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Title
  • en Population structure, egg production and gut content pigment of large grazing copepods during the spring phytoplankton bloom in the Oyashio region
Creator
    • en Onishi, Yuka
    • en Omata, Aya
    • en Kawai, Momoka
    • en Kaneda, Mariko
Accessrights open access
Subject
  • Other en Copepods
  • Other en Egg production
  • Other en Gut pigment
  • Other en Life cycle
  • Other en OECOS
  • NDC 452
Description
  • Abstract en As a basis for analyzing development of six large grazing copepods (Eucalanus bungii, Metridia pacifica, M. okhotensis, Neocalanus cristatus, N. flemingeri and N. plumchrus) in the Oyashio region, quasi-daily twin-NORPAC net (0.33 and 0.10 mm mesh) hauls were taken through the upper 150 m and 500 m at a station southwest of Hokkaido before (9-14 March) and after (6-30 April) the onset of the phytoplankton bloom in 2007. Based on additional fresh specimens collected from 0-150 m, egg production of E. bungii, M. pacifica and M. okhotensis, and gut pigments of late copepodid stages in each species were evaluated. Total zooplankton biomass was greater from 10 April onward by a factor of 2- to 8-fold the previous levels. This increase of the 0-150 m biomass was caused by development of Neocalanus spp. copepodids and upward migration of resting E. bungii. Egg production of E. bungii peaked on 18 April, while abundance of its nauplii and C1 peaked on 20 and 25 April, respectively. Sex ratio and C6-female gonad maturation index of E. bungii showed new recruitment to C6 during 20-30 April, likely derived from a population that over-wintered as C3 or C4. Egg production and hatchability of M. pacifica and M. okhotensis were highly variable and no temporal trend was detected. Comparison with field abundance data for Metridia spp. suggests that our estimates of egg production and hatchability are too low, despite care with experimental conditions. All the Neocalanus species utilize the bloom as energy for juvenile growth. Neocalanus cristatus developed from C2 through C4, and stage duration of C3 was estimated to be 24 days. Neocalanus flemingeri also developed from Cl through C3, and stage durations of C1 and C2 were estimated to be 7-9 days. Neocalanus plumchrus occurred in small numbers from mid-April onward. The stage duration estimates for Neocalanus spp. are similar to those reported from the high-nutrition southeastern Bering Sea shelf. Gut pigment variation clearly showed nocturnal feeding by Metridia spp., while no diel changes in gut pigment were recognized for E. bungii or Neocalanus spp. The diel changes in gut pigment of Metridia spp. were related to their diel vertical migrations. The calendar of sequential responses of copepods to the phytoplankton bloom is summarized.
Publisher en Elsevier
Date
    Issued2010-09
Language
  • eng
Resource Type journal article
Version Type AM
Identifier HDL http://hdl.handle.net/2115/43806
Relation
  • isVersionOf DOI https://doi.org/10.1016/j.dsr2.2010.03.012
Journal
    • PISSN 0967-0645
      • en Deep Sea Research Part II: Topical Studies in Oceanography
      • Volume Number57 Issue Number17-18 Page Start1679 Page End1690
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Oaidate 2023-07-26