Herbivory as a factor in patterns of nutrient utilization in the sea1

Abstract

A comparison of the horizontal nutrient gradients in coastal upwelling systems of the eastern boundary currents, in offshore divergences of high and low latitudes, and in the central gyres of the oceans suggests that changes in the dominant frequencies of variability of the physical habitat may define the importance of grazing stress as a constraint to nutrient utilization in the sea.Liebig's (1840) "1 aw of the minimum" and Lindeman's ( 1942 ) "trophic-dynamics" are rather general ecological concepts that are probably only applicable for brief periods during the life history of an organism. For example, simple consideration of single

Size dependence of growth and photosynthesis in diatoms: a synthesis

“…An alternative explanation of the occasional dominance of large phytoplankters can b e based on a consideration of the population dynamics of microalgae and zooplanktonic herbivores (Walsh 1976). Small microalgae are typically harvested by small invertebrates with mass-specific maximum growth rates which are the same magnitude as, or even greater than, microalgal growth rates (Banse 1982a).…”

“…Walsh and coworkers (Walsh 1976, Walsh et al 1978) have noted that blooms of large phytoplankton occur in the temporally more variable continental shelf regions where the storm cycle of about a week duration can account for a significant amount of the variance of water motion. The storm cycle produces a large input of nutrients on a time scale which allows uncoupling of the population dynamics of copepod herbivores and large-celled phytoplankton resulting in blooms.…”

Influence of iron on algal community composition and physiological status in the Peru upwelling system

“…The ''shift-up and shift-down'' phytoplankton physiological response occurs rapidly (a few days) near the coast (30-60 km) because of active upwelling and the rapid depletion of macronutrients as water is advected toward the shelf break (MacIssac et al 1985). Historically, grazing processes were believed to be primarily responsible for the high-nitrate, lowchlorophyll (HNLC) condition off the Peruvian continental shelf (Walsh 1976). Fe, however, was recently shown to be an important factor affecting phytoplankton assemblages and biogeochemical cycling near the Peru coast (Hutchins et al 2002;Eldridge et al 2004;Bruland et al 2005).…”

Carbon fluxes in the equatorial Pacific: a synthesis of the JGOFS programme

“…One of the main characteristics of tropical ecosystems is low temporal variability (Cushing, 1959;Walsh, 1976), and this is true also for both the warm pool and the equatorial upwelling systems. On time scales of less than a day, however, there can be substantial changes in abundance, cell size and in situ fluorescence (Binder and DuRand, 2002) due to active grazing at night by micrograzers, synchronized cell division , cell growth (Neveux et al, submitted), and changes in the chlorophyll to carbon content of individual cells as a function of irradiance (Kiefer, 1973;Dandonneau and Neveux, 1997;Neveux et al, submitted).…”