{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,28]],"date-time":"2026-03-28T00:01:04Z","timestamp":1774656064443,"version":"3.50.1"},"posted":{"date-parts":[[2026]]},"group-title":"SSRN","reference-count":51,"publisher":"Elsevier BV","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>The use of microalgae-based photobioreactors (PBRs) offers a promising alternative for the sustainable tertiary treatment of urban wastewater. While the role of bacteria in such systems is well studied, the diversity and ecological function of eukaryotic communities remain poorly understood. Here, we used 18S rRNA gene amplicon sequencing to characterize eukaryotic diversity in outdoor PBRs fed with real wastewater operated with two hydraulic retention times (HRT), of 24 and 48h, over four seasons which presented distinct climate drivers (temperature, light intensity and rainfall). Our results revealed strong seasonal structuring of the communities, shaped by predator\u2013prey interactions and temperature-dependent selection, while HRT had no significant impact. High temperatures and light intensity favoured thermotolerant microalgae such as Chlorella, likely due to reduced grazer pressure, and coincided with the highest phosphate removal which was likely performed by Chlorella under phosphorus depletion conditions. In contrast, seasons with mild temperatures, like spring, showed a peak in rotifer abundance and low microalgal biomass, correlating with enhanced biogas and methane production, as well as improved ammonium removal\u2014possibly driven by rotifer-mediated nutrient cycling. In seasons characterized by lower temperatures and more abundant rainfall, communities were more balanced, with co-occurrence of chlorophytes (Tetradesmus and Desmodesmus) and predators such as rotifers and amoebae. However, nutrient removal efficiency declined during these seasons, likely due to increased rainfall-driven dilution and reduced phosphorus uptake under suboptimal N:P ratios. Correlation network analyses highlighted season-specific interactions among taxa, reflecting complex ecological dynamics. These findings demonstrate the critical role of eukaryotic communities in influencing both biomass composition and nutrient removal, offering valuable insights for the seasonal optimization of PBR performance in wastewater treatment.<\/jats:p>","DOI":"10.2139\/ssrn.6481741","type":"posted-content","created":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T23:36:37Z","timestamp":1774654597000},"source":"Crossref","is-referenced-by-count":0,"title":["Seasonal dynamics shape eukaryotic communities and performance in wastewater photobioreactors"],"prefix":"10.2139","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1964-6819","authenticated-orcid":true,"given":"T\u00e2nia","family":"Aires","sequence":"first","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9579-9606","authenticated-orcid":true,"given":"Aschwin  H.","family":"Engelen","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2993-8572","authenticated-orcid":true,"given":"Etiele","family":"Greque de Morais","sequence":"additional","affiliation":[]},{"given":"Jos\u00e9","family":"Marques","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3101-693X","authenticated-orcid":true,"given":"Jo\u00e3o","family":"Varela","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4077-855X","authenticated-orcid":true,"given":"Lu\u00edsa  Afonso","family":"Barreira","sequence":"additional","affiliation":[]}],"member":"78","reference":[{"key":"ref1","article-title":"Wastewater treatment in 2050: Challenges ahead and future vision in a European context","volume":"2","author":"A Soares","year":"2020","journal-title":"Environ. 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