Progressive restoration of a shallow lake: A 12-year experiment in isolation, sediment removal and biomanipulation
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Published source details
Moss B., Stansfield J., Irvine K., Perrow M. & Phillips G. (1996) Progressive restoration of a shallow lake: A 12-year experiment in isolation, sediment removal and biomanipulation. Journal of Applied Ecology, 33, 71-86.
Published source details Moss B., Stansfield J., Irvine K., Perrow M. & Phillips G. (1996) Progressive restoration of a shallow lake: A 12-year experiment in isolation, sediment removal and biomanipulation. Journal of Applied Ecology, 33, 71-86.
Summary
Action: Control populations of wild vertebrates
A before-and-after study in 1985–1993 of a lake in England, UK (Moss et al. 1996) reported that after removing most fish, the biomass of submerged macrophytes generally increased. Unless specified, statistical significance was not assessed. In the year before fish removal, submerged macrophyte biomass in the lake ranged from 0.006 g/m2 to 311 g/m2 across four study sites. In the two years after fish removal, submerged macrophyte biomass had increased in three sites (now 0.04–317 g/m2) and remained relatively stable in the other (207–389 g/m2). Biomass fluctuated over the following three years, ending up higher than before fish removal at two sites (17–23 g/m2) but lower than before fish removal in the other two sites (0.8–3.8 g/m2). Phytoplankton abundance was significantly lower in the five years after fish removal (20–30 µg chl a/L) than in the four years before (28–41 µg chl a/L). Methods: A major electrofishing and seine-netting effort was carried out in Cockshoot Broad in early 1989 and 1990. Remaining fish were removed in subsequent winters, leaving only a “small number” in the lake. Earlier attempts to reduce nutrient levels and phytoplankton populations were isolation from nutrient-rich input water and sediment dredging (early 1980s) and improved sewage treatment (1985; see Kennison et al. 1998). Submerged macrophytes were surveyed each summer 1998–1993 (four sites; 10–80 samples/site). Biomass was dried before weighing. Chlorophyll a was sampled monthly between 1985 and 1993.
Action: Use fences or barriers to protect planted areas
A replicated, controlled study in 1990 in a freshwater lake in England, UK (Moss et al. 1996) found that protecting pots of Canadian waterweed Elodea canadensis from waterfowl increased waterweed biomass. After three months, waterweed biomass was greater within exclosures (30 g/m2) than outside exclosures (1 g/m2). Methods: In May 1990, three exclosures (1 m3, covered in 5-cm mesh chicken wire) were established in Cockshoot Broad. Eighty pots of waterweed were placed in each exclosure. Eighty plots were placed nearby but outside exclosures. Waterweed was removed, dried and weighed in August 1990.
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