Sizing the carbon sink associated with Posidonia oceanica seagrass meadows using very high-resolution seismic reflection imaging.

Among blue carbon ecosystems, seagrass meadows have been highlighted for their contribution to the ocean carbon cycle and climate change mitigation derived from their capacity to store large amounts of carbon over long periods of time in their sediments. Most of the available estimates of carbon stocks beneath seagrass meadows are based on the analysis of short sediment cores in very limited numbers. In this study, high-resolution seismic reflection techniques were applied to obtain an accurate estimate of the potential size of the organic deposit underlying the meadows of the Mediterranean seagrass Posidonia oceanica (known as 'matte'). Seismic profiles were collected over 1380 km of the eastern continental shelf of Corsica (France, Mediterranean Sea) to perform a large-scale inventory of the carbon stock stored in sediments. The seismic data were ground-truthed by sampling sediment cores and using calibrated seismo-acoustic surveys. The data interpolation map highlighted a strong spatial heterogeneity of the matte thickness. The height of the matte at the site was estimated at 251.9 cm, being maximum in shallow waters (10-20 m depth), near river mouths and lagoon outlets, where the thickness reached up to 867 cm. Radiocarbon dates revealed the presence of seagrass meadows since the mid-Holocene (7000-9000 cal yr BP). Through the top meter of soil, the matte age was estimated at 1656 ± 528 cal yr BP. The accretion rate showed a high variability resulting from the interplay of multiple factors. Based on the surface area occupied by the meadows, the average matte thickness underneath them and the carbon content, the matte volume and total Corg stock were estimated at 403.5 ± 49.4 million m3 and 15.6 ± 2.2 million t Corg, respectively. These results confirm the need for the application of large-scale methods to estimate the size of the carbon sink associated with seagrass meadows worldwide.

bcl-2 expression in plasma cells from neoplastic gammopathies and reactive plasmacytosis: a comparative study.

BACKGROUND AND OBJECTIVE: bcl-2 oncoprotein plays a major physiological role in hemopoietic and non-hemopoietic cells by preventing apoptosis (programmed cell death). Disregulation of this process may be important in oncogenesis and the response to treatment of patients with different hematological malignancies. We have investigated the levels of bcl-2 expression in plasma cells from patients with reactive plasmacytosis (RP), monoclonal gammopathy of unknown significance (MGUS) and multiple myeloma (MM), correlating the bcl-2 expression and clinico-biological features in MM patients. DESIGN AND METHODS: The percentage of bcl-2 (+) plasma cells and levels of bcl-2 protein expression were investigated in 73 patients at diagnosis. Immunofluorescence and immunoenzymatic methods were applied using McAb against bcl-2 protein, and the intensity of protein expression was assessed by both the mean channel fluorescence intensity (MFI) and semiquantitative methods. To evaluate the intensity of bcl-2 expression in proliferating plasma cells, sequential double immunoenzymatic staining with McAb Ki-67 and bcl-2 was applied in 10 patients with MM. Correlations between bcl-2 expression and the clinico-biological features in MM patients were also studied. RESULTS: The proportion of bcl-2 (+) plasma cells was significantly higher in MGUS and MM than in RP (p < 0.001). The intensity of bcl-2 expression in plasma cells (assessed by MFI) was significantly different between all groups studied (p < 0.0001). RP showed lower expression than MGUS and MM patients. MM stage III patients demonstrated higher bcl-2 expression values than MGUS (p < 0.01). According to the proportion of plasma cells expressing Ki-67, patients with a proliferative index (Ki-67+) > 4% showed lower bcl-2 expression than patients with proliferative index < 4% (p < 0.05). Immunocytochemistry showed that plasma cells from RP had a lower intensity of bcl-2 expression than MM (p < 0.001), and double immunostaining Ki-67/bcl-2 demonstrated that the majority of proliferating plasma cells had weak bcl-2 expression. There was no correlation between bcl-2 expression and clinico-biological parameters, response to therapy or overall survival in MM patients. INTERPRETATION AND CONCLUSIONS: Globally, the number of bcl-2 (+) plasma cells and the intensity of protein expression in neoplastic gammopathies are significantly higher than in reactive plasmacytosis and bcl-2 levels tend to increase with disease stage. bcl-2 may be relevant to the pathogenesis of malignant gammopathies, prolonging the survival of plasma cells by preventing apoptosis and increasing the chance of acquiring additional gene defects. bcl-2 expression could also contribute to the resistance to chemotherapy observed in MM disease.