits from the Kattegat, southern Scandinavia

BOREAS, Issue 4 2000
OLE BENNIKE
Shallow seismic profiling indicated the presence of a drowned lagoon,barrier system formed during the transgression of the southern Kattegat, and investigations of core material have confirmed this. Studies of plant and animal macrofossils show that the lagoonal sediments contain a mixture of marine, brackish, lacustrine, telmatic and terrestrial taxa, and analyses of foraminifers indicate brackish-water conditions. Low oxygen isotope values obtained on shells of marine molluscs also point to lowered salinity. The lagoonal sediments are situated at depths between 24 and 35 m below present sea level. They are dated to between c. 10.5 cal. ka BP and c. 9.5 cal. ka BP, and reflect a period characterized by a moderate relative sea level rise. The lagoonal sediments are underlain by lateglacial glaciomarine clay and silt, which are separated from the Holocene deposits by an unconformity. The earliest Holocene sediments consist of littoral sand with gravel, stones and shells; these sediments were formed during the transgression of the area before the barrier island,lagoon system was developed. The lagoonal sediments are overlain by mud, which contains animal remains that indicate increasing water depths. [source]