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Jean-pierre Debenay - One of the best experts on this subject based on the ideXlab platform.
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Modern diatom distribution in Mangrove Swamps from the Kaw Estuary (French Guiana)
Marine Geology, 2004Co-Authors: Florence Sylvestre, Daniel Guiral, Jean-pierre DebenayAbstract:Modern diatom assemblages were analyzed in 85 surface sediment samples collected in the Kaw estuary and adjacent Mangrove Swamps. Samples were collected according to seasonal variations (wet versus dry) and mudbank stability phases, from fluid mudflat to Mangrove Swamps overgrown with vegetation. According to the diatom species habitat and salinity affinities, the modern distribution shows three main diatom assemblages more related to the sediment stability than the seasonal variations. The fluid mudflat was primarily dominated by marine planktonic species (Coscinodiscus centralis, Cyclotella stylorum, Thalassionema nitzschioides) carried by oceanic waters. These species also dominated the samples located in the estuarine channel of the Kaw River and in adjacent Mangrove swamp areas in the upstream portion of the estuary. The occurrence of these marine planktonic species suggests a deep penetration of oceanic water into the estuary. The fluid mudflat was characterized by epipelic species, mostly dominated by species from the genera Gyrosigma, which are characterized by a high motility inside the sediments. This autochthonous epipelic assemblage could be considered as a biological indicator of the fluid mudflat stability. In the Mangrove swamp stabilized by vegetation, the diatom assemblages are more diverse and dominated by species from the genera Nitzschia and Navicula.
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behaviour and taphonomic loss in foraminiferal assemblages of Mangrove Swamps of french guiana
Marine Geology, 2004Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Fifty-three surface sediment samples were collected in January 1999, July 2000 and December 2000 on mud flats and in Mangrove Swamps of French Guiana. Sampling stations were selected to provide information on different environmental conditions, on the mud flats and in the Mangrove forest. Thirteen samples were also collected at a depth of about 8–12 cm in the sediment. Additional samples were collected from three long cores in the channel of the Kaw River. The main parameter controlling the distribution of recent foraminiferal assemblages is the seasonally variable relative influence of coastal water of reduced salinity and low pH, low-Ca river water. Areas under the influence of coastal water are dominated by calcareous species, mainly Ammonia tepida and Cribroelphidium spp., even in Mangrove Swamps during the dry season. River water influences almost all the study area during the rainy season and leads to the dominance of agglutinated species, with the nature of the assemblages depending on local environmental characteristics. On the mud flats, tests are typically well preserved in the 10 cm below the surface that is the most important taphonomically active zone for foraminifera. However, owing to intense bioturbation, the taphonomic processes in the Mangrove swamp may result in the total destruction of the microfauna, including agglutinated tests. This study shows that the preservation of thanatocoenoses in Mangrove swamp environments of French Guiana only occurs in exceptional circumstances. When they are preserved, the remaining assemblages, even if modified by taphonomic processes, give valuable information for paleoenvironmental reconstructions in this environment.
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ecological factors acting on the microfauna in Mangrove Swamps the case of foraminiferal assemblages in french guiana
Estuarine Coastal and Shelf Science, 2002Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Thirty-seven surface sediment samples were collected in January 1999 and July 2000 in the Mangrove Swamps and mud flats of French Guiana where strong seasonal contrasts occur. Sampling stations were selected to provide information on the foraminiferal assemblages associated with different environmental conditions, on the mud banks and in the Mangrove forest. A total of 44 species have been identified. The main parameter acting on the distribution of foraminiferal assemblages is the hydrodynamics of the estuary, characterized by the double influence of coastal water and low-Ca fresh water, with drastic seasonal changes. The coastal end member is dominated by the calcareous species Ammonia tepida, A. parkinsoniana andCribroelphidium spp., the continental (freshwater) end member is characterized by Miliammina fusca andTrochamminita irregularis . The calcareous species penetrate into the estuary, even into the Mangrove forest during the dry season, but totally disappear from the estuary during the rainy season. The second parameter acting on the distribution of foraminiferal assemblages is the vertical elevation that acts indirectly by influencing the time of aerial exposure and the colonization by Mangrove trees. Both canopy and litter of the Mangrove forest protect the sediment from heating, drying and increases in salinity due to sun and wind. Foraminifera are very rare or absent on the open mud banks affected by mud cracks, but begin to grow as soon as young Avicennia are present. In the Mangrove Swamps, local conditions influence the composition of the assemblages and the taphonomic processes.
Mario Parra - One of the best experts on this subject based on the ideXlab platform.
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behaviour and taphonomic loss in foraminiferal assemblages of Mangrove Swamps of french guiana
Marine Geology, 2004Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Fifty-three surface sediment samples were collected in January 1999, July 2000 and December 2000 on mud flats and in Mangrove Swamps of French Guiana. Sampling stations were selected to provide information on different environmental conditions, on the mud flats and in the Mangrove forest. Thirteen samples were also collected at a depth of about 8–12 cm in the sediment. Additional samples were collected from three long cores in the channel of the Kaw River. The main parameter controlling the distribution of recent foraminiferal assemblages is the seasonally variable relative influence of coastal water of reduced salinity and low pH, low-Ca river water. Areas under the influence of coastal water are dominated by calcareous species, mainly Ammonia tepida and Cribroelphidium spp., even in Mangrove Swamps during the dry season. River water influences almost all the study area during the rainy season and leads to the dominance of agglutinated species, with the nature of the assemblages depending on local environmental characteristics. On the mud flats, tests are typically well preserved in the 10 cm below the surface that is the most important taphonomically active zone for foraminifera. However, owing to intense bioturbation, the taphonomic processes in the Mangrove swamp may result in the total destruction of the microfauna, including agglutinated tests. This study shows that the preservation of thanatocoenoses in Mangrove swamp environments of French Guiana only occurs in exceptional circumstances. When they are preserved, the remaining assemblages, even if modified by taphonomic processes, give valuable information for paleoenvironmental reconstructions in this environment.
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ecological factors acting on the microfauna in Mangrove Swamps the case of foraminiferal assemblages in french guiana
Estuarine Coastal and Shelf Science, 2002Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Thirty-seven surface sediment samples were collected in January 1999 and July 2000 in the Mangrove Swamps and mud flats of French Guiana where strong seasonal contrasts occur. Sampling stations were selected to provide information on the foraminiferal assemblages associated with different environmental conditions, on the mud banks and in the Mangrove forest. A total of 44 species have been identified. The main parameter acting on the distribution of foraminiferal assemblages is the hydrodynamics of the estuary, characterized by the double influence of coastal water and low-Ca fresh water, with drastic seasonal changes. The coastal end member is dominated by the calcareous species Ammonia tepida, A. parkinsoniana andCribroelphidium spp., the continental (freshwater) end member is characterized by Miliammina fusca andTrochamminita irregularis . The calcareous species penetrate into the estuary, even into the Mangrove forest during the dry season, but totally disappear from the estuary during the rainy season. The second parameter acting on the distribution of foraminiferal assemblages is the vertical elevation that acts indirectly by influencing the time of aerial exposure and the colonization by Mangrove trees. Both canopy and litter of the Mangrove forest protect the sediment from heating, drying and increases in salinity due to sun and wind. Foraminifera are very rare or absent on the open mud banks affected by mud cracks, but begin to grow as soon as young Avicennia are present. In the Mangrove Swamps, local conditions influence the composition of the assemblages and the taphonomic processes.
Daniel Guiral - One of the best experts on this subject based on the ideXlab platform.
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Modern diatom distribution in Mangrove Swamps from the Kaw Estuary (French Guiana)
Marine Geology, 2004Co-Authors: Florence Sylvestre, Daniel Guiral, Jean-pierre DebenayAbstract:Modern diatom assemblages were analyzed in 85 surface sediment samples collected in the Kaw estuary and adjacent Mangrove Swamps. Samples were collected according to seasonal variations (wet versus dry) and mudbank stability phases, from fluid mudflat to Mangrove Swamps overgrown with vegetation. According to the diatom species habitat and salinity affinities, the modern distribution shows three main diatom assemblages more related to the sediment stability than the seasonal variations. The fluid mudflat was primarily dominated by marine planktonic species (Coscinodiscus centralis, Cyclotella stylorum, Thalassionema nitzschioides) carried by oceanic waters. These species also dominated the samples located in the estuarine channel of the Kaw River and in adjacent Mangrove swamp areas in the upstream portion of the estuary. The occurrence of these marine planktonic species suggests a deep penetration of oceanic water into the estuary. The fluid mudflat was characterized by epipelic species, mostly dominated by species from the genera Gyrosigma, which are characterized by a high motility inside the sediments. This autochthonous epipelic assemblage could be considered as a biological indicator of the fluid mudflat stability. In the Mangrove swamp stabilized by vegetation, the diatom assemblages are more diverse and dominated by species from the genera Nitzschia and Navicula.
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behaviour and taphonomic loss in foraminiferal assemblages of Mangrove Swamps of french guiana
Marine Geology, 2004Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Fifty-three surface sediment samples were collected in January 1999, July 2000 and December 2000 on mud flats and in Mangrove Swamps of French Guiana. Sampling stations were selected to provide information on different environmental conditions, on the mud flats and in the Mangrove forest. Thirteen samples were also collected at a depth of about 8–12 cm in the sediment. Additional samples were collected from three long cores in the channel of the Kaw River. The main parameter controlling the distribution of recent foraminiferal assemblages is the seasonally variable relative influence of coastal water of reduced salinity and low pH, low-Ca river water. Areas under the influence of coastal water are dominated by calcareous species, mainly Ammonia tepida and Cribroelphidium spp., even in Mangrove Swamps during the dry season. River water influences almost all the study area during the rainy season and leads to the dominance of agglutinated species, with the nature of the assemblages depending on local environmental characteristics. On the mud flats, tests are typically well preserved in the 10 cm below the surface that is the most important taphonomically active zone for foraminifera. However, owing to intense bioturbation, the taphonomic processes in the Mangrove swamp may result in the total destruction of the microfauna, including agglutinated tests. This study shows that the preservation of thanatocoenoses in Mangrove swamp environments of French Guiana only occurs in exceptional circumstances. When they are preserved, the remaining assemblages, even if modified by taphonomic processes, give valuable information for paleoenvironmental reconstructions in this environment.
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ecological factors acting on the microfauna in Mangrove Swamps the case of foraminiferal assemblages in french guiana
Estuarine Coastal and Shelf Science, 2002Co-Authors: Jean-pierre Debenay, Daniel Guiral, Mario ParraAbstract:Abstract Thirty-seven surface sediment samples were collected in January 1999 and July 2000 in the Mangrove Swamps and mud flats of French Guiana where strong seasonal contrasts occur. Sampling stations were selected to provide information on the foraminiferal assemblages associated with different environmental conditions, on the mud banks and in the Mangrove forest. A total of 44 species have been identified. The main parameter acting on the distribution of foraminiferal assemblages is the hydrodynamics of the estuary, characterized by the double influence of coastal water and low-Ca fresh water, with drastic seasonal changes. The coastal end member is dominated by the calcareous species Ammonia tepida, A. parkinsoniana andCribroelphidium spp., the continental (freshwater) end member is characterized by Miliammina fusca andTrochamminita irregularis . The calcareous species penetrate into the estuary, even into the Mangrove forest during the dry season, but totally disappear from the estuary during the rainy season. The second parameter acting on the distribution of foraminiferal assemblages is the vertical elevation that acts indirectly by influencing the time of aerial exposure and the colonization by Mangrove trees. Both canopy and litter of the Mangrove forest protect the sediment from heating, drying and increases in salinity due to sun and wind. Foraminifera are very rare or absent on the open mud banks affected by mud cracks, but begin to grow as soon as young Avicennia are present. In the Mangrove Swamps, local conditions influence the composition of the assemblages and the taphonomic processes.
James C Lynch - One of the best experts on this subject based on the ideXlab platform.
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global carbon sequestration in tidal saline wetland soils
Global Biogeochemical Cycles, 2003Co-Authors: Gail L Chmura, Shimon C Anisfeld, Donald R Cahoon, James C LynchAbstract:[1] Wetlands represent the largest component of the terrestrial biological carbon pool and thus play an important role in global carbon cycles. Most global carbon budgets, however, have focused on dry land ecosystems that extend over large areas and have not accounted for the many small, scattered carbon-storing ecosystems such as tidal saline wetlands. We compiled data for 154 sites in Mangroves and salt marshes from the western and eastern Atlantic and Pacific coasts, as well as the Indian Ocean, Mediterranean Ocean, and Gulf of Mexico. The set of sites spans a latitudinal range from 22.4°S in the Indian Ocean to 55.5°N in the northeastern Atlantic. The average soil carbon density of Mangrove Swamps (0.055 ± 0.004 g cm−3) is significantly higher than the salt marsh average (0.039 ± 0.003 g cm−3). Soil carbon density in Mangrove Swamps and Spartina patens marshes declines with increasing average annual temperature, probably due to increased decay rates at higher temperatures. In contrast, carbon sequestration rates were not significantly different between Mangrove Swamps and salt marshes. Variability in sediment accumulation rates within marshes is a major control of carbon sequestration rates masking any relationship with climatic parameters. Globally, these combined wetlands store at least 44.6 Tg C yr−1 and probably more, as detailed areal inventories are not available for salt marshes in China and South America. Much attention has been given to the role of freshwater wetlands, particularly northern peatlands, as carbon sinks. In contrast to peatlands, salt marshes and Mangroves release negligible amounts of greenhouse gases and store more carbon per unit area.
Yuk Shan Wong - One of the best experts on this subject based on the ideXlab platform.
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contamination of polycyclic aromatic hydrocarbons in surface sediments of Mangrove Swamps
Environmental Pollution, 2001Co-Authors: L Ke, Xin Wang, Yuk Shan WongAbstract:Abstract The concentrations of total polycyclic aromatic hydrocarbons (ΣPAHs) and 15 individual PAH compounds in 20 surface sediments collected from four Mangrove Swamps in Hong Kong were analysed. ΣPAH concentrations ranged from 356 to 11,098 ng g −1 dry weight with mean and median values of 1992 and 1142 ng g −1 , respectively. These values were significantly higher than those of marine bottom sediments of Hong Kong harbours, suggesting that more PAHs were accumulated in Mangrove surface sediments. The concentrations of ΣPAHs as well as individual PAH compound varied significantly among Mangrove Swamps. The Swamps heavily polluted by livestock and industrial sewage, such as Ho Chung and Mai Po, had much higher concentrations of total PAHs and individual PAH than the other Swamps. The PAH profiles were similar among four Mangrove Swamps, and were dominated by naphthalene (two-ring PAH), fluorene and phenanthrene (three-ring PAH). The Mangrove sediments had higher percentages of low-molecular-weight PAHs. These indicated that PAHs in Mangrove sediments might originate from oil or sewage contamination (petrogenic input). Ratio values of specific PAH compounds such as phenanthrene/anthracene and fluoranthene/pyrene, were calculated to evaluate the possible source of PAH contamination in Mangrove sediments. These ratios varied among samples, suggesting that Mangrove sediments might have a mixed pattern of pyrolytic and petrogenic inputs of PAHs. Sediments collected from Ho Chung Mangrove swamp appeared to be more dominated by pyrolytic input while those from Tolo showed strong petrogenic contamination.
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spatial variation of heavy metals in surface sediments of hong kong Mangrove Swamps
Environmental Pollution, 2000Co-Authors: Yuk Shan WongAbstract:The degree of heavy metal contamination in the fine-grained (<63 μm) and sand-sized (2 mm–63 μm) fractions of surface sediments in 18 different Mangrove Swamps (144 random samples) in Hong Kong was examined. Higher concentrations of heavy metals were found in the fine-grained than the sand-sized fractions of the sediment; however, the differences between these two fractions became less significant when the swamp was more contaminated. The principal component analyses show that the 18 Mangrove Swamps, according to the median concentrations of total heavy metals, were clustered into four groups. The first group included three Mangrove Swamps in Deep Bay region which are seriously contaminated, with heavy metal concentrations in sediments around 80 μg g−1 Cu, 240 μg g−1 Zn, 40 μg g−1 Cr, 30 μg g−1 Ni, 3 μg g−1 Cd and 80 μg g−1 Pb. The second cluster, made up of another four Swamps distributed in different geographical locations (two in Sai Kung district and two in Tolo region), also had elevated levels of Cu, Pb, Ni and Cr in the sediments. Field observation reveals that these seven stands received industrial, livestock and domestic sewage as well as pollution from mariculture activities, suggesting that anthropogenic input is the main source of heavy metal contamination in Hong Kong Mangroves. The sediments from other Mangrove Swamps were relatively uncontaminated.