G.A. van Duinen

Do restoration measures rehabilitate fauna diversity in raised bogs? A comparative study on aquatic macroinvertebrates

To assess whether raised bog restorationmeasures contribute to the conservation andrestoration of the fauna diversity,macroinvertebrate species assemblages werecompared between water bodies created byrewetting measures and water bodies whichhave not been subject to restorationmeasures, but are remnants offormer peat cuttings and trenches used forbuckwheat culture in the past.The restoration sites were inhabited bycharacteristic raised bog species and rarespecies, but their numbers were higher atthe remnant sites not affected byrestoration management. A considerablenumber of characteristic and rare faunaspecies were only found at the remnantsites. The remnant sites includedconsiderably more variation inmacroinvertebrate species assemblages andhad a higher cumulative species richness.The number of characteristicmacroinvertebrate species was not clearlyrelated to the presence of a characteristicraised bog vegetation. In restoration sitesnumbers of rare and characteristic speciesper site tended to increase with the timeelapsed after rewetting. However,restoration measures will not automaticallyresult in restoration of a more or lesscomplete macroinvertebrate speciesspectrum, as restoration measures have sofar resulted in habitats for only a limitednumber of the characteristic species.When planning restoration measures, it isrecommended to protect the populations ofrare and characteristic species present inthe area, as these populations may becomethe sources for colonization of rewettedsites. Safeguarding habitat diversityduring the restoration process andrestoration of different elements of thehabitat diversity of complete raised bogsystems will result in the characteristicfauna diversity being conserved andrestored more successfully.

Biological traits successfully predict the effects of restoration management on macroinvertebrates in shallow softwater lakes

Many shallow softwater lakes are being affected by eutrophication and acidification. In these small lakes decaying organic material usually accumulates and characteristic plant and animal species disappear. In many degraded lakes organic matter and macrophytes are being removed in order to restore the lakes to their original state. To assess the effects of restoration management in softwater lakes on aquatic macroinvertebrates, changes in the species assemblages were studied in four degraded lakes in the Netherlands undergoing restoration measures. The degraded lakes still harboured species characteristic of pristine softwaters. However, most of these species were not recorded after restoration measures were taken. Species’ densities declined dramatically during the execution of restoration measures. Swimming and abundant species were more likely to survive the restoration measures than other species. The first years after restoration, the lakes did not meet the habitat requirements for a number of species. Species requiring vegetation for ovipositioning, animal food sources and swards of vegetation as habitat declined. Because recolonization is expected to be restricted, it is recommended to ensure the survival of relict populations when taking measures to restore degraded softwater lakes. This may be achieved by phasing restoration measures in space and time, hereby minimizing mortality during the execution of restoration measures and by preserving habitat conditions required by characteristic species.

Differential response of aquatic oligochaete species to increased nutrient availability - a comparative study between Estonian and Dutch raised bogs

To assess the effects of increased nutrient availability on aquatic oligochaetes in raised bogs, species assemblages were compared within and between fairly pristine raised bogs in Estonia and raised bog remnants in The Netherlands. Within the pristine bog landscape a distinct pattern in the species assemblage is present. In the most nutrient-poor water bodies, in the ombrotrophic raised bog, only the fragmenting, almost never mature, acid-tolerant species Cognettia sphagnetorum is present. In pristine Estonian raised bogs Nais variabilis, Lumbriculus variegatus and sexually reproducing species are limited to more minerotrophic water bodies, which have a higher decomposition rate of dead organic matter and, consequently, higher nutrient availability. With ten species the lagg zone is the most species-rich part of a pristine raised bog landscape. Most of these lagg zone species are not present in Dutch bog remnants as this part of the bog landscape has long been cultivated. Nais variabilis occurs in the Dutch bog remnants much more frequently than in Estonian bogs, whereas the frequency of C. sphagnetorum and L. variegatus is similar between both countries. These three species respond differently to the increased nutrient availability in The Netherlands, which could be linked to differences in their diets. In contrast to pristine bog pools, N. variabilis in Dutch raised bog remnants is present in water bodies not influenced by minerotrophic water. In Dutch raised bog remnants the occurrence of oligochaetes is not limited anymore by nutrient availability, due to the higher atmospheric nitrogen and sulphur loads in The Netherlands. Overall, it can be concluded that the degradation of Dutch raised bogs has resulted in the loss of both the nutrient-poor parts of the landscape and the special lagg conditions.

Methane as a carbon source for the food web in raised bog pools

Abstract.  Raised bog pools are extremely nutrient poor and rich in humic substances, and these features limit primary production. To assess the base of the invertebrate food web in bog pools we measured the stable-isotopic signatures of primary producers, dead organic matter, and invertebrates, and the composition and stable-C-isotope ratio of their phospholipid-derived fatty acids (PLFAs). The stable-isotopic signatures showed the presence of multiple trophic levels and differential use of basal food sources by the invertebrates among and within species, individuals, and size classes. Carnivorous and omnivorous invertebrates assimilated polyunsaturated fatty acids (PUFAs) derived from algae, and possibly macrophytes, and fatty acids that are specific for methane-oxidizing bacteria (MOB). Part of the bacterial biomass conveyed to higher trophic levels in the bog pools originated from MOB. Pelagic zooplankton appeared to rely more on bacteria, whereas insects relied more on algae. Periphyton, a primary algal food source, was the basal food source most depleted in 13C and was inferred to sustain ≥½ the invertebrate food web. The relatively depleted &dgr;13C values of PUFAs in invertebrates suggest a role for methane-derived C. We argue that the CO2 assimilated by the algae could be derived from MOB. Therefore, depleted &dgr;13C values of invertebrates do not necessarily indicate a direct pathway between MOB and these invertebrates because algae may form an intermediate level.