Analysis of the impact of Holothuria scabra intensive farming on sédiment.

We analysed the impact o f intensive Holothuria scabra farming by comparing various parameters o f the sea
cucumber food (i.e. the upper layer of the sediment) inside and outside the pens o f two farms in the south-west of
Madagascar. Our analyses showed that : (i) the proportion of the finest grain size fraction (< 250 pm) decreased from 5 to
14%, (ii) the global carbonate proportion decreased by 5%, (iii) aragonite was the carbonate type most affected by
holothurians, followed by calcite and niagnesian calcitc, (iv) the total organic matter did not vary significantly, (v) the
number o f bacteria decreased by up to 50%, and (vi) the concentration o f photosynthetic microorganisms fell by up to 22%,
within sea farm pens. Based on these results we suggest that fallow practice should be considered in the future for holothuri culture