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Neighbor-joining phylogram (K2P distances) of COI sequences of Chondria. The phylogram analysis demonstrates the sequence divergence of C. tumulosa sp. nov. samples from other represented members of the genus, and illustrates that the newly analyzed specimens from Pearl and Hermes Atoll do not match previously characterized specimens in the genus. Additional Hawaiian specimens are shown in bold. Scale bar = substitutions per site. https://doi.org/10.1371/journal.pone.0234358.g001
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Survey cruises by the National Oceanic and Atmospheric Administration (NOAA) in 2016 and 2019 yielded specimens of an undetermined red alga that rapidly attained alarming levels of benthic coverage at Pearl and Hermes Atoll, Papahānaumokuākea Marine National Monument, Hawaiʻi. By 2019 the seaweed had covered large expanses on the northeast side of...
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... the BLAST algorithm on GenBank and BOLD, this sequence was identified as likely belonging to the genus Chondria, although a species-level match was not found. The NJ analysis demonstrated that the Chondria sequence was unique from all other available sequences for the genus, including those for other Hawaiian species of Chondria (Fig 1). ...
Citations
... In 2019, a previously undescribed red alga (Chondria tumulosa) was found overgrowing large areas of the reef (including live corals, Fig. 1) at Manawai (Pearl and Hermes Atoll) in the Papahānaumokuākea Marine National Monument (Sherwood et al. 2020). Chondria tumulosa forms large mounds or mats up to 20 cm in height that are loosely attached to hard substrate and composed of densely packed, tangled thalli (Sherwood et al. 2020). ...
... In 2019, a previously undescribed red alga (Chondria tumulosa) was found overgrowing large areas of the reef (including live corals, Fig. 1) at Manawai (Pearl and Hermes Atoll) in the Papahānaumokuākea Marine National Monument (Sherwood et al. 2020). Chondria tumulosa forms large mounds or mats up to 20 cm in height that are loosely attached to hard substrate and composed of densely packed, tangled thalli (Sherwood et al. 2020). Currently, this alga is described as cryptogenic because its origin is unresolved. ...
... This suggests the transition to a C. tumulosa-dominated benthic habitat in the northeast backreef AOI occurred sometime after 2015. This chronology of C. tumulosa spread at Manawai supports the timeline documented in benthic survey data collected over the past 20 years (Sherwood et al. 2020). ...
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 mean C. tumulosa cover seven times higher than adjacent high-albedo (“light”) sites. There was an inverse relationship between C. tumulosa percent cover at ground-truthing sites and mean reflectance values. Archival satellite imagery showed that areas of high C. tumulosa cover (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 of C. tumulosa, provides managers with a valuable tool, especially in remote regions.
... A plausible explanation is that S. arecina could be a human-mediated old introduction in southern Europe. Numerous cryptic or cryptogenic species have been reported in the Ceramiales (Williams and Smith 2007, Thomsen et al. 2016, D ıaz-Tapia et al. 2017a, Sherwood et al. 2020, Piñeiro-Corbeira et al. 2020a, highlighting the need to improve molecular datasets in this diverse red algal order for which only a small proportion of the diversity has been molecularly characterized. However, the introduction hypothesis cannot be confirmed for S. arecina, as its potential distribution beyond southern Europe is at present unsupported by the available molecular information. ...
Molecular analyses, in combination with morphological studies, provide invaluable tools for delineating red algal taxa. However, molecular datasets are incomplete and taxonomic revisions are often required once additional species or populations are sequenced. The small red alga Conferva parasitica was described from the British Isles in 1762 and then reported from other parts of Europe. Conferva parasitica was traditionally included in the genus Pterosiphonia (type species P. cloiophylla in Schmitz and Falkenberg 1897), based on its morphological characters, and later transferred to Symphyocladia and finally to Symphyocladiella using molecular data from an Iberian specimen. However, although morphological differences have been observed between specimens of Symphyocladiella parasitica from northern and southern Europe they have yet to be investigated in a phylogenetic context. In this study, we collected specimens from both regions, studied their morphology and analyzed rbcL and cox1 DNA sequences. We determined the phylogenetic position of a British specimen using a phylogenomic approach based on mitochondrial and plastid genomes. Northern and southern European populations attributed to S. parasitica represent different species. Symphyocladiella arecina sp. nov. is proposed for specimens from southern Europe, but British specimens were resolved as a distant sister lineage to the morphologically distinctive Amplisiphonia, so we propose the new genus Deltalsia for this species. Our study highlights the relevance of using materials collected close to the type localities for taxonomic reassessments, and showcases the utility of genome‐based phylogenies for resolving classification issues in the red algae.
... As climate change continues to affect coral reefs, reef communities may respond and shift-additional macroalgal species, which are rare or cryptic and were previously overlooked, may become more abundant. For example, the fleshy red alga, Chondria tumulosa may have been a sparse and cryptic species at Pearl and Hermes Atoll in the Northwestern Hawaiian Islands that increased in abundance and spread rapidly after changes in ecosystem conditions (Sherwood et al., 2020a). Changes in nutrient concentrations (Stimson, 2015), water temperature (Boudouresque and Verlaque, 2010;Dijkstra et al., 2019), and greenhouse gas concentrations (Fernańdez de la Hoz et al., 2019) have been linked to coral-macroalgal phase shifts on reefs, range shifts in macroalgal distribution, and changes in macroalgal abundances. ...
The recently described crustose calcifying red algal species Ramicrusta hawaiiensis, known only from mesophotic depths off Lehua Island, west of Kaua’i Island, was found in shallow benthic reef habitats (3-18 m deep) along the western coast of Hawai’i Island. Molecular and microscopy techniques were used for genetic confirmation and for detailed morphological and anatomical examination. Two independent benthic cover survey datasets collected from west Hawai’i Island were used to investigate temporal and geographic distribution of Ramicrusta. In both datasets, we report Ramicrusta at approximately 60% of the sites surveyed. Benthic cover for this alga varies among sites and among years and its presence in west Hawai’i is evident since at least 2003. These findings help to document Hawaiian coral reef ecosystem change and benthic community composition reshuffling. This study also emphasizes the critical importance of taxonomy and proper identification of macroalgal species to understand the potential for phase-shifts of dominant taxa in coral reef ecosystems after environmental disturbances and fluctuations in abiotic factors. In the last decade, members of the red algal order Peyssonneliales have increased in abundance and overgrown other benthic species in reef ecosystems in the Caribbean and tropical Pacific. The novel aspect of finding abundant Ramicrusta in much shallower water than originally described, the decadal presence of Ramicrusta, and its potential for competition with other benthic organisms make this research valuable to coral reef ecology and justify further investigation of Ramicrusta ecology and biology in the Hawaiian Islands and globally.
... With the exception of the recent discovery of the cryptogenic, invasive-like alga Chondria tumulosa (Sherwood et al. 2020), the Northwestern Hawaiian Islands do not contain invasive macroalgae. In comparison, the Main Hawaiian Islands contain several species of invasive Chlorophyta and Rhodophyta (Smith et al. 2002;Foster et al. 2019). ...
... Because of this, we examined site-specific differences at the level of island/atoll. Manawai was the most extensively surveyed atoll in August 2019 due to the discovery of the cryptogenic red alga C. tumulosa that displayed invasive traits across the reefs (Sherwood et al. 2020). Understanding whether algal tissue nitrogen concentrations differ at various sites at Manawai could provide insight into processes that may increase the growth or occurrence of this cryptogenic alga. ...
The Hawaiian Archipelago stretches 2500 km from the Main to the Northwestern Hawaiian Islands, represents a complex gradient of oceanographic and anthropogenic drivers, and has a high abundance and diversity of native and invasive macroalgae. These photosynthetic organisms occur in intertidal to mesophotic (30–150+ m) depths and absorb nitrogen with limited fractionation associated with their physiology and source. Our goal was to examine nitrogen dynamics from shallow to mesophotic reefs using compositional patterns of two well‐characterized macroalgal tissue parameters: stable isotope ratio of nitrogen and tissue nitrogen content. We collected 813 macroalgal samples from 13 islands/atolls between 0 and 117 m depths. Within the Main Hawaiian Islands, macroalgal tissue stable N isotope ratios were higher in mesophotic depths; N content was higher in shallow depths. However, within the Northwestern Hawaiian Islands, no differences in stable N isotope ratios and N content were found between shallow and mesophotic depths. Regionally, stable N isotope ratios varied along a gradient of anthropogenic and oceanographic processes (in Main and Northwestern Hawaiian Islands, respectively), while N content reflected elevated nitrogen in the Main compared with the Northwestern Hawaiian Islands. Additionally, the invasive macroalga Avrainvillea lacerata had significantly higher N content than co‐occurring native bryopsidalean macroalgae at similar depths, and may be reshaping nutrient dynamics from shallow to mesophotic depths in the Main Hawaiian Islands. Nitrogen dynamics at mesophotic depths may be influenced by nearshore anthropogenically derived nitrogen via submarine groundwater discharge and/or inputs from deeper water within the Main Hawaiian Islands.
... The phylogenomic tree was constructed using previously published complete plastid genome sequences from 31 red algal species within the order Ceramiales and showed C. tumulosa positioned as sister to three representatives of Chondria identified only to the genus level, forming a sister clade to the Laurencieae tribe, with full support (Figure 1). The previous phylogenetic analysis based on the rbcL and SSU genes (plastid and nuclear) showed C. tumulosa as distinct from the other species of the genus (Sherwood et al. 2020). In the present study, phylogenomic analysis based on the complete chloroplast genome sequence reaffirms the position of C. tumulosa as a new species within the Chondrieae tribe of the red algal family Rhodomelaceae. ...
The complete chloroplast genome of Chondria tumulosa, a red alga from Manawai (Pearl and Hermes Atoll), Hawai‘i, was determined and analyzed using next-generation sequencing and de novo assembly approaches. The chloroplast genome sequence of C. tumulosa was 172,617 bp and contained 231 genes, consisting of 197 protein-coding genes, 29 transfer RNA genes, three ribosomal RNA genes, one transfer-messenger RNA gene, one non-coding RNA gene, and one intron inserted into the trnM gene. The number of genes and genome structure was largely similar to other members of the family Rhodomelaceae. The phylogenomic analysis of 32 complete cpDNA from the red algal order Ceramiales showed that C. tumulosa is a distinct species within the Chondrieae tribe, and is a diverging early relative to the other three available Chondria chloroplast genomes.
... baileyana, C. dangeardii, C. repens, C. simpliciuscula, C. ryukyuensis) (Titlyanov et al., 2015a), the potential in this rather cryptic growing group is high. Nevertheless, despite the observed patchiness in our study, care has to be taken as members of this genus, like C. tumulosa were recently reported to start overgrowing Hawaiian coral reefs (Sherwood et al., 2020). ...
Tropical coastal ecosystems provide a unique complex marine habitat with a high diversity of algal species, Vietnam being a particular hotspot. These algae may host a variety of potential unknown or underestimated bioactive algal compounds. In parallel the worldwide rising interest in macroalgae-based products lead to increasing activities in seaweed natural harvest and mariculture within coastal waters With this growing interest, the present work provides baseline data for a systematic and science-based macroalgal monitoring program in Nha Trang Bay, Vietnam, to keep track of potentially interesting taxa and to identify driving environmental factors which may also naturally influence biodiversity and species abundance. The present study investigated macrophyte diversity and abundance by combining a qualitative and quantitative macroalgal survey approach with environmental sampling (e.g. physicochemical properties of water column, underwater light regime, and sediment characteristics). Surveys were performed in the dry season (May/June) 2019 in different water depths (3, 6 and 10 m) at seven sites within Nha Trang Bay. The study revealed a coastal patchwork of diverse habitats inhabited by complex macrophyte communities, including estuarine dense Sargassum forests and Turbinaria meadows, sheltered sandy seagrass (Halodule spp.) beds with upcoming Lyngbya blooms, low diverse Padina deserts and highly turbid aquaculture (lobster and fish farms) impacted sites with surprisingly high macroalgal diversity. During our study a total of 86 macrophyte species were encountered in the subtidal (>1 m water depth), whereas only 6 species (Padina australis, Sargassum mcclurei, Turbinaria ornata, Halimeda discoidea, Amphiroa fragilissima, Tricleocarpa cylindrical) were frequently found at every survey site. The observed high patchiness and presence of economically important (e.g. Sargassum spp., Gracilaria spp., Caulerpa spp., Gelidiella acerosa, Acanthophora spicifera) and potentially economically interesting (e.g. Padina australis, Turbinaria ornata, Stypopodium zonale, Chondria armata) taxa during the survey underlines the high potential of the present macrophytic bio-resource, which apparently is strongly structured and will be altered by the changing heterogenic environment.
This updated list is composed of a total of 661 records, which includes 71 brown algae, 450 red algae, 137 green algae, and three seagrasses, with an overall rate of endemism of 13.2%. Almost half (46.7%) of the Hawaiian records presented here are represented by at least one DNA sequence, while 16.3% are confirmed through a DNA sequence match to a topotype, and 6.7% are confirmed through a DNA sequence match to a type specimen. The data are presented in the context of the natural history of the Hawaiian Islands, which is heavily influenced by the volcanic hotspot origin of the archipelago in the middle of the Pacific Ocean, as well as the important cultural role of seaweeds and other marine plants in Hawai‘i, and the current threats to marine ecosystems, which include the introduction and proliferation of a number of invasive marine macroalgae.
