  Many fundamental parameters of biological systems -- eg. productivity,
population sizes and biomass -- are most effectively expressed in absolute
terms. In contrast to proportional data (eg. percentages), absolute values
provide standardised metrics on the functioning of biological entities (eg.
organisism, species, ecosystems). These are particularly valuable when
comparing assemblages across time and space. Since it is almost always
impractical to count entire populations, estimates of population abundances
require a sampling method that is both accurate and precise. Such absolute
abundance estimates typically entail more "sampling effort" (data collection
time) than proportional data. Here we refined a method of absolute abundance
estimates -- the "exotic marker technique" -- by producing a variant that is
more efficient without losing accuracy. This new method, the "field-of-view
subsampling method" (FOVS method) is based on area subsampling, from which
large samples can be quickly extrapolated.
  Two case studies of the exotic marker technique were employed: 1, computer
simulations; and 2, an observational "real world" data set of terrestrial
organic microfossils from the Permian- and Triassic-aged rock strata of
southeastern Australia, spiked with marker grains of known quantity and
variance. We compared the FOVS method against the traditional "linear method"
method using three metrics: 1, concentration (specimens/gram of sediment); 2,
precision and 3, data collection effort. In almost all cases, the FOVS method
delivers higher precision than the linear method, with equivalent effort, and
our computer simulations suggest that the FOVS method more accurately estimates
the true error for large target-to-marker ratios. Since we predict that these
conditions are typically common, we recommend the new FOVS method in almost
every "real world" case.
