Nitrogen and phosphorus budgets for a tropical watershed impacted by agricultural land use: Guayas, Ecuador

Borbor-Córdova, Mercy J.; Boyer, E. W.; McDowell, William H.; Hall, Charles A. S.

doi:10.1007/s10533-006-9009-7

Cited by 84 publications

(69 citation statements)

References 35 publications

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“…4a), since the high flow regime mainly occurs in the summer when high temperature and sunlight contribute to algae growth . As expected, annual riverine TP flux was significantly correlated with NAPI, consistent with previous studies (Borbor-Cordova et al, 2006;Russell et al, 2008;Han et al, 2011a;Hong et al, 2012). Similar to NAPI, both NAPI AF and NAPI R presented significant correlations with riverine TP flux ( Table 2).…”

Section: Response Of Riverine Tp Export To Changes In Phosphorus Budgetssupporting

confidence: 90%

“…This estimate falls within the range reported for many studies in American, European and Chinese watersheds (i.e., 1-38%, David and Gentry, 2000;Borbor-Cordova et al, 2006;Russell et al, 2008;Han et al, 2011a;Sobota et al, 2011;Hong et al, 2012;Chen et al, 2015a). Of cumulative riverine TP flux (12.0 kg P ha À1 ) over the 32-yr period, 48% was derived from the agricultural/forest system, while 52% originated from the residential system.…”

Section: Fates Of Surplus Phosphorussupporting

confidence: 85%

“…2a), annual riverine TP fluxes were positively correlated with precipitation and river discharge (Table 2). Higher precipitation and river discharge enhance erosion and leaching that subsequently increase the fractional export of P inputs by rivers (Borbor-Cordova et al, 2006;Morse and Wollheim, 2014). Eroded sediments are typically enriched with P relative to the bulk soil (up to a factor of five times) due to the preferential removal of fine soil particles having a greater P content (Sharpley et al, 2002).…”

Section: Response Of Riverine Tp Export To Changes In Land-use and Hymentioning

confidence: 99%

“…Calculation of net anthropogenic phosphorus input (NAPI) is a P budgeting approach that sums annual P contributions from atmospheric deposition, fertilizer application, non-food input (i.e., detergent P), seed input, and net import/export in animal feed and human food supplies (Han et al, 2013). The NAPI approach has been successfully applied to many watersheds across Asia (Han et al, 2011b(Han et al, , 2013Chen et al, 2015a), the Americas (David and Gentry, 2000;Borbor-Cordova et al, 2006;Han et al, 2011a;Russell et al, 2008;Sobota et al, 2011), and Europe (Hong et al, 2012). It is a simple yet powerful approach to evaluate net P inputs from anthropogenic sources to terrestrial ecosystems, as well as an effective tool to explain among-watershed or among-year variations in riverine P exports.…”

Section: Introductionmentioning

confidence: 99%

“…It is commonly observed that years with higher precipitation or river discharge export a higher fraction of NAPI via rivers (Borbor-Cordova et al, 2006;Russell et al, 2008;Han et al, 2011a;Sobota et al, 2011;Hong et al, 2012;Chen et al, 2015a), and agricultural watersheds with tile drainage generally export a higher fraction of NAPI (Gentry et al, 2007;Han et al, 2011a;Morse and Wollheim, 2014). In addition, legacy P (i.e., surplus P stored in watershed landscapes that is derived from anthropogenic P inputs in previous years) can be remobilized or recycled after land management change (Meals et al, 2010;Sharpley et al, 2013) or when the degree of landscape P saturation increases after longterm excessive P addition (Kleinman et al, 2011), yielding a considerable P flux to downstream waterbodies Haygarth et al, 2014;Chen et al, 2015a).…”

Section: Introductionmentioning

confidence: 99%

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Factors controlling phosphorus export from agricultural/forest and residential systems to rivers in eastern China, 1980–2011

Chen

Wang

et al. 2016

Journal of Hydrology

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s u m m a r yThis study quantified long-term response of riverine total phosphorus (TP) export to changes in land-use, climate, and net anthropogenic phosphorus inputs to agricultural/forest (NAPI AF ) and residential (NAPI R ) systems for the upper Jiaojiang watershed in eastern China. Annual NAPI AF rose by 73% in 1980-1999 followed by a 41% decline in 2000-2011, while NAPI R continuously increased by 122% over the 1980-2011 period. Land-use showed a 63% increase in developed land area (D%) and a 91% increase in use of efficient drainage systems on agricultural land area (AD%) over the study period. Although no significant trends were observed in annual river discharge or precipitation, the annual number of storm events rose by 90% along with a 34% increase in the coefficient of variation of daily rainfall. In response to changes of NAPI AF , NAPI R , land-use and precipitation patterns, riverine TP flux increased 16.0-fold over the 32-year record. Phosphorus export via erosion and leaching was the dominant pathway for P delivery to rivers. An empirical model incorporating annual NAPI AF , NAPI R , precipitation, D%, and AD% was developed (R 2 = 0.96) for apportioning riverine TP sources and predicting annual riverine TP fluxes. The model estimated that NAPI AF , NAPI R and legacy P sources contributed 19-56%, 16-67% and 13-32% of annual riverine TP flux in 1980-2011, respectively. Compared to reduction of NAPI AF , reduction of NAPI R was predicted to have a greater immediate impact on decreasing riverine TP fluxes. Changes in anthropogenic P input sources (NAPI AF vs. NAPI R ), land-use, and precipitation patterns as well as the legacy P source can amplify P export from landscapes to rivers and should be considered in developing P management strategies to reduce riverine P fluxes.

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Section: Response Of Riverine Tp Export To Changes In Phosphorus Budgetssupporting

confidence: 90%

Section: Fates Of Surplus Phosphorussupporting

confidence: 85%

Section: Response Of Riverine Tp Export To Changes In Land-use and Hymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Factors controlling phosphorus export from agricultural/forest and residential systems to rivers in eastern China, 1980–2011

Chen

Wang

et al. 2016

Journal of Hydrology

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Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador

Muñoz‐Abril

Valle

Alava

et al. 2022

Environmental Toxicology and Chemistry

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We examined how dietary factors recorded by C and N influence Hg uptake in 347 individuals of yellowfin tuna (Thunnus albacares), an important subsistence resource from the Galápagos Marine Reserve (Ecuador) and the Ecuadorian mainland coast in 2015–2016. We found no differences in total Hg (THg) measured in red muscle between the two regions and no seasonal differences, likely due to the age of the fish and slow elimination rates of Hg. Our THg concentrations are comparable to those of other studies in the Pacific (0.20‐9.60 mg/kg wet wt), but a subset of individuals exhibited the highest Hg concentrations yet reported in yellowfin tuna. Mercury isotope values differed between Δ199Hg and δ202Hg in both regions (Δ199Hg = 2.86 ± 0.04‰ vs. Δ199Hg = 2.33 ± 0.07‰), likely related to shifting food webs and differing photochemical processing of Hg prior to entry into the food web. There were significantly lower values of both δ15N and δ13C in tuna from Galápagos Marine Reserve (δ15N: 8.5–14.2‰, δ13C: −18.5 to −16.1‰) compared with those from the Ecuadorian mainland coast (δ15N: 8.3–14.4‰, δ13C: −19.4 to −11.9‰), of which δ13C values suggest spatially constrained movements of tuna. Results from the pooled analysis, without considering region, indicated that variations in δ13C and δ15N values tracked changes of Hg stable isotopes. Our data indicate that the individual tuna we used were resident fish of each region and were heavily influenced by upwellings related to the eastern Pacific oxygen minimum zone and the Humboldt Current System. The isotopes C, N, and Hg reflect foraging behavior mainly on epipelagic prey in shallow waters and that food web shifts drive Hg variations between these populations of tuna. Environ Toxicol Chem 2022;41:2732–2744. © 2022 SETAC

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Transport of nutrients into the southern Gulf of Mexico by the Grijalva–Usumacinta rivers

Castillo-Uzcanga

Carrillo

Jarquín-Sánchez

et al. 2023

Hydrological Processes

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Nutrient transport by rivers strongly influences ecosystem productivity and hypoxia zone formation in coastal areas. In this study, we estimated the transport of nitrogen and phosphorus by the Grijalva and Usumacinta rivers that combined represent the second largest source of fresh water into the Gulf of Mexico. Water samples were collected monthly within an annual cycle at different sites (mainstem and tributaries) in the Lower Grijalva and Usumacinta basins to encompass the seasonal variation in discharge. Nitrogen (total nitrogen, nitrate-N, ammonium-N, and nitrite-N), phosphorus (total phosphorus, soluble reactive phosphorus), and chlorophyll concentrations were determined, and annual loads estimated using the Beale ratio approach. Nutrient and chlorophyll concentrations were greater in the Grijalva than in the Usumacinta River. Stronger seasonal patterns in nutrient concentrations and discharge were identified in the Usumacinta, evincing the flow regulation experimented by the Grijalva. In the Grijalva, higher nutrient concentrations were measured at the De la Sierra and Pichucalco rivers, compared to the regulated Carrizal. TN:TP ratios were greater during the dry season in both rivers, and higher TN:TP occurred in the Usumacinta than in the Grijalva.The Usumacinta showed greater nutrient loads (nitrogen, 26790.6 Â 10 3 kg year À1 ; phosphorus, 3056.9 Â 10 3 kg year À1 ) than the Grijalva (nitrogen 19974.7 Â 10 3 kg year À1 ; phosphorus, 1941.8 Â 10 3 kg year À1 ). However, the Grijalva River showed higher soluble reactive phosphorus and ammonium-N loads and yields than the Usumacinta, likely explained by greater delivery of urban wastewater in the lower Grijalva Basin. The Grijalva-Usumacinta represents an important source of nitrogen compared to other rivers draining into the Gulf of Mexico, even though more disturbed rivers can exceed the phosphorus load. This study can contribute to the modelling of nutrient delivery into the Gulf of Mexico and to better understand the influence of tropical rivers in the formation of coastal hypoxia.

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Nitrogen and phosphorus budgets for a tropical watershed impacted by agricultural land use: Guayas, Ecuador

Cited by 84 publications

References 35 publications

Factors controlling phosphorus export from agricultural/forest and residential systems to rivers in eastern China, 1980–2011

Factors controlling phosphorus export from agricultural/forest and residential systems to rivers in eastern China, 1980–2011

Elevated Mercury Concentrations and Isotope Signatures (N, C, Hg) in Yellowfin Tuna (Thunnus albacares) from the Galápagos Marine Reserve and Waters off Ecuador

Transport of nutrients into the southern Gulf of Mexico by the Grijalva–Usumacinta rivers

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