AbstructA review of growth rates of diatoms and dinoflagellates in light-saturated, nutrient-replete cultures at 20°C confirms weak dependence on cell volume or mass. These maximal (intrinsic) rates are not linearly related to surface arca or surface-to-volume ratio of the cells. The growth of most diatoms is materially faster than that of dinoflagellates; other algae fall in between or below the dinoflagellates.Small ciliates have appreciably higher intrinsic growth rates than algae of the same cell volume. The average food consumption per ciliate in the marine pelagic realm is inferred to be very low, so that the realized specific growth rates are much smaller than the intrinsic potentials. Also, a previously postulated refuge from predation, afforded by small size, is extended down to about lo-pm3 cell volume.In this paper, I review the dependence of maximal growth rates of unicellular algae on cell volume, briefly contrast their rates with those of ciliates, and make inferences about marine pelagic food webs. Maximal (intrinsic) growth rates of organisms (Tm, or pLmax in the phycologists' parlance) were first scaled by Fenchel(l974) to cell mass by the allometric equation rm = aMb, where M is the wet (live) mass and a is a proportionality coefficient. The exponent b was -0.28 for the mass range from a virus to large ciliates. The mass dependence of algal growth rates was first quantified by Banse (1976), who suggested an exponent of -0.25 for optimal growth, which was the same as for the mass-specific respiration in betweenspecies comparisons (Hemmingsen 1960). Based on new measurements, however, Chan (1978) reported a very slight mass dependence of algal growth rates at saturating irradiance. I will support his conclusion with additional data from the literature and put this low mass dependence into broader physiological and ecological contexts.The quantitative role of ciliates as consumers of phytoplankton is a longstand-1 Contribution 1257 from the School of Occanography, University of Washington.

We investigate specific production rates (per unit biomass) of populations using published data on the relation of annual production/mean biomass (P/B). Aquatic and terrestrial invertebrates between the sizes of copepods and clams are emphasized, ranging about 105—fold in body mass upon reaching maturity (Ms, in kcal to compare with respiratory energy expense) and about 102—fold in P/B. Fishes and mammals are briefly treated; phytoplankton is mentioned. For 33 invertebrates living at annual mean temperatures between about 5° and 20°C, Ms is shown to be an efficient and precise estimator, or scaling factor, of the annual P/B. The rate declines markedly with Ms according to P/B = 0.65Ms—0.37. The exponent differs significantly from the —0.25 power of comparative physiology. Most of the measured values of P/B fall within 50 to 200% of predicted values. Much of this variability is associated with the ratio of annual production/annual respiration (P/R): for a given Ms, species achieving about half the predicted P/B have P/R ratios of about 0.1; those achieving twice the predicted P/B have P/R ratios of about 1.0. Age upon reaching maturity contributes some variability, with late—maturing (>1 yr) species tending towards a higher P/B. The variability is not significantly correlated with phylogenetic relationships (excepting insects for which P/B might not be mass—dependent), trophic type, major habitat, production rate, or biomass of the populations. The values of P/B of invertebrates living at annual mean temperatures >25° may be elevated over those of temperate species of the same Ms, while those of polar forms are depressed. The reasons for a single power function governing the mass dependence of P/B of temperate invertebrates, and for the particular exponent, are unclear; an ecological cause, i.e., mortality, combining with the general size dependence of life processes, is implicated. On the average, the annual specific mortality rate equals P/B and hence also declines by 0.65Ms—0.37. Very small metazoans (pelagic rotifers, benthic meiofauna) tend to have an appreciably lower P/B than indicated by the relationship for larger invertebrates. A refuge from predation by being small is postulated which may also apply for phytoplankton. For meiofauna, a power function of mass dependence of P/B with average rates 3—5 times below those of the larger invertebrates is suggested. Annual P/B values of fishes and mammals likewise decline by a power function of Ms; the few available data yield exponents of —0.26 and —0.33, respectively. Ecological reasons are again invoked. Values of P/B and the specific mortality rates of temperate fishes seem to be 4—5 times, and those of mammals 20—25 times, higher than those of temperate invertebrates of the same mass.

Although it is nominally a tropical locale, the semiannual wind reversals associated with the Monsoon system of the Arabian Sea result annually in two distinct periods of elevated biological activity. While in both cases monsoonal forcing drives surface layer nutrient enrichment that supports increased rates of primary productivity, fundamentally different entrainment mechanisms are operating in summer (Southwest) and winter (Northeast) Monsoons. Moreover, the intervening intermonsoon periods, during which the region relaxes toward oligotrophic conditions more typical of tropical environments, provide a stark contrast to the dynamic biogeochemical activity of the monsoons. The resulting spatial and temporal variability is great and provides a significant challenge for ship-based surveys attempting to characterize the physical and biogeochemical environments of the region. This was especially true for expeditions in the pre-satellite era. Here, we present an overview of the dynamical response to seasonal monsoonal forcing and the characteristics of the physical environment that fundamentally drive regional biogeochemical variability. We then review past observations of the biological distributions that provided our initial insights into the pelagic system of the Arabian Sea. These evolved through the 1980s as additional methodologies, in particular the first synoptic ocean color distributions gathered by the Coastal Zone Color Scanner, became available. Through analyses of these observations and the first large-scale physical-biogeochemical modeling attempts, a pre-JGOFS understanding of the Arabian Sea emerged. During the 1 990s, the in situ and remotely sensed observational databases were significantly extended by regional JGOFS activities and the onset of Sea-viewing Wide Field-of-View Sensor ocean color measurements. Analyses of these new data and coupled physical-biogeochemical models have already advanced our understanding and have led to either an amplification or revision of the pre-JGOFS paradigms. Our understanding of this complex and variable ocean region is still evolving. Nonetheless, we have a much better understanding of time-space variability of biogeochemical properties in the Arabian Sea and much deeper insights about the physical and biological factors that drive them, as well as a number of challenging new directions to pursue. The publl reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, Sjlfhering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of htfcrmsti n, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware tbsn notiithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a...

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