• Alternative methods for assessing habitat quality in freshwater systems

      Sweet, Michael; Ramsey, Andrew; Brys, Rein; Mauvisseau, Quentin (University of DerbyAquatic Research Facility, Environmental Sustainability Research Centre, University of Derby, 2020-06-03)
      “Water, water, everywhere…”. 71% of the earth’s surface is covered by water, freshwater representing 2.5% of it, and only 1% being accessible. Due, largely to a number of anthropogenic activities (pollution, habitats modification) coupled with the impacts of climate change, a dramatic decline in biodiversity is occurring across all earth’s ecosystems. Surprisingly, freshwater ecosystems receive considerably less attention than many other habitats and therefore, effective biodiversity monitoring programs are urgently needed to assess the health and state of the endangered and threatened species in these aquatic systems. Further, current techniques utilised to survey freshwater ecosystems are often considered ineffective, invasive, time consuming and biased. As a result, the implementation of molecular-based detection tools are attractive options as they are often shown to be more sensitive and cost effective. The use of environmental DNA (eDNA) detection is one such molecular tool which is showing promising results, due to its high reliability, sensitivity and non-invasiveness characters. However, recent studies have highlighted potential limitations associated with eDNA-based detection. Such limitations may lead to a decrease in the confidence of this method. The aim of this thesis was to investigate the use of eDNA-based detection across a number of species and a number of systems, all as a proxy of habitat quality. Stringent laboratory practices and validation guidelines were adhered to, allowing for reliable quality assessments of newly designed eDNA assays outlined in this thesis. Moreover, distinct controlled mesocosm experiments allowed the investigation of critical factors, part of the sampling method or analysis processes leading to an optimisation of eDNA collection and decreasing the rates of false negative results. Several comparison between traditional monitoring techniques and the novel assays were also performed aiding in the confidence of these new methods. Interestingly, the results obtained in this thesis shows a similar efficiency between traditional and eDNA-based methods for monitoring invasive species, but a higher efficiency of eDNA detection when detecting rare or low abundant organisms (i.e. those that are endangered or threatened). Furthermore, this thesis reports an extreme example where a species was found at a number of locations within a stretch of a river, yet undetected with the eDNA assay. In this chapter eDNA detection was only possible when I utilised ddPCR rather than qPCR (the more standard technique for assessing eDNA in any given system). Overall, eDNA detection was found to be an effective tool for assessing the presence of invasive and/or endangered species, increasing theknowledge on their distribution and the impact of future management plans. In this thesis, chapters 2, 3, 4, 5 and 6 are organised as case studies, aiming to highlight benefits and limitations of species-specific detection using eDNA.
    • Behavioural and metabolic responses of the freshwater mussels Anodonta anatina and Unio pictorum to environmental stimuli with a focus on food and light availability

      Ramsey, Andrew; Huck, Maren; Mehra, Aradhana; Zapitis, Charitos (University of Derby, 2020-07-05)
      Benthic invertebrates play a crucial role in sediment mixing, nutrient cycling, and oxygen fluxes in benthic ecosystems. Despite the broad global distribution and high abundance of unionid mussels in both lentic and lotic ecosystems, the role of their locomotion behaviour and metabolic activity on the aforementioned processes remain understudied. In this thesis, Anodonta anatina and Unio pictorum were exposed to a range of Chlorella vulgaris concentrations between 0.5 and 20.0 mg Ash Free Dry Mass (AFDM) l-1 at 11.0, 15.0 and 19.0 ± 1.0 °C in laboratory experiments. Unionid behaviours were recorded by time-lapse photography. Mussel locomotion probability and duration, opening behaviour, posterior tip movement and the position in relation to the light source were extracted image and video analysis. The diel rhythm was assessed as well as the responses to the light intensity at ~230, 450 and 1200 lux on a horizontal light gradient. The oxygen consumption (OC) during digestion was quantified at 0.05, 6.0 and 12.0 mg of AFDM of Chlorella vulgaris l-1 at 19.0 ± 1.0 °C. The locomotion probability was significantly higher for A. anatina, compared to U. pictorum, increased with increasing temperature (lower for 11.0 ± 1.0 °C), and decreased with increasing algal concentrations. Locomotion duration decreased with the increasing algal concentration in both species, with U. pictorum showing a shorter locomotion duration than A. anatina. Valve opening peaked at algal concentrations of 3.0 mg l-1. A contrasting locomotion pattern was recorded between the two species with A. anatina crawling on the sediment and U. pictorum breaking through the sediment with is umbo covered. Both species showed a significantly higher probability of locomotion in the absence of light and a decreasing locomotion path distance with the increasing light intensity. The specimens which moved towards the light source covered a longer distance than those which moved away. Additionally, A. anatina showed a net movement towards the light source while all activities were recorded in the absence of light. Digestion significantly contributed to unionid metabolism in both species. In addition, the mean OC rate per dry soft-tissue mass (DM) increased with the algal concentration, with A. anatina showing a significantly higher rate. In A. anatina OC DM-1 decreased with the increasing DM. The findings are discussed in the context of eutrophication, unionid bioremediation potential, and the development of species-specific remediation models. A conceptual model developed demonstrates the ecological interactions between unionids and their environment in lentic systems.