Eutrophication of surface water bodies is a major environmental problem worldwide that, despite being a process that can occur naturally can be greatly accelerated by anthropogenic activities, namely through the abnormal enrichment of nutrients in the waters.
As a result of agricultural activities, numerous lakes in the Azores archipelago are impacted by eutrophication due to the excessive nutrient loads, resulting in one of the most serious problems regarding surface water quality in the Azores archipelago. Some eutrophic lakes contain numerous macrophytes or present frequent algae blooms during summer, that contributes toward the accumulation of organic matter in the bottom sediments. ~
In studied lakes (Caiado Lake and Sete Cidades Lake in Pico and São Miguel Island, respectively), a relationship was observed between CO2 flux emission and the eutrophication indices, mainly due to the influence of the areas occupied by the masses of macrophytes and algae, over the CO2 flux. For the winter and summer surveys, it can be seen that, The higher biogenic-derived CO2 release is enhanced by the water temperature, as suggested by the surface gradient measured in these areas each lake in the different surveys (shown through the comparison of the temperature and CO2 flux maps).
We argue that the eutrophication processes increase the CO2 emission rates in the lake, and these contributions should also be evaluated in other lakes with similar conditions as may be relevant to evaluate the carbon biogenic and hydrothermal total budget.