Relationship between filtration activity and food availability in the Mediterranean mussel Mytilus galloprovincialis

• Published in: Marine biology 2007-11, Vol.152 (6), p.1293-1307
• Main Authors: MAIRE, Olivier, AMOUROUX, Jean-Michel, DUCHENE, Jean-Claude, GREMARE, Antoine
• Format: Article
• Language: English
• Subjects: Algae; Animal and plant ecology; Animal behavior; Animal, plant and microbial ecology; Biological and medical sciences; Diet; Filtration; Food availability; Fundamental and applied biological sciences. Psychology; Inorganic matter; Invertebrates; Isochrysis galbana; Marine; Marine biology; Measurement techniques; Mollusca; Mollusks; Mytilus edulis; Mytilus galloprovincialis; Sea water ecosystems; Synecology; Valves
• ISSN: 0025-3162; 1432-1793
• DOI: 10.1007/s00227-007-0778-x

The filtration activity of the Mediterranean mussel, Mytilus galloprovincialis, was assessed under different concentrations and compositions of seston by using a new automated image acquisition and analysis system. This approach allowed for frequent and simultaneous measurements of valve gape and exhalant siphon area. Filtration rates were measured through clearance measurements whereas pumping rates were measured using hot-film probes. The average filtration rate (17.5 l g h-1 DW-1 for a 0.36 g DW mussel) recorded during the present study was higher than those available for Mytilus edulis when standardized to flesh dry weight but almost equivalent (17.5 l h-1 g DW-1 for a 53 mm shell length mussel) to those rates when standardized to shell length. Immediately after the addition of algal cells (Isochrysis galbana; 4.5 mcm in size), valve gape, exhalant siphon area and filtration rate increased quickly as mussels reached their maximum filtration activity. These three parameters then gradually decreased until complete closure of the shell. The algal cell concentration inducing this transition was close to 800 cells ml-1 and 0.5 mcg Chl a l-1. When algal concentration was maintained above this threshold by successive algal additions, both valve gape and exhalant siphon area remained maximal. Temporal changes in the exhalant siphon area were continuous as opposed to those of valve gape. Therefore, despite the significant correlation between these two parameters, valves and siphon were sometimes dissociated due to a reduction of the area or even a closure of the exhalant siphon while the valves remained open. The velocity of exhaled water tended to be constant irrespective of exhalant siphon area and thus pumping rates were a linear function of exhalant siphon area. Consequently, reductions in exhalant siphon area and pumping rate were almost similar in M. galloprovincialis. Our results thus clearly support the hypothesis that exhalant siphon area constitutes a better proxy of pumping rate than valve gape as already suggested for Mytilus edulis. Finally, the high filtration rates measured during the present study together with the high concentrations of inorganic matter (> 40 mg DW l-1) requested to alter those rates suggest that the studied mussels were well adapted to oligotrophic waters featuring strong hydrodynamism and frequent sediment resuspension events. [PUBLICATION ABSTRACT]