Increased rainfall remarkably freshens estuarine and coastal waters on the Pacific coast of Panama: Magnitude and likely effects on upwelling and nutrient supply

Valiela, Iván; Camilli, Luis; Stone, T.A.; Giblin, Anne E.; Crusius, John; Fox, Sophia E.; Barth-Jensen, Coralie; Monteiro, Rita Oliveira; Tucker, Jane; Martinetto, Paulina; Harris, Carolynn

doi:10.1016/j.gloplacha.2012.05.006

Cited by 29 publications

(23 citation statements)

References 21 publications

(44 reference statements)

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“…5). During December 2010, the region was affected by La Niña-associated intensification of rainfall that led to a remarkable freshening of estuaries and coastal waters (Valiela et al 2012). The amount of rain during that wet season was the largest of any of our sampling periods.…”

Section: Ammoniummentioning

confidence: 92%

“…Annual rainfall ranges from 2000 to 4000 mm, and has been increasing during the last decade (Valiela et al 2012). Where forested, the vegetation of the watersheds is seasonal wet forest, with diverse, tall canopies containing trees up to 40−60 m covering steep slopes.…”

Section: Sites Watershed Delineation and Estimation Of Deforestatiomentioning

confidence: 99%

“…This broad span provided a reasonably wide range within which we could assess the effects of conversion of forest to pasture on watershed nutrient export to freshwater streams and estuaries. The gradient in land cover involved was essentially a shift between forest and pastures, since the areas of other types of land cover in the region were small (Valiela et al 2012). There were minimal areas of recovering forest vegetation, because owners maintained pastures by removal of woody invaders using machetes and selective burning.…”

Section: Watershed Deforestationmentioning

confidence: 99%

“…5), differences in concentrations were less evident, and concentrations in water leaving estuaries were lower than concentrations in surface near-shore water (blue symbols in Fig. 10), but estuarine flows were greater, and there were salinity dilutions in near-shore surface water (Valiela et al 2012), so it is hard to speculate as to net effects. To more clearly show the contrasts between water leaving estuaries, and receiving near-shore water, we calculated the ratio of normalized concentrations of nutrients at the estuary mouth, divided by concentrations in near-shore surface water (Fig.…”

Section: Exports Of Nutrients From Estuariesmentioning

confidence: 99%

“…This event reversed the usual direction of forcing, and marine imports altered conditions up-estuary. The second event took place during the wet season of 2010, when record La Niña conditions led to higher-than average wet season rainfall (2984 mm compared to a mean of 2561 mm for 2004 to 2009, a 17% increase, from region-wide data from the Tropical Rainfall Measuring Mission, www.trmm.gsfc.nasa.gov/) through northern South America and Central America (Valiela et al 2012). Local rainfall during the wet season reached considerably larger amounts in the local area of our study (SERVIR, the Mesoamerican Regional Climate Monitoring Center, and authors' pers.…”

Section: Introductionmentioning

confidence: 99%

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Nutrient gradients in Panamanian estuaries: effects of watershed deforestation, rainfall, upwelling, and within-estuary transformations

Valiela¹,

Giblin²,

Barth-Jensen³

et al. 2013

Mar. Ecol. Prog. Ser.

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To test whether deforestation of tropical forests alters coupling of watersheds, estuaries, and coastal waters, we measured nutrients in 8 watershed-estuarine systems on the Pacific coast of Panama where watershed forest cover ranged from 23 to 92%. Watersheds with greater forest cover discharged larger dissolved inorganic nitrogen concentrations and higher N/P into estuary headwaters. As freshwater mixed with seawater down-estuary, within-estuary biogeochemical processes erased the imprint of watershed deforestation, increased ammonium, lowered nitrate concentrations, and otherwise altered down-estuary water column composition. As estuarine water left mangrove estuaries, ammonium, nitrate, and phosphate, but not dissolved organic nitrogen, were exported to receiving near-shore waters. Mangrove estuaries in this region thus provide important ecological services, by uncoupling coastal waters from changes in terrestrial land covers, as well as by subsidizing adjoined receiving coastal waters by providing nutrients. The pattern of land−sea coupling and exports was disrupted during La Niña-influenced conditions. In one instance when La Niña conditions led to upwelling of deeper layers, high concentrations of marine-derived ammonium were inserted into estuaries. In another instance, La Niña-associated high rainfall diluted nutrient concentrations within estuaries and lowered salinity regionally, and the fresher upper layer impaired coastal upwelling. Regional rainfall has increased during the last decade. If La Niña rainfall continues to increase, disruptions of current land−estuary−sea couplings may become more frequent, with potentially significant changes in nutrient cycles and ecological services in these coupled ecosystems.The impacts of anthropogenic changes in land cover on the export of nutrients to tropical estuaries are attenuated by mangroves (inset).Photos: I. Valiela FREE REE ACCESS CCESS

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Section: Ammoniummentioning

confidence: 92%

Section: Sites Watershed Delineation and Estimation Of Deforestatiomentioning

confidence: 99%

Section: Watershed Deforestationmentioning

confidence: 99%

Section: Exports Of Nutrients From Estuariesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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