Coccolith volume of the Southern Ocean coccolithophore Emiliania huxleyi as a possible indicator for palaeo-cell volume.

Coccolithophores are a key functional phytoplankton group and produce minute calcite plates (coccoliths) in the sunlit layer of the pelagic ocean. Coccoliths significantly contribute to the sediment record since the Triassic and their geometry have been subject to palaeoceanographic and biological studies to retrieve information on past environmental conditions. Here, we present a comprehensive analysis of coccolith, coccosphere and cell volume data of the Southern Ocean Emiliania huxleyi ecotype A, subject to gradients of temperature, irradiance, carbonate chemistry and macronutrient limitation. All tested environmental drivers significantly affect coccosphere, coccolith and cell volume with driver-specific sensitivities. However, a highly significant correlation emerged between cell and coccolith volume with Vcoccolith  = 0.012 ± 0.001 * Vcell  + 0.234 ± 0.066 (n = 23, r2  = .85, p < .0001, σest  = 0.127), indicating a primary control of coccolith volume by physiological modulated changes in cell volume. We discuss the possible application of fossil coccolith volume as an indicator for cell volume/size and growth rate and, additionally, illustrate that macronutrient limitation of phosphorus and nitrogen has the predominant influence on coccolith volume in respect to other environmental drivers. Our results provide a solid basis for the application of coccolith volume and geometry as a palaeo-proxy and shed light on the underlying physiological reasons, offering a valuable tool to investigate the fossil record of the coccolithophore E. huxleyi.

Draft genome sequence of a novel culturable marine chroococcalean cyanobacterium from the South atlantic ocean.

The novel chroococcalean cyanobacterium strain CENA595 was isolated from the deep chlorophyll maximum layer of the continental shelf of the South Atlantic Ocean. Here, we report the draft genome sequence for this strain, consisting of 60 contigs containing a total of 5,265,703 bp and 3,276 putative protein-coding genes.

Avaliaçäo de um bioensaio de multiespécie utilizando o fitoplâncton marinho natural / Evaluation of a multi-species bioassay using natural marine phytoplankton

Rapidamente tem crescido o interesse dos efeitos adversos das atividades antropogênicas sobre os ecossistemas naturais. Poluiçäo química é uma das mais pronunciadas consequências da industrializaçäo. O potencial dos impactos destas substâncias estressoras sobre os ecossistemas aquáticos e seus organismos podem ser avaliados, em parte, por testes ecotoxicológicos de diferentes complexidades. A questäo é: qual a complexidade dos sistemas testes que possa demonstrar de forma mais realística os efeitos das taxas de risco em comunidades naturais? Este trabalho teve por objetivo principal testar o desenho experimental de um bioensaio de multiespécies, utilizando a comunidade do fitoplâncton marinho natural. Observou-se taxas de crescimento algal e composiçäo específica a partir da induçäo de stress pelo agente químico Dicofol (1,1-bis-(clorofenil)-2,2,2-tricloroetano)