The vertical structure of the vegetative canopy of the brown algae Cystoseira (Black Sea)

Abstract

In the coastal ecosystems of the Black Sea, macrophytobenthos and, in particular, the association of Cystoseira crinite, C. barbata, Cladostephus verticillatus, and Corallina mediterranea, with its thick vegetative canopy (VC), is the key contributor to primary production (PP). Though the vertical structure of the canopy, formed by the algal association, is of principal importance to the PP level, this subject has been long-neglected by researchers. The goal of our work was to compare vertical structures of the vegetative canopy of Cystoseira brown algae under diverse hydrodynamical conditions of the Crimean Peninsula coast. Samples were collected using the 50 cm×50 cm counting frame at eight stations positioned in shallow (55–60 cm deep) sites of Sevastopol Bay (Crimean Peninsula). Dry weight biomass of the VC was determined for all algae assemblage and for each algal species individually, per horizontal surface unit, at each height (Z). The study shows that: 1) the VC is characterized by unimodal vertical distribution of biomass, with maximum estimate in the lower part, where the biomass increases to 85% of the total biomass; 2) a series of single-peaked curves reliably describes the unimodal distribution of the biomass; thalli of different age groups are found along the canopy profile; and 3) algae found in epiphytic synusia prefer inhabiting the upper part of the VC. The role of environmental factors (seawater turbulence and solar radiation) is discussed in reference to the formation of the vertical structure, made up of the associations of the brown algae Cystoseira.