Cotton-strip assays: Let's move on to eco-friendly biomonitoring!

There is increasing recognition that functional bioindicators are needed for ecosystem health assessments. In this perspective, cotton strip assays are widely considered as a standard method to account for organic matter decomposition in streams. However, cotton cultivation and manufacture raise both environmental and societal dramatic issues that are - in our opinion - irreconcilable with the objectives of bioindication. In this study, we assessed the relevance of four alternative - eco-friendly - textiles (made of organic cotton, hemp and linen) by comparing their chemical composition and degradation rates in six streams. Chemical composition exhibited low variations among textiles, but contrasted sharply with the expectation that cotton is mostly composed of cellulose. Moreover, surprisingly high nutrient (0.49% N) contents occurred in the conventional cotton strips compared with the organic textiles (N < 0.12%). All textiles provided similar degradation rates across the six streams, meaning that they could be interchangeably used as alternatives to conventional cotton strips. We thus call for the adoption of such ethical and eco-friendly tools as 'next-generation' indicators for the functioning of stream ecosystem.