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1 Polish Journal of Ecology

1 2012

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Detrital components in submontane organogenic springs in relation to their morphology, microhabitats and macroinvertebrates

Ticha K., Simon O., Douda K., Kubikova L.

Polish Journal of Ecology

2012

Vol. 60, nr 1

163-175

Fine particulate organic matter (FPOM), originated by aggregation of smaller particles and by decomposition of bigger particles, usually presents the dominant energy and nutrient source in the primary river net. Relationships between detrital components, environmental factors and macroinvertebrate composition were investigated in 52 submontane organogenic spring areas in small catchment in the Sumava foothills, Czech Republic. All three types of springs (helocrenes, rheocrenes and limnocrenes) were represented, as well as springs with the transitional character. The selected springs were permanent, with water discharge higher than 0.1 L s[^-1], they all were coldwater and stenothermic, with the winter water temperature at the point of the source ranging from 2.0 to 9.9[degrees]C. At each spring area, the main morphological and physical characteristics of the spring and surrounding area were recorded. Samples of detritus were collected (using the 2 mL sampling tube) from up to 5 microhabitats at each spring, usually macrophyte vegetation, point of the source, detrital deposition, sand, algal mat, leaf litter or moss, accordingly to the microhabitats, which were present. Macroinvertebrates were semiquantitatively sampled using a 15-cm circular sampler with 0.8 mm mesh, to the orders or lower taxa were determined. Water samples were taken, and analyses of the main physico-chemical factors were carried out. In our set of springs, organic substrate prevailed. Only small differences in the physico-chemical parameters (e.g. pH = 5.96 [plus or minus] 0.39; mean [plus or minus] SD) and low concentrations of nutrients (e.g. N-NO3[^-] = 0.79 [plus or minus] 0.86 mg L[^-1], ortho-PPO4[^-] = 0.0336 [plus or minus] 0.0275 mg L[^-1]) were noted, whereas studied geomorphological parameters and microhabitat types were more diverse. The proportion of basic microscopically differentiable components of the detritus was similar in all spring types and microhabitats. In all study sites, faecal pellet content was dominant in the detritus (49%) followed by plant residuals (26%) and amorphous matter (21%). High faecal pellet content is considered to be a consequence of a steadily low temperature in the springs. The correlation among the presence of macroinvertebrate groups and particular detrital components content was not significant, except for Trichoptera; the abundance of this group was positively correlated with the proportion of plant residuals in detritus in vegetation microhabitats. Faecal pellet content showed a weak negative correlation with N-NH4 concentration, which is probably the result of faster faecal pellet decomposition in springs with higher N-NH4 contents.