Grapevine

Phytoplankton community shifts after wastewater treatment plant closure

A study by the UPV/EHU's Department of Plant Biology and Ecology has evaluated the response of Urdaibai estuary phytoplankton to the changes brought about after the closing-down of the Gernika wastewater treatment plant; a novel tool based on pigment analysis and developed by the Phytoplankton Ecology group was used. The results show that the physicochemical quality of the water has improved and this has led to changes in the phytoplankton community that are heading in the right direction.

The findings are published in the journal Marine Environmental Research.

Phytoplankton, a collection of photosynthesizing microscopic organisms, are highly sensitive to variations in nutrient availability. So they are a useful indicator when assessing excess inorganic nutrients from human activity (eutrophication) and management actions to reduce them.

Jone Bilbao, a researcher at the University of the Basque Country (UPV/EHU), has evaluated the medium-term response of the phytoplankton community in the Urdaibai estuary to the discontinuing of wastewater discharge from the Gernika wastewater treatment plant. "We analyzed the changes in the phytoplankton biomass and community composition before (in 2020) and after (in 2022) the clean-up works," she explained.

The results of the research show "significant medium-term effects on the system," said Sergio Seoane, lecturer in the department of Plant Biology and Ecology and who led the study. The nutrients supplied by the sewage station (ammonium and phosphate) decreased drastically, and this had a direct effect on phytoplankton biomass and composition of the community.