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A Simple Surface Water Biogeochemical Model: 1. Description, Sensitivity Analyses, and Idealized Simulations
Author(s) -
Jewell Paul W.
Publication year - 1995
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/95wr01021
Subject(s) - biogeochemical cycle , photic zone , environmental science , water column , atmospheric sciences , flux (metallurgy) , soil science , phytoplankton , nutrient , oceanography , chemistry , geology , environmental chemistry , organic chemistry
Accurate simulation of surface productivity, dissolved nutrient and oxygen concentrations, and particulate carbon flux are critical components of any viable surface water quality model. A linear, three‐component model consisting of a dissolved limiting nutrient, phytoplankton, and zooplankton coupled to a one‐dimensional turbulence closure fluid flow model has been constructed and applied to a generalized surface water setting. The model transfers nutrients from the euphotic zone to the subeuphotic zone using empirical biogenic flux‐depth relationships. The model does not require specification of biogenic particle settling velocity which is known to vary by at least 2 orders of magnitude in natural surface waters and thus constitutes a major source of uncertainty in many biogeochemical models. Using an empirical biogenic flux‐depth function to transfer nutrients through the water column introduces spatial errors which are most extreme in deep water. The model is thus most appropriate for lakes, estuaries, and shallow (<1000 m deep) marine settings. Restricting the model to three components with seven empirical constants permits a high degree of computational efficiency. Sensitivity analyses of the empirical constants show that integrated surface productivity is responsive to the three constants related to light (initial slope of the light‐productivity curve, light attenuation coefficient of the water, and photosynthetically available radiation) while being relatively insensitive to constants which are strictly related to biogeochemical transformations (remineralization rate, nutrient half‐saturation constant, maximum zooplankton growth rate, and Ivlev constant for zooplankton growth). Model simulations using idealized surface temperature boundary conditions produce thermal and biogeochemical characteristics of a typical temperate‐latitude lake. The simulations also suggest that vertical mixing plays an important role in producing the late seasonal, deep chlorophyll maximum commonly observed in many surface water settings.