The bad against the villain: suitability of Corbicula fluminea as a bioremediation agent towards cyanobacterial blooms.
Cyanobacteria can cause ecological, economic and human health problems, climate change trends giving them advantage over other phytoplanktonic groups. Management strategies exist to deal with the nuisance, but many are not effective due to the likelihood of cell lysis and toxin release. This study explores the suitability of the use of the invasive and widespread bivalve Corbicula fluminea for cyanobacterial control. The capacity of clams to filter and ingest cyanobacteria was evaluated using a set of bloom-forming strains comprising different morphological features potentially affecting edibility and palatability. Results generally showed limited filtration of the majority of cyanobacteria, compared with green microalgae used as the reference for optimal filtration (ca. 60 μg Chl a removed in 120 min), except for Pseudanabaena (ca. 90 μg Chl a removed) and Anabaena (ca. 120 μg Chl a removed). The specific attention given to the binomial filtration-ingestion exposed that filtration often directly relates to the deposit of cyanobacteria as pseudofaeces rather than reflects assimilation through effective ingestion. Allocation to pseudofaeces accounted for more than 50% of the Chl a removed from water for all cyanobacteria tested. Adding to effective filtration by the clam, the related accumulation of cyanobacterial biomass in pseudofaeces has the potential for further exploitation since it can be functionally paralleled with the use of synthetic flocculants for cyanobacterial (villain) removal in settings where a natural treatment alternative using an (bad) invasive bivalve could be suitable yet controlled to avoid side ecosystem effects.