3. Results and discussions
3.1. Environmental conditions
Environmental conditions at the fish farm and the control site
during the study were monitored. The WT, SAL, DO and pH values
were not significantly different (t-test, all p > 0.05) between the
sampling sites (Table 1). However, higher dissolved nitrogen levels,
including the NH4–N, NO2–N and NO3–N contents, were all found
in fish farm than those in control site (t-test, all p < 0.05). The phosphate
contents of both sampling sites were low and constant during
the study period, and no significant differences (t-test,
p = 0.059 and p = 0.075, respectively) were found.
The average DIN:DIP ratio of the fish farm water (Table 1) was
far above the Redfield ratio of 16, suggesting that DIN was in excess
of seaweed requirements relative to DIP. While, the average DIN:-
DIP ratio of the seawater from the control site was not far from the
Redfield ratio, but with P in excess, indicating possible N limitation
for the seaweed growth.