Primary producers: field observations

Bank-forming moss species on Signy Island (60°S) have expanded over the last 50 years (Cannone et al. Reference Cannone, Dalle Fratte, Convey, Worland and Guglielmin2017), while colonization following glacial retreat on Livingston Island (62°S) has been surprisingly slow, with only 0.04 ha of land showing signs of new vegetation cover since 1956 (Ruiz-Fernandez et al. Reference Ruiz-Fernandez, Oliva and Garcia-Hernandez2017). Lichen assemblages in deglaciated areas of King George Island show loss of some species due to desiccation, while pioneer species have emerged on the youngest moraines (Olech & Slaby Reference Olech and Slaby2016, Rodriguez et al. Reference Rodriguez, Passo and Chiapella2018). No changes in lichen abundance and diversity were found in Dronning Maud Land (73°S) between 1991 and 2002 (Johansson & Thor Reference Johansson and Thor2008), nor at Cape Hallett (72°S) between 1961 and 2018 (Colesie et al. Reference Colesie, Pan, Cary, Gemal, Brabyn and Kim2022), indicating that current levels of regional change have been insufficient to affect the cover of lichen communities. Vegetation monitoring in Victoria Land (73–75°S) since 2000 suggests that permafrost warming has supported the expansion of moss communities with sufficient water supply, while lichen communities expand at drier micro-sites (Guglielmin et al. Reference Guglielmin, Fratte and Cannone2014). Colder and drier summers have caused declines in moss health in the East Antarctica Antarctic Conservation Biogeographic Region (ACBR; Robinson et al. Reference Robinson, King, Bramley-Alves, Waterman, Ashcroft and Wasley2018).

Local distribution expansions of the native Antarctic vascular plant species Colobanthus quitensis (Kunth.) and Deschampsia antarctica (Desv.), and changes in their reproductive output, have been reported at various locations in the Maritime Antarctic (Fowbert & Smith Reference Fowbert and Smith1994, Smith Reference Smith1994, Convey Reference Convey1996, Grobe et al. Reference Grobe, Ruhland and Day1997, Torres-Mellado et al. Reference Torres-Mellado, Jana and Casanova-Katny2011, Cannone et al. Reference Cannone, Guglielmin, Convey, Worland and Favero Longo2016, Reference Cannone, Malfasi, Favero-Longo, Convey and Guglielmin2022). In the Argentine Islands, there is a suggestion that the rapid expansion documented between the 1960s and mid-1990s (Fowbert & Smith Reference Fowbert and Smith1994) subsequently plateaued (Parnikoza et al. Reference Parnikoza, Convey, Dykyyz, Trokhymets, Milinevsky and Tyschenko2009), consistent with the temporary cessation of the regional mean air temperature warming trend documented for the western Antarctic Peninsula region since the late 1990s (Turner et al. Reference Turner, Lu, White, King, Phillips and Hosking2016). Similar temperature- and moisture-driven vascular plant responses have been reported from sub-Antarctic islands (Chown & Smith Reference Chown and Smith1993, Frenot et al. Reference Frenot, Gloaguen, Picot, Bougere and Benjamin1993, Bergstrom et al. Reference Bergstrom, Turner, Scott, Copson and Shaw2006, le Roux & McGeoch Reference le Roux and McGeoch2008, Robin et al. Reference Robin, Chapuis and Lebouvier2011, van der Merwe et al. Reference van der Merwe, Greve, Hoffman, Skowno, Pallett and Terauds2024). There are no known field observations of increased terrestrial algal growth over time.

Primary producers: environmental gradients

There are consistent species richness declines across latitudinal gradients in Antarctica (Peat et al. Reference Peat, Clarke and Convey2007, Green et al. Reference Green, Sancho, Pintado and Schroeter2011) that also correlate with physiological activity patterns (Sancho et al. Reference Sancho, Pintado and Green2019, Shelyakin et al. Reference Shelyakin, Zakhozhiy and Golovko2020, Beltrán-Sanz et al. Reference Beltrán-Sanz, Raggio, Gonzalez, Dal Grande, Prost and Green2022). However, physiological work on isolated lichen photo- and mycobionts suggests that responses to warming may vary widely between species depending on their acclimation ability and due to the fact that species with a broad ecological amplitude may be favoured (Colesie et al. Reference Colesie, Budel, Hurry and Green2018, Marín et al. Reference Marín, Barták, Palfner, Vergara-Barros, Fernandoy, Hájek and Casanova-Katny2022).

A comparison of vegetation types along elevation gradients on Marion Island indicates that warming-induced changes will probably be mediated by water availability (Smith et al. Reference Smith, Steenkamp and Gremmen2001). Notably, there were no abundance differences of D. antarctica or C. quitensis along a 147 m elevation gradient on Livingston Island (Vera Reference Vera2011). Local elevation studies have also shown clear species differentiation of crustose lichen communities in the McMurdo Dry Valleys, indicating species niche differences and, hence, scope for climate change impacts (Wagner et al. Reference Wagner, Bathke, Cary, Green, Junker, Trutschnig and Ruprecht2020). Reconstruction of lichen growth rates also indicates a match between radial growth and glacier retreat on South Georgia (Roberts et al. Reference Roberts, Hodgson, Shelley, Royles, Griffiths, Deen and Thorne2010).

Primary producers: experimental studies

Moss and algae rapidly covered entire experimental plots within 1–3 years of treatment with completely enclosed cloches on Signy Island (Kennedy Reference Kennedy1996), while the response in OTCs was limited following 10 year field experimental manipulations (Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2016). However, moss cover expanded and gametangia production increased after only 2–6 years of treatment with OTCs on Fildes Peninsula (King George Island; Casanova-Katny et al. Reference Casanova-Katny, Torres-Mellado and Eppley2016, Shortlidge et al. Reference Shortlidge, Eppley, Kohler, Rosenstiel, Zuniga and Casanova-Katny2017, Prather et al. Reference Prather, Casanova-Katny, Clements, Chmielewski, Balkan and Shortlidge2019). Lichen photosynthetic capabilities appear diminished within OTCs due to increased desiccation (another micro-environmental consequence of OTCs; Casanova-Katny et al. Reference Casanova-Katny, Barták and Gutierrez2019). Lichen community responses to experimental warming also appear to be highly species-specific (Bokhorst et al. Reference Bokhorst, Huiskes, Convey and Aerts2007b, Reference Bokhorst, Convey, Huiskes and Aerts2016), in line with species ecophysiological characteristics (Colesie et al. Reference Colesie, Budel, Hurry and Green2018, Marín et al. Reference Marín, Barták, Palfner, Vergara-Barros, Fernandoy, Hájek and Casanova-Katny2022). Field and laboratory incubations of Antarctic soils under increased temperature show accelerated growth of algae, mosses and microbial soil crusts (Kennedy Reference Kennedy1996, Wynn-Williams Reference Wynn-Williams1996, Teoh et al. Reference Teoh, Chu, Marchant and Phang2004, Wong et al. Reference Wong, Teoh, Phang, Lim and Beardall2015), indicating that there is scope for increased growth of these organisms and assemblages under climate change scenarios.

Primary producers: physiological plasticity

The response of vascular plant leaf respiration to warming at sub-Antarctic Heard Island was stronger at high elevation compared with at low elevation (Schortemeyer et al. Reference Schortemeyer, Evans, Bruhn, Bergstrom and Ball2015). However, experimental warming using OTCs for 12 years did not result in species-specific responses or changes in the community composition of vascular plants on the Falkland Islands (Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2017). Increased growth of D. antarctica and C. quitensis was reported on Anvers Island under infrared heaters (Day et al. Reference Day, Ruhland, Strauss, Park, Krieg, Krna and Bryant2009) and in passive warming chambers (Day et al. Reference Day, Ruhland, Grobe and Xiong1999, Reference Day, Ruhland and Xiong2008). These responses are further supported by the photosynthetic temperature response appearing to be suboptimal for D. antarctica and C. quitensis, with optimum rates at 10–14°C, suggesting that warming may promote greater carbon acquisition (Xiong et al. Reference Xiong, Ruhland and Day1999). However, warming with OTCs on King George Island resulted in no effect on the growth or photosynthesis of D. antarctica, while C. quitensis showed increased photosynthetic performance and growth (Saez et al. Reference Saez, Cavieres, Galmes, Gil-Pelegrin, Peguero-Pina and Sancho-Knapik2018a). Antarctic vascular plants exposed to field warming within OTCs showed reduced freezing resistance on King George Island (Sierra-Almeida et al. Reference Sierra-Almeida, Cavieres and Bravo2018). Laboratory studies on the photosynthetic performance of D. antarctica indicate increased photochemical activity and decreased thermal dissipation activity and specific leaf mass with warming (Saez et al. Reference Saez, Rivera, Ramirez, Vallejos, Cavieres, Corcuera and Bravo2019). However, increased growth under warming may be limited by mesophyll conductance, indicating that water limitation may counteract warming effects (Fuentes-Lillo et al. Reference Fuentes-Lillo, Cuba-Diaz and Rifo2017, Saez et al. Reference Saez, Galmes, Ramirez, Poblete, Rivera and Cavieres2018b). In addition, there is little evidence for photosynthetic temperature acclimation across temperatures from 7°C to 20°C (Xiong et al. Reference Xiong, Mueller and Day2000).

Primary producers: historical proxies

Various studies using historical proxies indicate that changes in moss growth during the last 50 years along the Antarctica Peninsula have been exceptional in a historical context, and they are expected to increase further with future climate warming (Royles et al. Reference Royles, Amesbury, Convey, Griffiths, Hodgson, Leng and Charman2013, Amesbury et al. Reference Amesbury, Roland, Royles, Hodgson, Convey, Griffiths and Charman2017, Charman et al. Reference Charman, Amesbury, Roland, Royles, Hodgson, Convey and Griffiths2018). However, this is contingent on topography controlling suitable microclimatic conditions, including water availability in particular (Stelling et al. Reference Stelling, Yu, Loisel and Beilman2018). Similar evidence has been reported from sub-Antarctic islands such as Iles Crozet (Van der Putten et al. Reference Van der Putten, Hebrard, Verbruggen, de Vijver, Disnar and Spassov2008). Additionally, lake sediment cores show increased moss remains during the Holocene ‘climate optimum’ (c. 3800–1300 years bp) at Signy Island (Jones et al. Reference Jones, Hodgson and Chepstow-Lusty2000). The remains of a peatland ecosystem re-exposed from ice cover have been found near Cape Rasmussen, Graham Coast (65°S), an ecosystem type not currently present in the Maritime Antarctic, indicating that warm periods have occurred along the Antarctic Peninsula during the last 2500 years and that future climate warming may facilitate the re-establishment and spread of such ecotypes (Yu et al. Reference Yu, Beilman and Loisel2016, Loisel et al. Reference Loisel, Yu, Beilman, Kaiser and Parnikoza2017).

Microbial responses: environmental gradients and proxies

Fungal community composition did not change with latitude across a 54–72°S gradient along the Scotia Arc and Antarctic Peninsula, with changes instead being associated with vegetation, microclimate and edaphic factors (Yergeau et al. Reference Yergeau, Bokhorst, Huiskes, Boschker, Aerts and Kowalchuk2007, Dennis et al. Reference Dennis, Rushton, Newsham, Lauducina, Ord and Daniell2012), and vegetation-soil associations for microbes have also been found in the McMurdo Dry Valley ecosystems (Lee et al. 2019). Fungal and bacterial diversity were positively correlated with mean annual surface air temperature across the 54–72°S gradient (Newsham et al. Reference Newsham, Hopkins, Carvalhais, Fretwell, Rushton, O’Donnell and Dennis2016, Dennis et al. Reference Dennis, Newsham, Rushton, O'Donnell and Hopkins2019). Comparisons across large latitudinal scales indicate the loss of microbial diversity in colder environments (Dragone et al. Reference Dragone, Childress, Vanderburgh, Willmore, Hogg and Sancho2025). Moss-inhabiting diatom species richness similarly declines with elevation on sub-Antarctic Iles Kerguelen (Gremmen et al. Reference Gremmen, Van De Vijver, Frenot and Lebouvier2007). Records of testate amoebae obtained from moss bank archives indicate increases in the abundance of these organisms associated with rising air temperatures since the 1950s (Royles et al. Reference Royles, Amesbury, Convey, Griffiths, Hodgson, Leng and Charman2013, Reference Royles, Amesbury, Roland, Jones, Convey and Griffiths2016). Diatom community changes have also been used to reconstruct historic climates on Ile de la Possession and Iles Crozet (Ooms et al. Reference Ooms, van de Vijver, Temmerman and Beyens2011).

Microbial responses: experimental studies

Warming with OTCs induced consistent increases in the abundance of fungi and bacteria, and in the Alphaproteobacteria-to-Acidobacteria ratio, in a study spanning from the Falkland Islands (54°S) to Anchorage Island (67°S) in both moss and fellfield vegetation (Yergeau et al. Reference Yergeau, Bokhorst, Kang, Zhou, Greer, Aerts and Kowalchuk2012). Similarly, a 20% increase in bacterial and fungal biomass was reported at Fildes Peninsula following warming over 7 years (Kim et al. Reference Kim, Park, Kim, Youn, Yang and Casanova-Katny2018), while plant-associated microbial communities declined in OTCs on King George Island (Perazzolli et al. Reference Perazzolli, Vicelli, Antonielli, Longa, Bozza, Bertini, Caruso and Pertot2022). OTC impacts on the concentrations of Gram-positive bacterial markers in soil were negative at Mars Oasis on Alexander Island (72°S), while no such response was observed at Signy Island (60°S), probably owing to the weaker effects of OTCs on soil temperatures at the latter site (Dennis et al. Reference Dennis, Newsham, Rushton, Ord, O'Donnell and Hopkins2013). However, using Illumina sequencing, Newsham et al. (Reference Newsham, Tripathi, Dong, Yamamoto, Adams and Hopkins2019) reported strong responses of soil bacterial communities to nutrient additions but no effects of warming with OTCs at Mars Oasis after 4 years, as well as no effects of OTCs on the Alphaproteobacteria-to-Acidobacteria ratio. Warming-induced stress, using miniature closed cloches, resulted in reduced fungal diversity and the dominance of a few species in Victoria Land (74°S; Tosi et al. Reference Tosi, Onofri, Brusoni, Zucconi and Vishniac2005). Soils from the McMurdo Dry Valleys showed declines in bacterial cell numbers in response to warming and increased FT frequency under laboratory conditions (Knox et al. Reference Knox, Andriuzzi, Buelow, Takacs-Vesbach, Adams and Wall2017). In contrast, laboratory studies using soils from Signy Island (60°S) showed that bacteria were more affected by warming than changes in FT frequency, while fungal abundance and community structure were most affected by FT frequency (Yergeau & Kowalchuk Reference Yergeau and Kowalchuk2008). Laboratory studies of Antarctic algal species show increased growth rates at higher temperatures (Teoh et al. Reference Teoh, Chu, Marchant and Phang2004, Wong et al. Reference Wong, Teoh, Phang, Lim and Beardall2015).

Microbial responses: physiological flexibility

The temperature sensitivity of Antarctic microbial process rates, as measured through Q ₁₀ values quantified under laboratory conditions, has been shown to increase with mean annual soil temperature. This has been used to suggest that bacterial communities from colder regions are less temperature sensitive than those from warmer regions, although warming with OTCs for 3 years had no effect on the temperature relationships of the soil bacterial community in question (Rinnan et al. Reference Rinnan, Rousk, Yergeau, Kowalchuk and Baath2009). Laboratory studies of soil microbial process rates, such as respiration and nitrogen mineralization, often report increased rates with higher temperatures (Bokhorst et al. Reference Bokhorst, Huiskes, Convey and Aerts2007a, Sun et al. Reference Sun, Dennis, Laudicina, Ord, Rushton and O'Donnell2014, Laudicina et al. Reference Laudicina, Benhua, Dennis, Badalucco, Rushton and Newsham2015, Khan & Ball Reference Khan and Ball2024). However, conversely, cotton strip decomposition was not affected by experimental warming in the McMurdo Dry Valleys (Treonis et al. Reference Treonis, Wall and Virginia2002). Increased temperature fluctuation, associated in the natural environment with clear skies and high solar radiation during the summer, reduces fungal growth under laboratory conditions (Newsham Reference Newsham2024).

Invertebrate responses: field observations

Some non-native invertebrates (e.g. the beetles Merizodus soledadinus (Guerin-Ménéville) and Trechisibus antarcticus (DeJean)) have expanded their ranges on South Georgia (Convey et al. Reference Convey, Key, Key, Belchier and Waller2011, Tichit et al. Reference Tichit, Brickle, Newton, Convey and Dawson2024) and Iles Kerguelen (Ouisse et al. Reference Ouisse, Day, Laville, Hendrickx, Convey and Renault2020), which may in part have been facilitated by local environmental warming. Similarly, Ectemnorhinini weevil colonization and speciation rates appear to be linked to long-term climate variability across Southern Ocean islands along the Antarctic Polar Front (Baird et al. Reference Baird, Shin, Oberprieler, Hullé, Vernon and Moon2021). However, there are no repeat descriptions or long-term monitoring studies of terrestrial invertebrate communities in Antarctica except for nematode populations in the McMurdo Dry Valleys (Andriuzzi et al. Reference Andriuzzi, Adams, Barrett, Virginia and Wall2018). Large egg aggregations of the springtails Cryptopygus antarcticus (Willem) and Friesea grisea (Schäffer) (now reclassified to Friesea antarctica (Greenslade Reference Greenslade2018)) have been linked with very early commencement of the growing season near Palmer Station (Schulte et al. Reference Schulte, Elnitsky, Benoit, Denlinger and Lee2008).

Invertebrate responses: environmental gradients

Arthropod species richness and abundance declined with elevation on Marion Island, indicating that warming may result in increased abundance and richness (Lee et al. Reference Lee, Somers and Chown2012, Hugo-Coetzee & le Roux Reference Hugo-Coetzee and le Roux2018, Treasure et al. Reference Treasure, le Roux, Mashau and Chown2019). Seasonality and resource availability explain the size differences of weevils with elevation between Marion Island and Heard Island (Chown & Klok Reference Chown and Klok2003), indicating that lengthening of the growing season may lead to larger-sized animals with consequential outcomes for life history features such as overall egg production or offspring size. A latitudinal comparison of nematode abundance, based on gene abundance, did not indicate a consistent pattern along the Antarctic Peninsula except for considerably lower abundance on southern Alexander Island (71°S; Yergeau et al. Reference Yergeau, Bokhorst, Huiskes, Boschker, Aerts and Kowalchuk2007). However, this location supports a strikingly higher and distinct nematode diversity compared to the rest of the Maritime Antarctic region (Maslen & Convey Reference Maslen and Convey2006).

Invertebrate responses: experimental studies

Springtail abundance and alpha diversity decline under experimental warming on sub- and peri-Antarctic islands (McGeoch et al. Reference McGeoch, le Roux, Hugo and Chown2006, Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2017), while the response of the dominant Maritime Antarctic springtail, C. antarcticus, shows a mixed response to experimental warming. Increased abundance was reported from active warming in combination with increased water input on Anvers Island near Palmer Station (64°S; Day et al. Reference Day, Ruhland, Strauss, Park, Krieg, Krna and Bryant2009), whereas declines in abundance were found under a passive warming manipulation experiment at the same location after 4 years (Convey et al. Reference Convey, Pugh, Jackson, Murray, Ruhland, Xiong and Day2002). These responses mostly reflect differences in warming intensity and increased growth under active warming compared to passive warming. At Signy Island (60°S), C. antarcticus increased in abundance after 8 years of warming in closed cloches (Kennedy Reference Kennedy1994) but showed a decreasing abundance trend following 2 years of warming with OTCs (Bokhorst et al. Reference Bokhorst, Huiskes, Convey, van Bodegom and Aerts2008). However, the latter pattern was not maintained, and no effect on abundance was found after 10 years of warming (Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2016), possibly reflecting the timescale required for such field manipulation experiments in the Antarctic to stabilize and generate reliable community and abundance profiles. Microarthropod abundance increased in mosses warmed by OTCs over 8 years at Fildes Peninsula (62°S; Prather et al. Reference Prather, Casanova-Katny, Clements, Chmielewski, Balkan and Shortlidge2019), while no effect on microarthropod abundance associated with OTC warming over 2 years was reported on Anchorage Island (67°S; Bokhorst et al. Reference Bokhorst, Huiskes, Convey, van Bodegom and Aerts2008). Warming through the use of closed cloches at Cape Bird on Ross Island for 3 years also did not result in changes in the abundance of microarthropods (Sinclair Reference Sinclair2002).

In the McMurdo Dry Valleys, while nematode abundance did not show a response to 2 years of passive warming using OTCs (Treonis et al. Reference Treonis, Wall and Virginia2002), a 42% decline in the abundance of Scottnema lindsayae (Timm), the dominant species in this community, was reported after 8 years of warming (Simmons et al. Reference Simmons, Wall, Adams, Ayres, Barrett and Virginia2009). In a ventilated cloche study at Mars and Ares oases, Alexander Island (72°S), there were very rapid increases of two to three orders of magnitude in soil nematode population density after only 1 year of manipulation, although in subsequent years this dropped back to only two- to five-fold increases (Convey & Wynn-Williams Reference Convey and Wynn-Williams2002, Convey Reference Convey, Huiskes, Gieskes, Rozema, Schorno, van der Vies and Wolff2003). These changes appear mostly driven by the bacterivorous genus Plectus (Bastian) in response to the rapid development of surface microbial and moss communities. Although warming-induced increases in the population density of Plectus inhabiting hydrated vegetation have similarly been recorded in a 3 year study on Adelaide Island (Newsham et al. Reference Newsham, Hall and Maslen2021), no effect of OTCs was found on total tardigrade and nematode abundances after 10 years of warming on Anchorage Island (S. Bokhorst, unpublished data 2016) and after 8 years of warming on Fildes Peninsula (Prather et al. Reference Prather, Casanova-Katny, Clements, Chmielewski, Balkan and Shortlidge2019).

An exceptional warming event in the McMurdo Dry Valleys, which resulted in widespread flooding (Fig. 1d), led to the decreased abundance of the microbivorous nematode S. lindsayae, while the omnivorous Eudorylaimus spp. increased in abundance (Barrett et al. Reference Barrett, Virginia, Wall, Doran, Fountain, Welch and Lyons2008, Simmons et al. Reference Simmons, Wall, Adams, Ayres, Barrett and Virginia2009). However, 2 decades of monitoring of the soil community in the McMurdo Dry Valleys has not revealed consistent patterns in nematode abundances with respect to mean summer temperatures, although the community did respond to extreme events related to water availability, as described earlier (Andriuzzi et al. Reference Andriuzzi, Adams, Barrett, Virginia and Wall2018, Barrett et al. Reference Barrett, Adams, Doran, Dugan, Myers and Salvatore2024). Antarctic nematode responses to climate change will be largely contingent on local soil moisture and vegetation patterns (Nielsen et al. Reference Nielsen, Wall, Adams and Virginia2011, Nielsen & Wall Reference Nielsen and Wall2013, Snyder et al. Reference Snyder, Adams, Borgmeier, Jorna, Power, Salvatore and Barrett2025).

Invertebrate responses: physiological plasticity

Laboratory studies on the upper and lower thermal limits of native and invasive invertebrate species on sub-Antarctic islands (Kerguelen and Marion islands) indicate that these are likely to be exceeded more frequently in short-term events under climate warming (Klok & Chown Reference Klok and Chown1997, van der Merwe et al. Reference van der Merwe, Chown and Smith1997, Klok & Chown Reference Klok and Chown1998, Klok & Chown Reference Klok and Chown2001, Sinclair & Chown Reference Sinclair and Chown2002, Reference Sinclair and Chown2003, Smith Reference Smith2002, Sinclair et al. Reference Sinclair, Klok and Chown2004, Reference Sinclair, Terblanche, Scott, Blatch, Klok and Chown2006, Deere et al. Reference Deere, Sinclair, Marshall and Chown2006, Slabber et al. Reference Slabber, Roger Worland, Petter Leinaas and Chown2007, Lalouette et al. Reference Lalouette, Williams, Cottin, Sinclair and Renault2012, Haupt et al. Reference Haupt, Sinclair and Chown2017). Increased population growth of C. antarcticus from Anchorage Island (67°S) was reported with warming in controlled laboratory experiments (Martin et al. Reference Martin, Aerts, Convey and Bokhorst2023). Various invertebrates show great interannual variation in supercooling point, in part driven by avoidance and glycerol/glucose production (Sinclair & Sjursen Reference Sinclair and Sjursen2001a, Worland & Convey Reference Worland and Convey2001, Sjursen & Sinclair Reference Sjursen and Sinclair2002), which should allow them to survive unseasonal temperature extremes. Laboratory studies into the impact of FT cycle frequency on Continental Antarctic nematodes showed that increased FT cycles resulted in greater mortality among smaller nematodes and reduced bacterial cell numbers (Knox et al. Reference Knox, Andriuzzi, Buelow, Takacs-Vesbach, Adams and Wall2017). A similar response was observed in the field for the nematode S. lindsayae in Taylor Valley (Knox et al. Reference Knox, Wall, Virginia, Vandegehuchte, Gil and Adams2016). Laboratory incubation of the tardigrade Acutuncus antarcticus indicated more rapid development at 15°C, but that those reared at 5°C lived longer and produced more offspring (Giovannini et al. Reference Giovannini, Manfrin, Greco, Vincenzi, Altiero and Guidetti2023). Metabolic activity of the Continental Antarctic nematode Plectus murrayi increased when cultured up to 40°C under laboratory conditions, indicating a large temperature range and resource demand under future climate warming (Robinson et al. Reference Robinson, Hansen, Xue and Adams2023).

Invertebrate responses: historical records and proxies

Population expansions and declines have been reported for the oribatid mites Alaskozetes antarcticus (Michael) and Halozetes belgicae (Michael) in conjunction with a warming period in the Holocene through analysis of lake sediment cores at Signy Island (Hodgson & Convey Reference Hodgson and Convey2005).

Summary of biotic responses to temperature

Primary producer distribution patterns and physiological activity across large-scale latitudinal gradients, along with historical proxies, indicate that there is scope for community change if temperatures keep rising. However, to date, no such changes have been reported and only a limited number of local-scale primary producer population increases have been documented. Field experimental warming studies show a mixed response within and across biological groups, highlighting the context dependency of climate warming impacts (Fig. 3). While parts of Antarctica have warmed, there is as yet relatively little direct evidence of terrestrial biological responses to these changes to the climate in the natural environment. This suggests that biotic responses to warming may take longer than we anticipate to emerge, which is not unsurprising given the low physiological activity of most affected organisms, or it suggests that warming levels to date have been insufficient to generate measurable biological responses.

Figure 3.

Heatmap of biological responses to altered levels of temperature, water, ultraviolet (UV) radiation exposure and nutrients in Antarctica. Biological responses across taxonomic groups (microbial, invertebrate and primary producers) are reported from field observational studies (obs), experimental studies (Exp.) in both field and laboratory settings, historical evidence for change (Hist.) and indications of sufficient physiological flexibility (Physiol.). Grey indicates negative impacts and white represents a lack of data. Dark colours indicate increased growth/population size or sufficient physiological flexibility and light colours indicate a mixed response (both positive and negative).

Figure 3 Long description

A four-panel heatmap. The Y-axis for all panels lists taxonomic groups from top to bottom: Fungi, Bacteria, Tardigrades, Springtails, Protozoa, Nematodes, Mites, Diptera, Vascular plants, Liverworts, Lichens, Bryophytes, and Algae. Horizontal dashed lines separate microbial, invertebrate, and primary producer groups. The X-axis for all panels lists study types: obs, Exp dot, Hist dot, and Physiol dot.

* Temperature Panel: Shows orange and red blocks. Red (increased growth) is prominent in the Physiol dot column for most groups and the Exp dot column for Vascular plants and Bryophytes. Orange (mixed response) appears in the Exp dot column for Fungi, Bacteria, Tardigrades, and Springtails.

* Water Panel: Shows light blue and dark blue blocks. Dark blue (increased growth) is concentrated in the Physiol dot column for Fungi, Bacteria, and Tardigrades, and the Exp dot column for Springtails, Vascular plants, and Bryophytes. Light blue (mixed response) is scattered across obs and Exp dot columns.

* U V Panel: Shows solid vertical bars. The Exp dot column is entirely grey (negative impact) for all taxa. The Physiol dot column is entirely purple (increased growth or flexibility) for all taxa. The obs and Hist dot columns are white (no data).

* Nutrients Panel: Shows light green and dark green blocks. Light green (mixed response) dominates the obs column for almost all taxa. Dark green (increased growth) appears in the obs column for Tardigrades, Springtails, Nematodes, and Mites, and in the Exp dot column for Bryophytes.

Primary producers: environmental gradients

Comparison of cryptogam physiological activity shows an increase from the cold and dry McMurdo Dry Valleys to the wetter Antarctic Peninsula (Sancho et al. Reference Sancho, Green and Pintadoa2007, Schroeter et al. Reference Schroeter, Green, Pintado, Turk and Sancho2017). A key aspect here is that lichen activity in the McMurdo Dry Valleys is activated by water concurrently with potentially damaging light levels, whereas, along the Antarctic Peninsula, activity can occur throughout the year but often at lower levels. Similar contrasts in the activity levels of cryptogams have been reported from xeric and mesic sites along the Antarctic Peninsula (Schlensog et al. Reference Schlensog, Green and Schroeter2013). Comparisons along an elevation gradient indicate that water supply has a greater influence on lichen activity than temperature on Livingston Island (Schroeter et al. Reference Schroeter, Green, Pintado, Türk and Sancho2021). Physiological adaptations to submergence and desiccation tolerance correspond with the distribution of moss species (Longton Reference Longton1988, Wasley et al. Reference Wasley, Robinson, Lovelock and Popp2006b, Reference Wasley, Robinson, Turnbull, King, Wanek and Popp2012).

Primary producers: experimental studies

Experimental drying and field-water deficits have increased the mortality of Azorella species on sub-Antarctic Marion Island and Macquarie Island (le Roux et al. Reference le Roux, McGeoch, Nyakatya and Chown2005, Bergstrom et al. Reference Bergstrom, Bricher, Raymond, Terauds, Doley and McGeoch2015, Dickson et al. Reference Dickson, Baker, Bergstrom, Bricher, Brookes and Raymond2019). Similarly, drying in parts of coastal East Antarctica has led to the deterioration of moss vegetation (Robinson et al. Reference Robinson, King, Bramley-Alves, Waterman, Ashcroft and Wasley2018), while experimental water addition to moss communities increased productivity (Wasley et al. Reference Wasley, Robinson, Lovelock and Popp2006a). A similar response to water amendment was reported for moss and vascular plant biomass at Palmer Station on Anvers Island (Day et al. Reference Day, Ruhland, Strauss, Park, Krieg, Krna and Bryant2009). Increased moss and algal abundance in response to increased water availability was reported after long-term monitoring at Cape Hallett (Brabyn et al. Reference Brabyn, Beard, Seppelt, Rudolph, Türk and Green2006), but the biological response was not sustained (Colesie et al. Reference Colesie, Pan, Cary, Gemal, Brabyn and Kim2022).

Primary producers: physiological plasticity

The algal genus Trebouxia (Hildreth & Ahmadjian), a photobiont of some lichens, has been found to be susceptible to drought stress, but it recovers rapidly from freezing (Sadowsky & Ott Reference Sadowsky and Ott2012). However, large differences exist in desiccation resistance between the photobionts of various lichens (Sadowsky et al. Reference Sadowsky, Mettler-Altmann and Ott2016). The growth response of C. quitensis was found to be stronger to water additions than to warming under laboratory incubations (Fuentes-Lillo et al. Reference Fuentes-Lillo, Cuba-Diaz and Rifo2017). Species-specific morphological characteristics affect the influence of vapour pressure differences of moss and lichen species on their carbon uptake and loss (Stanton et al. Reference Stanton, Merlin, Bryant and Ball2014, Reference Stanton, Ormond, Koch and Colesie2023).

Primary producers: historical proxies

Increases in moss growth have been reported from historical archives (70–2700 years bp) in relation to greater water availability along the Antarctic Peninsula (Royles et al. Reference Royles, Amesbury, Convey, Griffiths, Hodgson, Leng and Charman2013, Royles & Griffiths Reference Royles and Griffiths2015, Amesbury et al. Reference Amesbury, Roland, Royles, Hodgson, Convey, Griffiths and Charman2017, Charman et al. Reference Charman, Amesbury, Roland, Royles, Hodgson, Convey and Griffiths2018, Stelling et al. Reference Stelling, Yu, Loisel and Beilman2018).

Microbial and invertebrate responses: environmental gradients

Microbial biomass and respiration rates were enhanced in the proximity of drainage lines in the McMurdo Dry Valleys, but these patterns were also affected by soil conditions and salinity effects, indicating that the impact of water was not consistent across the landscape (Ball & Levy Reference Ball and Levy2015, Lee et al. Reference Lee, Caruso, Archer, Gillman, Lau and Cary2018). Similar patterns have been reported for soil communities during extreme melt events in this region (Ball et al. Reference Ball, Barrett, Gooseff, Virginia and Wall2011, Nielsen et al. Reference Nielsen, Wall, Adams, Virginia, Ball, Gooseff and McKnight2012, Gooseff et al. Reference Gooseff, Barrett, Adams, Doran, Fountain and Lyons2017).

Microbial and invertebrate responses: experimental studies

Sylvain et al. (Reference Sylvain, Wall, Cherwin, Peters, Reichmann and Sala2014) reported lower nematode abundances at wetter sites in the McMurdo Dry Valleys and also in response to water additions. This response contrasts with other reports from the same location, probably reflecting differences in watering intensity and species-specific tolerance limits (Nielsen et al. Reference Nielsen, Wall, Adams, Virginia, Ball, Gooseff and McKnight2012). The abundance of the springtail C. antarcticus increased in response to water additions in the field at Palmer Station (Day et al. Reference Day, Ruhland, Strauss, Park, Krieg, Krna and Bryant2009), which corresponds with its poor control over water loss, which is broadly characteristic of springtails (Block & Convey Reference Block and Convey2001, Convey et al. Reference Convey, Block and Peat2003, Elnitsky et al. Reference Elnitsky, Benoit, Denlinger and Lee2008).

Microbial and invertebrate responses: physiological plasticity

Water additions to Antarctic biological soil crusts increased nitrogen fixation rates under laboratory conditions (Perez et al. Reference Perez, Aravena, Ivanovich and McCulloch2017). They also increased soil respiration, nitrification and the decomposition of cotton strips in McMurdo Dry Valley soils in the laboratory (Treonis et al. Reference Treonis, Wall and Virginia2002). However, extracellular enzyme activities can be impaired under enhanced water and temperature conditions (Misiak et al. Reference Misiak, Goodall-Copestake, Sparks, Worland, Boddy and Magan2021).

Snow manipulations

In contrast with Arctic and alpine regions, snow manipulation experiments are scarce in Antarctica (Wipf & Rixen Reference Wipf and Rixen2010, Cooper Reference Cooper2014). Ayres et al. (Reference Ayres, Nkem, Wall, Adams, Barrett and Simmons2010) reported shifts in the nematode communities of the McMurdo Dry Valleys, where increased snow depth resulted in altered moisture conditions. The native vascular plant flora appears to be negatively affected by deeper and more prolonged snow cover (Edwards Reference Edwards1972, Park et al. Reference Park, Ahn and Lee2013). Year-round placement of OTCs and consequential (unintended) accumulation of snow (Fig. 4) have been implicated in the decline of the lichen Usnea antarctica (Du Rietz) on Signy Island (Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2016). The presence of Usnea is also used as a proxy for thinner snowpacks along the Antarctic Peninsula (Vieira et al. Reference Vieira, Mora, Pina and Schaefer2014). Bacterial activity levels are strongly regulated by snow and ice cover, as the thickness of these layers regulates light levels and UV radiation exposure (Cockell et al. Reference Cockell, Rettberg, Horneck, Wynn-Williams, Scherer and Gugg-Helminger2002).

Figure 4.

Snow-filled open-top chambers on Signy Island (left, summer 2004) and Anchorage Island (right, winter 2005), where the thicker winter snowpack insulates the contained vegetation against freezing temperatures, with detrimental consequences for lichens such as U. antarctica (Bokhorst et al. Reference Bokhorst, Convey, Huiskes and Aerts2016).

Summary of biotic responses to water

Primary producer distribution patterns and physiological activity are strongly driven by water availability across Antarctica, as is apparent across current environmental gradients and historical proxies. Most primary producers will benefit from increased moisture levels or duration of water availability, except at locations that are already saturated. Although experimental evidence is limited, the same applies for associated microbial and invertebrate communities (Fig. 3). Despite being a continent almost completely covered by snow and ice, very few studies relating to snow and ice cover have been made in Antarctic terrestrial ecosystems, indicating that the role of snow and ice on organism physiology, growth and population sizes is largely unknown.

Primary producer responses to UV: environmental gradients

There appears to be a considerable shift in the type of lichen secondary compounds produced naturally, which help in protection against UV radiation, among lichen species from the northern Maritime Antarctic compared to those inhabiting more southern locations (de Jonge et al. Reference de Jonge, Convey, Klarenberg, Cornelissen and Bokhorst2025), indicating that UV exposure and lichen chemistry may affect species distribution patterns.

Primary producer responses to UV: experimental studies

Newsham & Robinson (Reference Newsham and Robinson2009) carried out a meta-analysis of studies into the responses of Antarctic and Arctic bryophytes and vascular plants to UV radiation, concluding that enhanced levels of UV increased pigmentation levels and DNA damage and reduced biomass. The underlying repair mechanisms have yet to be completely resolved (Contreras & Zúñiga Reference Contreras and Zúñiga2025). The lichens Turgidosculum complicatulum (Nyl), Stereocaulon alpinum (Laurer) and U. antarctica did not show any physiological response to 2 years of reduced UV levels on Léonie Island (Huiskes et al. Reference Huiskes, Lud and Moerdijk-Poortvliet2001, Lud et al. Reference Lud, Huiskes, Moerdijk and Rozema2001a). UV filtering reduced the concentration of UV-absorbing compounds present in moss and lichen species in East Antarctica (Gautam et al. Reference Gautam, Singh and Pant2011, Singh et al. Reference Singh, Gautam and Pant2012). Antarctic mosses show UV screening capabilities, although endemic species appear to be poorly protected compared to cosmopolitan species (Dunn & Robinson Reference Dunn and Robinson2006, Turnbull & Robinson Reference Turnbull and Robinson2009). The thalli of the liverwort Cephaloziella varians (Gottsche) lost their dark colour when placed underneath UV-filtering Mylar screens, and pigmentation was induced within 48 h of removing the screens (Snell et al. Reference Snell, Kokubun, Griffiths, Convey, Hodgson and Newsham2009). Ambient UV levels have been implicated in affecting rhizosphere microbial communities associated with D. antarctica (Avery et al. Reference Avery, Lewis Smith and West2003), while fungal symbionts appear to help protect C. quitensis against UV damage (Barrera et al. Reference Barrera, Hereme, Ruiz-Lara, Larrondo, Gundel and Pollmann2020, Acuña-Rodríguez et al. Reference Acuña-Rodríguez, Ballesteros, Gundel, Castro-Nallar, Barrera, Carrasco-Urra and Molina-Montenegro2024). Historical ozone concentrations have been tracked through flavonoid levels in herbarium specimens of the Antarctic moss Bryum argenteum (Ryan et al. Reference Ryan, Burne and Seppelt2009).

Primary producer responses to UV: physiological plasticity

Physiological plasticity responses of primary producers to UV radiation exposure have not been widely studied. However, laboratory studies show increased membrane damage and photo-inactivation in C. quitensis with exposure to high UV levels (Navarrete-Gallegos et al. Reference Navarrete-Gallegos, Bravo, Molina-Montenegro and Corcuera2012).

Microbial responses to UV radiation: experimental studies

Strong microalgal colonization was reported in ventilated cloches that also reduced UV radiation on Signy Island (Wynn-Williams Reference Wynn-Williams1996). Algae of the genus Zygnema (Bessey) showed reduced levels of photosystem II activity under high-UV conditions, while phenolic compound concentrations at the cell periphery increased (Pichrtova et al. Reference Pichrtova, Remias, Lewis and Holzinger2013). The terrestrial microalga Stichococcus bacillaris (Nägeli) showed reduced cell viability and maximum quantum yield of photosystem II under increased UV conditions (Hughes Reference Hughes2006). In contrast, the terrestrial alga Prasiola crispa (Kützing) showed limited and transient response differences between UV-sheltered and -exposed treatments (Lud et al. Reference Lud, Buma, van de Poll, Moerdijk and Huiskes2001b), although increased UV resulted in reduced photosynthetic performance (Post & Larkum Reference Post and Larkum1993). Cyanobacterial communities showed more species-specific responses to UV exposure (George et al. Reference George, Murray and Montiel2001). Fungal communities showed increased growth under reduced UV irradiance in Victoria Land (Tosi et al. Reference Tosi, Onofri, Brusoni, Zucconi and Vishniac2005), and bacterial communities similarly performed better underneath ultrathin soil layers (500 μm) compared with bacterial communities exposed to ambient UV levels (Cockell et al. Reference Cockell, Rettberg, Horneck, Scherer and Stokes2003).

Microbial responses to UV radiation: physiological plasticity

Laboratory studies on a strain of the freshwater alga Chlorella (UMACC 237) showed that high UV levels impaired the return of optimal photosystem II activity at higher temperatures (Wong et al. Reference Wong, Teoh, Phang, Lim and Beardall2015). Young vegetative algal cells adapt better to experimental UV stress exposure than older cells (> 6 months) under laboratory conditions (Holzinger et al. Reference Holzinger, Albert, Aigner, Uhl, Schmitt-Kopplin, Trumhova and Pichrtova2018). Pigmentation in various bacteria and fungi isolated from Antarctic environments increases resistance to environmental stressors such as high light and UV exposure (Arcangeli et al. Reference Arcangeli, Zucconi, Onofri and Cannistraro1997, Wong et al. Reference Wong, Chu, Marchant and Phang2007, Mojib et al. Reference Mojib, Farhoomand, Andersen and Bej2013, Reis-Mansur et al. Reference Reis-Mansur, Cardoso-Rurr, Silva, de Souza, Cardoso and Mansoldo2019). The fungus Arthrobotrys ferox (Onofri & Tosi) isolated from Antarctic soil showed better protection against UV radiation compared to temperate species (Zucconi et al. Reference Zucconi, Ripa, Selbmann and Onofri2002). Ice layers protect microbial communities of cryoconite and cryo-lake ecosystems from high light intensity (Bagshaw et al. Reference Bagshaw, Wadham, Tranter, Perkins, Morgan and Williamson2016).

Invertebrate responses to UV

Field experimental enhancements of UV radiation resulted in decreased microarthropod abundance in a study on Anvers Island, but this response may have been mediated through changes in the biochemical composition of the vegetation or litter formed (Convey et al. Reference Convey, Pugh, Jackson, Murray, Ruhland, Xiong and Day2002). The Continental Antarctic Collembola species Gomphiocephalus hodgsoni (Carpenter) showed reduced survival and moult rates when exposed to UV radiation compared to darkness and also showed upregulation of DNA repair mechanisms (Hawes et al. Reference Hawes, Marshall and Wharton2012).

Summary of biotic responses to UV radiation

Antarctic vegetation appears relatively well protected against UV radiation, but there are costs associated with this protection, which may to some extent impair physiology, growth, reproduction and distribution patterns. Similar observations have been made for microbes and invertebrates, but with fewer studies made on these organisms (Fig. 3). There have been limited comparisons across environmental gradients, local and latitudinal comparisons and historic proxies.

Primary producer responses to nutrients

Except for nitrophilous algae, hardly any vegetation grows in seal and penguin colonies due to trampling and extreme levels of nutrients (Smykla et al. Reference Smykla, Wołek and Barcikowski2007, Favero-Longo et al. Reference Favero-Longo, Cannone, Worland, Convey, Piervittori and Guglielmin2011). Around the periphery of such colonies, increased vegetation development can sometimes be observed where suitable habitats are present (Zwolicki et al. Reference Zwolicki, Barcikowski, Barcikowski, Cymerski, Stempniewicz and Convey2015), although there is no Antarctic equivalent to the sometimes spectacular ‘bird cliff’ vegetation that characterizes some parts of the High Arctic (Zwolicki et al. Reference Zwolicki, Zmudczyńska-Skarbek, Wietrzyk-Pełka, Convey, Goldstein and DellaSala2019). Sub-Antarctic islands show lusher and nutrient-enriched vegetation in proximity to penguin and seal colonies (Erskine et al. Reference Erskine, Bergstrom, Schmidt, Stewart, Tweedie and Shaw1998, Smith et al. Reference Smith, Steenkamp and Gremmen2001, Vidal et al. Reference Vidal, Jouventin and Frenot2003). Cryptogam abundance and diversity was also increased near petrel nests in the Vestfold Hills and Dronning Maud Land in Continental Antarctica (Ryan & Watkins Reference Ryan and Watkins1989, Leishman & Wild Reference Leishman and Wild2001). Lichen physiological activity is affected by nutrients from penguin colonies (Crittenden et al. Reference Crittenden, Scrimgeour, Minnullina, Sutton, Tang and Theobald2015). However, aside from such observational studies on vegetation development in the proximity of vertebrate aggregations, nutrient addition studies on vegetation are scarce, although mosses respond more strongly to nutrient additions than water amendments in East Antarctica (Wasley et al. Reference Wasley, Robinson, Lovelock and Popp2006a). Moss-inhabiting diatom communities are often dominated by different taxa in the proximity of nutrient inputs from vertebrate species along the Antarctic Peninsula (Kopalova et al. Reference Kopalova, Ochyra, Nedbalova and Van de Vijver2014).

Microbial responses to nutrients

Marine-derived nutrients promote soil microbial abundance (Smith & Steyn Reference Smith and Steyn1982), microbial processes and decomposition on sub-Antarctic islands (Smith et al. Reference Smith, Steenkamp and French1993, Smith Reference Smith2003, Reference Smith2005, Reference Smith2008) and at sites along the Antarctic Peninsula (Bokhorst et al. Reference Bokhorst, Huiskes, Convey and Aerts2007a, Park et al. Reference Park, Day, Strauss and Ruhland2007, Zhu et al. Reference Zhu, Liu, Xu, Ma, Zhao and Sun2008, Reference Zhu, Liu, Ma, Sun, Xu and Sun2009, Teixeira et al. Reference Teixeira, Yeargeau, Balieiro, Piccolo, Peixoto, Greer and Rosado2013, 2014, Rampelotto et al. Reference Rampelotto, Barboza, Pereira, Triplett, Schaefer, de Oliveira Camargo and Roesch2015, Guo et al. Reference Guo, Wang, Li, Rosas, Zang and Ma2018, 2019, Ramírez-Fernández et al. Reference Ramírez-Fernández, Trefault, Carú and Orlando2019, Wang et al. Reference Wang, D'Imperio, Liu, Tian, Jia and Ambus2019), as well as at colder sites such as Ross Island (Ball et al. Reference Ball, Tellez and Virginia2015) and Dronning Maud Land (Cocks et al. Reference Cocks, Newton and Stock1998). However, field manipulation studies in the McMurdo Dry Valleys suggest that the impacts of nutrients are limited by water availability (Ball et al. Reference Ball, Adams, Barrett, Wall and Virginia2018), and high nutrient levels can result in reduced microbial biomass, process rates and bacterial diversity and community composition (Ball & Virginia Reference Ball and Virginia2014). There is also evidence that warming can both constrain and enhance certain microbial responses to additional nutrients (Dennis et al. Reference Dennis, Newsham, Rushton, Ord, O'Donnell and Hopkins2013, Newsham et al. Reference Newsham, Misiak, Goodall-Copestake, Dahl, Boddy, Hopkins and Davey2022).

Invertebrate responses to nutrients

Field surveys in the proximity of nitrogen sources from penguins and elephant seals indicate that invertebrate abundance and diversity are greatly increased compared to sites without nitrogen input along the Antarctic Peninsula and Scotia Arc (Bokhorst & Convey Reference Bokhorst and Convey2016, Bokhorst et al. Reference Bokhorst, Convey and Aerts2019). Similar patterns have been observed in Dronning Maud Land near nesting petrels (Ryan & Watkins Reference Ryan and Watkins1989). However, nematode communities within penguin colonies at much colder and drier sites on Ross Island were dominated by a single species (Porazinska et al. Reference Porazinska, Wall and Virginia2002).

Summary of biotic response to nutrients

The abundance and physiological activity of plants and associated organisms tend to respond positively to nutrient inputs, indicating that most Antarctic terrestrial ecosystems are nutrient limited. Only in some of the coldest and driest regions are nutrients not the most limiting resource. However, most such knowledge is derived from environmental gradient studies, and there is a lack of controlled field and laboratory experimentation to better understand underlying mechanisms (Fig. 3). Given the strong impacts that external nutrients tend to have on population size, any changes in marine-derived nutrient inputs from penguins, birds and seals may affect local terrestrial biodiversity patterns.

Summary of freshwater biotic responses to temperature

There is clear evidence from different methodological approaches that increased temperature results in increased physiological activity and growth in freshwater ecosystems (Fig. 7). However, this creates opportunities for algal blooms and increased cyanobacterial toxins, which could severely impact local diversity.

Figure 7.

Heatmap of biological responses in freshwater ecosystems to enhanced levels of temperature, water, ultraviolet (UV) radiation exposure and nutrients in Antarctica. Biological responses across taxonomic groups including unicellular organisms, invertebrates and chlorophyll as a measure of productivity are reported from field observational studies (obs.), experimental studies (Exp.) in both field and laboratory settings, historical evidence for change (Hist.) and indications of sufficient physiological flexibility (Physiol.). White represents a lack of data, while dark colours indicate increased growth/population size or sufficient physiological flexibility, and light colours indicate a mixed response (positive and negative).

Figure 7 Long description

Four vertical rectangular panels. The Y-axis for all panels lists taxonomic groups from top to bottom: Flagellate, Diatoms, Bacteria, Arthropods, and Chlorophyll. Horizontal dashed lines separate unicellular organisms (Flagellate, Diatoms, Bacteria) from invertebrates (Arthropods) and productivity measures (Chlorophyll). The X-axis lists study types: obs dot, Exp dot, Hist dot, and Physiol dot.

Panel 1, Temperature: Red blocks indicate increased growth or flexibility for Flagellate (Exp dot and Physiol dot), Diatoms (Hist dot), Bacteria (all study types except obs dot), Arthropods (Exp dot and Physiol dot), and Chlorophyll (all study types except Exp dot).

Panel 2, Water: Light blue blocks (mixed response) for Flagellate, Diatoms, and Bacteria under obs dot. Dark blue blocks (increased growth) for Flagellate, Diatoms, and Bacteria under Hist dot, and for Chlorophyll under obs dot and Hist dot.

Panel 3, U V: Grey blocks (mixed response) for Bacteria, Arthropods, and Chlorophyll under Exp dot. Purple blocks (increased growth or flexibility) for Flagellate, Diatoms, Bacteria, Arthropods, and Chlorophyll under Physiol dot.

Panel 4, Nutrients: Light green blocks (mixed response) for Bacteria under obs dot. Dark green blocks (increased growth) for Diatoms (Exp dot), Bacteria (Exp dot), Arthropods (obs dot and Exp dot), and Chlorophyll (obs dot and Exp dot).

Summary of freshwater biotic responses to water availability

The impacts of changes in water supply to freshwater ecosystems mostly influence biota through the dilution of nutrients and minerals, which can limit physiology and growth, depending on local availability. Most knowledge on this subject derives from opportunistic sampling, and more insights could be derived from the application of (field) experimental approaches (Fig. 7).

Summary of biotic responses to UV radiation

UV exposure is harmful for most organisms and is evident in reduced abundance or the adaptations reported for various freshwater organisms (Fig. 7). However, it is unclear whether all such adaptations also affect growth and reproductive output for all freshwater organisms.

Summary of biotic responses to nutrient availability

From sub-Antarctic islands to the McMurdo Dry Valleys, freshwater chlorophyll content, algal growth and microbial communities tend to respond positively to nutrient inputs, indicating that most, if not all, Antarctic freshwater ecosystems are nutrient limited (Fig. 7). This limitation may impair biological responses to climate change. More field experimental work is needed to unravel the underlying mechanisms, limitations and physiological plasticity of freshwater organism responses to nutrient inputs.