Interviews de Pierre Lejeune (Directeur de la STARESO), Cécile Guieu (Directrice de Recherche au CNRS) et Frédéric Gazeau (Chargé de Recherche au CNRS / Chef de Projet) dans le cadre de la campagne Medsea Stareso 2012.
Archive for July 6th, 2012
Permian lysocline shoaling and ocean acidification along NW Pangea led to carbonate eradication and chert expansionPublished 6 July 2012 Science Leave a Comment
The Upper Carboniferous to Upper Permian deposits of the Sverdrup Basin (Arctic Canada) record a transition from carbonate to silica dominated shallow shelf ecosystems. Chert expansion started during the latest Carboniferous in distal deep-water slope environments when prolific warm-water, photozoan carbonate factories developed on the adjacent shallow shelves. A shift to heterozoan factories during the Sakmarian–Artinskian was caused by the introduction of cooler water in response to paleoceanographic changes along NW Pangea. By Kungurian time, heterozoan carbonate factories narrowed substantially while hyalosponge factories had expanded well into the mid shelves. A brief return to widespread heterozoan carbonate sedimentation occurred during the Wordian, followed by further encroachment of shallow shelves by biosiliceous factories during the Capitanian and Wuchiapingian. A major drop in relative rates of carbonate sediment accumulation with time suggests both carbonate and biosiliceous factories were under considerable stress prior to the Late Permian Extinction event. It is proposed that Sverdrup Basin waters became progressively more acidic in response to build up of atmospheric CO2 throughout the Permian which led to a gradual shoaling of the lysocline and the calcite compensation depth, which was amplified by upwelling along the northwestern margin of Pangea. Ocean acidification initiated in response to amalgamation of the Pangea supercontinent which inhibited the silicate weathering-response through development of thick protective soil blankets. A temperature shock associated with the extinction event led to a major fall of the lysocline allowing carbonates to resume accumulation in spite of low pH conditions. The subsequent die off of terrestrial vegetation, stripping of soil cover, widespread continental erosion and repeated exposures of fresh rock surfaces associated with a major base level shift allowed silicate weathering to restart and drive oceans back to carbonate saturation.
Workshop on U.K. – U.S. research collaboration concerning the ecosystem level effects of ocean acidificationPublished 6 July 2012 Meetings , Science Leave a Comment
A small workshop (limited to ~25 participants) has been organized to explore approaches to assess the effects of ocean acidification on the structure and function of ecosystems, and to foster collaboration between U.K. and U.S. researchers. This workshop will be convened following the Oceans in a High CO2 World Symposium this fall (September 24-27, 2012) in Monterey, CA.
CO2 enrichment and reduced seawater pH had no effect on the embryonic development of Acropora palmata (Anthozoa, Scleractinia)Published 6 July 2012 Science Leave a Comment
Tags: biological response, corals, laboratory, morphology, North Atlantic, reproduction
The effects of decreased pH, caused by carbon dioxide (CO2) dissolution in seawater (known as ocean acidification (OA)), on the development of newly fertilized eggs of the Caribbean reef-building coral, Acropora palmata, was tested in three experiments conducted during the summers of 2008 and 2009 (two repeats). Three levels of CO2 enrichment were used: present day conditions (400 µatm, pH 8.1) and two CO2-enriched conditions (700 µatm, pH 7.9, and 1000 µatm, pH 7.7). No effects on the progression or timing of development, or embryo and larval size, were detected in any of the three experimental runs. The results show that the embryos and larvae of A. palmata are able to develop normally under seawater pH of at least 0.4 pH units lower than the present levels. Acropora palmata larvae do not usually begin to calcify after settlement, so this study only examined the non-calcifying part of the life cycle of this species. Most of the concern about the effects of OA on marine organisms centers on its effect on calcification. Negative effects of OA on the embryonic development of this species were not found and they may not manifest until the newly settled polyps begin to calcify.