Community effects of invasive macrophyte control: role of invasive plant abundance and habitat complexity

Abstract

Summary1. The control of invasive species has become a widespread management practice, yet information on the community effects of such efforts is very limited, there is no unified framework for monitoring their success and no guidelines exist to help minimize potential adverse impacts. 2. This study was conducted to determine how long-term efforts to control a widespread invasive macrophyte, Eurasian watermilfoil, affect native macrophytes, fish and macroinvertebrates. In addition, we examined how members of the aquatic fauna respond to changes in invasive macrophyte abundance and habitat complexity to understand the mechanisms underlying any potential community response. 3. Selective control of the invasive macrophyte had minor effects on habitat complexity due to timely recolonization by native macrophytes and it did not affect littoral fish richness and abundance. Macroinvertebrate communities were highly variable and some of that variation could be attributed to characteristics of the macrophyte community. Fish and macroinvertebrates were more affected by habitat complexity than by other attributes of the macrophyte assemblage. 4. Synthesis and applications. Management plans to control invasive species need to prioritize selective removal and timely restoration of the native assemblage. In this study, the invasive macrophyte was used by aquatic fauna, which emphasizes the need for immediate restoration of the native macrophyte community to mitigate for the lost habitat after invasive plant control efforts. As both fish and macroinvertebrates were more affected by complexity than other attributes of the macrophyte assemblage, re-establishment of habitat complexity appears to be a promising restoration strategy. On a more general note, we highlight the importance of assessing community response to the habitat provided by the invader and invader's function in the community when evaluating strategies to control invasive species.

Macroinvertebrate communities associated with macrophyte habitats in a tropical man-made lake (Lake Taabo, Côte d’Ivoire)

“…Besides, according to Thomaz et al (2008), macrophyte identity plays a smaller role than macrophyte surface area or fractal complexity in explaining macroinvertebrate diversity and abundance. Also, Kovalenko et al (2010) showed that the abundance of certain macrophytes could explain a small proportion of variability in macroinvertebrate communities, but the effect of this driver was not consistent among lakes or among the seasons. It may be supposed that Eichhornia crassipes is a permanent addition to Lake Taabo's macrophytes and in terms of aquatic macroinvertebrate communities it serves a similar function to the littoral plants.…”

“…It tends to invade water bodies where hydrological or nutrient conditions have been altered by human activities (Barret, 1989). Surprisingly few studies have reported the influence of macrophytes on diversity of invertebrates in freshwater ecosystems (e.g., Brendonck et al, 2003;Toft et al, 2003;Albertoni et al, 2007;Thomaz et al, 2008;Kovalenko et al, 2010). In addition to the prevailing environmental conditions, there are many other factors that may affect epiphytic and plant-associated invertebrate distribution.…”

Effects of invasive macrophyte on trophic diversity and position of secondary consumers

“…No invasive plants were present in our study sites in the treated lakes. Herbicide application at label rates should not directly affect fish or invertebrates (Washington State Department of Ecology, 2001a, b), and a previous study did not detect treatment-related changes in fauna, possibly due to selectivity of the treatment and timely restoration of native macrophytes (Kovalenko et al, 2010). Study lakes were similar in nutrient status (moderately eutrophic, Minnesota Department of Natural Resources, unpublished data) and fish community structure.…”

“…Study lakes were similar in nutrient status (moderately eutrophic, Minnesota Department of Natural Resources, unpublished data) and fish community structure. A previous study showed that overall fish community in these lakes was dominated by invertivorous bluegill (Lepomis macrochirus, 74% of all fish collected in the littoral zone), whereas largemouth bass (Micropterus salmoides) was the most common piscivore (approximately 80% of all predatory fish abundance, Kovalenko et al, 2010).…”

Macroinvertebrate communities associated with littoral zone habitats and the influence of environmental factors in Malilangwe Reservoir, Zimbabwe

“…However, our findings are similar to findings by Mwabvu and Sasa (2009) who observed the same situation in Fletcher Reservoir. Kovalenko et al (2010) showed that the abundance of certain macrophytes could explain a small proportion of variability in macroinvertebrate communities. This was consistent with our study Reservoir, as a decline in macrophyte cover and abundance due to drawdown resulted in changes in macroinvertebrate communities, abundance and distribution.…”