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The freshwater zebra mussel Dreissena polymorpha is a powerful biofouling bivalve, which has tremendous impact on industrial facilities whose operation depends on the intensive use of freshwater, such as waterworks and power stations. The control of the pest in industrial environments remains a major challenge due to low selectivity over non-target organisms and the expense of the large quantities of biocides required. A novel delivery technique involving the encapsulation of a toxin within hundred micron-sized particles, edible for the bivalves, has been recently proposed. This strategy exploits the mussels' filtration activity and minimises their avoidance responses to certain chemicals, resulting in an increase of their susceptibility to the biocide. In the present paper, which further develops this approach, a new, promising toxin-loaded paniculate formulation is presented. The effectiveness of the product as a molluscicide has been demonstrated in laboratory bioassays. Encapsulation was observed to reduce the amount of biocide required to achieve 90% mortality in a 12-h treatment by a factor of approximately three. The dependence of the biocide-loaded panicles' molluscicidal activity on their physical characteristics is also illustrated in this paper by comparing the features of the promising formulation to those of an unsuccessful paniculate product. [ABSTRACT FROM AUTHOR]

In recent years biofouling from native (bryozoans, sponges) and non-native (Cordylophora) animals has increased in UK water treatment works (WTW). A survey of six UK water companies and eight WTWs revealed that these taxa were more widespread and abundant than previously recognised. Primary problems related to the occlusion of underfloor nozzles and tailpipes in rapid gravity filter beds (RGFs). These cost the UK water industry £1.49 m between 2005 and 2009. Additional impacts came from skin irritation to operatives from sponge spicules and the potential for elevated bacterial pathogen levels. Sponges penetrated the furthest through the water treatment process, reaching the point of final chlorination at one WTW. A monitoring plate study showed pronounced seasonality in fouling, with most taxa peaking in mid to late summer before a winter die-off. Control options, including the use of chlorine, and the importance of resistant stages for each taxon are discussed. [ABSTRACT FROM AUTHOR]

This study investigated host specialisation in an unusual symbiosis between a species of fish, the European bitterling (Rhodeus scriceus:family Cyprinidae, subfamily Acheilognathinae), and four species of freshwater mussels (family Unionidae) which bitterlings use for spawning. A field study from a single site in England examined four aspects of host use. First, comparisons among mussel species showed significant differences in production of bitterling young: Unio pictorum released the most young fish, followed in order by Anodonta anatina, Unio tumidus, and Anodonta cygnea. These findings pertained to mussels which had received eggs naturally, and were repeated in an experimentin the wild which controlled for mussel density and prior occupancy by bitterling embryos. Second, there were no significant differences within species in host productivity according to mussel size for individuals >60 mm in length. Third, field manipulations indicated microhabitat differences in host use which depended on the mussel species: U. pictorum individuals were used most heavily when closest to the river bank, whereas the opposite trend occurred for U. tumidus and A. anatina. Finally, the total productivity of mussels which had been clustered in groups of three was three times higher than single individuals. This latter effect suggests a benefit to males from choosing to defend groups of mussels. Benefits from specialisation among mussel species are not clear, but host use may reflect the broader context ofoverlaps between the fish and mussels in habitats. The ranges of allfour mussel species overlap widely with those of bitterlings, but the least-used mussel species, A. cygnea, has the least habitat overlapwith bitterlings, suggesting the potential for weaker selection on the fish for host recognition or adaptation to this species. [ABSTRACT FROM AUTHOR]

Algal and cyanobacterial blooms in reservoirs are driven by nutrient enrichment and may present economic and conservation challenges for water managers. Current approaches such as suppression of algal growth with barley straw, ferric dosing or manipulation of fish stocks have not yielded long term successes. A possibility that has sparked growing interest is the encouragement and cultivation of natural filter feeders, such as mussels, which remove suspended matter from the water and reduce nutrient levels through biodeposition and assimilation. This review focusses on the zebra mussel (Dreissena polymorpha) as a tool for enhancement of water quality in reservoirs. Native to the Ponto-Caspian region, this species has invaded many lakes and reservoirs across North America and Western Europe, where it occurs in very high densities. While purposeful introduction of a non-native species into new sites is socially unacceptable, we investigate the possible benefits of encouraging increased abundance of zebra mussels in sites where the species is already established. We estimate that the annual nitrogen and phosphorus input into a large UK reservoir (Grafham Water) could be assimilated into zebra mussel biomass by encouraging settlement onto 3075 m and 1400 m of commercial mussel ropes, respectively. While zebra mussel cultivation has an incredible capacity to push eutrophic systems towards a clear water state, there are many risks associated with encouraging an invasive species, even within sites where it has already established. The zebra mussel is a prominent biofouler of native unionid mussels and raw water pipes, it changes the physical characteristics of the places it inhabits, in sites low in phosphorus it can be responsible for toxic cyanobacterial blooms, it alters nutrient cycling and community structure and it can have negative impacts on amenity value. Increased propagule pressure from elevated numbers of veliger larvae in the water column may increase the risk of spread to other locations. This may render some reservoir systems, such as dammed rivers which have outflows to downstream watercourses, unsuitable for cultivation. Such reservoirs are especially common in North America. We consider the practicalities of putting a zebra mussel cultivation system into place and identify gaps in knowledge. We conclude that zebra mussel cultivation offers an attractive tool for managing nutrient-enriched reservoirs, but that the benefits and costs must be balanced on a site-by-site basis., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Cordylophora caspia is a hydrozoan which causes biofouling in power plants and is an increasing problem in UK drinking water treatment works. Thermal control is not usually feasible without a ready source of hot water so laboratory experiments were conducted to assess whether using pulsed doses of chlorine is an alternative solution. C. caspia polyps disintegrated after a single 20 min dose (the length of one backwash cycle in water treatment work filter beds) of 2.5 ppm chlorine. Without further treatment colonies regenerated within 3 days, but repeated dosing with chlorine for 20 min each day inhibited this regeneration. The resistance of surviving colonies to chlorine increased over time, although colony size and polyp regeneration continued to fall. These results suggest pulsed treatment with chlorinated backwashes at 2 ppm could be used to control C. caspia biofouling in rapid gravity filters and this may have relevance to other settings where thermal control is not feasible.