Preprint volume - SIBM

Pre-print Volume - Oral presentations
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
diffusion. The general ecological model calibration on primary forcing showed a good
level of accuracy compared primarily with the surface layer dataset (years 2002-2003)
acquired by stations located in Seno II that gave an idea of the annual trend for nutrient
loads (Fig. 1).
Nitrogen (kg m -3 )
0.0016
0.0014
0.0012
0.001
0.0008
0.0006
0.0004
0.0002
0
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SENO II-Nitrogen
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
110
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Time (days)
Fig. 1 - The simulated total nitrogen concentration at the surface (solid line) and bottom (dashed line)
layers, compared to the experimental data collected at the surface (triangles).
I risultati del modello relativi alla simulazione della concentrazione di azoto totale nello
strato superficiale (linea continua) e nello strato di fondo (linea tratteggiata) comparati con i
dati di superficie determinati sperimentalmente (triangoli).
The calibration of the phytoplankton community changes are based on observed data
(years 2002-2003). The phytoplankton succession is complicated by a feedback with
nutrient regeneration and grazing by predators (e.g. zooplankton and mussels).
The succession of the three groups indicates that diatoms prevail in winter (with high
runoff and consequently high new nitrogen load), dinoflagellates and phytoflagellates
increase during summer (with higher ammonia values) (Fig. 2).
The field data testify that throughout the years, a drastic reduction of the total
phytoplankton and particularly of diatom abundance has been observed (Caroppo C.,
unpublished data). So, it seems that the qualitative composition of the communities is
changing with a shift from diatoms to nano-phytoplagellates as dominant group in
terms of cell densities. Probably, this last is an evidence of the change of system’s
nutrient load due to the sewer discharge reduction occurred between 2000 and 2007
(Caroppo et al., 2010).
Conclusions – Historical studies of Mar Piccolo ecosystem are mostly limited only to
models of circulation (Umgiesser et al., 2007) and to statistical studies on hydrology
and chemico-physical features (Alabiso et al., 1997).
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