Open AccessSeasonal variation in net benthic C‐mineralization in a shallow estuary
Author(s) -
Therkildsen Mette S.,
Lomstein Bente Aa.
Publication year - 1993
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.1993.tb00025.x
Subject(s) - benthic zone , water column , mineralization (soil science) , environmental chemistry , sediment , biology , carbonate , estuary , chlorophyll a , total organic carbon , botany , ecology , chemistry , soil water , paleontology , organic chemistry
Seasonal changes in net benthic C‐mineralization were measured as sediment O 2 uptake, as well as Σ CO 2 flux from the sediment to the water column. Oxygen uptake varied between 26 and 181 mmol m −2 d −1 through the year, and Σ CO 2 efflux varied between 17 and 132 mmol m −2 d −1 . Both parameters were related to temperature, and the Q 10 for O 2 uptake and Σ CO 2 efflux were 2.5 and 2.0, respectively. The Σ CO 2 /O 2 ratio varied between 0.8 and 1.0 during most of the year. The Σ CO 2 /O 2 ratio was, however, less than 0.8 in late summer and autumn, which might be due to reoxidation of accumulated reduced sulfur compounds and carbonate precipitation. Calcium carbonate deposition by molluscs seemed quantitatively important for the Σ CO 2 efflux in September 1990 and August 1991. The Σ CO 2 /O 2 ratio reached a maximum of 1.3 in mid‐April during decomposition of benthic and sedimented microalgae. On an annual basis, all the oxidants which were reduced during anaerobic mineralization (e.g., Mn 2+ , Fe 2+ , HS − ), apparently were reoxidized by O 2 , as illustrated by an annual Σ CO 2 /O 2 ratio of 0.8. Benthic macrofauna stimulated C‐mineralization, indicated by a positive relationship between O 2 uptake and Σ CO 2 efflux rates, respectively, and macrofauna biomass. Sediment chlorophyll‐ a + pheopigment content and C/N ratio served as good indicators both of algal sedimentation from the water column and of the presence of benthic microalgae. The sediment parameters, including the organic carbon and nitrogen content, C/N ratio, and chlorophyll‐ a + pheopigment content, clearly reflected the seasonal variation in sediment mineralization rates. There was a temporal phase displacement between input of organic matter and benthic C‐mineralization, which resulted in a temporary build up of organic matter during periods with high primary production and/or low C‐mineralization (spring, late autumn, winter). The accumulated organic matter was mineralized during periods when the actual supply of organic matter was insufficient (summer, early autumn).