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The aim of this work was to study seasonal variation of histopathological and histochemical markers in blue mussels (Mytilus edulis L.) exposed to pyrogenic PAH contaminants. Mussels were collected in January, June, September and October from a sampling site in the vicinity of the discharge from an aluminium smelter and from a clean reference site. Histopathological analysis was carried out on the digestive gland (DG) and the gonads, lipofuscin and neutral lipids were analysed in the DG. Clear responses in lipofuscin and neutral lipids were detected in the DG of mussels collected from the polluted site at some sampling times. Moreover, these mussels presented atrophy in digestive tubules and haemocytic aggregates in the gonad and DG. However, in all parameters studied, the magnitude of the response showed clear seasonal variation. 相似文献
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D. Lirman T. Thyberg R. Santos S. Schopmeyer C. Drury L. Collado-Vides S. Bellmund J. Serafy 《Estuaries and Coasts》2014,37(5):1243-1255
Nearshore benthic habitats of Biscayne Bay fit the prediction of communities at risk due to their location adjacent to a large metropolitan center (Miami) and being influenced by changes in hydrology through the activities of the Comprehensive Everglades Restoration Plan (CERP). We examine whether the proposed programmatic expansion of mesohaline salinities through the introduction of additional fresh water would result in: (1) increases in seagrass cover; (2) expansion in the distribution and cover of Halodule; and (3) a reduction in the dominance of Thalassia, as hypothesized by CERP. Seagrasses were present at 98 % of sites where they covered 23 % of the bottom. Salinity was the only physical variable with a significant relationship to the occurrence of all SAV taxa. Occurrence of Thalassia, Halimeda, and Penicillus increased significantly with increasing salinity, but Halodule, Syringodium, Laurencia, Udotea, Batophora, Caulerpa, and Acetabularia showed a significant negative relationship with salinity. Mesohaline habitats had higher cover of seagrass and Halodule, and reduced dominance by Thalassia. Thus, we expect increases in the extent of mesohaline habitats to achieve the established CERP goals. We also examined the nutrient content of seagrass blades to evaluate whether: (1) nutrient availability is higher in areas close to canal discharges; and (2) tissue nutrient levels are related to seagrass abundance. The low abundance of Thalassia along the shoreline is not only due to its exclusion from low-salinity environments but also by higher nutrient availability that favors Halodule. Percent N and P, and N:P ratios in seagrass tissue suggest that Biscayne Bay receives high N inputs and is P-limited. Thus, increased P availability may facilitate an expansion of Halodule. The data presented suggest that increased mesohaline salinities will increase seagrass abundance and support co-dominance by Halodule and Thalassia as hypothesized, but raise concerns that current high N availability and increases in P may prompt a shift away from seagrass-dominated to algal-dominated communities under scenarios of enhanced fresh water inputs. 相似文献
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Flow of fluids and transport of solutes in porous media are subjects of wide interest in several fields of applications: reservoir
engineering, subsurface hydrology, chemical engineering, etc. In this paper we will study two-phase flow in a model consisting
of two different types of sediments. Here, the absolute permeability, the relative permeabilities and the capillary pressure
are discontinuous functions in space. This leads to interior boundary value problems at the interface between the sediments.
The saturation Sw will be discontinuous or experience large gradients at the interface. A new solution procedure for such problems will be
presented. The method combines the modified method of characteristics with a weak formulation where the basis functions are
discontinuous at the interior boundary. The modified method of characteristics will provide a good first approximation for
the jump in the discontinuous basis functions, which leads to a fast converging iterative solution scheme for the complete
problem.
The method has been implemented in a two-dimensional simulator, and results from numerical experiments will be presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Brit Shay-Margalit 《社会与自然资源》2017,30(1):112-128
The objective of this study was to explore the mechanism through which a reform in environmental education (EE) programs affects pupils’ relation to the environment. We surveyed 589 pupils aged 9–12 years in three types of Israeli elementary school: regular schools, schools that implement an EE program (designated “green schools”), and schools that implement a more intensive EE program (designated “persistent green schools”). Analyzing the results obtained from our questionnaire, we found that both EE programs had a positive effect on environmental attitudes. Importantly, however, only persistent green schools showed a direct positive effect on environmental behavior. In addition, we assessed the influences of various demographic and other factors on pupils’ relation to the environment. Of note, we found that students who spent their leisure time watching TV or engaging with other electronic media expressed less concern about the environment. 相似文献
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Hans-Christian Teien Brit Salbu Frode Kroglund Lene Sørlie Heier Bjørn Olav Rosseland 《Applied Geochemistry》2007
Cationic Al species (Ali) cause toxic effects towards fish in acidified water. As several factors can influence the Ali-speciation, acid neutralising capacity (ANC) has been applied as an alternative indicator for acidification and effects towards fish. However, the critical range of ANC for biological stress has been shown to be dependent upon the concentration of organic material (DOC). Using in situ size fractionation techniques the influence of particulate and colloidal DOC (0–400 μM) on Ali-speciation and ANC-values was investigated in Norwegian streams. During high flow events with high river transport of DOC the Ali concentration increased by a factor of 2 due to retention of colloidal Al species (>10 kDa), probably organic, in the chromatography column. Ultrafiltration (?10 kDa) of water prior to chromatography reduced the influence of non-toxic organic Al-species, on Ali-speciation. The charge balanced ANC-values (ANCcb) were also significantly lower (on average 34 μeq L−1) in ultrafiltered water compared to unfiltered water samples, as base cations were associated with colloidal DOC (>10 kDa to 0.45 μm) and organic acids were not incorporated in the ANCcb estimate. Thus, ANCcb will underestimate the acidification effects towards fish in organic waters increasing with concentration of colloidal DOC present. Alkalinity based ANC-values (ANCalk), which include a fraction of organic acids, were similar in unfiltered and ultrafiltered waters, but higher than ANCcb-values of ultrafiltered samples. Thus, ANCalk-values also underestimate the acidification effects on fish in organic waters. Based on ultrafiltered samples, however, ANCcb-values was negatively correlated with Ali independent of the DOC present and thus a more correct indicator for toxic Al-species. 相似文献
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Brit Thyberg Jens JahrenTurid Winje Knut BjørlykkeJan Inge Faleide Øyvind Marcussen 《Marine and Petroleum Geology》2010
Late Cretaceous mudstones from two wells located in the northern North Sea and the Norwegian Sea have been examined with respect to quartz cement. Two different types of quartz cement (Type 1 and Type 2) have been identified using SEM/EDS/CL-analysis of drill-bit cuttings at depths 2370–2670 m (80–85 °C). Type 1 appears as relatively large aggregates (30–100 μm) of depth/temperature related crypto- or microcrystalline to macrocrystalline irregular quartz cement formed by local re-crystallization of biogenic silica. The CL-responses of Type 1 quartz cement give a clear indication of an authigenic origin. Type 2 quartz cement represents relatively high amounts of extremely fine-grained micro-sized (1–3 μm) crystals embedded as discrete, short chains or small clusters/nests within the illitized clay matrix. The CL-responses of micro-quartz crystals indicate an authigenic origin. The micro-quartz is most probably sourced from silica released during the smectite to illite dissolution–precipitation reaction. The petrographic evidence indicates that most of the silica released by the smectite to illite reaction has not been exported out of the mudstones. The silica released produce a subtle inter-connected micro-quartz network interlocked with aggregates of micro-quartz and authigenic clay crystals. This micro-quartz cementation process causes a significant and sharp change in the mudstone stiffness at the onset of the chemical compaction regime. This is indicated by an abrupt increase in well log velocity (Vp) and change in seismic facies close to 2500 m (80/85 °C). 相似文献
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