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Marine Ecology Progress Series

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MEPS 331:131-138 (2007)  -  doi:10.3354/meps331131

Supplemental effects of diet mixing on absorption of ingested organic carbon in the marine copepod Acartia tonsa

Peter Thor1,*, Marja Koski2, Kam W. Tang2,3, Sigrún H. Jónasdóttir2

1Göteborg University, Department of Marine Ecology, Kristineberg Marine Research Station, 450 34 Fiskebäckskil, Sweden
2Danish Institute for Fisheries Research, Department of Marine Ecology and Aquaculture, Kavalergården 6, 2920 Charlottenlund, Denmark
3Virginia Institute of Marine Science, Rt. 1208, Greate Road, Gloucester Point, Virginia 23062-1346, USA

ABSTRACT: We investigated increased carbon absorption efficiencies (AEs) as a possible cause for positive effects of diet mixing on copepod egg production rates (EPRs) and hatching success (EHS). Female Acartia tonsa were fed 14C/51Cr dual-labelled Dunaliella tertiolecta (Dun), Amphidinium carterae (Amp), Phaeocystis globosa (Pha), and 3 pairwise 1:1 mixes of the 3 diets. AEs, derived from the ratios of labels in algae and copepod faecal pellets, were 44% on Dun, 37% on Amp, and 49% on Pha, but increased significantly to 61% on Dun + Amp. As a result, EPRs remained low in all tested diets except for Dun + Amp, where it was twice that in the individual diets. Linear multiple regression analysis revealed that EPRs were strongly dependent on the ingestion and absorption of the fatty acids 18:3(n-3) and 22:6(n-3) so that the simultaneous ingestion and absorption of 18:3(n-3) from Dun and 22:6(n-3) from Amp enhanced EPR in the Dun + Amp diet. EHS was low with the Dun diet, which was devoid of 20:5(n-3) and 22:6(n-3). Multiple regression analysis showed that EHS depended on 16:1(n-7) and any or all of 22:6(n-3), 20:5(n-3), or 18:5(n-3).

KEY WORDS: Copepods · Food quality · Absorption efficiency · Diet mixing · Fatty acid composition

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