Manipulating nutrient limitation using modified local soils: A case study at Lake Taihu (China)

Abstract

a b s t r a c tThe effect of geo-engineering materials of chitosan modified local soil (MLS) on nutrient limitation was studied in comparable whole ponds in Lake Taihu in October 2013. After 20 kg MLS were sprayed in the whole water pond (400 m 2 ), the chlorophyll-a (Chl-a) concentration was decreased from 42 to 18 mg L À1 within 2 h and remained below 20 mg L À1 in the following 15 months, while the average Chl-a was 36 mg L À1 in the control pond throughout the experiment. In situ nutrient addition bioassay experiments indicated that the nutrient limitation was shifted from nitrogen (N) and phosphorus (P) co-limitation to P limitation after MLS treatment from October 2013 to March 2014 compared to the control pond. In the cyanobacterial bloom season of June 2014, N and P co-limitation remained and N was the primary limiting nutrient and P was a secondary one in the control pond where phytoplankton biomass showed significant increase by N addition and further increase by N þ P additions, while both N and P became the limiting nutrient for phytoplankton growth where only combined N and P additions showed significant Chl-a stimulation in the treatment pond. In the next summer (June 2014), a cyanobacteria-dominated state still remained in the control pond but chlorophytes, bacillariophytes and cyanophytes distributed equally and submerged vegetation was largely restored in the treatment pond. Meanwhile, the upper limiting concentration of DIN was enhanced from 0.8 to 1.5 mg L À1 and SRP from 0.1 to 0.3 mg L À1 compared to the control pond. This study indicates that nutrient limitation can be manipulated by using MLS technology.

A critical review on control methods for harmful algal blooms

“…Although flocculants or modifiers could have detrimental impacts, the combined used has been shown to reduce the clay loading resulting in overall lower environmental impact (Wang et al . ,b). Notwithstanding, application methods should be carefully considered as cultured fish could be sensitive to these substances.…”

“…The operation principle is similar to Phoslock ® , but with the advantage to use local soil supplemented with a biopolymer as chitosan (Wang et al . ,b). In China, its implementation in the natural environment at mesocosm scale showed a change in microplankton community, with an increase in diversity (multi‐algae coexistence) together with a decrease of nutrients in the water column and diminished release of nutrients from the sediments (Dai et al .…”

“…At larger scale in the same lake, the impact was similar, showing restoration of submerged vegetation (Macrophyte) suggesting that nutrient limitation can be manipulated using the MLS technology and secondarily that ecological recovery can be promoted (Wang et al . ,b). However, successful manipulation of biogeochemical processes requires a comprehensive understanding of physical, chemical and biological conditions, which could lead to contrasting results (Spears et al .…”

Switching Harmful Algal Blooms to Submerged Macrophytes in Shallow Waters Using Geo-engineering Methods: Evidence from a 15N Tracing Study

“…2,3 It is well known that reduction of nutrient concentrations is often insufficient to restore the vegetated clear state even at substantially lower nutrient concentrations where levels than those at when the massive degradation of the vegetation occurred. 4,5 Some studies suggest that improving the submerged macrphytes growing conditionrestoration of clear water canto trigger the growth of submerged macrophytes, which cause the clear state to be self-stabilizing of self-stabilizing in alternativethe to the undesirable situation, thereby recovering the ecosystem resilience. 6,7 However, this is thought to be difficult to achieve in an established algael-dominated bloom waters in where photosynthesis and seed germination in submerged plants are usually suppressed by due to its stable situation including low reduced transparence and low dissolved oxygen.…”

Adsorption Performance on Sediment Nutrients by Different Proportions of Zeolite and Shale Ceramsite (ZSC)

“…The nitrogen adsorbents are mainly zeolite [18] and modified zeolite [11]. The phosphorus adsorbents are modified maifanite [19], modified zeolite [20], modified local soils [5] and so on. But several issues remain: (1) lack of studies on materials absorption of both nitrogen and phosphorus;…”