Seagrass and submerged aquatic vegetation (VAS) habitats off the Coast of Brazil: state of knowledge, conservation and main threats

Seagrass meadows are among the most threatened ecosystems on earth, raising concerns about the equilibrium of coastal ecosystems and the sustainability of local fisheries. The present review evaluated the current status of the research on seagrasses and submerged aquatic vegetation (SAV) habitats off the coast of Brazil in terms of plant responses to environmental conditions, changes in distribution and abundance, and the possible role of climate change and variability. Despite an increase in the number of studies, the communication of the results is still relatively limited and is mainly addressed to a national or regional public; thus, South American seagrasses are rarely included or cited in global reviews and models. The scarcity of large-scale and long-term studies allowing the detection of changes in the structure, abundance and composition of seagrass habitats and associated species still hinders the investigation of such communities with respect to the potential effects of climate change. Seagrass meadows and SAV occur all along the Brazilian coast, with species distribution and abundance being strongly influenced by regional oceanography, coastal water masses, river runoff and coastal geomorphology. Based on these geomorphological, hydrological and ecological features, we characterised the distribution of seagrass habitats and abundances within the major coastal compartments. The current conservation status of Brazilian seagrasses and SAV is critical. The unsustainable exploitation and occupation of coastal areas and the multifold anthropogenic footprints left during the last 100 years led to the loss and degradation of shoreline habitats potentially suitable for seagrass occupation. Knowledge of the prevailing patterns and processes governing seagrass structure and functioning along the Brazilian coast is necessary for the global discussion on climate change. Our review is a first and much-needed step toward a more integrated and inclusive approach to understanding the diversity of coastal plant formations along the Southwestern Atlantic coast as well as a regional alert the projected or predicted effects of global changes on the goods and services provided by regional seagrasses and SAV

Indicateur biologique et variations relatives du niveau de la mer sur les côtes rocheuses de Provence depuis 4 500 ans

Biological evidence of relative sea level rise, during the last 4 500 years, on the rocky coasts of Provence. On the rocky coasts of Provence, biogenic littoral rims develop, built by the coralline Rhodophyte Lithophyllum lichenoides. Remains may be preserved for millenia when submersed in a rising sea environment. These remains can be used as biological indicators of relative sea level variations. The studied stations indicate constant decrease in global speed of relative sea level rise for the last 5 000 years. The Holocene marine transgression seems to stop in Provence around 500 A. D.Les corniches médiolittorales à Lithophyllum lichenoides se développent sur les côtes rocheuses de Provence. Les vestiges de ces bioconstructions peuvent se conserver pendant des milliers d'années. Ils constituent alors des indicateurs biologiques précis des variations relatives du niveau marin. Les stations étudiées indiquent des ralentissements constants des vitesses globales de montée relative du plan d'eau depuis environ S 000 ans. La transgression marine holocène semble s'achever vers 500 ans après J.-C. Nous insistons sur l'absence d'indice de stationnement marin historique supérieur au niveau actuel sur les côtes de Provence.Morhange Christophe, Laborel Jacques, Laborel-Deguen F., Lounnas V., Verrecchia Eric. Indicateur biologique et variations relatives du niveau de la mer sur les côtes rocheuses de Provence depuis 4 500 ans. In: Géologie Méditerranéenne. Tome 20, numéro 2, 1993. pp. 89-100

Late holocene coseismic vertical displacements and tsunami deposits near Kynos, Gulf of Euboea, Central Greece

International audienc

Episodic uplift deduced from Holocene shorelines in the Perachora Peninsula, Corinth area, Greece

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Late-Holocene shoreline changes related to palaeoseismic events in the Ionian Islands, Greece

International audienceA systematic multidisciplinary survey on the coasts of the Ionian Islands, founded on 26 new radiocarbon accelerator mass spectrography (AMS) dates, has revealed the occurrence of sectors which were uplifted (seismo)tectonically during the late Holocene. In Corfu, two uplift movements of about 0.8m each took place in the central part of the island: one of them around 790-400 cal. BC, and also at a more recent, undetermined date. In Levkas, up-and-down tectonic movements of metric order governed late-Holocene relative sea-level changes, at least in the northern part of the island; submergence of at least 2.5 m occurred since 2400 years ago, with a possible spasmodic subsidence around cal. AD 500-700. In Cephalonia, two vertical displacements affected most of the island, around cal. AD 350-710 and in AD 1953; both movements resulted in uplift in the southeastern part of the island. Submergence seems to predominate round Ithaca. Lastly, in Zante, clear evidence of a Holocene crustal block movement is limited to the southeastern peninsula, where an uplift of 0.95 ± 0.15 m took place, probably coseism ically, around the period cal. AD 200-500. The time ranges of uplift in Cephalonia and Zante, and of possible subsidence in Levkas, correspond with a period of regional tectonic paroxysm, between the middle of the fourth century AD and the middle of the sixth century AD; this has already been documented in several areas of the eastern Mediterranean, notably in the Gulf of Corinth, the southern Hellenic arc, Turkey, Cyprus, the Lebanon and Syria