Ecophysiological studies of selected macro- and microalgae: production of organic compounds and climate change interactions
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This study focused on algal ecophysiological and chemical responses of marine algae to environmental impacts, in particular, light including UV radiation, temperature and nutrients. Marine algae influence climate by affecting the global biogeochemical cycles and the energy budget through the emission of aerosols and gases. Experiments were conducted with microalgae under different irradiance, UV radiation and temperature to assess the usefulness of pigments as a good proxy for biomass indicators. Chlorophyll a (chl a) content of microalgae varied with different species and changes in temperatures, irradiances and nutrients had a significant effect. Hence, mechanisms controlling microalgal growth and physiology should be considered in assessment of primary production as quantitative analysis using pigments is hindered by intraspecific variability of cellular pigment contents due to photoacclimation. Algal metabolic compounds are released into the water contributing to the dissolved organic matter (DOM) pool. Accumulation of short-term phlorotannin and mycosporine-like amino acids content in macroalgae were species specific and were influenced by temperature, light and UV radiation. The production of dissolved organic carbon (DOC) in oceans is important due to its potential to drive primary production when inorganic nutrients such as nitrates are depleted. The present study showed the release of DOC from healthy cells of microalgae during their growth. Species specific variations of DOC exudation for both macro- and microalgae to temperature and light were observed. This study has also provided insights into the chemical composition and properties of fine primary marine aerosols in simulated high microalgal bloom conditions. This may have important consequences in the prediction of cloud condensation nuclei (CCN) properties of marine aerosols and in the role of marine algae as a regulatory feedback mechanism via biogenic aerosol production. Marine algae, therefore plays an essential role not only as indicators of climate change but also by mediating global climate through their emission potentials and influencing cloud formation.