Competition between cyanobacteria and green algae affects phytoplankton succession and the well-known cyanobacteria blooms. Climate warming and water acidification are two concerned environmental issues changing the freshwater ecosystems. To investigate the competitive responses of phytoplankton to warming and acidification, we co-cultured Microcystis aeruginosa and Scenedesmus obliquus at a temperature range of 15-35 °C and a pH range of 5-9. Results showed that S. obliquus was superior competitor at 15 °C. At 20-30 °C, the populations of both Scenedesmus and Microcystis were inhibited by the presence of each other. S. obliquus was in competitive domination at the initial phase of cultivation, but was finally replaced by M. aeruginosa. Microcystis kept competition advantage at 35 °C, whereas Scenedesmus outcompeted Microcystis at acidic conditions (pH ≤ 6). Neutral and weakly alkaline conditions (pH 7-9) supported the replacement of competition domination from Scenedesmus to Microcystis. The present study revealed that climate warming may accelerate the phytoplankton succession from green algae to cyanobacteria, with the predicted promoted cyanobacteria blooms. Nonetheless, water acidification causes Microcystis to be a weak competitor with green algae, suggesting that the advantageous effect of Microcystis toward green algae at high temperatures was controlled by other variables like the water pH.

No abstract

Competition amongst different‐sized cladocerans has attracted the interest of many researchers because of their similar life strategies and overlap in feeding habits. To test the combined effects of food concentration and initial relative abundance on the competition outcomes between small‐ and large‐bodied cladocerans, we grew large Daphnia magna and small Moina micrura with two initial relative abundances under five algal densities. At the lowest food concentration (0.10 mg L−1 carbon), D. magna could not maintain a population in the presence or absence of M. micrura. Under conditions in which both species grew together, food levels as high as 0.30 mg L−1 favoured superior population growth of D. magna, irrespective of inoculation abundance. Under conditions in which both species had equal initial abundance, population growth of M. micrura was inhibited by the presence of Daphnia at ≥0.30 mg L−1 food levels. M. micrura was superior to D. magna at higher food concentrations (≥0.60 mg L−1) and high initial abundance. These results suggest that population growth of large Daphnia was more successful than that of small Moina when the food availability was low, while the small Moina dominated under conditions of high initial abundance and high food supply. Therefore, interspecific competition amongst cladocerans depends not only on the size of competing species, but also on their initial relative abundance and food availability.

Herein, a novel kind of composite yarn with alternating segmented structure and interval color has been prepared based on a ring spinning approach. By adjusting the relative motion and blend ratio of the colored polyester filament and natural cotton staple fiber in yarn spinning process, a series of composite yarns were designed and prepared with various segmented structure and cyclical change of the distinct colors. The blend ratio was found to strongly influence on the segment frequency and yarn performance, achieving an improved mechanical property and yarn performance. A color systematic analysis indicated that the combination of alternating structural change induced interval color sense and gradient at the merged regions would lead to an enhanced stereoscopic visual effect of the composite yarns. Moreover, the composite yarns were confirmed to have an excellent weavability and able to endow different patterns and visual effects to the textiles. Thus, considering of the above advantages and multifunctionalities, this work should spur great possibilities for dyeing industry with the promising physical spinning method.

Microcystis blooms are generally associated with zooplankton shifts by disturbing interspecific relationships. The influence of Microcystis on competitive dominance by different sized zooplanktons showed species-specific dependence. We evaluated the competitive responses of small Moina micrura and large Daphnia similoides to the presence of Microcystis using mixed diets comprising 0%, 20%, and 35% of toxic M. aeruginosa, and the rest of green alga Chlorella pyrenoidosa. No competitive exclusion occurred for the two species under the tested diet combinations. In the absence of M. aeruginosa, the biomasses of the two cladocerans were decreased by the competition between them. However, the Daphnia was less inhibited with the higher biomass, suggesting the competitive dominance of Daphnia. M. aeruginosa treatment suppressed the population growths of the two cladocerans, with the reduced carrying capacities. Nonetheless, the population inhibition of Daphnia by competition was alleviated by the increased Microcystis proportion in diet. As a result, the competitive advantage of Daphnia became more pronounced, as indicated by the higher Daphnia: Moina biomass ratio with increased Microcystis proportions. These results suggested that M. aeruginosa strengthens the advantage of D. similoides in competition with M. micrura, which contributes to the diversified zooplankton shifts observed in fields during cyanobacteria blooms.

No abstract