Department or Program



This thesis investigates carbon source and stocks in salt marshes and seagrass beds in the Patos Lagoon estuary, the largest choked lagoon in the world, located in Southern Brazil. The study was conducted in the mesohaline region, at three shallow shoals. At each shoal, three sediment cores (50 cm deep) and plant biomass samples (aboveground and belowground) were collected along a transect line, spanning from the marsh to seagrass beds or unvegetated sediments (total = 9 sediment cores). The 50cm cores were subsampled and analyzed for organic carbon and nitrogen content, C/N ratios, and the isotope ratios of 13C/12C, and 15N/14N. Geochemical data in marsh sediments generally reflect the overlying vegetation indicating that the carbon source is largely from the in situ vegetation. Seagrass and tidal flat sediments have similar isotopic signatures and likely represent a mix carbon source of seagrass, phytoplankton, and macroalgae. Total carbon stocks for marshes (50cm depth) range from 97 to 221 MgC/ha. Seagrasses and tidal sediments have similar values and range from 9 to 57MgC/ha. These estimates are comparable to global values and indicate the importance of these ecosystems as carbon sinks. Initial rough calculations of ecosystem carbon stocks for the total area of marshes and seagrass beds in Patos Lagoon are 2,800 to 13,000MgC and 800 to 2,000 MgC, respectively. The size of these stocks emphasize the fact that these ecosystems are significant uncounted carbon sinks in Brazil that should be conserved and potentially utilized in Brazil’s active carbon market.

Level of Access

Open Access

First Advisor

Johnson, Beverly

Date of Graduation

Spring 5-2016

Degree Name

Bachelor of Science

Number of Pages


Open Access

Available to all.