On the status of seagrass communities in the Black Sea

There are six species of seagrasses in the Black Sea: Zostera marina (eelgr ass), Z. noltii, Potamogeton pectinatus, Ruppia maritima, R. spiralis and Z annichellia 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 as hore is estimated to be 50,000 wet tonne. Classification of Black Sea bottom vegetation distinguishes five associatio ns of seagrasses. The most comprehensive knowledge has been gained about Zo stern communities; The largest number of plant species concentrate at the 1 to 5 m depths, Algae with short Life cycles, mostly red algae, dominate th ese phytocenoses. Epiphytic and unattached forms usually prevail over litop hytic forms. Typical representatives of the algal flora are species of gene ra Ceramium, Cladophora, Enteromorpha, Kylinia and Polysiphonia. Quantitative characteristics of eelgrass are higher in pure phytocenoses th an in mixed ones. Estimates were greatest for the depth 3 m. Ecophytocenosi s optimum for eelgrass is in mixed phytocenosis with Gracilaria verrucosa g rowing at 5 m. Actual seed production yielded by eelgrass in Sevastopol Bay and adjacent areas is 4847 seed m(-2). Peaks of vegetative reproduction ar e in spring and autumn when lateral shoots are formed most intensively. The eelgrass biocenosis provides a habitat to a diversity of marine organis ms. Being an important element of coastal ecosystem, seagrasses have been p ut under protection in two nature reserves, e.g., Chernomorsky and Azovosiv ashsky. (C) 1999 Elsevier Science B.V. All rights reserved.