Effects of the novel "Flock & Lock" lake restoration technique on Daphnia in Lake Rauwbraken (The Netherlands)
Oosterhout, J.F.X. ; Lürling, M.F.L.L.W. - \ 2011
Journal of Plankton Research 33 (2011)2. - ISSN 0142-7873 - p. 255 - 263.
eutrophic hardwater lakes/ - suspended clay - rare-earth - magna - growth - water - reproduction - survival - ca(oh)(2) - toxicity
We combined a low-dose flocculent (polyaluminiumchloride) with a lanthanum-enriched benthonite clay (Phoslock®) into a novel restoration technique “Flock & Lock”. This treatment was first applied in April 2008 to Lake Rauwbraken, where it stripped all phosphorus (P) from the water column and strongly reduced P-release from the sediment. The treatment had a strong positive effect on water quality, i.e. filamentous cyanobacteria were removed, chlorophyll-a concentration dropped to very low levels of 2 µg L-1, however aluminium, lanthanum and suspended clay concentrations were at least temporally strongly elevated. Following the treatment, Daphnia galeata disappeared for 3 months from the water column within 1 week after application; this phenomenon was not observed in similar periods during 2 years before (2006, 2007) and 1 year after the application (2009). From our field observation and additional grazing (comparing the effects of flocculent, clay and combination of both) and survival experiments (food deprivation), we conclude that the disappearance of D. galeata from Lake Rauwbraken may have been caused by the combination of the physical effects due to flocks, grazing inhibition by flocks and clay, very low food concentrations and absence of predation refuge. However, effects were temporary and Daphnia recovered from the treatment.
Effects of lanthanum and lanthanum-modified clay on growth, survival and reproduction of Daphnia magna
Lürling, M.F.L.L.W. ; Tolman, Y. - \ 2010
Water Research 44 (2010)1. - ISSN 0043-1354 - p. 309 - 319.
waterkwaliteit - meren - klei - eutrofiëring - daphnia magna - lanthaan - zeldzame aardelementen - fosfor - aquatische ecologie - waterzuivering - water quality - lakes - clay - eutrophication - daphnia magna - lanthanum - rare earth elements - phosphorus - aquatic ecology - water treatment - phosphorus binding clay - rare-earth-elements - microcystis-aeruginosa - cyanobacterial toxins - suspended clay - waters - blooms - phosphate
The novel lanthanum-modified clay water treatment technology (Phoslock) seems very promising in remediation of eutrophied waters. Phoslock is highly efficient in stripping dissolved phosphorous from the water column and in intercepting phosphorous released from the sediments. The active phosphorous-sorbent in Phoslock is the Rare Earth Element lanthanum. The purpose of this study was: 1) to establish a dose response relationship between Phoslock and the growth of Daphnia magna, 2) to determine the amount of lanthanum released from Phoslock, and 3) to test the effects of lanthanum on life-history characteristics of D. magna in artificial P-free and P-containing medium.
The novel lanthanum-modified clay water treatment technology (Phoslock (R)) seems very promising in remediation of eutrophied waters. Phoslock (R) is highly efficient in stripping dissolved phosphorous from the water column and in intercepting phosphorous released from the sediments. The active phosphorous-sorbent in Phoslock (R) is the Rare Earth Element lanthanum. A leachate experiment revealed that lanthanum could be released from the clay, but only in minute quantities of 0.13-2.13 mu g l(-1) for a worst-case Phoslock (R) dosage of 250 mg l(-1). A life-history experiment with the zooplankton grazer Daphnia magna revealed that lanthanum, up to the 1000 mu g l(-1) tested, had no toxic effect on the animals, but only in medium without phosphorous. In the presence of phosphorous, rhabdophane (LaPO4 center dot nH(2)O) formation resulted in significant precipitation of the food algae and consequently affected life-history traits. With increasing amounts of lanthanum, in the presence of phosphate, animals remained smaller, matured later, and reproduced less, resulting in lower population growth rates. Growth rates were not affected at 33 mu g La l(-1), but were 6% and 7% lower at 100 and 330 mu g l(-1), respectively, and 20% lower at 1000 mu g l(-1). A juvenile growth assay with Phoslock (R) tested in the range 0-5000 mg l(-1), yielded EC50 (NOEC) values of 871 (100) and 1557 (500) mg Phoslock (R) l(-1) for weight and length based growth rates, respectively. The results of this study show that no major detrimental effects on Daphnia are to be expected from Phoslock (R) or its active ingredient lanthanum when applied in eutrophication control. (C) 2009 Elsevier Ltd. All rights reserved.
Temporal and spatial distribution of microcrustacean zooplankton in relation to turbidity and other environmental factors in a large tropical lake (L. Tana, Ethiopia)
Dejen, E. ; Vijverberg, J. ; Nagelkerke, L.A.J. ; Sibbing, F.A. - \ 2004
Hydrobiologia 513 (2004)1-3. - ISSN 0018-8158 - p. 39 - 49.
barbs barbus-humilis - aquatic organisms - suspended clay - population-dynamics - community structure - reservoir - reproduction - cladocerans - abundance - dispersal
The spatial and seasonal distribution of microcrustacean zooplankton of Lake Tana (Ethiopia) was monthly studied for 2 years. Concurrently, various environmental parameters were measured and related to zooplankton distribution. Canonical Correspondence Analysis (CCA) was used to estimate the influence of abiotic factors and chlorophyll a content in structuring the zooplankton assemblage. Among the environmental factors, zooplankton abundance correlated most strongly with turbidity. Turbidity was negatively correlated with species abundance, especially for Daphnia spp. and to the least extent for Diaphanosoma spp. Analysis of variance (ANOVA) was used to determine spatial (littoral, sublittoral and pelagic zone) and temporal (four seasons) variation in zooplankton abundance. We observed significant temporal differences in zooplankton abundance, with highest densities during dry season (November-April). Only cladocerans showed significant differences in habitat use (highest densities in the sublittoral zone).