The effect of phosphorus binding clay (Phoslock®) in mitigating cyanobacterial nuisance: a laboratory study on the effects on water quality variables and plankton

This laboratory study examined the lanthanum modified clay Phoslock® for its effectiveness to bind soluble reactive phosphorus (SRP), release of nutrients from this modified clay, its influence on water quality variables (pH, oxygen saturation %, conductivity and turbidity), effects on phytoplankton growth (green alga Scenedesmus obliquus, cyanobacteria Microcystis aeruginosa and Anabaena sp.), and, lastly, its effect on the population growth of the rotifer Brachionus calyciflorus. A clear dose–response for SRP binding by the modified clay was observed. A small amount of ammonium is released from Phoslock®. We found no effect of Phoslock® on pH or oxygen saturation. Conductivity increased with the increasing concentration of Phoslock®. An application of Phoslock® caused a transient increase of turbidity up to 211 NTU. However, due to rapid settlement, turbidity fell below 13 NTU (~1 m Secchi depth), after 6 h. Phoslock® addition caused a reduction in growth of all phytoplankton species tested that we attribute to the combined effects of light limitation, flocculation with the bentonite and binding of SRP to Phoslock®. We estimated the EC50 of Phoslock® on the population growth of rotifer B. calyciflorus to be 0.15 g Phoslock® l-1. Overall, the results of our study indicate Phoslock® seems to be suitable for field applications

Effects of an anionic surfactant (FFD-6) on the energy and information flow between a primary producer (Scenedesmus obliquus) and a consumer (Daphnia magna)

The effects of a commercially available anionic surfactant solution (FFD-6) on growth and morphology of a common green alga (Scenedesmus obliquus) and on survival and clearance rates of the water flea Daphnia magna were studied. The surfactant-solution elicited a morphological response (formation of colonies) in Scenedesmus at concentrations of 10–100 μl l−1 that were far below the No Observed Effect Concentration (NOEC) value of 1,000 μl l−1 for growth inhibition. The NOEC-value of FFD-6 for colony-induction was 3 μl l−1. Daphnia survival was strongly affected by FFD-6, yielding LC50–24h and LC50–48h of 148 and 26 μl l−1, respectively. In addition, clearance rates of Daphnia feeding on unicellular Scenedesmus were inhibited by FFD-6, yielding a 50% inhibition (EC50–1.5h) at 5.2 μl l−1 with a NOEC of 0.5 μl l−1. When Daphnia were offered FFD-6-induced food in which eight-celled colonies (43 × 29 μm) were most abundant, clearance rates (~0.14 ml ind.−1 h−1) were only 25% the rates of animals that were offered non-induced unicellular (15 × 5 μm) Scenedesmus (~0.56 ml ind.−1 h−1). As FFD-6 concentrations in the treated food used in the experiments were far below the NOEC for clearance rate inhibition, it is concluded that the feeding rate depression was caused by the altered morphology of the Scenedesmus moving them out of the feeding window of the daphnids. The surfactant evoked a response in Scenedesmus that is similar to the natural chemically induced defensive reaction against grazers and could disrupt the natural information conveyance between these plankton organisms

The smell of water : grazer-induced colony formation in Scenedesmus

In aquatic systems, the phytoplankton - zooplankton relation is of major importance because it is the first step in the pelagic food chain. It is well known that zooplankton feed with a highly variable success on phytoplankton, primarily owing to algal characteristics such as size, shape, cell wall texture, nutritional quality and toxicity. Algae are present in a broad variety of shapes and may express an enormous variability in their morphology, physiology and behavior depending on environmental variables. Because algae depend on solar energy they have to remain in the upper water layers as long as possible. Moreover, they have to compete with other algae for dissolved nutrients. This means that in an aquatic environment selection pressure exists for small organisms since these have the most efficient uptake of nutrients and light and lowest sinking losses. By contrast, mortality through grazing by an entire assemblage of protozoan and metazoan grazers will exert a strong selection for traits that reduce this mortality through grazing. An effective way to resist grazing is by a dramatic increase in size. However, this confronts the algae with conflicting allometries of selection pressures.Since algae are small relative to their predatory enemies, they may not survive an encounter with a grazer. Therefore, it may be profitable to detect a grazer before they encounter each other in order to elicit a defensive strategy. In a predictable environment temperature and day length could be good predictor of danger. However, in aquatic systems, grazing fluctuates considerably on temporal and spatial scales and chemical cues may be used instead. All organisms exchange constantly chemicals with their environment and those chemicals that are essential in the biology of the grazer and are detectable by the algae may prove potential indicators of danger. They convey information and are referred to as infochemicals. This thesis focuses on the role of infochemicals in the interaction between algae and zooplankton, with emphasis on the Scenedesmus (algae) - Daphnia (waterflea) relation.In the presence of filtered medium from a Daphnia culture, the non-spiny Scenedesmus acutus formed numerous eight-celled colonies (coenobia) (Chapter 2). However, in control populations, i.e. in the absence of Daphnia -infochemical, S. acutus remained unicellular and formed only four-celled colonies when cultures reached stationary phase. The induced colony formation appeared reversible as eight-celled colonies gradually disappeared from the treated populations.A prerequisite for further exploration of the phenomenon of Daphnia -induced colony formation is the development of a reliable biotest (Chapter 3). Inoculum algal density, carbon availability and filter-type are some of the factors that affected the Daphnia -induced colony formation. Analysis of filter extractables revealed that at least two detergents might cause S. acutus to shift rapidly from a completely unicellular population to one dominated with colonies. The production of the Daphnia -infochemical is related to the amount of food processed by the animals. Starved animals or animals fed with ingestible but non-digestible beads were ineffective in inducing colonies. Neither algal homogenates nor auxins and several organic carbon sources have colony inducing activity. The infochemical does seem to originate from the Daphnia -food interaction, or better from the grazer-algal food interaction as several herbivorous zooplankters were able to induce colonies in S. acutus , whereas carnivorous zooplankton and fish were ineffective (Chapter 3). Simple excretion products, such as ammonia and urea alone or in combination with organic carbon sources were ineffective as colony inducing agents (Chapters 3 & 4).Scenedesmus plasticity has, however, not only been shaped by the activity of grazers, but also by other selective forces. Several factors are known that may influence the growth and morphological development in Scenedesmus and among them nutrient availability (Chapter 4) and temperature (Chapter 5) are important ones. In culture, with relatively high algal densities carbon limitation may occur. The availability of inorganic carbon appeared ineffective in inducing colonies, but had a clear effect on cell size. Neither N- nor P-limitation resulted in the formation of numerous, eight-celled coenobia. In general, under nutrient limitation cultures were dominated by unicells. However, despite the limitation, by adding Daphnia water, colonies still could be induced. One of the criticisms on use of artificial growth media is the excessive amount of nutrients in most of them. However, using media of various strengths showed no differences in morphological appearance of S. acutus , both in the absence and presence of Daphnia water.It appears that as long as cell division is not hampered grazer-induced colony formation may occur.Temperature not only affected growth, but also the morphological development in S. acutus (Chapter 5). At low temperatures growth was reduced, but cell- and colony size increased. Under a broad range of temperatures from 9° to 29°C, the addition of Daphnia water significantly increased the proportion of eight-celled coenobia. The smaller size at higher temperature supports the hypothesis of a trade-off between sinking and size.An analysis of potential costs associated with grazer-induced colony formation was initially directed on metabolic costs (Chapter 6). However, no reductions in growth and photosystem II efficiency were detected in induced colonies. Higher sinking losses of induced colonial Scenedesmus populations were measured. Hence, costs may be assigned to enhanced sinking out of the euphotic zone into darker and colder water layers, thereby significantly reducing growth rates. The strategy may, however, not be completely lethal, as Scenedesmus is known to be capable of surviving for prolonged periods on the sediments.One of the prerequisites for interpreting the grazer-induced colony formation as an induced defense is that the response has to be effective in reducing mortality through grazing. In Chapter 7, the grazing success of several zooplankton species, such as the rotifers Keratella and Brachionus and the cladocerans Bosmina , Ceriodaphnia and Daphnia , was analyzed. Food intake was reduced in all smaller grazers, but not in the largest Daphnia species. Moreover, growth of the small Daphnia cucullata was reduced when offered colonial S. acutus . These reductions appeared not the result of an altered biochemical composition of induced colonies.So far, the effect of grazing-associated infochemicals had only been examined for the non-spiny S. acutus . In Chapter 8, 23 different Scenedesmus strains, 9 different other chlorophytes, 2 diatom species and 5 strains of cyanobacteria were investigated. In 35% of the Scenedesmus a positive response to the addition of Daphnia water was observed. Most responding appeared the non-spiny strains, i.e. 64% in contrast to the 4% for spined Scenedesmus . Not only is the trait colony formation only one of the potential defensive traits, it also appeared that the biotest was only suited for examining non-spiny Scenedesmus .The grazer-induced colony formation appeared not to be restricted to the genus Scenedesmus, since two Coelastrum strains were responsive too. Also in the diatom Synedra and the cyanobacterium Microcystis cell size was increased in the presence of Daphnia water. Moreover, the latter showed a tendency to higher toxin levels when cultured in the presence of medium from a Daphnia culture (Chapter 8).Another phenomenon often observed in the presence of live Daphnia , is the aggregation of live cells onto fecal pellets (Chapter 8). These large aggregates will undoubtedly be inedible to grazers and may be an additional process affecting the energy flow from algae to their consumers.In Chapter 9, experiments were performed to evaluate the ability of Daphnia to locate algae by means of chemical cues. No evidence for such a mechanism was detected. However, the animals did seem to avoid water with odors from congeners. Moreover, water from crowded Daphnia cultures had clear effects on growth and reproduction in two Daphnia species and may have an effect on the phytoplankton-grazer interaction.Summarizing the various experiments described in this thesis, the phenomenon of grazer-induced colony formation in Scenedesmus can be interpreted as an inducible defense at the expense of higher sinking losses. The phenomenon is not restricted to Scenedesmus and because of the enormous plasticity in phytoplankton, numerous species may eventually turn out not only to respond to abiotic but to biotic agents as well.</p

Editorial – A critical perspective on geo-engineering for eutrophication management in lakes

Eutrophication is the primary worldwide water quality issue. Reducing excessive external nutrient loading is the most straightforward action in mitigating eutrophication, but lakes, ponds and reservoirs often show little, if any, signs of recovery in the years following external load reduction. This is due to internal cycling of phosphorus (P). Geo-engineering, which we can here define as activities intervening with biogeochemical cycles to control eutrophication in inland waters, represents a promising approach, under appropriate conditions, to reduce P release from bed sediments and cyanobacteria accumulation in surface waters, thereby speeding up recovery. In this overview, we draw on evidence from this special issue Geoengineering in Lakes, and on supporting literature to provide a critical perspective on the approach. We demonstrate that many of the strong P sorbents in the literature will not be applicable in the field because of costs and other constraints. Aluminium and lanthanum modified compounds are among the most effective compounds for targeting P. Flocculants and ballast compounds can be used to sink cyanobacteria, in the short term. We emphasize that the first step in managing eutrophication is a system analysis that will reveal the main water and P flows and the biological structure of the waterbody. These site specific traits can be significant confounding factors dictating successful eutrophication management. Geo-engineering techniques, considered collectively, as part of a tool kit, may ensure successful management of eutrophication through a range of target effects. In addition, novel developments in modified zeolites offer simultaneous P and nitrogen control. To facilitate research and reduce the delay from concept to market a multi-national centre of excellence is required

Duikers in de mist : wetenschappelijk onderzoek naar de mate van doorzicht rondom onderwaterhuis 'Aquavilla' in een diepe duikplas

Veiligheid staat bij Duikteam De Kaaiman hoog in het vaandel. Duiken in troebel water kan gevaarlijk zijn en is dus ongewenst. Ook verhoogt helder water het duikgenot. In het meer de Berendonck bij Wijchen, de vaste duikstek van De Kaaiman, ligt op een diepte van 17 meter een onderwaterhuis. Vooral rondom dit huis is sprake van slecht zicht. Waardoor komt dit en wat is er aan te doen

Case study on the efficacy of a lanthanum-enriched clay (Phoslock®) in controlling eutrophication in Lake Het Groene Eiland (The Netherlands)

Lake Het Groene Eiland was created in the beginning of 2008 by construction of dikes for isolating it from the surrounding 220-ha water body. This so-called claustrum of 5 ha was treated using lanthanum-modified clay (Phoslock®) to control eutrophication and mitigate cyanobacterial nuisance. Cyanobacteria chlorophyll-a were significantly lower in the claustrum than those in the reference water body, where a massive bloom developed in summer, 2008. However, PO4-P and TP did not statistically differ in these two waters. TN and NO3-N were significantly lower in the claustrum, where dense submerged macrophytes beds developed. Lanthanum concentrations were elevated after the applications of the modified clay in the claustrum, but filterable lanthanum dropped rapidly below the Dutch standard of 10.1 μg l−1. During winter, dozens of Canada geese resided at the claustrum. Geese droppings contained an average of 2 mg PO4-P g−1 dry weight and 12 mg NH3-N g−1 dry weight and might present a growing source of nutrients to the water. Constructing the claustrum enabled unrestricted bathing in subsequent three summers, as no swimming bans had to be issued due to cyanobacteria blooms. However, the role of the modified clay in this positive outcome remains unclear, and longevity of the measures questionable.

Resuspensie, sedimentatie en lichtklimaat in de Breukeleveense Plas.

Opwerveling van slib kan in ondiepe Nederlandse oppervlaktewateren een aanzienlijke bijdrage leveren aan de uitdoving van het licht onder water. In 1989 werd gepoogd om door Actief Biologisch Beheer, door verwijdering van een groot deel van de planktivore en benthivore visstand, het doorzicht in de Breukeleveense Bias te vergroten. Deze ingreep gaf echter geen verbetering in het onder water lichtklimaat te zien. Als één van de belangrijkste oorzaken voor het uitblijven van succes wordt de door de wind veroorzaakte opwerveling van bodemslib gezien. Deze studie beschrijft het onder water lichtklimaat in de plas. Het onderzoek was gericht op de bijdrage van verschillende componenten en de invloed van wind op de uitdoving van licht en de vermindering van het doorzicht. De extinctiecoëfficiënten en het doorzicht zijn geschat met behulp van het model UITZICHT. Met dit model werd inzicht verkregen in de bijdrage van verschillende componenten aan de extinctie en het doorzicht. In de plas blijken algen (ca. 50%) en detritus (ca. 25%) in hoge mate verantwoordelijk voor de uitdoving van licht. Met het model DYNHX kon worden afgeleid wat de bijdrage van geresuspendeerd bodemslib aan de extinctie en de afname van het doorzicht is. In het slibrijke zuidwesten van de plas is de bijdrage aan de extinctie gemiddeld 25% resulterend in een afname van het doorzicht van gemiddeld 0,44 tot 0,30 m. In het meer zanderige noordoosten is de bijdrage van resuspensie aan de extinctie gemiddeld 17%, het doorzicht wordt hierdoor gereduceerd van gemiddeld 0,41 tot 0,32 m. In perioden met hevige wind kunnen de bijdragen van resuspensie aan de extinctie oplopen tot 72% in het zuidwesten en tot 44°/o in het noordoosten van de plas. Tijdens deze perioden blijkt het doorzicht gereduceerd te worden tot 0,13 m in het zuidwesten en tot 0,22 m in het noordoosten van de plas. Voor een verbetering van het doorzicht zullen naast reductie van de planktivore en benthivore visstand aanvullende maatregelen voor de reductie van de slibopwerveling nodig zijn aangezien baggeren, vanwege de extreem hoge kosten, geen reële oplossing blijkt

Importance of nutrient competition and allelopathic effects in suppression of the green alga. Scenedesmus obliquus by the macrophytes Chara, Elodea and Myriophyllum

Possible allelopathic effects of substances released from the macrophytes Chara globularis, Elodea canadensis, Myriophyllum spicatum on the common green alga Scenedesmus obliquus were tested in the laboratory with plastic plants and untreated medium as controls. A two-phase approach was used in which first the effects of physical presence of plants was studied (phase I) followed by the effects of plant culture filtrates (phase II). In the presence of plastic plants growth was reduced only marginally, but strong growth inhibition of Scenedesmus occurred in the physical presence of all macrophytes. In contrast, filtrates from Chara had no growth inhibitory effect on Scenedesmus. Myriophyllum filtrate reduced particle-based growth rate by 7% compared to filtration controls, while Elodea culture filtrate reduced volume-based growth by 12%, chlorophyll-based growth by 28% and particle-based growth by 15%. Photosystem II-efficiency of Scenedesmus was reduced in all three macrophyte treatments in phase I, but not in filtrates from macrophyte cultures (phase II). Thus, while enzyme activity or other physiological aspects may have been affected, the current study yielded no proof for allelopathically active compounds being directed at photosynthesis. Mean particle volume (MPV) of Scenedesmus was not influenced by macrophyte exudates and cultures remained dominated by unicells. The strong growth inhibitory effects found for Scenedesmus in the physical presence of macrophytes, but not in plastic controls, and no or weaker response in nutrient-enriched filtrates, suggest nutrient competition was a more powerful driving factor than allelochemicals. However, the experimental design does not exclude disappearance of allelochemicals during the filtration process

Evaluation of a Commercial Enzyme Linked Immunosorbent Assay (ELISA) for the Determination of the Neurotoxin BMAA in Surface Waters

The neurotoxin ß-N-methylamino-L-alanine (BMAA) is suspected to play a role in Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Because BMAA seems to be produced by cyanobacteria, surface waters are screened for BMAA. However, reliable analysis of BMAA requires specialized and expensive equipment. In 2012, a commercial enzyme-linked immunosorbent assay (ELISA) for determination of BMAA in surface waters was released. This kit could enable fast and relatively cheap screening of surface waters for BMAA. The objective of this study was to determine whether the BMAA ELISA kit was suitable for the determination of BMAA concentrations in surface waters. We hypothesised that the recovery of spiked samples was close to 100% and that the results of unspiked sample analysis were comparable between ELISA and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. However, we found that recovery was higher than 100% in most spiked samples, highest determined recovery was over 400%. Furthermore, the ELISA gave a positive signal for nearly each tested sample while no BMAA could be detected by LC-MS/MS. We therefore conclude that in its current state, the kit is not suitable for screening surface waters for BMAA

Combined and single effects of pesticide carbaryl and toxic Microcystis aeruginosa on the life history of Daphnia pulicaria

The combined influence of a pesticide (carbaryl) and a cyanotoxin (microcystin LR) on the life history of Daphnia pulicaria was investigated. At the beginning of the experiments animals were pulse exposed to carbaryl for 24 h and microcystins were delivered bound in Microcystis’ cells at different, sub-lethal concentrations (chronic exposure). In order to determine the actual carbaryl concentrations in the water LC–MS/MS was used. For analyses of the cyanotoxin concentration in Daphnia’s body enzyme-linked immunosorbent assay (ELISA) was used. Individual daphnids were cultured in a flow-through system under constant light (16 h of light: 8 h of dark), temperature (20°C), and food conditions (Scenedesmus obliquus, 1 mg of C l−1). The results showed that in the treatments with carbaryl egg numbers per female did not differ significantly from controls, but the mortality of newborns increased significantly. Increasing microcystin concentrations significantly delayed maturation, reduced size at first reproduction, number of eggs, and newborns. The interaction between carbaryl and Microcystis was highly significant. Animals matured later and at a smaller size than in controls. The number of eggs per female was reduced as well. Moreover, combined stressors caused frequent premature delivery of offspring with body deformations such as dented carapax or an undeveloped heart. This effect is concluded to be synergistic and could not be predicted from the effects of the single stressors.