Flows of nitrogen in a mesocosm experiment in the Baltic Sea
| Autor: | Fred Sörensson, Elisabeth Sahlsten, Karin Pettersson, Johanne-Sophie Selmer |
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| Rok vydání: | 1989 |
| Předmět: | |
| Zdroj: | Marine Ecology Progress Series. 58:77-88 |
| ISSN: | 1616-1599 0171-8630 |
| DOI: | 10.3354/meps058077 |
| Popis: | N~trogen transformations in a Ballc Sea plankton community were studied in a mesocosm (100 m3) using additions of initially "N labelled ammonium and subsequently unlabelled nitrate to the entire mesocosm. Labelling of different size fractions during the experiment showed that there was a temporal difference in labelling peaks between fractions dominated by producers and consumers, with the latter showing a lag of 30 to 80 h. The size fraction 12-35 pm responded fastest to "N labelling and also attained the highest atom O/ O IsN. The amount of recovered in particulate, dissolved and sedimented nitrogen decreased with time, and only 53 % of the amount initially present was detected after 12 d of sampling. This was probably due to incomplete capture of sedimenting material. After 10 d. 14 % of the added ' 5 ~ could be recovered in the total dissolved nitrogen. The C/N ratio of both suspended and sedimented material decreased during the experiment. The value obtained for the sediment was always higher than the value noted for suspended material. A method is described for determining nutrient uptake and regeneration in the presence of an existent label. The uptake determinations showed that the order of importance of the nitrogenous nutrient sources was ammonium > urea > nitrate, except after the nitrate addition, when nitrate uptake dominated. The rates of ammonium regeneration showed a sharp increase 40.5 h after the labelling of the mesocosm, and after the maximal labelling of the size fraction < 35 pm, presumably due to an increased grazing pressure. On average, rates of ammonium regeneration were 50 % higher than those of ammonium uptake. |
| Databáze: | OpenAIRE |
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