How is patchiness addressed?
Dramatic variability can occur in seagrass habitats often without apparent environmental gradients. Choices in sampling may be made to exclude or include the variability or to specifically examine the patchiness. For example, if standing crop of a seagrass community needs to be determined and a preliminary examination of the survey area shows dense beds interspersed with bare patches, different sampling design alternatives yield different information. Underwater assessments using harvesting or estimation often avoid bare patches and results are presented in terms of standing crop within beds (excluding spatial variability). By adding aerial photography to the design, the areas of dense beds and bar patches can be quantified. Now the standing crop results can also represent the area as a whole, multiplying the mean standing crop by the ratio of bare patch area to meadow area, assuming bare patches have zero standing crop (specific examination of patchiness). Another way to deal with patchiness is to adjust the sample size to include it, and then ignore the patchiness when selecting sampling sites. For instance, if the sampling unit is 5 to 10 fold larger in area than the average patch size (or 2 to 3 fold longer than average patch length), the measurement of mean standing crop will reflect the variability without losing precision (including spatial variability). If the spatial variation(patchiness) is hopelessly larger than