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Surveys of Hawaiian macroalgae over the past 15 years have yielded numerous specimens representing species new to science. Calliblepharis yasutakei sp. nov. is here described based on a plant collected at a depth of 98 m from Kapou, Papahânaumokuâkea Marine National Monument, Hawaiʻi. Phylogenetic analyses of three molecular markers (COI, rbcL, and SSU) and analyses of morphological features were used to describe the new species in the family Cystocloniaceae. Calliblepharis yasutakei sp. nov. grouped with C. fimbriata, C. rammediorum, C. occidentalis and C. jolyi in a clade with full support for the rbcL analysis, representing a distinct lineage within the genus. Phylogenetic and vegetative morphological comparisons demonstrated that the new Hawaiian species is most closely related to C. rammediorum from Israel (rbcL similarity of 96.3%), although no female reproductive structures were found to allow a more comprehensive comparison. In order to determine whether C. yasutakei represents the first confirmed report of the genus Calliblepharis in the Hawaiian Islands, phylogenetic and morphological analysis of the Hawaiian Hypnea saidana (=Calliblepharis saidana) specimen accessioned at the Bernice P. Bishop Museum was performed. These analyses demonstrated that this specimen belongs to a new species in the genus Hypnea, which is here described as H. tsudae sp. nov. C. yasutakei, in addition to being a new species, is also reported as the first confirmed record of the genus Calliblepharis in the Hawaiian archipelago, and the description of H. tsudae brings the number of species for this genus in Hawaiʻi to eight. 

Over the last 2 decades, routine collections in the Hawaiian Archipelago have expanded to mesophotic reefs, leading to the discovery of a new red algal genus and species, here described asAnunuuluaehu liulagen. et sp. nov. This study provides a detailed genus and species description and characterizes chloroplast and mitochondrial organellar genomes. The new genus,Anunuuluaehu, shares many characteristics with the family Phyllophoraceae and shows close similarities toArchestennogrammaandStenogramma, including habit morphology, nemathecia forming proliferations at the outer cortex with terminal chains of tetrasporangia, and carposporophytes with multi‐layered pericarps. The single species in this genus exhibits distinctive features within the Phyllophoraceae: the presence of single‐layer construction of large medullary cells and the development of long, tubular gonimoblastic filaments. Multi‐gene phylogenetic analyses confirmed it as a unique, monophyletic lineage within the family. Cis‐splicing genes, interrupted by intron‐encoded proteins within group II introns, are present in both the chloroplast and mitochondrial genomes ofA. liula. Notably, a specific region of thecoxI group II intron exhibits similarity to fungal introns.Anunuuluaehu liulais presumed to be endemic to the Hawaiian Archipelago and thus far is known to live solely at mesophotic depths from Hōlanikū to Kaho‘olawe ranging from 54 to 201 m, which is the deepest collection record of any representative in the family. Overall, this study enhances our understanding of the genomic and taxonomic complexities of red algae in mesophotic habitats, emphasizing the significance of continued research in this area to uncover further insights into evolutionary processes and biogeographic patterns.

 

Two genera of the Rhodymeniales, Halopeltis and Leptofauchea, are here reported for the first time from the Hawaiian Islands and represent the deepest records for both genera. Molecular phylogenetic analyses of cytochrome oxidase subunit I (COI), rbcL, and large subunit ribosomal DNA (LSU) sequences for Hawaiian specimens of Leptofauchea revealed one well-supported clade of Hawaiian specimens and three additional lineages. One of these clades is described here as Leptofauchea huawelau sp. nov., and is thus far known only from mesophotic depths at Penguin Bank in the Main Hawaiian Islands. L. huawelau sp. nov. is up to 21 cm, and is the largest known species. An additional lineage identified in the LSU and rbcL analyses corresponds to the recently described L. lucida from Western Australia, and is a new record for Hawai‘i. Hawaiian Halopeltis formed a well-supported clade along with H. adnata from Korea, the recently described H. tanakae from mesophotic depths in Japan, and H. willisii from North Carolina, and is here described as Halopeltis nuahilihilia sp. nov. H. nuahilihilia sp. nov. has a distinctive morphology of narrow vegetative axes that harbor constrictions along their length. The current distribution of H. nuahilihilia includes mesophotic depths around W. Maui, W. Moloka‘i, and the island of Hawai‘i in the Main Hawaiian Islands. Few reproductive characters were observed because of the small number of specimens available; however, both species are distinct based on phylogeny and morphology. These descriptions further emphasize the Hawaiian mesophotic zone as a location harboring many undescribed species of marine macroalgae. 

Satellite imagery is a useful tool for monitoring and mapping the distribution of invasive or nuisance algal species on coral reefs over the temporal and spatial scales needed for ecosystem management. Visual inspections of high-resolution satellite imagery were used to detect the newly discovered nuisance alga,Chondria tumulosa, at Manawai (Pearl and Hermes Atoll) in combination with ground-truthing surveys. Low-albedo (“dark”) survey sites on spur habitats were associated with meanC. tumulosacover seven times higher than adjacent high-albedo (“light”) sites. There was an inverse relationship betweenC. tumulosapercent cover at ground-truthing sites and mean reflectance values. Archival satellite imagery showed that areas of highC. tumulosacover (i.e., dark patches) were not evident on or before 2015 on the northeast backreef. The ability to use satellites for the detection of nuisance or invasive benthic species, such as expansive mats ofC. tumulosa, provides managers with a valuable tool, especially in remote regions.

 

Small red algal morphologically variable blades have been extensively collected from Hawaiian reefs, but for many specimens their taxonomy remains poorly understood. In surveys of the Papahānaumokuākea Marine National Monument (PMNM) and Main Hawaiian Islands (MHI), we discovered two taxa of undescribed small (< 5 cm) red blades that matched the genera Psaromenia and Meredithia, based on morphology and molecular analyses. Neither genus has been previously recorded in the Hawaiian Islands, and neither group of specimens matched currently described species in these two genera. Accordingly, these specimens are described here as new species within the family Kallymeniaceae. Psaromenia laulamaula sp. nov., exclusively found at mesophotic depths (83–94 m) in PMNM, is easily distinguished from other members of the genus by its comparatively large, procarpic carpogonial branch system and solitary obovate pink-tomagenta blades. Conversely, Meredithia hawaiiensis sp. nov., occurring in both shallow (0–17 m) and mesophotic depths (55 m), has high morphological plasticity, with characters that overlap with other Meredithia species, and can only be distinguished based on DNA sequences. This study provides additional evidence of the extent of diversity in the Kallymeniaceae that is poorly characterized from mesophotic depths and provides further evidence that members of the macroalgal flora contain overlooked biodiversity.