| State variable(s) and units | subject to ex-change | external inputs & outputs | local gains | local losses | effects on | Reference |
|
chlorophyll mg m-3 |
yes | light and nutrient controlled growth | mesozoo-plankton and benthic grazing | itself(-), via transparency; nutrients (-); mussels (+) | dCSTT model (Tett et al. 2003, Laurent et al 2006) | |
|
nutrients (N, P,
Si) mmol m-3 |
yes | recycling from grazing | uptake by phytoplankton | chlorophyll (+) | dCSTT model, as above | |
|
POM mg m-3 |
yes | mussel pseudo-faeces | feeding by mussels; sinking | mussels (+) | ||
|
AFC(s) g m-3 [ as mg/L] |
yes | from yachts in marinas | none | none | chlorophyll (-) | MAMPEC (van Hattum et al. 2002) |
|
individual mussel
biomass mg C |
no | initial biomass at seeding | feeding on algal C (from chlorophyll) and POM C | respiration | chlorophyll (-); POM (-); farm revenue (+) | Grant & Bacher 1998 |
|
mussel numbers (c x lines)‡ |
no | seeding (+), harvest (-) | natural mortality | as above, mussel biomass (effect = numbers x biomass) | ||
| mussel farm revenue | no | selling harvested mussels (unit price depends on biomass) | pay to employees†; taxation; replacing depreciated capital; cost of seed | [employment in local community]§ | ||
| marina revenue | no | renting moorings (to yachts) | pay to employees†; taxation; replacing depreciated capital |
AFCs release
(+) [employment in local community]§ |
||
|
† In each sector the simulated number of employees
was set by the size of the enterprise. Mussel farms had 1 full-time employee per
4 lines, and 12 lines were simulated in loch Fyne. Marinas had 10
full-time employees per 250 berths, plus seasonal employees up to 10 when the
berths were full. ‡ A line is a mussel farm unit, comprising a line of moored buoys, each supporting a rope containing c mussels when seeded at the start of year 1; simulated harvest took place in year 2. §Employment in the local community by the enterprises: we used the annual total of wages paid to people directly employed as a proxy for social benefit; |
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