* Crimerian Astrophysic Laboratory, Nauchny Krym, Krym 334413, Ukraine e-mail: pkv@crao.crimea.ua

** Institute of Biology of Southern Seas, Nahimova prospekt 2, Sevastopol 335011, Ukraine; e-mail: parch@ibss.iuf.net

Abstract

Various equations describing growth of organisms are considered. Some of them although widely used in biology are not correct and should not to be used for the growth rate calculations. Average estimation of growth rate appears rough and unreliable relative to the instant one. An approach is suggested that allows to infer the instant growth rate from experimental data directly without appealing to any standard growth rate models. The approach is based on approximation of the original data by cubic splines that have first and second derivatives, while subsequent analytic differentiation of that polynomial function allows to calculate the instant growth rate using minimisation of the medium risk function. This approach is very sensitive and makes it possible to observe the whole dynamics of the growth within the given interval. Its advantages are illustrated by the data on red algae Gracilaria verrucosa growth rate.