Changes in carbon stock due to an expansion of Spartina spp. marshes at the mouth of the Maldonado channel, Bahia Blanca estuary, Argentina

MAZON, C.; PELÁEZ, M.R.; MOLINA, L.M.; PRATOLONGO, P.D.; PERILLO. G.M.E.

Bahía Blanca, Argentina

Simposio; ECSA 44 Symposium: Science and management of estuaries and coasts: A tale of two hemispheres; 2008

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