Calculate Mean Total Abundance and Total Abundance

Hi there. I'm currently working on a report (based on fieldwork) where samples have been collected on field by different groups from different habitats e.g. from the dry zone, sublittoral, seagrass etc. And I am asked to calculate the mean total abundance, total abundance and mean total species and total species for the habitats for comparative reasons. However the problem is that the number of samples carried out by each group in the different habitats are not equal. Say group 1 performed 10 samples for seagrass, group 2 performed 5 samples from the same habitat and group 3 performed 7 samples. How do you normalize the data to make it a fair test? As for calculating the mean total abundance, that is easy because the no. of individuals collected by group 1 is divided by the no. of samples and the same for the different groups however what about the 'Total Abundance' and 'Total Species Number'? Cheers.