Italy - The Lagoon of Venice
700
600
500
.!! 400
~ 300
200
Phosphorus in surface sediment
1-0--I norganic - - - - Total - k - - organic
100
0~--_4----~----+---~~--~----+---~~--~
Feb-B5 Apr-B5 Jun-B5 Aug-85 Sep-B5 Nov-85 Jan-86 Mar-86 May-86
Total nitrogen in surface sediment
3.5 ----------------------------------------------------3.0
. ; 2.5
E 2.0
1.5
1.0 ~---=i=----__+_----+_--_4----__+_----+__--_+----__I
Feb-B5 Apr-85 Jun-85 Aug-85 Sep-85 Nov-85 Jan-86 Mar-86 May-86
Organic carbon in surface sediment
19 -----------------------------------------------------17
. ; 15
E 13
11
9~--_+----__+_----+_--___t----~----+_--___t----~
Feb-85 Apr-85 Jun-85 Aug-85 Sep-85 Nov-85 Jan-86 Mar-86 May-86
361
Fig. 15.8. Annual trends of nutrients and organic carbon in the upper 5-cm surface layer
of the sediment at the Lido station
between 1989 and 1991) and the GPP in the central lagoon as estimated
for 1987 (Table 15.9). Nutrients recycled by macroalgae in 1987 were
approximately 23900 t of nitrogen and 2100 t of phosphate. Taking into
account the most recent estimations of nutrient loadings in this basin
(2578 and 351 t of Nand P, respectively; Andreottola et al. 1990), the
seaweeds recycled about nine times the total N and six times the P
entering the central lagoon annually (Table 15.9). Since the amount of