Changes in carbon stock due to an expansion of Spartina spp. marshes at the mouth of the Maldonado Channel, Bahía Blanca Estuary, Argentina.

MAZZON, C.; PELAEZ, M.R.,; MOLINA, L.M.; PRATOLONGO, P.D.; PERILLO, G.M.E.

Bahía Blanca

Congreso; ECSA 44: SCIENCE AND MANAGEMENT OF ESTUARIES AND COASTS: A TALE OF TWO HEMISPHERES; 2008

Estuarine Coastal Science Association-Instituto Argentino de Oceanografía

During the past 50 years, an expansion of Spartina alterniflora and S. densiflora marshes has been described at different sites inthe Bahía Blanca Estuary. In this work, we evaluated changes in the area covered by S. alterniflora, S. densiflora and S. perennismarshes at the mouth of the Maldonado channel. We used aerial photographs from the area taken in 1967, 1991, and 1996, whichwere rectified and georeferenced. On each date, boundaries of the different vegetation zones were digitized, and the total area ofeach community was estimated. Field work to asses the above and belowground biomass, as well as soil carbon content on eachtype of marsh was carried out at the end of the growing season, in April 2008. Spartina spp. marshes appeared in the area after1967, increasing in area up to 17.41 and 6.79 ha (S. alterniflora and S. densiflora, respectively). The observed expansion occurredby replacement of former S. perennis marshes and mudflats. A general retreat of S. perennis marshes (a total loss of 26.77 ha) wasobserved due to a landward migration of mudflats. In the carbon balance, a total amount of 4682 tons of dry matter presently standsin the area as aerial living, standing dead, and belowground biomass, compared to 1121 tons in 1967. Organic mat ter stored in soil,in turns, changed from 3 to 16 % of soil dry weight in S. densiflora marshes formerly covered by S. perennis, and from 3 to 9 % in S.alterniflora marshes formerly covered by mudflats.