Protocol development towards using benthic diatom endpoints to determine freshwater ecosystem function and health: Assessing the impact of the environment on the colonisation of substratum by benthic diatoms

Benthic diatom communities have been used for decades in the assessment of the health of freshwater environments. To this end, several benthic diatom metrics have been used to measure the effects of nutrient enrichment, acidification, and organic chemical contamination at the community level. Organic chemicals present in Home and personal care products (HPCPs) have a wide range of functions within household cleaning and personal hygiene products. Despite their prevalence, there is limited research on many of these chemicals, compared to other groups of organic chemicals, such as herbicides or pesticides, which unlike most HPCPs are biologically active. In this thesis, development of a protocol for using benthic diatom community endpoints to determine the effects of organic chemicals on freshwater ecosystem health and function was conducted. The results presented here indicate that microscope slides, ceramic tiles or sandstone substratum could be reasonably used for culturing benthic diatom communities without having a significant effect on the communities that are developed, but ceramic tiles are slightly better at mimicking more developed communities within four weeks. A laboratory-based batch culturing method using communities grown directly from lake water was shown to be capable of developing functioning diatom communities, although longer periods of culturing will likely be required, as these cultures exhibited far lower biomass measurements than field equivalents, and a customized nutrient replacement regime developed using pre-culture tests to determine the usage rate of nutrients within the cultures are recommended. Diatom communities from sites in good ecological quality in the Vale of York were also assessed, and several species of sensitive and tolerant diatoms were identified for a representative community to be cultured using the methodology developed here. Further research studying these sites, and a broader range of others in the region at different times of the growing season are recommended.