abstract
In vivo phycocyanin (PC) fluorescence allows assessing cyanobacterial abundance in an easy, fast and cost-effective way. However, the establishment of PC thresholds is necessary for its use in routine monitoring programmes and there has been no consensus regarding their definition. This work aimed: (1) to assess the potential species-specific variation in fluorometric PC content among Microcystis aeruginosa, Nostoc muscorum and Cylindrospermopsis raciborskii; (2) to propose specific PC thresholds based on World Health Organization alert levels; and (3) to evaluate the in vivo PC signal reliability to interferences from massive algal growth and mixtures of bloom-forming cyanobacteria. Strong linear relationships were recorded between PC and cell counts, biovolume and chlorophyll a. However, a significant species-specific variation in PC was observed using cell counts. Increased microalgal densities did not cause significant interference of PC signals. Also, dual mixtures of cyanobacteria revealed strong relationships between measured and expected PC content. Results suggest that fluorometric PC is a good predictor for cyanobacterial biomass but cell number is not the best parameter to define thresholds. Biovolume should be used instead. Nevertheless, species-specific thresholds must be considered, rather than a general cyanobacterial threshold.
keywords
HARMFUL ALGAL BLOOMS; POTENTIALLY TOXIC CYANOBACTERIA; VIVO FLUORESCENCE METHOD; CLIMATE-CHANGE; FILAMENTOUS CYANOBACTERIA; FLUOROMETRIC METHOD; WATER; BIOVOLUME; RESPONSES; RESERVOIR
subject category
Marine & Freshwater Biology
authors
Macario, IPE; Castro, BB; Nunes, MIS; Antunes, SC; Pizarro, C; Coelho, C; Goncalves, F; de Figueiredo, DR
our authors
Inês Adriana Patrunilho Efe Macário
PhD Studentacknowledgements
This work was supported by European Funds through COMPETE and by National Funds through the Portuguese Science Foundation (FCT) within project PEst-C/MAR/LA0017/2013. Daniela de Figueiredo and Bruno B. Castro were also supported by FCT, by means of a postdoctoral Grant (SFRH/BPD/74184/2010) and a research contract (programme Ciencia2008, co-funded by National Strategic Reference Framework 2007-2013 and European Social Fund), respectively. The authors thank Victor Galhano for providing one of the cyanobacterial cultures.