Inter-Research
Aquatic Microbial Ecology

ABSTRACT: Copepod nauplii may be an important intermediary between the 'microbial' and 'classical' pelagic marine food webs. In studies of planktonic food webs, along a trophic gradient from eutrophic harbour through coastal to oligotrophic oceanic waters off Jamaica, West Indies, we investigated bacterivory by nauplii of 11 representative copepod taxa (n = 176 total nauplii) using fluorescently labelled bacteria (FLB) of 0.7 µm³ volume at concentrations of 1.5 to 2.5 x 10⁶ cells ml^-1. Seven taxa consistently ingested FLB: Acartia liljeborgii, Paracalanus spp., Temora stylifera, T. turbinata, Oncaea spp., Undinula vulgaris, Oithona spp.; 4 taxa consistently did not: Centropages velificatus, Clausocalanus spp., Euchaeta marina, and Corycaeus spp. These data, and the observations that naupliar moulting and growth rates were uncoupled from chlorophylla concentrations in any size fraction over the range 0.09 to 4.7 mg m^-3, suggest that nauplii are not food limited even in oceanic waters. Calculations indicate that daily food requirements of oceanic nauplii can be met from a diet of bacteria and picoplankton, but not from a diet of nano- and net-phytoplankton. Naupliar production in oceanic waters is at least 50 to 60% of copepodite production; it appears therefore that the ecological importance of copepod nauplii in oceanic waters has been greatly underestimated.

KEY WORDS: Marine plankton . Nauplius . Bacterivory . Tropical copepods . Microbial food web

Published in AME Vol. 9, No. 2 (1995) on August 31
Print ISSN: 0948-3055; Online ISSN: 1616-1564. Copyright © Inter-Research, Oldendorf/Luhe, 1995