Abundance of a chlorophyll a precursor and the oxidation product hydroxychlorophyll a during seasonal phytoplankton community progression in the Western English Channel

This study presents the first in-situ measurements of the chlorophyll a oxidation product, hydroxychlorophyll a as well as the chlorophyll a precursor, chlorophyll aP276 conducted over an annual cycle. Chlorophyll a oxidation products, such as hydroxychlorophyll a may be associated with the decline of algal populations and can act as an initial step in the degradation of chlorophyll a into products which can be found in the geochemical record, important for studying past climate change events. Here, hydroxychlorophyll a and chlorophyll aP276 were measured at the long-term monitoring station L4, Western Channel Observatory (UK, www.westernchannelobservatory.org) over an annual cycle (2012). Weekly measurements of phytoplankton species composition and abundance enabled detailed analysis of possible sources of hydroxychlorophyll a. Dinoflagellates, 2 diatom species, the prymnesiophyte Phaeocystis spp. and the coccolithophorid Emiliania huxleyi were all associated with hydroxychlorophyll a occurrence. However, during alternate peaks in abundance of the diatoms, no association with hydroxychlorophyll a occurred, indicating that the oxidation of chlorophyll a was dependant not only on species but also on additional factors such as the mode of mortality, growth limiting factor (i.e. nutrient concentration) or phenotypic plasticity. Surface sediment samples contained 10 times more hydroxychlorophyll a (relative to chlorophyll a) than pelagic particulate samples, indicating that more chlorophyll a oxidation occurred during sedimentation or at the sediment-water interface, than in the pelagic environment. In addition, chlorophyll aP276 correlated with chl-a concentration, thus supporting its assignment as a chl-a precursor

Resource Supply Overrides Temperature as a Controlling Factor of Marine Phytoplankton Growth

The universal temperature dependence of metabolic rates has been used to predict how ocean biology will respond to ocean warming. Determining the temperature sensitivity of phytoplankton metabolism and growth is of special importance because this group of organisms is responsible for nearly half of global primary production, sustains most marine food webs, and contributes to regulate the exchange of CO2 between the ocean and the atmosphere. Phytoplankton growth rates increase with temperature under optimal growth conditions in the laboratory, but it is unclear whether the same degree of temperature dependence exists in nature, where resources are often limiting. Here we use concurrent measurements of phytoplankton biomass and carbon fixation rates in polar, temperate and tropical regions to determine the role of temperature and resource supply in controlling the large-scale variability of in situ metabolic rates. We identify a biogeographic pattern in phytoplankton metabolic rates, which increase from the oligotrophic subtropical gyres to temperate regions and then coastal waters. Variability in phytoplankton growth is driven by changes in resource supply and appears to be independent of seawater temperature. The lack of temperature sensitivity of realized phytoplankton growth is consistent with the limited applicability of Arrhenius enzymatic kinetics when substrate concentrations are low. Our results suggest that, due to widespread resource limitation in the ocean, the direct effect of sea surface warming upon phytoplankton growth and productivity may be smaller than anticipated

A benthic Si mass balance on the Congo margin: Origin of the 4000 m DSi anomaly and implications for the transfer of Si from land to ocean

International audienceTo elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO2) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the intensity of DSi recycling is consistent with the degradation of organic matter, as observed from Si:O2 ratios in the benthic fluxes compared to that ratio observed in the anomalies. Strong imbalances, observed in both the Si and C mass balances, suggest that the biogenic matter that degrades and dissolves in these sediments near 4000 m does not come from pelagic sedimentation. It is probably not coming also from the deep channel, because observations were similar in the deep channel vicinity (site D) and further south, far from its influence (site C). The composition of the sediments, with an Si:C ratio close to that observed on continental shelves, suggests that this matter is coming from downslope transport. A first estimate of the magnitude of this flux at global scale, close to 12 T mol Si yr−1, suggests that it may be an important path for transferring Si from land to ocean

Letramento e alfabetização na escola para surdos

Orientadora: Sueli de Fátima FernadesMonografia(Graduação) - Universidade Federal do Paraná,Setor de Ciências Humanas, Curso de Licenciatura em Letras LibrasResumo: Este Trabalho de Conclusão de Curso aborda a temática das práticas de alfabetização e letramento para surdos. Nosso objetivo foi investigar como os processos de leitura e escritas são desenvolvidas na escola para surdos. A pesquisa utilizada é de abordagem qualitativa e utiliza a revisão de literatura e o levantamento de dados no campo de pesquisa. A revisão de literatura envolve a contribuição de autores que debatem o tema de Alfabetização e Letramento (SOARES, 1999, 2000, 2009) e letramento para surdos (FERNANDES, 2003, 2006, 2007, 2008). O levantamento de dados no campo foi realizado por meio da observação em duas escolas para surdos localizadas nos municípios de Curitiba e São José dos Pinhais, com proposta de educação bilíngue: Língua brasileira de Sinais (Libras) e Língua Portuguesa. Foram observados quatro aspectos: a) caracterização da escola e Projeto Político-Pedagógico (PPP);b) a metodologia de ensino de leitura e escrita da professora regente; c)práticas de alfabetização/letramento desenvolvidas em sala de aula e d) caracterização da turma: os alunos surdos. As turmas de 4º e 5º anos do Ensino Fundamental, eram compostas de alunos surdos com idade entre 9 a 15 anos e as professoras regentes eram surdas bilíngues. Os resultados indicam um avanço em relação às práticas de educação bilíngue nas escolas, há presença de professores surdos como modelo das crianças surdas, ensinando Libras e outras disciplinas, a Libras é amplamente usada na comunidade escolar e nas práticas de comunicação e ensino em sala de aula, fazendo da escola um ambiente bilíngue. Em relação ao nosso problema de pesquisa, observamos que o ensino de português como segunda língua, na modalidade escrita, ainda enfrenta muitos desafios, já que as metodologias de ensino não estão adequadas às práticas de letramento, com acesso aos textos como ponto de partida para o trabalho e à abordagem de gêneros textuais diversificados. Percebemos que a maioria das práticas enfatizam a alfabetização baseada nas relações letra/som e os alunos têm um domínio muito precário da leitura e escrita

A benthic Si mass balance on the Congo margin: Origin of the 4000 m DSi anomaly and implications for the transfer of Si from land to ocean

11 pages, 6 figures, 3 tables.-- Article in press.To elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO2) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the intensity of DSi recycling is consistent with the degradation of organic matter, as observed from Si:O2 ratios in the benthic fluxes compared to that ratio observed in the anomalies. Strong imbalances, observed in both the Si and C mass balances, suggest that the biogenic matter that degrades and dissolves in these sediments near 4000 m does not come from pelagic sedimentation. It is probably not coming also from the deep channel, because observations were similar in the deep channel vicinity (site D) and further south, far from its influence (site C). The composition of the sediments, with an Si:C ratio close to that observed on continental shelves, suggests that this matter is coming from downslope transport. A first estimate of the magnitude of this flux at global scale, close to 12 T mol Si yr−1, suggests that it may be an important path for transferring Si from land to ocean.This study has been partly funded through the Si-WEBS RTN (HPRN-CT-2002-00218) and the European Commission is greatly acknowledged.Peer reviewe

Seasonal patterns in Arctic planktonic metabolism (Fram Strait-Svalbard region)

The metabolism of the Arctic Ocean is marked by extremely pronounced seasonality and spatial heterogeneity associated with light conditions, ice cover, water masses and nutrient availability. Here we report the marine planktonic metabolic rates (net community production, gross primary production and community respiration) along three different seasons of the year, for a total of eight cruises along the western sector of the European Arctic (Fram Strait - Svalbard region) in the Arctic Ocean margin: one at the end of 2006 (fall/winter), two in 2007 (early spring and summer), two in 2008 (early spring and summer), one in 2009 (late spring-early summer), one in 2010 (spring) and one in 2011 (spring). The results show that the metabolism of the western sector of the European Arctic varies throughout the year, depending mostly on the stage of bloom and water temperature. Here we report metabolic rates for the different periods, including the spring bloom, summer and the dark period, increasing considerably the empirical basis of metabolic rates in the Arctic Ocean, and especially in the European Arctic corridor. Additionally, a rough annual metabolic estimate for this area of the Arctic Ocean was calculated, resulting in a net community production of 108 g C m(-2) yr(-1)