Abstract
Understanding the full range of consequences of species introductions into island and marine habitats requires quantitative studies of systems that are currently under-represented in the scientific literature. We document the introduction, proliferation and establishment of a non-native sea anemone species in an isolated tropical marine lake, a marine ‘island’. From 2003–2012, we gathered samples to identify the introduced species and used transect and photo-quadrat surveys to describe its abundance, distribution, and any associations with native species or habitats. The non-native sea anemone was first found at the tourist entry into the lake in 2003 and identified as Exaiptasia pallida (Agassiz 1864), a species with zooxanthellae endosymbionts. Temporal patterns of tourism, the spatial extent of the sea anemone in 2003, and genetic analyses of the symbiont were consistent with the early stages of introduction. Subsequent expansion of E. pallida throughout the lake occurred within six years. The native species assemblages that were invaded by E. pallida were heterogeneous among surveys and habitats. Overall, there were few correlations that were significant between percent cover of E. pallida and native species; most significant associations were negative; the majority were on mangrove roots. There was one positive association between E. pallida and a native sponge. No significant relationship was found between the abundance of E. pallida and native species diversity. The rapid expansion of E. pallida but dearth of strong ecosystem effects presents a case study of invasive species in a tropical marine habitat where consequences are not directly proportional to invasive abundance. Whether this outcome is stable and representative of other species introduced into marine lakes, or elsewhere in marine systems, remains to be seen.
Highlights
Non–indigenous species (NIS) and their negative or positive associations with native species, ecosystem functions, and society have been much debated in descriptions of species invasions (Bax et al 2003, Davis 2003, Sax and Gaines 2003, Galil 2007, Molnar et al 2008)
In 2003, we discovered a non-native sea anemone introduced in Jellyfish Lake (Ongeim’l Tketau), a tropical marine lake in Palau (Figs. 1, 2)
Five anemone specimens were identified as Exaiptasia pallida (Agassiz in Verrill, 1864), formerly Aiptasia pulchella and Aiptasia pallida (Grajales and Rodriquez 2014)
Summary
Non–indigenous species (NIS) and their negative or positive associations with native species, ecosystem functions, and society have been much debated in descriptions of species invasions (Bax et al 2003, Davis 2003, Sax and Gaines 2003, Galil 2007, Molnar et al 2008). Situations in which invasions have been common include semi‐enclosed bays, estuaries, and seas (e.g., Hewitt et al 2004), but because such coastal locations have experienced heavy ship traffic, human development, and waves of introduced species over the last century (Galil 2007), the introductions themselves can be difficult to study.
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