Cyanobacterial occurrence and detection of microcystins and saxitoxins in reservoirs of the Brazilian semi-arid

Fonseca, Jessica Roberts; Vieira, Pryscila Cynara Soares; Kujbida, Paula; Costa, Ivaneide Alves Soares da

doi:10.1590/S2179-975X2814

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Articles • Acta Limnol. Bras. 27 (1) • Jan-Mar 2015 • https://doi.org/10.1590/S2179-975X2814 copy

Cyanobacterial occurrence and detection of microcystins and saxitoxins in reservoirs of the Brazilian semi-arid

Ocorrência de cianobactérias e detecção de microcistinas e saxitoxinas em reservatórios do semiárido brasileiro

Authorship SCIMAGO INSTITUTIONS RANKINGS

Aim:

The rapid spread of cyanobacteria in water sources and reservoirs has caused serious environmental damage and public health problems, and consists in a problem that challenges the institutions responsible for providing water to the population. In this study, the quantification of microcystin, saxitoxins and cyanobacteria levels was performed over 3 years in the semi-arid reservoirs of Rio Grande do Norte (Brazil). In addition, we analyzed the seasonal distribution of cyanotoxins and the percentage of cyanobacteria and cyanotoxins which were above the limit established by Brazilian law.

Methods

The study was conducted between 2009 and 2011 in four dams with six sites: Armando Ribeiro Gonçalves (ARG) in Itajá, San Rafael (SR) and Jucurutu; Passagem das Traíras (PT); Itans and Gargalheiras (GARG). Cyanobacteria presence were quantified and identified and the presence of microcystins (MCYs) and saxitoxins (STXs) was investigated by ELISA.

Results

The densities of cyanobacteria were found to be above the permitted in 76% of cases. The ELISA results showed that of the 128 samples analyzed, 27% were above the maximum allowed by the Brazilian Ministry of Health Order 2914/2011. A seasonal pattern for the presence of MCYs was found (0.00227 to 24.1954 µg.L^–1), with the highest values in the rainy season. There was no clear seasonal pattern for STXs (0.003 to 0.766 µg.L^–1).

Conclusions

This study showed the importance of establishing a water quality monitoring for human consumption and its potability standards since the concentration of MCYs in some samples was above the maximum limit allowed by Brazilian law, thus posing a risk to public health since the conventional water treatment is not able to eliminate these potent hepatotoxins.

microcystin, saxitoxin; ELISA; cyanobacteria; semi-arid reservoirs

RESERVOIR	ARG	PT	ITANS	GARG
Maximum volume (x 10⁶ m³)	2.400.0	48.8	81.7	44.4
AAV 2009-2011 (x 10⁶ m³)	2.055.0	39.2	61.3	32.5
Zmax (m)	40	25	23	29
Zm mean (m)	12.2	3.9	5.1	4.4
RT (m³/anos)	3.65	0.26	2.46	6.22
VMA 2009 (%)	95	94.0	88.2	82.1
VMA 2010 (%)	77.4	31.6	63.1	52.5
VMA 2011 (%)	91.2	40.1	75.2	66.1

	ITAJÁ	SR	JUCURUTU	ITANS	PT	GARG
Transparency (m)	1.0 (0.5-2.0)	0.8 (0.6-1.5)	0.5 (0.2-0.9)	1.1 (0.5-3.5)	0.7 (0.3-1.3)	0.9 (0.3-1.3)
Depth (m)	25 (18-28)	19 (12-24)	1.0 (0.2-3)	3.6 (0.7-8)	1.6 (0.5-6 )	2.4 (0.6-12)
pH	8.4 (6.8-9.6)	8.3 (6.5-9.4)	7.8 (6.6-8.9)	8.7 (7.8-9.2)	8.7 (7.4-9.5)	8.8 (7.4-10)
Conductivity (S cm^–1)	12.4 (9-15.8)	12.8 (9-17)	17.5 (10-31.3)	26.3 (17.7-35.7)	28.6 (0.5-47.9)	28.5 (19.3-37.3)
Turbidity (NTU)	95.8 (9.6-720)	256.3 (15.5-790)	257.6 (55-973)	249.7 (8.3-990)	243.6 (8.7-816.7)	242.9 ( 11-843.3)
Temperature (°C)	29 (27.2-32.2)	29 (27.1-31.9)	30.3 (26.4-33.5)	29.4 (26.5-32.1)	28.6 (26.1-30.9)	27.9 (25.2-32.7)

	ITAJÁ	SR	JUCURUTU	PT	ITANS	GARG
MICROCYSTIN (µg L^–1)
Rainy period 2009-2011	2.97 (±2.5)	1.98 (±1.7)	1.52 (±0.8)	3.58 (±2.9)	2.62 (±2.3)	5.84 (±6.5)
Dry period 2009-2011	0.44 (±0.4)	0.42 (±0.3)	0.24 (±0.3)	-	0.36 (±0.3)	0.38 (±0.3)

Rainy season 2009	2.73 (±0.1)	1.31 (±0.2)	1.84 (±0.6)	3.24 (±2.8)	5.19 (±0.7)	13.29 (±15.4)
Rainy Period 2010	5.62 (±0.9)	3.90 (±2.4)	2.15 (±2.7)	6.64 (±1.0)	2.09 (±3.0)	2.64 (±3.7)
Rainy Period 2011	0.57 (±0.6)	0.74 (±0.3)	0.57 (±0.3)	0.86 (±1.0)	0.59 (±0.3)	1.60 (±0.5)

Dry period 2009	0.15 (±0.1)	0.21 (±0.2)	0.08 (±0.1)	0.06 (±0.1)	0.08 (±0.0)	0.20 (±0.4)
Dry Period 2010	0.85 (±0.4)	0.70 (±0.5)	0.55 (±0.3)	0.47 (±0.3)	0.72 (±0.6)	0.67 (±0.1)
Dry Period 2011	0.33 (±0.1)	0.35 (±0.2)	0.09 (±0.0)	-	0.27 (±0.2)	0.28 (±0.4)

SAXITOXIN (µg L^–1)
Rainy period 2009-2010	0.02 (±0.0)	0.01 (±0.0)	0.17 (±0.2)	0.05 (±0.0)	0.01 (±0.0)	0.11 (±0.1)
Dry period 2009-2010	0.11 (±0.1)	0.14 (±0.2)	0.02 (±0.0)	0.07 (±0.0)	0.11 (±0.0)	0.02 (±0.0)

Rainy period 2009	0.01 (±0.0)	0.01 (±0.0)	0.01 (±0.0)	0.01 (±0.0)	0.01 (±0.0)	0.02 (±0.0)
Rainy period 2010	0.04 (±0.1)	0.02 (±0.0)	0.32 (±0.4)	0.08 (±0.0)	0.02 (±0.0)	0.21 (±0.3)

Dry period 2009	0.01 (±0.0)	0.01 (±0.0)	0.01 (±0.0)	0.11 (±0.1)	0.11 (±0.1)	0.02 (±0.0)
Dry period 2010	0.21 (±0.2)	0.27 (±0.4)	0.04 (±0.0)	0.04 (±0.1)	0.11 (±0.2)	0.01 (±0.0)
Dry period 2011	0.01 (±0.0)	0.02 (±0.0)	0.03 (±0.0)	-	0.01 (±0.0)	0.15 (±0.1)

Year 2009	ITAJÁ		SR		JUCURUTU		ITANS		PT		GARG
Cyanobacterias	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY
Planktothrix agardhii	x		x			x			x	x
Microcystis spp**	x	x		x			x	x			x	x
Cilindrospermopsis raciborskii		x		x				x	x	x	x
Anabaena spp*							x				x

Year 2010	ITAJÁ		SR		JUCURUTU		ITANS		PT		GARG
	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY
Planktothrix agardhii	x	x		x					x
Microcystis spp**			x							x	x	x
Cilindrospermopsis raciborskii	x	x	x	x			x	x	x	x	x	x
Aphanizomenon gracile	x					x					x
Anabaena spp*												x

Year 2011	ITAJÁ		SR		JUCURUTU		ITANS		PT		GARG
	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY	RAIN	DRY
Planktothrix agardhii	x	x	x	x	x		x			x		x
Microcystis spp**								x			x
Cilindrospermopsis raciborskii	x	x	x	x			x		x	x	x	x
Anabaena circinalis											x

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