[Elucidation of Phenomena Involving Cyanobacteria in Freshwater Ecosystem by Chemically Ecological Approach].

Lakes Sagami and Tsukui are reservoirs constructed by connecting to the Sagami River. Because of eutrophication of the lakes, cyanobacteria have appeared every year. This review deals with phenomena related to occurrence of cyanobacteria that have been observed for 40 years since 1974 at the lakes. These 40 years of observations raised three interesting issues including the retention of cyanobacteria on their surfaces. These phenomena have been attributed to the usual factors, such as illuminance, nutrition and water temperature, but our research results suggested that they cannot be resolved without the introduction of another factor. We have attempted to elucidate various phenomena involving cyanobacteria in lake ecosystems by chemical ecological methods using volatile organic compounds (VOCs) produced by the cyanobacteria as indicators. One of the VOCs, ß-cyclocitral, was significantly involved in the above phenomena, which was considered to be produced by the carotenoid cleavage dioxygenase (CCD) of the cyanobacteria. ß-Cyclocitral was not produced in the two known CCDs, but two additional CCDs to Microcystis aeruginosa participated to produce the ß-cyclocitral. These CCDs did not directly produce ß-cyclocitral, but it was accumulated in cells as their precursors. The released ß-cyclocitral underwent a Baeyer-Villiger-like oxidation. It was speculated that Microcystis activated the CCD genes through density stress and produced ß-cyclocitral, which acted as an allelopathic substance. As a result, the number of cells of cyanobacteria decreased, and the resulting nitrogen and phosphorus were fed to the living cyanobacteria. It is postulated that this "quorum sensing" was functioning in the above-mentioned issues.

Biomass allocation and nutrients balance related to the concentration of Nitrogen and Phosphorus in Salvinia auriculata (Salviniaceae) / Alocação de biomassa e o Balanço de nutrientes relacionados à concentração de Nitrogênio e Fósforo em Salvinia auriculata (Salviniaceae)

Abstract Aquatic plants can use differential allocation (trade-off) of carbon among their structures depending on the nutrition concentration. Given that N and P are limiting in the growth of plants, our questions were: Are the N and P concentrations in S. auriculata related to the biomass allocation to its structures? Is a differential allocation of N and P between floating and submerged leaves? We evaluated the relation between the nutrients and the biomass allocation, and the trade-off among the leaves using the Spearman correlation. Our results showed that N and P concentrations in S. auriculata are related to the biomass allocation to its structures, and that there is no trade-off of these nutrients between “shoot and root”. Thus, we can see the importance of N and P concentration in the biomass of S. auriculata, and why this plant is capable to development in different environments as a weedy.

Resumo Plantas aquáticas podem realizar alocação diferencial (trade-off) de carbono entre as suas estruturas dependo da disponibilidade de nutrientes. Considerando que N e P são limitantes para o crescimento de plantas, nossas perguntas foram: As concentrações de N e P em S. auriculata estão relacionadas com a alocação de biomassa para suas estruturas? Existe alocação diferencial de N e P entre os folíolos aéreos e a “raiz”? Avaliamos a relação entre os nutrientes e a biomassa, e o trade-off entre as folhas utilizando correlação de Spearman. Os resultados encontrados mostram que as concentrações de N e P em S. auriculata estão relacionadas com a alocação de biomassa para as suas estruturas, e que não há um trade-off de N e P entre os folíolos aéreos e a “raiz”. Dessa maneira, é possível observar a importância de N e P no ganho de biomassa de S. auriculata, e porque a espécie é capaz de se desenvolver em diferentes ambientes como uma planta daninha.

Biomass allocation and nutrients balance related to the concentration of Nitrogen and Phosphorus in Salvinia auriculata (Salviniaceae).

Aquatic plants can use differential allocation (trade-off) of carbon among their structures depending on the nutrition concentration. Given that N and P are limiting in the growth of plants, our questions were: Are the N and P concentrations in S. auriculata related to the biomass allocation to its structures? Is a differential allocation of N and P between floating and submerged leaves? We evaluated the relation between the nutrients and the biomass allocation, and the trade-off among the leaves using the Spearman correlation. Our results showed that N and P concentrations in S. auriculata are related to the biomass allocation to its structures, and that there is no trade-off of these nutrients between "shoot and root". Thus, we can see the importance of N and P concentration in the biomass of S. auriculata, and why this plant is capable to development in different environments as a weedy.

Slick science: will new BP funds keep Gulf genomics afloat?

Funding injections by British Petroleum this summer are fueling studies in the Gulf Coast, raising hopes that the Deepwater Horizon oil spill might provide answers to long-standing questions on the nature of cellular toxicity. Rebecca Alvania investigates.

Conducting site-specific assessments of selenium bioaccumulation in aquatic systems.

Selenium (Se) is a chemical of concern at many locations across North America and elsewhere, and site-specific conditions are important when evaluating its bioaccumulation and effects in aquatic ecosystems. Most regulatory criteria and guidelines are based on waterborne Se concentrations. In contrast, the draft water quality chronic criterion of the US Environmental Protection Agency (USEPA) is based on Se concentrations in whole-body fish, and current information suggests the agency will issue a new draft criterion based in part on fish egg and/or ovary Se concentrations. However, implementation guidance is not available from the agency for either of these tissue-based criteria. Therefore, we describe a phased approach for field and laboratory assessments of Se bioaccumulation in fish and aquatic-dependent birds that can be applied in different environmental settings with the goal of developing and interpreting a tissue-based Se value. We recommend here the use of decision trees, conceptual models, and data quality objectives toward defining what should be done during the assessment, plus sampling and monitoring procedures for the assessment. First, available tissue or waterborne Se concentrations should be compared to tissue residue guidelines or adopted water quality criteria and guidelines. When needed, reproductive toxicity testing and assessment of fish populations should also be conducted in the area of interest. In addition, extensive data on the effects of Se on fish and bird species have been developed, and describing the associations between fish or bird egg tissue, aqueous Se, and potential effects is important for sites where Se may be a concern. Selenium bioaccumulation and toxicity also are of concern for amphibians and oviparous reptiles, but interpretive information is very limited for those species. Recent science indicates that effects are more strongly related to tissue concentrations of Se (especially in the eggs or ovaries of oviparous vertebrates) than to waterborne concentrations. Overall, we conclude that the approach for site-specific assessment must be flexible enough to allow what is appropriate for the situation. Furthermore, risk management and remediation decisions should be based on combined biology and chemistry data, using multiple lines of evidence in the assessment.