Particle clearance and yield in relation to bacterioplankton and suspended particulate availability in estuarine and open coast populations of the mussel Mytilus edulis

Abstract

Measurements were made of resource availabihty and the filtration rate and particle retention efficiency of mussels M y t h s edulis L. from an estuarine site on the River Lynher and from an open coastal site at Whitsand Bay, Cornwall, UK. Small cocci of 0.25 km, large cocci of 0.56 pm and small rods of 0.725 pm mean spherical diameter comprised 87 % of the free-living bacterial population at Whitsand Bay and 86% in the Lynher estuary during September 1984. Free-living bacteria represented only 5 % of the carbon and 9.7 and 11 3 O/O respectively of the nitrogen potentially available for exploitation as a food resource in the water column at the estuanne and open coast sites. Weightspecific clearance rate of particles > 12.7 km diameter by M. edulis from the Lynher estuary was approximately 2.5 1 g-' h-' at 14'C whdst that for mussels from Whltsand Bay was 2.6 1 g-' h-'. Relative retention efficiency of particles was generally similar for mussels from the 2 sites, declining to ca 28 O/O for natural bacterioplankton of 0.513 to 0.524 pm mean spherical diameter. These results suggest no significant intraspecific differences in filtration rates or relatlve particle retention efficiencies, for mussels from the 2 sites, in spite of major differences in partlcle concentrations at the sites. Although ca 65 O/O of the natural bacterioplankton were cleared from the expenmental vessels after 335 min at 14 'C, carbon and nitrogen yield from bacterioplankton at natural concentrations is likely to be small. The complete particle spectrum, represented by living phytoplankton cells, detritus and bacterioplankton, would need to be exploited by the Whitsand Bay population of mussels to sustain carbon and nitrogen demands since the total yleld from all particulate size classes was only 713 ug C h-' and 78 pg N h-' compared with an estimated minimum requirement of 737 pg C h-' and 45.5 ug N h-'. The total carbon and nitrogen resource in the Lynher estuary was well in excess of the estimated requirements of the mussels. However, it is estimated that the free-living bacterial resource would contribute only 4.2 % to the carbon budget and 17 % to the nitrogen budget of the Lynher estuary mussels compared with 1.6 and 7 % respectively of that of the open coast mussels. These results suggest that mussels from both the estuarine and coastal sites utilize phytoplankton or similar sized particles as a primary nutritional resource, although in other systems where bacterial standing stocks are high relative to other particulate resources, bacterioplankton may make a more important contribution to the carbon and nitrogen requirements of filter-feedmg organisms.

Faecal bacteria in Perna perna (Linnaeus, 1758) (Mollusca: Bivalvia) for biomonitoring coastal waters and seafood quality

“…The clearance rates obtained for P. perna in this study (from 0.16 to 0.47 l h -1 per mussel), were lower than those obtained by Resgalla Jr. et al (2006), however, these latter authors offered phytoplanktonic organisms to the mussels, so it was already expected that the clearance rates obtained by the use of bacterial cells would be lower since the size of the food offered greatly affects the results, as showed by Lucas et al (1987).…”

Length- and weight-dependent clearance rates of juvenile mussels (Mytilus edulis) on various planktonic prey items

“…This sharp decline in retention efficiency with decreasing particle size has been reported before (Lucas et al 1987;Matthews et al 1989;Ward and Shumway 2004). Preferential capture of picophytoplankton over bacteria must be based on properties other than cell size alone.…”

“…At times when total cell volume was dominated by larger cells, capture efficiency increased to larger particles (20-30 lm). Calculating the carbon per size class for data published in Lucas et al (1987) revealed a similar pattern; retention efficiency for 1.6-lm particles differed between two sites. The highest retention efficiency for these picoparticles corresponded to relative small (8 lm) particles dominating total carbon availability, while at the site with a lower retention the carbon availability was dominated by 12-to 16-lm particles.…”

Impact of introduced juvenile mussel cultures on the pelagic ecosystem of the western Wadden Sea, The Netherlands

“…From previous studies, it was already known that adult mussels are not very efficient suspension feeders on small planktonic components like bacteria and picophytoplankton (< 2 µm), while they are generally assumed to better retain larger organisms like nanoand microsized plankton (> 2 µm) including both autotrophs and heterotrophs (Lucas et al 1987, Horsted et al 1988, Matthews et al 1989, Kreeger & Newell 1996, Ward & Shumway 2004, Trottet et al 2008a, Strohmeier et al 2012. Using a mesocosm set-up in which natural plankton was exposed to mussel filtration, we confirmed for juvenile mussels (< 25 mm) that filtration mainly affected the larger components of the plankton community (3−200 µm).…”