Blauwalgen binnen het Kennis voor Klimaat programma

Korte beschrijving van de inventarisatie van cyanotoxines die binnen het Kennis voor Klimaat Programma uitgevoerd gaat worden in Nederlandse oppervlaktewateren, om een indruk te krijgen welke toxines waar en onder welke omstandigheden voorkomen

Assessment of changes in potential nutrient limitation in an impounded river after application of lanthanum-modified bentonite

With the advent of phosphorus (P)-adsorbent materials and techniques to address eutrophication in aquatic systems, there is a need to develop interpretive techniques to rapidly assess changes in potential nutrient limitation. In a trial application of the P-adsorbent, lanthanum-modified bentonite (LMB) to an impounded section of the Canning River, Western Australia, a combination of potential P, nitrogen (N) and silicon (Si) nutrient limitation diagrams based on dissolved molar nutrient ratios and actual dissolved nutrient concentrations have been used to interpret trial outcomes. Application of LMB resulted in rapid and effective removal of filterable reactive P (FRP) from the water column and also effectively intercepted FRP released from bottom sediments until the advent of a major unseasonal flood event. A shift from potential N-limitation to potential P-limitation also occurred in surface waters. In the absence of other factors, the reduction in FRP was likely to be sufficient to induce actual nutrient limitation of phytoplankton growth. The outcomes of this experiment underpins the concept that, where possible in the short-term, in managing eutrophication the focus should not be on the limiting nutrient under eutrophic conditions (here N), but the one that can be made limiting most rapidly and cost-effectively (P)

Praktijkproeven blauwalgenbestrijding in Noord-Brabant

Overlast door blauwalgenbloei is een hardnekkig en veel voorkomend waterkwaliteitsprobleem. Het is niet alleen hinderlijk omdat het vaak in de woonomgeving of in zwemplassen voorkomt, maar er zijn ook risico’s voor dier- en volksgezondheid aan verbonden. Structurele bestrijding van blauwalgen blijkt in de praktijk een lastige opgave. Veel van de uitgevoerde bestrijdingsmaatregelen blijken onvoldoende effect te sorteren. Om de kennis van de effectiviteit, mogelijke neveneffecten en kosten van kansrijke maatregelen te vergroten, worden in Noord-Brabant praktijkproeven uitgevoerd. Maatregelen die worden onderzocht, zijn onder andere de recent beschikbaar gekomen Flock en Lock-methodiek, baggeren en actief biologisch beheer. De maatregelen worden in verschillende combinaties toegepast. De uitvoering van de eerste maatregelen begon in mei 2009. Het project loopt dit jaar in ieder geval door. In het onderzoek werken de Wageningen Universiteit, de waterschappen Brabantse Delta, Aa en Maas en De Dommel en STOWA same

Effects of hydrogen peroxide and ultrasound on biomass reduction and toxin release in the cyanobacterium, microcystis aeruginosa

Cyanobacterial blooms are expected to increase, and the toxins they produce threaten human health and impair ecosystem services. The reduction of the nutrient load of surface waters is the preferred way to prevent these blooms; however, this is not always feasible. Quick curative measures are therefore preferred in some cases. Two of these proposed measures, peroxide and ultrasound, were tested for their efficiency in reducing cyanobacterial biomass and potential release of cyanotoxins. Hereto, laboratory assays with a microcystin (MC)-producing cyanobacterium (Microcystis aeruginosa) were conducted. Peroxide effectively reduced M. aeruginosa biomass when dosed at 4 or 8 mg L-1, but not at 1 and 2 mg L-1. Peroxide dosed at 4 or 8 mg L-1 lowered total MC concentrations by 23%, yet led to a significant release of MCs into the water. Dissolved MC concentrations were nine-times (4 mg L-1) and 12-times (8 mg L-1 H2O2) higher than in the control. Cell lysis moreover increased the proportion of the dissolved hydrophobic variants, MC-LW and MC-LF (where L = Leucine, W = tryptophan, F = phenylalanine). Ultrasound treatment with commercial transducers sold for clearing ponds and lakes only caused minimal growth inhibition and some release of MCs into the water. Commercial ultrasound transducers are therefore ineffective at controlling cyanobacteria

Guiding principles for the development and application of solid-phase phosphorus adsorbents for freshwater ecosystems

While a diverse array of phosphorus (P)-adsorbent materials is currently available for application to freshwater aquatic systems, selection of the most appropriate P-adsorbents remains problematic. In particular, there has to be a close correspondence between attributes of the P-adsorbent, its field performance, and the management goals for treatment. These management goals may vary from a rapid reduction in dissolved P to address seasonal enrichments from internal loading, targeting external fluxes due to anthropogenic sources, or long term inactivation of internal P inventories contained within bottom sediments. It also remains a challenge to develop new methods and materials that are ecologically benign and cost-effective. We draw on evidence in the literature and the authors’ personal experiences in the field, to summarise the attributes of a range of P-adsorbent materials. We offer 'guiding principles' to support practical use of existing materials and outline key development needs for new materials

Is the future blue-green or brown? The effects of extreme events on phytoplankton dynamics in a semi-arid man-made lake

In arid and semi-arid regions, a hydrological regime characterized by an annual cycle of drought and rainy seasons changes the volume and retention time of reservoirs. Such changes affect the limnological characteristics and lead to changes on phytoplankton community. Phytoplankton seasonal succession was studied in a Brazilian eutrophic semiarid water supply reservoir (Cruzeta). In this study, the changes in the biomass and species composition of phytoplankton during two annual hydrological cycles were analyzed, and the driving factors were evaluated.The composition of phytoplankton alternated between filamentous cyanobacteria, such as Cylindrospermopsis raciborskii, under conditions of mixing, and colonial species, such as Microcystis panniformis and Sphaerocavum brasiliensis, under conditions of high water column stability. The lower water level during a severe drought favored adaptive phytoplankton species with low requirement for resources, such as diatoms and cryptomonads. Extreme events, i.e., torrential rains and severe droughts, governed by the hydrological regime of the semi-arid region led to strong altered availability of resources in the watershed, directing the spatial and temporal dynamics of the phytoplankton in the Cruzeta man-made lake. The results showed an unusual behavior of the phytoplankton community contradicting the expectations about the climatic change scenario. Instead of an expected increase in cyanobacteria, the severe drought led to low biomass and resources, favoring diatoms and cryptomonad

Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis)

To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays – i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g-1 dry weight: Day 14: carapace +10.5 µg g-1, gills +112 µg g-1, ovaries +2.6 µg g-1, hepatopancreas +32.9 µg g-1 and abodminal muscle +3.2 µg g-1. Day 28: carapace +17.9 µg g-1; gills +182 µg g-1; ovaries +2.2 µg g-1; hepatopancreas +41.9 µg g-1 and abodminal muscle +7.6 µg g-1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effect

A Comparative Study on Three Analytical Methods for the Determination of the Neurotoxin BMAA in Cyanobacteria

The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA) has been considered a serious health threat because of its putative role in multiple neurodegenerative diseases. First reports on BMAA concentrations in cyanobacteria were alarming: nearly all cyanobacteria were assumed to contain high BMAA concentrations, implying ubiquitous exposure. Recent studies however question this presence of high BMAA concentrations in cyanobacteria. To assess the real risk of BMAA to human health, this discrepancy must be resolved. We therefore tested whether the differences found could be caused by the analytical methods used in different studies. Eight cyanobacterial samples and two control samples were analyzed by three commonly used methods: HPLC-FLD analysis and LC-MS/MS analysis of both derivatized and underivatized samples. In line with published results, HPLC-FLD detected relatively high BMAA concentrations in some cyanobacterial samples, while both LC-MS/MS methods only detected BMAA in the positive control (cycad seed sarcotesta). Because we could eliminate the use of different samples and treatments as causal factors, we demonstrate that the observed differences were caused by the analytical methods. We conclude that HPLC-FLD overestimated BMAA concentrations in some cyanobacterial samples due to its low selectivity and propose that BMAA might be present in (some) cyanobacteria, but in the low µg/g or ng/g range instead of the high µg/g range as sometimes reported before. We therefore recommend to use only selective and sensitive analytical methods like LC-MS/MS for BMAA analysis. Although possibly present in low concentrations in cyanobacteria, BMAA can still form a health risk. Recent evidence on BMAA accumulation in aquatic food chains suggests human exposure through consumption of fish and shellfish which expectedly exceeds exposure through cyanobacteria

The implications of nongenetic inheritance for evolution in changing environments

Nongenetic inheritance is a potentially important but poorly understood factor in population responses to rapid environmental change. Accumulating evidence indicates that nongenetic inheritance influences a diverse array of traits in all organisms and can allow for the transmission of environmentally induced phenotypic changes (‘acquired traits’), as well as spontaneously arising and highly mutable variants. We review models of adaptation to changing environments under the assumption of a broadened model of inheritance that incorporates nongenetic mechanisms of transmission, and survey relevant empirical examples. Theory suggests that nongenetic inheritance can increase the rate of both phenotypic and genetic change and, in some cases, alter the direction of change. Empirical evidence shows that a diversity of phenotypes – spanning a continuum from adaptive to pathological – can be transmitted nongenetically. The presence of nongenetic inheritance therefore complicates our understanding of evolutionary responses to environmental change. We outline a research program encompassing experimental studies that test for transgenerational effects of a range of environmental factors, followed by theoretical and empirical studies on the population-level consequences of such effects