Abstract
Filtration capacity and feeding behaviour has been intensely studied for adult mussels (Mytilus edulis), but less information is available for juvenile mussels (1.5–25 mm, <1 year), especially in natural sea water. The recent introduction of mussel seed collectors in the Netherlands prompted the need for more detailed information on juvenile mussel behaviour. To estimate the impact of juvenile populations on ecosystem carrying capacity, information on clearance rate as well as usage of different prey items is essential. Clearance rates were measured in an experimental study, incubating juvenile mussels in natural sea water. Rates were related to isometrics as well as specified for the prey items bacteria, picophytoplankton (<3 μm), nanophytoplankton (3–20 μm), and ciliates. Results showed that the clearance rate of juvenile mussels depends on shell length2, while the relationship between clearance rate and weight was more variable. Length is thus a better parameter for estimating clearance rate than weight. Ciliates and nanophytoplankton were cleared at comparable, but variable rates, while picoalgae were cleared from the water at the rate of 11–64 % compared to nanophytoplankton. For bacteria, the clearance rate was on average 9 %. This study showed different retention of particles of similar size (picoalgae and bacteria) as well as variability in particle retention for the different prey items. This variable retention efficiency could not be related to seston concentration nor to dominance in cell size. The results from this study can be used to estimate the effect of mussel seed collectors on the carrying capacity of the Dutch Wadden Sea.
Highlights
In estuarine ecosystems, suspension-feeding bivalves, like the blue mussel (Mytilus edulis), often occur in large numbers, affecting the surrounding ecosystem by filtering vast volumes of water, thereby removing different components of the plankton community (e.g. Verwey 1952; Cadee and Hegeman 1974; Cloern 1982; Dame 1996; Kreeger and Newell 1996; Wong and Levinton 2006)
Filtration capacity and feeding behaviour has been intensely studied for adult mussels (Mytilus edulis), but less information is available for juvenile mussels (1.5–25 mm, \1 year), especially in natural sea water
This study showed different retention of particles of similar size as well as variability in particle retention for the different prey items
Summary
Suspension-feeding bivalves, like the blue mussel (Mytilus edulis), often occur in large numbers, affecting the surrounding ecosystem by filtering vast volumes of water, thereby removing different components of the plankton community (e.g. Verwey 1952; Cadee and Hegeman 1974; Cloern 1982; Dame 1996; Kreeger and Newell 1996; Wong and Levinton 2006). The recent introduction of mussel seed collectors in the Netherlands prompted the need for assessing the effect of large numbers of juvenile individuals on the carrying capacity of the surrounding ecosystem. There have been numerous studies performed on the filtration capacity and feeding behaviour of mussels, but these studies were mainly confined to larger ([15 mm) individuals Most studies on filtration rates of mussels were performed under controlled laboratory conditions using algal cultures. These experiments resulted in estimates of the maximum clearance rate, while it can be expected that under natural conditions, clearance rates will be lower. The need for information on actual realised clearance rates under natural conditions and the specific usage of natural plankton by these dense collections of juvenile mussels has been recognised (Bunt et al 1992; Cranford et al 2003, 2011; Trottet et al 2008)
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