MEPS 319:135-153 (2006)  -  doi:10.3354/meps319135

Effects of food availability on sediment reworking in Abra ovata and A. nitida*

Olivier Maire1,**, Jean Claude Duchêne1, Rutger Rosenberg2, Joël Braga de Mendonça Jr.1, Antoine Grémare1

1Université Pierre et Marie Curie-Paris, UMR 7621, 66650 Banyuls-sur-mer, France; CNRS, UMR 7621, 6650 Banyuls-sur-mer, France
2Department of Marine Ecology, Göteborg University Kristineberg Marine Research Station, Kristineberg, 45034 Fiskebäckskil, Sweden
*This paper is dedicated to the memory of Prof. K. R. Tenore **Email:

ABSTRACT: We used a new experimental approach involving thin aquaria, luminophores, time lapse photography and image analysis to assess sediment reworking in 2 closely related bivalves, Abra ovata and A. nitida. The method proved efficient based on the highly significant correlation between the concentrations of luminophores assessed using image analysis and direct counting of sediment slices. A. ovata and A. nitida exhibited different sediment reworking behaviours. A. ovata remained immobile within the sediment and transferred luminophores within the sediment through its siphonal activity, which resulted in the creation of typical inverse conical structures. A. nitida moved within the sediment and reworked a thinner sediment layer. Both A. ovata and A. nitida were characterised as biodiffusers. Biodiffusion coefficients (Db) were maximal at intermediate food concentration in A. ovata and at high food concentration in A. nitida. This new approach allowed assessment of the effects of spatial scale and vertical grid size on the computation of Db. In both species Db decreased with spatial scale up to 3.750 cm and then remained constant. It is suggested that this pattern partly resulted from heterogeneity linked to: (1) the mode of sediment reworking (A. ovata) and (2) the relative proportion of reworked sediment surface (A. nitida). Vertical grid size >0.250 cm resulted in a significant overestimation of Db in A. nitida, due to the low thickness of the sediment layer reworked by this species. The implications of these results on the main characteristics (duration, spatial scale, vertical grid size) of classical luminophore experiments are discussed.

KEY WORDS: Sediment reworking · Image analysis · Food availability · Scaling · Luminophores · Abra ovata · Abra nitida

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