The first record of a non-native seaweed from South Georgia and confirmation of its establishment in the Falkland Islands: Ulva fenestrata Postels & Ruprecht

Abstract

Detecting non-native species can be challenging, particularly in the case of taxa such as seaweeds, which can be difficult to distinguish based on morphology and often require molecular-assisted taxonomy for reliable identification. The sub-Antarctic island of South Georgia supports unique and important marine biodiversity, including a rich seaweed flora, but despite its isolation, its inshore ecosystems are susceptible to the introduction of potentially invasive non-native species. Here, we provide the first report of a non-native seaweed in South Georgia, Ulva fenestrata Postels & Ruprecht (Ulvophyceae, Chlorophyta), and confirm its widespread presence in the Falkland Islands via molecular-assisted taxonomy. Phylogenetic analyses of tufA and rbcL-3P genetic markers enabled the identification of a specimen collected from Grytviken, South Georgia in November 2021 as U. fenestrata. In terms of tufA sequence, this sample was identical to specimens collected from four sites spanning West and East Falkland in 2013 and 2018. This study represents the second Southern Hemisphere record of U. fenestrata, which is generally regarded as a Northern Hemisphere species. Our findings provide a foundation for monitoring this potentially invasive species in South Georgia, and for determining its likely source and mode of arrival, while emphasising the importance of robust biosecurity measures.

Identifying marine invasion threats and management priorities through introduction pathway analysis in a remote sub‐Antarctic ecosystem

“…It is important to note that none of these species have yet been recorded in SGSSI and so there is a large amount of uncertainty regarding their real‐world survival and reproduction potential, and pivotally, whether other species, not considered here, will arrive first (e.g. Mrowicki & Brodie, 2023 ).…”

“…This ecoregion has few historical recordings of non‐native species and these are almost entirely terrestrial non‐native species (Frenot et al., 2005 ). However, multiple non‐native marine algae and invertebrates have been observed within the nearby Antarctic Peninsula region (Cárdenas et al., 2020 ; McCarthy et al., 2019 ), and the first record of an established marine non‐native ( Ulva fenestrata ) within South Georgia waters was recently recorded (Mrowicki & Brodie, 2023 ). Despite low‐level passive dispersal of marine non‐native species (Avila et al., 2020 ; Brasier et al., 2021 ), increasingly frequent rafting on kelp or plastic transports species to the archipelago (Convey & Peck, 2019 ; Fraser et al., 2018 ; Griffiths & Waller, 2016 ).…”