Variability of photosynthetic parameters of macroalgae and seagrasses based on laboratory experiments

Abstract

The PE-curve describes dependence of the macroalgae and seagrasses photosynthesis rate on the irradiance. To determine the main parameters of the PE-curve (photosynthetic parameters) at various temperatures and light intensities, an archive of laboratory experiments data was collected from the available published sources, and systematized (a total of 125 species of macroalgae and 14 species of seagrasses). The available data on the ratio of plant surface area to volume (SA:V) were added to the database. All macroalgae species were assigned to functional-form groups according to Littler [15], and an additional group “seagrasses” was determined.The data on photosynthetic parameters of macrophytobenthos were clusterized using the Ward's minimum variance criterion, which made it possible to identify clusters that differ greatly in the rate of photosynthesis. The composition of each cluster was determined within the framework of the classification by functional-form groups. The variability of functional parameters was studied by calculating the coefficients of variation within a functional-form group, cluster, and taxonomic division in a narrow temperature range.Graphs of the oxygen daily production by plants were plotted for different water temperatures to determine the temperature dependence of the photosynthesis rate. Using the method of constructing a neural network, the regression equations for the photosynthetic parameters were found in the form of polynomial dependencies on the morphological characteristics of algae: the SA:V ratio and the Littler group. With limited prognostic value, they illustrate well the qualitative changes in photosynthetic parameters during the transition from thin sheet-like and filamentous structures of thalli to coarser and more resistant ones.