9 resultados para 35C
em Publishing Network for Geoscientific
Resumo:
The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon, with tropical sea surface temperatures over 35°C. High-amplitude sea-level changes and positive d18O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New d18O data from the tropical Atlantic show synchronous shifts ~91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap. Even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets, calling into question the common assumption that the poles were always ice-free during past periods of intense global warming.
Resumo:
The eastern Mediterranean is a hotspot of biological invasions. Numerous species of Indo-pacific origin have colonized the Mediterranean in recent times, including tropical symbiont-bearing foraminifera. Among these is the species Pararotalia calcariformata. Unlike other invasive foraminifera, this species has been discovered only two decades ago and is restricted to the eastern Mediterranean coast. Combining ecological, genetic and physiological observations, we attempt to explain the recent invasion of this species in the Mediterranean Sea. Using morphological and genetic data, we confirm the species attribution to P. calcariformata McCulloch 1977 and identify its symbionts as a consortium of diatom species dominated by Minutocellus polymorphus. We document photosynthetic activity of its endosymbionts using Pulse Amplitude Modulated Fluorometry and test the effects of elevated temperatures on growth rates of asexual offspring. The culturing of asexual offspring for 120 days shows a 30-day period of rapid growth followed by a period of slower growth. A subsequent 48-day temperature sensitivity experiment indicates a similar developmental pathway and high growth rate at 28°C, whereas an almost complete inhibition of growth was observed at 20°C and 35°C. This indicates that the offspring of this species may have lower tolerance to cold temperatures than what would be expected for species native to the Mediterranean. We expand this hypothesis by applying a Species Distribution Model (SDM) based on modern occurrences in the Mediterranean using three environmental variables: irradiance, turbidity and yearly minimum temperature. The model reproduces the observed restricted distribution and indicates that the range of the species will drastically expand westwards under future global change scenarios. We conclude that P. calcariformata established a population in the Levant because of the recent warming in the region. In line with observations from other groups of organisms, our results indicate that continued warming of the eastern Mediterranean will facilitate the invasion of more tropical marine taxa into the Mediterranean, disturbing local biodiversity and ecosystem structure.
Resumo:
The cores and dredges described at this site were taken on the SAFARI II cruise from 21 July until 1 September 1981 by the MusÈum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 65 cores, dredges and camera stations were recovered and are available at MNHN for sampling and study.
Resumo:
Following the launch of the "Marion Dufresne 1", first supply ship of the Terres Australes and Antarctiques Françaises and part time oceanographic vessel in the Indian Ocean, a new marine geology program was developped at the Laboratoire de Géologie, MNHN. The first oceanographic cruise of the "Marion Dufresne 1" started in 1973 in the Southwestern Indian Ocean (OSIRIS I cruise). Forty piston-cores recovered nearly 200 m of sediments consisting in the first of the 450 cores of the Indian Ocean collection now deposited at the Museum. L. Leclaire being Director from 1980 to 1991, a multidisciplinary team (including sedimentologists and micropaleontologists) was involved in many oceanographic cruises in the Indian Ocean. Marine sedimentology was developped during annual cruises programs in collaboration with geophysicists, geochemists, and biologists. In 1995, the "Marion Dufresne 2" replaced the initial "Marion Dufresne 1".
Resumo:
In this paper we investigated, for two years and with a bi-monthly frequency, how physical, chemical, and biological processes affect the marine carbonate system in a coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, northern Adriatic Sea, Mediterranean Sea).