Phytoplankton community responses in a shallow lake following lanthanum-bentonite application

Abstract

Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. The release of phosphorus (P) from bed sediments to the overlying water can delay , 2012;Spears et al., 2012;Sharpley et al., 2014). (over 3 days, as slurry from a pontoon) to control internal P loading, in an effort to Loch Flemington (Table 1) and likewise, being shallow, does not thermally stratify. 189This site also has sufficient data available and satisfies the BACI requirements for 190 the differences between sites to be relatively constant in the before period and not 191 subject to localised long-term random influences (e.g. large storms) during the study. 192The phytoplankton community in Loch Leven is, primarily, P limited and the loch has and cyanobacterial bloom intensity (using cyanobacteria biovolume) (see also , 1986). The null hypothesis is that there is no change in the difference in 262 the two time periods i.e. no effect of the La-bentonite application and where a 263 significant difference in the differences in the two time periods is detected at the 5% evidence that a large-scale driver i.e. weather, was influencing changes at both sites. 422Hence the increase in annual mean TP concentration may have been due to 423 enhanced internal P loading, associated with the drier and warmer than average 424 summer of 2013, when compared across the five year monitoring period (Table 4) essential and could potentially be discerned using long-term monitoring data. 441The phytoplankton compositional metric (PTI EQR) showed a sustained Implications of the results for future eutrophication management in lakes 468We have demonstrated the use of a BACI approach for detecting responses in shallow lake ecosystems (Hosper & Jagtman, 1990;Søndergaard et al., 2000; 532 Wichelen et al., 2007;Mehner et al., 2002 Mehner et al., & 2008 Duras & Dziaman, 2010). 533Controlling catchment-derived nutrient loading is a prerequisite for lasting lake 534 restoration efforts, otherwise internal stocks of nutrients will be replenished and 535 recovery periods protracted through their sediment release (Cooke et al., 2005). 536We have presented the first comprehensive assessment, using a BACI 546• This initial cyanobacterial response was not sustained beyond post-application 547 year two, implying a short lived reduction in internal P loading as a result of capping 548 sediment release. 549• The resumption in annual mean TP concentration, suggests that the La-bentonite 550 application was insufficient to control internal P loading for longer than two years. 551• Continual improvements in the phytoplankton compositional and abundance 552 metrics, not observed at the control site, may reflect a response to the sustained 553 reduction in annual mean FRP concentration following La-bentonite application. 554• The cyanobacterial bloom intensity metric is sensitive to inter-a...

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

“…This result contrasts with some studies that showed a rapid decline in phytoplankton abundance, yet they combined a coagulant with LMB as ballast, effectively clearing the water column [20,65]. Other studies used only LMB and also reported a decline or control of cyanobacteria [61], or a short-lived positive effect [19], but no information on the speed of the response, while in another study a clear lag period of several months was observed [66]. In our study, the increase in cyanobacteria in controls and sole LMB treatments after one month does not seem to be caused by recruitment of settled cyanobacteria as a similar phenomenon should have then occurred in the dredged enclosures.…”

“…Therefore, primary production is a more probable explanation for the observed increase in pH in these treatments. This is unexpected as sufficient reduction of SRP by LMB can strongly hamper algal growth, as evidenced in laboratory experiments [15] and whole-lake applications [19,61], yet there are also reports that algal growth was not inhibited after LMB application [62]. Both an insufficient reduction in SRP and potential luxury consumption of P by the cyanobacteria are possible explanations for continued primary production.…”

Assessing the impacts of phosphorus inactive clay on phosphorus release control and phytoplankton community structure in eutrophic lakes

“…Loch Flemington, which is explained by the less competitive advantage of cyanobacteria under reduced phosphorus conditions (Lang et al, 2016). Similar results are also found in shallow reservoir in California and marine cyanobacteria removal by polyaluminium chloride modified clay (Yu et al, 1995).…”

“…Most of the previous research on phosphorus inactive materials has highlighted the performance of phosphorus fixation or immobilization Wagenhoff et al, 2012). Recently, their impacts on phytoplankton abundance and community structure are getting more attentions to be considered in eutrophic water restoration actions Lang et al, 2016;. Although our study aims to answer these questions, the laboratory-scale experiment cannot simulate the field reality where the phosphorus cycle and phytoplankton community are affected by numerous environmental factors .…”

An Enhanced System with Macrophytes and Polyurethane Sponge as an Eco-Technology for Restoring Eutrophic Water: A Pilot Test

“…It was hypothesized that the phosphorus-sensitive cyanobacteria were significantly affected by low phosphorus pressure [42]. Lang et al [43] and Su et al [44] reported that the number of cyanobacteria decreased due to the less competitive advantage of cyanobacteria under reduced phosphorus conditions after the removal of phosphorus in shallow water. In this study, the reduction of cyanobacteria was also more sensitive than Chlorophyta (Figure 4).…”