Benthic Diatom Didymosphenia Geminata Research Articles

Glacier recession alters stream water quality characteristics facilitating bloom formation in the benthic diatom Didymosphenia geminata

Glaciers provide cold, turbid runoff to many mountain streams in the late summer and buffer against years with low snowfall. The input of glacial meltwater to streams maintains unique habitats and support a diversity of stream flora and fauna. In western Canada, glaciers are anticipated to retreat by 60–80% by the end of the century, and this retreat will invoke widespread changes in mountain ecosystems. We used a space-for-time substitution along a gradient of glacierization in western Canada to develop insights into changes that may occur in glaciated regions over the coming decades. Here we report on observed changes in physical (temperature, turbidity), and chemical (dissolved and total nutrients) characteristics of mountain streams and the associated shifts in their diatom communities during de-glacierization. Shifts in habitat characteristics across gradients include changes in nutrient concentrations, light penetration, temperatures, and flow, all of which have led to distinct changes in diatom community composition. Importantly, glacial-fed rivers were 3–5 °C cooler than rivers without glacial contributions. Declines in glacial meltwater contribution to streams resulted in shifts in the timing of nutrient fluxes and lower concentrations of total phosphorus (TP), soluble reactive phosphorus (SRP), and higher dissolved inorganic nitrogen (DIN) and light penetration. The above set of conditions were linked to the overgrowth of the benthic diatom Didymosphenia geminata. These changes in stream condition and D. geminata colony development primarily occurred in streams with marginal (2–5%) to no glacier cover. Our data support a hypothesis that climate-induced changes in river hydrochemistry and physical condition lead to a phenological mismatch that favors D. geminata bloom development.

Blooms of benthic diatoms in phosphorus‐poor streams

Blooms of benthic diatoms in phosphorus‐poor streams

Influence of Didymosphenia geminata Blooms on Prey Composition and Associated Diet and Growth of Brown Trout

AbstractWe compared diet, stomach fullness, condition, and growth of Brown Trout Salmo trutta among streams with or without blooms of the benthic diatom Didymosphenia geminata in the Black Hills, South Dakota. In Rapid Creek, where D. geminata blooms covered ∼30% of the stream bottom, Brown Trout consumed fewer ephemeropterans (6–8% by weight) than individuals from two stream sections that have not had D. geminata blooms (Castle and Spearfish creeks; 13–39% by weight). In contrast, dipterans (primarily Chironomidae) represented a larger percentage of Brown Trout diets from Rapid Creek (D. geminata blooms present; 16–28% dry weight) compared with diets of trout from streams without D. geminata blooms (6–19% dry weight). Diets of small Brown Trout (100–199 mm TL) reflected the invertebrate species composition in benthic stream samples; in Rapid Creek, ephemeropterans were less abundant whereas dipterans were more abundant than in streams without D. geminata blooms. Stomach fullness and condition of Brown Trout from Rapid Creek were generally greater than those of Brown Trout from other populations. Linkages among invertebrate availability, diet composition, and condition of Brown Trout support the hypothesis that changes in invertebrate assemblages associated with D. geminata (i.e., more Chironomidae) could be contributing to high recruitment success for small Brown Trout in Rapid Creek.

Didymo Control: Increasing the Effectiveness of Decontamination Strategies and Reducing Spread

ABSTRACTNuisance algal blooms formed by the benthic diatom Didymosphenia geminata (didymo) have been spreading rapidly, with negative ecological and economic effects. This microscopic alga is transported on fishing equipment, and controlling the spread of didymo involves proper cleaning of gear. Our study experimentally tested several common decontamination treatments and determined the response of state agencies and fishermen to decontamination procedures. In testing decontamination products, we found that dish liquid detergent was the most effective, followed by bleach, Virkon, and salt. Decontaminants were more effective on cells that were not still attached to their stalks. From the fishermen's perspective, didymo was the aquatic invasive species of highest concern, but there was a wide range of approaches to didymo control. Our final recommendations concentrate on the importance of comprehensive information sources and standards for didymo decontamination and education, specifically, and for invasive/nuisance species more generally.

Phosphorus limitation of the freshwater benthic diatom Didymosphenia geminata determined by the frequency of dividing cells

SUMMARY 1. Unlike other nuisance algal species, the freshwater benthic diatom Didymosphenia geminata typically forms blooms in low-nutrient rivers. The negative association between D. geminata blooming behaviour and nutrient levels appears at both catchment and smaller scales. We conducted a series of trials in streamside experimental channels colonised with D. geminata using water from the D. geminata-affected, oligotrophic Waitaki River, South Island, New Zealand to determine how elevated nitrate and phosphate concentrations affected D. geminata cell division. Because D. geminata blooms are typically most pronounced in unshaded waters, we also investigated the growth response to shading. In all experiments, we used the frequency of dividing cells (FDC) as a metric of cell division. 2. Concentrations of nitrate and dissolved reactive phosphorus (DRP) in the Waitaki River were very low (4 mg m )3 NO 3 -N and <1 mg m )3 DRP). In pilot trials, substrata colonised by D. geminata were subjected to enrichment by either switching the water source to N- and P-rich spring water or by adding a stock NO 3 PO 3 solution. Both trials resulted

On the Boots of Fishermen: The History of Didymo Blooms on Vancouver Island, British Columbia

AbstractIn 1989 blooms of the river benthic diatom Didymosphenia geminata (didymo) first appeared and rapidly spread among rivers on central Vancouver Island, covering the bottoms with thick, woolly‐looking mats. Although didymo is native to North America, extensive field surveys of rivers on Vancouver Island and other data indicate that didymo blooms are new. No known environmental changes were associated with the onset of didymo blooms. However the pattern of didymo spread among rivers on Vancouver Island correlates with the activity of fishermen and the commercial introduction and widespread use of felt‐soled waders in the late 1980s. Since 1994 nuisance blooms of didymo have appeared in numerous other places in the Northern Hemisphere and South Island, New Zealand, all areas frequented by fishermen. Actions by government agencies to educate the public and restrict the use of felt‐soled waders have been undertaken in some jurisdictions and at least one commercial manufacturer of waders will discontinue production of felt‐soled models in the near future.

Didymosphenia geminata (Protista, Bacillariophyceae) invasion, resistance of native periphyton communities, and implications for dispersal and management

Historically described as cosmopolitan but rare, the benthic diatom Didymosphenia geminata is now considered a nuisance, bloom-forming and invasive species. In New Zealand, D. geminata was first recorded in 2004 in the lower Waiau River. By winter 2008 it had been identified in 26 major catchments. To investigate invasion success of D. geminata in relation to succession and biomass accumulation of native periphyton communities, we conducted a two-factorial field experiment. Seven successional stages of a native periphyton community (substrate exposure time: 0–49 days) were exposed to two D. geminata propagule concentrations (low and high) for 25 days. D. geminata propagule concentration and successional stage of the native periphyton community significantly affected the invasion success of D. geminata. While D. geminata invasion was low on all substrates that had been exposed to the low D. geminata propagule concentration, there was a unimodal relationship between invasion success and substrate exposure time at the high propagule concentration. D. geminata abundance was low on uncolonised substrates, increased when the native communities were 1- or 2-week-old, and low when the age of the native communities was 4 or more weeks. These results imply that D. geminata is a late successional species that needs some existing structure to anchor to a substrate. Although late successional stages of the native periphyton community displayed partial resistance to D. geminata invasion, trying to keep D. geminata abundances as low as possible appears to be the only way to manage this species at this time.