Soil nitrifying enrichments
as biofilter starters in intensive recirculating saline water aquaculture
A. Gross, A. Nemirovsky, D. Zilberg, A. Khaimov, A.
Brenner, E. Snir, Z. Ronen, A. Nejidat-2003
Aquaculture, 223(1-4): 51-62
Abstract:
Intensive recirculating aquaculture relies on biofilters to sustain
satisfactory water quality in the ponds. Establishment of new biofilters in
aquaculture ponds without a start-up culture requires a long period of time
and may therefore cause significant losses and environmental harm due to
discharge of nitrogen-rich effluents. A laboratory scale setup (7-l aquaria
with shrimp and fish) demonstrated that an external start-up nitrifying
enrichment culture performed similarly to the natural bacterial population
of an established pond biofilter, and superior to the performance of similar
biofilters without a start-up culture (control). Ammonia concentration in
the control treatment increased daily and reached 18 mg l-1
during a 14-day experiment, whereas in the treated aquaria, it averaged less
than 2 mg l-1. Fish growth and survival were similar in the
treated aquaria (average growth of 0.45 g/14 days, and 95% survival) and
significantly higher than in the control (average growth of 0.0 g/14 days,
and 80% survival). The source for the enrichment cultures was soil samples
collected from the region where the farm is situated. This approach may lead
to the development of bacterial amendments (probiotic products) that can be
used as start-up cultures for new operations or damaged filters, and
potentially enhance nitrification in established filters. As the cultures
are collected from soils, it is unlikely that they will be contaminated with
fish disease-causing agents. This will improve water quality and
consequently aquatic animal production.