Low ratios of silica to dissolved nitrogen supplied to rivers arise from agriculture not reservoirs.
Ecol Lett
; 19(12): 1414-1418, 2016 12.
Article
em En
| MEDLINE
| ID: mdl-27737496
ABSTRACT
Coastal marine systems are greatly altered by toxic marine algae, eutrophication and hypoxia. These problems have been linked to decreased ratios of dissolved silica to inorganic nitrogen (Si DIN) delivered from land. Two mechanisms for this decline under consideration are enhanced nitrogen (N) fertiliser losses from agricultural lands or Si sequestration in reservoirs. Here we examine these mechanisms via nutrient concentrations in impoundments receiving water from 130 watersheds in a landscape representative of the agriculture that often dominates coastal nutrient inputs. Decreased Si DIN was correlated with agriculture, not impoundment. Watersheds with > 60% agricultural land yielded highest DIN, whereas Si was uncorrelated with agricultural intensity. Furthermore, eutrophic lakes were dominated by Cyanobacteria that use little Si, so reservoirs did not diminish Si DIN. Instead, Si DIN increased slightly as reservoir residence time increased. These data suggest that impoundments in agricultural watersheds may enhance the water quality of coastal ecosystems, whereas fertiliser losses are detrimental.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Dióxido de Silício
/
Rios
/
Nitrogênio
Idioma:
En
Revista:
Ecol Lett
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
Estados Unidos