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1.
Annually integrated air-water CO2 flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO2 fluxes over the coastal ocean (26×106 km2), taking into account its geographical and ecological diversity. Air-water CO2 fluxes were then up-scaled in global ocean (362×106 km2) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×106 km2). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO2(−1.17 mol C m−2 yr−1) and the uptake of atmospheric CO2 by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr−1). The inclusion of the coastal ocean increases the estimates of CO2 uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr−1) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr−1) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO2 emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr−1). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO2 (0.38 mol C m−2 yr−1) and the uptake of atmospheric CO2 from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr−1) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO2 but at temperate latitudes, it still behaves as a moderate CO2 sink. A rigorous up-scaling of air-water CO2 fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO2 cycle.  相似文献   

2.
 This study re-estimates one important component in the global carbon cycle: the modern global fluviatile organic carbon discharge- and burial rates. According to these results, approximately 430×1012 g of terrestrial organic carbon are transported to the ocean in modern times. This amount is higher than the latest estimates but takes into account new data from Oceania not previously considered in global flux studies. However, only the minor amount of 10% or approximately 43×1012 gC year–1 is most likely buried in marine sediments. This amount is similar to the burial of marine organic carbon in the coastal ocean (55×1012 gC year–1). Adding both estimates gives approximately 100×1012 gC year–1, which is the value calculated by Berner (1982) for "terrestrial" deltaic-shelf sediments. However, the results in this study suggest that on a global scale the organic carbon content in coastal ocean sediments is not solely of terrestrial origin but a mixture of nearly equal amounts of marine and terrestrial organic carbon. The major part of the terrestrial organic carbon that enters the ocean by rivers (approximately 400×1012 gC year–1) seems to be either (a) remineralised in the ocean, whereas the mechanism by which the terrestrial organic carbon is oxidised in the ocean are unknown; or (b) is dispersed throughout the oceans and accumulates in pelagic sediments. Received: 9 November 1998 / Accepted: 25 May 1999  相似文献   

3.
Spatial patterns of estuarine biota suggest that some nearshore ecosystems are functionally linked to interacting processes of the ocean, watershed, and coastal geomorphology. The classification of estuaries can therefore provide important information for distribution studies of nearshore biodiversity. However, many existing classifications are too coarse-scaled to resolve subtle environmental differences that may significantly alter biological structure. We developed an objective three-tier spatially nested classification, then conducted a case study in the Alexander Archipelago of Southeast Alaska, USA, and tested the statistical association of observed biota to changes in estuarine classes. At level 1, the coarsest scale (100–1000’s km2), we used patterns of sea surface temperature and salinity to identify marine domains. At level 2, within each marine domain, fjordal land masses were subdivided into coastal watersheds (10–100’s km2), and 17 estuary classes were identified based on similar marine exposure, river discharge, glacier volume, and snow accumulation. At level 3, the finest scale (1–10’s km2), homogeneous nearshore (depths <10 m) segments were characterized by one of 35 benthic habitat types of the ShoreZone mapping system. The aerial ShoreZone surveys and imagery also provided spatially comprehensive inventories of 19 benthic taxa. These were combined with six anadromous species for a relative measure of estuarine biodiversity. Results suggest that (1) estuaries with similar environmental attributes have similar biological communities, and (2) relative biodiversity increases predictably with increasing habitat complexity, marine exposure, and decreasing freshwater. These results have important implications for the management of ecologically sensitive estuaries.  相似文献   

4.
The composition and distribution of diatom algae inhabiting estuaries and coasts of the subtropical Americas are poorly documented, especially relative to the central role diatoms play in coastal food webs and to their potential utility as sentinels of environmental change in these threatened ecosystems. Here, we document the distribution of diatoms among the diverse habitat types and long environmental gradients represented by the shallow topographic relief of the South Florida, USA, coastline. A total of 592 species were encountered from 38 freshwater, mangrove, and marine locations in the Everglades wetland and Florida Bay during two seasonal collections, with the highest diversity occurring at sites of high salinity and low water column organic carbon concentration (WTOC). Freshwater, mangrove, and estuarine assemblages were compositionally distinct, but seasonal differences were only detected in mangrove and estuarine sites where solute concentration differed greatly between wet and dry seasons. Epiphytic, planktonic, and sediment assemblages were compositionally similar, implying a high degree of mixing along the shallow, tidal, and storm-prone coast. The relationships between diatom taxa and salinity, water total phosphorus (WTP), water total nitrogen (WTN), and WTOC concentrations were determined and incorporated into weighted averaging partial least squares regression models. Salinity was the most influential variable, resulting in a highly predictive model (r apparent2 = 0.97, r jackknife2 = 0.95) that can be used in the future to infer changes in coastal freshwater delivery or sea-level rise in South Florida and compositionally similar environments. Models predicting WTN (r apparent2 = 0.75, r jackknife2 = 0.46), WTP (r apparent2 = 0.75, r jackknife2 = 0.49), and WTOC (r apparent2 = 0.79, r jackknife2 = 0.57) were also strong, suggesting that diatoms can provide reliable inferences of changes in solute delivery to the coastal ecosystem.  相似文献   

5.
 The total amount of groundwater resources in the middle and upper Odra River basin is 5200×103 m3/d, or about 7.7% of the disposable groundwater resources of Poland. The average modulus of groundwater resources is about 1.4 L/s/km2. Of the 180 'Major Groundwater Basins' (MGWB) in Poland, 43 are partly or totally located within the study area. The MGWB in southwestern Poland have an average modulus of groundwater resources about 2.28 L/s/km2 and thus have abundant water resources in comparison to MGWB from other parts of the country. Several types of mineral waters occur in the middle and upper Odra River basin. These waters are concentrated especially in the Sudety Mountains. Carbon-dioxide waters, with yields of 414 m3/h, are the most widespread of Sudetic mineral waters. The fresh waters of the crystalline basement have a low mineralization, commonly less than 100 mg/L; they are a HCO3–Ca–Mg or SO4–Ca–Mg type of water. Various hydrochemical compositions characterize the groundwater in sedimentary rocks. The shallow aquifers are under risk of atmospheric pollution and anthropogenic effects. To prevent the degradation of groundwater resources in the middle and upper Odra River basin, Critical Protection Areas have been designated within the MGWB. Received, January 1995 Revised, May 1996, August 1997 Accepted, August 1997  相似文献   

6.
中国海岸带地质资源与环境评价研究   总被引：3，自引：1，他引：2       下载免费PDF全文
海岸带是中国社会经济发展的前沿地带,人口密度最大、城镇化程度最高,在中国海洋强国战略中发挥重要的支撑作用,同时也是中国资源环境压力最大的区域。本文在全面分析近20年来中国海岸带地质资源环境调查成果的基础上,系统梳理了海岸带地区地质资源环境优势和存在的地质环境问题。中国海岸带地质资源环境优势突出,为绿色发展提供了良好条件,重要地质资源环境优势包括:1.2×10~4km~2滩涂后备土地资源可适度开发,以缓解海岸带建设用地紧张局面;2.8×10~4km~2绿色富硒土地和4.1×10~5km~2绿色渔场,适宜发展绿色特色农业和建设海洋牧场;浅层地温能和地热水年可开采量折合标准煤4.2×10~8t,对改善能源结构、减少大气污染有重要作用;5.8×10~4km~2滨海湿地和134处国家级和世界级地质遗迹资源,为海岸带生态文明建设提供了条件;90%的陆域适宜城镇和重大工程规划建设,地下空间开发条件较好,为海岸带地质安全提供了保障。存在的主要环境问题包括:海岸带局部存在活动断裂、地面沉降、地面塌陷、海岸侵蚀淤积、风暴潮等重大地质问题,对部分城市与重要基础设施形成威胁,局部地区水、土污染及海水入侵严重,需要高度重视。建议加大海岸带多学科综合地质调查,构建多要素、多圈层、多维度地质模型,查明自然灾害发生的规律和原因,减轻对人民生命财产造成的损失。  相似文献   

7.
Summary ?Rocks containing braunite from the Ossa-Morena central belt (Iberian Massif, SW Spain) have been studied; these include nodules and layers of braunite (association I), Mn-slates (association II) and Mn-metatuffs (associations III and IV). Geochemical features of braunite nodules such as Mn/Fe ratios around 2, positive Ce-anomalies and good correlations among Mn, Fe, Co, Cu and REE contents indicate that the protolith of the braunite-nodules was precipitated from oxidising sea water. Greenschist facies Hercynian metamorphism reduced initial Mn4+ to Mn3+ and Mn2+. High initial fO2 of oxide beds (association I) limited reduction to the formation of braunite. Reduction continued until the formation of garnet + piemontite (associations II and III), and pyroxmangite + pyrophanite (association IV). Ti-rich braunites (up to 6.8% of TiO2) occur in slates and metatuffs in which the (Mn + Fe)/Ti ratio of the whole rock is lower than 30, while braunites have lower Ti contents in slates and metatuffs with (Mn + Fe)/Ti ratios around 90. Fe-rich braunite crystallized in rocks with Mn2+ oxide and silicate where low Mn3+/Mn2+ in the whole rock facilitated substitution of Fe3+ for Mn3+. Received January 30, 2002; revised version accepted May 7, 2002 Published online November 22, 2002  相似文献   

8.
We measured seasonal variations in microzooplankton grazing in Long Island Sound (LIS) and San Francisco Bay (SFB). There was consistent evidence of nutrient limitation in LIS, but not SFB. We found higher chlorophyll a concentrations in LIS compared with SFB. In spite of differences in phytoplankton, there were no differences in microzooplankton abundance (summer: LIS, 12.4 ± 1.8 × 103 indiv. L−1; SFB, 14.1 ± 3.0 × 103 indiv. L−1), biomass (summer: LIS, 30.4 ± 5.0 μg C L−1; SFB, 26.3 ± 5.9 μg C L−1), or grazing rates (summer: LIS, 0.66 ± 0.19 day−1; SFB, 0.65 ± 0.18 day−1) between the two estuaries. In common with many other investigators, we found many instances of saturated as well as insignificant grazing. We suggest that saturation in some cases may result from high particle loads in turbid estuarine systems and that insignificant grazing may result from extreme saturation of the grazing response due to the need to process non-food particles.  相似文献   

9.
A new classification of coastal wetlands along the coast of China has been generated that is compatible with the Ramsar Convention of 1971. The coastal wetlands have been divided into two broad categories with overall nine subcategories. On this basis, a series of coastal wetland maps, together covering the coast of mainland China, have been produced based on topographic maps acquired in the 1970s and satellite images acquired in 2007. These document substantial wetland losses over this period. In the 1970s, the total coastal wetland area in China was 5.76?×?104?km2, whereas in 2007, it was 5.36?×?104?km2, indicating a loss of 7 %. Over this approximately 40-year period, the area of natural coastal wetlands decreased from 5.74?×?104 to 5.09?×?104?km2, while that of artificial coastal wetlands increased from 240 to 2,740 km2. Due to shoreline and sea-level changes, newly formed coastal wetlands amounted to 2,460 km2, while coastal wetland loss amounted to 6,310 km2 in the period from the 1970s to 2007. When excluding shallow coastal waters (depths between 0 and ?5 m), nearly 16 % of Chinese coastal wetlands have been lost between the 1970s and 2007.  相似文献   

10.
 Impact of catchment erosion and the resultant reservoir siltation from a tropical environment is reported here to discuss the effect of a reservoir in the natural degradation of an evergreen-forested segment. While an area of 8.01 km2 has been affected by direct inundation at the full reservoir level, another 2.6 km2 area once under thick forest cover, had also lost its identity over the last 38 years by indirect degradation. This zone mainly falls in the confluence of tributaries, namely Neyyar and Mullayar, with the reservoir. The capacity of the reservoir was found to be reduced by 28.8 Mm3 during this period and the annual average loss is calculated as 0.75 Mm3 (0.71%), indicating the intensity of erosion from the catchment zone. In case the proposed upper dam in the reservoir comes into existence, an additional area of 2.4 km2 from the virgin forest would be submerged and more area would face degradation around the inundated zone. Received: 29 July 1998 · Accepted: 16 November 1998  相似文献   

11.
A suite of more than 200 garnet single crystals, extracted from 150 xenoliths, covering the whole range of types of garnet parageneses in mantle xenoliths so far known from kimberlites of the Siberian platform and collected from nearly all the kimberlite pipes known in that tectonic unit, as well as some garnets found as inclusions in diamonds and olivine megacrysts from such kimberlites, were studied by means of electron microprobe analysis and single-crystal IR absorption spectroscopy in the v OH vibrational range in search of the occurrence, energy and intensity of the v OH bands of hydroxyl defects in such garnets and its potential use in an elucidation of the nature of the fluid phase in the mantle beneath the Siberian platform. The v OH single-crystal spectra show either one or a combination of two or more of the following major v OH bands, I 3645–3662 cm−1, II 3561–3583 cm−1, III 3515–3527 cm−1, and minor bands, Ia 3623–3631 cm−1, IIa 3593–3607 cm−1. The type of combination of such bands in the spectrum of a specific garnet depends on the type of the rock series of the host xenolith, Mg, Mg-Ca, Ca, Mg-Fe, or alkremite, on the xenolith type as well as on the chemical composition of the respective garnet. Nearly all garnets contain band systems I and II. Band system III occurs in Ti-rich garnets, with wt% TiO2 > ca. 0.4, from xenoliths of the Mg-Ca and Mg-Fe series, only. The v OH spectra do not correspond to those of OH− defects in synthetic pyropes or natural ultra-high pressure garnets from diamondiferous metamorphics. There were no indications of v OH from inclusions of other minerals within the selected 60 × 60 μm measuring areas in the garnets. The v OH spectra of pyrope-knorringite- and pyrope-knorringite-uvarovite-rich garnets included in diamonds do not show band systems I to III. Instead, they exhibit one weak, broad band (Δv OH 200–460 cm−1) near 3570 cm−1, a result that was also obtained on pyrope-knorringite-rich garnets extracted from two olivine megacrysts. The quantitative evaluation, on the basis of relevant existing calibrational data (Bell et al. 1995), of the sum of integral intensities of all v OH bonds of the garnets studied yielded a wide range of “water” concentrations within the set of the different garnets, between values below the detection limit of our single-crystal IR method, near 2 × 10−4 wt%, up to 163 × 10−4 wt%. The “water” contents vary in a complex manner in garnets from different xenolith types, obviously depending on a large number of constraints, inherent in the crystal chemistry as well as the formation conditions of the garnets during the crystallization of their mantle host rocks. Secondary alteration effects during uplift of the kimberlite, play, if any, only a minor role. Despite the very complex pattern of the “water” contents of the garnets, preventing an evaluation of a straightforward correlation between “water” contents of the garnets and the composition of the mantle's fluid phase during garnet formation, at least two general conclusions could be drawn: (1) the wide variation of “water” contents in garnets is not indicative of regional or local differences in the composition of the mantle's fluid phase; (2) garnets formed in the high-pressure/high-temperature diamond-pyrope facies invariably contain significantly lower amounts of “water” than garnets formed under the conditions of the graphite-pyrope facies. This latter result (2) may point to significantly lower f H2O and f O2 in the former as compared to the latter facies. Received: 25 November 1997 / Accepted: 9 March 1998  相似文献   

12.
The eastern Alaska Beaufort Sea coast is characterized by numerous shallow (2–5 m) estuarine lagoons, fed by streams and small rivers that drain northward from the Brooks Range through the arctic coastal plain, and bounded seaward by barrier islands and shoals. Millions of birds from six continents nest and forage during the summer period in this region using the river deltas, lagoons, and shoreline along with several species of anadromous and marine fish. We examined biogeochemical processes linking the benthic community to the overall food web structure of these poorly studied but pristine estuaries, which are largely covered by 1.8 m of ice for 10 months annually. In summer, these lagoons are relatively warm with brackish salinities (5–10°C, S = 10–25) compared to more open coastal waters (0–5°C, S > 27). The stable isotopic composition of organic materials in sediments (i.e., benthic particulate organic matter) and water column suspended particulate organic matter from both streams and lagoons are largely indistinguishable and reflect strong terrestrial contributions, based upon δ13C and δ15N values (−25.6‰ to −27.4‰ and 1.4‰ to 3.3‰, respectively). By comparison, shifts toward more heavy isotope-enriched organic materials reflecting marine influence are observed on the adjacent coastal shelf (−24.8‰ to −25.4‰ and 3.4‰ to 5.3‰, respectively). The isotopic composition of lagoon fauna is consistent with a food web dominated by omnivorous detritovores strongly dependent on microbial processing of terrestrial sources of carbon. Biomagnification of 15N in benthic organisms indicate that the benthic food web in lagoons support up to four trophic levels, with carnivorous gastropod predators and benthic fishes (δ15N values up to 14.4‰) at the apex.  相似文献   

13.
The spatiotemporal evolution of sea ice of Bohai Sea in the 2009–2010 winter was studied by time-series remote sensing data, and real-time meteorological data in combination with cumulative freezing degree days (CFDD). Sea ice acreage was determined using a ratio-threshold segmentation together with visual interpretation of daily MODIS 250 m imagery. We found the sea ice acreage soared to 31,849 km2 on January 23, covering 40.8% of the Bohai Sea. But on February 12, it reached 26,700 km2 in Liaodong Bay only, covering almost 90.0% of Liaodong Bay. The rapid formation and expansion of sea ice was caused by continuous cold snaps superimposed on a background of anomalously cold weather. CFDD calculated from surrounding cities highly correlated with sea ice acreage in Liaodong Bay (R 2 = 0.72) suggesting CFDD is one of the significant controlling factors. Sea ice expansion showed 7 days lag with respect to the lowest temperature from surrounding coastal cities, and it mainly occurred close to land, along the coastline, and gradually expanded from the shore outwards.  相似文献   

14.
Water quality monitoring in Hanalei Bay, Kaua`i (Hawai`i, USA) has documented intermittent high concentrations of nutrients (nitrate, phosphate, silica, and ammonium) and fecal indicator bacteria (FIB, i.e., enterococci and Escherichia coli) in nearshore waters and spurred concern that contaminated groundwater might be discharging into the bay. The present study sought to identify and track sources of nutrients and FIB to four beaches in Hanalei Bay and one beach outside the bay, together representing a wide range of land uses. 223Ra and 224Ra activity, salinity, nutrient and FIB concentrations were measured in samples from the coastal aquifer, the nearshore ocean, springs, the Hanalei River, and smaller streams. In addition, FIB concentrations in beach sands were measured at each site, and the enterococcal surface protein (esp) gene assay was used to investigate whether the observed FIB originated from a human source. Nutrient concentrations in groundwater were significantly higher than in nearshore water, inversely correlated to salinity, and highly site specific, indicating local controls on groundwater quality. Fluxes of groundwater into Hanalei Bay were calculated using a mass-balance approach and represented at least 2–10% of river discharges. However, submarine groundwater discharge (SGD) may provide 2.7 times as much nitrate + nitrite to Hanalei Bay as does the Hanalei River. It may also provide significant fluxes of phosphate and ammonium, comprising 15% and 20% of Hanalei River inputs, respectively. SGD-derived silica inputs to the bay comprised less than 3% of Hanalei River inputs. FIB concentrations in groundwater were typically lower than those in nearshore water, suggesting that significant FIB inputs from SGD are unlikely. Positive esp gene assays suggested that some enterococci in environmental samples were of human fecal origin. Identifying how nutrients and FIB enter nearshore waters will help environmental managers address pressing water quality issues, including exceedances of the state Enterococcus water quality standard and nutrient loading to coral reefs.  相似文献   

15.
 Unit-cell dimensions of a natural phlogopite from Pargas, Finland, have been determined in the temperature interval of 27–1050 °C by X-ray powder diffraction technique. Expansion rates vary discontinuously with temperature with a break at 412 °C. Below this temperature, the linear expansions (α) for a, b and c axis lengths are 3.74 × 10−5 K−1, 1.09 × 10−5 K−1, and 1.19 × 10−5 K−1, respectively, and above that they are 0.86 × 10−5 K−1, 0.80 × 10−5 K−1, and 1.93 × 10−5 K−1. The volume thermal expansion coefficients are 6.26 × 10−5 K−1 and 3.71 × 10−5 K−1 for low-temperature and high-temperature intervals, respectively. The observed kink in the rate of thermal expansions with temperature could be due to the different mode of structural changes. Thermogravimetric analysis of the sample indicates the oxidation of iron in the temperature range of 500–600 °C and dehydroxylation as well as decomposition of phlogopite in the temperature range of 900–1200 °C. Received: 8 September 1998 / Accepted: 28 February 2000  相似文献   

16.
The nearshore land-water interface is an important ecological zone that faces anthropogenic pressure from development in coastal regions throughout the world. Coastal waters and estuaries like Chesapeake Bay receive and process land discharges loaded with anthropogenic nutrients and other pollutants that cause eutrophication, hypoxia, and other damage to shallow-water ecosystems. In addition, shorelines are increasingly armored with bulkhead (seawall), riprap, and other structures to protect human infrastructure against the threats of sea-level rise, storm surge, and erosion. Armoring can further influence estuarine and nearshore marine ecosystem functions by degrading water quality, spreading invasive species, and destroying ecologically valuable habitat. These detrimental effects on ecosystem function have ramifications for ecologically and economically important flora and fauna. This special issue of Estuaries and Coasts explores the interacting effects of coastal land use and shoreline armoring on estuarine and coastal marine ecosystems. The majority of papers focus on the Chesapeake Bay region, USA, where 50 major tributaries and an extensive watershed (~ 167,000 km2), provide an ideal model to examine the impacts of human activities at scales ranging from the local shoreline to the entire watershed. The papers consider the influence of watershed land use and natural versus armored shorelines on ecosystem properties and processes as well as on key natural resources.  相似文献   

17.
Atmospheric deposition of nitrogen (AD-N) is a significant source of nitrogen enrichment to nitrogen (N)-limited estuarine and coastal waters downwind of anthropogenic emissions. Along the eastern U.S. coast and eastern Gulf of Mexico, AD-N currently accounts for 10% to over 40% of new N loading to estuaries. Extension of the regional acid deposition model (RADM) to coastal shelf waters indicates that 11, 5.6, and 5.6 kg N ha−1 may be deposited on the continental shelf areas of the northeastern U.S. coast, southeast U.S. coast, and eastern Gulf of Mexico, respectively. AD-N approximates or exceeds riverine N inputs in many coastal regions. From a spatial perspective, AD-N is a unique source of N enrichment to estuarine and coastal waters because, for a receiving water body, the airshed may exceed the watershed by 10–20 fold. AD-N may originate far outside of the currently managed watersheds. AD-N may increase in importance as a new N source by affecting waters downstream of the oligohaline and mesohaline estuarine nutrient filters where large amounts of terrestrially-supplied N are assimilated and denitrified. Regionally and globally, N deposition associated with urbanization (NOx, peroxyacetyl nitrate, or PAN) and agricultural expansion (NH4 + and possibly organic N) has increased in coastal airsheds. Recent growth and intensification of animal (poultry, swine, cattle) operations in the midwest and mid-Atlantic regions have led to increasing amounts of NH4 + emission and deposition, according to a three decadal analysis of the National Acid Deposition Program network. In western Europe, where livestock operations have dominated agricultural production for the better part of this century, NH4 + is the most abundant form of AD-N. AD-N deposition in the U.S. is still dominated by oxides of N (NOx) emitted from fossil fuel combustion; annual NH4 + deposition is increasing, and in some regions is approaching total NO3 − deposition. In receiving estuarine and coastal waters, phytoplankton community structural and functional changes, associated water quality, and trophic and biogeochemical alterations (i.e, algal blooms, hypoxia, food web, and fisheries habitat disruption) are frequent consequences of N-driven eutrophication. Increases in and changing proportions of various new N sources regulate phytoplankton competitive interactions, dominance, and successional patterns. These quantitative and qualitative aspects of AD-N and other atmospheric nutrient sources (e.g., iron) may promote biotic changes now apparent in estuarine and coastal waters, including the proliferation of harmful algal blooms, with cascading impacts on water quality and fisheries.  相似文献   

18.
We compared the extent to which ancient and restoring wetlands in three estuary regions of San Francisco Bay support estuarine ecosystems through food web contributions. In comparison to mature marshes, we hypothesized that food webs of increasingly younger restoration sites would display increased dependency upon allochthonous subsidies due to nominal internal production. Using multiple stable isotopes (δ13C, δ15N, δ34S) in a mixing model, we traced links among primary producers and estuarine consumers. Results indicate that food webs of estuarine marshes are heavily dependent upon autochthonous marsh materials (76 ± 17%), even within the youngest restoration marshes (11 years). Nearly all sampled organisms relied upon autochthonous marsh materials, with the exception of Neomysis kadiakensis, a mysid shrimp, which derived the majority of its support from freshwater-produced phytoplankton. Marsh-derived organic matter (OM) support was consistent both temporally throughout the year and spatially along the three estuary regions, but evidence suggests that the specific type of OM supporting estuarine consumers depends on position along the estuarine gradient and on seasonal shifts in freshwater flow. These results indicate that wetland restoration rapidly provides important contributions to marsh consumers and potentially bolsters food web linkages in shallow-water ecosystems.  相似文献   

19.
Summary The complexation of aluminium(III) and silicon(IV) was studied in a simplified seawater medium (0.6 M Na(Cl)) at 25 °C. The measurements were performed as potentiometric titrations using a hydrogen electrode with OH − ions being generated coulometrically. The total concentrations of Si(IV) and Al(III) respectively [Si tot ] and [Al t ot], and −log[H +] were varied within the limits 0.3 < [Si tot ] < 2.5 mM, 0.5 < [Al tot ] < 2.6 mM, and 2 ≤ -log[H +] ≤ 4.2. Within these ranges of concentration, evidence is given for the formation of an AlSiO(OH) 3 2+ complex with a formation constant log β1,1-1 = −2.75 ± 0.1 defined by the reaction Al 3++Si (OH)4 ↔ AlOSi(OH) 3 2+ +H + An extrapolation of this value to I=0 gives log β1,1-1 = −2.30. The calculated value of log K (Al 3++SiO(OH) 3 − ↔ AlOSi(OH) 3 2+ ) = 6.72 (I=0.6 M) can be compared with corresponding constants for the formation of AlF 2+ and AlOH 2+ , which are equal to 6.16 and 8.20. Obviously, the stability of these Al(III) complexes decreases within the series OH −>SiO(OH) 3 −  > F −  相似文献   

20.
青藏高原东部长江流域盆地陆地化学风化研究   总被引：4，自引：0，他引：4  
长江河水主要离子由流域盆地碳酸盐岩的风化所控制,沱沱河和楚玛尔河受蒸发盐岩影响较为明显;河水溶质载荷Si,Si/TZ *,Si/(Na* K)等指标表明,长江流域盆地地表硅酸盐岩风化还是浅表层次的;金沙江地表化学剥蚀速率为1.74×103mol/yr.km2,雅砻江为1.69×103mol/yr.km2,大渡河为1.57×103mol/yr.km2,岷江为1.88×103mol/yr.km2,长江河源区楚玛尔河为2.32×103mol/yr.km2,沱沱河为1.37×103mol/yr.km2,流域地表化学剥蚀速率可与世界上其它造山带的河流进行对比。  相似文献   

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