In this paper, the dynamics of a delayed phytoplankton-zooplankton model is considered. Taking the delay due to the gestation of zooplankton as param- eter, we describe the local Hopf bifurcation by center manifold th...In this paper, the dynamics of a delayed phytoplankton-zooplankton model is considered. Taking the delay due to the gestation of zooplankton as param- eter, we describe the local Hopf bifurcation by center manifold theorem and normal form, then we discuss the global existence of periodic solution. At last, some simulations are given to support our result.展开更多
The aim of this study of the Manantali dam reservoir is to investigate the biological quality of the water through inventories and analysis of the ichthyofauna and planktonic communities (zooplankton and phytoplankton...The aim of this study of the Manantali dam reservoir is to investigate the biological quality of the water through inventories and analysis of the ichthyofauna and planktonic communities (zooplankton and phytoplankton). Inventories of ichthyofauna and plankton communities were carried out quarterly from 2003 to 2022. The fish populations studied on the basis of bioindicators (species richness, diversity index, equitability index, diversification index) identified 29 species belonging to 10 families. The Cichlidae family is the most represented, while the Schilbeidae and Tetraodontioae families are less represented in terms of number of species. The species Hydrocynus forskalii and Brycinus nurse with relative abundances of 40.12% and 21.4% respectively, both from the family Alestidae, are the most abundant. The species H. forskalii has a frequency of occurrence of 100%. The specific diversity index of 2.9 and the equitability index of 0.6 show an average diversity of fish species. The diversification index of 2.9 indicates a theoretical number of habitats of 2 to 3. The planktonic community is made up of zooplankton and phytoplankton. The inventory of zooplankton shows the presence of 28 zooplankton species belonging to 9 families of the three zooplankton groups Rotifera, Cladocera and Copepoda. Analysis of the frequencies of occurrence of the various taxa showed that the characteristic species of Lake Manantali are the omnipresent rotifers Keratella cochlearis, Keratella quadrata and Trichocerca chattoni. For phytoplankton, the inventories carried out show the presence of 65 species belonging to 5 families (Chlorophycees, Diatomees, Dinophycees, Chrysophycees and Cyanophycees). An analysis of the frequency of occurrence of the various taxa shows that the characteristic species of Lake Manantali are Chlorophycees, with 7 species: Desmidium baileyi, Micrasterias alata, Sphaerocystis schroeteri, Spondylosium sp., Staurastrum heimii, Staurastrum subanchora, Staurodesmus wandae;Diatoms, with one species: Navicula sp. and Cyanophycees, with one species: Microcystis aeruginosa.展开更多
Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our ...Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our work in 2019 concerning the ecotoxicological effects of such formulations on corals (Seriatopora hystrix), we here provide some new information about the biodegradability and the ecotoxicological effects of these products on marine zoo- and phytoplankton. Therefore, we choose to realize in silico and in vitro studies of the biodegradability of several solar products but also to evaluate the ecotoxicological effects of these products on one phytoplankton, i.e. Phaeodactylum tricornutum, and one zooplankton, i.e. Acartia tonsa, of a great importance for sea species survival (notably as sources of food). Materials and methods: Two different approaches were used to study the biodegradability of the tested products: One in silico method and an in vitro one. 2 solar products were involved in the in silico study which consisted in the determination of the degradation factor (DF) of each ingredient of the tested formulas in order to finally obtain their estimated biodegradability percentage. Already available data concerning each ingredient coupled to a computer model developed with one of our partners were used to achieve this study. The in vitro study involved 8 formulas containing UV-filters and was led by following the OECD 301 F guidelines. Ecotoxicological studies of 7 of the formulas containing UV-filters were for their part realized by following the ISO 10253 guidelines for the experiments led with Phaeodactylum tricornutum, and the ISO 14669 guidelines for the experiments led with Acartia tonsa. In these studies, the effect of each tested product on crustaceans’ mortality and algal growth inhibition was assessed. Results: The in silico study predicted that formulas containing chemical UV-filters display a high biodegradability (superior to the threshold value of 60% given by the OECD 301 F guidelines). In the in vitro part of our work, the 8 tested formulas showed a biodegradability slightly inferior to the one predicted in the in silico experiments. Therefore, in order to evaluate if these calculated biodegradability value could have significant harmful effects on zoo- or phytoplankton, we studied the effect of our products regarding the growth inhibition on Phaeodactylum tricornutum and the mortality on Acartia tonsa. In this last part of the study, all the tested products were classified as “non ecotoxic” following an internal classification based on Part 4 entitled “Environmental Hazards” of Globally Harmonized System of Classification and Labelling of Chemicals (GHS), 9<sup>th</sup> edition (2021). Conclusions: These results are notably in line with those published by our teams in 2019 on the effects of solar cosmetic products on corals and seem to confirm that formulas containing mineral and chemical UV-filters can be daily used without displaying significant noxious effects on marine fauna and flora. .展开更多
基金supported by the National Natural Science Foundations of China(No.11431008)NSF of Shanghai grant(No.15ZR1423700)
文摘In this paper, the dynamics of a delayed phytoplankton-zooplankton model is considered. Taking the delay due to the gestation of zooplankton as param- eter, we describe the local Hopf bifurcation by center manifold theorem and normal form, then we discuss the global existence of periodic solution. At last, some simulations are given to support our result.
文摘The aim of this study of the Manantali dam reservoir is to investigate the biological quality of the water through inventories and analysis of the ichthyofauna and planktonic communities (zooplankton and phytoplankton). Inventories of ichthyofauna and plankton communities were carried out quarterly from 2003 to 2022. The fish populations studied on the basis of bioindicators (species richness, diversity index, equitability index, diversification index) identified 29 species belonging to 10 families. The Cichlidae family is the most represented, while the Schilbeidae and Tetraodontioae families are less represented in terms of number of species. The species Hydrocynus forskalii and Brycinus nurse with relative abundances of 40.12% and 21.4% respectively, both from the family Alestidae, are the most abundant. The species H. forskalii has a frequency of occurrence of 100%. The specific diversity index of 2.9 and the equitability index of 0.6 show an average diversity of fish species. The diversification index of 2.9 indicates a theoretical number of habitats of 2 to 3. The planktonic community is made up of zooplankton and phytoplankton. The inventory of zooplankton shows the presence of 28 zooplankton species belonging to 9 families of the three zooplankton groups Rotifera, Cladocera and Copepoda. Analysis of the frequencies of occurrence of the various taxa showed that the characteristic species of Lake Manantali are the omnipresent rotifers Keratella cochlearis, Keratella quadrata and Trichocerca chattoni. For phytoplankton, the inventories carried out show the presence of 65 species belonging to 5 families (Chlorophycees, Diatomees, Dinophycees, Chrysophycees and Cyanophycees). An analysis of the frequency of occurrence of the various taxa shows that the characteristic species of Lake Manantali are Chlorophycees, with 7 species: Desmidium baileyi, Micrasterias alata, Sphaerocystis schroeteri, Spondylosium sp., Staurastrum heimii, Staurastrum subanchora, Staurodesmus wandae;Diatoms, with one species: Navicula sp. and Cyanophycees, with one species: Microcystis aeruginosa.
文摘Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our work in 2019 concerning the ecotoxicological effects of such formulations on corals (Seriatopora hystrix), we here provide some new information about the biodegradability and the ecotoxicological effects of these products on marine zoo- and phytoplankton. Therefore, we choose to realize in silico and in vitro studies of the biodegradability of several solar products but also to evaluate the ecotoxicological effects of these products on one phytoplankton, i.e. Phaeodactylum tricornutum, and one zooplankton, i.e. Acartia tonsa, of a great importance for sea species survival (notably as sources of food). Materials and methods: Two different approaches were used to study the biodegradability of the tested products: One in silico method and an in vitro one. 2 solar products were involved in the in silico study which consisted in the determination of the degradation factor (DF) of each ingredient of the tested formulas in order to finally obtain their estimated biodegradability percentage. Already available data concerning each ingredient coupled to a computer model developed with one of our partners were used to achieve this study. The in vitro study involved 8 formulas containing UV-filters and was led by following the OECD 301 F guidelines. Ecotoxicological studies of 7 of the formulas containing UV-filters were for their part realized by following the ISO 10253 guidelines for the experiments led with Phaeodactylum tricornutum, and the ISO 14669 guidelines for the experiments led with Acartia tonsa. In these studies, the effect of each tested product on crustaceans’ mortality and algal growth inhibition was assessed. Results: The in silico study predicted that formulas containing chemical UV-filters display a high biodegradability (superior to the threshold value of 60% given by the OECD 301 F guidelines). In the in vitro part of our work, the 8 tested formulas showed a biodegradability slightly inferior to the one predicted in the in silico experiments. Therefore, in order to evaluate if these calculated biodegradability value could have significant harmful effects on zoo- or phytoplankton, we studied the effect of our products regarding the growth inhibition on Phaeodactylum tricornutum and the mortality on Acartia tonsa. In this last part of the study, all the tested products were classified as “non ecotoxic” following an internal classification based on Part 4 entitled “Environmental Hazards” of Globally Harmonized System of Classification and Labelling of Chemicals (GHS), 9<sup>th</sup> edition (2021). Conclusions: These results are notably in line with those published by our teams in 2019 on the effects of solar cosmetic products on corals and seem to confirm that formulas containing mineral and chemical UV-filters can be daily used without displaying significant noxious effects on marine fauna and flora. .
