Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

Abstract

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02-3.20 mg/L for dissolved silicate (Si); 0.06-2.40 mg/L for DIN (NH 4 N + NO 2 N + NO 3 N); 0.03-0.56 mg/L for PO 4 P and 0.22-193.37 μg/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.-23 Mar.; the second one: 23 Mar.-28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO 4 P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO 4 P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space.Daily and bidaily monitoring of Site A and B, representing for high DIN: PO 4 P ratio and low DIN:PO 4 P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.

Phytoplankton variation and its relationship with the environment in Xiangxi Bay in spring after damming of the Three-Gorges, China

“…However, in Xiangxi Bay, nitrogen has been considered to be the primary nutrient limiting phytoplankton growth (Ye et al 2007;Zhou et al 2009). The Xiangxi Bay was subject to serious phosphorus pollution mainly from a large number of phosphorous industry wastewater and domestic sewage ).…”

“…Additionally, the spatial extents and frequency of algal blooms exhibited an increasing trend in last 3 years. Except for some of the earlier studies on algal blooms investigation and water quality assessment (Kuang et al 2004;Zhou et al 2006;Ye et al 2007), there were no studies focusing on spring phytoplankton blooms and its relationship with environment in Xiangxi Bay. However, determining the ongoing changes of environmental factors that primarily affect spring phytoplankton blooms under the given interactions between reservoir formation and river flow is an important first step in monitoring the development while these data can at a later date serve effectively reservoir management strategies.…”

Asynchrony of spring phytoplankton response to temperature driver within a spatial heterogeneity bay of Three-Gorges Reservoir, China

“…A long reservoir-bay can be regarded as the canyon-shaped reservoir without dam which exhibited marked longitudinal gradients . For example, Ye et al (2006Ye et al ( , 2007 analyzed the spatial distribution of nutrient in Xiangxi Bay of Three-Gorge Reservoir (TGR, China), and found that phosphorus increase and nitrogen decrease along longitudinal gradients from the mouth to the headwater. Xu et al (2009a) also illustrated the longitudinal gradients in inorganic suspended particles of Xiangxi Bay, one of non algal absorbing components which influence the underwater light condition for phytoplankton growth.…”

Changes in water types under the regulated mode of water level in Three Gorges Reservoir, China

“…Surprisingly, there have been no algal blooms reported until now in the mainstream of TGR. Many examples of algal blooms from Xiangxi Bay were published in Chinese and international journals (Ye et al, , 2007Wang et al, 2009;Xu et al, 2009cXu et al, , 2010cZhang et al, 2009). For example, daily and weekly observation during spring of the year 2005 showed that algal blooms occurred in the Xiangxi Bay with maximum chlorophyll a of 179.39 mg/L (Ye et al, , 2007.…”

“…The impacts of TGD on ecological processes of water body have caused concern to aquatic ecologists worldwide (Cai and Hu, 2006). Many ecological studies of TGR after the first impoundment have been published in Chinese and international journals, including suspended solids (Xu et al, 2009a), water eutrophication (Cai and Hu, 2006;Xu et al, 2010a), algal blooms (Ye et al, , 2007Xu et al, 2009b,c), phytoplankton (Zeng et al 2006), zooplankton (Xue et al, 2006), and macroinvertebrates (Shao et al, 2008). For example, it was found that water residence time is an important regulatory factor for seasonal dynamics of suspended solids (Xu et al, 2009a), trophic status (Xu et al, 2010a) and water clarity (Xu et al, 2010b) after the first impoundment.…”