Abstract
Ponds throughout the world are subjected to a variety of management measures for purposes of biodiversity conservation. Current conservation efforts typically comprise a combination of multiple measures that directly and indirectly impact a wide range of organism groups. Knowledge of the relative impact of individual measures on different taxonomic groups is important for the development of effective conservation programs. We conducted a field study of 28 man-made ponds, representing four management types differing in the frequency of periodic pond drainage and the intensity of fish stock management. We disentangled the relative importance of direct and indirect effects of pond management measures on the community composition of phytoplankton, zooplankton, aquatic macro-invertebrates, submerged and emergent vascular plants. With the exception of phytoplankton, pond management had strong effects on the community composition of all investigated biota. Whether management affected communities directly or indirectly through its impact on fish communities or local environmental conditions in the pond varied between organism groups. Overall, the impact of pond drainage regime and fish community characteristics on the community composition of target organism groups were more important than local environmental conditions. The majority of taxa were negatively associated with fish density, whereas multiple emergent plant species and several taxa of aquatic macro-invertebrates were positively affected by increased drainage frequency. The effects of fish community and drainage tended to be largely independent. The present study indicates that pond drainage is an important element for biodiversity conservation in eutrophicated shallow and interconnected man-made ponds.
Highlights
Ponds are increasingly recognized for their high contribution to regional biodiversity [1,2,3,4] and the provisioning of vital ecosystem services [5,6,7,8,9]
We exploited the higher level of taxonomic detail available for Mollusca and Hemiptera and analyzed the community compositional variation of these groups separately at the species level. These analyses provide additional information since an analysis at the family level only may obscure group-specific response patterns resulting from the large differences in life history characteristics, feeding ecology, dispersal mode and physiology that exist among invertebrate groups
For the interpretation of the importance of management, we mainly focused on three components of explained variation: (1) the fraction of variation in community composition that can uniquely be attributed to pond management type
Summary
Ponds are increasingly recognized for their high contribution to regional biodiversity [1,2,3,4] and the provisioning of vital ecosystem services [5,6,7,8,9]. Increased human impact, such as nutrient loading, overstocking with fish and reduced water level fluctuation, have resulted in a worldwide deterioration of pond habitats [10, 11] and the local and regional loss of species [5, 12, 13]. A current challenge in conservation biology is the development of effective management programs that maintain and enhance biodiversity in anthropogenic landscapes. This is the case for man-made pond complexes in Western and Central Europe. Many of these systems have high conservation value but are increasingly threatened by the intensification of fish farming [10, 15, 16]
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