Intraspecific variation in alkaline phosphatase activity in Phaeodactylum tricornutum (Bacillariophyceae, Bohlin)

To describe potential intraspecific variation in phosphorus incorporation in two strains of Phaeodactylum tricornutum (Bohlin), Ub3 and Ub7, alkaline phosphatase (AP) activity was evaluated via enzyme-labeled fluorescence assay. Analysis using the probe ELF-97 (R) provides individual evaluation, and therefore can determine the nutritional status of inorganic phosphorus in phytoplanktonic cells. Bioassays compared the control treatment to both phosphate-enriched and phosphate-depleted treatments by varying only the phosphate concentration in the media. The P. tricornutum strains exhibited differences in their development when incubated in the phosphate-enriched media. The development of the Ub7 strain differed by exhibiting "luxury uptake" and utilization of organic phosphorus, and the alkaline phosphatase analysis indicated limitations of this clone under such conditions. The Ub7 strain showed higher AP activity, when compared to Ub3, in the P-enriched condition. P. tricornutum presented increases in AP activity and low variation in Surface/Volume ratio, by increasing biovolume and its maximum linear dimension, as strategies for phosphate incorporation. Our results highlight intraspecific differences in alkaline phosphatase activity, and hence differences in the incorporation of organic phosphorus, as the tested species regulated enzymatic activity under different external phosphate concentrations.Univ Estado Rio de Janeiro, Fac Oceanog, Lab Ecol & Cult Fitoplancton Marinho, BR-20550900 Rio De Janeiro, RJ, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, Campus Baixada Santista, BR-11030400 Santos, SP, BrazilInst Nacl Pesquisas Espaciais, Km 39, BR-12630000 Cachoeira Paulista, SP, BrazilUniv Fed Sao Paulo, Dept Ciencias Mar, Campus Baixada Santista, BR-11030400 Santos, SP, BrazilWeb of Scienc

Liberação de polissacarídeos extracelulares por Spondylosium pygmaeum (Desmidiaceae) em função do crescimento em diferentes fontes de nitrogênio

Dissertação (mestrado)-Universidade Federal do Rio Grande, Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais, Instituto de Ciências Biológicas, 2007.A produção extracelular de compostos orgânicos pelo fitoplâncton possui grande importância ecológica, principalmente pelo incremento da biodiversidade funcional gerada a partir de associações entre o fito e o bacterioplâncton. Entretanto, muito pouco se conhece a respeito dos processos fisiológicos que controlam este mecanismo. O objetivo deste trabalho é determinar o efeito da fonte de nitrogênio e da sua disponibilidade na excreção de carboidratos totais, bem como na composição dos polissacarídeos extracelulares produzidos por Spondylosium pygmaeum (Desmidiaceae). Esta linhagem foi isolada de um pequeno lago, localizado no extremo sul do Brasil (Rio Grande, RS), e está sendo mantida em condições axênicas na coleção de culturas de microalgas dulcícolas do Departamento de Ciências Morfobiológicas da FURG. Foram realizados experimentos testando duas concentrações de nitrato (10 e 100 μM) e amônio (20 e 150 μM). O crescimento foi monitorado tanto pela densidade celular (contagem ao microscópio), como pelo teor de clorofila-a (espectrofotometria). A concentração das fontes de nitrogênio no meio foi determinada por cromatografia iônica (nitrato) e espectrofotometria (amônio), enquanto a produção de carboidratos extracelulares totais foi monitorada por espectrofotometria (método fenol-sulfúrico). A caracterização dos polissacarídeos extracelulares foi realizada por HPLC com detecção por pulsos amperométricos. Os resultados mostraram que S. pygmaeum atinge maior biomassa quando cultivada com nitrato, embora a taxa de crescimento tenha sido maior quando cultivada com amônio. A taxa de excreção aproxima-se de zero durante os experimentos, com ambos nutrientes. Desta forma, pode-se dizer que esta espécie cresce na mesma proporção que produz carboidratos extracelulares. Este resultado demonstra que o estado fisiológico não altera a taxa de excreção de carboidratos por célula. A composição dos polissacarídeos extracelulares produzidos por S. pygmaeum varia durante o crescimento e com a fonte de nitrogênio, bem como quando os nutrientes estão limitantes. Utilizando-se o nitrato como fonte de nitrogênio, encontrou-se a Galactose, a Glicose e Manose e/ou Xilose como os principais açúcares; enquanto que com amônio, encontrou-se a Glicose, Manose e/ou Xilose e a Fucose. Esta constituição predominante dos polissacarídeos produzidos pela linhagem assemelha-se aos de outras desmídias planctônicas

Variabilidade espacial e temporal do fitoplâncton na zona de arrebentação da praia do Cassino (RS, Brasil): relação com os depósitos de lama e nutrientes dissolvidos

Tese(doutorado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2012.Na zona de arrebentação de praias arenosas e expostas ocorrem acumulações de diatomáceas, as quais são importantes produtores primários. Visando entender se existe uma variação espacial e temporal do fitoplâncton na zona de arrebentação da Praia do Cassino, foram analisadas semanalmente cinco estações no período de deposição lama (maio a julho de 2009), e posteriormente (agosto de 2009 a abril 2010) três estações quinzenalmente ao longo de 21 km. As relações entre variáveis ambientais e a composição e biomassa do fitoplâncton foram comparadas, verificando-se que a deposição de lama influenciou a transparência da água, mas não foi detectada diferença significativa entre os valores médios de nutrientes e de clorofila a nas estações ao longo do ano. As diatomáceas foram dominantes, destacando-se a contribuição de cêntricas unicelulares do microplâncton e Skeletonema spp., e das penadas Asterionellopsis glacialis e Pseudo-nitzschia sp. Porém, a densidade de A. glacialis encontrada neste ano foi menor do que em anos anteriores, enquanto os gêneros planctônicos Skeletonema e Pseudo-nitzschia apareceram em alta densidade. Em laboratório foram realizados experimentos curtos com enriquecimento de nutrientes inorgânicos dissolvidos testando-se ao todo sete proporções de silicato, nitrato e fosfato, com objetivo de determinar sua influência sobre as microalgas da Praia do Cassino. Como resultado, a biomassa fitoplanctônica exibiu um aumento significativo nos tratamentos com adição de nitrato, independentemente da proporção adicionada, indicando que o nitrato é o nutriente mais importante no controle da biomassa e do crescimento das diatomáceas da Praia do Cassino.In the surf zone of exposed sandy beaches significant accumulations of diatoms occur, which are important primary producers. In order to determine the spatial and temporal variability of phytoplankton in the surf zone, five and three stations were studied in the period with mud deposition (weekly sampling, May to July 2009) and without (every two weeks, August 2009 to April 2010), respectively, along 21 km of Cassino Beach. The relationships among environmental variables and phytoplankton composition and concentration were compared. The influence of mud was evident on the water transparency, but not on the mean values of nutrients and chlorophyll a. The diatoms were dominant, emphasizing the contribution of the unicellular centric microplankton and Skeletonema spp., and the pennates Asterionellopsis glacialis and Pseudo-nitzschia spp. However, the density of A. glacialis found in this study was lower than in previous years. Moreover, the planktonic species Skeletonema and Pseudo-nitzschia appeared in high density. In laboratory, short experiments were performed with dissolved inorganic nutrient enrichment by testing seven proportions of silicate, nitrate and phosphate, in order to determine their influence on the microalgae from Cassino Beach. In both experiments, density showed a significant increase (mainly diatoms) in the treatments with nitrate addition, regardless of the proportion added, showing that nitrate is the most important nutrient controlling diatoms density and growth at the sandy Cassino Beach

Intraspecific variation in alkaline phosphatase activity in Phaeodactylum tricornutum (Bacillariophyceae, Bohlin)

ABSTRACT To describe potential intraspecific variation in phosphorus incorporation in two strains of Phaeodactylum tricornutum (Bohlin), Ub3 and Ub7, alkaline phosphatase (AP) activity was evaluated via enzyme-labeled fluorescence assay. Analysis using the probe ELF-97(r) provides individual evaluation, and therefore can determine the nutritional status of inorganic phosphorus in phytoplanktonic cells. Bioassays compared the control treatment to both phosphate-enriched and phosphate-depleted treatments by varying only the phosphate concentration in the media. The P. tricornutum strains exhibited differences in their development when incubated in the phosphate-enriched media. The development of the Ub7 strain differed by exhibiting "luxury uptake" and utilization of organic phosphorus, and the alkaline phosphatase analysis indicated limitations of this clone under such conditions. The Ub7 strain showed higher AP activity, when compared to Ub3, in the P-enriched condition. P. tricornutum presented increases in AP activity and low variation in Surface/Volume ratio, by increasing biovolume and its maximum linear dimension, as strategies for phosphate incorporation. Our results highlight intraspecific differences in alkaline phosphatase activity, and hence differences in the incorporation of organic phosphorus, as the tested species regulated enzymatic activity under different external phosphate concentrations

Antioxidant responses and reactive oxygen species generation in different body regions of the estuarine polychaeta Laeonereis acuta (Nereididae)

The aim of this study was to analyze the total antioxidant capacity (TOSC), generation of reactive oxygen species (ROS) and lipid peroxidation (LPO) in the different body regions of the estuarine polychaeta Laeonereis acuta (Nereididae) sampled at non-polluted (NOPOL)and polluted (POL) sites from Lagoa dos Patos (Southern Brazil). Organisms collected at POL during summer showed similar (p > 0.05)TOSC values along the body, but worms collected at NOPOL presented higher (p < 0.05) TOSC values in the posterior (P) region in respect of anterior (A) region and middle (M) region. TOSC in the P region at NOPOL was higher (p < 0.05) compared with the same body region of worms at POL. In summer, ROS concentration was higher in A andMregions of worms at POL in respect of the organisms at NOPOL. During winter all the regions showed higher ROS in worms sampled at POL. It was registered absence of season influence on LPO content,but in the P region at NOPOL in summer there were lower LPO levels compared with the others regions (p < 0.05). In vitro assays showed that P region, despite a higher basal ROS, presented a higher competence to cope with pro-oxidants compared with A and M regions (p < 0.05), corroborating the field results. A lower proteic sulfhydril content was observed in P in respect of the other regions (p < 0.05) supporting the idea of a highest oxidant condition in this region. The results indicate that worms collected at the POL site are confronted to higher ROS concentrations, affecting its antioxidant capacity, a result that depends of body regions

Toxicological responses in Laeonereis acuta (Annelida, Polychaeta) after arsenic exposure

Several environmental pollutants, including metals, can induce oxidative stress. So, the objective of this study was to evaluate the effects of arsenic (AsIII, as As2O3) on the antioxidant responses in the polychaete Laeonereis acuta. Worms were exposed to two environmentally relevant concentrations of As, including the highest previously allowed by Brazilian legislation (50 μg As/l). A control group was kept in saline water(10‰) without added metal. It was observed that: (1) a peak concentration of lipid peroxide was registered after 2 days of exposure to 50 μg As/l (61±3.2 nmol CHP/g wet weight)compared to the control group (43±4.5 nmol CHP/g wet weight), together with a lowering of the activity of the antioxidant enzyme catalase (−47 and −48%, at 50 or 500 μg As/l respectively) and a higher superoxide dismutase activity (+305% at 50 μg As/l with respect to the control group); (2) a lower conjugation capacity through glutathione-S-transferase activity was observed after 7 days of exposure to 50 μg As/l (−48% compared to the control group); (3) a significant increase in As concentration was verified after 1 week of exposure to both As concentrations 50 and 500 μg/l); (4) worms exposed to As showed a limited accumulation of related methylated As species and the levels of non-toxic As species like arsenobetaine (AsB) and arsenocholine (AsC) remained unchanged during the exposure period when compared with the controls. Overall, it can be concluded that As interfered in the antioxidant defense system of L. acuta, even at low concentrations (50 μg/l)that Brazilian legislation previously considered safe. The fact that worms exposed to As showed high levels of methylated As species indicates the methylation capability of L. acuta, although the high levels of inorganic As suggest that not all the administered AsIII (as As2O3) is completely removed or biotransformed after 7 days of exposure