Asian Journal of Fisheries and Aquatic Research

Seaweed Ulva sp. has great potential in sustainable integrated cultivation systems to reduce the impact of exploitation in nature. This research aimed to analyze the effect of Total Ammonia Nitrogen (TAN) concentration on the growth and chlorophyll-a content of seaweed Ulva sp. in a controlled culture system. The importance of this research is to develop sustainable cultivation systems without harming natural ecosystems by utilizing available nutrients in the form of TAN. The research method used a Completely Randomized Design (CRD) with 5 TAN concentration treatments: (P0: 0 ppm, P1: 0,010 ppm, P2: 0,025 ppm, P3: 0,050 ppm, P4: 0,075 ppm) with 3 replications. The culture was conducted for 15 days at the Aquaculture Environment Laboratory, University of Mataram. Parameters observed included absolute weight growth, specific weight growth rate, thallus sheet width and length, and Chlorophyll-a content. Research results showed that the highest absolute weight growth was achieved in treatment P1 (17,67%), the highest specific growth rate in P3 (3,39%), the highest thallus sheet width growth in P4 (2,83 cm), and the highest thallus length growth in P4 (3,50 cm). The highest Chlorophyll-a content was found in the control treatment P0 (8,06 mg/l), but based on the one-way ANOVA test results, there was no significant (p>0,05) effect on the growth of Ulva sp. However, the 2nd order polynomial regression test revealed a strong relationship between TAN concentration and growth, with R² ranging from 88-94%. Water quality during culture remained within normal range. The conclusion of this research indicates that TAN concentrations in the range of 0-0.075 ppm (mg/L) were only able to support the survival of seaweed Ulva sp. without providing significant effects on its growth. Further research with higher TAN concentration ranges is recommended to determine the optimal growth point for Ulva sp.