Restoration of submerged vegetation in shallow eutrophic lakes – A guideline and state of the art in Germany

Abstract

One of the most serious problems caused by eutrophication of shallow lakes is the disappearance of submerged macrophytes and the switch to a turbid, phytoplankton-dominated state. The reduction of external nutrient loads often does not result in a change back to the macrophyte-dominated state because stabilising mechanisms that cause resilience may delay a response. Additional internal lake restoration measures may therefore be needed to decrease the concentration of total phosphorus and increase water clarity. The re-establishment of submerged macrophytes required for a long-term stability of clear water conditions, however, may still fail, or mass developments of tallgrowing species may cause nuisance for recreational use. Both cases are often not taken into account when restoration measures are planned in Germany, and existing schemes to reduce eutrophication consider the topic inadequately.Here we develop a step-by-step guideline to assess the chances of submerged macrophyte re-establishment in shallow lakes. We reviewed and rated the existing literature and case studies with special regard on (1) the impact of different internal lake restoration methods on the development of submerged macrophytes, (2) methods for the assessment of natural re-establishment, (3) requirements and methods for artificial support of submerged macrophyte development and (4) management options of macrophyte species diversity and abundance in Germany. This guideline is intended to help lake managers aiming to restore shallow lakes in Germany to critically asses and predict the potential development of submerged vegetation, taking into account the complex factors and interrelations that determine their occurrence, abundance and diversity.

Effect of excess iron and copper on physiology of aquatic plant Spirodela polyrrhiza (L.) Schleid

“…To improve the water quality and to control the formation of cyanobacterial blooms, a lot of physical, chemical and biological measures have been used in the restoration of aquatic ecosystem. However, experimental studies on effects of these measures, especially chemical reagents addition, on growth of aquatic plants are very lacking (Hilt et al, 2006). As is well known, iron and copper are often applied to kill bloom-forming cyanobacteria (Hullebusch et al, 2002) and improve water quality (Haughey et al, 2000), however, this may cause secondary pollution of water environment.…”

Effects of water nutrients on regeneration capacity of submerged aquatic plant fragments

“…The combination of the mostly free-floating growth form and the high regeneration capacity under high nutrients seems one of the key parameters for the weed potential of this species, particularly in eutrophic waters, in both its native and introduced range (Wells et al, 1997;Hilt et al, 2006). Myriophyllum heterophyllum, which was documented to have a much higher regeneration capacity in a study with sediment (Hussner, 2008), regenerated mostly by roots.…”

Disentangling natural and anthropogenic drivers of changes in a shallow lake using palaeolimnology and historical archives

“…Low growing species, like Characeae, are desirable in lakes used for recreation, but achieving Charadominated lakes is challenging when applying restoration measures (Hilt et al, 2006). In the case of Lake Rotcze this type of vegetation developed spontaneously, probably because of lower water levels, counteracting a potential shift into phytoplankton dominated state, even though the lake was becoming increasingly productive.…”

“…The presence and diversity of macrophytes are important in lake ecosystem evaluation for nature conservation (Salgado et al, 2010) and macrophyte-dominated, clear-water lakes are often the target of lake restoration measures (Moss, 1998;Hilt et al, 2006;Ogdahl & Steinman, 2014). Substantial changes to the dynamics and composition of submerged plant communities have occurred over the last 200 years in many shallow Northern European lakes including sites from the UK (Davidson et al, 2005, Ayres et al, 2008, Sayer et al, 2010aSalgado et al, 2010;Bennion et al, 2011a, b), Denmark (McGowan et al, 2005) and Poland .…”