Study

Stable or changing lakes? A classification of aquatic macrophyte assemblages from a eutrophic shallow lake system in the United Kingdom

  • Published source details Kennison G.C.B., Dunsford D.S. & Schutten J. (1998) Stable or changing lakes? A classification of aquatic macrophyte assemblages from a eutrophic shallow lake system in the United Kingdom. Aquatic Conservation: Marine and Freshwater Ecosystems, 8, 669-684.

Summary

Action: Control populations of wild vertebrates

A before-and-after study in 1983–1995 of a lake in England, UK (Kennison et al. 1998) reported that after removing most fish, there were changes in the community composition and abundance of aquatic macrophytes. Statistical significance was not assessed. Over six years after fish removal, there were changes in the overall macrophyte community composition – although the overall community type remained similar (data reported as a graphical analysis). The total abundance of macrophytes was greater in the six years after fish removal than in the six years before (data reported as abundance scores). Accordingly, some individual species were more abundant after fish removal than before, e.g. macroalgae Enteromorpha sp. (especially after 1–2 years), filamentous algae (especially after 3–4 years), and coontail Ceratophyllum demersum and horned pondweed Zannichellia palustris (especially after 5–6 years). Methods: From 1989, electrofishing and seine netting dramatically reduced the fish population in Cockshoot Broad (see also Moss et al. 1996). Earlier attempts to reduce nutrient levels were isolation from nutrient-rich input water and sediment dredging (early 1980s) and improved sewage treatment (1985). Submerged and floating macrophytes were surveyed with a grapnel each summer 1983–1995 (894 m of permanent transects/year).

 

Action: Control populations of wild vertebrates

A before-and-after study in 1983–1995 of a lake in England, UK (Kennison et al. 1998) reported that after removing fish, there were changes the community composition and abundance of aquatic macrophytes. Statistical significance was not assessed. In the summer after fish removal, the overall macrophyte community composition differed from the previous years (data reported as a graphical analysis). Macrophytes were far more abundant in the summer after fish removal than in 7 of 10 years before fish removal – including the most recent surveys, 2–3 years before fish removal (data reported as abundance scores). The most abundant species after fish removal was sago pondweed Potamogeton pectinatus. It was far more abundant, and comprised a greater proportion of the community, than in any previous years. Methods: In early 1995, fish were removed from Ormesby Broad (further details not reported). Submerged and floating macrophytes were surveyed with a grapnel each summer 1983–1995 (1,504 m of permanent transects/year).

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