One of the constraints on K. alvarezii cultivation in Indonesia is the decrease in production during the summer season. Water quality parameters such as temperature and light intensity will change between seasons. We investigated the effects of temperature and light intensity on the production of K. alvarezii (brown type) over the summer season by observing photosynthetic activity based on the level of chlorophyll fluorescence measured by PAM (Pulse Amplitude Modulated) Imaging. Photosynthetic parameters of Maximum Quantum Yield (Fv/Fm) and Effective Quantum Yield (ΦPSII) were observed in order to determine the photosynthetic-stress and the potential for recovery of affected seaweed. Based on the Fv/Fm value, K. alvarezii could not recover after experiencing photosynthetic-stress at the higher temperature (34 ᵒC) and higher light intensity (1,000 mol photons m-2 s-1) levels. We found that ΦPSII was 0 e per photon at light intensity of 1000 mol photon m-2 s-1 and at temperatures of 20, 27 and 34 ᵒC. Based on temperature and light intensity recorded in seaweed farming areas around South Sulawesi, the findings show that conditions prevalent are often outside the range suitable for K. alvarezii photosynthetic activity, especially during the summer season.