Knee deep in Malacostraca

This week I have been mostly thinking about Malacostraca, specifically Amphipods - "different feet" - referring to the different types of legs they have, some for eating and some for swimming. Amphipods are highly important invertebrates - primary decomposers which carry out the bulk of shredding of vegetation such as dead leaves, speeding up nutrient cycling by other organisms. The most commonly encountered Amphipod is Gammarus pulex/fossarum agg., which is in fact a species complex of many cryptic species distinguishable only by DNA analysis (Continental-scale patterns of hyper-cryptic diversity within the freshwater model taxon Gammarus fossarum (Crustacea, Amphipoda). (2020) Scientific reports, 10(1), 16536). 

I find Gammarus pulex/fossarum agg. pretty much everywhere I look, and around here that means fairly degraded aquatic environments. Urban rivers are some of the most anthropogenically modified landscapes on Earth, resulting in characteristic low diversity communities ("urban stream syndrome"). Several recent projects have aimed to clean up Leicester's watercourses. Although well-meaning these are mostly cosmetic since nothing has been done to reduce harmful inputs, and there has been no real progress in reversing the damaging concrete canalisation of past decades. A few wild flowers and shrubs have been planted and litter, such as the inevitable shopping trolleys, removed. Surprisingly, litter removal in itself might be counter productive. Invertebrates readily colonise artificial surfaces as long as they are non-toxic. An article from Nottingham and Loughborough looked at several urban streams including Saffron Brook and showed that anthropogenic litter in urban rivers supports distinct and diverse macroinvertebrate communities (Anthropogenic litter is a novel habitat for aquatic macroinvertebrates in urban rivers. (2021) Freshwater Biology, 66(3), 524-534). Compared with the harshness of the bare concrete channel, building waste, broken bottles and shopping trolleys are invertebrate paradise. Once again wildlife and the tidy brigade are in conflict.