Libro de Resúmenes / Book of Abstracts (Español/English)

Resumenes 126
The lagoon of Chascomús is the largest one pertaining to the “Linked
Lagoons” of the province of Buenos Aires (Argentina); it has a surface of
3044 ha, a length of 15 km and a wide of 5 km; its average depth is 1.52 m
and its maximum depht is 2.50 m. The lagoon bottom is composed of
muddy clay and muddy sand, and lodges a great variety of fish of
commercial interest. Many of these fish are affected by periodic anoxic
crises that occur in association with high temperatures and low rain.
Previous studies have demonstrated a strong association between dissolved
oxygen (DO) concentration and the amount of suspended matter (seston).
Seston includes live organisms, dead organic matter and inorganic matter.
We present here a mathematical model of the seston dynamics. The model
was parametrised with existing data and a DO prediction was made taking
into account the negative correlation between seston and DO.
We consider that seston dynamics can be represented by a
differential equation including a growth rate (algae growth) related to light
and temperature, and a mortality/decomposition rate correlated with
temperature only:
dt
−k1
sin
[ ( B sin t + k )( 1 − e ) − C sin t − q ] ⋅ s
ds t
=
0
Temperature and light are periodic variables throughout the year.
The grow rate is considered asimptotic with light.
The solution of the equation is:
ln
−k
sin
e
cost
⎛ B
⎜
⎝ k1
1
0
() s = ( C − B)
cost
+ ( k − q ) ⋅ t + ⎜ sin t + ⎟ + E
0
The model has an equilibrium point that fluctuates throughout the
year following the forcing variables (temperature and light). The model fits
very well to experimental data of seston and DO. This model can help us to
predict anoxic crises and to predict them.
0
t
0
k
k
1
⎞
⎟
⎠