Biogeochemistry and dynamics of settling particle fluxes at the Antikythira Strait (Eastern Mediterranean)

For the first time, a 12-month trap experiment was conducted on both sides of the strait between Crete and Antikythira Island (Eastern Mediterranean S ea) from June 1994 to June 1995 as part of the PELAGOS experiment. Analyses of major chemical constituents, including carbohydrates and stable lead is otopes and Scanning Electron Microscope studies were performed on the trap samples. Total mass fluxes varied between 1 and 1273 mg m(-2) d(-1). The lo west fluxes observed were in summer and autumn 1994, when stratification of the water column was at its deepest. In general, mass fluxes exhibited ver y low values throughout this experiment confirming the strong oligotrophy o f this area. The mean contents of the major constituents (carbonates, opal, lithogenic fraction) were quite similar during the survey and between trap s, with the exception of organic carbon contents, which were highest (7-10% ) in summer 1994, i.e. during the period of lowest mass fluxes. During the first 6-month deployment (summer-autumn 1994) there was an important mass f lux peak, which was depleted in organic carbon, at the Ionian near-bottom t rap. This event coincided with a violent wind episode, which may have cause d the resuspension of particles, which were then transported down the steep continental slope on the Ionian side of the strait. A smaller peak in mass flux occurred at the Aegean near-bottom trap, coincident with rainfall. Bo th these events indicate that environmental factors can control flux variat ions in an oligotrophic environment. During the second 6-month deployment ( winter-spring 1995) there was another important increase in mass fluxes, wh ich occurred at all three traps, although in the Ionian traps mass flux pea ks were delayed by one to two sampling intervals. The distance between the two mooring sites gives a rough estimate of a minimum horizontal advection speed of 2 cm s(-1) for this particulate transfer from the Aegean to the Io nian area. This estimate is in good agreement with the measured current vel ocities. (C) 2000 Elsevier Science Ltd. All rights reserved.