Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa.
Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa.
Sci Total Environ. 2022 Sep 15;839:156320. doi: 10.1016/j.scitotenv.2022.156320. Epub 2022 May 29.
Global contamination of freshwater ecosystems by chemical compounds, such as pesticides, may exert high pressure on biologically-driven organic matter decomposition. These pollutants may also impair the quality of organic substrates for colonising invertebrates and reduce primary productivity by decreasing the abundance of phytoplankton. In southern Africa, increasing pesticide usage associated with macadamia plantations, in particular, presents a growing risk to freshwater ecosystems. Here, we examined macadamia (Macadamia integrifolia) leaf litter decomposition following exposure to three pesticides (i.e., Karate Zeon 10 CS (lambda-cyhalothrin), Mulan 20 AS (acetamiprid), Pyrinex 250 CS (chlorpyrifos)) used commonly in macadamia plantations, via an ex-situ microcosm approach. We examined mosquito colonisation of these microcosms as semi-aquatic macroinvertebrates which form a significant component of aquatic communities within standing waters. Macadamia leaf litter tended to decompose faster when exposed to Karate and Pyrinex pesticide treatments. Additionally, chlorophyll-a, conductivity, total dissolved solids, and pH differed among pesticide treatments and controls, with pesticides (Karate Zeon and Mulan) tending to reduce chlorophyll-a concentrations. Overall, pesticide treatments promoted mosquito (i.e., Culex spp.) and pupal abundances. In terms of dominant aquatic mosquito group abundances (i.e., Anopheles spp., Culex spp.), the effect of pesticides differed significantly among pesticide types, with Pyrinex and Mulan treatments having higher mosquito abundances in comparison to Karate Zeon and pesticide-free treatments. These findings collectively demonstrate that common pesticides used in the macadamia plantation may exert pressure on adjacent freshwater communities by shaping leaf-litter decomposition, semi-aquatic macroinvertebrate colonisation dynamics, and chlorophyll-a.
全球范围内，化学化合物（如农药）对淡水生态系统的污染可能对生物驱动的有机物质分解造成巨大压力。这些污染物还可能通过减少浮游植物的丰度来损害为无脊椎动物定殖的有机基质的质量，并降低初级生产力。在南非，与澳洲坚果种植园相关的农药使用量不断增加，对淡水生态系统构成了越来越大的威胁。在这里，我们通过一种离体微宇宙方法，研究了三种常用于澳洲坚果种植园的农药（即百树得 10CS（高效氯氟氰菊酯）、亩旺特 20AS（噻虫嗪）、毒死蜱 250CS）暴露后对澳洲坚果（Macadamia integrifolia）叶凋落物分解的影响。我们研究了这些微宇宙中蚊子的定殖情况，因为蚊子是静水水生社区中重要的半水生大型无脊椎动物组成部分。当暴露于百树得和毒死蜱农药处理时，澳洲坚果叶凋落物的分解速度往往更快。此外，叶绿素-a、电导率、总溶解固体和 pH 值在农药处理和对照之间存在差异，其中农药（百树得和亩旺特）往往会降低叶绿素-a 的浓度。总的来说，农药处理促进了蚊子（即库蚊属和伊蚊属）和蛹的丰度。就主要水生蚊子群体（即按蚊属和库蚊属）的丰度而言，不同农药类型之间的农药效应有显著差异，与百树得和无农药处理相比，吡虫啉和亩旺特处理的蚊子丰度更高。这些发现共同表明，在澳洲坚果种植园中使用的常见农药可能通过塑造凋落物分解、半水生大型无脊椎动物定殖动态和叶绿素-a 对相邻淡水社区施加压力。
