Transplanting aquatic macrophytes to restore the littoral community of a eutrophic lake after the removal of common carp

Abstract

Knopik J, Newman R. 2018. Transplanting aquatic macrophytes to restore the littoral community of a eutrophic lake after the removal of common carp. Lake Reserve Manage. 34:365–375.Six native submersed aquatic macrophyte taxa were transplanted to a eutrophic lake (Lake Susan, Minnesota) to promote the growth and expansion of native taxa after the removal of common carp (Cyprinus carpio). Muskgrass (Chara spp.), wild celery (Vallisneria americana), northern watermilfoil (Myriophyllum sibiricum), bushy pondweed (Najas flexilis), water stargrass (Heteranthera dubia), and flat-stem pondweed (Potamogeton zosteriformis) were transplanted in a series of shallow (0.5–1.0 m) and deep (1.0–1.5 m) experimental plots around the lake. Survival and expansion of plants were measured over 4 yr and compared against environmental factors. Transplantation of whole plants in shallow water was generally successful, but plants in depths ≥1.4 m failed to persist. Light availability was the most important factor determining success. Water stargrass was the most successful, with high long-term survival and substantial expansion. Wild celery had high survival, but slow and limited expansion. Bushy pondweed had variable survival, but when it survived it generally expanded well. Muskgrass and northern watermilfoil had poor survival and expansion. Transplanting whole submersed aquatic macrophytes can help to restore the littoral community in degraded systems, but ecological stressors such as common carp should first be addressed. Poor mid-summer water clarity will limit the depth and distribution of successful transplants and taxa that survive. Taxa with large perennial structures such as water stargrass and wild celery are more likely to establish and persist, but the annual bushy pondweed was also able to grow and spread.