The role of mucus and silk as attachment and sorption sites in streams

This thesis is an examination of the characteristics of mucus and silk within freshwaters. The source of mucus was snail pedal mucus from Lymnaea peregra and Potamopyrgus jenkinsi, the source of silk was first instar silk threads of Simuliidae spp. Each chapter examines a different aspect, or role, of such materials within the habitat of snails and blackfly. In particular, the interactions of suspended particles, pollutants, sediments and biofilms are examined in relation to snail trail mucus (STM) and blackfly silk. The search for a particle type, suitable as a marker for STM is detailed. This was used to characterise STM, including the examination of the duration of STM integrity, the effect of water flow upon STM, the effect of disturbance and bacteria (airborne, waterborne and those included within the mucus trail). The advantage that different substrates offer in maintaining STM presence, as well as the physical dispersal of STM are aspects that are also examined. A comparison is made between the STM of two species of freshwater snail. The examination of the interactions of a range of pesticides to mucus and silk finds sorption to a degree previously unmeasured for any other natural substance. This presents many implications in terms of the bio-accumulation of pollutants within the freshwater ecosystem. The effect that STM has upon benthic sediment stability was found to be immeasurable. In looking at the role of STM in the development of biofilm, it is found that STM can accelerate the accumulation of particulate matter as well as acting as a "seed-bed" for specific types of bacteria. This study provides evidence that organic materials, produced by freshwater macroinvertebrates are an understudied resource that have considerable impact on biological and chemical processes. They exist in considerable quantities and present a large surface area within the freshwater environment. In so doing, they act as a trap or sink for a wide variety of particulate material