Table 3. Top-down calculations of mussel carbon budget for the mean expected harvest (ignoring seed stock) expressed as wet weight for two different trophic scenarios: years 1990, 2003. Values have been calculated by considering as a proxy the 1990 mussels physiological data, e.g., flesh dry weight % and carbon content. Globally, the carbon ingestion needed by mussels (F) is estimated as the sum of the carbon content of flesh dry weight (C, values from Brigolin et al. 2009), and the increase of carbon due to mean assimilation efficiency (D), both multiplied by the top-down trophic efficiency from mussels to phytoplankton (E, from Teramoto 1993, Townsend et al. 2000). In the lower part of the table the values of observed chlorophyll a converted to biomass (ratio Chl:C = 45) from year 2002 to year 2004 (simulation period) are reported to quantify the available biomass in each basin.

Mussel Carbon budget for year 1990 (CI = 15.5) Total (103 kg)
A Expected mussel harvest (wet weight) 30,000
B Flesh dry weight of mussel harvest 7% of A 2100
C Carbon content of flesh dry weight 40% of B 840
D Increase of Carbon due to the averaged assimilation efficiency 25% of C 210
E Increase of Carbon due to top-down trophic efficiency (C+D)/0.2 5250
F Total Carbon ingestion needed by mussels = E 5250
*Values are calculated on MP basin area; a factor of 1/3 for SENO I and 2/3 for SENO II has been considered
 
Mussel Carbon budget for year 2003 (CI = 9.5) Total (103 kg)
A Expected mussel harvest (wet weight) 50,000
B Flesh dry weight of mussel harvest 4% of A 2000
C Carbon content of flesh dry weight 40% of B 800
D Increase of Carbon due to the averaged assimilation efficiency 25% of C 200
E Increase of Carbon due to the averaged assimilation efficiency (C+D)/0.2 5000
F Total Carbon ingestion needed by mussels = E 5000
*Values are calculated on MP Basin area; a factor of 1/3 for SENO I and 2/3 for SENO II has been considered
 
Year Units MP Seno I Seno II
2002 Obs Chl a (µg l-1) - 1.71 2.43
2003 Obs Chl a (µg l-1) - 2.37 2.26
2004 Obs Chl a (µg l-1) - 1.07 1.78
Annual means, daily values (µg l-1) 1.72 2.16
2002 Biomass (mg C m-3) 95.3 77.0 109.0
2003 Biomass (mg C m-3) 104.0 107.0 102.0
2004 Biomass (mg C m-3) 66.0 48.2 80.1
Annual means, daily values (mg C/m3) 88.5 77.3 97.1
2002 Biomass (kg C d-1) 5700 2000 3700
2003 Biomass (kg C d-1) 6300 2800 3500
2004 Biomass (kg C d-1) 4000 1300 2700
Basin biomass, mean value (kg C d-1) 5300 2000 3300
Area, (m2)
Volume (m3, surface layer)
20,700,000 8,300,000 12,400,000
86,170,000 37,370,000 48,800,000