LONG TERM DATA MONITORING (1998 - 2015): CHARACTERISTIC OF SEAWATER QUALITY AT HURUN BAY LAMPUNG  

Muawanah*, Tri Haryono,Wahyu Widiatmoko and Kurniastuty
Main Center for Marine Aquaculture, Lampung
E-mail : awanah_tj@yahoo.com

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Hurun Bay as part of Lampung Bay is one of suitable location for mariculture in Indonesia, floating net cage culture of groupers, white snapper, pompano and etc. have been going for about 28 years. Utilization of areas in term of land area as well as seawater area in the surrounding of Hurun Bay more diverse and improved from time to time, where these activities over long time will affect the quality of the environment. Therefore, it is necessary to monitor the water quality characteristics. Monitoring activities carried out every a week including temperature, DO, pH, salinity, brightness (done in situ), phosphate and DIN (Dissolved Inorganic Nitrogen). There were 682 times monitoring already done during 18 years. The measurement results showed that salinity between 20 to 33 ppt, the lowest value obtained in the first week of June 2005 as the impact of major floods through the canals and rivers. Temperature values between 28.6 to 340C, the highest temperature obtained in January 2001. Concentration of DO between 3.10 to 7.02 mg/l, the lowest concentration obtained in the second week of February 2009 as a result of the high abundance of plankton especially diatoms, in general the concentration of DO tend to  decline over time. The pH value was between 7.20 to 8.89, a decreasing and increasing of  pH is only temporary fluctuation because the seawater itself has function as buffer to stabilize pH. Concentration of DIN which is an accumulation of three N-containing compounds ammonia, nitrite and nitrate obtained between 0.003 to 4.585 mg/l, the highest concentration obtained in the first week of July 2015 as the impact of bulk discharging  shrimp ponds. Phosphate concentration between 0.001 to 1.090 mg/l which was the highest concentration obtained in the first week of July 2015. In general pattern of DIN and phosphate concentrations almost same and tend to increase over time. Generally, monitoring results can be concluded that the fluctuations of the parameters concentration were influenced by several factors such as topography, hydrology and waste material (domestic, agricultural and industrial waste). Monitoring activities were expected to assist  the implementation of environmental management for sustainable aquaculture activities and as Early Warning System in an integrated manner for reducing the level of disease in biota farming