Seasonal progression of factors limiting phytoplankton pigment biomass in the Rhode River estuary, Maryland (USA). II. Modeling N versus P limitation

Abstract

Pre\~iously reported experiments demonstrated that N addition enhanced phytoplankton growth rate more frequently and to a greater extent than did addition of P alone. Here w e develop a modcl of nutrient-limited net phytoplankton production for the Rhode River estuary, Maryland (USA). to determine the sensitivity of observed patterns to changes in the manner in which nutrients are delivered to the system The model successfully reproduced the seasonal pattern of phytoplankton chlorophyll variation for an average year, the relatlve timlng of P and N limitat~on, and the ~nterannual val-1-ability in the timing of the shift from P to N limitation. Manipulat~on of nutrient sources In the model suggested that the disappearance of N at the seaward boundary of the estuary is sufficient to produce the shift from P to N I~inltation. Raising the modeled N:P ratio of sediment nutrient release to a value greater than that of the phytoplankton biolnass caused CO-liinltation by both N and P in the sumnler, but no manipulations produced lim~tation solely by P in the summer. In the model, different computed indicators of nutrient limitation (i.e. ratios of available N:P, physiological ~ndicators of internal nutrient pools, and computed growth stimulation by nutrient additions) generally identified the same nutrient as limiting at a particular time. The model demonstrates how observed shifts in nutrient limitation result from changes In delivery of N and P from the watershed, from the sediment, and from incoming phytoplankton.

Mediation of benthic–pelagic coupling by microphytobenthos: an energy- and material-based model for initiation of blooms of Aureococcus anophagefferens

“…The geochemistry of nitrogen and phosphorus differ because of phosphorus' tenacious binding to sediments (Addiscott and Thomas, 2000) and lateral inputs of phosphorus are likely only when there is transport of sediment particles, as occurs during storms (Fisher et al, 1998). Even in a system such as the Rhode River, a sub-estuary of Chesapeake Bay, where the nitrogen budget is dominated by riverine inputs, benthic resuspension is likely to be critical in regulating inputs of phosphorus (Gallegos and Jordan, 1997). The benthos might therefore be a critical source of a nutrient or nutrients even where there are large lateral inputs.…”

Annual cycle of microalgal biomass in a South African temporarily-open estuary: nutrient versus light limitation

“…5), but also in an increase in nutrient loading. High DIN and DIP concentrations usually stimulate algal growth (Fisher et al 1992, Gallegos & Jordan 1997. One month after the opening of the estuary, DIN:DIP ratios were well above the Redfield ratio of 16:1 (Fig.…”

HOW CRITICAL IS THE CRITICAL N:P RATIO?1

“…It should be noted, however, that neither the Monod model nor the traditional quota model (which is superior in ecosystem simulations; e.g. Gallegos and Jordan 1997 have the capacity to simulate nutrient transport at rates above that required to support steady‐state uptake, for example, to demonstrate changes in potential transport rates with nutrient stress.…”