Methane release from the southern Brazilian margin during the last glacial.

Seafloor methane release can significantly affect the global carbon cycle and climate. Appreciable quantities of methane are stored in continental margin sediments as shallow gas and hydrate deposits, and changes in pressure, temperature and/or bottom-currents can liberate significant amounts of this greenhouse gas. Understanding the spatial and temporal dynamics of marine methane deposits and their relationships to environmental change are critical for assessing past and future carbon cycle and climate change. Here we present foraminiferal stable carbon isotope and sediment mineralogy records suggesting for the first time that seafloor methane release occurred along the southern Brazilian margin during the last glacial period (40-20 cal ka BP). Our results show that shallow gas deposits on the southern Brazilian margin responded to glacial-interglacial paleoceanographic changes releasing methane due to the synergy of sea level lowstand, warmer bottom waters and vigorous bottom currents during the last glacial period. High sea level during the Holocene resulted in an upslope shift of the Brazil Current, cooling the bottom waters and reducing bottom current strength, reducing methane emissions from the southern Brazilian margin.

Phylogenetic placement of Cibicidoides wuellerstorfi (Schwager, 1866) from methane seeps and non-seep habitats on the Pacific margin.

Benthic foraminifera are among the most abundant groups found in deep-sea habitats, including methane seep environments. Unlike many groups, no endemic foraminiferal species have been reported from methane seeps, and to our knowledge, genetic data are currently sparse for Pacific deep-sea foraminifera. In an effort to understand the relationships between seep and non-seep populations of the deep-sea foraminifera Cibicidoides wuellerstorfi, a common paleo-indicator species, specimens from methane seeps in the Pacific were analyzed and compared to one another for genetic similarities of small subunit rDNA (SSU rDNA) sequences. Pacific Ocean C. wuellerstorfi were also compared to those collected from other localities around the world (based on 18S gene available on Genbank, e.g., Schweizer et al., 2009). Results from this study revealed that C. wuellerstorfi living in seeps near Costa Rica and Hydrate Ridge are genetically similar to one another at the species level. Individuals collected from the same location that display opposite coiling directions (dextral and sinstral) had no species level genetic differences. Comparisons of specimens with genetic information available from Genbank (SSU rDNA) showed that Pacific individuals, collected for this study, are genetically similar to those previously analyzed from the North Atlantic and Antarctic. These observations provide strong evidence for the true cosmopolitan nature of C. wuellerstorfi and highlight the importance of understanding how these microscopic organisms are able to maintain sufficient genetic exchange to remain within the same species between seep and non-seep habitats and over global distances.

Video endoscopic oro-nasal visualisation of the anterior wall of maxillary sinus: a new technique.

The anterior wall of the maxillary sinus represents a blind spot in maxillary sinus endoscopic surgery because of the absence of proper visualisation and instrumentation to reach it. The aim of this study was to validate a new approach through the oral cavity into the nose with a flexible video endoscope (oro-nasal endoscopic approach; ONEA) to visualise the entire anterior maxillary wall including the anteromedial angle. We started from a dried bone cadaver model, and then dissected fresh-frozen cadavers. The maxillary sinus was explored with a rigid and a flexible endoscope entering from the nose. Next, a flexible endoscope was introduced through the mouth and back up through the choana, it accessed the maxillary middle antrostomy, entering inside the sinus and looking at the anterior wall. A small ruler inserted inside the sinus demonstrated all the angles visualised. The new ONEA technique allows complete visualisation of the anterior wall of the maxillary sinus with inspection of all blind spots. It is therefore possible to detect lesions that would normally not be visible with a normal rigid endoscope. We demonstrate the validity of a novel technique that allows visualisation of the infero-medial angle of the anterior wall of the maxillary sinus.