Assessment of Water Quality Status, Nutrients, and Phytoplankton Communities in the Coastal Zone of East Aceh Regency, Indonesia

Abstract

Due to rapid urban development in the coastal area of the East Aceh Regency, water quality degradation and marine pollution issues become the primary concern in this region. Moreover, seasonal observation of water quality and phytoplankton has yet to be assessed. This study aimed to determine the control of seasonal water quality and nutrients over phytoplankton abundance throughout the East Aceh coast. Direct field measurements and laboratory analyses were performed to collect the primary data, whereby the sampling period was conducted during the displacement toward the ebb tide. We assessed the water quality parameters using a modified CWQI (coastal water quality index). Furthermore, linear regression and principal component analysis were performed as the basis of statistical analyses. The phytoplankton abundance was higher in April than in September, with most Bacillariophyceae and Dinophyceae in all observed stations. Except for DO and turbidity, the assessed water quality parameters (temperature, TDS, conductivity, salinity, sulfide, and TOM) are feasible for marine biota. Of particular concern, the East Aceh coast is characterized by poor-good water quality, with the CWQI value ranging from 40 to 90. Based on the regression and PCA analyses, N and P nutrients significantly control the phytoplankton abundance like a "seesaw" between April and September, with a respective coefficient determination of about 50%. Because of the tremendously high phosphate observed in April, the water condition tended to be P-limited and vice versa for September. On the other hand, instead of evoking the phytoplankton growth, each water quality parameter has a specific influence in characterizing phytoplankton communities in the study area.

Eco-environmental assessment in the Sembilan Archipelago, Indonesia: its relation to the abundance of humphead wrasse and coral reef fish composition

“…Except for station 2 (Lapoipoi), the ammonia concentration was below the allowed standard (less than 0.3 mg/ L). The ammonia concentration indicates that the N fixation and ammonification process takes place very well in the Sembilan Archipelago, which is very useful for supporting autotroph biota in photosynthesis (Tjahjo et al, 2023).…”

“…The water temperature salinity in the study area ranged from 30℃−32℃ and 31‰−34‰, respectively, with the highest value observed at Batanglampe station. The relatively higher temperature in the study area could impact the surrounding ecosystem, such as increasing heavy metals and nutrient deposition in water (Tjahjo et al, 2023;Wisha et al, 2018).…”

“…The phosphate determination was performed using 700-800 nm wavelength and ascorbic acid levels, resulting in blue phosphomolybdic complex compounds, and these compounds were reduced using ascorbic acid to yield a molybdenum complex with blue color. The color intensity reflects the phosphorus concentration (Tjahjo et al, 2023).…”

“…This significantly low nitrite concentration indicates that nitrobacteria optimally transform nitrite to nitrate within a high DO condition. Hence, the N cycle in the study area takes place normally (Tjahjo et al, 2023;Wisha et al, 2018). This state was consistent with the tremendously high nitrate concentration observed at the four observation stations, ranging from 0.475−0.603 mg/L.…”

“…The water quality status does not solely reflect the abundance of humphead wrasse and other coral reef fish composition. On the other hand, specific water quality parameters, such as nutrients and phytoplankton, would be more significant in determining the composition of higher-trophic coral reef fishes (Tjahjo et al, 2023). Therefore, even though the total value of CWQI shows a good water quality, the specific parameters considered within the calculation of CWQI may have a specific role in triggering environmental issues, such as algal blooming, nutrient enrichment, and even heavy metal deposition (Sahoo et al, 2017;Zhang et al, 2017).…”