Importance Of Nutrient Loading Research Articles

Colonial nesting waterbirds as vectors of nutrients to Lake Lesser Prespa (Greece)

ABSTRACT The nutrients imported by breeding waterbirds should be considered when identifying the main sources of nutrient input to lakes. Lake Lesser Prespa (Greece), including the adjacent Vromolimni pond, hosts numerous protected waterbirds that nest in densely populated colonies across the reedbeds. The accelerated eutrophication of the lake in recent years has been of increasing concern. In addition to likely large sources of nutrients (i.e., anthropogenic activities, especially agriculture), nutrient input via waterbird excrement may further trigger eutrophication. We estimated the annual phosphorus (P) and nitrogen (N) input by the most abundant colonial-nesting waterbirds (great white pelican, Dalmatian pelican, great cormorant, and pygmy cormorant) into the lake and investigated their influence on water and sediment quality. Near the waterbird colonies, soluble nutrient concentrations in the lake sediments were higher, and chlorophyll measurements indicated higher algal growth near these sites in summer. Stable isotope analysis suggests that near the colonies, waterbirds are responsible for nutrient loadings that affect the lake sediment. The estimated N and P nutrient input into the lake by both pelican and cormorant species is at least 1243 and 1649 kg/yr, respectively. On a landscape scale, this level of loading could be of minor importance for the lake because N and P can reach 32.8 (SD 9.3) and 38.9 (5.8) mg/m2 per year, respectively. Locally, however, this level of loading might induce cyanobacterial blooms, illustrated by the analysis of isolated Vromolimni pond near the lake. Our findings emphasize the likely importance of nutrient loading by waterbirds for the lake system.

Importance of nutrient loading and irrigation in gross primary productivity trends in India

Investigating the effects of various environmental factors on gross primary productivity (GPP) is crucial for quantifying the carbon exchange between the atmosphere and the terrestrial vegetation for managing climate change. Although it is well known that various natural and anthropogenic factors (e.g., climate change, agricultural activities, and atmospheric CO2 concentration change) can alter GPP, their relative influences are not clearly understood in every region. In this study, we consider several factors and investigate their roles in increasing the GPP in large parts of India. We considered about three decades (1980s to late 2000s) of GPP data and use a regression based systematic approach to find out the most likely cause explaining the trends in India. This study suggests that the common suspects like CO2 and climate may have limited influence on the GPP trends in India when compared to anthropogenic influences. Our results instead support the notion that GPP trends in India are mainly shaped by agricultural activities through nutrient loading (R2=0.68) and irrigation (R2=0.1). Overall, our study reveals the potential of agricultural activities in altering the carbon budget of a region.