The concentration of TAN in the effluent entering the
seaweed biofilter unit decreased from 95.3 (± 21.00)
μmol l−1 to 83.1 (±18.64) μmol l−1 at the outflow of
the 1500-l tanks containing Chondrus (Table 3). The
TAN concentration at the inflow of the smaller tanks
containing Palmaria was 75.4 (±12.81) μmol l−1 and
decreased to 45.4 (± 6.79) μmol l−1 in the outflow. This
corresponds to a nitrogen uptake efficiency of 14.3%
(± 12.00%) for Chondrus in the first level of the system,
and 41.0% (± 17.26%) for Palmaria, in the second level
(Fig. 2). The nitrogen uptake efficiency of the complete
cascade system was 50.1% (±27.85%) (Fig. 2). The
total nitrogen removed per day was 2.7 g per cascade
unit (one 1500-l tank and one 300-l tank, Table 3). The
complete system (3 cascade units) was able to remove
8.1 g per day, corresponding to 1.35 g N day−1 m−2