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Publicly Available Published by De Gruyter November 30, 2023

Vertical distribution of brown and red macroalgae along the central Western Antarctic Peninsula

  • Charles D. Amsler

    Charles D. Amsler is a Professor of Biology at the University of Alabama at Birmingham. He is a phycologist by background and much of his Antarctic research has focused on the chemical ecology of benthic organisms. He has also led or co-led projects examining the impacts of climate change on benthic communities including this one examining the impacts of declining sea ice. He has participated in 24 Antarctic expeditions since 1985–86, and has made over 1000 Antarctic research scuba dives.

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    , Margaret O. Amsler

    Margaret O. Amsler is a Researcher V at the University of Alabama at Birmingham. Her master’s degree centered on the Antarctic krill and lead to participation in twelve expeditions with emphasis on krill. The majority of her thirty-two plus expeditions focused on the benthos studying chemical ecology of benthic organisms, documenting the distribution and abundance of deep-sea crabs, examining the impacts of sea ice cover on benthic communities, and investigating the impacts of ocean acidification on macroalgae and benthic invertebrates.

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    , Sabrina Heiser

    Sabrina Heiser earned her doctor’s degree in biology in 2023 and is currently a postdoctoral researcher in Dr. Deana Erdner’s lab at the University of Texas at Austin Marine Science Institute. She is a benthic ecologist studying the population and chemical ecology of algae assemblages focusing on understanding community structure within ecosystems. She has worked from the tropics to the poles and studied chemical defense diversity in macroalgae as well as community composition of benthic microalgal communities.

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    , James B. McClintock ORCID logo , Katrin Iken

    Katrin Iken is a professor of Marine Biology with a research focus on benthic ecology, biodiversity, and food webs. She has worked extensively in both the Arctic and Southern oceans, ranging from SCUBA-diving based studies on macroalgae in coastal systems to ship-based operations for studying shelf and deep-sea systems.

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    , Aaron W. E. Galloway

    Aaron W. E. Galloway is an Associate Professor at the Oregon Institute of Marine Biology, the coastal marine lab of the University of Oregon. Dr. Galloway leads the Coastal Trophic Ecology Lab, which is generally focused on trophic inferences in marine benthic food webs, with an emphasis on algae-invertebrate interactions. To do this work, the group often uses fatty acids as trophic biomarkers, paired with underwater natural history, scuba diving, lab and field experimentation, and modeling.

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    and Andrew G. Klein ORCID logo
From the journal Botanica Marina

Abstract

Fleshy macroalgae dominate the hard bottom, shallow waters along the Western Antarctic Peninsula (WAP). Although there are numerous reports on their ecology, geographic distribution, and to a lesser extent, vertical (depth) distribution in the northern portions of the WAP, much less is known farther south along the central portion of the WAP. Here we provide the first report of the vertical distributions of brown and red fleshy macroalgae in this region based on scuba-derived collections at 14 study sites between southern Anvers Island (64.8°S, 64.4°W) in the north and central Marguerite Bay (68.7°S, 67.5°W) in the south. Although several overstory brown macroalgal species that can be common along the northern WAP including Desmarestia anceps and Cystosphaera jacquinotii are mostly absent from the central WAP, the vertical distributions of the brown macroalgae Desmarestia menziesii and Himantothallus grandifolius are similar to the northern WAP even though their percent cover is much lower. Likewise, the vertical distribution of the 14 most widespread red macroalgae, where they occur, mirrored those known from the northern part of the WAP even though macroalgal cover, biomass, and total species richness declined markedly to the south across this region due to increasing sea ice concentrations.

1 Introduction

The macroalgal flora of Antarctica consists of over 150 currently known species, which is likely a substantial underestimate of the actual species richness (Oliveira et al. 2020). Macroalgae are distributed throughout the entire coastline of the continent including a few species as far south as southern McMurdo Sound, which is as far south globally as open water ever occurs (Wiencke and Amsler 2012; Wiencke et al. 2014). However, many, probably most, of the known species are only found along the western side of the continental Antarctic Peninsula and the islands to its west and north (Oliveira et al. 2020; Wiencke and Clayton 2002; Wiencke et al. 2014). As commonly done, herein we refer to this entire region as the Western Antarctic Peninsula (WAP).

The vast majority of published reports on the WAP flora come from observations between the South Orkney Islands in the northeast and Anvers Island in the southwest (Figure 1), which for convenience we hereafter call the “northern WAP.” General descriptions of macroalgal distribution and ecology in the northern WAP date back to 1906 with at least 35 published reports since 1965 (see Amsler et al. 2023, Appendix 1) in addition to numerous other reports comprised mainly of species lists. Farther south, waters near Rothera Station on Adelaide Island (Figure 1) are relatively well studied (e.g., Rozema et al. 2017; Venables et al. 2023) but there are only limited reports of macroalgal diversity or abundance (Barnes and Brockington 2003; Bowden 2005; Mystikou et al. 2014). From these few reports it is evident that the Rothera area has many fewer macroalgal species with lower macroalgal cover and biomass than commonly reported in the northern WAP. Unfortunately, until recently, the only other published information on the flora along the WAP south of Anvers Island were species lists and casual observations from the early 1970s (DeLaca and Lipps 1976; Moe and DeLaca 1976) at nine sites extending as far south as Marguerite Bay (Figure 1). For convenience in this article, we refer to this area south of Anvers Island as the “central WAP.”

Figure 1: 
Study sites along the central Western Antarctic Peninsula. Inset shows the entire northern and central portions of the Antarctic Peninsula. The 14 research sites, designated north to south as A through N, were surveyed between April 23 and May 18, 2019. Their locations spanned the range of annual sea ice coverage (color scale bar). Modified from Amsler et al. (2023).
Figure 1:

Study sites along the central Western Antarctic Peninsula. Inset shows the entire northern and central portions of the Antarctic Peninsula. The 14 research sites, designated north to south as A through N, were surveyed between April 23 and May 18, 2019. Their locations spanned the range of annual sea ice coverage (color scale bar). Modified from Amsler et al. (2023).

In 2019, we participated in a research cruise using scuba diving to make by-hand collections of macroalgae and macroinvertebrates and to record video transects of the benthos at four study sites off southern Anvers Island and 10 additional sites located in the central WAP. Fleshy macroalgal cover was strongly, negatively correlated with annual sea ice concentration while overall community diversity was positively correlated with fleshy macroalgal cover (Amsler et al. 2023). Macroalgal stable isotope values varied little across the latitudinal and sea ice range but, across the overall communities, food web length and trophic niche width were negatively correlated with sea ice cover (Iken et al. 2023). Although Amsler et al. (2023) present species lists for each site as well as macroalgal cover both overall and by depth at each site by macroalgal group, describing the vertical (depth) distribution of individual macroalgal species was beyond the scope of that report. Nonetheless, information on the vertical distributions of macroalgae, particularly red macroalgae, have been completely lacking from the central WAP. This contribution fills that information gap for the overstory brown and most widespread red macroalgal species, which will be important for making predictions about how benthic communities in the central WAP will be impacted by climate change (e.g., Amsler et al. 2023; Deregibus et al. 2023).

2 Materials and methods

Fourteen study sites (Figure 1) between the Joubin Islands off southwest Anvers Island (64.8°S, 64.4°W) in the north and the Terra Firma Islands in Marguerite Bay (68.7°S, 67.5°W) in the south were sampled in April and May 2019. The sites were selected because they spanned the range of satellite-determined sea ice concentrations in this region and because they were within a defined window of satellite-determined open water turbidity. Further information on site selection parameters, coordinates, sea ice concentrations, and turbidity levels are detailed in Amsler et al. (2023). Sea ice concentration data presented herein were derived from weekly National Ice Center charts (Dedrick et al. 2001; Fetterer 2006) averaged over the entire five year period preceding sampling (1 April 2014 through 1 April 2019).

Sites were designated by letters from north (A) to south (N) (Figure 1). At each site, vertical transects were surveyed by scuba divers. Where bottom topography allowed, transects began at 40 m depth and ended at 5 m depth. All sites contained transects that covered the 20–5 m depth range, and 11 of the sites had transects starting at least at 30 m depth. At each 5 m depth interval between 35 and 5 m depth the transect included a 5 m long horizontal component (cf. Amsler et al. 2023) along which one of each macroalgal species observed was sampled and placed into an individually labeled bag for later identification. Macroalgae were identified, in most cases to species level, upon their return to the research ship. At least one pressed voucher specimen of each species at each site was prepared. Upon return to the United States, the voucher material was compared to previously identified herbarium specimens and to each other across sites to confirm identifications and ensure consistency of identifications across the study sites. Voucher macroalgae are archived in the macroalgal herbarium of C. Amsler at the University of Alabama at Birmingham. Only macroalgae that were attached to the substratum were included; unattached, drift macroalgae were not collected to ensure that only macroalgae growing at that depth were included in the dataset. Three parallel vertical transects spaced approximately 100 m apart were surveyed at all sites except for site I where a logistical issue limited us to two transects. At sites F, H, and M, bottom topography prevented one of the three transects from beginning as deep as the others, as also occurred in two of the transects at site N. At site J, the sample bag from 10 m depth on one transect was lost. After the transects at each site were completed, with the exception of site I, an additional scuba dive was made to collect macroalgal species that were present at the site but not collected along the horizontal components of the transects.

As a semi-quantitative representation of the vertical distribution of macroalgae across the geographic range of our samples, we tabulated the number of transects at each depth at each site where a species was present. This was done for five brown algal species that comprise the overstory canopy as well as for the 14 (of 27 total) understory red algal species that were collected at five or more sites (Amsler et al. 2023). Amsler et al. (2023) reported Pantoneura plocamioides from nine sites due to a data transcription mistake. The correct number of sites is five as reported here. Iridaea ‘cordata’ is reported with the specific epithet in single quotes because this entity on the WAP is genetically distinct from the type locality of I. cordata in South America and almost certainly represents a different but heretofore unnamed species (Hommersand et al. 2009; Ocaranza-Barrera et al. 2019). ‘Myriogramme smithii’ is reported in single quotes because algae identified as this species in Antarctica probably represent a new species of Hymenena (Hommersand et al. 2009). Hymenocladiopsis spp. are reported as such because the number and identity of Antarctic species in this genus is unclear (Hommersand et al. 2009). Our collections of Hymenocladiopsis probably represent a single species but we cannot be certain. Plocamium sp. is reported as such because it is genetically distinct from all described Plocamium spp. elsewhere in the world (Dubrasquet et al. 2018; Hommersand et al. 2009) but has not yet been formally described as a new species. All species names used and the taxonomic authorities for them are those currently accepted in AlgaeBase (Guiry and Guiry 2023).

In addition to algal collections, each transect was video recorded at 4K resolution using a Paralenz DC+ underwater cameras and two Light and Motion Sola 3800 video lights. A custom-built mount held two Z-Bolt SCUBA-BL low temperature blue laser pointers 10 cm apart to provide scaling for video analyses. Video stream processing of transects was accomplished with VLC software (VideoLAN Organization) and Coral Point Count with Excel extensions (CPCe 4.1; National Coral Reef Institute at Nova Southeastern University; Kohler and Gill 2006). The data were compiled using the automatic Excel spreadsheet generation feature of CPCe (Kohler and Gill 2006) to yield percent cover data as described in detail by Amsler et al. (2023). Camera malfunctions resulted in the loss of video from one transect each at sites H and K.

Red macroalgae often could not be confidently identified to species in the recordings and therefore we are not able to report percent cover data for them. With the exception of Desmarestia menziesii and D. anceps, which could only be distinguished from each other if a holdfast was in clear view, the other overstory brown algae (Himantothallus grandifolius, D. antarctica, and Cystosphaera jacquinotii) could be confidently identified to species. Unlike the by-hand collections, drift macroalgae usually could not be clearly distinguished from attached algae in the video analyses so the percent cover data probably include some unattached macroalgae.

Graphs of the data (Figures 2 5) were prepared using Microsoft Excel and PowerPoint. Figure 1 was prepared with ArcGIS 2.X, ArcGIS 3.X, and Adobe Illustrator.

Figure 2: 
Vertical distribution of brown macroalgal species by the number of transects in which they were present in the diver by-hand collections. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy macroalgae were present at site K so it is not included. Only two transects were sampled at site I, so the abscissa only extends to two for that site. Single blue asterisks indicate one less transect collection at that depth at that site, two asterisks indicate two less; “(present)” indicates that the species was found in general collections at the site but was not present in the transect collections.
Figure 2:

Vertical distribution of brown macroalgal species by the number of transects in which they were present in the diver by-hand collections. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy macroalgae were present at site K so it is not included. Only two transects were sampled at site I, so the abscissa only extends to two for that site. Single blue asterisks indicate one less transect collection at that depth at that site, two asterisks indicate two less; “(present)” indicates that the species was found in general collections at the site but was not present in the transect collections.

Figure 3: 
Vertical distribution of Desmarestia menziesii and Desmarestia anceps combined and of Himantothallus grandifolius at horizontal depth intervals from video transect analyses. Means + standard error of mean. Sample size was two at sites H, I, and K and three at all other sites. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy macroalgae were present at site K so it is not included. “(present)” indicates that the species was found in general collections at the site but was not present under a random dot in the video analyses.
Figure 3:

Vertical distribution of Desmarestia menziesii and Desmarestia anceps combined and of Himantothallus grandifolius at horizontal depth intervals from video transect analyses. Means + standard error of mean. Sample size was two at sites H, I, and K and three at all other sites. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy macroalgae were present at site K so it is not included. “(present)” indicates that the species was found in general collections at the site but was not present under a random dot in the video analyses.

Figure 4: 
Vertical distribution of seven red macroalgal species by the number of transects in which they were present in the diver by-hand collections. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy red macroalgae were present at site K, and none of the species included in this report were present at site N. Only two transects were sampled at site I, so the abscissa only extends to two for that site. Single blue asterisks indicate one less transect collection at that depth at that site; “(present)” indicates that the species was found in general collections at the site but was not present in the transect collections.
Figure 4:

Vertical distribution of seven red macroalgal species by the number of transects in which they were present in the diver by-hand collections. Sites are ordered by National Ice Center average sea ice concentrations from 2014 to 2019. No fleshy red macroalgae were present at site K, and none of the species included in this report were present at site N. Only two transects were sampled at site I, so the abscissa only extends to two for that site. Single blue asterisks indicate one less transect collection at that depth at that site; “(present)” indicates that the species was found in general collections at the site but was not present in the transect collections.

Figure 5: 
Vertical distribution of seven additional red macroalgal species by the number of transects in which they were present in the diver by-hand collections. Other details as in Figure 4.
Figure 5:

Vertical distribution of seven additional red macroalgal species by the number of transects in which they were present in the diver by-hand collections. Other details as in Figure 4.

3 Results

The total number of species in each group collected at each site is presented in Table 1. The single green algal species present at any site was Lambia antarctica. Desmarestia menziesii was the most widespread species (Figure 2). It was present at all sites except site K where no fleshy macroalgae at all were present. Desmarestia menziesii was not observed on any of the transects at site D but was found on the subsequent general collection dive. It was most commonly present in the shallower transects and was usually the only brown alga collected at 5 m depth (Figure 2). D. anceps was only collected at three sites (Figure 2). It was observed between 5 and 25 or 30 m at sites A and B but only at a single depth (15 m) on one transect at site G. As noted above, D. menziesii and D. anceps could only rarely be confidently separated in the video transects but except for sites A, B, and 15 m depth at site G, the percent cover data for the two species combined (Figure 3) should represent only D. menziesii. The vertical distribution by percent cover of D. menziesii and D. anceps combined was usually similar in terms of the number of transects at which it was collected by hand, but this was not always true, for example at site L where it was only collected by hand at 5 m but was only present in the video data between 10 and 30 m (Figures 2 and 3).

Table 1:

Number of macroalgal species found at each site by group.

Site Fleshy macroalgal species
Brown Red Green Total
A 5 17 1 23
B 7 18 1 26
C 4 12 1 17
D 4 15 0 19
E 2 13 0 15
F 4 16 1 21
G 2 16 1 19
H 2 10 1 13
I 2 5 0 7
J 3 14 0 17
K 0 0 0 0
L 1 3 0 4
M 2 2 0 4
N 1 1 0 2

Himantothallus grandifolius had the widest distribution across depths of the brown algae in terms of both presence-absence in transects (Figure 2) and percent cover (Figure 3) although it was never observed at 5 m depth. Cystosphaera jacquinotii was only observed at 20 m and deeper in the four northernmost sites (A through D; Figure 2). However, its percent cover was usually low where it was observed, with a maximum cover of 13.3 % at the single depth (30 m) and transect where it occurred at site C. Desmarestia antarctica was present across depths, albeit not at every single depth, in four of the six sites where it occurred in the presence-absence, by-hand collections (Figure 2). However, its percent cover only exceeded 4 % at 5 m depth at sites B and C (10.3 ± 6.2 and 21.0 ± 5.4, means ± standard error, respectively).

Red macroalgae were found at all sites except K, although at site N the only red macroalgal species was Phyllophora antarctica, for which data are not included herein as it was only present at three sites total (Amsler et al. 2023). Iridaea ‘cordata’ was present at all other sites except for site L (Figure 4). It was most commonly observed at 5 m depth but at some sites was found as deep as 35 m (Figure 4). Plocamium sp. was present across most or all of the depth range at all sites where it occurred (Figure 4). A similar pattern with sometimes a bias towards shallower depths was observed in Sarcopeltis antarcticus and Trematocarpus antarcticus, and sometimes with a bias towards deeper depths in Myriogramme manginii (Figure 4). The seven species presented in Figure 5 were most commonly found at deeper depths but some ranged shallower, particularly at the three highest ice cover sites (M, G, and I; Figure 5).

4 Discussion

Compared to the many reports of brown macroalgal distribution along the northern WAP (reviewed by Wiencke et al. 2014), it is perhaps surprising that at sites (except site J) where Himantothallus grandifolius occurred it was always the dominant overstory brown alga below 5 m depth in terms of percent cover. In the northern WAP it is common for Desmarestia anceps to dominate in terms of cover and biomass at intermediate depths, often between D. menziesii dominating in shallower water and H. grandifolius below (e.g., Brouwer et al. 1995; Klöser et al. 1996; Quartino et al. 2001; Valdivia et al. 2015). However, D. anceps is not found at all sites in the region where other Desmarestia spp. or H. grandifolius occur (e.g., Moe and DeLaca 1976; Pellizzari et al. 2017, 2023; Valdivia et al. 2015). Our (CDA, MOA, SH, and KI) personal observations from well over 1500 dives in the vicinity of sites A through D (particularly near B and C) since 1985, including semi-quantitative observations presented in Heiser et al. (2023; Table S2), are that while D. anceps is often the dominant overstory macroalga between 5–10 and 30 m or sometimes deeper, it is not uncommon for it to be absent at some sites or to have only limited cover as in the present dataset. As discussed in more detail in Amsler et al. (2023), our observation of D. anceps at a single depth on a single transect at site G is the only credible report of it south of 65°S latitude, a range limitation probably resulting from daylength requirements for reproduction in its microscopic gametophyte phase (Wiencke et al. 1996). Although Klöser et al. (1994) hypothesized that D. menziesii and D. anceps could competititevly exclude H. grandifolius except at greater depths at King George Island (Figure 1), our data do not support that conclusion in the central WAP. Desmarestia menziesii was found throughout the depth range sampled in by-hand collections at many of the sites but, where present, H. grandifolius dominated in the intermediate depth range often dominated by D. anceps in the northern WAP. Culture studies of gametophytes of the other members of the Desmarestiaceae that we observed indicate that the daylength requirements of their gametophytes should not limit their geographic distribution as is the case with D. anceps (Matula et al. 2022; Wiencke and Clayton 1990; Wiencke et al. 1991, 1995).

As also discussed in Amsler et al. (2023), the lack of brown macroalgae at site D above 20 m in the percent cover data and at 5 m in the by-hand collections is probably due to iceberg scouring long enough prior to our 2019 collections to allow presumably shorter-lived red macroalgae to recolonize but not longer-lived overstory brown macroalgae. Site D is in the Wauwermans Island group and, at another location in the island group in a previous study, we observed a high cover of D. menziesii, D. anceps, and H. grandifolius throughout the 5–29 m depth range where observations were recorded (Heiser et al. 2023; Table S2). Ice scour probably also explains the discrepancy in our data at site L where D. menziesii was present only at 5 m in by-hand collections but only between 10 and 30 m in the percent cover data. As noted in Section 2, only macroalgae attached to substrata were collected by hand but the video analysis could not reliably distinguish attached versus unattached, drift algae. The D. menziesii observed in the video analysis at site L were likely individuals that had been dislodged from the substratum by ice scour. The sea urchin Sterechinus neumayeri was particularly abundant at site L, although not at 5–10 m (Amsler et al. 2023), and commonly covers itself with drift macroalgae (e.g., Amsler et al. 1999). Diver observations at the site recorded in our field notes indicated that many, and on one transect, all, of the macroalgae observed were attached to urchins rather than the substratum. The vertical distribution of macroinvertebrates at site L also suggests the impacts of ice scour at shallow depths (Amsler et al. 2023). A similar difference between by-hand and percent cover patterns occurs at site M, which had the second highest cover of S. neumayeri.

We are aware of only few reports of the vertical distribution of red macroalgae anywhere along the northern WAP, and many specifically report only on a subset of the red macroalgal species presumably present with others lumped into one or more groups or not reported at all. The only quantitative reports deeper than 25 m are those of DeLaca and Lipps (1976) to 31 m at one site on Anvers Island (Figure 1), Brouwer et al. (1995) to 29 m at one site on Signy Island in the South Orkney Islands (Figure 1), Klöser et al. (1996) to approximately 35 m from 14 transects in Potter Cove on King George Island (Figure 1), and Valdivia et al. (2015) to 30 m at six sites in Fildes Bay on King George Island. Klöser et al. (1996) report the vertical distribution of most red macroalgae in species groups rather than individually. Valdivia et al. (2015) only report on one red macroalga in the main text but an additional 18 are included in supplementary material, including at least 12 of the species included here (they report “Delesseria sp.” at one site that could be Paraglossum salicifolium but only at 5–10 m depth, which in our personal experience from Anvers Island is more likely to have been P. amsleri). Otherwise, the only studies we are aware of that provide vertical distribution data for more than approximately five individual red macroalgal species are: 1) DeLaca and Lipps (1976), reporting 19 species of which 10 are reported on herein; 2) Amsler et al. (1995), also at Anvers Island, reporting 17 species of which 12 are included herein; and 3) Ko et al. (2020, mostly in Supplementary information 5) reporting 18 species from six sites in Maxwell Bay on King George Island, of which 12 species are included here. Ko et al. (2020) built on an earlier study at the same sites that reported general vertical distributions qualitatively (Chung et al. 1994).

We chose to only include red macroalgal species in this report that were collected from at least five sites, which as noted previously excluded an additional 13 red algal species reported by Amsler et al. (2023). Most of these 13 species are included in the other studies listed in the previous paragraph. We did not include them here because most were present in only one or two transects or depths in the central WAP sites (if found in the central WAP sites at all) and so are of limited utility in generalizing about vertical distributions. The by-hand collection data for these additional 13 red macroalgal species are available at the United States Antarctic Program Data Center as noted in the Data Accessibility Statement, below.

The vertical distributions of red macroalgal species we observed were usually similar across sites and were generally similar to the distributions observed in previous studies in the northern WAP. Plocamium sp. and Myriogramme manginii had consistently the widest vertical distributions at sites where they occurred. Both species were also reported across depths in previous Anvers Island reports (Amsler et al. 1995; DeLaca and Lipps 1976), as was reported for Plocamium sp. from four studies at King George Island (Klöser et al. 1996; Ko et al. 2020; Quartino et al. 2001; Valdivia et al. 2015) and one on Signy Island (Brouwer et al. 1995). M. mangini was also reported in species groups found across depths by Klöser et al. (1996) as well as, but only rarely, across depths as an individual species by Ko et al. (2020) and Valdivia et al. (2015). Previous reports of the most geographically widespread red macroalga in our study, Iridaea ‘cordata’, usually have it restricted to 5–10 m and shallower (Amsler et al. 1995; Brouwer et al. 1995; DeLaca and Lipps 1976; Klöser et al. 1996; Valdivia et al. 2015) but we observed it deeper (even down to 35 m) at six sites, although not in abundance. Ko et al. (2020) also found I. ‘cordata’ deeper than 10 m at three of their six King George Island sites.

Sarcopeltis antarctica (previously Gigartina skottsbergii, Hughey et al. 2020) and Trematocarpus antarcticus were commonly observed across depths. S. antarctica was more commonly collected shallower and T. antarcticus was sometimes more common in middle depths, both of which are consistent with most northern WAP reports (Amsler et al. 1995; DeLaca and Lipps 1976; Klöser et al. 1996; Ko et al. 2020; Valdivia et al. 2015). The species presented in Figure 5 were primarily observed in middle to deeper depths, which, where reported, are also consistent with records from the northern WAP (Amsler et al. 1995; Brouwer et al. 1995; DeLaca and Lipps 1976; Klöser et al. 1996; Ko et al. 2020; Valdivia et al. 2015).

To our knowledge, the present study provides the only species-level information available on the vertical distribution of central WAP macroalgae. Moe and DeLaca (1976) and Mystikou et al. (2014) provide species lists for 21 sites in the central WAP but no information on distribution by depth. Barnes and Brockington (2003) and Bowden (2005) provide limited data on macroalgal vertical distributions at Adelaide Island (Figure 1) but not by species. Although overall macroalgal cover is strongly, negatively correlated to annual sea ice cover (Amsler et al. 2023), which generally increases to the south (Figure 1), where present, most red macroalgal species’ vertical distributions in the central WAP are similar to those previously reported in the northern WAP. However, few of the species were observed south of site J (66.1°S). The brown macroalgal flora of the central WAP differs markedly from that of the northern WAP due to the absence of D. anceps but the vertical distributions of the other two major overstory macroalgae, D. menziesii and H. grandifolius are similar to the northern WAP even though their percent cover becomes much lower.

Decreases in sea ice cover predicted by the end of the twenty-first century are likely to greatly increase overall macroalgal cover in the central WAP (Amsler et al. 2023), and glacier retreat, also driven by climate change, is likely to allow macroalgae to expand into newly exposed benthos (Deregibus et al. 2023). Both have important implications not only with respect to expanding benthic food webs but also to understanding the potential for the WAP to contribute to blue carbon sequestration (Amsler et al. 2023; Deregibus et al. 2023; Iken et al. 2023; Lagger et al. 2018; Morley et al. 2022). Our results indicate that with the likely exception of D. anceps, the distribution of macroalgae across depths in these expanded, future communities should be similar to those in heretofore much more widely studied northern WAP communities. Consequently, current knowledge of the northern WAP should be applicable to predictions about food web structure and blue carbon sequestration in the future central WAP.


Corresponding author: Charles D. Amsler, Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA, E-mail:

Award Identifier / Grant number: ANT-1744550, ANT-1744570, ANT-1744584, ANT-1744602

About the authors

Charles D. Amsler

Charles D. Amsler is a Professor of Biology at the University of Alabama at Birmingham. He is a phycologist by background and much of his Antarctic research has focused on the chemical ecology of benthic organisms. He has also led or co-led projects examining the impacts of climate change on benthic communities including this one examining the impacts of declining sea ice. He has participated in 24 Antarctic expeditions since 1985–86, and has made over 1000 Antarctic research scuba dives.

Margaret O. Amsler

Margaret O. Amsler is a Researcher V at the University of Alabama at Birmingham. Her master’s degree centered on the Antarctic krill and lead to participation in twelve expeditions with emphasis on krill. The majority of her thirty-two plus expeditions focused on the benthos studying chemical ecology of benthic organisms, documenting the distribution and abundance of deep-sea crabs, examining the impacts of sea ice cover on benthic communities, and investigating the impacts of ocean acidification on macroalgae and benthic invertebrates.

Sabrina Heiser

Sabrina Heiser earned her doctor’s degree in biology in 2023 and is currently a postdoctoral researcher in Dr. Deana Erdner’s lab at the University of Texas at Austin Marine Science Institute. She is a benthic ecologist studying the population and chemical ecology of algae assemblages focusing on understanding community structure within ecosystems. She has worked from the tropics to the poles and studied chemical defense diversity in macroalgae as well as community composition of benthic microalgal communities.

Katrin Iken

Katrin Iken is a professor of Marine Biology with a research focus on benthic ecology, biodiversity, and food webs. She has worked extensively in both the Arctic and Southern oceans, ranging from SCUBA-diving based studies on macroalgae in coastal systems to ship-based operations for studying shelf and deep-sea systems.

Aaron W. E. Galloway

Aaron W. E. Galloway is an Associate Professor at the Oregon Institute of Marine Biology, the coastal marine lab of the University of Oregon. Dr. Galloway leads the Coastal Trophic Ecology Lab, which is generally focused on trophic inferences in marine benthic food webs, with an emphasis on algae-invertebrate interactions. To do this work, the group often uses fatty acids as trophic biomarkers, paired with underwater natural history, scuba diving, lab and field experimentation, and modeling.

Acknowledgments

We are grateful to Julie Schram, Ross Whippo, and Alex Lowe who contributed greatly to the fieldwork as well as to our other shipmates on the ARSV Laurence M. Gould (LMG). This included Captain Zsolt Esztergomi and his LMG crew and the Antarctic Support Contract LMG team of Sean Bercaw, Chuck Holloway, Linnah Neidel, Kevin Pedigo, Gina Pikton, and Rich Thompson. We are also grateful to Prof. Matthew Dring and two anonymous reviewers for comments on the original submission that substantially improved the final version.

  1. Research ethics: Not applicable.

  2. Author contributions: All authors except MOA and SH contributed to the conception and design of the project. All authors except JBM contributed to the fieldwork. MOA analyzed the percent cover data. CDA collated the by-hand collection data, prepared the data figures, and wrote the first draft of the article. All authors contributed to the final draft and approved the submitted version for publication.

  3. Competing interests: The authors declare no conflicts of interest regarding this article.

  4. Research funding: The project was funded by National Science Foundation awards ANT-1744550 (CDA, JBM), ANT-1744602 (KI), ANT-1744570 (AWEG), and ANT-1744584 (AGK) and from the Antarctic Organisms and Ecosystems Program.

  5. Data availability: Data from the overall project are available at the United States Antarctic Program Data Center (https://www.usap-dc.org/view/project/p0010104). These include by-hand collection data for all species included in the original study including those not presented here at https://doi.org/10.15784/601725 as well as the raw percent cover data from the video analysis, compiled from Coral Point Count with Excel extensions, at https://doi.org/10.15784/601619. All videos used for percent cover determination are available and can be requested through https://doi.org/10.15784/601610. Some clips are included in a video available at https://www.youtube.com/watch?v=fZ4XX3kZ1pA.

References

Amsler, C.D., Rowley, R.J., Laur, D.R., Quetin, L.B., and Ross, R.M. (1995). Vertical distribution of Antarctic Peninsular macroalgae: cover, biomass, and species composition. Phycologia 34: 424–430, https://doi.org/10.2216/i0031-8884-34-5-424.1.Search in Google Scholar

Amsler, C.D., McClintock, J.B., and Baker, B.J. (1999). An antarctic feeding triangle: defensive interactions between macroalgae, sea urchins, and sea anemones. Mar. Ecol. Prog. Ser. 183: 105–114, https://doi.org/10.3354/meps183105.Search in Google Scholar

Amsler, C.D., Amsler, M.O., Klein, A.G., Galloway, A.W.E., Iken, K., McClintock, J.B., Heiser, S., Lowe, A.T., Schram, J.B., and Whippo, R. (2023). Strong correlations of sea ice cover with macroalgal cover along the Antarctic Peninsula: ramifications for present and future benthic communities. Elem. Sci. Anth. 11: 00020, https://doi.org/10.1525/elementa.2023.00020.Search in Google Scholar

Barnes, D.K.A. and Brockington, S. (2003). Zoobenthic biodiversity, biomass and abundance at Adelaide Island, Antarctica. Mar. Ecol. Prog. Ser. 249: 145–155, https://doi.org/10.3354/meps249145.Search in Google Scholar

Bowden, D.A. (2005). Quantitative characterization of shallow marine benthic assemblages at Ryder Bay, Adelaide Island, Antarctica. Mar. Biol. 146: 1235–1249, https://doi.org/10.1007/s00227-004-1526-0.Search in Google Scholar

Brouwer, P.E.M., Geilen, E.F.M., Gremmen, N.J.M., and van Lent, F. (1995). Biomass, cover and zonation pattern of sublittoral macroalgae at Signy Island, South Orkeny Islands, Antarctica. Bot. Mar. 38: 259–270, https://doi.org/10.1515/botm.1995.38.1-6.259.Search in Google Scholar

Chung, H., Oh, Y.S., Lee, I.K., and Kim, D.-Y. (1994). Macroalgal vegetation of Maxwell Bay in King George Island, Antarctica. Korean J. Phycol. 9: 47–58.Search in Google Scholar

Dedrick, K.R., Partington, K., Van Woert, M., Bertoia, C.A., and Benner, D. (2001). U.S. National/Naval Ice Center digital sea ice data and climatology. Can. J. Rem. Sens. 27: 457–475, https://doi.org/10.1080/07038992.2001.10854887.Search in Google Scholar

DeLaca, T.E. and Lipps, J.H. (1976). Shallow water marine associations, Antarctic Peninsula. Antarct. J. U. S. 11: 12–20.Search in Google Scholar

Deregibus, D., Campana, G.L., Neder, C., Barnes, D.K.A., Zacher, K., Piscicelli, J.M., Jerosch, K., and Quartino, M.L. (2023). Potential macroalgal expansion and blue carbon gains with northern Antarctic Peninsula glacial retreat. Mar. Environ. Res. 189: 106056, https://doi.org/10.1016/j.marenvres.2023.106056.Search in Google Scholar PubMed

Dubrasquet, H., Reyes, J., Sanchez, R.P., Valdivia, N., and Guillemin, M.-L. (2018). Molecular-assisted revision of red macroalgal diversity and distribution along the Western Antarctic Peninsula and South Shetland Islands. Cryptogam. Algol. 39: 409–429, https://doi.org/10.7872/crya/v39.iss4.2018.409.Search in Google Scholar

Fetterer, F. (2006). A selection of documentation related to National Ice Center Sea Ice Charts in Digitial Format. National Snow and Ice Center Special Report #13, Available at: <https://nsidc.org/sites/nsidc.org/files/technical-references/nsidc_special_report_13.pdf> (Accessed 24 August 2023).Search in Google Scholar

Guiry, M.D. and Guiry, G.M. (2023). AlgaeBase. World-wide electronic publication, Available at: <http://www.algaebase.org> (Accessed 26 October 2023).Search in Google Scholar

Heiser, S., Shilling, A.J., Amsler, C.D., McClintock, J.B., and Baker, B.J. (2023). To change or not to change: drivers of defensive secondary metabolite distribution in the red macroalga Plocamium sp. Mar. Biol. 170: 31, https://doi.org/10.1007/s00227-023-04173-9.Search in Google Scholar

Hommersand, M.H., Moe, R.L., Amsler, C.D., and Fredericq, S. (2009). Notes on the systematics and biogeographical relationships of Antarctic and Sub-Antarctic Rhodophyta with descriptions of four new genera and five new species. Bot. Mar. 52: 509–534, https://doi.org/10.1515/bot.2009.081.Search in Google Scholar

Hughey, J.R., Leister, G.L., Gabrielson, P.W., and Hommersand, M.H. (2020). Sarcopeltis gen. nov. (Gigartinaceae, Rhodophyta), with S. skottsbergii comb. nov. from southern South America and S. antarctica sp. nov. from the Antarctic Peninsula. Phytotaxa 468: 75–88, https://doi.org/10.11646/phytotaxa.468.1.4.Search in Google Scholar

Iken, K., Amsler, C.D., Gorman, K.B., Klein, A.G., Galloway, A.W.E., Amsler, M.O., Heiser, S., Whippo, R., Lowe, A.T., Schram, J.B., et al.. (2023). Macroalgal input into the coastal food web along a gradient of seasonal sea ice cover along the Western Antarctic Peninsula. Mar. Ecol. Prog. Ser. 718: 1–22, https://doi.org/10.3354/meps14388.Search in Google Scholar

Klöser, H., Mercuri, G., Laturnus, F., Quartino, M.L., and Wiencke, C. (1994). On the competitive balance of macroalgae at Potter Cove (King George Island, South Shetlands). Polar Biol. 14: 11–16, https://doi.org/10.1007/bf00240266.Search in Google Scholar

Klöser, H., Quartino, M.L., and Wiencke, C. (1996). Distribution of macroalgae and macroalgal communities in gradients of physical conditions in Potter Cove, King George Island, Antarctica. Hydrobiologia 333: 1–17, https://doi.org/10.1007/bf00020959.Search in Google Scholar

Ko, Y.W., Choi, H.-G., Lee, D.S., and Kim, J.H. (2020). 30 years revisit survey for long-term changes in the Antarctic subtidal algal assemblage. Sci. Rep. 10: 8481, https://doi.org/10.1038/s41598-020-65039-4.Search in Google Scholar PubMed PubMed Central

Kohler, K.E. and Gill, S.M. (2006). Coral Point Count with Excel extensions (CPCe): a visual basic program for the determination of coral and substrate coverage using random point count methodology. Comput. Geosci. 32: 1259–1269, https://doi.org/10.1016/j.cageo.2005.11.009.Search in Google Scholar

Lagger, C., Nime, M., Torre, L., Servetto, N., Tatián, M., and Sahade, R. (2018). Climate change, glacier retreat and a new ice-free island offer new insights on Antarctic benthic responses. Ecography 41: 579–591, https://doi.org/10.1111/ecog.03018.Search in Google Scholar

Matula, C.V., Quartino, M.L., Nuñez, J.D., Zacher, K., and Bartsch, I. (2022). Effects of seawater temperature and seasonal irradiance on growth, reproduction, and survival of the endemic Antarctic brown alga Desmarestia menziesii (Phaeophyceae). Polar Biol. 45: 559–572, https://doi.org/10.1007/s00300-021-02991-5.Search in Google Scholar

Moe, R.L. and DeLaca, T.E. (1976). Occurrence of macroscopic algae along the Antarctic Peninsula. Antarct. J. U. S. 11: 20–24.Search in Google Scholar

Morley, S.A., Souster, T.A., Vause, B.J., Gerrish, L., Peck, L.S., and Barnes, D.K.A. (2022). Benthic biodiversity, carbon storage and the potential for increasing negative feedbacks on climate change in shallow waters of the Antarctic Peninsula. Biology 11: 320, https://doi.org/10.3390/biology11020320.Search in Google Scholar PubMed PubMed Central

Mystikou, A., Peters, A., Asensi, A., Fletcher, K., Brickle, P., van West, P., Convey, P., and Küpper, F. (2014). Seaweed biodiversity in the South-Western Antarctic Peninsula: surveying macroalgal community composition in the Adelaide Island/Marguerite Bay region over a 35-year time span. Polar Biol. 37: 1607–1619, https://doi.org/10.1007/s00300-014-1547-1.Search in Google Scholar

Ocaranza-Barrera, P., González-Wevar, C.A., Guillemin, M.-L., Rosenfeld, S., and Mansilla, A. (2019). Molecular divergence between Iridaea cordata (Turner) Bory de Saint-Vincent from the Antarctic Peninsula and the Magellan region. J. Appl. Phycol. 31: 939–949, https://doi.org/10.1007/s10811-018-1656-2.Search in Google Scholar

Oliveira, M.C., Pellizzari, F., Medeiros, A.S., and Yokoya, N.S. (2020). Diversity of Antarctic seaweeds. In: Gómez, I. and Huovinen, P. (Eds.), Antarctic seaweeds: diversity, adaptation and ecosystem services. Springer International Publishing, Cham, pp. 23–42.10.1007/978-3-030-39448-6_2Search in Google Scholar

Pellizzari, F., Silva, M.C., Silva, E.M., Medeiros, A., Oliveira, M.C., Yokoya, N.S., Pupo, D., Rosa, L.H., and Colepicolo, P. (2017). Diversity and spatial distribution of seaweeds in the South Shetland Islands, Antarctica: an updated database for environmental monitoring under climate change scenarios. Polar Biol. 40: 1671–1685, https://doi.org/10.1007/s00300-017-2092-5.Search in Google Scholar

Pellizzari, F., De Mello, J.P.D.S., Santos-Silva, M.C., Osaki, V.S., Brandini, F.P., Convey, P., and Henrique Rosa, L. (2023). New records and updated distributional patterns of macroalgae from the South Shetland Islands and northern Weddell Sea, Antarctica. Antarct. Sci. 35: 243–255, https://doi.org/10.1017/s095410202300010x.Search in Google Scholar

Quartino, M.L., Klöser, H., Schloss, I.R., and Wiencke, C. (2001). Biomass and associations of benthic marine macroalgae from the inner Potter Cove (King George Island, Antarctica) related to depth and substrate. Polar Biol. 24: 349–355, https://doi.org/10.1007/s003000000218.Search in Google Scholar

Rozema, P.D., Venables, H.J., van de Poll, W.H., Clarke, A., Meredith, M.P., and Buma, A.G.J. (2017). Interannual variability in phytoplankton biomass and species composition in northern Marguerite Bay (West Antarctic Peninsula) is governed by both winter sea ice cover and summer stratification. Limnol. Oceanogr. 62: 235–252, https://doi.org/10.1002/lno.10391.Search in Google Scholar

Valdivia, N., Díaz, M.J., Garrido, I., and Gómez, I. (2015). Consistent richness-biomass relationship across environmental gradients in a marine macroalgal-dominated subtidal community on the Western Antarctic Peninsula. PLoS One 10: e0138582, https://doi.org/10.1371/journal.pone.0138582.Search in Google Scholar PubMed PubMed Central

Venables, H., Meredith, M.P., Hendry, K.R., ten Hoopen, P., Peat, H., Chapman, A., Beaumont, J., Piper, R., Miller, A.J., Mann, P., et al.. (2023). Sustained year-round oceanographic measurements from Rothera Research Station, Antarctica, 1997–2017. Sci. Data 10: 265, https://doi.org/10.1038/s41597-023-02172-5.Search in Google Scholar PubMed PubMed Central

Wiencke, C. and Amsler, C.D. (2012). Seaweeds and their communities in polar regions. In: Wiencke, C., and Bischof, K. (Eds.), Seaweed biology: novel insights into ecophysiology, ecology and utilization. Springer-Verlag, Berlin, pp. 265–294.10.1007/978-3-642-28451-9_13Search in Google Scholar

Wiencke, C. and Clayton, M.N. (1990). Sexual reproduction, life history, and early development in culture of the Antarctic brown alga Himantothallus grandifolius (Desmarestiales, Phaeophyceae). Phycologia 29: 9–18, https://doi.org/10.2216/i0031-8884-29-1-9.1.Search in Google Scholar

Wiencke, C. and Clayton, M.N. (2002). Antarctic seaweeds. Synopsis of the Antarctic benthos, Vol. 9. ARG Gantner Verlag KG, Ruggell, Liechtenstein.Search in Google Scholar

Wiencke, C., Stolpe, U., and Lehmann, H. (1991). Morphogenesis of the brown alga Desmarestia antarctica cultivated under seasonally fluctuating antarctic daylengths. Ser. Sci. INACH 41: 65–78.Search in Google Scholar

Wiencke, C., Clayton, M.N., and Schulz, D. (1995). Life history, reproductive morphology and development of the Antarctic brown alga Desmarestia menziesii J. Agardh. Bot. Acta 108: 201–208, https://doi.org/10.1111/j.1438-8677.1995.tb00851.x.Search in Google Scholar

Wiencke, C., Clayton, M.N., and Langreder, C. (1996). Life history and seasonal morphogenesis of the endemic Antarctic brown alga Desmarestia anceps Montagne. Bot. Mar. 39: 435–444, https://doi.org/10.1515/botm.1996.39.1-6.435.Search in Google Scholar

Wiencke, C., Amsler, C.D., and Clayton, M.N. (2014). Macroalgae. In: De Broyer, C., Koubbi, P., Griffiths, H.J., Raymond, B., d’Udekem d’Acoz, C., Van de Putte, A.P., Danis, B., David, B., Grant, S., Gutt, J., et al.. (Eds.). Biogeographic atlas of the Southern Ocean. Scientific Committee on Antarctic Research, Cambridge, UK, pp. 66–73.Search in Google Scholar

Received: 2023-09-18
Accepted: 2023-11-10
Published Online: 2023-11-30
Published in Print: 2024-02-26

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