Seasonal Influence of the Needle Rush <Emphasis Type="Italic">Juncus roemarianus</Emphasis> on Saltmarsh Pore Water Geochemistry     

Carla M. Koretsky  Douglas Miller 《Estuaries and Coasts》2008,31(1):70-84

Previous studies have shown that saltmarsh macrophytes have a significant influence on sediment biogeochemistry, both through radial release of oxygen from roots and also via primary production and release of labile organic exudates from roots. To assess the seasonal influence of the needle rush, Juncus roemarianus, on saltmarsh sediment geochemistry, pore waters and sediments were collected from the upper 50 cm of two adjacent sites, one unvegetated and the other vegetated by Juncus roemarianus, in a Georgia saltmarsh during winter and summer. Pore waters collected at 1- to 2-cm intervals were analyzed for pH, alkalinity, dissolved phosphate, ammonium, Fe(II), Fe(III), Mn(II), sulfide, sulfate, and organic carbon. Sediments were collected at 5-cm intervals and analyzed for iron distribution in the solid phase using a two-step sequential extraction. The upper 50 cm of the sediment pore waters are mostly sulfidic during both winter and summer. The pore water and sediment geochemistry suggest organic matter degradation is coupled mostly to Fe(III) and sulfate reduction. In summer, there is greater accumulation of alkalinity, sulfide, ammonium, and phosphate in the pore waters and lower levels of ascorbate extractable Fe, which is presumed to be comprised primarily of readily reducible Fe(III) oxides, in the sediments, consistent with higher organic matter degradation rates in summer compared to winter. Lower pH, alkalinity, ammonium, and sulfide concentrations in sediments with Juncus, compared to nearby unvegetated sediments, is consistent with release of oxygen into the Juncus rhizosphere, especially during summer.  相似文献   

Geodynamic evolution of the Taiwan-Luzon-Mindoro belt since the late eocene   总被引：1，自引：0，他引：1  

Jean Franois Stephan  Ren Blanchet  Claude Rangin  Bernard Pelletier  Jean Letouzey  Carla Muller 《Tectonophysics》1986,125(1-3)

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Methods to the measurements of distances     

Mario Carla 《Journal of Geodesy》1962,36(4):317-319

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Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles     

Isabelle Leblond  Carla Scalabrin  Laurent Berger 《Marine Geophysical Researches》2014,35(3):191-210

Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en-route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0–200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.  相似文献   

Acoustic monitoring of gas emissions from the seafloor. Part II: a case study from the Sea of Marmara     

Gaye Bayrakci  Carla Scalabrin  Stéphanie Dupré  Isabelle Leblond  Jean-Baptiste Tary  Nadine Lanteri  Jean-Marie Augustin  Laurent Berger  Estelle Cros  André Ogor  Christos Tsabaris  Marc Lescanne  Louis Géli 《Marine Geophysical Researches》2014,35(3):211-229

A rotating, acoustic gas bubble detector, BOB (Bubble OBservatory) module was deployed during two surveys, conducted in 2009 and 2011 respectively, to study the temporal variations of gas emissions from the Marmara seafloor, along the North Anatolian Fault zone. The echosounder mounted on the instrument insonifies an angular sector of 7° during a given duration (of about 1 h). Then it rotates to the next, near-by angular sector and so forth. When the full angular domain is insonified, the “pan and tilt system” rotates back to its initial position, in order to start a new cycle (of about 1 day). The acoustic data reveal that gas emission is not a steady process, with observed temporal variations ranging between a few minutes and 24 h (from one cycle to the other). Echo-integration and inversion performed on the acoustic data as described in the companion paper of Leblond et al. (Mar Geophys Res, 2014), also indicate important variations in, respectively, the target strength and the volumetric flow rates of individual sources. However, the observed temporal variations may not be related to the properties of the gas source only, but reflect possible variations in sea-bottom currents, which could deviate the bubble train towards the neighboring sector. During the 2011 survey, a 4-component ocean bottom seismometer (OBS) was co-located at the seafloor, 59 m away from the BOB module. The acoustic data from our rotating, monitoring system support, but do not provide undisputable evidence to confirm, the hypothesis formulated by Tary et al. (2012), that the short-duration, non-seismic micro-events recorded by the OBS are likely produced by gas-related processes within the near seabed sediments. Hence, the use of a multibeam echosounder, or of several split beam echosounders should be preferred to rotating systems, for future experiments.  相似文献   

Climate change and warm‐water species at the north‐western boundary of the Mediterranean Sea          下载免费PDF全文

Valeriano Parravicini  Luisa Mangialajo  Laure Mousseau  Andrea Peirano  Carla Morri  Monica Montefalcone  Patrice Francour  Michel Kulbicki  Carlo Nike Bianchi 《Marine Ecology》2015,36(4):897-909

The effects of global change are particularly serious in areas where range shifts of species are physically constrained such as the Ligurian Sea, which is one of the coldest sectors of the Mediterranean. In this basin, historical information on water temperature (from the sea surface down to 75 m depth) dates back to the 1950s. Early studies also recorded warm‐water species occurrence. Thanks to these data we provide the first detailed characterization of water temperature variation from 1958 up to 2010 in the layer 0–75 m depth. We coupled this analysis with the available information on rocky reef epibenthic communities (literature review from 1955 to 1964 and field data from 1980 to 2010). The analysis of water temperature revealed several patterns of variation: a cooling phase from 1958 to 1980, a phase of rapid warming from 1980 to 1990 and a phase of slower warming from 1990 to 2010. Inter‐annual variation in temperature increased over the entire period for the water layer down to 20 m. Warm‐water native and alien species richness increased during the warming phases. Literature estimates suggest a decrease in warm‐water native species richness during the cooling phase. The analysis of quantitative data collected in the early 1990s and late 2000s indicated a decrease in the cover of warm‐water native species on shallow rocky reefs and an increase in deeper waters. We argue that increased inter‐annual variation in water temperature may disadvantage native warm‐water species in shallow waters. Our results indicate that the effect of temperature rises in cold, constrained basins may be more complex than the simple prediction of species changing their geographical range according to their thermal limits.  相似文献   

Abnormal weather events in 2009, increased precipitation and disastrous impacts in the Philippines     

Graciano P. Yumul Jr.  Carla B. Dimalanta  Nathaniel T. Servando  Nathaniel A. Cruz 《Climatic change》2013,118(3-4):715-727

The Philippines has recently experienced distinct changes in the weather patterns with disastrous results. These changes which were distinctly felt in 2009 included: 1. too much precipitation throughout the year; 2. some areas received a lot of rain while other parts of the country went through dry spell and drought conditions; and 3. abnormalities and variance in weather patterns (e.g. multiple entry of a tropical cyclone during an El Niño event; longer duration of tropical cyclone; deviations from the normal tropical cyclone path). The country, with its disaster risk management program in place, has managed to bring down the cost of damage and number of casualties due to weather-related disasters. However, in some instances, disaster risk response was made difficult due to other factors (e.g. degraded ecosystem, ill-managed land use and risk denial by people and communities). In general though, the resiliency and ability to recover by the people devastated by these disasters and the availability of community-based support systems provided the best means of coping with these catastrophic events. This is important as climate change is projected to bring more variations in the country’s weather and climate patterns which, as of now, are already adversely affecting the people.  相似文献   

Assessment of Fish Assemblages Before Dredging of the Shipping Channel Near the Mouth of the Savannah River in Coastal Georgia     

Jennifer A. Güt  Mary Carla Curran 《Estuaries and Coasts》2017,40(1):251-267

Evaluating the effects of anthropogenic activities is dependent upon data collection prior to impact, though funds are rarely allocated to conduct an assessment before a critical need arises. The Savannah Harbor Expansion Project is one such activity that includes dredging of the Savannah River. It may potentially change physical conditions of the estuary thereby altering fish assemblages. The purpose of the present study was to characterize pre-impact fish assemblages along a salinity gradient near the mouth of the river and determine which abiotic factors most influence them. One site within the mouth of the Savannah River and two sites immediately outside the river mouth were sampled monthly for 2 years using both a beam trawl and seine net. Salinity, temperature, dissolved oxygen, and sediment grain size were assessed. All four factors had a significant effect on fish assemblages. A total of 3943 fishes representing ≥55 species formed three statistically distinct fish assemblages and at least three seasonal assemblages. Only 24 species (43.6 %) were collected by both gear types indicating the importance of using multiple gear types to assess fish assemblages. We conclude that the fish assemblages near the mouth of the Savannah River may be altered or may shift given the predicted increase in salinity and/or the possible changes in sediment composition from channel dredging. Understanding the abiotic factors that most influence spatial and seasonal fish distributions prior to dredging will be invaluable in predicting how organisms will be impacted by similar public projects elsewhere.  相似文献   

Preliminary geochemical characterization of groundwater drained by the Roman emissary of Lake Albano (Italy)     

Paolo Madonia  Marianna Cangemi  Carla Galeazzi  Carlo Germani  Mario Parise  Rocco Favara 《Environmental Earth Sciences》2017,76(7):289

Many lakes have been the object of hydraulic works in historical times, and the drainage tunnel carved by Romans for regulating the level of Lake Albano (Central Italy) can be considered as one of the most important historical hydraulic tunnels in the world. We sampled and analysed lake water, as well as groundwater samples from the Lake Albano emissary and another hydraulic work in the area (Ninfeo), which were analysed for their geochemical and isotopic composition in order to extract useful information for a possible reuse of the tunnel for anthropogenic purposes. The collected water samples exhibit common chemical features, typical of water–rock interaction processes in volcanic areas. Analyses of minor and trace elements confirmed the abovementioned results, indicating the presence of an atmospheric pollution source for heavy metals, although their concentrations are mostly below the Maximum Admitted Concentrations for drinking water issued by the World Health Organization. The chemical composition of dissolved gases indicated that both lake and groundwater are mainly enriched in CO₂. Isotopic analyses suggested a clear volcanic origin for CO₂ dissolved in lake water, while carbon dioxide in groundwater from the Roman emissary is produced by soil respiration. As further confirmed by Oxygen and Deuterium isotopic composition, the Roman emissary drains local suspended aquifers neither in contact with the lake water body nor influenced by volcanic activity, suggesting the opportunity to use the tunnel as a “zero-condition” monitoring site for individuating a possible future renewal of volcanic activity.  相似文献   

Temporospatial dynamics and public health significance of bacterial flora identified on a major leatherback turtle (Dermochelys coriacea) nesting beach in the Southern Caribbean          下载免费PDF全文

Ayanna Carla N. Phillips  Johanna Coutou  Stacy Rajh  Neville Stewart  Antonio Watson  Adam Jehu  Hamish Asmath  Francis Dziva  Chandrashekhar Unakal  Ridley Holder  Raymond Raoul Carthy 《Marine Ecology》2017,38(2)

Grande Riviere beach, on the island of Trinidad, supports the largest nesting population of leatherback turtles in the Caribbean region. Throughout the nesting season, nests are naturally disturbed by newly nesting females, resulting in egg breakage and loss of some nest viability. This environment is ideal for the growth and proliferation of microorganisms. The range of bacterial flora present in beach sand and egg shells was examined, with emphasis on bacteria that may pose a threat to public and animal health. The extent to which the bacterial load and genera on the beach changed throughout the season was also assessed. Twenty‐five genera were identified, with Pseudomonas spp. found to be the most predominant environmental bacteria. Four genera identified possess zoonotic potential, while five additional genera are known to be of public and animal health significance. Distinct shifts in the density and distribution of bacteria were observed along the beach from early to peak nesting season. Shifts were seen across heavily traversed zones, thus highlighting the potential exposure threats posed to beach visitors and animals alike. Further studies aimed at speciating this population of bacteria, as well as isolating potential fungal pathogens may mitigate this threat. Identification of bacterial agents that are specifically pathogenic to leatherback turtles, turtle eggs, hatchlings and those who may interact with these animals will serve to enhance and guide efforts to better conserve this species and protect the health of all who visit this ecologically significant site.  相似文献