Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds Palma Bay, NW MediterraneanReport as inadecuate

Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds Palma Bay, NW Mediterranean - Download this document for free, or read online. Document in PDF available to download.

1 Unité d-Océanographie Chimique B5 2 LOV - Laboratoire d-océanographie de Villefranche 3 IMEDEA CSIC-UIB 4 Département des Sciences Biologiques Montréal

Abstract : Planktonic and benthic incubations bare and Posidonia oceanica vegetated sediments were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma Mallorca, Spain. Results showed a contrast between the planktonic compartment, which was on average near metabolic balance -4.6±5.9 mmol O2 m-2 d-1 and the benthic compartment, which was autotrophic 17.6±8.5 mmol O2 m-2 d-1. During two cruises in March and June 2002, planktonic and benthic incubations were performed at several stations in the bay to estimate the whole-system metabolism and to examine its relationship with partial pressure of CO2 pCO2 and apparent oxygen utilisation AOU spatial patterns. Moreover, during the second cruise, when the residence time of water was long enough, net ecosystem production NEP estimates based on incubations were compared, over the Posidonia oceanica meadow, to rates derived from dissolved inorganic carbon DIC and oxygen O2 mass balance budgets. These budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the planktonic heterotrophy in shallow waters relative to the maximum depth of the bay 55 m. This generated a horizontal gradient from autotrophic or balanced communities in the shallow seagrass-covered areas, to strongly heterotrophic communities in deeper areas of the bay. It seems therefore that, on an annual scale in the whole bay, the organic matter production by the Posidonia oceanica may not be sufficient to fully compensate the heterotrophy of the planktonic compartment, which may require external organic carbon inputs, most likely from land.

Author: F. Gazeau - C. M. Duarte - J.-P. Gattuso - C. Barrón - N. Navarro - S. Ruiz - Y. T. Prairie - M. Calleja - B. Delille - M. Frank

Source: https://hal.archives-ouvertes.fr/


Related documents