Land use controls Kenyan riverine nitrate discharge into Lake Victoria – evidence from Nyando, Nzoia and Sondu Miriu river catchments

Nyilitya, Benjamin; Mureithi, Stephen Mwangi; Boeckx, Pascal

doi:10.1080/10256016.2020.1724999

Cited by 15 publications

(3 citation statements)

References 43 publications

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“…The LVB has experienced a rapid decline in biodiversity, with up to 76% of endemic species threatened with extinction, yet there is a dearth of basic information on the distribution and status of many freshwater species (Sayer et al, 2018a,b). Unsustainable changes in land use that significantly influence ecosystem structure and functioning (Lambin et al, 2003;Turner et al, 2003;De Groot et al, 2010) have impacted river catchments (Ochola, 2006;Odada et al, 2009;Masese et al, 2013;van Soesbergen et al, 2019;Nyilitya et al, 2020), affecting the distribution of fish species in river networks within the LVB (Achieng et al, 2020). Previous studies on the impact of human activities on riverine fish species distribution and biological characteristics within the LVB focused on lower reaches of the basin or were limited to specific rivers (Whitehead, 1959;Corbet, 1961;Masese et al, 2020a).…”

Section: Introductionmentioning

confidence: 99%

Assessment of the Ecological Health of Afrotropical Rivers Using Fish Assemblages: A Case Study of Selected Rivers in the Lake Victoria Basin, Kenya

Achieng¹,

Masese²,

Coffey³

et al. 2021

Front. Water

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Streams and rivers are globally threatened ecosystems because of increasing levels of exploitation, habitat degradation and other anthropogenic pressures. In the Lake Victoria Basin (LVB) in East Africa, these threats are mostly caused by unsustainable land use; however, the monitoring of ecological integrity of river systems has been hampered by a lack of locally developed indices. This study assessed the health of four rivers (Nzoia, Nyando, Sondu–Miriu and Mara) on the Kenyan side of the LVB using physicochemical water quality parameters and a fish-based index of biotic integrity (IBI). Fish tolerance ranking was derived from principal component analysis of water quality parameters, and the concept of niche breadth (NB). The relationship between fish species and water quality parameters was examined with canonical correspondence analysis, whereas community metrics and stressors were evaluated through Pearson network correlation analysis. Fish species richness, trophic structures, taxonomic composition and species tolerance were used to generate the metrics for fish-based IBI. NB showed that most of the fish species were moderately tolerant to poor water. Moderately tolerant and intolerant fish species were negatively correlated with a high level of organic loading in the Mara River. Fish-based IBI scores for the rivers ranged from 26 to 34, with Sondu–Miriu scoring the lowest. Our results show that the cumulative effect of stressors can adequately rank fish species tolerance according to the disturbance gradients and further develop regional metrics to assess river health. Despite the fact that fish communities are declining, continual management and enforcement of environmental regulations are important, with conservation and management of headwaters and low-order streams being essential while they are still species rich.

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Section: Introductionmentioning

confidence: 99%

Assessment of the Ecological Health of Afrotropical Rivers Using Fish Assemblages: A Case Study of Selected Rivers in the Lake Victoria Basin, Kenya

Achieng¹,

Masese²,

Coffey³

et al. 2021

Front. Water

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“…Samples analyzed for δ 15 N and δ 18 O in

{\text{NO}}_{3}^{&#x02010;}

were filtered in situ with 25 mm diameter and 0.45‐μm pore sized disposable filter devices (0.45 μm pore size, 25 mm diameter, GD/X, Whatman), and then frozen and stored in PET centrifuge tubes (15 mL, Sterile, Corning), at 0–4 °C, before analysis. Nitrogen and oxygen isotopes of

{\text{NO}}_{3}^{&#x02010;}

were measured using the “Bacterial Denitrification” method (McIlvin & Casciotti, 2011; Weigand et al, 2016), which simultaneously determined the δ 15 N and δ 18 O in N 2 O that was converted from

{\text{NO}}_{3}^{&#x02010;}

by denitrifying bacteria without N 2 O reductase (Nyilitya et al, 2020). The δ 15 N and δ 18 O in the generated N 2 O were analyzed by a trace gas preparation unit (Precon) coupled with isotope ratio mass spectrometry (IRMS, MAT 253, ThermoFisher).…”

Section: Methodsmentioning

confidence: 99%

Isotopic source identification of nitrogen pollution in the Pi River in Chengdu

Ding

Shi²,

Ouyang³

et al. 2022

Integr Envir Assess & Manag

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This study used stable isotope (δ 15 N-NO 3 − and δ 18 O-NO 3 − ) ratios, modeled by means of a Bayesian stable isotope analysis in R (SIAR) approach, to identify nitrate sources in the Pi River, which flows through the megacity Chengdu. The goal was to determine where management resources should be applied to reduce nitrogen pollution. Results revealed that NO 3 − was the primary nitrogen species throughout the study area; that it originated in manure and sewage, as well as nitrification of fertilizer and soil nitrogen; and that the nitrogen in the main stream came primarily from the tributaries. Notably, the nitrogen concentration in the tributaries exhibited no evident seasonal variations, further demonstrating that its source was intensive anthropogenic activity. Results of Bayesian model (SIAR) estimation indicated that manure and sewage were the dominant nitrate contributors in the watershed and that the nitrate concentration decreased from 54.19% to 39.57% in response to water treatment. These results empirically demonstrate that the methodology described in this work can be used effectively in catchments affected by intensive anthropogenic activity to determine where management resources should be applied to reduce nitrogen pollution.

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“…Резултатите показват, че концентрациите на повечето йони във водоносния хоризонт имат широки пространствено-времеви вариации и са податливи на влияния на околната среда и антропогенното натоварване от земеделска дейност (Liu еt al., 2022). Проучвания показват, че върху състава и хидрохимичните характеристики на водите оказват значително влияние и начините на земеползване, където се установяват съществени разлики в химичния състав на подпочвените води при различните земеделски площи, пасищни площи и естественият ландшафт (Guo et al, 2015;Nobrega et al, 2018;Zhang et al, 2019;Nyilitya et al, 2020;Ijioma 2021).…”

Section: резултати и обсъжданеunclassified

Diffuse pollution sources of groundwater in an intensive agricultural area in Southern Bulgaria

Simeonova

2024

BJCS

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The monitoring was conducted of groundwater and surface water in the period of 2018-2019 year, on Tsalapitsa village, near city of Plovdiv on Аlluvial-meadow soil (Fluvisol). In the scheme of study were included different land use, which reflect the great variety from loading in agroecosystems under agricultural activities - orchards, vineyards, rice fields, fields, where are grown cereals and intensive crops (diffuse or nonpoint sources). Water samples from wells in the pilot survey site were taken twice a year. It was found that the waters from wells under arable lands were characterized in most cases by alkaline reaction and content of chemical elements under or near to the maximum permissible concentration for drinking water. It was established that most of the studied elements are influenced by anthropogenic load and different land use, especially when growing vegetables. Data show that the nitrate nitrogen content in the shallow groundwater varies in a wide range, depending on the location of the studied wells. It was found that change in the nitrate concentrations depending on the land use is in the following order - vegetable crops > rice fields > arable fields > orchards etc. It‘s necessary conducting long-term monitoring to understand the dynamics and transformation of nitrogen in waters and the ongoing complex biochemical processes in the agro-ecosystem, especially in vulnerable areas with soils that are light in mechanical composition, shallow groundwater and with intensive agricultural activity.

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Land use controls Kenyan riverine nitrate discharge into Lake Victoria – evidence from Nyando, Nzoia and Sondu Miriu river catchments

Cited by 15 publications

References 43 publications

Assessment of the Ecological Health of Afrotropical Rivers Using Fish Assemblages: A Case Study of Selected Rivers in the Lake Victoria Basin, Kenya

Assessment of the Ecological Health of Afrotropical Rivers Using Fish Assemblages: A Case Study of Selected Rivers in the Lake Victoria Basin, Kenya

Isotopic source identification of nitrogen pollution in the Pi River in Chengdu

Diffuse pollution sources of groundwater in an intensive agricultural area in Southern Bulgaria

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