The Breton Sound estuary acted as a source for
NH4. This was most likely caused by the regeneration
of NH4 by the decomposition of organic matter
(Kemp and Boynton 1984), as well as reduction
of NO,, + NO3 to NH4 (Sorenson 1978). Bacteria
and fungi decompose organic material to obtain
energy and in the process release nutrients in dissolved
organic form (Day et al. 1989). Numerous
studies have shown the net mobilization of NH 4 by
benthic sediments (Koike and Hattori 1978; Callender
and Hammond 1982; Teague et al. 1988).
The relatively shallow water depths, rapid settling
rates and rapid bacterial utilization result in fairly
short residence times for organic material in estuarine
waters (Moran and Hodson 1989). Therefore,
much of the regeneration of nutrients probably
takes place on or in the sediments, which is
where NH 4 regeneration is highest (Blackburn
1979).