『Abstract
The effect of phytodetritus derived from Phaeocystis sp.
bloom on benthic mineralization processes has been determined
at four intertidal stations along the French coast of the eastern
English Channel. Sites were chosen to offer a diversity of sediment
types, from permeable sandy beach to estuarine mudflats. Sediment
Oxygen demand (SOD) as well as total fluxes of Dissolved Inorganic
Nitrogen (DIN) at the sediment-water interface were determined
by using whole core incubation technique and diffusive fluxes
were predicted from interstitial water concentrations. In the
absence of phytodetritus deposits, a marked gradient of granulometric
characteristics and organic matter contents were observed, and
resulted in more intensive mineralization processes in muddy sediments.
Highly significant correlations (P＜0.05) were evidenced between
SOD and porosity, bacterial biomass, Organic Carbon and Organic
Nitrogen, evidencing the direct link between sediment texture,
organic matter accumulation and microbial activity. The spring
bloom led to a massive input of organic matter in surficial sediments
and mineralization rates significantly increased while higher
DIN release towards the water column was observed. A modification
of the mineralization pathways was evidenced but clearly depended
on the sediment type. With a global view, benthic mineralization
processes in the intertidal zone provided significant a part of
DIN inputs in the coastal zone while water column was depleted
in nutrients.
Keywords: Intertidal; Organic matter mineralization; Phaeocystis
sp.; Sediment-water fluxes』
Introduction
Materials and methods
Site description
Sampling and incubation device
Pore water profiles and predicted flux calculation
Sediment characteristics
Bacteria and macrofaua biomass
Statistics
Results
Hydrological variables
Sedimentary characteristics
Sediment-water fluxes
Pore water profiles and diffusive fluxes
Biological characteristics
Relationship between variables
Discussion
Total versus diffusive fluxes
Spatial variability and sedimentary gradient
Macrofaunal influence
Temporal variability and mineralization processes
Ecological implications of mineralization processes
Conclusions
Acknowledgements
References