Wetland Restoration with Hydrophytes: A Review

Introduction of Native Submerged Macrophytes to Restore Biodiversity in Streams

Streams are biodiversity hotspots that provide numerous ecosystem services. Safeguarding this biodiversity is crucial to uphold sustainable ecosystem functioning and to ensure the continuation of these ecosystem services in the future. However, in recent decades, streams have witnessed a disproportionate decline in biodiversity compared to other ecosystems, and are currently considered among the most threatened ecosystems worldwide. This is the result of the combined effect of a multitude of stressors. For freshwater systems in general, these have been classified into five main pressures: water pollution, overexploitation, habitat degradation and destruction, alien invasive species, and hydromorphological pressures. On top of these direct stressors, the effects of global processes like environmental and climate change must be considered. The intricate and interconnected nature of various stressors affecting streams has made it challenging to formulate effective policies and management strategies. As a result, restoration efforts have not always been successful in creating a large-scale shift towards a better ecological status. In order to achieve an improved status in these systems, situation-specific management strategies tailored to specific stressor combinations may be needed. In this paper, we examine the potential of introducing native submerged macrophyte species to advance the restoration of stream ecosystems. Through successful introductions, we anticipate positive ecological outcomes, including enhanced water quality and increased biodiversity. This research is significant, as the potential success in restoring stream biodiversity not only represents progress in ecological understanding but also offers valuable insights for future restoration and management strategies for these vital ecosystems.

Macrophytes in Inland Waters: From Knowledge to Management

The huge biodiversity of inland waters and the many different aquatic habitats or ecosystems occurring there are particularly threatened by human impacts. In this Special Issue, ten articles have been collected that show new data on the distribution and ecology of some rare aquatic macrophytes, including both vascular plants and charophytes, but also on the use of these organisms for the monitoring, management, and restoration of wetlands.

Understanding the ecological processes governing hydrophyte-associated bacterial communities involved in hydrophyte growth and development

Maintaining hydrophyte growth has been a major focus of aquatic ecological research. The hydrophyte microbiome plays a key role in the growth and health of hydrophytes, but the ecological processes regulating the assembly and function of hydrophyte microbial communities remain unclear. This knowledge gap limits the efficacy of managing microbiomes to enhance the capacity of hydrophytes to restore the aquatic environment. Here, we sampled three typical hydrophytes (Ceratophyllum demersum, Nymphoides peltatum, and Potamogeton crispus) to study the ecological process governing hydrophyte-associated bacterial communities. The results demonstrated that hydrophyte-associated bacterial communities were affected more by the hydrophyte host species (HEEI = 2.40) than by the environment (HEEI = 1.00). The hydrophyte host species not only affected bacterial community assembly, but reduced the diversity and network complexity of the bacterial community relative to that of the environment. Furthermore, the core taxa of two hydrophytes were identified. Chryseobacterium was the core taxon of N. peltatum, and Burkholderia-Caballeronia-Paraburkholderia, Pseudolabrys, and Pajaroellobacter were the core taxa of P. crispus. The core taxa of P. crispus were closely related to potential denitrification-related functions of bacteria and revealed that P. crispus played a role in denitrification during aquatic ecological restoration. Overall, the results of this study highlight the need to develop approaches employing hydrophyte-associated bacteria to promote the development of hydrophytes, which will be essential for increasing the utility of hydrophyte microbiomes in the future and enhancing aquatic ecological restoration.

Re-Establishment Techniques and Transplantations of Charophytes to Support Threatened Species

Re-establishment of submerged macrophytes and especially charophyte vegetation is a common aim in lake management. If revegetation does not happen spontaneously, transplantations may be a suitable option. Only rarely have transplantations been used as a tool to support threatened submerged macrophytes and, to a much lesser extent, charophytes. Such actions have to consider species-specific life strategies. K-strategists mainly inhabit permanent habitats, are perennial, have low fertility and poor dispersal ability, but are strong competitors and often form dense vegetation. R-strategists are annual species, inhabit shallow water and/or temporary habitats, and are richly fertile. They disperse easily but are weak competitors. While K-strategists easily can be planted as green biomass taken from another site, rare R-strategists often must be reproduced in cultures before they can be planted on-site. In Sweden, several charophyte species are extremely rare and fail to (re)establish, though apparently suitable habitats are available. Limited dispersal and/or lack of diaspore reservoirs are probable explanations. Transplantations are planned to secure the occurrences of these species in the country. This contribution reviews the knowledge on life forms, dispersal, establishment, and transplantations of submerged macrophytes with focus on charophytes and gives recommendations for the Swedish project.