Fig 1.
Location of the 49 freshwater springs in Iceland investigated in this study.
Numbers refer to springs as listed in Table 2. The map was drawn using the map and mapdata libraries in R (https://cran.r-project.org/package=maps).
Table 1.
Environmental characteristics of the springs studied.
Table 2.
Invertebrates found in freshwater springs in Iceland.
Fig 2.
a-b. Diversity of invertebrates in Icelandic springs with respect to temperature. Shannon diversity (a) and Taxa richness (b) are shown in relation to spring temperature at the source (black dots) and the surface (white dots). Regression lines for the source samples are shown as continuous line and for the surface samples as broken line. The regression analysis is summarized in Table 5.
Table 3.
Dependence of alpha diversity indices on environmental variables and sampling location within each spring (source or surface).
Table 4.
Correlation matrix of some environmental variables from Icelandic springs.
Fig 3.
a-b. Non-metric multidimensional scaling of invertebrate taxa (a) and sites (b) for surface samples. Non-linear stress was 0.210. Significant associations (p < 0.05) of the environmental variables to the axes are shown with arrows (Ox = oxygen saturation, Type = spring type, Temp = temperature). Acronyms of invertebrate taxa (a) are listed in Table 2. Three clusters (I–III) of overlapping data points were defined for clarity reasons, containing the following taxa: Cluster I–Azo, CLA, Crt, Lim,Mac, Mic, NEM, OLI, Oob, OST, Ref, TAR; cluster II–Cha, Dia, Ofr; cluster III–Cri, Hyd, Lgr, Mfu, Ort, Pki, PLE, Thi. Spring sites (b) are classified as rheocrene and limnocrene springs.
Fig 4.
a-b. Non-metric multidimensional scaling of invertebrate taxa (a) and sites (b) for source samples. Non-linear stress was 0.18. Significant associations (p < 0.05) of the environmental variables to the axes are shown with arrows (Ox = oxygen saturation, Temp = temperature, Lat = Latitude). Acronyms of invertebrate taxa (a) are listed in Table 2. Spring sites (b) are classified as rheocrene and limnocrene springs.
Table 5.
Dependence of the invertebrate community composition on environmental variables and sampling location within each spring (source or surface).
Table 6.
Indicator species of rheocrene and limnocrene springs at the surface.