An analysis of publications on invasive macrophytes in aquatic ecosystems

Abstract

A good understanding of the mechanisms and magnitude of the impact of invasive alien species on ecosystem services and biodiversity is a prerequisite for the efficient prioritisation of actions to prevent new invasions or for developing mitigation measures. In this review, we identified alien marine species that have a high impact on ecosystem services and biodiversity in European seas, classified the mechanisms of impact, commented on the methods applied for assessing the impact and the related inferential strength, and reported on gaps in available information. Furthermore, we have proposed an updated inventory of 87 marine species in Europe, representing 13 phyla, which have a documented high impact on ecosystem services or biodiversity.Food provision was the ecosystem service that was impacted by the greatest number of alien species (in terms of both positive and negative impacts). Following food provision, the ecosystem services that were negatively affected by the highest number of alien species were ocean nourishment, recreation and tourism, and lifecycle maintenance, while the ecosystem services that were most often positively impacted were cognitive benefits, water purification, and climate regulation. In many cases, marine aliens were found to impact keystone/protected species and habitats. Thirty percent of the assessed species had an impact on entire ecosystem processes or wider ecosystem functioning, more often in a negative fashion. Forty-nine of the assessed species were reported as being ecosystem engineers, which fundamentally modify, create, or define habitats by altering their physical or chemical properties.The positive impacts of alien species are probably underestimated, as there is often a perception bias against alien species. Among the species herein assessed as high-impact species, 17 had only negative and 7 only positive impacts; for the majority (63 species), both negative and positive impacts were reported; the overall balance was often unknown. Although there is no doubt that invasive species have modified marine ecosystems, evidence for most of the reported impacts is weak, as it is based on expert judgement or dubious correlations, while only 13% of the reported impacts were inferred via manipulative or natural experiments. A need for stronger inference is evident, to improve our knowledge base of marine biological invasions and better inform environmental managers.

Herbivore regulation of plant abundance in aquatic ecosystems

“…Furthermore, the effect of nativeness on change in plant abundance was reduced at higher herbivore densities, perhaps because at high herbivore densities the opportunities for selective feeding on preferred species will be diminished because of competition among individuals (Schoener, 1971). Recent decades have seen an increased spread of both invasive herbivores and macrophytes, which suggests that the magnitude of plant-herbivore interactions may be varying over time in many invaded aquatic ecosystems in response to changes in the nativeness of species assemblages (Jackson & Grey, 2013;Evangelista, Thomaz & Umetsu, 2014).…”

Germination and Seedling Growth of Water Primroses: A Cross Experiment between Two Invaded Ranges with Contrasting Climates

“…This suggests that there are fundamental differences in the colonization dynamics of aquatic ecosystems, and further demonstrates the vulnerability of these systems to invasion. The ability of exotic macrophytes to transform ecosystems ( Yarrow et al, 2009 ; Evangelista et al, 2014 ) raises concerns about the future of native species, as some regions support many rare or threatened macrophyte species ( Nicolet et al, 2004 ). Moreover, projected global climate changes are expected to magnify the negative impacts of invasive species with severe consequences for native species and ecosystems ( Mainka and Howard, 2010 ).…”

Does the alienLemna minutashow an invasive behavior outside its original range? Evidence of antagonism with the nativeL. minorin central Italy

“…Specifically, for inland waters, studies on biological invasions have focused almost exclusively on the weed species’ economic impact (e.g., Wilgen et al, ), whereas studies concerning impact on freshwater biodiversity have received little attention (e.g., Ricciardi and MacIsaac, ). With regard to plant invasions in aquatic ecosystems, only recently there has been an increase in the studies concerning invasive alien macrophytes (e.g., Brundu et al, ; Evangelista et al, ; Kovalenko and Dibble, ) and their impact on different biological communities (e.g., Janes et al, ; Schultz and Dibble, ; Kelly et al, ). Given the relevance of invasiveness of these macrophytes in aquatic ecosystems, it has now become important to widen the study effort regarding the invasion dynamics of these plants and their effect on the invaded ecosystems.…”