My MSc project focused on picoplanktonic prokaryotic (bacterial) community dynamics within an open-air algae raceway fertilised by wastewater (sewage). Algae raceways are currently the cheapest available method of cultivating certain algae species. The algal biomass is then harvested and used in products of pharmaceutical, nutraceutical or even cosmetic value. Recently however, algae raceways have drawn attention as a potentially sustainable source of energy. Namely, the generation of sustainable biogas (methane) via the anaerobic digestion of algae biomass harvested from these raceways. The use of wastewater to fertilise algae raceways has also drawn much attention in recent decades due to the mutually beneficial arrangement providing a cheap source of fertiliser for the algae as well as free sewage treatment (in the form of microbially-mediated nutrient removal). However due to the complexity and instability of microbial communities, biomass (algae blooms) in outdoor raceways tends to collapse, hence compromising its feasibility as a sustainable source of energy.
Project PRODIGIO (Developing Early Warning Systems for Improved microalgae PROduction and Anaerobic DIGestIOn) is a three-year research project funded by the EU which aims to boost productivity in open-air algae raceways and develop an early-warning signal to indicate when the algae raceway begins to transition into a “failure state” (bloom collapse). PRODIGIO maintains two algae raceways in Almería, southern Spain. One fertilised with wastewater and one fertilised with artificial fertilisers. Samples are taken at both the inflow (i.e. fertiliser) and outflow (culture samples) points of the raceway, and multiple ASV (genetic) datasets are generated focusing on different aspects of microbial life within the raceways (for example the picoplanktonic <0.2 μm and nanoplanktonic <3 μm size fractions, or eukaryotic and prokaryotic communities). PRODIGIO samples are sent to the Institut de Ciéncies del Mar (ICM) in Barcelona, Spain, where DNA extraction and chemical analysis are carried out.
I carried out my project based at the ICM in Barcelona, using data provided by project PRODIGIO. I decided to focus on the wastewater raceway outflow (culture) samples of the picoplanktonic size fraction of prokaryotic communities, and I also received data pertaining to the physio-chemical environment within the raceways, including biomass productivity, nutrients (including nitrate, ammonium and phosphate), pH, dissolved oxygen (DO), photosynthetically active radiation (PAR) and photosynthetic efficiency (Fv/Fm). I carried out analyses in R, Excel and PRIMER to determine interrelationships between environmental variables and how picoplanktonic prokaryotic community dynamics are influenced/influenced by environmental factors.