Bivalve molluscs as environmental monitors and tools for sustainable water management

Abstract

Freshwater environments are capable of providing a wide range of vital ecosystem services, from basic provision of drinking water to energy production, waste removal to recreation. Well-managed water resources allow such precious services to be preserved. However, anthropogenic influences have led to the widespread degradation of freshwater environments, resulting in extensive decline in freshwater organisms. With growing pressures on water resources, there is an increasing need for change: sustainable water management regimes are needed, to allow the water requirements of society to be met as far as is feasible both at the current time, and in the future. The improvement of monitoring capacity affords an effective tool for the protection and conservation of waterways, which represent key components of sustainable water management strategies. In situ physical and chemical sensing has allowed improved temporal and spatial resolution of water monitoring, yet the information they provide is limited, and key ecological information is lacking. This has encouraged the use of aquatic biota to provide direct information on the ecological state of a waterway. Such monitoring is beneficial, both to the protection of the health of aquatic ecosystems, and the human populations that rely upon them. Bivalve molluscs offer particular promise for the biomonitoring of aquatic systems. This thesis seeks to progress understanding and enable wider study of prominent means by which bivalves can, or may yet, provide insights into their environments. Production of a review explained the key behaviours of bivalves used in biosensing of water quality, and suggested means to enhance the informativeness of systems employing them, as well as other potential behaviours that could be valuable in biosensing, and future directions. Subsequently, a novel system was developed, demonstrating how the key behaviours used in biosensing, valve movements and cardiac activity, may both be simultaneously measured. With extensive detail and explanation of a sophisticated yet simple, inexpensive, scalable and adaptable set-up, this work encourages and facilitates the widespread implementation of bivalve-based monitoring. The system was then demonstrated in experimental work through simple testing of stressor responses with specimens of Duck Mussel (Anodonta anatina), which highlighted the potential benefits of integration of behaviours (a key suggestion of the review), and helped address practical concerns regarding their simultaneous use. Within the review, vertical and horizontal movements of mobile bivalve species were suggested as an alternative biosensing behaviour. Harnessing advances in artificial intelligence, a proof-of-concept system was therefore developed for tracking these movements in specimens of Painter’s Mussel (Unio pictorum) and Duck Mussel, in an entirely natural mode of life, and their responses to different stressors were tested. There was high variability between individual mussels, which indicated that future approaches using artificial intelligence to monitor movements should control for individual variation by monitoring deviations from baselines. The viability of the approach is proven and should prompt further study. Finally, examination of external and (novel) internal anatomical features across very small distances in space (microhabitats), revealed significant morphological responses in specimens of the Swollen River Mussel (Unio tumidus), highlighting the sensitivity of morphology to intricacies of a bivalve’s environment. The knowledge gained in the current work expands understanding of the various ways by which bivalve molluscs can provide tools for monitoring the environment and, through prototype and proof-of-concept studies, helps to demonstrate and encourage more widespread implementation of study. While providing further water monitoring tools, this work enables a greater understanding of bivalve ecology; this is valuable for informing their conservation. Furthermore, freshwater mussels are prominent ecosystem engineers and shape the aquatic community around them. Hence, their conservation facilitates the conservation of the whole freshwater ecosystem. Therefore, the work here demonstrates that bivalves are effective tools in sustainable water management strategies, through enabling protection of freshwater resources, and aiding their conservation.