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In this review, we describe the history, pathways and vectors of the biological invasion of the azooxanthellate coral Tubastraea (Scleractinia: Dendrophylliidae) throughout the world. In order to do so we consulted previous reports in the literature and also compiled new unpublished information on the distribution of the three species of Tubastraea which have been reported as non indigenous species, both within their native and non-native ranges and also on vectors, and where cryptogenic. We combine these data with historical aspects of marine vectors in order to get insights into how Tubastraea species have successfully spread around the world, established and invaded and where future studies would be best focused. T. coccinea and T. tagusensis are recognized as being highly invasive and are causing significant environmental, economic, and social impacts requiring management actions. The third species, T. micranthus so far only reported outside its native range on oil platforms, may have similar potential for negative impact. The vectors of introduction of Tubastraea may have changed throughout history and the biological invasion of these invasive corals may reflect changing practices, demands and legislation in shipping activities over the years. Today it is clear that these corals are fouling organisms strongly associated with oil and gas platforms worldwide which are thus primary vectors for new introductions.

The deep reef refuge hypothesis (DRRH) postulates that mesophotic coral ecosystems (MCEs) may provide a refuge for shallow coral reefs (SCRs). Understanding this process is an important conservation tool given increasing threats to coral reefs. To establish a better framework to analyze the DRRH, we analyzed stony coral communities in American Sāmoa across MCEs and SCRs to describe the community similarity and species overlap to test the foundational assumption of the DRRH. We suggest a different approach to determine species as depth specialists or generalists that changes the conceptual role of MCEs and emphasizes their importance in conservation planning regardless of their role as a refuge or not. This further encourages a reconsideration of a broader framework for the DRRH. We found 12 species of corals exclusively on MCEs and 183 exclusively on SCRs with another 63 species overlapping between depth zones. Of these, 19 appear to have the greatest potential to serve as reseeding species. Two additional species are listed under the U.S. Endangered Species Act, Acropora speciosa and Fimbriaphyllia paradivisa categorized as an occasional deep specialist and a deep exclusive species, respectively. Based on the community distinctiveness and minimal species overlap of SCR and MCE communities, we propose a broader framework by evaluating species overlap across coral reef habitats. This provides an opportunity to consider the opposite of the DRRH where SCRs support MCEs.

An annotated checklist of the stony corals (Scleractinia, Milleporidae, Stylasteridae, and Helioporidae) of American Sāmoa is presented. A total of 377 valid species has been reported from American Sāmoa with 342 species considered either present (251) or possibly present (91). Of these 342 species, 66 have a recorded geographical range extension and 90 have been reported from mesophotic depths (30–150 m). Additionally, four new species records ( Acanthastreasubechinata Veron, 2000, Favitesparaflexuosus Veron, 2000, Echinophylliaechinoporoides Veron & Pichon, 1980, Turbinariairregularis Bernard, 1896) are presented. Coral species of concern include species listed under the US Endangered Species Act (ESA) and the International Union for Conservation of Nature’s (IUCN) Red List of threatened species. Approximately 17.5% of the species present or possibly present are categorized as threatened by IUCN compared to 27% of the species globally. American Sāmoa has seven ESA-listed or ESA candidate species, including Acroporaglobiceps (Dana, 1846), Acroporajacquelineae Wallace, 1994, Acroporaretusa (Dana, 1846), Acroporaspeciosa (Quelch, 1886), Fimbriaphylliaparadivisa (Veron, 1990), Isoporacrateriformis (Gardiner, 1898), and Pocilloporameandrina Dana, 1846. There are two additional species possibly present, i.e., Pavonadiffluens (Lamarck, 1816) and Poritesnapopora Veron, 2000.

In 1917, Alfred Mayor surveyed a 270 m transect on a reef flat on American Samoa. Eleven surveys were conducted on the transect from 1917 to 2019. The coral community on the reef crest was resilient over the century, occasionally being seriously damaged but always recovering rapidly. In contrast, the originally most dense coral community on the reef flat has been steadily deteriorating throughout the century. Resilience of coral communities in regions of high wave energy on the reef crests was associated with the important binding function of the crustose coralline alga (CCA) Porolithon onkodes. Successful coral recruits were found on CCA 94% of the time, yet living coral cover correlated negatively with CCA cover as they became alternative winners in competition. Mayor drilled a core from the transect on the surface to the basalt base of the reef 48 m below. Communities on Aua reef were dominated by scleractinians through the Holo cene, while cores on another transect 2 km away showed the reef was occupied by alcyonaceans of the genus Sinularia, which built the massive reef with spiculite to the basalt base 37 m below. Despite periods of sea levels rising 9 to 15 times the rate of reef accretion, the reefs never drowned. The consistency of scleractinians on Aua reef and Sinularia on Utulei Reef 2 km away during the Holocene was because the shape of the bay allowed more water motion on Aua reef. After 10 700 yr of reef building by octocorals, coastal construction terminated this spiculite-reef development.

The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures.

Tropical marine ecosystems are biologically diverse and economically invaluable. However, they are severely threatened from impacts associated with climate change coupled with localized and regional stressors, such as pollution and overfishing. Non-native species (sometimes referred to as ‘alien’ species) are another major threat facing these ecosystems, although rarely discussed and overshadowed by the other stressors mentioned above. NNS can be introduced accidentally (for example via shipping activities) and/or sometimes intentionally (for aquaculture or by hobbyists). Understanding the extent of the impacts NNS have on native flora and fauna often remains challenging, along with ascertaining when the species in question actually became ‘invasive’. Here we review the status of this threat across key tropical marine ecosystems such as coral reefs, algae meadows, mangroves, and seagrass beds. We aim to provide a baseline of where invasive NNS can be found, when they are thought to have been introduced and what impact they are thought to be having on the native ecosystems they now inhabit. In the appended material we provide a comprehensive list of NNS covering key groups such as macroalgae, sponges, seagrasses and mangroves, anthozoans, bryozoans, ascidians, fishes, and crustaceans.

A recent study reported that seventy-five species of reef-building corals, considered to be at elevated extinction risk when assessed by the criteria of the International Union for Conservation of Nature, occur in Pacific waters under United States jurisdiction. Closer examination substantiates records of occurrence for 66 species, while records for the other 9 species were based on misinterpretations or are otherwise uncertain. Of these, at least 55 have been reported from reef habitat under federal protection within National Parks, Marine National Monuments, National Marine Sanctuaries, and National Wildlife Refuges. The highest number of species (31) is found within the Ofu Island unit of the National Park of American Samoa, followed by Kingman Reef (24) and Palmyra Atoll (21), both within the Pacific Remote Islands Marine National Monument. Federally protected areas already in place serve as important habitats for resources whose stewardship needs and priorities may vary over time.

The recent review by Veron et al. (2025) posits that quantitative genomic evidence used to understand coral evolution should be secondary to species hypotheses derived from expert opinion based on field experience. The authors argue that morphological “biological entities” should take precedence over molecular evidence when conflicts arise. This perspective required the rejection of extensive, independent molecular datasets that have progressively converged on a robust evolutionary framework for reef corals. Here, we reaffirm how prioritising subjective visual assessments over quantitative genetic and genomic data is methodologically unsound and scientifically regressive. We reject the framing of this perspective as “morphology versus molecules”. Rather, it is a fundamental divergence between two opposing philosophies: a static system anchored in non-reproducible expert judgement, and an integrative framework where genetic data provide the necessary independent test of morphological hypotheses. We show how a reliance on “field entities” obscures true morphological patterns by failing to distinguish between phenotypic plasticity, convergence, and evolutionary divergence. Effective taxonomy requires species hypotheses to be testable, and to stand or fall on the strength of reproducible evidence. Such a framework does not replace morphology; it validates it by providing an explicit, testable basis for evaluating morphological hypotheses. The integration of testable, reproducible molecular analysis with other lines of evidence including morphology is the benchmark of modern taxonomy across all Kingdoms of Life. We address the logical inconsistencies in the general arguments put forward by Veron et al. (2025) and refute their specific rejection of recent Acropora species-level revision with reproducible data.