Ocorrência e co-existência de cianobactérias diazotróficas com o aumento da pluviosidade no Canal de São Sebastião – SP

Núcleo de Pesquisa em Biodiversidade Marinha da Universidade de São Paulo (NP-BioMar/USP

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

Occurrence and co-existence of diazotrophic cyanobacteria in São Sebastião-SP channel with increasing rainfall

A fixação de N2 é uma fonte importante de nitrogênio novo nos ciclos biogeoquímicos, realizado potencialmente por cianobactérias diazotróficas, principalmente em condições de limitação de nitrogênio. O canal de São Sebastião (CSS) é reconhecidamente meso-oligotrófico, porém, eventos episódicos de precipitação podem alterar as concentrações de nutrientes locais interferindo na ocorrência de diazotróficas. Este trabalho investigou o efeito do aumento da pluviosidade na ocorrência e coexistência de diazotróficas no CSS e na baía do Araçá (BA), em 9 cenários distintos. As diazotróficas Trichodesmium spp. e Richelia intracellularis ocorreram após o aumento da pluviosidade nos dois pontos, não co-existindo em dois eventos. R. intracellularis ocorreu somente em endossimbiose com diatomáceas do gênero Hemiaulus, com predomínio em H. membranaceus. Os ventos de SW no CSS indicaram relações diretas na ocorrência das diazotróficas, sugerindo advecção de células provindas de outros locais. A temperatura e o fosfato apresentaram relações significativas com a ocorrência das diazotróficas. As densidades de diazotróficas e da comunidade fitoplanctônica foram maiores na BA em todos os eventos, assim como as concentrações de clorofila-a e nutrientes, ressaltando a importância da interação das águas da BA com o CSS.The biological nitrogen fixation adds new nitrogen into the biogeochemical cycle. This process is attributed to diazothrophic cyanobacteria, which are known to occur in environments with nitrogen limitation. Although the São Sebastião Channel (CSS) is a meso-oligothrophic environment, local rain can affect nutrients concentrations, hence the occurrence of diazothrophic species. This work addressed how the increase in the precipitation rate alters the occurrence and co-existence of diazothrophic cyanobacteria in nine scenarios in the CSS and Araçá Bay (BA). The diazothrophic species Trichodesmium spp. and Richelia intracellularis occurred after an increase in rainfall, co-occurring in 7 of the 9 scenarios. Richelia intracellularis was always associated symbiotically with Hemiaulus diatoms, specially H. membranaceus. The occurrence of diazothrophic species was highly correlated to intense SW winds, suggesting the allochthonous input of cells in the CSS. The diazothrophic species occurrence was also associated with variations in temperature and phosphate concentration. The abundance of both diazothrophic species and phytoplankton community were higher in the BA in every scenario. The nutrients and chlorophyll-a concentrations were higher in the BA, highlighting the importance of water transport between BA and CSS

Retention-favorable timing of propagule release in barnacles and periwinkles

Recent studies on the ecology of marine larvae suggest that retention near coastal areas and self-recruitment are probably much more common than previously thought. In light of this, the advective potential of pelagic stages can be partially determined by the timing of propagule release. We sampled the upper-shore levels of a subtropical coastline in southeastern Brazil to examine the temporal patterns of propagule release for the common barnacle Chthamalus bisinuatus and the periwinkle Nodilittorina lineolata. The release timing in both species was very consistent between sites a few kilometers apart. Barnacles released nauplii in a rhythmic pattern, mostly coinciding with neap tides, when the speed of tidal currents was lowest. There was no variation in propagule release in relation to diel or flood-ebb tidal cycles. Periwinkles released propagules in a very irregular pattern, which remarkably matched a time series of wave heights. Egg capsules were released during periods of rough seas, when onshore surface currents were expected to prevail. Eggs were released mostly during ebb tides, and there was no diel variation. Propagule release rhythms are usually viewed as a means to ensure fast offshore advection, thus avoiding presumed hazardous conditions for larvae. However, propagule release strategies in these upper-shore species would more likely contribute to the retention of offspring close to parental stocks.FAPESP[2008/10085-5]FAPESP[06/58700-4

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