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

• 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 (D-b) 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 D-b, In both species D-b 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 D-b 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.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

sediment reworking

image analysis

food availability

scaling

luminophores

Abra ovata

Abra nitida

LONGICALLUS SCACCHI BIVALVIA

PARTICLE MIXING RATES

EARLY DIAGENESIS

DEPOSIT-FEEDERS

ORGANIC-MATTER

STYLODRILUS-HERINGIANUS

RADIOTRACER

MEASUREMENT

ECOSYSTEM FUNCTION

SOLUTE TRANSPORT

DITRUPA-ARIETINA

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