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201.
《Limnologica》2016
Mechanical and biological processing in aquatic systems converts coarse particulate organic matter (CPOM) into fine particulate organic matter (FPOM). Other sources of particles with different size classes include flocculated dissolved matter, algae and soil particles. The relative magnitudes of these inputs are influenced by the degree of allochthony of a lake or stream. The size-reactivity hypothesis, formulated for dissolved organic matter, postulates that bacterial degradation rates are higher with high-molecular-weight fractions than with low-molecular-weight fractions. In this study, we investigated the effect of particle size on degradation of POM and on freshwater bacterial communities. We generated leaf-derived particle size classes of the same age (same diagenesis status) but differing in quality (maple and beech leaves). Contrary to our expectations, we found a strong effect of particle size and no significant effect of substrate quality on community respiration which decreased at smaller particle size, on C:N ratios which declined with particle size, and on δ15 N which showed a decreasing trend (though not significant) at smaller particle size in beech leaves. By contrast, bacterial community structure and ∂13C values responded mainly to particle quality. Bacterial biomass, estimated by qPCR, was affected by complex interactions between particle size and quality. These findings open an unanticipated perspective on the size-reactivity hypothesis for particulate organic matter. 相似文献
202.
Characterization of transboundary POP contamination in aquatic ecosystems of Pearl River delta 总被引:5,自引:0,他引:5
Chau KW 《Marine pollution bulletin》2005,51(8-12):960-965
During the past two decades, the rapid development of the Pearl River delta leads to substantial accumulation of various toxic organic compounds. This study aims to give a preliminary characterization of the existing state of contamination in this region and to provide insight into the possible fate of persistent organic pollutants (POPs) in this estuary. The available data on POPs in water, river, estuarine sediments, soil, and marine organisms within the Pearl River delta are compiled. It is shown that it may lead to transboundary POP pollution problems at both Hong Kong and Macau Special Administration Regions located at the downstream end of the region. It is noted that the levels of DDTs and HCHs in various environmental media are at alerting levels and that fresh DDT might still be applied illegally within the region. A systematic research is required to determine both the temporal and spatial variations of all POPs in various carrying media of the Pearl River delta as a whole. 相似文献
203.
Seasonal Occurrence of Species of Saprolegniales and Leptomitales in Lake Aue and the River Fulda in Kassel (Hesse) with Special Consideration of Fish Pathogenic Species In this study, we examined the occurrence of species of aquatic Oomycetes of Saprolegniales und Leptomitales in Lake Aue and the river Fulda in Kassel (Hesse, Germany) with special consideration of fish pathogenic species. We monthly collected water samples of both water bodies from July 2003 to June 2004. The baiting method was used to gain an insight into the specific seasonal occurrence of aquatic Oomycetes. Some species show a seasonal periodicity. Nine of 11 species of Saprolegniales isolated from the two water bodies, and Leptomitus lacteus (Roth) C. Agardh, one of the two species of Leptomitales, were already documented on fish according to references. Additionally, 7 of 10 species could according to references already be detected on fish species present in the two water bodies. Simultaneous measurements of limnological‐chemical parameters were done during the sampling of water for the isolation of aquatic Oomycetes. The results of some measurements, concerning the river Fulda, were additionally compared with the predetermined guideline values and limit values of water bodies of fish of the “Cyprinid region”. 相似文献
204.
Yan Zhao Carl D. Sayer Hilary H. Birks Michael Hughes Sylvia M. Peglar 《Journal of Paleolimnology》2006,35(2):335-350
We have explored the contemporary spatial relationship between aquatic vegetation and surficial macrofossil and pollen remains
in a small, shallow, English lake. A detailed point-based (n = 87) underwater vegetation survey was undertaken in the middle of the plant-growing season in July 2000. Then following
plant die-back in November 2000, surface sediment samples (upper 1.5 cm) were collected from 30 of these plant survey points
and analysed for plant macro-remains (all 30 samples), and pollen (4 evenly spaced samples). All data were stored as separate
layers in a geographical information system and spatial relationships between the aquatic vegetation and plant remains were
explored. In contrast to pollen types, plant macrofossils were not evenly dispersed across all parts of the lake and, with
the exception of Chara oospores, higher concentrations of remains (particularly for Potamogeton) were found close to areas of source-plant dominance. The spatial pattern of macrophyte–macrofossil relationships revealed
that vegetative remains (particularly leaf fragments) were probably deposited at source, whereas seeds were recovered close
to the shore suggesting slightly wider dispersal. Overall, however, macro-remains best represented local ‘patch-scale’ vegetation
within 20–30 m of the core site. The macro-remains effectively recorded the dominant plants in the lake with 63% of samples
containing a combination of remains of Chara, Elodea, and Potamogeton. However, relationships between macrophytes and fossils were complex. Some species were significantly over-represented by
macrofossils (e.g., Chara spp., Nitella flexilis agg., and Zannichellia palustris), while others were either under-represented (e.g., Potamogeton spp.), or not represented at all (e.g., Lemna trisulca). Pollen represented macrophyte diversity poorly, but some taxa were found (e.g., Myriophyllum spicatum, Ceratophyllum demersum) that were not recorded by macro-remains. We conclude that macrofossil analysis may be very usefully employed to determine
the dominant taxa in past aquatic plant communities of shallow, productive lakes and that the addition of pollen analysis
provides further information on former species richness. 相似文献
205.
Ballast water is a major pathway for the transfer of non-indigenous species in aquatic environments. The objectives of this study were to determine the ability of ozone to reduce the numbers of a spectrum of marine organisms collected from Puget Sound, Washington in replicated mesocosm (280 l) experiments, and estimate the minimum ozone concentrations as measured by total residual oxidant (TRO) required to reduce organism densities. Ozone treatment was effective in removing bacteria, phytoplankton, and mesozooplankton with initial TRO concentrations of 2–5 mg l−1 as Br2. Persistence of TRO resulted in an extended period of toxicity and cumulative mortality. TRO decay allowed bacteria populations to multiply when TRO levels fell below 0.5–1.0 mg l−1 as Br2. Phytoplankton chlorophyll a concentrations were rapidly reduced by ozone treatment and did not increase in any treatments or controls because of lack of light. Overall mesozooplankton viability was rapidly reduced by 90–99% in treatment TRO levels above 1.85 mg l−1 as Br2. Our study outlines novel protocols that can be used for testing different potential ballast water treatment systems in replicated and controlled mesocosm experiments. 相似文献
206.
207.
Christopher M. Free Olaf P. Jensen Sherri A. Mason Marcus Eriksen Nicholas J. Williamson Bazartseren Boldgiv 《Marine pollution bulletin》2014
Despite the large and growing literature on microplastics in the ocean, little information exists on microplastics in freshwater systems. This study is the first to evaluate the abundance, distribution, and composition of pelagic microplastic pollution in a large, remote, mountain lake. We quantified pelagic microplastics and shoreline anthropogenic debris in Lake Hovsgol, Mongolia. With an average microplastic density of 20,264 particles km−2, Lake Hovsgol is more heavily polluted with microplastics than the more developed Lakes Huron and Superior in the Laurentian Great Lakes. Fragments and films were the most abundant microplastic types; no plastic microbeads and few pellets were observed. Household plastics dominated the shoreline debris and were comprised largely of plastic bottles, fishing gear, and bags. Microplastic density decreased with distance from the southwestern shore, the most populated and accessible section of the park, and was distributed by the prevailing winds. These results demonstrate that without proper waste management, low-density populations can heavily pollute freshwater systems with consumer plastics. 相似文献