Application of a spectrofluorimetric tool (bbe BenthoTorch) for monitoring potentially toxic benthic cyanobacteria in rivers.
Over the last decade reports of animal poisoning following accidental consumption of neurotoxin-producing benthic cyanobacteria (mainly Phormidium spp.) have increased. There is a need for rapid and cost-effective tools to survey benthic cyanobacteria. In this study we assessed the performance of the BenthoTorch, a fluorometric probe that provides in situ estimations of cyanobacteria, diatoms and green algae biomass in biofilms. Biofilms (n = 288) were analysed from two rivers in France and eight in New Zealand. Correlations between chlorophyll-a measured using the BenthoTorch and spectrophotometry were higher for thin (<2 mm) compared to thick (>2 mm) biofilms (r(2) = 0.58 and 0.27 respectively; p < 0.001). When cyanobacteria represented less than 50% of the total biomass (based on biovolumes), microscopic and BenthoTorch compositional estimations were significantly correlated (r(2) = 0.53, p < 0.001). Conversely, there was no correlation when cyanobacteria exceeded 50% of the total biomass. Under this scenario diatoms were overestimated. Our results suggest that the observed biases occur because the BenthoTorch only measures the upper biofilm layer and it underestimates the biomass of phycoerythrin-containing cyanobacteria. To improve the performance of this sensor and render it a useful tool for a rapid evaluation of benthic cyanobacterial biomass in rivers, we propose that: (i) the algorithms based on the LEDs responses currently available on this tool need revision, (ii) new excitation wavelengths should be included that allow the fingerprints of phycoerythrin-containing cyanobacteria to be discriminated, and (iii) a sensor that penetrates the biofilms is needed to obtain more accurate estimates of cyanobacterial biomass.
Unité Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, CNRS, Case 39, 57 Rue Cuvier, 75005, Paris, France; INRA, IEES Paris, Université Pierre et Marie Curie (UPMC), 4 Place Jussieu, 75005, Paris, France.
Isidora
I
Echenique-Subiabre
Unité Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, CNRS, Case 39, 57 Rue Cuvier, 75005, Paris, France.
Caroline
C
Dalle
Unité Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, CNRS, Case 39, 57 Rue Cuvier, 75005, Paris, France.
Charlotte
C
Duval
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Mark W
MW
Heath
Unité Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, CNRS, Case 39, 57 Rue Cuvier, 75005, Paris, France.
Alain
A
Couté
Cawthron Institute, Private Bag 2, 7001, Nelson, New Zealand; Environmental Research Institute, University of Waikato, Private Bag 3105, 3240 Hamilton, New Zealand.
Susanna A
SA
Wood
INRA, IEES Paris, Université Pierre et Marie Curie (UPMC), 4 Place Jussieu, 75005, Paris, France.
Jean-François
JF
Humbert
Unité Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, CNRS, Case 39, 57 Rue Cuvier, 75005, Paris, France; Université Paris Diderot, 5 Rue T. Mann, 75013, Paris, France. Electronic address: quiblier@mnhn.fr.
Catherine
C
Quiblier
D000818:Animals; D018533:Biomass; D000460:Chlorophyta; D000458:Cyanobacteria; D017377:Diatoms; D045483:Rivers / Q000382:microbiology*
Benthic cyanobacteria monitoring; BenthoTorch; Chlorophyll-a; Phormidium spp; Phycoerythrin