Defining the adequate sampling effort necessary in tropical ecosystems is a sensitive subject. It is virtually
impossible to sample every single species in an ecosystem. Thus, sampling must be a compromise between
the desired completeness of the dataset and the amount of time and work that is feasible for researchers to
do during fieldwork. Here, we used rarefaction procedures and richness estimators to evaluate sampling
issues in a coastal lagoon in Ceará state, Brazil. We used 70 plots (1 m2 each) to perform a phytosociological
study in the lagoon and complemented the data with opportunistic floristic observations. We then applied
statistical methods to the phytosociological survey to estimate how much of the local plant diversity had
been sampled. Extrapolating our sampling accumulation curve to a sampling effort three times larger
than the actual sampling done (210 plots), we were able to estimate the cumulative richness expected.
After this, we used a different approach and calculated how many plots would be necessary to record a
certain proportion of the total plant community. We recorded 49 species using phytosociological plots
and 65 species in the floristic compilation. Richness estimators calculated the local alfa diversity to be
between 68 and 85 species. We show that sampling 80% of the total local richness would require 100
plots, which is a reasonable sampling effort, but to sample 99% of the species, an extremely large amount
of sampling would be needed (580 plots). This is not practical during fieldwork. We show here how
rarefaction and extrapolation can be used as a framework to gauge the amount of field effort needed in
aquatic ecosystems.
Defining the adequate sampling effort necessary in tropical ecosystems is a sensitive subject. It is virtuallyimpossible to sample every single species in an ecosystem. Thus, sampling must be a compromise betweenthe desired completeness of the dataset and the amount of time and work that is feasible for researchers todo during fieldwork. Here, we used rarefaction procedures and richness estimators to evaluate samplingissues in a coastal lagoon in Ceará state, Brazil. We used 70 plots (1 m2 each) to perform a phytosociologicalstudy in the lagoon and complemented the data with opportunistic floristic observations. We then appliedstatistical methods to the phytosociological survey to estimate how much of the local plant diversity hadbeen sampled. Extrapolating our sampling accumulation curve to a sampling effort three times largerthan the actual sampling done (210 plots), we were able to estimate the cumulative richness expected.After this, we used a different approach and calculated how many plots would be necessary to record acertain proportion of the total plant community. We recorded 49 species using phytosociological plotsand 65 species in the floristic compilation. Richness estimators calculated the local alfa diversity to bebetween 68 and 85 species. We show that sampling 80% of the total local richness would require 100plots, which is a reasonable sampling effort, but to sample 99% of the species, an extremely large amountof sampling would be needed (580 plots). This is not practical during fieldwork. We show here howrarefaction and extrapolation can be used as a framework to gauge the amount of field effort needed inaquatic ecosystems.
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