Introduction
Crustose coralline algae (CCA), calcifying multicellular red seaweeds, play critical ecological roles in marine environments, such as being one of the builders of coral reefs and providing habitat and settlement cues for larval and juvenile stages of invertebrates (Cornwall et al. Reference Cornwall, Diaz-Pulido and Comeau2019, Tâmega & Figueiredo Reference Tâmega and Figueiredo2019). CCA occur globally from the tropics to the cold waters of the polar regions (Nelson Reference Nelson2009). However, despite progress in describing their diversity and taxonomy (Sciuto et al. Reference Sciuto, Moschin, Alongi, Cecchetto, Schiaparelli and Caragnano2021), ecological knowledge of this group remains limited in polar latitudes, particularly in the Southern Hemisphere, including Antarctica.
The Antarctic region and the Southern Ocean, home to pristine ecosystems and unique biota, are pivotal to the stability of the global climate because of their ability to take up heat and CO2 as well as providing important climate feedbacks through their influence on albedo and atmospheric and oceanic circulation (Jones et al. Reference Jones, Gille, Goosse, Abram, Canziani and Charman2016, Convey & Peck Reference Convey and Peck2019). Warming is a significant issue in this region, not least with the record highest air temperature being recorded on the continent in 2020 (18.3°C on 6 February 2020 at Argentina's Esperanza research station; World Meteorological Organization 2021). Warming also melts more land-based snow and ice, increasing freshwater runoff and causing localized lowered intertidal, subtidal and shallow water salinity (Janecki et al. Reference Janecki, Kidawa and Potocka2010).
CCA are particularly sensitive to climate change, especially those inhabiting the Southern Ocean, due to the potential decline in their calcification rates resulting from decreased pH and carbonate ion (CO32-) concentration as more CO2 dissolves into ocean surface waters (Hofmann & Bischof Reference Hofmann and Bischof2014, McCoy & Kamenos Reference McCoy and Kamenos2015, Johnson et al. Reference Johnson, Rodriguez Bravo, O'Connor, Varley and Altieri2019, Sciuto et al. Reference Sciuto, Moschin, Alongi, Cecchetto, Schiaparelli and Caragnano2021). The photosynthetic performance of Antarctic intertidal CCA is yet to be investigated, as are the physiological traits that allow them to survive intertidal environmental conditions.
During a 2019 Antarctic expedition studying CCA diversity on the Antarctic Peninsula, bleaching of these algae was observed for the first time in this region. Such bleaching - the loss of pigmentation in algae - has been widely linked to thermal-stress events associated with climate change in tropical and subtropical regions (Martone et al. Reference Martone, Alyono and Stites2010, Cornwall et al. Reference Cornwall, Diaz-Pulido and Comeau2019, Montes-Herrera et al. Reference Montes-Herrera, Cimoli, Cummings, D'Archino, Nelson, Lucieer and Lucieer2024). Experiments on coralline algae have revealed a variety of causes for bleaching due to the single or combined effects of multiple environmental stressors, including water temperature change (Martone et al. Reference Martone, Alyono and Stites2010), acidification (Anthony et al. Reference Anthony, Kline, Diaz-Pulido, Dove and Hoegh-Guldberg2008), high irradiance (Dring et al. Reference Dring, Wagner, Boeskov and Lüning1996, Martone et al. Reference Martone, Alyono and Stites2010), canopy and epiphyte loss (Figueiredo et al. Reference Figueiredo, Kain (Jones) and Norton2000, Irving et al. Reference Irving, Connell, Johnston, Pile and Gillanders2005) and desiccation and salinity extremes (Sotka et al. Reference Sotka, Murren and Strand2018). Biological factors such as pathogen infection (Case et al. Reference Case, Longford, Campbell, Low, Tujula, Steinberg and Kjelleberg2011) or changes in surface bacterial assemblages (Campbell et al. Reference Campbell, Harder, Nielsen, Kjelleberg and Steinberg2011) are other reported causes of bleaching events. Although the diversity in outcomes among different experimental studies, with both positive and negative physiological responses, blurs predictions of climate change impacts, this might be a result of species-specific differences (Chan et al. Reference Chan, Halfar, Adey, Lebednik, Steneck, Norley and Holdsworth2020, Sordo et al. Reference Sordo, Santos, Barrote, Freitas and Silva2020).
Over recent decades, West Antarctica and the Antarctic Peninsula have lost ice mass rapidly, three to four times more than the rest of Antarctica combined (Convey & Peck Reference Convey and Peck2019). Therefore, it is relevant to study how photophysiology varies between CCA individuals undergoing different responses (bleaching phenotype) under the same environmental conditions, especially in the context of climate change and the development of future strategies for conservation in Antarctica led by Parties to the Antarctic Treaty.
Here, we present initial findings on the physiological state (photosynthetic performance) of bleached and non-bleached CCA assessed using chlorophyll-a fluorescence induction measured using pulse amplitude modulation (PAM) fluorometry. This study contributes to our understanding of the physiological tolerance of coralline algae that is currently lacking, especially in extreme environments such as the polar regions.
Materials and methods
CCA bleaching was observed close to the Chilean Yelcho research station on Doumer Island in a protected bay composed of rocky platforms and surrounded by glaciers, adjacent to the Peltier Channel, western Antarctic Peninsula (64°52'33"S, 63°33'46"W; Fig. 1a–c), during the 2018/2019 summer (21 February 2019). The study site is characterized by the presence of hard substrate (pebbles, larger stones, bedrock) and is protected from large waves and swells. Seven specimens each of bleached (white) and normally coloured (pale violet-red) CCA (Fig. 1d,e) were randomly collected under permit (Special Permits 198/2019 and 200/2019 issued to Universidad de Magallanes by the Instituto Antártico Chileno - INACH) from the intertidal zone. These were used to perform identification and compare their photosynthetic performances. Sampling took place around solar noon on a sunny day. Additionally, a quadrat survey was performed to analyse the bleached CCA percentage cover. Ten quadrats of 50 × 50 cm were selected randomly in the study area.
Figure 1. a. Map of the western Antarctic Peninsula coastline showing the study site (white star) and point of environmental parameter measurements (black circle), both near the Chilean Yelcho research station (black square). b. The landscape of the collection area. c. Beds of crustose coralline algae (arrowheads) in the intertidal zone. d. Stone covered by bleached Clathromorphum sp. (arrowheads) surrounded by the red alga Palmaria decipiens, also showing some bleaching spots. e. Close-up of crustose coralline algae showing the initial stages of bleaching in the margins of the algae (arrowheads).
Identification of the collected CCA was performed using specialist literature (Mendoza & Cabioch Reference Mendoza and Cabioch1985, Hommersand et al. Reference Hommersand, Moe, Amsler and Fredericq2009), and phylogenetic analyses were completed using standard markers from the plastid genome (psbA and rbcL). Molecular procedures were performed as described by Calderon et al. (Reference Calderon, Bustamante, Gabrielson, Martone, Hind, Schipper and Mansilla2021). Primer pairs used for amplification and sequencing were F1- R2 (Yoon et al. Reference Yoon, Hacket and Bhattacharya2002) for psbA and F57- 897cR and F645- R1150 (Freshwater & Rueness Reference Freshwater and Rueness1994, Lin et al. Reference Lin, Fredericq and Hommersand2002, Torrano-Silva et al. Reference Torrano-Silva, Riosmena-Rodriguez and Oliveira2014) for rbcL. In total, 13 new sequences (psbA = 6; rbcL = 7) were generated and have been deposited in GenBank (www.ncbi.nlm.nih.gov/genbank/; Table S1). Representative material has been deposited in the herbarium of Criptógamas Subantárticas (LEMAS) del Laboratorio de Ecosistemas Marinos Antárticos y Sub-antárticos of the Universidad de Magallanes, Punta Arenas, Chile (UMAG).
Photosynthetic activity was measured in situ on crusts using a pulse-amplitude-modulated chlorophyll fluorometer ‘MINI-PAM-II' (Walz GmbH, Germany). Photosynthetic performance was measured in vivo after 15 min of dark adaption, and rapid light curves (RLC) were recorded using an actinic light of 0–2950 μmol photons m-2 s-1 (Marambio et al. Reference Marambio, Rodríguez, Rosenfeld, Méndez, Ojeda and Ocaranza2023). The standard photosynthetic parameters as relative maximum electron transport rate (rETRmax), electron transport efficiency (α, initial linear slope), light saturation point of photosynthesis (E k) and quantum yield of photosystem II (F v/F m) were estimated for both bleached and coloured CCA following the procedures described by Wilson et al. (Reference Wilson, Blake, Berges and Maggs2004) and Méndez et al. (Reference Méndez, Marambio, Ojeda, Rosenfeld, Rodríguez, Tala and Mansilla2018). Studies of photosynthetic performance commonly use a minimum of two to three measurements per group (see Gómez et al. Reference Gómez, Weykam, Klöser and Wiencke1997, Payri et al. Reference Payri, Maritorena, Bizeau and Rodière2001, Chisholm Reference Chisholm2003). Here, the photosynthetic parameters rETRmax, α, E k and the ratio of F v/F m were measured on three individuals each of bleached and coloured CCA. Temperature (°C) and salinity (psu) were measured using an SBE 19plus v2 CTD device (Sea-Bird Scientific, USA) in the water column, and pH was measured using a portable pH meter ProfiLine pH 3110 (WTW, Germany). Radiation data were obtained from WeatherOnline Ltd - Meteorological Services (www.weatheronline.co.uk) for Palmer Station (64°46'S, 64°03'W), 26 km north-west of our collection point. Photosynthetically active radiation (PAR) was calculated using the R package 'bigleaf' to convert radiation (W m-2) to photosynthetic photon flux density (PPFD).
Results
We report the presence of bleached CCA for the first time in the Antarctic Peninsula region. The specimens collected were consistent with the morphological description of the genus Clathromorphum (Hapalidiales, Rhodophyta). The phylogenetic reconstruction based on psbA and rbcL sequences (Fig. S2) did not group our specimens with the generitype Clathromorphum compactum, rather clustering them in an independent lineage within the order Hapalidiales (Figs S1 & S2). Since the identification of coralline algae is notoriously difficult, further studies are required to confirm the taxonomic position of these specimens, hereafter referred to as Clathromorphum sp.
Approximately 20% of intertidal CCA were bleached. Most of the instances of bleached CCA occurred at apparently random points on extensive solid rock surfaces and hemispherical boulders (~15–20 cm radius), the bleached area covering up to 70% of such boulders (Fig. 1d). Bleaching initiated at the periphery of the encrusting algae, advancing irregularly in the undulating margins (Fig. 1e). The surrounding red alga Palmaria decipiens also showed bleached regions at the margins and tips of its thalli (Fig. 1d). In situ environmental variables recorded at the study site included pH 8.1, temperatures between +4.5°C (at 0 m) and +1.7°C (at 25 m depth; Fig. 2a) and a gradient of salinity in the water column ranging from 0.15 (at 0 m) to 32.39 (at 25 m depth) psu (Fig. 2b), with the presence of a halocline between 10 and 12 m (3.12–16.3 psu; Table S2). PAR varied between 492.7 and 740.4 μmol photons m-2 s-1 (Table S3).
Figure 2. Variation in a. temperature and b. salinity in the water column. Photosynthetic parameters of healthy (black bars) and bleached (grey bars) crustose coralline algae calculated from chlorophyll-a fluorescence measurements for c. relative maximum electron transport rate, (rETRmax), d. light saturation point of photosynthesis (E k), e. electron transport efficiency (α) and f. the quantum yield of photosystem II (F v/F m). r.u. = relative units.
Despite the limited number of specimens included in the photophysiological analysis, some interesting observations were apparent.
For instance, similar ranges of measurement were recorded for rETRmax, α and F v/F m in both CCA. rETRmax varied from 3.45 to 23.80 relative units (r.u.) in coloured CCA and from 15.48 to 16.48 r.u. in bleached CCA, while α ranged from 0.05 to 0.21 (μmol photons m-2 s-1)-1 in coloured CCA and from 0.08 to 0.11 (μmol photons m-2 s-1)-1 in bleached CCA. Furthermore, F v/F m varied from 0.28 to 0.38 and from 0.11 to 0.39 in coloured and bleached CCA, respectively. Conversely, E k ranged from 69.87 to 115.99 μmol photons m-2 s-1 and from 146.08 to 209.36 μmol photons m-2 s-1 in coloured and bleached CCA, respectively (Fig. 2c–f & Table I).
Table I. Photosynthetic parameters of the crustose coralline algae (CCA) Clathromorphum sp. (bleached and coloured).
α = electron transport efficiency; E k = light saturation point of photosynthesis; F v/F m = quantum yield of photosystem II; rETRmax = relative maximum electron transport rate.
Discussion
Photosynthetic performance of the intertidal calcareous coralline algae Clathromorphum sp. from Antarctica has not been explored previously. The genus Clathromorphum is very common along the Antarctic Peninsula, where it can dominate communities in intertidal pools and the subtidal seascape (Mendoza & Cabioch Reference Mendoza and Cabioch1985, Hommersand et al. Reference Hommersand, Moe, Amsler and Fredericq2009). It typically occurs low on the shore (< 0.3 m tide height) and in mid-intertidal tidepools, where exposure to light stress and desiccation is likely to be reduced during low tide. Here, it was not possible to achieve species-level identification since three species of the genus Clathromorphum - C. annulatum, C. lemoineanum and C. obtectulum - have been reported in West Antarctica, and descriptions suggest that they share habitat and ecological features (Mendoza & Cabioch Reference Mendoza and Cabioch1985, Hommersand et al. Reference Hommersand, Moe, Amsler and Fredericq2009). Thus, further taxonomic studies are required to confirm the phylogenic position of our specimens.
Our results derived from RLC measures, such as rETRmax (r.u.), E k (μmol photons m-2 s-1) and α ((μmol photons m-2 s-1)-1), of both coloured (3.45–23.80 r.u.; 69.87–115.99 μmol photons m-2 s-1; 0.05–0.21 (μmol photons m-2 s-1)-1) and bleached CCA (15.48–16.48 r.u.; 146.08–209.36 μmol photons m-2 s-1; 0.08–0.11 (μmol photons m-2 s-1)-1) were consistent with values reported in intertidal uncalcified red algae from Antarctica, such as Pyropia endiviifolia (10.82 ± 1.76 r.u.; 96.61 ± 26.13 μmol photons m-2 s-1; 0.11 ± 0.02 (μmol photons m-2 s-1)-1), Palmaria decipiens (13.36 ± 3.97 r.u.; 78.58 ± 17.66 μmol photons m-2 s-1; 0.17 ± 0.05 (μmol photons m-2 s-1)-1) and Iridaea cordata (18.61 ± 2.08 r.u.; 101.76 ± 15.17 μmol photons m-2 s-1; 0.18 ± 0.04 (μmol photons m-2 s-1)-1; Gómez et al. Reference Gómez, Navarro and Huovinen2019). The photosynthesis-irradiance (P-E) curve parameters (i.e. rETRmax and E k), which vary in relation with depth (Gómez et al. Reference Gómez, Navarro and Huovinen2019), are overall higher in eulittoral species than those collected from the subtidal zone and are not constrained by algal taxonomy (Huovinen & Gómez Reference Huovinen and Gómez2013). Additionally, the light requirements for photosynthesis (E k) measured here in bleached CCA (E k = 146.08–209.36 μmol photons m-2 s-1) were the highest values recorded for a shallow subtidal red alga in Antarctica, followed by Curdiea racovitzae (E k = 92.73 ± 8.22 μmol photons m-2 s-1) and I. cordata (E k = 121.26 ± 27.53 μmol photons m-2 s-1) and Pantoneura plocamioides (E k = 149.39 ± 30.06 μmol photons m-2 s-1; Gómez et al. Reference Gómez, Navarro and Huovinen2019), further supporting the notion of their strong resilience to exposure to high levels of PAR (Payri et al. Reference Payri, Maritorena, Bizeau and Rodière2001, Wiencke et al. Reference Wiencke, Clayton, Gómez, Iken, Lüder and Amsler2007). Polar algae from the upper sublittoral or eulittoral typically show high values of saturation points for photosynthesis (E k > 50 μmol photons m-2 s-1; Weykam et al. Reference Weykam, Gómez, Wiencke, Iken and Klöser1996, Gómez et al. Reference Gómez, Weykam, Klöser and Wiencke1997, Payri et al. Reference Payri, Maritorena, Bizeau and Rodière2001).
Photosynthetic studies of CCA in polar regions have focused to date on subtidal samples, complicating the comparison of parameters (Kühl et al. Reference Kühl, Glud, Borum, Roberts and Rysgaard2001, Roberts et al. Reference Roberts, Kühl, Glud and Rysgaard2002, Schwarz et al. Reference Schwarz, Hawes, Andrew, Mercer, Cummings and Thrush2005, Schoenrock et al. Reference Schoenrock, Bacquet, Pearce, Rea, Schofield and Lea2018). Despite this, the measured photosynthetic performance ranges (rETRmax; E k) of both normally coloured and bleached CCA from Doumer Island were higher than those of other intertidal calcareous algae studied in temperate regions, such as Lithothamnion glaciale from the west coast of Scotland (3.83 ± 0.52 r.u.; 54.61 ± 5.29 μmol photons m-2 s-1) and Chamberlainium sp. from Garorim Bay in South Korea (8.2 ± 0.26 r.u.; 57.1 ± 2.6 μmol photons m-2 s-1; Burdett et al. Reference Burdett, Hennige, Francis and Kamenos2012, Kim et al. Reference Kim, Kim, Moon, Lee, Jeong and Diaz-Pulido2020).
Most intertidal algal species examined in Antarctica have previously been shown to have high photosynthetic efficiency (α > 0.15 (μmol photons m-2 s-1)-1; Gómez et al. Reference Gómez, Weykam, Klöser and Wiencke1997, Gómez & Huovinen Reference Gómez and Huovinen2011), while the quantum yield of photosystem II (PSII; F v/F m) for red algae is typically 0.5–0.6 (Dring et al. Reference Dring, Wagner, Boeskov and Lüning1996, Burdett et al. Reference Burdett, Hennige, Francis and Kamenos2012). The low values of F v/F m measured here in both bleached (0.043–0.363) and coloured CCA (0.277–0.377) might suggest physiological stress and inefficiency of energy transfer to the PSII reaction centres (Dring et al. Reference Dring, Wagner, Boeskov and Lüning1996, Wilson et al. Reference Wilson, Blake, Berges and Maggs2004, Schoenrock et al. Reference Schoenrock, Bacquet, Pearce, Rea, Schofield and Lea2018), perhaps associated with exposure to low salinities. Our observations showed a strong gradient in salinity in the water column from hyposaline conditions (1.37 psu at 0.5 m depth) to a halocline between 10 and 12 m depth (3.12–16.30 psu), so further experimental work, including increase sample size and effort, is required to explore whether a reduction in salinity has major implications for photosynthesis in Antarctic Clathromorphum sp., as metabolic processes that control salinity tolerance also remain poorly understood in Antarctic calcareous algae (Karsten Reference Karsten, Wiencke and Bischof2012). Future in situ and laboratory experimental studies should also include short-term exposure to salinities close to freshwater values as well to reflect stresses associated with freshwater runoff across the shoreline from melt.
As we were not able to sample or monitor CCA over time, it was not possible to assess the duration of bleaching or recovery time (or if recovery occurred) of these bleached CCA. Thus, further studies that monitor pigment content, calcification rate and CaCO3 skeleton thickness, singlet-oxygen (1O2) production and concentrations of antioxidant dimethylated sulphur compounds (dimethylsulphoniopropionate (DMSP) and dimethyl sulphoxide (DMSO)) over seasonal timescales are now required, as has been carried out in previous studies of other non-polar CCA (Latham Reference Latham2008, Burdett et al. Reference Burdett, Hatton and Kamenos2015a, Reference Burdett, Hatton and Kamenos2015b, Schoenrock et al. Reference Schoenrock, Bacquet, Pearce, Rea, Schofield and Lea2018, Muth et al. Reference Muth, Esbaugh and Dunton2020, Montes-Herrera et al. Reference Montes-Herrera, Cimoli, Cummings, D'Archino, Nelson, Lucieer and Lucieer2024).
Bleaching is often thought to be an indicator of death (Irving et al. Reference Irving, Connell and Elsdon2004), although colour restoration has been observed after provision of shade, low irradiance exposure or salinity values > 30 psu (Dring et al. Reference Dring, Wagner, Boeskov and Lüning1996, Figueiredo et al. Reference Figueiredo, Kain (Jones) and Norton2000, Irving et al. Reference Irving, Connell and Elsdon2004, Muth et al. Reference Muth, Esbaugh and Dunton2020). However, measurements such as those reported here, confirming non-zero ETR values in bleached CCA, suggest bleaching is not necessarily associated with algal death. The study site was characterized by specific conditions (high irradiance and low salinity) that have been associated with bleaching and shifts in photosynthetic parameters of coralline algae in previous studies (Kirst Reference Kirst1989, Roberts et al. Reference Roberts, Kühl, Glud and Rysgaard2002, Thomas & Dieckmann Reference Thomas and Dieckmann2002, Irving et al. Reference Irving, Connell, Johnston, Pile and Gillanders2005, Latham Reference Latham2008, Burdett et al. Reference Burdett, Hatton and Kamenos2015b, Schoenrock et al. Reference Schoenrock, Bacquet, Pearce, Rea, Schofield and Lea2018). Our observations highlight the importance of establishing appropriate monitoring of marine environmental variables in key locations (as proposed within the Scientific Committee on Antarctic Research (SCAR) Antarctic Near-Shore and Terrestrial Observation System (ANTOS) initiatives, www.scar.org/science/cross/antos) in order to provide data that will assist in identifying and tracking the origin and duration of marine anomalies, since the environmental conditions that could have caused the bleaching of CCA reported here could have initiated before our observations.
While bleaching has been documented in CCA at temperate and tropical latitudes (Figueiredo et al. Reference Figueiredo, Kain (Jones) and Norton2000, Martone et al. Reference Martone, Alyono and Stites2010, Vargas-Ángel Reference Vargas-Ángel2010, Campbell et al. Reference Campbell, Harder, Nielsen, Kjelleberg and Steinberg2011), there are no previous reports of its occurrence as a natural event in the polar regions. Subtidal video recordings (Supplemental Material) showed bleaching in almost 80% of CCA located at 8–11 m depth, where the halocline was observed. Historically, the area between Anvers Island and Adelaide Island along the coast of the western Antarctic Peninsula (64°S–67°35'S), where our observations were made, has been very poorly studied, with the existence or extent of any marine changes occurring being undocumented (Wiencke & Amsler Reference Wiencke, Amsler, Wiencke and Bischof2012). Our initial study provides a starting point to both urgently draw attention to this bleaching event in the Antarctic Peninsula region and to improve understanding of bleaching in CCA and of its wider implications for Antarctic marine communities. It is already clear that bleached CCA have relatively healthy photophysiology responses (rETRmax, E k), but with lower photosynthetic efficiency (F v/F m), possibly associated with the low salinities recorded in the study area; however, seasonal monitoring of key environmental parameters and mesocosm experiments across the southern polar latitudes are urgently required to confirm this hypothesis.
A range of consequences of climatic and other environmental changes in Antarctica have been reported (e.g. biological invasions, changing sea ice, ocean acidification and also now bleaching of CCA; Anthony et al. Reference Anthony, Kline, Diaz-Pulido, Dove and Hoegh-Guldberg2008, Abram et al. Reference Abram, Mulvaney, Vimeux, Phipps, Turner and England2014, Convey & Peck Reference Convey and Peck2019, Siegert et al. Reference Siegert, Atkinson, Banwell, Brandon, Convey and Davies2019, Reference Siegert, Bentley, Atkinson, Bracegirdle, Convey and Davies2023), threats that are placing its unique and often highly endemic biodiversity at risk, yet are still waiting for political acceptance, reaction and effective response. Notwithstanding, an important element in any future strategy is that funding agencies from the national Antarctic Treaty Parties need now to develop ambitious commitments to tackle these growing concerns by investing in research, monitoring and protection programmes across Antarctica.
CRediT authorship contribution statement
MSC, DEB, AM and PC conceived the study. MSC, DEB, AM, FM and JPR conducted fieldwork. FM and JM performed and assessed the photosynthetic analyses. JPR collected environmental parameters. MSC, DEB and PC drafted the manuscript. All authors discussed the results, contributed to revisions of the manuscript, approved the final version and agree to be held accountable for the content.
Acknowledgements
We thank Instituto Antártico Chileno (INACH) for logistical support and the Chilean Army, including the crew of the ship Marinero Fuentealba (OPV-83), which provided transport. We also thank Michael Wynne and Flavio Augusto de Souza Berchez for helpful suggestions and comments that significantly improved the manuscript. We acknowledge the reviewers for their thoughtful comments and constructive feedback that improved our manuscript.
Financial support
This study was supported by the Chilean Research Council (ANID) Projects Fondecyt 3180539 (MSC) and Fondecyt 1180433, Conicyt PIA Apoyo CCTE AFB170008 through IEB (AM), as well as CHIC ANID FB210018. PC is supported by NERC core funding to the BAS 'Biodiversity, Evolution and Adaptation' Team.
Competing interests
The authors declare no relevant financial or non-financial interests to disclose.
Data availability
Molecular data are available on GenBank (OQ471937-OQ471949).
Statement
All data are included in the Supplemental Material. The subtidal video is deposited at https://doi.org/10.6084/m9.figshare.22177178.v1.
Supplemental material
Two supplemental figures and three supplemental tables will be found at https://doi.org/10.1017/S0954102024000361.
Open access
