Pacheco Juan Pablo, Calvo Clementina, Aznarez Celina, Barrios Margenny, Meerhoff Mariana, Jeppesen Erik, Baattrup-Pedersen Annette
Department of Bioscience, Aarhus University, Silkeborg 8600, Denmark; Sino-Danish Centre for Education and Research (SDC), Beijing 100049, China; University of Chinese Academy of Sciences, Beijing 100049, China; Centro Universitario Regional del Este - Universidad de la República, Maldonado 20000, Uruguay.
Centro Universitario Regional del Este - Universidad de la República, Maldonado 20000, Uruguay.
Sci Total Environ. 2022 Feb 1;806(Pt 1):150505. doi: 10.1016/j.scitotenv.2021.150505. Epub 2021 Sep 23.
Climate-induced changes in precipitation and land-use intensification affect the discharge of streams worldwide, which, together with eutrophication and loss of riparian canopy, can affect periphyton biomass and composition, and therefore, ultimately the stream functioning. We investigated the responses of periphyton biomass and life-forms (i.e., high profile, low profile and motile) to these changes applying an experimental approach by modulating nutrients (nutrient diffusion substrates enriched with 0.5 M NHNO + 0.031 M KHPO and without nutrient enrichment) and light availability (50% shade and full light) along a gradient in discharge ranging from 0.46 to 3.89 L/s (0.7 to 6.5 cm/s) in twelve large-sized (12- m long) outdoor flumes resembling lowland streams. We also analysed the potential effects of other environmental variables including macroinvertebrates on the responses of periphyton to discharge, nutrients, and light. Light and nutrient availability drastically affected periphyton biomass and composition responses to discharge. Periphyton biomass decreased with increasing discharge when shaded but this did not happen when exposed to full light. Under full light conditions, nutrient enrichment mediated an increase in the periphyton biomass with increasing discharge, possibly reflecting an increased metabolism, but this did not happen under non-enriched conditions. Enrichment further affected the compositional responses of periphyton to discharge, with an increase in the biomass of motile, fast-growing, small-sized flagellated at low discharge conditions, and mitigating a loss of high profile periphyton under higher discharges. Light did not affect periphyton composition, and the abundance or feeding-group composition of the macroinvertebrates did not affect biomass or composition of the periphyton either. Our results suggest that nutrient enrichment and light play an important synergistic role in the responses of the periphyton biomass and composition to discharge and emphasize the relevance of riparian canopy conservation and eutrophication control to avoid periphyton growth under increased discharge scenarios in small lowland streams.
气候引起的降水变化和土地利用集约化影响着全球河流的流量，这与富营养化和河岸树冠层的丧失一起，会影响周丛生物的生物量和组成，进而最终影响河流功能。我们采用实验方法，通过在十二个类似低地溪流的大型（12米长）室外水槽中，沿着0.46至3.89升/秒（0.7至6.5厘米/秒）的流量梯度调节养分（富含0.5M硝酸铵+0.031M磷酸二氢钾的养分扩散基质和无养分富集）和光照条件（50%遮荫和全光照），研究了周丛生物的生物量和生活型（即高型、低型和运动型）对这些变化的响应。我们还分析了包括大型无脊椎动物在内的其他环境变量对周丛生物对流量、养分和光照响应的潜在影响。光照和养分有效性极大地影响了周丛生物量和组成对流量的响应。遮荫时，周丛生物量随流量增加而减少，但在全光照条件下则不会。在全光照条件下，养分富集导致周丛生物量随流量增加而增加，这可能反映了新陈代谢的增强，但在无养分富集条件下则不会。富集进一步影响了周丛生物对流量的组成响应，在低流量条件下，运动型、快速生长的小型鞭毛藻生物量增加，减轻了高型周丛生物在较高流量下的损失情况。光照不影响周丛生物组成，大型无脊椎动物的丰度或摄食组组成也不影响周丛生物的生物量或组成。我们的研究结果表明，养分富集和光照在周丛生物量和组成对流量的响应中发挥着重要的协同作用，并强调了保护河岸树冠层和控制富营养化对于避免小型低地溪流在流量增加情况下周丛生物生长的重要性。
