Mangrove forests are unique habitats in their function as potential food source and nurseries, and support an important fisheries resource. In the Benin coastal zone, the mangrove fishes have been surveyed to investig...Mangrove forests are unique habitats in their function as potential food source and nurseries, and support an important fisheries resource. In the Benin coastal zone, the mangrove fishes have been surveyed to investigate fish species diversity, community structures and ecosystem degradation impacts in order to protect and to improve the mangrove fish resources. Results from wet, high-water and dry season samplings revealed that the two dominant mangrove species, Rizophora racemosa and Avicennia africana, are being intensively degraded for domestic use such as firewood and house building. Fifty one (51) fish species belonging to 25 families were recorded with Eleotridae (7 species), Cichlidae (5 species), and Mugilidae (5 species), the most speciose families. Dominant trophic guilds were detritivores (54.57%) and planktinovores/microcarnivores (30.41%). Six (6) species, Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Hemichromis fasciatus, Ethmalosa fimbriata, and Aplocheilichthys spilauchen, dominated the samples and accounted for about 80.27%. Sarotherodon melanotheron constituted the major dominant species and accounted numerically for about 29% of the total catches and 46.7% of the total biomass. The Margalef index of species richness ranged between 2.42 and 4.43, the Shannon-Weaver index of species diversity between 1.39 and 2.27, and the evenness between 0.50 and 0.62. Lower indices were observed for the highly degraded and the moderately degraded sites whereas higher indices were recorded for the less degraded and the restored sites. Species richness, species diversity and dominant species abundance were positively correlated with depth and transparency and negatively correlated with temperature. Multi-species fisheries dominate the coastal zone with Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Ethmalosa fimbriata, Liza falcipinus, Mugil sp. and Chrysichthys nigrodigitatus, the major species in the commercial catches. In addition to the mangrove destruction, the hydro electrical dam have greatly modified the Mono River flooding regime, water quality and the fish composition of the Benin coastal lagoon system. An integrated approach of the mangrove resource management/conservation, including intensive mangrove restoration, management of key fish species, freshwater prawns (Macrobrachiun sp.), peneids shrimps, mangrove oysters (Crassostrea sp.), and crabs (Callinectes sp., Cardiosoma sp.), and habitat protection is required for ecosystem recovery and sustainable exploitation.展开更多
Environmental contamination with metals such as manganese （Mn） and nickel （Ni） often results in elevated concentrations of these metals in plant tissues. At high concentrations, these metals are known to have detr...Environmental contamination with metals such as manganese （Mn） and nickel （Ni） often results in elevated concentrations of these metals in plant tissues. At high concentrations, these metals are known to have detrimental effects on certain insect herbivores. Using laboratory bioassays and artificial diet, we investigated the development and survival of a cosmopolitan insect detritivore, Megaselia scalaris （Diptera： Phoridae）, exposed to concentrations of Mn and Ni reaching 2 600 mg Mn/kg and 5 200 mg Ni/kg dry mass （dm） in artificial diet. Surprisingly, Ni and Mn at the concentrations tested did not harm this fly. Treatment groups from diets with 260-2 600 mg Mn/kg dm and 1 300-5 200 mg Ni/kg dm had significantly shorter larval development times, overall times to adult emergence, and both pupariation and pupal eclosion times compared to a control group. Wing length of females, a correlate of adult fitness, was also greater in metal treatment groups. Other measures including rate of egg hatch, percentage of emerging flies that were female, and wing length of male flies, were not significantly different in metal treatment groups. We conclude that Megaselia scalaris is tolerant of exceptionally high levels of Mn and Ni.展开更多
The extensive land use conversion expected to occur to meet demands for bioenergy feedstock production will likely have widespread impacts on agroecosystem biodiversity and ecosystem services, including carbon sequest...The extensive land use conversion expected to occur to meet demands for bioenergy feedstock production will likely have widespread impacts on agroecosystem biodiversity and ecosystem services, including carbon sequestration. Although arthropod detritivores are known to contribute to litter decomposition and thus energy flow and nutrient cycling in many plant communities, their importance in bioenergy feedstock communities has not yet been assessed. We undertook an experimental study quantifying rates of litter mass loss and nutrient cycling in the presence and absence of these organisms in three bioenergy feedstock crops—miscanthus （Miscanthus x giganteus）, switchgrass （Panicum virgatum）, and a planted prairie community. Overall arthropod abundance and litter decomposition rates were similar in all three communities. Despite effective reduction of arthropods in experimental plots via insecticide application, litter decomposition rates, inorganic nitrogen leaching, and carbon–nitrogen ratios did not differ significantly between control （with arthropods） and treatment （without arthropods） plots in any of the three community types. Our findings suggest that changes in arthropod faunal composition associated with widespread adoption of bioenergy feedstock crops may not be associated with profoundly altered arthropod-mediated litter decomposition and nutrient release.展开更多
Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative.This study examined the possible interspecific interactions...Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative.This study examined the possible interspecific interactions between a dung-tunneling beetle species(Onthophagus yubarinus)and an earthworm species(Aporrectodea noctuma),two major detritivores responsible for dung removal in a Tibetan alpine meadow.We conducted a two-way,factorial field experiment using replicated chambers,and measured the performances of beetles and earthworms,as well as yak dung removal,soil properties and aboveground plant biomass over two months.Earthworm presence significantly decreased the body size of beetle larvae and the weight of tunnel dung that beetle larvae live on.In contrast,beetle presence did not affect the performance of earthworms.Beetles,earthworms and their interaction significantly increased dung removal and soil organic carbon concentration at the end of the experiment.Beetles alone significantly increased soil total N and P,soluble N and P concentrations,but earthworms alone had nonsignificant effects on these nutrient variables.Beetles and earthworms additively enhanced soluble N and P concentrations,and aboveground plant biomass at the end of the experiment.These results indicate 1)there was a one-sided negative relationship between dung-tunneling beetles and earthworms,resulting from the consumption of earthworms on food resource of beetle larvae;and 2)the coexistence of beetles and earthworms facilitated dung removal interactively and plant growth additively by increasing nutrient availability.展开更多
文摘Mangrove forests are unique habitats in their function as potential food source and nurseries, and support an important fisheries resource. In the Benin coastal zone, the mangrove fishes have been surveyed to investigate fish species diversity, community structures and ecosystem degradation impacts in order to protect and to improve the mangrove fish resources. Results from wet, high-water and dry season samplings revealed that the two dominant mangrove species, Rizophora racemosa and Avicennia africana, are being intensively degraded for domestic use such as firewood and house building. Fifty one (51) fish species belonging to 25 families were recorded with Eleotridae (7 species), Cichlidae (5 species), and Mugilidae (5 species), the most speciose families. Dominant trophic guilds were detritivores (54.57%) and planktinovores/microcarnivores (30.41%). Six (6) species, Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Hemichromis fasciatus, Ethmalosa fimbriata, and Aplocheilichthys spilauchen, dominated the samples and accounted for about 80.27%. Sarotherodon melanotheron constituted the major dominant species and accounted numerically for about 29% of the total catches and 46.7% of the total biomass. The Margalef index of species richness ranged between 2.42 and 4.43, the Shannon-Weaver index of species diversity between 1.39 and 2.27, and the evenness between 0.50 and 0.62. Lower indices were observed for the highly degraded and the moderately degraded sites whereas higher indices were recorded for the less degraded and the restored sites. Species richness, species diversity and dominant species abundance were positively correlated with depth and transparency and negatively correlated with temperature. Multi-species fisheries dominate the coastal zone with Sarotherodon melanotheron, Dormitator lebretonis, Gerres melanopterus, Ethmalosa fimbriata, Liza falcipinus, Mugil sp. and Chrysichthys nigrodigitatus, the major species in the commercial catches. In addition to the mangrove destruction, the hydro electrical dam have greatly modified the Mono River flooding regime, water quality and the fish composition of the Benin coastal lagoon system. An integrated approach of the mangrove resource management/conservation, including intensive mangrove restoration, management of key fish species, freshwater prawns (Macrobrachiun sp.), peneids shrimps, mangrove oysters (Crassostrea sp.), and crabs (Callinectes sp., Cardiosoma sp.), and habitat protection is required for ecosystem recovery and sustainable exploitation.
文摘Environmental contamination with metals such as manganese （Mn） and nickel （Ni） often results in elevated concentrations of these metals in plant tissues. At high concentrations, these metals are known to have detrimental effects on certain insect herbivores. Using laboratory bioassays and artificial diet, we investigated the development and survival of a cosmopolitan insect detritivore, Megaselia scalaris （Diptera： Phoridae）, exposed to concentrations of Mn and Ni reaching 2 600 mg Mn/kg and 5 200 mg Ni/kg dry mass （dm） in artificial diet. Surprisingly, Ni and Mn at the concentrations tested did not harm this fly. Treatment groups from diets with 260-2 600 mg Mn/kg dm and 1 300-5 200 mg Ni/kg dm had significantly shorter larval development times, overall times to adult emergence, and both pupariation and pupal eclosion times compared to a control group. Wing length of females, a correlate of adult fitness, was also greater in metal treatment groups. Other measures including rate of egg hatch, percentage of emerging flies that were female, and wing length of male flies, were not significantly different in metal treatment groups. We conclude that Megaselia scalaris is tolerant of exceptionally high levels of Mn and Ni.
文摘The extensive land use conversion expected to occur to meet demands for bioenergy feedstock production will likely have widespread impacts on agroecosystem biodiversity and ecosystem services, including carbon sequestration. Although arthropod detritivores are known to contribute to litter decomposition and thus energy flow and nutrient cycling in many plant communities, their importance in bioenergy feedstock communities has not yet been assessed. We undertook an experimental study quantifying rates of litter mass loss and nutrient cycling in the presence and absence of these organisms in three bioenergy feedstock crops—miscanthus （Miscanthus x giganteus）, switchgrass （Panicum virgatum）, and a planted prairie community. Overall arthropod abundance and litter decomposition rates were similar in all three communities. Despite effective reduction of arthropods in experimental plots via insecticide application, litter decomposition rates, inorganic nitrogen leaching, and carbon–nitrogen ratios did not differ significantly between control （with arthropods） and treatment （without arthropods） plots in any of the three community types. Our findings suggest that changes in arthropod faunal composition associated with widespread adoption of bioenergy feedstock crops may not be associated with profoundly altered arthropod-mediated litter decomposition and nutrient release.
基金the National Natural Science Foundation of China(31971442 and 31530007).
文摘Interspecific interactions between two spatiotemporally co-occurred species sharing a single resource are considered to be either competitive or facilitative.This study examined the possible interspecific interactions between a dung-tunneling beetle species(Onthophagus yubarinus)and an earthworm species(Aporrectodea noctuma),two major detritivores responsible for dung removal in a Tibetan alpine meadow.We conducted a two-way,factorial field experiment using replicated chambers,and measured the performances of beetles and earthworms,as well as yak dung removal,soil properties and aboveground plant biomass over two months.Earthworm presence significantly decreased the body size of beetle larvae and the weight of tunnel dung that beetle larvae live on.In contrast,beetle presence did not affect the performance of earthworms.Beetles,earthworms and their interaction significantly increased dung removal and soil organic carbon concentration at the end of the experiment.Beetles alone significantly increased soil total N and P,soluble N and P concentrations,but earthworms alone had nonsignificant effects on these nutrient variables.Beetles and earthworms additively enhanced soluble N and P concentrations,and aboveground plant biomass at the end of the experiment.These results indicate 1)there was a one-sided negative relationship between dung-tunneling beetles and earthworms,resulting from the consumption of earthworms on food resource of beetle larvae;and 2)the coexistence of beetles and earthworms facilitated dung removal interactively and plant growth additively by increasing nutrient availability.
