Диатомовая водоросль Didymosphenia geminata: распространение и экология

Species of single celled organism

Didymosphenia geminata, commonly known as didymo or rock snot, is a species of diatom that produces nuisance growths in freshwater rivers and streams with consistently cold water temperatures and low nutrient levels. It is native to the northern hemisphere, and considered an invasive species in Australia, Argentina, New Zealand, and Chile. Even within its native range, it has taken on invasive characteristics since the 1980s. but it can affect stream habitats and sources of food for fish and make recreational activities unpleasant. This microscopic alga can be spread in a single drop of water.]] Didymosphenia geminata is a diatom, which is a type of single celled organism unique for their silica (SiO2) cell walls. The life history of diatoms includes both vegetative and sexual reproduction, though the sexual stage is not yet documented in this species. Although it is symmetric only along the apical axis, typical of gomphonemoid diatoms, it is a cymbelloid, which are typically symmetric along both primary axes. Cells contain a raphe, which allows them to move on surfaces, and an apical porefield, through which a mucopolysaccharide stalk is secreted. The stalk can attach to rocks, plants, or other submerged surfaces. When the diatom cell divides, through vegetative reproduction, the stalk divides too, eventually forming a mass of branching stalks. The nuisance build up is not the cell itself, but their massive production of extracellular stalks. Extracellular polymeric substances (EPS) that form the stalks are made primarily of polysaccharides and protein, forming complex, multi layered structures that are resistant to degradation. The distribution of didymo in the last two decades appears to be gradually expanding outside its native range. Even within its native range, there have been reports of excessive growths in areas where it previously existed only in low concentrations. Didymo is now considered likely to be native to New York.

Buryatia Widespread across large areas of Russia. Occurrence, ecology, water quality, and scanning electron micrography of D. geminata from Irokinda Mine Site, Buryatia, John G. Aronson, North American Diatom Symposium, Sept, 2011.

Alberta: Earliest anecdotal reports of D. geminata blooms in Alberta rivers occurred as early as the mid 1990s (e. g. the upper Bow River in Banff National Park). Reports of Didymo presence and bloom formation have been documented for most rivers in the South Saskatchewan River Basin in recent years (2005 to present). British Columbia: D. geminata was first reported as a nuisance species in the late 1980s on Vancouver Island. Since that time, outbreaks of Didymo have been reported on the island and on the mainland. Quebec: D. geminata was first officially reported in 2006 but a recent report demonstrates that it was present in the sediments back in the 70s at the least. New Brunswick: D. geminata was first reported in 2007. Ontario: D. geminata was reported in the upper St. Marys River in 2015 and 2016.

Chile: In 2010, the United States Geological Survey (USGS) and a Chilean laboratory, Centro de Investigacion en Ecosistemas de la Patagonia (CIEP), confirmed the identification of the diatom D. geminata (didymo) as forming extensive blooms in Chilean rivers in Chile's Los Lagos Region (X Región de Los Lagos) in the Andes west of Esquel, a town in the Chubut Province of Argentina, with reports from the Espolon River and the Futaleufú River for a total of more than 56 river kilometers affected.

D. geminata was discovered in New Zealand in 2004, the first time it was found in the southern hemisphere. To restrict its spread, the whole of New Zealand's South Island was declared a controlled area in December 2005. Extensive publicity was carried out to limit the spread, but it has subsequently been found in an increasing number of rivers there.

In the Gaspésie region of Quebec, a paleolimnological study was performed to (i) assess the validity of claims that didymo is in fact an introduced species in Quebec and (ii) explore potential mechanisms underlying the recent proliferation of didymo in the region. It was found that recent invasion or transfer to the Gaspésie region is a highly unlikely explanation for post 2006 didymo blooms. It was demonstrated that freshwater systems in Gaspésie are responding to recent climate warming. Given didymo’s habitat and environmental preferences, it was proposed that climate related changes in regional rivers are likely an important factor that favors its proliferation. Dr. Max Bothwell at Environment Canada claims that phosphorus poor streams create blooms of the algae. The research paper, "Blooms of benthic diatoms in phosphorus poor streams" was first published in March 2017.