A high frequency time series at Weathership M, Norwegian Sea, during the 1997 spring bloom:the reproductive biology of Calanus finmarchicus

Abstract

The reproductive biology of Calanus finmarchjcus was investigated at a permanent station in the Norwegian Sea (Weathership Stn M, 66" N, 2" E) during a time series between March and June 1997 The temporal development of female abundance, egg production rate and gonad development stage in relation to the phytoplankton production cycle is described Abundance of females, copepodite stage 5 and males as well as female gonad morphology were examlned from MrP2 net samples taken daily from the upper 100 m. Daily egg production rate and number of spawn.ing females we]-e determined from 50 individual females placed in multiwells or beakers. Once a week a multinet haul from 1000-500-250-100-50-0 m was performed to study the depth d~stribution of females and gonad development stages. Results show that the reproductive period of C. finmarchicusin the Atlantic rcqion of the Norwegian Sea can be subdivided in 3 periods in relation to phytoplankton devrlopmt,nt.(1) During the prebloom over a period of 49 d mean egg production rate was 8 eggs female-' d ' and an average of 47 of the females were mature. (2) Coincident with the bloom in mid May the e g g production rate increased up to a maximum of 44 eggs female-' d-' while more than 80% of the females were mature. (3) After the bloom at the beginning of June, egg production decreased, and mature females were only rarely found. Feedlng expenments indicate that food quantity limited egg production prior to the bloom, while presumably food quality was not sufficient dunng postbloom. However, due to high female abundance the total population egg production prior to the bloom was the same as during the bloom. This implies that the reproduction of C. finmarchicus in the Norwegian Sea is to some extent decoupled from the phytoplankton bloom.

Interannual variation in phytoplankton blooms and zooplankton productivity and abundance in the Gulf of Maine during winter

“…In 2 of these studies, measured (Irigoien et al 1998) and estimated (Richardson et al 1999) ingestion rates were insufficient to cover the energetic costs of EP. It is possible that in this species of Calanus, internal lipid stores provide most of the energetic requirements and some level of ingested material is required for gonad maturation and subsequent egg production (Ohman & Runge 1994, Niehoff et al 1999. Consistent with this interpretation, the spawning rates predicted in winter of 2000 in the GOM fit with Ivlev relationships relating chl a biomass to EP in this region (Fig.…”

“…In the Gulf of St. Lawrence, pre-bloom food limitation was demonstrated, as non-egg-producing females captured before the spring bloom and maintained in high food levels in the laboratory produced eggs well before their field counterparts. In contrast, significant rates of EP by C. finmarchicus have been observed at pre-bloom chl a concentrations of only 0.2 to 0.4 µg l -1 (Niehoff et al 1999, Richardson et al 1999, this study). In 2 of these studies, measured (Irigoien et al 1998) and estimated (Richardson et al 1999) ingestion rates were insufficient to cover the energetic costs of EP.…”

“…This illustrates the importance of female abundance in the regulation of population EP rates. A similar effect, where high abundance of adult females results in high population EP rates despite food limitation of EP rates, has been observed in the Norwegian Sea by Niehoff et al (1999).…”

Comparative ecology of over-wintering Calanus finmarchicus in the northern North Atlantic, and implications for life-cycle patterns

“…Alternatively, the composition of natural food consumed prior to the experimental incubations of summer-caught copepods may have inhibited egg production. Similarly, Niehoff et al (1999) found that egg production per female during the days following the 1997 spring phytoplankton bloom at Weathership M was substantially less than would have been expected on the basis of laboratory-based relationships with temperature and algal biomass. To summarize both the seasonal effect and the poorly quantified upper temperature limit for egg production, temperature dependency was represented in the nowcast model by a parabolic function which approximated to a Q 10 response fitted to the data of Hirche et al (1998) between 4 and 6 C, but decreased rather than increased at higher temperatures, approaching zero at 13 C (Appendix and Table 6).…”

Staging egg development of marine copepods with DAPI and PicoGreen®

“…Preservation of plankton was with buffered 4% formaldehyde. Samples collected by pump in 1998 by the U.S. GLOBEC Georges Bank program were provided by Edward Durbin of University of Rhode Island, and samples taken in 1997 with vertical nets at Station M in the Norwegian Sea (Niehoff et al 1999) were provided by HansJürgen Hirche and Barbara Niehoff of Alfred-Wegner Institute, Bremerhaven. We sorted eggs of Calanus finmarchicus from both of these sets of formaldehyde-preserved samples.…”