Biogeochemical Cycles - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 116

TABLE 4.13
Temperature Correction Factor for Organic Nitrogen
Decomposition in Sediments to NH 4 + ( θ )

Average Location Reference As Cited in

1.04 Texas bays and estuaries Brandes, 1976 Bowie et al. 93

1.18 Patuxent River Estuary Lung, 1992 Lung 80

Sediment NH 4 + release rates for coastal marine environments are given in
Table 4.14.

4.1.5.1.7 Nitrate Nitrogen (Benthic)

∂
∂

C
t

2

=− k

−
DD

θ

( T 20 )

C (4.28)

12 443 44

22 2

Denitrification

where
C 2

= nitrate nitrogen concentration [mg N l −1 ]

k 2D = denitrification rate constant at 20 ° C [day −1 ]

θ 2D = denitrification temperature coefficient [none]

T = water temperature [ ° C]

Sediment oxidized nitrogen release rates compiled from the literature are given
in Table 4.15. Half-saturation concentrations for nitrate and sediment denitrification
rates are presented in Tables 4.16 - 4.17.

4.1.5.2 Modeling of Phosphorus Cycle

The three phosphorus variables modeled in EUTRO5 are phytoplankton phosphorus
(phosphorus incorporated in phytoplankton cells), organic phosphorus, and inorganic
phosphorus (orthophosphate). Organic and inorganic phosphorus are divided into
their particulate and dissolved fractions.
Dissolved inorganic phosphorus is incorporated into phytoplankton cells during
growth. During phytoplankton respiration and death, organic and dissolved inorganic
phosphorus are released. Upon release, dissolved inorganic phosphorus is readily avail-
able for algal growth and the released organic phosphorus must undergo mineralization
or bacterial decomposition before it can be utilized by phytoplankton. Similar to organic
nitrogen mineralization, the organic phosphorus mineralization term in EUTRO5
includes a saturating recycle rate that is directly proportional to the phytoplankton
biomass present.