Comparison of Methods for Estimating Annual Productivity of the Copepods Acartia hudsonica and Eurytemora herdmani in Passamaquoddy Bay, New Brunswick

Abstract

Annual productivity of the copepods Acartia hudsonica and Eurytemora herdmani was estimated over a 12-mo period at three sites in Passamaquoddy Bay, New Brunswick. The sites were chosen to represent the range of habitats present in the bay. Samples were collected in vertical hauls of a 64-μm-mesh plankton net. Annual productivity was estimated by three methods. Estimates by the temperature–biomass method were 578–677 kJ∙m−2∙yr−1 for A. hudsonica and 63–173 kJ∙m−2∙yr−1 for E. herdmani. Both the mass-specific and cohort P/B methods yielded productivity estimates comparable with those calculated by the temperature–biomass method for E. herdmani. Acartia hudsonica estimates by the P/B methods were lower. We suspect that the cause of this discrepancy is the incorporation of periods of diapause and nonmaximal growth in estimating a mean biomass value for A. hudsonica. Other temporally abundant copepods observed in the bay included Tortanus discaudatus, Temora longicornis, Pseudocalanus sp., Oithona similis, and Centropages typicus. Total copepod productivity, assuming productivity by the rare species to be proportional to their relative numeric contribution, was estimated to be 800–850 kJ∙m−2∙yr−1. Through comparison of these estimates with previously published estimates, we suggest that copepod productivity in coastal areas may be similar over broad geographic areas.