Fluorometer Controlled Apparatus Designed for Long-Duration Algal-Feeding Experiments and Environmental Effect Studies with Mussels

Abstract

Experimental feeding and growth studies on filter-feeding organisms often rely on constant algal concentrations maintained over extended periods of time. Here we present a fluorometer controlled apparatus (FCA) designed for feeding experiments with suspension-feeding mussels at naturally low chlorophyllaconcentrations above 0.5 µg L−1. The principle used is feedback regulation of the algal concentration based on continuous monitoring of the fluorescence intensity of chlorophyllain water pumped through the apparatus from an aquarium with mussels. The filtration rate is monitored continuously as the rate of change of measured volume of an algal stock added to the aquarium for keeping a constant algal concentration. As an example, the FCA has been used to study the filtration rates of blue mussels (Mytilus edulis) at algal concentrations both near and above the incipient saturation level for reduced filtration activity. As another example to put the FCA into perspective as a reliable method for environmental effect studies, the apparatus has been used to demonstrate the acute effect of changing salinity on the filtration rate ofM. edulis.

Allometric equations for maximum filtration rate in blue mussels Mytilus edulis and importance of condition index

“…Further, data from more recent publications (Riisgård et al 2011b;Pleissner et al 2013) as well as new experimental data have been used.…”

Effect of Salinity-Changing Rates on Filtration Activity of Mussels from Two Sites within the Baltic <i>Mytilus</i> Hybrid Zone: The Brackish Great Belt (Denmark) and the Low Saline Central Baltic Sea

“…The newly developed fluorometer controlled apparatus (FCA) constructed by Pleissner et al [24] was used in the present study with a few modifications in order to establish filtration-rate measurements on mussels at controlled salinity-changing rates. The FCA maintains a constant defined algal concentration in an aquarium with mussels by adding concentrated algal suspension to replace the amount of algal cells removed.…”

“…If the algal concentration is below a defined level a peristaltic pump starts to pump a suspension of concentrated algae from a bottle (algal stock) into the aquarium to keep the algal concentration constant. The filtration rates were estimated by means of the equation [24]:…”

“…The effect of changing salinity on the filtration rate of mussels from Great Belt has recently been studied by Pleissner et al [24] who found that the filtration rate was unaffected by decreasing salinity down to about 10 psu, but below this threshold the mussels begun to close their valves and reduce the filtration rate. When the salinity was subsequently increased, the normal filtration rate was soon after restored, and Pleissner et al [24] concluded that the filtration activity is strongly influenced by the salinity-changing rate: the faster the salinity is either reduced or increased, the more pronounced is the change in the filtration rate.…”

“…When the salinity was subsequently increased, the normal filtration rate was soon after restored, and Pleissner et al [24] concluded that the filtration activity is strongly influenced by the salinity-changing rate: the faster the salinity is either reduced or increased, the more pronounced is the change in the filtration rate.…”