Spatial Distribution and Diversity of Macroinvertebrates on the Stony Shore of a Subarctic Lake

Abstract

Quantitative samples taken with a new colonisation sampler over three years demonstrated a macroinvertebrate community of 25 taxa in the stony littoral of Takvatn, North Norway. The spatial variance was density-dependent and the 'index of aggregation' varied in the range 1.01-1.73 for 13 common taxa. The distribution was significantly aggregated for 10 taxa and close to random for three taxa. The taxon richness and diversity was lower than in southern oligotrophic Fennoscandian lakes but higher than in northern Swedish lakes. Takvatn had more Plecoptera and fewer Trichoptera than most other lakes. All Plecoptera and Ephemeroptera in the lake occur in northern Norwegian rivers and typically lotic species were prominent in the lake-shore community.

Variation in functional trait composition of benthic invertebrates across depths and seasons in a subarctic lake

“…Confirming our first hypothesis, the invertebrate community in the upper littoral habitat shifted from being dominated by organic particle gatherers and algal scrapers in spring and summer (mostly mayflies), to a community represented by almost 50% leaf shredders in autumn (mostly caddisflies and stoneflies). Seasonal changes in littoral species composition were also expected based on previous studies (Klemetsen & Elliott 2010) and are in agreement with expectations over the tight linkages between the lake littoral benthic community and the riparian zone (Johnson & Goedkoop 2002). This is particularly important in lakes with low autochthonous production on account of low temperatures, a short ice-free season, and low nutrient levels (Larsson et al 1978), such as subarctic and arctic lakes.…”

“…All samples were taken across one transect located in the SE end of the lake (Hauglibukta), which constitutes a typical nearshore habitat of Takvatn. The site is exposed to frequent winds and a wave action due to large fetch (>2 km), which results in a wave-washed, hard-bottom shoreline area with no vegetation (Klemetsen & Elliott 2010). The upper littoral habitat extends to about five meters from the shoreline and is characterized by large presence of boulders and pebbles.…”

“…The upper littoral benthos were sampled using a vacuum pump for 1 min inside a circular tray (ø = 60 cm) that is surrounded by 10 cm of nylon mesh (mesh opening = 0.45 mm) (see pump description in Klemetsen & Elliott 2010). All other sites were sampled using an Ekman grab (area 16 x 16 cm).…”

“…Compared to boreal and temperate systems, subarctic lakes show a less diverse and less abundant benthic community (e.g., Klemetsen & Elliott 2010). Nonetheless, shifts in invertebrate species composition and in the structure and function of benthic communities will impact higher trophic levels and the functioning of these ecosystems.…”

Diversity and abundance of water birds in a subarctic lake during three decades

“…Such prey were rarely found in the fish stomachs at that time (Amundsen & Klemetsen 1988), but came back as a result of the stock reduction of charr (Klemetsen et al 2002, unpublished data). They continue to have reasonably high densities in the littoral zone (Klemetsen & Elliott 2010). We believe that the high density of diving ducks in 2003 (Table 2) is related to this recurrence of attractive macro-invertebrates in the lake.…”