Non-indigenous Aquatic Plant Research Articles

A Review and Secondary Analysis of Competition-Related Impacts of Nonindigenous Aquatic Plants in the Laurentian Great Lakes.

The Laurentian Great Lakes of North America are home to thousands of native fishes, invertebrates, plants, and other species that not only provide recreational and economic value to the region but also hold an important ecological value. However, there are also 55 nonindigenous species of aquatic plants that may be competing with native species and affecting this value. Here, we use a key regional database—the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS)—to describe the introduction of nonindigenous aquatic plants in the Great Lakes region and to examine patterns relating to their capacity to compete with native plants species. Specifically, we used an existing catalog of environmental impact assessments to qualitatively evaluate the potential for each nonindigenous plant species to outcompete native plant species for available resources. Despite an invasion record spanning nearly two centuries (1837–2020), a great deal remains unknown about the impact of competition by these species. Nonetheless, our synthesis of existing documentation reveals that many of these nonindigenous species have notable impacts on the native plant communities of the region in general and on species of concern in particular. Furthermore, we provide a thorough summary of the diverse adaptations that may contribute to giving these nonindigenous plants a competitive advantage. Adaptations that have been previously found to aid successful invasions were common in 98% of the nonindigenous aquatic plant species in the database.

Physical Control of Nonindigenous Aquatic Plants in Emerald Bay, Lake Tahoe, CA

Establishment of nonindigenous (NI) aquatic plants in the nearshore regions of freshwater ecosystems has resulted in environmental degradation, recreation concerns, economic impacts, and substantial management challenges. To reduce these undesirable effects, NI aquatic plants are often targeted for removal or control by management agencies, but the efficacy of implementation is often not documented or sustained. In this study, we developed a management plan to completely remove all NI plants from Emerald Bay, Lake Tahoe, CA, using only physical control techniques. Management plan priorities were based on previous research and lessons learned, including the need for (1) integrated weed management using multiple physical control techniques, (2) a large initial treatment investment, (3) ongoing early detection and rapid response, (4) detailed ecological monitoring, and (5) a long-term commitment to annual maintenance removal. Application of this management plan resulted in complete removal of all NI aquatic plants from Emerald Bay and substantial cost savings each year after the initial large investment. Annual maintenance removal and monitoring will need to continue as long as NI aquatic plants continue to enter Emerald Bay on boats and currents from other areas of Lake Tahoe.

The Effects of Ambient Water Quality and Eurasian Watermilfoil on Lakefront Property Values in the Coeur d’Alene Area of Northern Idaho, USA

Amenity value of water resources has become a major driving force of recent population growth in the region centered on Coeur d’Alene Lake in northern Idaho, USA. Despite regulatory measures aimed to protect lake water quality, surface water quality is increasingly threatened by lakefront development and invasions of Eurasian watermilfoil (Myriophyllum spicatum), a non-indigenous aquatic plant species. We used hedonic modeling to estimate the effects of ambient water quality and the presence of Eurasian watermilfoil on lakefront property values of single-family homes in the Coeur d´Alene area. We find that property values are positively associated with Secchi depth (a proxy of water quality or clarity), and negatively related to the presence of watermilfoil. Results of spatial regime analysis indicate the geographical variations of these associations. The presence of watermilfoil was related to a 13% decline in mean property value, corresponding to $64,255 USD, on average, lower property sales price. Our study demonstrates that proactive mitigation approaches to cope with potential environmental degradation in lake ecosystems could have significant economic benefits to owners of lakefront properties and local communities.

Comments on increasing number and abundance of non-indigenous aquatic macrophyte species in Germany

Hussner A, Van de Weyer K, Gross EM & Hilt S (2010). Comments on increasing number and abundance of non-indigenous aquatic macrophyte species in Germany. Weed Research 50, 519–526. Summary Non-indigenous aquatic plants are a major cause of biodiversity loss in many countries. In this study, our own field data and a literature review have been used to get an overview of the history and the present distribution of non-indigenous aquatic plant species in Germany. Results show that the number of non-indigenous aquatic plant species in Germany rose from 1 in 1860 to 12 in 1980, but doubled to 24 during the following 29 years. Thirteen of these species are naturalised in at least one federal state, 11 are only ephemeral. The number of non-indigenous aquatic plant species in the German federal states is significantly correlated with the population size and area. The increase in species number and abundance is probably caused by enhanced trading and increased invasibility of waters by eutrophication/re-oligotrophication and climate change. We propose a trading ban for some highly invasive non-indigenous aquatic species. This will not stop their natural spread, but should reduce the risk of further unintended entry and thus can be a major control factor.

Feeding rates of an introduced freshwater gastropod Pomacea insularum on native and nonindigenous aquatic plants in Florida

Pomacea insularum (Gastropoda: Ampullariidae) is a common, nonindigenous species in many parts of the world and an important consumer of aquatic macrophytes. We conducted laboratory trials to quantify the rates of consumption of native and nonindigenous aquatic plants in Florida, where this snail has been introduced. Twenty-two freshwater plant and alga species were presented to naïve P. insularum in laboratory trials, using single-snail replicates and simultaneous (no-snail) controls. Pomacea insularum damaged >50% of the replicate plants of 16 species; for 14 of these we calculated ash-free dry weight-specific feeding rates of P. insularum. The most heavily consumed plants were two native species: Limnobium spongia (0.744 g/g/d) and Chara sp. (0.478 g/g/d). Nonindigenous Panicum repens (0.306 g/g/d), Hydrilla verticillata (0.292 g/g/d) and Ceratophyllum demersum (0.254 g/g/d); and native Sagittaria latifolia (0.257 g/g/d), Najas guadalupensis (0.225 g/g/d) and Vallisneria americana (0.207 g/g/d) were also heavily consumed. Nonindigenous Eichhornia crassipes was consumed at a lower rate (0.053 g/g/d) while nonindigenous Colocasia esculenta and Pistia stratiotes were not consumed at detectable levels. Our results suggest that P. insularum cannot be relied upon as a biological control agent for nonindigenous plants and may heavily impact native macrophytes.

Is Hybridization Responsible for Invasive Growth of Non-indigenous Water-milfoils?

Heterosis, or hybrid vigor, has recently been proposed as a factor promoting invasive growth of some non-indigenous aquatic plant species, particularly those capable of spreading rapidly within and among lakes through clonal reproduction. We tested this hypothesis for variable-leaf water milfoil (Myriophyllum heterophyllum), a non-indigenous aquatic plant that has become a major management and conservation concern in New England. Using nuclear ribosomal DNA, we looked for F1 hybrid populations of invasive M. heterophyllum in 25 New Hampshire (NH) lakes. In contrast to a previous study that found F1 hybrid lineages of invasive M. heterophyllum in Connecticut, we did not find hybrids in our study lakes. This result has two implications: (1) pure lineages of M. heterophyllum are also capable of invasive growth, and (2) the distribution of invasive M. heterophyllum lineages (hybrid vs. pure) may be spatially structured across New England. We stress the importance of more detailed distributional and ecological studies for understanding the invasive potential of this species.

Integrating nonindigenous aquatic plant control with protection of snail kite nests in Florida.

The endangered snail kite (Rostrhamus sociabilis) feeds primarily on the freshwater apple snail (Pomacea paludosa) in Florida. The nonindigenous, floating water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) impede kites from finding snails. Effective control of these aquatic plants in the littoral zone of central and south Florida lakes benefits kites by maintaining open foraging habitat. However, incidental herbicide spraying of nesting substrates result in nest collapse when kites breed in nonwoody, emergent plants [cattail (Typha spp.) and giant bulrush (Scirpus validus)] in the outer littoral zone during lower lake levels. Many endangered species recovery plans and their implementation have experienced problems due to inaction and/or noncooperation by various governmental agencies and their personnel. Herein, we describe the development and implementation of a buffer zone strategy to prevent secondary impacts from an aquatic plant control program to snail kites nesting on lakes in central and south Florida. A strategy was jointly developed by personnel of five state and federal agencies to control herbicide application near kite nesting areas during the normal breeding season. Although requiring various modifications during its implementation, this cooperative effort successfully integrated aquatic plant control objectives with snail kite conservation on Lake Okeechobee during 1988. The program was expanded the following year to lakes Kissimmee and Tohopekaliga. Since the implementation of the snail kite impact preclusion program, no nest loss was attributed to incidental herbicide applications on lakes Okeechobee, Kissimmee, and Tohopekaliga.