A novel, inexpensive, and adaptable system for the simultaneous measurement of valve movements and cardiac activity in bivalves

Guarding aquatic resources from degradation is vital. Organismal behavioural biomonitoring enables facile broad-spectrum toxicity detection, with distinct strengths over traditional water-quality sensing. Bivalve molluscs make ideal biomonitors, using alterations within two behaviours, valve movements and cardiac activity. Commercial systems monitoring these are costly, and often inflexible, whilst published methods typically lack broad suitability or requisite detail, or necessitate expertise; widespread application can be hindered, especially in the Global South and remote locations, despite the benefits for water monitoring. Furthermore, integration of both behaviours in systems is uncommon, despite probable gains in informativeness and sensitivity. Therefore, in the current work, a novel prototype set-up to simultaneously monitor valve movements and cardiac activity in multiple specimens was designed, constructed, and demonstrated. Employing popular, sophisticated, and robust technological approaches, the system caters for many bivalves (sessile/mobile, freshwater/marine). Reproducible, inexpensive, and uncomplicated, the low-power system centres around a Raspberry Pi (3B+) microcontroller, compatible with manifold open-source software. Monitoring eight unfixed animals for approximately £200 (during 2020), the system is adaptable for specimen numbers, type/rate of data capture, and operational conditions/environment. It is also scalable; miniaturisation and economies of scale should reduce the size and cost of a single set-up, making wider deployment of multiple systems, and larger cohorts, increasingly feasible. In providing extensive detail, the current work encourages further application of such monitoring capability. Widespread deployment or biomonitoring networks could revolutionise water management, improving protection of aquatic ecosystems and human health. Such ecological understanding aids bivalve conservation, of particular benefit to declining freshwater species.