Phosphorus and suspended matter retention in mangroves affected by shrimp farm effluents in NE Brazil

MARINS, ROZANE V.; LACERDA, LUIZ D.; ARAÚJO, ISABEL CRISTINA S.; FONSECA, LOUIZE V.; SILVA, FRANCISCO A.T.F.

doi:10.1590/0001-3765202020200758

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EARTH SCIENCES • An. Acad. Bras. Ciênc. 92 (3) • 2020 • https://doi.org/10.1590/0001-3765202020200758 copy

Phosphorus and suspended matter retention in mangroves affected by shrimp farm effluents in NE Brazil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This study compares two mangroves with different land uses in the Jaguaribe River estuary, harboring large shrimp farms, and in the more pristine Pacotí River estuary. Normalized Difference Vegetation Index (NDVI) was used to compare the overall health of the forests. Measures of suspended matter (TSS), total (TP), particulate (PartP) and soluble reactive phosphorus (SRP) in the inflow and outflow waters of tidal channels draining the mangroves were performed during tidal cycles. NDVI varied from 0.65 in the Jaguaribe estuary to 0.85 in the Pacotí, suggesting the impact of shrimp farm effluents on mangrove canopy cover. The shrimp farm influenced site showed 10 times larger absolute ∑P (TP + PartP + SRP) = 1.2-5.2 kg.hr-1) flux than the pristine site (∑P = 0.22 kg.hr-1). Tidal balances showed smaller retentions of the total influx: 28-54%; 44-45%; 38-65% and 8-53% for TSS; TP; SRP; and PartP respectively, in the shrimp farm influenced site to over 93% of the total tidal input of TSS and all P fractions in the pristine mangrove. This suggests that mangrove phosphorus accumulation is decreased in the forest with lower NDVI and limits mangrove’s potential as a natural barrier to the nutrient transport to adjacent estuarine and coastal waters.

Key words
Nutrients; shrimp farms; forest canopy; NDVI; hydrology; hydrochemistry

Sampling	Creek depth (m)	Flooded area (m²)	Temp. (°C)	Salinity	pH	Dissolved Oxygen (mg.L^-1)	Dissolved Oxygen (%) n (%)	TSS (mg L^-1)
1 ^st Campaign: Jaguaribe estuary	2.10	28.7	26.9	29.9	7.3	3.30	49.8	61
	1.70	20.7	26.9	29.9	7.4	3.60	55.6	55
	0.95	7.0	26.8	29.8	7.3	3.48	52.3	88
	0.20	1.0	27.6	29.4	7.2	3.23	49.3	94
	0.10	0.2	27.6	30.3	6.9	1.52	24.5	86
	0.50	3.0	28.4	29.2	6.8	5.03	45.3	127
	0.90	5.9	28.1	28.0	7.2	4.44	70.1	173

2 ^nd Campaign: Jaguaribe estuary	1.90	24.7	28.8	31.1	7.1	3.20	49.7	171
	1.40	14.7	27.7	32.1	7.3	3.10	46.7	138
	0.80	5.7	27.1	32.9	7.3	2.73	42.4	64
	0.35	1.7	27.6	33.9	7.2	3.47	53.0	49
	0.18	1.0	28.5	34.0	7.3	4.36	67.5	34
	0.15	0.5	29.3	34.8	7.2	5.07	80.0	34
	0.20	1.0	29.4	34.8	7.2	3.75	57.0	24
	0.35	1.7	30.5	33.5	7.2	4.12	60.6	34
	0.55	3.5	32.4	32.8	7.6	4.80	84.5	42
	0.75	5.0	31.4	32.5	7.9	7.49	125.0	55
	1.20	11.4	30.4	32.1	7.9	7.91	126.5	98
	1.90	24.7	29.8	31.9	7.8	4.80	76.2	53
	2.05	27.7	30.0	33.5	7.6	4.85	79.7	50

Campaign: Pacotí estuary	1.15	13.3	25.8	32.6	8.0	5.20	73.0	23
	1.00	10.1	25.9	33.3	7.9	5.57	82.2	69
	0.60	4.5	26.7	33.9	7.8	5.45	84.0	73
	0.30	1.5	29.3	34.1	7.7	6.17	97.5	90
	0.10	0.1	31.9	35.1	7.8	7.15	117.0	76
	0.20	0.7	28.4	32.0	7.3	4.38	67.0	65
	0.85	7.6	28.4	33.9	7.7	5.26	81.7	69
	1.60	24.3	27.6	34.9	7.8	5.35	80.1	102

Sampling	Vel. (cm s^-1)	SRP (µM)	TP (µM)	PartP (µM)	Flux SRP (g.hr^-1)	Flux PartP (g.hr^-1)	Flux TP (g.hr^-1)	Flux TSS (kg.hr^-1)
1^st Campaign: Jaguaribe river	10.6	2.5	4.3	1.9	+2,552	+1,941	+4,493	+663
	7.3	2.9	4.7	1.8	-1,514	-902	-2,416	-298
	1.1	2.6	6.5	3.9	-66	-99	-165	-24
	0	2.5	7.5	5.0	0	0	0	0
	8.8	3.1	6.7	3.6	+23	+27	+50	+7
	0.5	4.5	9.4	4.9	+24	+25	+49	+7
	0.8	2.7	10.7	8.0	+43	+129	+173	+30

2^nd Campaign: Jaguaribe river	2.4	2.7	3.2	1.3	+547	+117	+664	+50
	1.1	2.8	6.6	3.9	-151	-208	-360	-39
	0.3	2.5	9.9	7.4	-11	-34	-45	-4
	0.1	2.8	10.3	7.3	-1	-3	-4	-1
	4.9	3.7	8.7	5.0	-62	-85	-147	-13
	2.7	3.5	9.8	6.3	-15	-26	-40	-3
	0	4.8	11.6	6.8	0	0	0	0
	0	6.5	13.8	7.3	0	0	0	0
	0.1	4.0	15.9	11.9	+3	+8	+11	+1
	0.1	2.1	12.7	10.6	+2	+9	+11	+1
	0.4	2.1	8.7	6.6	+30	+94	+124	+10
	0.4	2.5	5.2	2.8	+84	+93	+177	+18
	0.1	2.1	9.3	7.2	+19	+65	+84	+3

Campaign: Pacotí river	0.3	0.3	3.3	3.0	-4	-46	-50	-5
	0.3	0.1	2.9	2.8	-2	-34	-35	-3
	0	0.6	4.6	4.0	0	0	0	0
	0	0.9	5.1	3.9	0	0	0	0
	4.0	0.8	7.3	7.7	+7	+61	+68	+9
	3.8	0.4	4.7	4.3	+44	+428	+473	+55
	3.0	0.2	4.2	4.1	+48	+1,012	+1,060	+131
	0.2	4.2	4.1	+48	+1,012	+1,060	+131	+131

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[1] Correspondence to: Rozane V. Marins E-mail: rmarins@ufc.br