In the context of a collaborative project under the CSIRO Aquawatch mission, we conducted a study focusing on identifying proxies for detecting Harmful Algal Blooms (HABs) through dissolved oxygen prediction. This study, combined with previous work on oxygen forecasts modelisation, analyzed chlorophyll fluorescence data collected by an in-situ water quality sonde and spectra data acquired by a HydraSpectra sensor to evaluate the potential of dissolved oxygen forecasting as a proxy of photosynthetic activity. By deriving chlorophyll concentration from HydraSpectra data and validating it with in-situ measurements, we obtained a correlation coefficient of 0.46 between chlorophyll and oxygen variation. Spectral reflectance analysis demonstrated the capability to identify algae types aiding in calculating essential parameters like chlorophyll concentration. Notably, a correlation of 0.47 was found between the Red Tide Index? and dissolved oxygen levels. The study suggests that oxygen variation serves as a proxy for photosynthetic activity predictions, aiding in HAB detection. This research underscores the critical role of dissolved oxygen in photosynthesis comprehension and highlights the potential of spectral analysis in understanding oceanic processes and environmental monitoring, offering insights for effective management of aquatic ecosystems.