scholarly journals Intermediate ice scour disturbance is key to maintaining a peak in biodiversity within the shallows of the Western Antarctic Peninsula

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
B. J. O. Robinson ◽  
D. K. A. Barnes ◽  
L. J. Grange ◽  
S. A. Morley
Keyword(s):  
Antarctic Peninsula ◽  
Intermediate Disturbance Hypothesis ◽  
Trophic Levels ◽  
Depth Range ◽  
Western Antarctic Peninsula ◽  
Diverse Range ◽  
Spatial And Temporal Scales ◽  
Intermediate Disturbance ◽  
Antarctic Benthos ◽  
The Antarctic

AbstractClimate-related disturbance regimes are changing rapidly with profound consequences for ecosystems. Disturbance is often perceived as detrimental to biodiversity; however, the literature is divided on how they influence each other. Disturbance events in nature are diverse, occurring across numerous interacting trophic levels and multiple spatial and temporal scales, leading to divergence between empirical and theoretical studies. The shallow Antarctic seafloor has one of the largest disturbance gradients on earth, due to iceberg scouring. Scour rates are changing rapidly along the Western Antarctic Peninsula because of climate change and with further changes predicted, the Antarctic benthos will likely undergo dramatic shifts in diversity. We investigated benthic macro and megafaunal richness across 10–100 m depth range, much of which, 40–100 m, has rarely been sampled. Macro and megafauna species richness peaked at 50–60 m depth, a depth dominated by a diverse range of sessile suspension feeders, with an intermediate level of iceberg disturbance. Our results show that a broad range of disturbance values are required to detect the predicted peak in biodiversity that is consistent with the Intermediate Disturbance Hypothesis, suggesting ice scour is key to maintaining high biodiversity in Antarctica’s shallows.

scholarly journals No barrier to emergence of bathyal king crabs on the Antarctic shelf

2015 ◽  
Vol 112 (42) ◽  
pp. 12997-13002 ◽  
Author(s):  
Richard B. Aronson ◽  
Kathryn E. Smith ◽  
Stephanie C. Vos ◽  
James B. McClintock ◽  
Margaret O. Amsler ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Cold Water ◽  
Austral Summer ◽  
Outer Shelf ◽  
Depth Range ◽  
Western Antarctic Peninsula ◽  
Near Surface ◽  
Viable Population ◽  
Gravid Females ◽  
The Antarctic

Cold-water conditions have excluded durophagous (skeleton-breaking) predators from the Antarctic seafloor for millions of years. Rapidly warming seas off the western Antarctic Peninsula could now facilitate their return to the continental shelf, with profound consequences for the endemic fauna. Among the likely first arrivals are king crabs (Lithodidae), which were discovered recently on the adjacent continental slope. During the austral summer of 2010‒2011, we used underwater imagery to survey a slope-dwelling population of the lithodid Paralomis birsteini off Marguerite Bay, western Antarctic Peninsula for environmental or trophic impediments to shoreward expansion. The population density averaged ∼4.5 individuals × 1,000 m−2 within a depth range of 1,100‒1,500 m (overall observed depth range 841–2,266 m). Images of juveniles, discarded molts, and precopulatory behavior, as well as gravid females in a trapping study, suggested a reproductively viable population on the slope. At the time of the survey, there was no thermal barrier to prevent the lithodids from expanding upward and emerging on the outer shelf (400- to 550-m depth); however, near-surface temperatures remained too cold for them to survive in inner-shelf and coastal environments (<200 m). Ambient salinity, composition of the substrate, and the depth distribution of potential predators likewise indicated no barriers to expansion of lithodids onto the outer shelf. Primary food resources for lithodids—echinoderms and mollusks—were abundant on the upper slope (550–800 m) and outer shelf. As sea temperatures continue to rise, lithodids will likely play an increasingly important role in the trophic structure of subtidal communities closer to shore.

scholarly journals Every Rule Has an Exception: a Cheater in the Community-Wide Mutualism in Antarctic Seaweed Forests

2020 ◽  
Vol 60 (6) ◽  
pp. 1358-1368
Author(s):  
Sabrina Heiser ◽  
Charles D Amsler ◽  
James B McClintock ◽  
Andrew J Shilling ◽  
Bill J Baker
Keyword(s):  
Primary Production ◽  
Antarctic Peninsula ◽  
Ecosystem Engineers ◽  
Chemical Defenses ◽  
Western Antarctic Peninsula ◽  
Macroalgal Species ◽  
Antarctic Ecosystem ◽  
Ecological Roles ◽  
The Antarctic ◽  
Plocamium Cartilagineum

Synopsis Dense macroalgal forests on the Western Antarctic Peninsula serve important ecological roles both in terms of considerable biomass for primary production as well as in being ecosystem engineers. Their function within the Antarctic ecosystem has been described as a crucial member of a community-wide mutualism which benefits macroalgal species and dense assemblages of associated amphipod grazers. However, there is a cheater within the system that can feed on one of the most highly chemically defended macroalgal hosts. The amphipod Paradexamine fissicauda has been found to readily consume the finely branched red macroalga Plocamium cartilagineum. This amphipod grazer not only feeds on its host, but also appears to sequester its host’s chemical defenses for its own utilization. This review summarizes what we know about both of these exceptions to the community-wide mutualism.

An evaluation of sponge-associated amphipods from the Antarctic Peninsula

2009 ◽  
Vol 21 (6) ◽  
pp. 579-589 ◽  
Author(s):  
Margaret O. Amsler ◽  
James B. Mcclintock ◽  
Charles D. Amsler ◽  
Robert A. Angus ◽  
Bill J. Baker
Keyword(s):  
Antarctic Peninsula ◽  
Energy Flow ◽  
Benthic Communities ◽  
Diversity Indices ◽  
Amphipod Species ◽  
Western Antarctic Peninsula ◽  
Gut Content ◽  
Algal Communities ◽  
Host Relationships ◽  
The Antarctic

AbstractNearshore marine benthic algal communities along the western Antarctic Peninsula harbour extremely high densities of amphipods that probably play important roles in nutrient and energy flow. This study extends our evaluation of the importance of amphipods in the nearshore Antarctic Peninsular benthic communities and focuses on sponge associations. We found a mean density of 542 amphipods per litre (L) sponge for twelve species of ecologically dominant sponges. The highest mean density (1295 amphipods per L sponge) occurred withDendrilla membranosaPallas. The amphipod community associated with the 12 sponges was diverse (38 species), with mean species richness values ranging from two to eight species. Mean Shannon diversity indices (H’) ranged from 0.52 to 1.49. Amphipods did not appear to have obligate host relationships. Qualitative gut content analyses indicated that 12 of the 38 amphipod species were found with sponge spicules in their guts. However, only one of the amphipods,Echiniphimedia hodgsoniWalker, had considerable amounts of spicules in the gut. Organic lipophilic and hydrophilic extracts of the twelve sponges were presented in alginate food disks to a sympatric omnivorous amphipod in feeding bioassays and extracts of only two sponges deterred feeding.

The abundance and distribution of echinoderms in nearshore hard-bottom habitats near Anvers Island, western Antarctic Peninsula

2012 ◽  
Vol 24 (6) ◽  
pp. 554-560 ◽  
Author(s):  
Brittny A. White ◽  
James McClintock ◽  
Charles D. Amsler ◽  
Christopher L. Mah ◽  
Margaret O. Amsler ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Positive Relationship ◽  
Western Antarctic Peninsula ◽  
Benthic Production ◽  
Odontaster Validus ◽  
Sterechinus Neumayeri ◽  
Significant Relationships ◽  
Inherent Vulnerability ◽  
Abundance And Distribution ◽  
The Antarctic

AbstractEchinoderms are well represented in nearshore hard-bottom (< 100 m depth) habitats along the Antarctic Peninsula where they are presumably important contributors to benthic production, carbon flow, and determinants of community structure. The present study assesses the densities of echinoderms at shallow depths (2–15 m) at five sampling sites within three kilometres of Anvers Island on the central western Antarctic Peninsula. The asteroids Odontaster validus, Granaster nutrix, Lysasterias perrieri and Adelasterias papillosa, two ophiuroids in the Amphiuridae, the holothuroids Psolicrux coatsi and Psolus carolineae and one representative of the Cucumaridae, and the regular echinoid Sterechinus neumayeri were enumerated. Mean total echinoderm densities were high (34.9 individuals m-2) and ranged from 21.9 individuals m-2 for asteroids to 2.7 individuals m-2 for holothuroids. With the exception of a positive relationship between the abundance of the regular echinoid Sterechinus neumayeri and the biomass of the brown alga Himanthothallus grandifolius, no significant relationships were found between the abundance of asteroids, ophiuroids, or holothuroids and two species of brown algae or three algal ecotypes. The present study indicates nearshore hard-bottom echinoderms are important in the carbon cycle and their inherent vulnerability to ocean acidification may have community-level impacts.

Morphology of Australoneis gen. nov. and A. frenguelliae comb. nov. (Achnanthales, Bacillariophyta) from the Antarctic Peninsula

Phytotaxa ◽  
2021 ◽  
Vol 513 (2) ◽  
pp. 81-98
Author(s):  
JOSÉ M. GUERRERO ◽  
CATHERINE RIAUX-GOBIN ◽  
JUAN I. DEBANDI ◽  
KATHARINA ZACHER ◽  
MARIA LILIANA QUARTINO ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Antarctic Peninsula ◽  
New Genus ◽  
Light And Electron Microscopy ◽  
Benthic Diatoms ◽  
Western Antarctic Peninsula ◽  
Potter Cove ◽  
The Antarctic

Based on marine benthic diatoms collected at Potter Cove (Western Antarctic Peninsula), we present a detailed study, using both light and electron microscopy, of the morphology of Campyloneis frenguelliae, a species recently transferred from Cocconeis. Ultrastructural observations revealed a combination of new and unusual features within the Achnanthales: a raphe valve with different areolation patterns, a hollow valvocopula with no apparent fimbriae, and a sternum valve externally ornamented by an embossed structure, areolae occluded by hymenes mostly supported by one short peg, and multiple marginal pores that open internally into shallow valve depressions. In view of these unique set of features, we describe Australoneis gen. nov. to include Australoneis frenguelliae comb. nov. and designate a sample from Potter Cove as epitype of the latter. The main characteristics of the new genus are compared to those of its closely allied Cocconeis, Campyloneis, Xenococconeis and Amphicocconeis.

Shifts in microphytoplankton species and cell size at Admiralty Bay, Antarctica

2014 ◽  
Vol 27 (3) ◽  
pp. 225-239 ◽  
Author(s):  
Priscila Kienteca Lange ◽  
Denise Rivera Tenenbaum ◽  
Virgínia Maria Tavano ◽  
Rodolfo Paranhos ◽  
Lucia De Siqueira Campos
Keyword(s):  
Cell Size ◽  
Remote Sensing Data ◽  
Coastal Areas ◽  
Trophic Levels ◽  
Ice Formation ◽  
Western Antarctic Peninsula ◽  
Admiralty Bay ◽  
Planktonic Diatoms ◽  
The Antarctic

AbstractPhytoplankton (>15 µm) was investigated in three shallow coastal areas at Admiralty Bay (AB) between the summers of 2002–03 and 2008–09. Phytoplankton abundance was low (103 cells l-1) and, over time, the prevailing cell size decreased due to a shift in phytoplankton dominant species from diatoms to dinoflagellates. In situ and remote sensing data showed that oscillations in sea surface temperature, precipitation, ice formation/melting, irradiance (cloud cover) and bottom circulation (indexed by the Antarctic Oscillation Index; AAO) were shown to govern the structure of the phytoplankton. Under negative AAO, diatoms prevailed, with the dominance of large (>80 µm) benthic diatoms (e.g. Corethron pennatum and Navicula directa) in periods of low production (102 cells l-1 in 2002–03), and medium-sized (31–80 µm) centrics (e.g. Thalassiosira spp. and Stellarima microtrias) when the abundance was higher (104 cells l-1 in 2003–04). Conversely, positive AAO led to the co-dominance of dinoflagellates and planktonic diatoms (e.g. Pseudo-nitzschia spp.) in the summers of 2007–08 and 2008–09. These results suggest that the AAO can be a good predictor of phytoplankton in coastal areas around the western Antarctic Peninsula, and may help our understanding of changes in other trophic levels of the food web.

scholarly journals Climate change and the marine ecosystem of the western Antarctic Peninsula

2006 ◽  
Vol 362 (1477) ◽  
pp. 149-166 ◽  
Author(s):  
Andrew Clarke ◽  
Eugene J Murphy ◽  
Michael P Meredith ◽  
John C King ◽  
Lloyd S Peck ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Food Web ◽  
Antarctic Peninsula ◽  
Sublethal Effects ◽  
Marine Ecosystem ◽  
Ecological Interactions ◽  
Western Antarctic Peninsula ◽  
Ice Dynamics ◽  
The Antarctic

The Antarctic Peninsula is experiencing one of the fastest rates of regional climate change on Earth, resulting in the collapse of ice shelves, the retreat of glaciers and the exposure of new terrestrial habitat. In the nearby oceanic system, winter sea ice in the Bellingshausen and Amundsen seas has decreased in extent by 10% per decade, and shortened in seasonal duration. Surface waters have warmed by more than 1 K since the 1950s, and the Circumpolar Deep Water (CDW) of the Antarctic Circumpolar Current has also warmed. Of the changes observed in the marine ecosystem of the western Antarctic Peninsula (WAP) region to date, alterations in winter sea ice dynamics are the most likely to have had a direct impact on the marine fauna, principally through shifts in the extent and timing of habitat for ice-associated biota. Warming of seawater at depths below ca 100 m has yet to reach the levels that are biologically significant. Continued warming, or a change in the frequency of the flooding of CDW onto the WAP continental shelf may, however, induce sublethal effects that influence ecological interactions and hence food-web operation. The best evidence for recent changes in the ecosystem may come from organisms which record aspects of their population dynamics in their skeleton (such as molluscs or brachiopods) or where ecological interactions are preserved (such as in encrusting biota of hard substrata). In addition, a southwards shift of marine isotherms may induce a parallel migration of some taxa similar to that observed on land. The complexity of the Southern Ocean food web and the nonlinear nature of many interactions mean that predictions based on short-term studies of a small number of species are likely to be misleading.

scholarly journals Transport of warm Upper Circumpolar Deep Water onto the western Antarctic Peninsula continental shelf

Ocean Science ◽  
2012 ◽  
Vol 8 (4) ◽  
pp. 433-442 ◽  
Author(s):  
D. G. Martinson ◽  
D. C. McKee
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Deep Water ◽  
Antarctic Circumpolar Current ◽  
Western Antarctic Peninsula ◽  
Dominant Mechanism ◽  
Circumpolar Deep Water ◽  
Marguerite Bay ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. Five thermistor moorings were placed on the continental shelf of the western Antarctic Peninsula (between 2007 and 2010) in an effort to identify the mechanism(s) responsible for delivering warm Upper Circumpolar Deep Water (UCDW) onto the broad continental shelf from the Antarctic Circumpolar Current (ACC) flowing over the adjacent continental slope. Historically, four mechanisms have been suggested: (1) eddies shed from the ACC, (2) flow into the cross-shelf-cutting canyons with overflow onto the nominal shelf, (3) general upwelling, and (4) episodic advective diversions of the ACC onto the shelf. The mooring array showed that for the years of deployment, the dominant mechanism is eddies; upwelling may also contribute but to an unknown extent. Mechanism 2 played no role, though the canyons have been shown previously to channel UCDW across the shelf into Marguerite Bay. Mechanism 4 played no role independently, though eddies may be advected within a greater intrusion of the background flow.

Climate Variability and Ecological Response of the Marine Ecosystem in the Western Antarctic Peninsula (WAP) Region

2003 ◽  
Author(s):  
Raymond C. Smith ◽  
William R. Fraser
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Antarctic Peninsula ◽  
Marine Ecosystem ◽  
Western Antarctic Peninsula ◽  
Sea Ice Extent ◽  
Half Century ◽  
Air Temperatures ◽  
Temperature Records ◽  
The Antarctic

The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula (WAP) region, which is the location of the Palmer LTER (figure 9.1), provide the opportunity to observe how climate-driven variability in the physical environment is related to changes in the marine ecosystem (Ross et al. 1996; Smith et al. 1996; Smith et al. 1999). This is a sea ice–dominated ecosystem where the annual advance and retreat of the sea ice is a major physical determinant of spatial and temporal change in its structure and function, from total annual primary production to the breeding success and survival of seabirds. Mounting evidence suggests that the earth is experiencing a period of rapid climate change, and air temperature records from the last half century confirm a statistically significant warming trend within the WAP during the past half century (King 1994; King and Harangozo 1998; Marshall and King 1998; Ross et al. 1996; Sansom 1989; Smith et al. 1996; Stark 1994; van den Broeke 1998; Weatherly et al. 1991). Air temperature–sea ice linkages appear to be very strong in the WAP region (Jacka 1990; Jacka and Budd 1991; King 1994; Smith et al. 1996; Weatherly et al. 1991), and a statistically significant anticorrelation between air temperatures and sea ice extent has been observed for this region. Consistent with this strong coupling, sea ice extent in the WAP area has trended down during this period of satellite observations, and the sea ice season has shortened. In addition, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests possible linkages among sea ice, cyclonic activity, and global teleconnections.

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