136 The UMAP Journal 30.2 (2009) Table 6 Concentrations of elements in a pen. Element Concentration (ug/L) c(10% N(04%) 14-29 P(06%) 2.1-43 age weight and price of each species, and finally figure out the income K=$114×103 To calculate the cost of improving water quality, assume that we intro- duce 1,000 mussels into the pen. We investigate such factors as weight and market price of mussels, and put them into the model in Task 1 to figure out all the indexes Steady-state numbers(x10 )of species before adjustment. Algae Molluscs Herbivorous Milkfish (mussels) Before adjust After adjustme 137 062 061 0.70 Table 8 Concentrations of elements(ag/L)before and after adjustment. Chlorophyll C Before adjustment 0202 357114292.1-4 After adjustment 125336913282.041 From Table 8, it is easy to see that the water quality has improved. For one thing, the introduced mussels feed on the algae for one thing, and for another they decompose the organic particles. The 1,000 introduced mussels cost $361 or so, scarcely making a dent in Income Task 4 rom Task 3a, we know the numbers of algae, filter feeders, herbivo- rous fish, and milkfish:(14314, 6092, 6129, 6979). The algae are the most numerous, and the numbers of the other species are roughly equal. In such a steady state136 The UMAP Journal 30.2 (2009) Table 6. Concentrations of elements in a pen. Element Concentration (pg/L) C (10%) 35 -72 N (0.47) 1.4- 2.9 P (0.6%) 2.1- 4.3 age weight and price of each species, and finally figure out the income: K = $114 x 10i/pen. * To calculate the cost of improving water quality, assume that we intro￾duce 1,000 mussels into the pen. We investigate such factors as weight and market price of mussels, and put them into the model in Task 1 to figure out all the indexes. Table 7. Steady-state numbers (x104 ) of species before adjustment Algae Molluscs Herbivorous Milkfish (mussels) Fish Before adjustment 1.43 0.61 0.61 0.70 After adjustment 1.37 0.62 0.61 0.70 Table 8. Concentrations of elements (fig/L) before and after adjustment Chlorophyll C N P Before adjustment 0.202 35-71 1.4-2.9 2.1-4.3 After adjustment 0.125 33-69 1.3-2.8 2.0-4-1 From Table 8, it is easy to see that the water quality has improved. For one thing, the introduced mussels feed on the algae for one thing, and for another they decompose the organic particles. e The 1,000 introduced mussels cost $361 or so, scarcely making a dent in the income. Task 4 From Task 3a, we know the numbers of algae, filter feeders, herbivo￾rous fish, and milkfish: (14314, 6092, 6129, 6979). The algae are the most numerous, and the numbers of the other species are roughly equal. In such a steady state: