ISSN:
1573-5117
Keywords:
Oxygen
;
carbon
;
respiration
;
sediment
;
Kattegat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Sediment and seston oxygen consumption rates below the sharp halocline in the south-eastern part of the shallow Kattegat were measured and compared to calculated rates of carbon addition through the halocline. The mean rate of decrease in deep-water oxygen concentrations between March and September 1988 was 1.0 ml O2 M−3 h−1. Measurements of benthic oxygen uptake using laboratory-incubated sediment cores from depths ≥ 30 m gave a mean value of 7.8 ml O2 m−2 h−1. Below-halocline water (from 20 m, 30 m and 1 m above bottom) incubated in bottles showed oxygen consumption rates varying from ≤ 0.5 ml O2 m −3 h−1 in March to 2.8 ml O2 M−3 h-1 in late August. The sum of benthic and deep-water oxygen consumption was equivalent to a mean oxygen decrease rate of 1.7 ml O2 m−3 h−1 below the halocline. Of the total oxygen consumption below the halocline 65% was due to oxygen up-take in the water and 35% was due to benthic oxygen consumption. The sum of oxygen consumption measured in sediment cores and in bottles corresponds to a carbon utilisation of 80.1 g C m−2 (respiratory quotient (RQ), assumed 1.0 and 1.4 for water and sediment, respectively), while the decrease in deep-water oxygen concentration was equivalent to 43.0 g C m−2 (RQ assumed = 1.0). Using published values for the external N loading (including deep-water supply), 15NO3-uptake, 14CO2-uptake in combination with % 15NO3-uptake of total 15N-uptake (nitrate, ammonia and urea) and a Redfield C/N ratio of 6.6, rates of carbon addition (‘new’ or ‘export’ production) through the halocline were calculated to 31.9, 46.7 and 36.3 g C m−2, respectively, with a mean value of 38.3 g C m−2 for the 8 month period March–September. This is somewhat less than the value (50.5 g C m−2) calculated from a published empirical relationship between total and export production. The fact that the calculated carbon addition through the halocline was appreciably less than the carbon equivalent of the measured below-halocline respiration may be an effect of sediment focusing (horizontal transport of sedimenting material to deeper areas), since the bottom area below the halocline is much smaller than the total area of the Kattegat. A lower observed decrease in the oxygen concentration below the halocline compared to the sum of measured sediment and deep-water oxygen consumption on the other hand indicates oxygen supply to below-halocline waters through advection and/or vertical entrainment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00026222
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