Striving for -water Quanity Figure 3. Water quality when only milkfish are present. because there is still nothing to reduce the waste except the algae-which will grow uncontrollably to consume the milkfish waste, thus raising the level of chlorophyll to the point where it chokes off the sunlight and nutri- ents needed for the coral reef to grow [Environmental Protection Agency 2004. While it is possible to reduce the levels of waste through harvesting, doing so will only reduce the rate at which the waste level of bacteria grows (a more gradual slope), not cause it to decline Task 3: Water Quality of a Polyculture Before the farming of massive quantities of milkfish in pens, there was a balanced ecosystem of a variety of species that coexisted in ratios that allowed the waste of certain animals to serve as food for others. However the demand for milkfish led to a disruption of this balance The ecosystem is not as ideal as it once was, as we modeled in Task 1; but it is not as blea a situation as the milkfish monoculture that we modeled in Task 2. The second model in that task shows that the quantities of other species in the current system are insufficient to reach target levels of water quality-ones that would maximize the value ofbiomass available for harvest by restoring the natural catalyst of coral growth. The coral serves as protective shelter for all of these species. Coral grows very slowly, on average only 80 mm/yr [Roth 1979]Striving for Balance 149 3WO 300- 250 200 - Water Quality - Liunear (Water Quality) 150 100 so 0 5 10 25 20 25 30 35 Figure 3. Water quality when only milkfish are present. because there is still nothing to reduce the waste except the algae-which will grow uncontrollably to consume the milkfish waste, thus raising the level of chlorophyll to the point where it chokes off the sunlight and nutri￾ents needed for the coral reef to grow [Environmental Protection Agency 2004]. While it is possible to reduce the levels of waste through harvesting, doing so will only reduce the rate at which the waste level of bacteria grows (a more gradual slope), not cause it to decline. Task 3: Water Quality of a Polyculture Before the farming of massive quantities of milkfish in pens, there was a balanced ecosystem of a variety of species that coexisted in ratios that allowed the waste of certain animals to serve as food for others. However, the demand for milkfish led to a disruption of this balance. The ecosystem is not as ideal as it once was, as we modeled in Task 1; but it is not as bleak a situation as the milkfish monoculture that we modeled in Task 2. The second model in that task shows that the quantities of other species in the current system are insufficient to reach target levels of water quality-ones that would maximize the value of biomass available for harvest by restoring the natural catalyst of coral growth. The coral serves as protective shelter for all of these species. Coral grows very slowly, on average only 80 mm/yr [Roth 1979]