Stable isotope analysis was used to determine the relative dietary importance of kelp-derived detritus to plankton and benthic organisms along a gradient of kelp abundance driven by recovering sea otter populations al...Stable isotope analysis was used to determine the relative dietary importance of kelp-derived detritus to plankton and benthic organisms along a gradient of kelp abundance driven by recovering sea otter populations along the west coast of Vancouver Island (WCVI), Canada. The study used region-specific kelp isotope values (<i>δ</i><sup>13</sup>C and <i>δ</i><sup>15</sup>N) and season-specific phytoplankton isotope values to model dietary contributions of kelp-derived detritus (KDD). In general, KDD contributions were moderate to high in most plankton size fractions during the summer and decreased during the winter, particularly in the kelp sparse region. Hypothesized regional and spatial (distance from the coast) differences in kelp detritus contributions to zooplankton w<span style="white-space:normal;"><span style="font-family:;" "="">ere</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> not evident. Modeled estimates of the KDD contribution to benthic invertebrates w</span></span><span style="white-space:normal;"><span style="font-family:;" "="">ere</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> high (>40%) and independent of the organism size, among regions and between seasons, with the exception of <i>Astraea gibberosa</i> in the kelp abundant region. Local oceanography, natural kelp isotope signature variation, and significant overlap between kelps’ and blooming phytoplankton isotope values led to a large uncertainty in the assessed KDD contributions in benthic organisms. These results highlighted the importance of the KDD as a widespread and stable year-round food source in coastal kelp populated regions.</span></span>展开更多
Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments;among these, some 25 % are free-living marine forms with a population density of(1–12) 9 106 inds m-2in seabed ...Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments;among these, some 25 % are free-living marine forms with a population density of(1–12) 9 106 inds m-2in seabed sediment, reaching maximum values in muddy estuaries and salt marshes. A large quantity of carbon from the salt marsh plants enters the ecosystem via the detritus pathway,in which nematodes play an important role through their feeding and bioturbation activities. Vegetation influences the sedimentary environment and modifies the distribution pattern of nematode communities in coastal wetlands.Nematodes are coupled closely with bacteria/detritus in microbial food webs, stimulating bacterial growth and subsequent nutrient remineralization; they provide food sources for higher trophic levels and serve as a linkagebetween micro- and macro-fauna. Furthermore, nematodes have a potential to provide proxies that can be used in diagnosing environmental quality. In China, only a limited number of nematode data sets are available for the coastal wetlands across several different climatic zones. It is necessary to carry out additional investigations into the biology and ecology of nematodes in order to delineate their ecological functioning in coastal wetlands. On such a basis,the contribution made by nematodes to material cycling and the ecological functioning in coastal wetlands can be quantified. The assessment of their biological diversity should be a focus, which is fundamental in the study of wetland ecosystem dynamic mechanisms. In addition to laboratory and mesocosm experiments, mathematical models should be established to predict the responses of ecosystem to the environmental disturbance. Finally, it is necessary to improve the techniques for nematode analysis,to enhance the efficiency of data acquisition.展开更多
文摘Stable isotope analysis was used to determine the relative dietary importance of kelp-derived detritus to plankton and benthic organisms along a gradient of kelp abundance driven by recovering sea otter populations along the west coast of Vancouver Island (WCVI), Canada. The study used region-specific kelp isotope values (<i>δ</i><sup>13</sup>C and <i>δ</i><sup>15</sup>N) and season-specific phytoplankton isotope values to model dietary contributions of kelp-derived detritus (KDD). In general, KDD contributions were moderate to high in most plankton size fractions during the summer and decreased during the winter, particularly in the kelp sparse region. Hypothesized regional and spatial (distance from the coast) differences in kelp detritus contributions to zooplankton w<span style="white-space:normal;"><span style="font-family:;" "="">ere</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> not evident. Modeled estimates of the KDD contribution to benthic invertebrates w</span></span><span style="white-space:normal;"><span style="font-family:;" "="">ere</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> high (>40%) and independent of the organism size, among regions and between seasons, with the exception of <i>Astraea gibberosa</i> in the kelp abundant region. Local oceanography, natural kelp isotope signature variation, and significant overlap between kelps’ and blooming phytoplankton isotope values led to a large uncertainty in the assessed KDD contributions in benthic organisms. These results highlighted the importance of the KDD as a widespread and stable year-round food source in coastal kelp populated regions.</span></span>
基金supported by the Mega-Science Program of the Ministry of Science and Technology of China(2013CB956504)the National Natural Science Foundation of China(40906066)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments;among these, some 25 % are free-living marine forms with a population density of(1–12) 9 106 inds m-2in seabed sediment, reaching maximum values in muddy estuaries and salt marshes. A large quantity of carbon from the salt marsh plants enters the ecosystem via the detritus pathway,in which nematodes play an important role through their feeding and bioturbation activities. Vegetation influences the sedimentary environment and modifies the distribution pattern of nematode communities in coastal wetlands.Nematodes are coupled closely with bacteria/detritus in microbial food webs, stimulating bacterial growth and subsequent nutrient remineralization; they provide food sources for higher trophic levels and serve as a linkagebetween micro- and macro-fauna. Furthermore, nematodes have a potential to provide proxies that can be used in diagnosing environmental quality. In China, only a limited number of nematode data sets are available for the coastal wetlands across several different climatic zones. It is necessary to carry out additional investigations into the biology and ecology of nematodes in order to delineate their ecological functioning in coastal wetlands. On such a basis,the contribution made by nematodes to material cycling and the ecological functioning in coastal wetlands can be quantified. The assessment of their biological diversity should be a focus, which is fundamental in the study of wetland ecosystem dynamic mechanisms. In addition to laboratory and mesocosm experiments, mathematical models should be established to predict the responses of ecosystem to the environmental disturbance. Finally, it is necessary to improve the techniques for nematode analysis,to enhance the efficiency of data acquisition.
