Plankton composition and biomass development: a seasonal study of a semi-intensive outdoor system for rearing of turbot

Hans Henrik Jakobsen, Per Meyer Jepsen, Elisa Blanda, Niels O. G. Jørgensen, Aliona Novac, Kirsten Engell-Sørensen, Benni Winding Hansen

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Plankton food web dynamics were studied during a complete production season in a semi-intensive land-based facility for rearing of turbot (Scophthalmus maximus) larvae. The production season was divided into three production cycles of 3–5 weeks. Phytoplankton biomass (using chlorophyll a as biomass proxy) peaked in each production cycle. However, the maximum biomass decreased from spring (18 lg chlorophyll a L-1) to fall (ca. 7 lg chlorophyll a L-1), simultaneous with a decline in the concentration of dissolved nitrogen in the inoculating water. During the three production cycles, we observed decreasing copepod nauplii concentration
from spring to fall in the rearing tanks. The decreasing nitrogen gave increasing carbon to chlorophyll a ratio in the seston (from 23 in spring to 73 in fall). The pool
of free amino acids in seston was constant. We suggest that the decreasing nitrogen input in the inoculating water reduces the quality of the phytoplankton and thus the growth potential of the prey for fish larvae, copepods.
TidsskriftAquaculture Nutrition
Udgave nummer6
Sider (fra-til)1239-1250
Antal sider12
StatusUdgivet - 6 dec. 2016

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