Widdows, J., Brinsley, M.D., Salkeld, P.N. and Lucas, C.H.
Influence of biota on spatial and temporal variation in sediment erodability and material flux on a tidal flat (Westerschelde, The Netherlands)
Marine Ecology Progress Series, 194, . (doi:10.3354/meps194203).
Full text not available from this repository.
Annular flumes were used to quantlfy benthic-pelaqc exchanges in relation to changes in
current velocity and sediment biota. Various physical, chemical and biological parameters were determined
for 4 sites on the Molenplaat tidal flat in the Westerschelde (The Netherlands) during 2 field
campaigns in May-June and August-September 1996. These Pcluded: the mass of sediment eroded,
maximum and mean erosion rates, critical erosion velocity (Ucfi,), suspension feeding/biodeposition
rate, oxygen and ammonium fluxes, density of macrofauna species, chlorophyll a (chl a), colloidal carbohydrate,
and physical properties of the sediment. The study showed marked and statistically significant
spatial and temporal differences in the potential for sediment erosion. Sites in the centre of
the tidal flat were less erodable than those on the edge. All sites on the tidal flat had a significantly (p <
0.001) lower erosion potential in June (i.e. higher U,,, and lower erosion rates) compared to September.
The presence of a well-developed microphytobenthos community in June resulted in a statistically significant
relationship between U,,, and chl a/colloidal carbohydrate (r = +0.85, p = 0.01). There was a
significant relationship (r = +0.88, p = 0.005) between sediment erodab~lity (mass of sediment eroded
and erosion rate) and the density of the clam Macoma balthica, a major bioturbator of the surface sediment~.
Analysis of the data also demonstrated significant relationships between clearance rate and
Cerastoderma edule biomass (r = +0.91, p < 0.001), and between sedment chl a/colloidal carbohydrate
and C. edule biomass (r = +0.92; p < 0.001), reflecting the influence of suspension feeders on both the
water column and the sediment, through their biodeposits. The significant increase in sediment erodability
between June and September reflected the shift in the overall balance between the major 'biostabilisers'
(microphytobenthos) and 'bio-destabilisers' (bioturbating bivalves). Ths interpretation of
field-derived correlations is consistent with previously established relationships and mechanistic
understanding derived from controlled flume experiments.
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