Caracterización de las asociaciones de cocolitóforos en las cuencas offshore del Pacífico colombiano

This study was conducted on coccolithophores recovered from 39 piston-core samples taken offshore Chocó and Tumaco basins, on the Colombian Pacific. Qualitative and quantitative analyses of the coccoliths showed changes in the relative abundances and the state of preservation in the two basins. The examined sediments were characterized by the coccoliths Gephyrocapsa oceanica, Gephyrocapsamuellerae, Gephyrocapsa <3 μm, Emiliania huxleyi, Calcidiscus leptoporus and Helicosphaera carteri, which presented abundances higher than 2 %. We also identified a minority assemblage (<2%) constituted by Ceratolithus spp., Coccolithus pelagicus, Florisphaera profunda,Helicosphaera princei, Helicosphaera sellii, Helicosphaera wallichii and Pontosphaera spp. together with reworked specimens of Reticulofenestra spp, Sphenolithus spp. and Discoaster spp. The recovery of E. huxleyi as part of the assemblage indicates that the studied sediments are younger than the biozone NN21, covering an age range of Middle Pleistocene (Ionian). The number of coccoliths per gram (cc/g) was calculated, demonstrating an average of 5.7x106 cc/g and 1.2x107 cc/g for Chocó and Tumaco basins, respectively. In order to interpret the causes of this variance, we performed a multivariate redundancy analysis (RDA), showing that the distance to the coastline is the controlling factor of the fluctuations of the relative abundances and distribution of the coccoliths in both basins.

Two New Species of Recent and Upper Holocene Coccolith-agglutinated Foraminifera from the North Icelandic Shelf, North Atlantic

Two new coccolith-agglutinated foraminiferal species, Pseudobolivina islandica n. sp. and Haplophragmoides atlanticus n. sp., are described from Recent and Upper Holocene sediments at Húnaflóaáll on the North Icelandic shelf. Specimens of the two species have been found only in the small (63–106 µm) fraction using the wet-counting method. This method allows preservation of these fragile tests, which are predominantly composed of coccoliths, mainly of the species Coccolithus pelagicus (Wallich, 1877).

O Pliocénico de Pombal (Bacia do Mondego, Portugal Oeste): biostratigrafia, paleoecologia e paleobiogeografia

No presente trabalho são apresentados dados palinológicos inéditos da importante sequência do Pliocénico português em Pombal. Em paralelo, conjugando os dados dos vários proxies paleontológicos estudados nesta sequência, é feito o ponto da situação do conhecimento sobre nanofósseis calcários e associações de fósseis de moluscos, nomeadamente no que concerne ao seu significado biostratigráfico, paleoecológico e paleobiogeográfico. No tocante à Palinologia, a investigação dos níveis fossilíferos do Pliocénico da região em estudo evidencia uma microflora de carácter mesófilo. A presença de Taxodiaceae substituindo táxones mais termófilos como Cyrillaceae / Clethraceae indicaria descida da temperatura relativamente ao Zancleano, bem patente na sequência de Rio Maior. Na secção média da camada lignitosa (sondagem P1) a presença de Symplocos, táxon megamesotérmico, pressupõe uma ligeira subida de temperatura. O estudo palinológico da sequência representada na sondagem F58 da Bacia de Rio Maior demonstra que ela abrange o Zancleano e o Placenciano; a microflora de Pombal aqui descrita e discutida é correlacionável com o topo do conjunto esporo-polínico F da referida sequência, posicionando-se no topo do Zancleano ou na metade inferior do Placenciano ante 3,0 Ma. Em termos do significado das associações de nanofósseis calcários ricas em Coccolithus pelagicus s.l. é proposta uma interpretação, não baseada em condições paleoambientais subpolares oceânicas, mas sim em condições de afloramento costeiro (de upwelling) persistente e maior paleoprodutividade oceânica ao largo da costa ocidental da Ibéria de então. A associação de moluscos gastrópodes indica ambiente marinho pouco profundo, de salinidade normal e temperaturas subtropicais. Esta associação de gastrópodes sugere correlação com a Mediterranean Pliocene Molluscan Unit 1 do Mediterrânico, i.e., com uma idade pliocénica ante 3,0 Ma. A conjugação dos dados dos nanofósseis calcários e dos moluscos sugere para os níveis fossilíferos marinhos pliocénicos da região de Pombal um posicionamento cronostratigráfico abrangendo desde o topo do Zancleano até à metade inferior do Placenciano, desde cerca dos 3,70-3,61 Ma aos 3,0 Ma, ou mesmo apenas até aos 3,52 Ma, se se tiverem em conta dados dados isotópicos de 87Sr/86Sr.

Bacterial Diversity Associated with the Coccolithophorid AlgaeEmiliania huxleyiandCoccolithus pelagicusf.braarudii

Coccolithophores are unicellular calcifying marine phytoplankton that can form large and conspicuous blooms in the oceans and make significant contributions to oceanic carbon cycling and atmospheric CO2regulation. Despite their importance, the bacterial diversity associated with these algae has not been explored for ecological or biotechnological reasons. Bacterial membership ofEmiliania huxleyiandCoccolithus pelagicusf.braarudiicultures was assessed using cultivation and cultivation-independent methods. The communities were species rich compared to other phytoplankton cultures. Community analysis identified specific taxa which cooccur in all cultures (MarinobacterandMarivita). Hydrocarbon-degrading bacteria were found in all cultures. The presence of Acidobacteria, Acidimicrobidae,Schlegelella, andThermomonaswas unprecedented but were potentially explained by calcification associated with coccolith production. One strain of Acidobacteria was cultivated and is closely related to a marine Acidobacteria isolated from a sponge. From this assessment of the bacterial diversity of coccolithophores, a number of biotechnological opportunities are evident, from bioprospecting for novel taxa such as Acidobacteria to helping understand the relationship between obligate hydrocarbonoclastic bacteria occurrence with phytoplankton and to revealing bacterial taxa that have a specific association with algae and may be suitable candidates as a means to improve the efficiency of mass algal cultivation.

Biogeochemical implications of comparative growth rates of <i>Emiliania huxleyi</i> and <i>Coccolithus</i> species

Coccolithophores are a diverse and biogeochemically important group of phytoplankton in terms of the production and export of calcite, yet the comparative physiology and ecology of species other than the ubiquitous Emiliania huxleyi is poorly understood. Despite assumptions that Emiliania huxleyi is a fast growing species, we found it had comparable growth rates (0.16–0.85 d−1) with strains of Coccolithus pelagicus and Coccolithus braarudii when grown under identical temperature and light conditions. A recently isolated Arctic strain of C. pelagicus (RCC4092) exhibited only a 12% slower growth rate, on average, than a recently isolated Arctic strain of E. huxleyi (RCC3533), over a temperature range of 6–12 °C. Established temperate strains of E. huxleyi and C. braarudii (RCC1228 and RCC1198) exhibited a slightly larger difference in growth rates, with E. huxleyi growing 28% faster on average than C. braarudii over a temperature range of 12–19 °C. Coupled with the 30–80 times higher cellular calcite content of C. pelagicus and C. braarudii compared to E. huxleyi, this suggests that Coccolithus species could be major calcite producers in mixed populations. The relative abundance of coccolithophore species is key for determining which species will dominate calcite production in mixed communities growing at similar rates. Field samples from the North Atlantic show that C. pelagicus is in a high enough relative abundance in 69% of samples collected in the spring and summer of 2010 to be a larger source of calcite production than E. huxleyi.

High temperature decreases the PIC / POC ratio and increases phosphorus requirements in <i>Coccolithus pelagicus</i> (Haptophyta)

Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon through photosynthesis (POC production) and into particulate inorganic carbon through calcification (PIC production). As calcification produces a net release of CO2, the ratio of PIC to POC production determines whether coccolithophores act as a source (high PIC / POC) or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and high temperature on the physiology and the PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large and heavily calcified species is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. One of the subspecies was subjected to a 5 °C temperature increase from 10 °C to 15 °C, which did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. This temperature increase reduced the PIC / POC ratio by 40–60%, whereas the PIC / POC ratio did not differ between P-limited and nutrient-replete cultures when the subspecies were grown near their respective isolation temperature. Both P-limitation and elevated temperature significantly increased coccolith malformations. Our results suggest that a temperature increase may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, thus favouring CO2 sequestration over release. It seems unlikely that P-limitation by itself causes changes in the PIC / POC ratio in this species.