Figure - uploaded by Klaus van de Weyer
Content may be subject to copyright.
Abb. 7-11, 7-12: Fraßschäden an Chara tomentosa (links: T 7: 1 m) und Nitellopsis obtusa (rechts: Transekt 5)
Citations
... Macrophyte surveys have been performed during the summers 1962 (Krausch, 1964), 2002, 2007(unpublished data of Landesumweltamt Brandenburg), 2008(Van de Weyer et al., 2009(Van de Weyer et al., 2015Fig. 1B). ...
... Finally, it has been shown in a modeling study and by a metaanalysis that epiphyton increases the susceptibility of macrophytes to herbivory (Hidding et al., 2016). An influence of herbivorous and benthivorous cyprinids on charophytes in Lake Stechlin has been suggested based on the increase of vegetation-free areas and typical sediment patterns indicating physical disturbance by benthivorous fish ( Van de Weyer et al., 2015). Negative effects on charophytes have been shown in other lakes for a number of fish species such as common carp (Laguna et al., 2016), grass carp (Krupska et al., 2012), bream (Ten Winkel and Meulemans, 1984) and rudd (Lake et al., 2002). ...
Groundwater influx can significantly contribute to nutrient budgets of lakes and its influence is strongest in shallow littoral areas. In oligo- or mesotrophic systems, additional nutrient supply by groundwater influx may affect benthic primary producers and their interactions. Potential changes can be expected in community composition, biomass, stoichiometry and interactions between submerged macrophytes and epiphyton.This study aimed at investigating whether enhanced epiphyton growth at sites with groundwater discharge may have contributed to a significant change in shallow littoral macrophyte abundance reported from oligo-mesotrophic Lake Stechlin during the last 50 years. In the 1960s, shallow littoral areas were dominated by small charophyte species such as Chara aspera, C. filiformis and C. rudis. Recent mappings indicated a strong decline of this shallow water charophyte community from 42. ha to 3. ha and a shift to the occurrence of macrophyte species typical of eutrophic lakes such as Potamogeton perfoliatus, P. pectinatus and Myriophyllum spicatum. We analyzed the nutrient content of macrophytes, and measured epiphyton growth at sites with different groundwater influence. Water column nutrient enrichment may have increased the abundance of eutrophic species, but this did not explain the decrease of charophytes. Our data suggest that enhanced epiphyton growth in shallow littoral areas with groundwater influx could impair the development of small charophytes by shading, increasing drag forces and the charophytes' sensitivity to herbivory.
• Humanity is facing a biodiversity crisis, with freshwater‐associated biodiversity in a particularly dire state. Novel ecosystems created through human use of mineral resources, such as gravel pit lakes, can provide substitute habitats for the conservation of freshwater and riparian biodiversity. Many of these artificial ecosystems are subject to a high intensity of recreational use, however, which may limit their biodiversity potential.
• The species richness of several taxa (plants, amphibians, dragonflies, damselflies, waterfowl, and songbirds) was assessed and a range of taxonomic biodiversity metrics were compared between gravel pit lakes managed for recreational fisheries (n = 16) and unmanaged reference lakes (n = 10), controlling for non‐fishing‐related environmental variation.
• The average species richness of all the taxa examined was similar among lakes in both lake types and no substantial differences in species composition were found when examining the pooled species inventory. Similarly, there were no differences between lake types in the presence of rare species and in the Simpson diversity index across all of the taxa assessed.
• Variation in species richness among lakes was correlated with woody habitat, lake morphology (surface area and steepness), and land use, but was not correlated with the presence of recreational fisheries. Thus, non‐fishing‐related environmental variables had stronger effects on local species presence than recreational fisheries management or the presence of recreational anglers.
• Collectively, no evidence was found that anglers and recreational fisheries management constrain the development of aquatic and riparian biodiversity in gravel pit lakes in the study region; however, the conservation of species diversity in gravel pit lakes could benefit from an increasing reliance on habitat enhancement activities.
