The color of EPEA: Variability in the in situ bio-optical properties in the period 2000 - 2017

The ‘Estacion Permanente de Estudios Ambientales’ (EPEA, 38° 28′ S-57° 41′ W, Argentina) is an ecological time series of in situ observations started in 2000 aiming to assess changes in the marine environment and plankton communities under a global change scenario. Bio-optical properties are studied at EPEA since the color of the ocean undergoes temporal fluctuations, both for natural and anthropogenic causes. Here we assessed whether bio-optical properties at EPEA have changed during 2000-2017, identifying the occurrence of special events and inter-annual trends in these properties. An increasing trend in chlorophyll-a concentration, possibly due to an increase in the smaller fraction of phytoplankton was observed. Although the absorption coefficient of phytoplankton did not follow a significant trend, it represented the occurrence of special events of high biomass suggesting that satellite information should be useful for the study site. The specific absorption coefficient of phytoplankton and the blue to red absorption ratio showed high values in summer and low in winter, according to the probable dominance of different size cells and their expected acclimation to the light regime. These results emphasize the relevance of periodic bio-optical in situ observations in understanding coastal ecosystems in a context of climate change.