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Aquatic Microbial Ecology

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AME 09:165-175 (1995)  -  DOI:

Bacterivory by tropical copepod nauplii: extent and possible significance

Roff JC, Turner JT, Webber MK, Hopcroft RR

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.

Marine plankton . Nauplius . Bacterivory . Tropical copepods . Microbial food web

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