7 research outputs found
Temperature Modulates Coccolithophorid Sensitivity of Growth, Photosynthesis and Calcification to Increasing Seawater pCO2
Increasing atmospheric CO2 concentrations are expected to impact pelagic ecosystem functioning in the near future by
driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and
seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for
possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO2
gradient ranging from ,0.5â250 mmol kg21 (i.e. ,20â6000 matm pCO2) at three different temperatures (i.e. 10, 15, 20uC for
E. huxleyi and 15, 20, 25uC for G. oceanica). Both species showed CO2-dependent optimum-curve responses for growth,
photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and
production rates and modified sensitivities of metabolic processes to increasing CO2. CO2 optimum concentrations for
growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate
temperatures. However, there was a clear optimum shift towards higher CO2 concentrations from intermediate to high
temperatures in both species. Our results demonstrate that the CO2 concentration where optimum growth, calcification and
carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean
acidification at a given temperature can be negative, neutral or positive depending on that strainâs temperature optimum.
This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when
interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of
changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the
future ocean
Giardia duodenalis genotypes and Cryptosporidium species in humans and domestic animals in CĂŽte d'Ivoire: occurrence and evidence for environmental contamination
Giardia duodenalis genotypes and Cryptosporidium species were studied in humans and free-ranging animals living in closed enclaves in CĂŽte dâIvoire. Three hundred and seven stool samples were tested from humans, and 47 from freely roaming domestic animals (dogs, goats, ducks, chickens). Molecular characterization of the isolates was
performed by sequence analysis of a portion of the SSU-rDNA for Giardia and the COWP gene for Cryptosporidium, and a Ë-giardin SYBR-green real-time PCR was also used to confirm the assignment of Giardia isolates to Assemblages. In humans, genotyping of Giardia assigned many of the sequences (43/56 by the SSU-rDNA gene, and 36/61 by the Ë-giardin gene) to Assemblage B. The animal species harboured only zoonotic ssemblages A and B, except for dogs, in which host specific Assemblages C and D were also detected. Cryptosporidium meleagridis, C. parvum and C. hominis were detected in humans,
while among the animals only chickens were found positive for oocysts, identified as C. meleagridis and C. parvum. The results provide further evidence about the role of freeranging
domestic animals living closely with humans in the environmental dissemination
and potential transmission of these anthropozoonotic pathogens to humans
Environmental forcing of phytoplankton in a Mediterranean estuary (Guadiana Estuary, southwestern Iberia): a decadal of anthropogenic and climatic influences
Phytoplankton seasonal and interannual variability in theGuadiana upper estuarywas analyzed during 1996â2005, a period that encompassed a climatic controlled reduction in river flow that was superimposed on the construction of a dam.
Phytoplankton seasonal patterns revealed an alternation between a persistent light limitation and episodic nutrient limitation. Phytoplankton succession, with early spring diatom blooms and summerâearly fall cyanobacterial blooms, was apparently driven by changes in nutrients, water temperature,
and turbulence, clearly demonstrating the role of river flow and climate variability. Light intensity in the mixed layer was a
prevalent driver of phytoplankton interannual variability, and the increased turbidity caused by the Alqueva dam construction was linked to pronounced decreases in chlorophyll a concentration,
particularly at the start and end of the phytoplankton growing period. Decreases in annual maximum and average abundances of diatoms, green algae, and cyanobacteria were
also detected. Furthermore, chlorophyll a decreases after dam filling and a decrease in turbidity may point to a shift from
light limitation towards a more nutrient-limited mode in the near future