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

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 (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. KEY WORDS: Sediment reworking · Image analysis · Food availability · Scaling · Luminophores · Abra ovata · Abra nitida Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 319: [135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153] 2006 metal-doped sediment, chlorophyll a, luminophores) have been used to estimate sediment reworking by benthic fauna (Robbins 1982, Krezoski et al. 1984, Smith et al. 1986, White et al. 1987, Sharma et al. 1987, Sun et al. 1991, Wheatcroft 1992, Gérino et al. 1998. These tracers are indicative of sediment reworking occurring at different timescales. Luminophores (i.e. fluorescent particles) have been widely used in laboratory (Mahaut & Graf 1987, Gérino et al. 1998, Ouellette et al. 2004, Mermillod-Blondin et al. 2005 and in situ experiments (Mahaut & Graf 1987, Gérino 1990, Gérino et al. 1994, 1998, Biles et al. 2002, Mugnai et al. 2003, Solan et al. 2004b. Experiments classically consist of spreading luminophores at the surface of experimental sediment cores containing test organisms at time 0 and then incubating those cores for a known amount of time. At the end of the experiments, the cores are sliced horizontally and the vertical profiles of luminophore concentration assessed. The profiles are fitted to mathematical models that allow computat...

A multiple biomarker approach to tracking the fate of an ice algal bloom to the sea floor

“…Increasing food availability can increase foraging activity by benthic animals (Jumars and Wheatcroft 1989;Maire et al 2006), which can aVect sediment proWles of pigments and other constituents. Moreover, chl a:phaeo ratios can be used as indicators of the degradation of organic matter (Boon and Duineveld 1996).…”

Linking feeding activity and sediment reworking in the deposit-feeding bivalve Abra ovata with image analysis, laser telemetry, and luminophore tracers

“…The results showed that the addition of low concentrations of organic matter significantly enhanced the feeding activity of this bivalve. In sediment column experiments using thin aquaria, and the same techniques with Abra ovata, a low organic input also induced a significant increase of vertical sediment mixing (Maire et al 2006), suggesting a positive relationship between the intensity of feeding activity and vertical sediment mixing. However, these measurements were not made simultaneously, since activity was measured at the sediment surface whereas sediment mixing was measured within the sediment column.…”

“…Through these ecological processes, the infauna has an impact on oxygen uptake (Andersen & Kristensen 1988, Glud et al 2003, porewater fluxes (Marinelli 1992(Marinelli , 1994, and sediment reworking (Rhoads 1974, Aller 1982. The resulting effects are clearly dependent on the nature and the intensity of infaunal activity (Boudreau & Marinelli 1994, Gérino et al 1998, Maire et al 2006.…”

“…These approaches combine luminophore pulses and high resolution image analysis to estimate vertical sediment mixing over short time scales (i.e. a few minutes, Solan et al 2004, Maire et al 2006. Similar image analysis techniques also allow continuous quantification of infaunal activity at a high spatial resolution (Duchêne & Rosenberg 2001, Hollertz & Duchêne 2001.…”

“…New experimental techniques in sediment profile imaging have recently been introduced to assess vertical sediment mixing (Gilbert et al 2003, Solan et al 2004, Maire et al 2006. These approaches combine luminophore pulses and high resolution image analysis to estimate vertical sediment mixing over short time scales (i.e.…”