Aquaculture & Fisheries

Biography

Biography: Hochard Sebastien

Abstract

Although sediment is considered as an important detritic component of earthen ponds used in shrimp production, benthic primary production is usually considered as negligible. Yet Benthic Micro Algae (BMA) are a major component of shallow marine ecosystem functioning. They produce labile organic matter at the sediment surface and control the nutrient exchanges at the water-sediment interface. Thus BMA may have an influence on the benthic pelagic coupling during the rearing period and influence the dynamics of water quality and phytoplankton communities. This may have direct consequences in the pond management strategy. These issues were investigated in the context of New Caledonian shrimp aquaculture, which is based on the rearing of Litopenaeus stylirostris in semi intensive pond. Author scientific approach included both industrial pond surveys and mesocosm experiments. Authors’ research showed that BMA could reach a biomass that exceeded phytoplankton biomass in both systems. BMA biomass was controlled by nutrient input (food), light availability and shrimp bioturbation. BMA activity had a significant contribution to the total pond metabolism and had an important role in the control of nutrient exchanges at the water-sediment interface. The controlling factors appeared to be different for nitrogen and phosphorus, leading to fluctuating release of nutrients from the sediment to the water column, both in term of fluxes and N/P ratio. These have direct consequences on the pond management. They had discuss these features in term of fertilization strategy, and pond sediment monitoring and management.