Growth, morphology and reproductive phenology of Gelidium adriaticum (Gelidiales, Rhodophyta) from the Slovenian coast (Gulf of Trieste, northern Adriatic)

Abstract

The occurrence, growth, external morphology and reproductive phenology of a Gelidium adriaticum population from the midlittoral zone in St. Simon Bay (Slovenian coast, Gulf of Trieste, northern Adriatic Sea) were investigated. The study was based on seasonal sampling conducted for one year, from winter to autumn 2023. The studied population was well developed in shaded rock crevices, forming dense turfs with a very patchy and irregular distribution. It was characterized by a slight predominance of tetrasporic plants, with a ratio between the three life stages (tetrasporic: vegetative: cystocarpic) of 1.19: 1.04: 1.00. The mean values of the morphological characteristics studied (height and width of the thallus, width of the widest part of the thallus axis, width of the apical, middle and basal parts of the erect axes) varied between seasons and life stages. In general, these values were lower in the cystocarpic specimens than in the tetrasporic and vegetative stages in all seasons.