Estimates of oceanic mesozooplankton production: a comparison using the Bermuda and Hawaii time-series data

https://doi.org/10.1016/S0967-0645(01)00099-6Get rights and content

Abstract

Mesozooplankton growth rates were estimated for the Hawaiian (HOT) and Bermuda (BATS) ocean time-series stations using the empirical model of Hirst and Lampitt (Marine Biology 132 (1998) 247), which predicts copepod growth rate from temperature and body size. Using this approach we derived seasonal and annual estimates of mesozooplankton production as well as rates of mesozooplankton ingestion and egestion using assumed growth and assimilation efficiencies for the period 1994–1997. Annual mesozooplankton production estimates at HOT (average 0.79 mol C m−2 yr−1) were higher than production estimates at BATS (average 0.33 mol C m−2 yr−1) due to both higher mesozooplankton biomass and higher estimated mesozooplankton individual growth rates. Annual primary production at the two sites was similar (average 14.92 mol C m−2 yr−1 at HOT and 13.43 mol C m−2 yr−1 at BATS). Thus, mesozooplankton production was a greater fraction of primary production at HOT (0.05) as compared to BATS (0.02). Mesozooplankton potentially contributed more to the gravitational flux of carbon at HOT, where the ratio of the average annual estimate of mesozooplankton fecal pellet carbon production/annual estimate of carbon flux at the base of the euphotic zone was 1.03 compared to the same ratio of 0.39 at BATS. Mortality estimates were similar to estimates of mesozooplankton production when compared over the entire study period. The higher mesozooplankton biomass and derived rate parameters at HOT compared to BATS may be due to the more episodic nature of nutrient inputs at BATS, which could result in mis-matches between increases in phytoplankton production and the grazing/production response by mesozooplankton. In addition, there is evidence to suggest that there are periodic blooms of gelatinous macrozooplankton (salps) at BATS that may not be captured sufficiently by the monthly sampling program. Thus the gelatinous zooplankton would add to the overall grazing impact on the phytoplankton at BATS as well as the contribution of zooplankton to the gravitational flux of biogenic material via fecal pellet production.

Introduction

In situ copepod growth estimates have been made in restricted water bodies such as lakes, mesocosms, lagoons and bays where emigration and immigration are zero or minimal. In situ growth measurements in open waters have been conducted while following drogues (i.e. Cushing and Tungate, 1963), but the measurements are extremely time-consuming and it is difficult/impossible to follow the same population/water mass over enough time to measure copepod growth rates. Shipboard incubation techniques have been used for growth estimates for individual copepod species based on molting frequency (e.g., Miller et al., 1984) and egg production (e.g., Kiørboe and Johansen, 1986; Berggreen et al., 1988), but these techniques are subject to a variety of containment effects and are of limited value for overall copepod community growth estimates in tropical and sub-tropical seas where the species diversity of copepods is great (e.g., Grice and Hart, 1962; Timonin, 1971). In addition, in some circumstances weight-specific reproductive growth (i.e. egg production) is not the same as weight-specific somatic (increase in body mass) growth (McKinnon, 1996; Hopcroft and Roff, 1998), so that the egg production method may not accurately represent the growth of the whole copepod population.

Another approach to estimating copepod metabolism is based on regression models that use temperature (e.g. Huntley and Lopez, 1992) or temperature and body size (e.g. McLaren, 1965; Ikeda and Motoda, 1975; Hirst and Sheader, 1997; Hirst and Lampitt, 1998) to predict copepod growth rates. These empirical models are based on laboratory, and in some cases, field measurements of copepod growth rates (somatic growth) over a range of temperatures, food conditions, copepod body sizes and copepod species. The predictive equations assume that all species (sizes of copepods) grow at the same rate at a particular temperature. In some cases we know that this is not true. For example, cyclopoid copepods may grow slower than the same size calanoid copepods (Lampitt and Gamble, 1982; Kiørboe and Sabatini, 1995; Hopcroft et al., 1998). This regression approach also has been criticized (Kleppel et al., 1996; Calbet and Agusti, 1999) because it assumes that growth rate is not food limited. The egg production rates of copepods have been shown to be food-limited in a variety of marine waters (e.g. Checkley, 1980; Durbin et al., 1983; Saiz and Kiørboe, 1995). It is interesting to note, however, that spatial and temporal estimates of copepod biomass can vary by several orders of magnitude whereas published copepod growth rates at similar temperature varies by 2–4 times (e.g. Huntley and Lopez, 1992; Hopcroft et al., 1998). Thus for estimates of copepod production (growth rate×biomass) the errors associated with estimates of growth rate are probably less compared to those of biomass.

We have used an empirical regression model (Hirst and Lampitt, 1998) to estimate mesozooplankton production and assumed rates of ingestion and egestion at the Hawaiian and Bermuda ocean time-series stations, both part of the US Joint Global Ocean Flux Study (US JGOFS) program. At these study sites, seasonal measurements of mesozooplankton size fractions and species composition can be used for size-based copepod growth models. JGOFS core measurements allow these mesozooplankton rate estimates to be compared to rates of primary production and export flux to deduce the role of mesozooplankton in the cycling of biogenic material. Repeated mesozooplankton biomass measurements over the year can provide the necessary data for crude estimates of annual mesozooplankton production, which can be compared to annual estimates of primary production and the gravitational flux of material from the euphotic zone.

Section snippets

Mesozooplankton sampling

Mesozooplankton samples were collected at the Hawaiian ocean time-series (HOT; 22°45′N, 158°00′W; Karl and Lukas, 1996) and Bermuda Atlantic time-series (BATS; 31°50′N, 64°10′W; Michaels and Knap, 1996) stations. The details of mesozooplankton sampling and processing have been described for both HOT (Landry et al., 2001) and BATS (Madin et al., 2001). Briefly, oblique tows were taken with a 1 m-diameter (BATS) or 1-m2 (HOT), 200-μm mesh net equipped with a General Oceanics flowmeter and

Mesozooplankton biomass

The seasonal cycles of mesozooplankton biomass at HOT (Landry et al., 2001) and BATS (Madin et al., 2001) have been described previously. In general, there was over twice as much mesozooplankton at HOT compared to BATS (Fig. 1; Table 1), with the average being 23.84 mmol C m−2 at HOT and 11.38 mmol C m−2 at BATS for samples collected between 1994 and 1997. There were significant (P<0.05) seasonal differences in mesozooplankton biomass at HOT, with the highest mean values found in the fall and the

Discussion

Our estimates of mesozooplankton growth, production, mortality, egestion and ingestion will be overestimates if the actual in situ mesozooplankton growth rates were food-limited. The 935 published growth rates used to generate the Hirst and Lampitt (1998) equation covered a range of food conditions, some of which were food-limited growth. The average estimated mesozooplankton growth rates, weighted by the distribution of biomass size fractions, were 0.09 and 0.08 d−1 at HOT and BATS,

Acknowledgments

This research was support by Grant OCE-9725976 from the National Science Foundation as part of the US JGOFS Synthesis and Modeling study. We are grateful to the scientists involved in the HOT and BATS time-series programs for collecting and analyzing the data. Scott Doney and two anonymous reviewers made helpful comments on an earlier version of the manuscript. This is University of Maryland Center for Environmental Sciences Contribution No. 3486; and US JGOFS Contribution No. 693.

References (62)

  • D.K. Steinberg et al.

    Zooplankton vertical migration and the active transport of dissolved organic and inorganic carbon in the Sargasso Sea

    Deep-Sea Research I

    (2000)
  • J.R. White et al.

    Latitudinal gradients in zooplankton biomass in the tropical pacific at 140°W during the JGOFS EqPac studyeffects of El Niño

    Deep-Sea Research I

    (1995)
  • Bates, N.R., 2001. Interannual variability of oceanic CO2 and biogeochemical properties in the western North Atlantic...
  • U. Berggreen et al.

    Food size spectra, ingestion and growth of the copepod Acartia tonsa during developmentimplications for determination of copepod production

    Marine Biology

    (1988)
  • A. Calbet et al.

    Latitudinal changes in copepod egg production rates in Atlantic waterstemperature and food availability as the main driving factors

    Marine Ecology Progress Series

    (1999)
  • C.A. Carlson et al.

    Annual flux of dissolved organic carbon from the euphotic zone in the northwestern Sargasso Sea

    Nature

    (1994)
  • D.M. Checkley

    Food limitation of egg production by a marine, planktonic copepod in the sea off southern California

    Limnology and Oceanography

    (1980)
  • R. Conover

    Transformations of organic matter

  • T.J. Cowles et al.

    In situ characterization of phytoplankton from vertical profiles of fluorescence emission spectra

    Marine Biology

    (1993)
  • D.H. Cushing et al.

    Studies on a Calanus patch. I. The identification of a Calanus patch

    Journal of the Marine Biological Association of the United Kingdom

    (1963)
  • G.B. Deevey

    The annual cycle in quantity and composition of the zooplankton of the Sargasso Sea off Bermuda. I. The upper 500 m

    Limnology and Oceanography

    (1971)
  • G.B. Deevey et al.

    The annual cycle in quantity and composition of the zooplankton of the Sargasso Sea off Bermuda. II. The surface to 2000 m

    Limnology and Oceanography

    (1971)
  • E.G. Durbin et al.

    Food limitation of production by adult Acartia tonsa in Narragansett Bay, Rhode Island

    Limnology and Oceanography

    (1983)
  • B.W. Frost

    Effects of size and concentration of food particles on the feeding behavior of the marine planktonic copepod, Calanus pacificus

    Limnology and Oceanography

    (1972)
  • J.C. Goldman

    Spatial and temporal discontinuities of biological processes in pelagic surface waters

  • G.D. Grice et al.

    The abundance, seasonal occurrence and distribution of epizooplankton between New York and Bermuda

    Ecological Monographs

    (1962)
  • A.G. Hirst et al.

    Towards a global model on in situ weight-specific growth rates in marine planktonic copepods

    Marine Biology

    (1998)
  • A.G. Hirst et al.

    Are in situ weight-specific growth rates body-size independent in marine planktonic copepods? A re-analysis of the global syntheses and a new empirical model

    Marine Ecology Progress Series

    (1997)
  • R.R. Hopcroft et al.

    Zooplankton growth ratesthe influence of female size and resources on egg production of tropical marine copepods

    Marine Biology

    (1998)
  • R.R. Hopcroft et al.

    Zooplankton growth ratesthe influence of size and resources in tropical marine copepodites

    Marine Biology

    (1998)
  • M. Huntley et al.

    Food-limited growth of marine zooplankton

    The American Naturalist

    (1984)
  • Cited by (0)

    View full text