Expansion of an introduced sea anemone population, and its associations with native species in a tropical marine lake (Jellyfish Lake, Palau)

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.

Mediators of invasions in the sea: life history strategies and dispersal vectors facilitating global sea anemone introductions

“…The speed with which it covers substrate is a point of concern for aquarists, who note that it grows over corals and other ornamentals and can clog aquarium filters (Ram 2013 ). Exaiptasia pallida may play a similar fouling role in native environments, as it is often found on shells, coral skeletons, and the roots of mangroves, and this proliferative power makes its appearance of concern in sensitive environments such as isolated marine lakes (Hanzawa et al 2012 ; Patris et al 2019 ), in Madeira (Canning-Clode et al 2013 ; Wirtz 2014 ) and in the Galapagos Islands (Carlton et al 2019 ), although the quantified effects of E. pallida in these systems so far has either not been studied or is minimal (Patris et al 2019 ). Experimental competitive interactions between E. pallida and native European species indicate that it is competitively matched by ecologically similar native species and thus unlikely to become dominant (Escribano-Álvarez and López-González 2018 ).…”

Invasive Japanese foraminifera in a south-west Australian estuary

“…Various invasive species in shallow marine environments have been documented in 'plague' proportions due to rapid increases in populations in their new environments (e.g. sea anemones, gastropods, crustaceans, fish, seagrasses and algae; Ceccherelli et al 2000;Smith et al 2002;Hunt and Behrens Yamada 2003;Lanfranconi et al 2009;Edelist et al 2013;Patris et al 2019). In Western Australian estuaries and shallow lagoons, invasive species from diverse taxonomic groups have been recorded (e.g.…”