Temporal development of biodiversity of macrophytes in newly established lakes

Abstract

1. Every year, a vast number of wetlands are constructed to restore ecosystem function and biodiversity, thus counteracting massive historical losses by reclamation to farmland. However, our knowledge of the long-term effects on biodiversity, particularly of large systems such as lakes, is very limited.2. Our objective was to follow the development of macrophytes over 3-4 decades in 24 new, shallow, eutrophic lakes in order to test the hypotheses that: (1) species richness reaches a maximum after some years and then declines; and (2) species composition changes substantially from small early colonisers to taller, competitive later colonisers, which causes ongoing high β-diversity. A generalised linear mixed-effect model showed that species richness was relatedto lake size, phosphorus concentration and spatial setting, which are known to influence natural lakes as well. Moreover, species composition and richness were affected by lake age. Species colonised rapidly and richness peaked at an intermediate age and then declined.4. Temporal species turnover within lakes was high in three lake age groups of ≤10, 11-20 or >20 years since establishment, although lowest after 11-20 years.Species replacement tended to contribute most to β-diversity in the youngest lakes, whereas richness fluctuated in older lakes and appeared to contribute most to temporal turnover there. 5. Early colonisers in ≤10-year-old lakes were commonly replaced by tall canopyforming species in 11-20-year-old lakes, probably as a result of increasing competition for light and space over time. After 20 years, rootless Ceratophyllum submersum as well as species with floating and emergent leaves became dominant, potentially due to the gradual accumulation of more organic sediment difficult to root and grow in, along with gradually reduced light penetration in the water.6. Establishing new lakes for biodiversity remains a challenge because of the falling richness and continuous species turnover with lake age, but our results suggest that constructing large, nutrient-poor lakes in species-rich landscapes ensures the best prerequisites for obtaining diverse communities. K E Y W O R D Saquatic plants, community composition, ecological succession, restoration, wetlands

Biodiversity and Sediment Contamination in Wet Stormwater Ponds Depending on Design and Catchment Characteristics

“…Recent studies on a variety of new and reestablished Danish lakes, several of which resembling large stormwater ponds in form and function, have reached similar conclusions [65,66]. Shortly after their establishment, the new lakes exhibited a high biodiversity dominated by pioneer species of macrophytes and birds [65,66]. However, new sediment quickly formed and sediment organic content, P levels and the biodiversity of macrophytes and birds reached levels similar to eutrophic natural lakes within 20-30 years [67,68].…”

“…This would allow for a higher biodiversity in intervals or continuously depending on the excavation frequency. Recent studies on a variety of new and reestablished Danish lakes, several of which resembling large stormwater ponds in form and function, have reached similar conclusions [65,66]. Shortly after their establishment, the new lakes exhibited a high biodiversity dominated by pioneer species of macrophytes and birds [65,66].…”

Optimal physical design in a new lake for reducing phosphorus pools

“…An increasing focus on biodiversity and ecological quality of freshwater and marine habitats has inspired recent initiatives to reestablish former wetlands and lakes. In Denmark alone, approximately 100 lakes (>5 ha) have been created within the last 30 years to support biodiversity both in the lake and downstream, by reducing nutrient loading throughout the catchment (Stage Sø, Sand-Jensen & Baastrup-Spohr, 2020). Biodiversity, nutrient loading and ecological quality are essential management issues, according to the EU Water Frame Directive (European Parliament of the Council, 2000).…”

Groundwater–surface water interaction in Denmark

“…In the past 25 years, due to greater concern about environmental issues and a desire to increase biodiversity, about 50 large (>10 ha) Danish lakes have been re‐established in former lake basins (B. Hansen et al, 2012). Comprehensive studies of a few of these lakes (Kragh et al, 2022; Sø et al, 2020) show that rewetting of drained low‐lying organic‐rich agricultural areas to wetlands and lakes improves biodiversity and water quality, and changes greenhouse gas emission at the same time (Baastrup‐Spohr et al, 2016). Despite the economic impact of losing agricultural land, lake restorations have generated other values such as natural areas for recreation, improved conditions for biodiversity, and reduced nutrient transport to downstream coastal waters (Hoffmann & Baattrup‐Pedersen, 2007), which might also be converted into economic benefits.…”