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Revista chilena de historia natural

Print version ISSN 0716-078X

Abstract

DANERI, GIOVANNI. A study of the vertical flow of carbon and nitrogen in controlled aquatic environments at the Knebel Bay, Denmark, with the use of the stable isotopes of nitrogen and carbon (15N y 13C). Rev. chil. hist. nat. [online]. 2001, vol.74, n.3, pp.515-522. ISSN 0716-078X.  http://dx.doi.org/10.4067/S0716-078X2001000300002.

Stable isotopes were used as tracers to characterize and quantify the downward flux of carbon and nitrogen. The experiments were conducted in Knebel bay, Denmark (56 08' N, 10 11' E), in two controlled aquatic environments (mesocosm type). The addition of inorganic nutrients to the mesocosms stimulated a bloom of the non-toxic flagellate Prorocentrum minimum. A similar pattern in the concentration of chlorophyll a (Chl-a), particulate organic nitrogen (PON) and particulate organic carbon (POC) was observed in both mesocosms. The elevated nutrient conditions resulted in low isotopic discrimination, this was reflected in low d13C values of the suspended and sediment POC. The uncoupling between the peaks of PON, Chl-a and POC, as well as the rapid assimilation of the added nitrate (in less than three days) and a changing C/N ratio indicate that P. minimum has a great ability to assimilate inorganic nitrogen. The C/N ratio reached a minimum at the beginning of the experiment increasing later, once nitrate depletion was reached. The sedimentation of new nitrogen during this study was 10-11 % of the total originally added to the water column. No massive sedimentation of P. minimum was observed once the nitrate added to the mesocosms was utilized

Keywords : stable isotopes; sedimentation; trophic structure; Prorocentrum minimum.

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