Phytoplankton modeling primary production

Fig. 1. Model depicting nitrogen flows in a kelp bed community. Primary production by macrophytes is partitioned into particulate (POM) and dissolved (DOM) components. Filter-feeders feed on detritus consisting of POM, bacteria and animal faeces. Recycling of nitrogen via the feedback loop provided by faeces is indicated by heavy lines. Fig. la) shows the model under downwelling conditions, when phytoplankton is imported with surface water from offshore. Fig. lb) shows the model under upwelling conditions when it is assumed that phytoplankton in the upwelling water is negligible and excess detritus is exported in surface water.

FIGURE 3 Proportion of lake area accounted for by littoral zones for the world s lakes (a), and the proportion of extracellular (ER) dissolved organic matter inputs derived from littoral zones (b see text for description of the model). The solid lines illustrate relationships in which lake boundaries are restricted to littoral and pelagic zones and the dotted lines illustrate patterns in which lake boundaries are expanded to include adjacent wetlands. In (b), the two sets of lines illustrate the range in the contribution of littoral zones to total lake ER with variation in rates of primary production for phytoplankton (0.1-2.0 kg organic matter m-2 yr 1) and macrophytes (0.6-3.8 kg organic matter nT2 yr 1). The relationship between littoral zone area and number of lakes is from Wetzel (1983). 

Arrigo KR, Worthen DL, Robinson DH (2003) A coupled ocean-ecosystem model of the Ross Sea. Part 2 iron regulation of phytoplankton taxonomic variability and primary production. J Geophys Res 108(C7) 3231. DOI 10.1029/2001J C000856... 

Phaeocystis sp. (Prymnesiophyceae). II. Pigment Composition. J Phycol 34 496-503 Wells ML (1999), Manipulating iron availability in nearshore waters. Limnol Oceanogr 44 1002-1008 Wells ML, Price NM, Bruland KW (1994) Iron limitation and the cyanobacterium Synechococcus in equatorial Pacific waters. Limnol Oceanogr 39 1481-1486 Worthen DL, Arrigo KR (2003) A coupled ocean-ecosystem model of the Ross Sea. Part 1 Interannual variability of primary production and phytoplankton community structure. In DiTullio GR, Dunbar RB (eds) Biogeochemistry of the Ross Sea. Antarct Res Ser 78 93-105... 

In many estuarine systems primary production by phytoplankton and other autotrophs is affected by N inputs and concentrations (e.g., Cloem, 2001 Howarth, 1988 Kelly, 2001 Nixon, 1992 Smith, 2003). For this review, we have compiled estimates of annual primary production and simple models used to relate production to nutrient conditions. We also discuss the evolution of thinking concerning nutrient limitation of pelagic primary production in estuaries. Finally, we review the conceptual models concerning benthic and pelagic primary production and consider the influence of N on these different autrotrophic components. 

Table 18.5 A summary, by date of publication, of statistical models relating phytoplankton primary productivity or biomass to nitrogen (concentration or loading rates) or other variables...

Figur 33 1 Physical and biological upwelling response simulated by the Wroblewski (1977) 2-dimensional coastal upwelling model (A) The circulation in the transverse plane normal to the coast, the bottom topography, and the wind stress. The maximum u and w velocities in the field are —2.9 cm s and 1.4 x 10 cm s , respectively. (B) The daily gross primary production of the water column. (C) The distribution of phytoplankton. Contour intervals are 1 jimol N 1. Redrawn with permission from Wroblewski (1977).

The focus of this review has been on the history and state-of-the-art of N-cycle models. One can legitimately ask how relevant these models are given recent advances in our understanding of the factors that control primary production and particulate matter export in the ocean. Fifteen to twenty years ago, when the Fasham et al. (1990) model was stiU under development, the potential importance of iron limitation was only beginning to be appreciated. The emphasis at that time was on N limitation, the intricacies of the food web and the potential importance of bacteria and the microbial loop. We now know that iron limits phytoplankton growth over... 

Scardi, M, 2001. Advances in neural network modeling of phytoplankton primary production. Ecological Modelling 146, p.33-45. 

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