Anthony David Montgomery

Coral reefs are diverse marine ecosystems that provide ecological functions and economic and social benefits across over 100 tropical countries. Warming driven by climate change is a primary threat to coral reefs and is increasing the frequency of global coral bleaching events. Here we reassessed the IUCN Red List status of 892 reef-building coral species, first assessed in 2008 ¹. Because species-level population trends are unavailable for most reef-building corals, population reductions were inferred using proxies based on global coral cover trends and projected annual severe bleaching under SSP2-4.5, both over three decades, adjusted using trait-based estimates of species vulnerability. Of the 774 species with sufficient data to be assessed, 340 (44%) were classified as threatened under IUCN Red List criteria. Thirty-three species were assessed as Critically Endangered, 251 as Endangered, and 56 as Vulnerable, most due to risk of population reduction associated with projected thermal stress. These findings predate the three hottest years on record and the fourth global coral bleaching event (2023-2025), and the first exceedance for an annual mean of the 1.5^oC global warming threshold. The findings reinforce the importance of limiting further warming to maintain coral biodiversity and reef ecosystem function. The Red List assesses the relative extinction risk of species, whereby species are placed in categories of increasing risk by comparing their population size, decline and geographic range against standardised thresholds. The Red List does not predict whether or when a species may go extinct. As the ranges of coral species remain under-surveyed, future assessments would be strengthened by species-level population data and thermal-stress and recovery metrics that better capture range-representative dynamics.

Most inferences about black coral (Antipatharia) phylogenetics have relied on a handful of molecular markers from PCR-Sanger methods but recently complete mitogenomes are shedding additional light on relationships. We present the most complete survey of shallow-water to mesophotic Hawaiian black corals (‘ēkaha kū moana) to date based on complete mitogenome sequences. The phylogenetic relationships inferred from whole-mitochondrial phylogenies recover Myriopathidae as monophyletic with Myriopathes and Tanacetipathes as the outgroups to all other Hawaiian black coral taxa. Combining our data with other published mitochondrial datasets for black corals, we find that morphologically similar Cirrhipathes cf. anguina specimens are divergent and may not be conspecifics. Likewise, the genera Antipathes and Stichopathes (family Antipathidae) include species that are more divergent from one another than they are to other genera in family Aphanipathidae. Overall, data show Myriopathidae is a monophyletic family, but the families Aphanipathidae and Antipathidae are polyphyletic, and the genera Antipathes and Stichopathes live up to their reputation as a “taxonomic dumping ground”. These phylogenetic analyses underscore the need for continued research to understand the evolutionary history and phylogenetic relationships for black corals generally and ‘ēkaha kū moana specifically.

This study reports the first mitogenome from the antipatharian (black coral) genus Cirrhipathes (GenBank accession number ON653414). The 20,452 bp mitochondrial genome of Cirrhipathes cf. anguina LS-2022 consists of 13 protein-coding genes, two rRNA genes, and two tRNA genes (trnM and trnW). The mitogenome is typical of other antipatharian families, including an A + T biased (64.1%) base composition and cytochrome c oxidase subunit I (COX1) intron with embedded homing endonuclease gene (HEG). A phylogenetic tree based on complete mitogenome sequences of currently available antipatharians indicates Cirrhipathes cf. anguina LS-2022 is sister and closely related to Stichopathes sp. SCBUCN-8849. However, it seems unlikely that intergeneric taxa share 99.97% similarity across their complete mitogenomes, raising questions about the current taxonomy of this group. This study highlights the need for additional vouchered antipatharian species to be sequenced so phylogenetic relationships can be compared with accepted taxonomy.

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.

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.