IN SHORT…
To date, photos of a green alga from Barbados uploaded to iNaturalist that appear to be Boergesenia forbesii have commonly been identified as Valonia utricularis (some gaining Research Grade status), or a species of Ulva or Caulerpa. A suggestion that a specimen I had identified as Valonia sp. was in fact a species of Boergesenia prompted my investigation of this topic.
The Conclusion: Overall, reports in the literature and iNaturalist records suggest that the earliest occurrence of Boergesenia forbesii in the Caribbean was in Puerto Rico (2008 reported collection date), and that it has spread southward reaching Barbados sometime between 2008 and 2016.
Of Indo-Pacific origin, Boergesenia forbesii is clearly a recent immigrant to Barbados.
Read more in iNaturalist Journal