Gone with the wind? Newspaper discourse of eutrophication and blue‐green algae blooms in Finland

The mass media shape the public and policy agenda by giving prominence to certain ecosystem changes and risks, as well as by framing some policy measures as the preferred ones. Based on longitudinal analysis of the leading Finnish newspaper, this study considers the media coverage of eutrophication. The results show an increase of reporting in the late 1990s as a result of intertwined ecological and social factors – i.e. intense algal occurrences and establishment of a national communication system. The news coverage has highlighted the harmful algal blooms and health risks of algal toxins and has framed short‐term weather conditions as the key factor regulating algal occurrences. This creates a challenge for environmental management aimed at reduction in the nutrient discharges that influence the state of the environment in the long term.     

Occurrence of copper resistant mutants in the toxic cyanobacteria Microcystis aeruginosa: characterisation and future implications in the use of copper sulphate as algaecide

Freshwater toxic cyanobacteria are an increasing problem to human and animal health. Control of cyanobacteria in water supply reservoirs involves the use of algaecides, such as copper sulphate, usually in a repetitive way. Repercussions of recurrent algaecide treatments on cyanobacteria population dynamics remain still unknown. We studied the adaptation of cyanobacteria to lethal doses of copper sulphate by using Microcystis aeruginosa as an experimental model. A fluctuation analysis demonstrated that copper-resistant cells arise by spontaneous mutations that occur randomly prior to exposition to copper sulphate. The rate of spontaneous mutation from copper sensitivity to resistance was 1.76×10⁻⁶ mutants per cell division. Resistant mutants exhibited a diminished fitness in the absence of copper sulphate, but only these variants were able to grow at Cu²⁺ concentrations higher than 5.8 μM. In addition, copper-resistant cells were significantly smaller than wild-type ones. Warnings on the long-term consequences of repetitive algaecide treatments in water supplies are suggested.     

Isolation,characterization, and quantitative analysis of Microviridin J,a new Microcystis metabolite toxic to Daphnia

This paper describes the purification and characterization of microviridin J, a newly discovered metabolite of Microcystis that causes a lethal molting disruption in Daphnia spp., upon ingestion of living cyanobacterial cells. Microviridin J consists of an acetylated chain of 13 amino acids arranged in three rings and two side chains. Unlike other known isoforms of microviridin, microviridin J contains arginine that imparts a unique solution conformation characterized by proximal hydrophobic interactions between Arg and other regions of the molecule. This eventually results in the formation and stabilization of an additional ring system. Microviridin J potently inhibits porcine trypsin, bovine chymotrypsin, and daphnid trypsin-like proteases. The activity against trypsin is most likely due to Arg and its distinctive conformational interactions. Overall, the data presented for microviridin J emphasize once again the ability of cyanobacteria to produce numerous and potent environmental toxins.     

The biomass dynamics of cyanobacteria in an annual cycle determined by confocal laser scanning microscopy

We recently published a method for estimating cyanobacteria biomass in delta microbial mats from the Ebro river using confocal laser scanning microscopy (CLSM). The present paper uses this method for identifying different groups of cyanobacteria and for determining their biomass dynamics. Microcoleus chthonoplastes and the Lyngbya-Oscillatoria were the most important contributors to the cyanobacterial biomass throughout the study. Biomass values ranged from 1.29 to 6.55 mgC/cm2 sediment for Microcoleus chthonoplastes, and from 128 microgC/cm2 to 3.16 mgC/cm2 sediment for Lyngbya-Oscillatoria. This technique is useful for determining biomass and for studying filamentous cyanobacteria as well as ramified eukaryotic cells. Confocal serial sections through the samples can be obtained. Two-dimensional images from the samples can be used to calculate the biomass of individual cells.     

Development of operational strategies to remove carbon dioxide in photobioreactors

The objective of this work was to evaluate different operational strategies for photobioreactors to remove carbon dioxide using the cyanobacteria, Aphanothece microscopica Nägeli. Two types of reactor configuration, bubble column and airlift were evaluated under three different operational conditions to treat air containing 15% carbon dioxide: simple operation, air recirculation and two sequential reactors. The results obtained showed that the reactor configuration and the operational mode were both determinant criteria for the performance of photobioreactors in the biological conversion of carbon dioxide. Operations with air recirculation showed possibilities for use in small-scale operations, but two-stage sequential photobioreactors (elimination capacity and removal efficiency of 12,217 g_carbon/m³_reactor day and 52.5%, respectively) were shown to be the operational mode with greatest potential for application on an industrial scale by the increased removal efficiency.     

Evaluation of seafood toxicity in the Australes archipelago (French Polynesia) using the neuroblastoma cell-based assay

Ciguatera fish poisoning (CFP), a disease caused by consuming fish that have accumulated ciguatoxins (CTXs) in their tissue, is regarded as the most prevalent form of intoxication in French Polynesia. Recently, the Australes, one of the least affected archipelago until the early 1980s, has shown a dramatic increase in its incidence rates in 2009 with unusual CFP cases. In the present work, potential health hazards associated with the proliferation of various marine phytoplankton species and the consumption of fish and marine invertebrates highly popular among local population were assessed in three Australes islands: Raivavae, Rurutu and Rapa. Extracts from the marine dinoflagellates Gambierdiscus, Ostreospis and mat-forming cyanobacteria as well as fish, giant clams and sea urchin samples were examined for the presence of CTXs and palytoxin (PLTX) by using the neuroblastoma cell-based assay (CBA-N2a).

Cytotoxic responses observed with both standards (Pacific CTX-3C and PLTX) and targeted marine products indicate that CBA-N2a is a robust screening tool, with high sensitivity and good repeatability and reproducibility. In Rurutu and Raivavae islands, our main findings concern the presence of CTX-like compounds in giant clams and sea urchins, suggesting a second bio-accumulation route for CFP toxins in the ciguatera food chain. In Rapa, the potential CFP risk from Gambierdiscus bloom and fish was confirmed for the first time, with levels of CTXs found above the consumer advisory level of 0.01?ng Pacific CTX-1B?g^?1 of flesh in three fish samples. However, despite the presence of trace level of PLTX in Ostreopsis natural assemblages of Rapa, no sign of PLTX accumulation is yet observed in tested fish samples.

Because this multi-toxinic context is likely to emerge in most French Polynesian islands, CBA-N2a shows great potential for future applications in the algal- and toxin-based field monitoring programmes currently on hand locally.     

Antibacterial and antifungal activities of selected microalgae and cyanobacteria

In vitro activity of nine cyanobacterial and ten microalgal newly isolated or culture collection strains against eight significant food‐borne pathogens has been evaluated and compared. Water extracts and culture liquids of Gloeocapsa sp. and Synechocystis sp. demonstrated the widest spectrum of activity with minimal inhibitory concentration (MIC) ranging from 1.56 to 12.5 mg mL^?1. Culture liquid of Anabaena sp. had the highest activity (MIC = 0.39 mg mL^?1) but only to Gram‐positive bacteria. Ethanol extracts and fatty acids from all cyanobacteria and microalgae were active against Streptococcus pyogenes and/or Staphylococcus aureus. The fatty acids of Synechocystis sp. inhibited the growth of Bacillus cereus, Escherichia coli and Candida albicans (MIC values of 2.5–1.25 mg mL^?1, respectively). Exopolysaccharides (EPS) of Gloeocapsa sp. were the sample that exhibited activity against all test pathogens with lowest MIC values (0.125–1 mg mL^?1). High activity with a narrower range of susceptible targets demonstrated the exopolysaccharides of Synechocystis sp. and Rhodella reticulata. Antimicrobial activity was proven for phycobiliproteins isolated from Synechocystis sp., Arthrospira fusiformis, Porphyridium aerugineum and Porphyridium cruentum, respectively. In conclusion Gloeocapsa sp. and Synechocystis sp. and especially their exopolysaccharides showed the most promising potential against the examined food pathogens.     

丝状藻响应温度变化的生长及功能特性

针对近年来丝状蓝藻水华的频繁暴发问题,研究了3种常见丝状藻生长对温度的响应以及生长与功能特性间的关系。结果表明：温度由15℃增加至30℃,拟柱孢藻比生长速率由0.28 d^-1增加为0.70 d^-1,光合活性（F_v/F_m）在0.40~0.61范围内波动,单位藻细胞溶解性总氮（DTN）和溶解性反应磷（SRP）消耗量也分别增加了6.36 mg-DTN/mg-Chl.a、0.15 mg-SRP/mg-Chl.a;伪鱼腥藻比生长速率从0.12 d^-1到0.60 d^-1,F_v/F_m在15℃时达到最低,为0.12,单位藻细胞氮磷消耗量也分别增加了21.72 mg-DTN/mg-Chl.a、1.71 mg-SRP/mg-Chl.a;水华束丝藻比生长速率从0.20 d^-1到0.44 d^-1,F_v/F_m受影响较小,单位藻细胞氮磷消耗量也分别增加了12.29 mg-DTN/mg-Chl.a、0.83 mg-SRP/mg-Chl.a。温度升高都会促进3种丝状藻生长,拟柱孢藻易在大于30℃高温下形成优势;伪鱼腥藻温度适应范围广,但温度低于15℃会抑制伪鱼腥藻生长;水华束丝藻最佳生长温度为25℃,并可在15℃时取得优势,耐低温能力较强。另外,丝状藻可通过权衡藻细胞生理特性以维持不同温度下的生长优势。