Temporal and spatial trends in water quality of Lake Taihu, China: analysis from a north to mid-lake transect, 1991–2011

Abstract

Interpretations of state and trends in lake water quality are generally based on measurements from one or more stations that are considered representative of the response of the lake ecosystem. The objective of this study is to examine how these interpretations may be influenced by station location in a large lake. We addressed this by analyzing trends in water quality variables collected monthly from eight monitoring stations along a transect from the central lake to the north in Lake Taihu (area about 2,338 km(2)), China, from October 1991 to December 2011. The parameters examined included chlorophyll a (Chl a), total nitrogen (TN), and total phosphorus (TP) concentrations, and Secchi disk depth (SD). The individual variables were increasingly poorly correlated among stations along the transect from the central lake to the north, particularly for Chl a and TP. The timing of peaks in individual variables was also dependent on station location, with spectral analysis revealing a peak at annual frequency for the central lake station but absence of, or much reduced signal, at this frequency for the near-shore northern station. Percentage annual change values for each of the four variables also varied with station and indicated general improvement in water quality at northern stations, particularly for TN, but little change or decline at central lake stations. Sediment resuspension and tributary nutrient loads were considered to be responsible for some of the variability among stations. Our results indicate that temporal trends in water quality may be station specific in large lakes and that calculated whole-lake trophic status trends or responses to management actions may be specific to the station(s) selected for monitoring and analysis. These results have important implications for efficient design of monitoring programs that are intended to integrate the natural spatial variability of large lakes.

Spatiotemporal Variability in the Water Quality of Poyang Lake and Its Associated Responses to Hydrological Conditions

“…Therefore, the inter-annual variations of water quality were under the dual influence of hydrological conditions (e.g., water level, discharge) and sewage flowed into the lake. Eutrophication remains one of the most pervasive environmental problems in lakes [23]. The nutrient indicators considered in the present study all showed significant seasonal variations.…”

“…Dilution was identified as the controlling factor that drives the seasonal variability in the water quality of Poyang Lake. Eutrophication remains one of the most pervasive environmental problems in lakes [23]. The nutrient indicators considered in the present study all showed significant seasonal variations.…”

“…In reference to the study of Akyuz et al [23], we examined the seasonal variations at each sampling site using a relative seasonal average (RM se,s,p ):…”

Ecotoxicological assessment of flocculant modified soil for lake restoration using an integrated biotic toxicity index

“…Over the past several decades, harmful algae blooms (HABs) have frequently occurred worldwide, causing serious ecological and economic impacts to aquatic ecosystems and human health (Akyuz et al, 2014;Paerl and Huisman, 2008). Several chemical (Burson et al, 2014;Fan et al, 2013), mechanical and biological techniques (Kim et al, 2007;Nan et al, 2008) have been developed to reduce these impacts.…”

Interactive monitoring in reservoirs using NUSwan – preliminary field results

“…To better understand, monitor, and manage the water resources, researchers are required to measure the water quality parameters regularly at diverse locations over different periods (Atkinson & Mabe 2006;Carraro et al 2012;Zhang et al 2015). Long term site studies (Akyuz et al 2014;Su et al 2015;Wang et al 2015;Yan et al 2016) and satellite imagery (Nellis et al 1998;Bergamino et al 2010;Pu et al 2017) have shown evidence of spatiotemporal dynamics in water quality variables in lake environments. Human activities (Warnken & Buckley 2004;Krogh et al 2009), urbanisation and land use (Ahearn et al 2005;Almeida et al 2007;Zhao et al 2013;Kändler et al 2017) have been reported to affect water quality in catchments and rivers.…”