Figure 12.3 Observed eelgrass distribution (yellow cross-hatch) and simulated eelgrass (green) depth 
distribution based on the 75 th percentile case. Brown regions are unsuitable for eelgrass 
survival. Inset boxes show that the 75 th percentile case would eliminate much of the current 
eelgrass distribution in Zone 2. 
12.5 Discussion 
Many seagrass monitoring and assessment programs rely on presence/absence data or periodic 
evaluations of biomass and distribution (Pulich and White, 1997; Berry et al., 2003). However, these 
parameters are not very sensitive indicators of seagrass decline since they require very large sample 
sizes to detect modest changes (Heidelbaugh and Nelson, 1996). For example, biomass is a classic 
response variable; however, by the time monitoring programs can detect changes in biomass the 
perturbation may have caused seagrass decline. Better indicators of stress and decline are required to 
adequately assess seagrass condition. Non-structural carbohydrates may provide a more sensitive and 
integrative response variable since carbohydrate is the energy “currency” of the plant. Our assessment 
of the protective capacity of potential criteria was based on an evaluation of modeled carbohydrate 
content and modeled biomass. 
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