Benthic macrocrustacean and insect assemblages in relation to spring habitat characteristics: patterns in abundance and diversity

Abstract

We studied variation in benthic macrocrustacean and insect assemblages in relation to spring habitat characteristics in six springs located in a single groundwater area in south-west Finland. We defined five habitat types in the studied springs according to water flow and benthic substrate characteristics: minerogenic brooks, organogenic brooks, helocrenes, floating moss carpets and limnocrene pools. Most studied invertebrate orders, as well as individual taxa, showed differences in relative abundances between the habitat types, but the most common taxa occurred in all springs and habitat types. The studied macroinvertebrates were most abundant in the moss carpet sites and least abundant in the pool sites, but the difference was not statistically significant. We did not observe significant differences in mean taxonomic richness per sample between habitat classes. The observed taxonomic richness in pooled samples of habitat classes was highest in moss carpet habitat and lowest in pool habitat, and the rarefied richness estimate was lowest in pool habitat. Benthic macrocrustacean and insect assemblages varied more between habitat types than between individual springs. In an Nonmetric Multidimensional Scaling ordination analysis, spring brook sites were separated from the moss carpet and pool sites, whereas helocrene sites were widely scattered among sites in other habitat classes. The strongest ecological gradients were related to water flow and the presence of minerogenic substrate, separating lentic and lotic habitats. Abundances of moss and coarse detritus accounted for most of the within-class variation. We identified several indicator species for minerogenic and organogenic brooks and for moss carpet and pool habitats, but none for the helocrenes. We found several occurrences of two crenobiont insect species considered threatened in Finland. We suggest that combined studies on macroinvertebrate and bryophyte assemblages would be a powerful approach in assessing the biodiversity of springs.

Crunoecia irrorata (Curtis) (Trichoptera: Lepidostomatidae) and conservation of boreal springs: indications of clustering of red‐listed species

“…The larvae of C. irrorata live among mosses, leaves and other suitable madicolous (terrestrial-aquatic interface) habitats in helocrenes and along spring brooks, and the species is referred to as a crenobiont species in European studies of spring fauna (Lindegaard et al, 1975(Lindegaard et al, , 1998Lauko¨tter, 1993;Cianficconi et al, 1998;Hoffsten and Malmqvist, 2000;Ilmonen and Paasivirta, 2005). However, it has also been recorded in lower reaches of headwater streams (e.g.…”

“…The springs included in the subset varied in size and complexity from small limnocrenes and rheocrenes to spring complexes covering several hectares. Some representative localities with information on the biota have been described by Ilmonen and Paasivirta (2005). The total area of each spring and the area of limnocrene pools, helocrenes, spring brooks with minerogenic or organogenic substrate, and moss habitats was estimated in the field using a classification based on a logarithmic scale (1: 510 m 2 , 2: 10-99 m 2 , 3: 100-999 m 2 , 4: 1000-9999 m 2 , and 5: 510 000 m 2 ).…”

“…Springs are often characterized by high habitat heterogeneity, which enhances biodiversity and accounts for much of the macroinvertebrate assemblage variation at both local and regional scales (e.g. Lindegaard et al, 1998;Ilmonen and Paasivirta, 2005). Moss carpets and helocrenes, where groundwater percolates through a layer of detritus or vegetation forming a marshy area with little open water, have been recognized as habitats with especially high invertebrate diversity, and as the most important habitat for many crenobiont invertebrates (species living exclusively in springs) (Lindegaard et al, 1975;Fischer, 1993;Lindegaard, 1995;Ilmonen and Paasivirta, 2005).…”

“…Lindegaard et al, 1998;Ilmonen and Paasivirta, 2005). Moss carpets and helocrenes, where groundwater percolates through a layer of detritus or vegetation forming a marshy area with little open water, have been recognized as habitats with especially high invertebrate diversity, and as the most important habitat for many crenobiont invertebrates (species living exclusively in springs) (Lindegaard et al, 1975;Fischer, 1993;Lindegaard, 1995;Ilmonen and Paasivirta, 2005). Permanence is also an important factor affecting the occurrence of spring-dwelling species (Erman and Erman, 1995;Hoffsten and Malmqvist, 2000;Smith et al, 2003).…”

“…Until recently, the macroinvertebrate fauna of springs in Fennoscandia has been the subject of very few studies (Hoffsten and Malmqvist, 2000;Ilmonen and Paasivirta, 2005). Owing to the poor knowledge of spring fauna, the spring-dwelling caddisfly C. irrorata (Curtis) (Trichoptera: Lepidostomatidae) was recorded in Finland for the first time in 1996 (Saarela, 1999).…”