Reproduction of the Invasive Species Bonnemaisonia hamifera Hariot near the Southern Coast of Crimea (Black Sea)

During the study of the macrophytobenthos annual cycle of the aquatic component in the Cape Martyan Reserve, it has been found that sporophytes of the invasive transforming species Bonnemaisonia hamifera Hariot (Trailliella phase), naturalized in coastal waters off the Southern Coast of Crimea (SCC), abundantly form specialized organs of asexual reproduction. Mature tetrasporangia were registered in autumn at every zone of the phytal. Their morphology and morphometry, which have an important diagnostic value, were identified and measured. It was found that any thalli cells (except apical ones) could turn into sporangia, with the maximum number being formed in the terminal branches, where rows of up to 3–4 pcs are most common. Considering the fact that the formation of tetrasporangia occurs only in a narrow range of light-temperature conditions of a short day typical for autumn and spring, we showed that in the SCC the favorable period for this process lasts from the first decade of October to the second decade of December. In spring, in deep open water areas near the SCC, under modern climatic conditions, the formation of tetrasporangia is limited by water temperature, and therefore is unlikely. However, in relatively isolated shallow bays and lagoons, characteristic of other coastal regions of the Azov-Black Sea basin, it is possible due to local water temperature rise in the first half of March. Still, the ability of sporophyte thalli for vegetative reproduction by forming an unlimited number of fragments, that retain their viability and the potential for further fragmentation, remains likely the key factor ensuring the scale and rapid spread of B. hamifera in the SCC and in the Azov-Black Sea region as a whole.