Such a system, however, will continue to work well only if it is managed-managed well once the system begins to take shape. ongoing management is to be instituted as one ofits essential components only management can control the feedback loops needed to aug ment those that have evolved as internally functioning mechanisms in natural systems. Cer tain kinds of control are needed to prevent foreign and potentially damaging materials like fertilizers, pesticides, oil residues, or phosphates from entering the lagoon. Human activities can be regulated in such a way as to prevent their interfering with sensitive lagoon processe or populations Critical indicators of environmental quality, especially water quality in the lagoon need to be monitored to maintain the stability of the system. When an imbalance appears, or if there is evidence of deterioration or conflict somewhere, some correctiv action can be taken. In the absence of such a program, however carefully the initial design may be conceived the lagoon w ill eventually return to its present sorry state or worse.