Ulva species composition during northeast and southwest monsoons in Cuta West–Sta. Clara, Batangas City

Abstract

Batangas City is vulnerable to the anthropogenic inputs flowing from the Calumpang River to Batangas Bay and its industrialized area. Studying the composition of Ulva species is vital in monitoring and managing marine ecosystems as these species could be a bioindicator species. The composition of Ulva species in Cuta West–Sta. Clara, Batangas City was assessed during the southwest and northeast monsoons. Ulva species composition, abundance, dominance, and contribution were determined using the line transect-quadrat method. Physicochemical conditions of water, such as pH, salinity, dissolved oxygen, temperature, phosphate, and nitrate were also measured to determine any relationship with Ulva species composition during the two sampling periods. Three Ulva species were identified, namely, Ulva intestinalis, U. lactuca, and U. reticulata. During the southwest monsoon, U. intestinalis was the dominant species, which then shifted to U. lactuca during the northeast monsoon. Physicochemical conditions during the two sampling periods were closely similar and within the quality standard of the Department of Environment and Natural Resources (DENR), except for pH level, which ranged from 8.7-8.9. Dissolved oxygen showed an increasing trend from 6.13 mg/L to 9.19 mg/L. Nitrate content showed a decreasing trend from 2.18 mg/L to <0.075 mg/L. The declining trend of nitrate might indicate accumulation by U. lactuca, which may have contributed to its increased biomass during the northeast monsoon. The increase in biomass and wave action may explain the increase in dissolved oxygen during this period. Overall there is a possible relationship between the Ulva species composition and physicochemical conditions.