Concentrations of suspended particulate organic carbon in the tidal Yorkshire Ouse River and Humber Estuary

Data are presented for particulate organic carbon (POC) and particulate nit rogen (PN) concentrations in the Humber Estuary and tidal River Ouse Estuar y. The POC data were derived from approximately monthly surveys and are con sistent with data reported for suspended particulate matter (SPM) in the no n-tidal River Ouse (the freshwater river) and with SPM, or bed sediments, i n estuarine ecosystems such as the Mississippi, Delaware, San Francisco Bay , Tolo Harbour, the Vellar Estuary and Cochin Backwater, as well as the Loi re, Gironde, Ems and Tamar Estuaries. Relative to the dry weight of SPM, th e Humber-averaged organic carbon and nitrogen percentages during the year F ebruary 1995-March 1996 were 2.6 + 0.6% (mean and S.D.) and 0.21 +/- 0.04%, respectively. The ratio of Humber-averaged POC to Humber-averaged PN was 1 3 +/- 3. Higher POC levels were observed near the Humber's mouth and in the adjacent coastal zone during 'bloom' conditions, and in the upper estuarin e reaches during large, winter and springtime freshwater inflows. At these times of high runoff, the POC content of SPM increased progressively up-est uary from the coastal zone to the tidal River Ouse. When inflows became ver y low, during late spring to early autumn of 1995, both the freshwater-salt water interface (FSI) and the strengthening turbidity maximum (TM) moved fu rther up-estuary and the POC content of SPM in the upper reaches of the Ous e became lower compared with that immediately down-estuary. This led to a p oorly defined POC maximum near the confluence of the Humber, Ouse and Trent , before POC eventually decreased again towards the coastal zone. The lower POC contents in the upper estuarine reaches of the tidal Ouse may have bee n partly due to POC respiration by heterotrophic bacteria attached to SPM w ithin the TM, consistent with the severe oxygen depletion observed there du ring high turbidity, summertime spring tides. (C) 2000 Elsevier Science B.V . All rights reserved.