Microbiological investigations of the Canadian tundra

Microbial communities were analyzed at 17 sites visited during the expedition Tundra Northwest 1999 (TNW-99) by microscopic analyses (epifluorescence microscopy and image analyses). The data were used to describe the communities of bacteria, fungi and algae in detail by number, biovolume and biomass. Great variability was found, which could be related to organic matter content of soils and features of vegetation patterns. The amounts (numbers and abundance) of organisms and data on microbial biomass are discussed in relation to other polar environments of the Northern and Southern Hemispheres.

Seawater carbonate chemistry and biological processes during experiments with early life stages of the blue mussel Mytilus edulis, 2010

Several experiments have shown a decrease of growth and calcification of organisms at decreased pH levels. There is a growing interest to focus on early life stages that are believed to be more sensitive to environmental disturbances such as hypercapnia. Here, we present experimental data, acquired in a commercial hatchery, demonstrating that the growth of planktonic mussel (Mytilus edulis) larvae is significantly affected by a decrease of pH to a level expected for the end of the century. Even though there was no significant effect of a 0.25-0.34 pH unit decrease on hatching and mortality rates during the first 2 days of development nor during the following 13-day period prior to settlement, final shells were respectively 4.5±1.3 and 6.0±2.3% smaller at pHNBS~7.8 (pCO2~1100-1200 µatm) than at a control pHNBS of ~8.1 (pCO2~460-640 µatm). Moreover, a decrease of 12.0±5.4% of shell thickness was observed after 15d of development. More severe impacts were found with a decrease of ~0.5 pHNBS unit during the first 2 days of development which could be attributed to a decrease of calcification due to a slight undersaturation of seawater with respect to aragonite. Indeed, important effects on both hatching and D-veliger shell growth were found. Hatching rates were 24±4% lower while D-veliger shells were 12.7±0.9% smaller at pHNBS~7.6 (pCO2~1900 µatm) than at a control pHNBS of ~8.1 (pCO2~540 µatm). Although these results show that blue mussel larvae are still able to develop a shell in seawater undersaturated with respect to aragonite, the observed decreases of hatching rates and shell growth could lead to a significant decrease of the settlement success. As the environmental conditions considered in this study do not necessarily reflect the natural conditions experienced by this species at the time of spawning, future studies will need to consider the whole larval cycle (from fertilization to settlement) under environmentally relevant conditions in order to investigate the potential ecological and economical losses of a decrease of this species fitness in the field.

Annotated record of the detailed examination of Mn deposits from the R/V Rig Seismic Cruise 11 (BMR 66) in 1986 over the Great Australian Bight Basin area

Late Cretaceous and younger sediments dredged from the upper continental slope and canyon walls in the Great Australian Bight Basin between 126° and 136°E broadly confirm the stratigraphy which had been established previously from scattered exploration wells. Late Cretaceous to Early Eocene marine and marginal marine terrigenous sediments are overlain by Middle Eocene and younger pelagic carbonate (fine limestone and calcareous ooze). The samples provide the first evidence of truly marine Maastrichtian sedimentation, with abundant calcareous nannoplankton, on the southern margin of the continent. Other samples of interest include Precambrian sheared granodiorite on the upper slope south of Eyre Terrace, Paleocene phosphatic sediment in 'Eucla' Canyon at 128° 30'E, and terrigenous Early Miocene mudstone at 133° 20' and 134° 50'E. The mudstone is of note as an exception to the uniform pelagic carbonate wackestone and ooze which characterise Middle Eocene and younger sedimentation at all other sites. Fragments of alkali basalt lava of unknown age were recovered in 'Eucla' Canyon. Cores are mostly pelagic calcareous ooze, but those from submarine canyons include terrigenous turbidites.