Pulsing versus constant supply of nutrients (N, P and Si): effect on phytoplankton, mesozooplankton and vertical flux of biogenic matter

Authors

  • Camilla Svensen Norwegian College of Fishery Science, University of Tromsø
  • Jens C. Nejstgaard Department of Fisheries and Marine Biology, University of Bergen
  • Jorun K. Egge Department of Fisheries and Marine Biology, University of Bergen
  • Paul Wassmann Norwegian College of Fishery Science, University of Tromsø

DOI:

https://doi.org/10.3989/scimar.2002.66n3189

Keywords:

nutrient pulsing, new and regenerated production, Gyrodinium aureolum, sedimentation, mesocosm

Abstract


An experiment with eight vertically stratified seawater enclosures of 27 m3 (depth 9.3 m, diameter 2 m, 90% penetration of PAR) was run in order to test whether pulsed addition of nutrients may cause: 1, higher primary production; 2, higher build-up of phytoplankton biomass; 3, larger temporal mismatch between herbivores and phytoplankton biomass; and 4, higher sedimentation rates, distinguishing in each case between silicate and non-silicate fertilised systems. Nitrate and phosphate were added to all enclosures (NP), while silicate was added to four of the enclosures (NPS). Each enclosure received the same total amount of nutrients, but the nutrients were supplied at four different intervals ranging from one single load to continuous additions. Spring bloom-like systems developed where nutrients were added in one or two pulses as they were characterised by high primary production, high suspended biomass of chlorophyll a (Chl a) and particulate organic carbon (POC) and high sedimentation rates. In contrast, the seawater enclosures receiving nutrients about every third day or in a continuous supply resembled regenerated systems with low concentrations of suspended Chl a and POC and with low and stable loss rates. Due to a typical autumn inoculum with dominance of dinoflagellates and flagellates, diatoms did not dominate the NPS enclosures. The only significant effect of the silicate addition was higher vertical flux of particulate organic nitrogen in the NPS enclosures, and higher microzooplankton biomass. The mesozooplankton did not show responses to the different frequencies of nutrient additions. However, accumulation of mesozooplankton biomass was higher in the NP-mesocosms, probably reflecting better feeding conditions. We conclude that the frequency of nutrient additions had a stronger influence on the development of the phytoplankton and vertical flux of carbon than the +/- silicate treatment in this experiment.

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Published

2002-09-30

How to Cite

1.
Svensen C, Nejstgaard JC, Egge JK, Wassmann P. Pulsing versus constant supply of nutrients (N, P and Si): effect on phytoplankton, mesozooplankton and vertical flux of biogenic matter. scimar [Internet]. 2002Sep.30 [cited 2021Dec.2];66(3):189-203. Available from: https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/579

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