On the status of seagrass communities in the Black Sea

Abstract

There are six species of seagrasses in the Black Sea: Zostera marina (eelgrass), Z. noltii, Potamogeton pectinatus, Ruppia maritima, R. spiralis and Zannichellia major. Eelgrass grows in shallow bays of the northwestern Black Sea in extensive underwater meadows. Following storm events, this species yields abundant litter on the beach. The biomass of eelgrass litter cast ashore is estimated to be 50,000 wet tonne. Classification of Black Sea bottom vegetation distinguishes five associations of seagrasses. The most comprehensive knowledge has been gained about Zostera communities. The largest number of plant species concentrate at the 1 to 5 m depths. Algae with short life cycles, mostly red algae, dominate these phytocenoses. Epiphytic and unattached forms usually prevail over litophytic forms. Typical representatives of the algal flora are species of genera Ceramium, Cladophora, Enteromorpha, Kylinia and Polysiphonia. Quantitative characteristics of eelgrass are higher in pure phytocenoses than in mixed ones. Estimates were greatest for the depth 3 m. Ecophytocenosis optimum for eelgrass is in mixed phytocenosis with Gracilaria verrucosa growing at 5 m. Actual seed production yielded by eelgrass in Sevastopol Bay and adjacent areas is 4847 seed m −2. Peaks of vegetative reproduction are in spring and autumn when lateral shoots are formed most intensively. The eelgrass biocenosis provides a habitat to a diversity of marine organisms. Being an important element of coastal ecosystem, seagrasses have been put under protection in two nature reserves, e.g., Chernomorsky and Azovosivashsky.