• Energy Research

AbstractEndemic Antarctic macroalgae are especially adapted to live in extreme Antarctic conditions. Their potential biogeographic distribution niche is primarily controlled by the photoperiodic regime and seawater temperatures, since these parameters regulate growth, reproduction, and survival during the entire life cycle. Here we analyzed the upper survival temperature (UST) of juvenile sporophytes and the temperature range for sporophyte formation from gametophytes of Desmarestia menziesii, one of the dominant endemic Antarctic brown algal species. This process is a missing link to better evaluate the full biogeographical niche of this species. Two laboratory experiments were conducted. First, growth and maximum quantum yield of juvenile sporophytes were analyzed under a temperature gradient (0, 5, 10, 12, 13, 14, 15, and 16 °C) in a 16:8 h light:dark (LD) regime (Antarctic spring condition) for 2 weeks. Second, the formation of sporophytes from gametophytes (as a proxy of gametophyte reproduction) was evaluated during a 7 weeks period under a temperature gradient (0, 4, 8, 12, and 16 °C), and two different photoperiods: 6:18 h LD regime simulating winter conditions and a light regime simulating the Antarctic shift from winter to spring by gradually increasing the light period from 7.5:16.5 h LD (late winter) to 18.5:5.5 h LD (late spring). Sporophytes of D. menziesii were able to grow and survive up to 14 °C for 2 weeks without visible signs of morphological damage. Thus, this species shows the highest UST of all endemic Antarctic Desmarestiales species. In turn, gametophyte reproduction solely took place at 0 °C but not at 4–8 °C. The number of emerging sporophytes was six times higher under the light regime simulating the transition from winter to spring than under constant short day winter conditions. There was a negative relationship between the number of sporophytes formed and the gametophyte density at the beginning of the experiment, which provides evidence that gametophyte density exerts some control upon reproduction in D. menziesii. Results strongly indicate that although sporophytes and gametophytes may survive in warmer temperatures, the northernmost distribution limit of D. menziesii in South Georgia Islands is set by the low temperature requirements for gametophyte reproduction. Hence, global warming could have an impact on the distribution of this and other Antarctic species, by influencing their growth and reproduction.

A sublittoral transect (P3) in the North of Helgoland that had been investigated ~40 years earlier by Lüning (1970) was traversed again. Scuba dives were carried out between 13.07.2005 and 25.08.2005. For each sampling point, time, date and coordinates were given as well as the depth in m mean low water spring tide. 0.25 m² frames were used to obtain the species composition, total fresh mass and total dry mass. In addition, 1 m² frames were used to record the kelp community by counting the individuals and measuring kelp stipe length, kelp blade area, kelp blade fresh mass, kelp age and fresh mass of epiphytes on the kelp stipes. Equal Location IDs represent the same frame. Gehling (2006) figure 3 shows the sampling location as green lines. The Loc ID is the frame no. In frame 1, 10 species were found and weight was taken. In frame 4, 13 species were found. Weight was taken from all species and in addition, stipe and blade weight of L. hyperborea was measured as well as single weights from each individual called Individual code: 1-18, as there where 18 L. hyperborea.

The leaf area of macroalgae was surveyed at Hansneset, Blomstrand in Kongsfjorden, Svalbard, from the 2.5 m down to 15 m depth in summer 2012 and 2021. Our goal was to document changes in Arctic kelp forests dynamics in an Arctic fjord system influenced by glacial melt by repeatedly sampling the same site in a standardized manner. As ocean temperatures in the Arctic have risen substantially and underwater light climate continuously deteriorated over this time period we observed alterations in the seaweed community, especially kelps as major coastal foundation species.This data contains the leaf area index measurements (leaf area [m²]) per species per quadrat (Replicate) at a series of specific depths (Depth [m]) for the years 2012 and 2021 taken at Hansneset, Kongsfjorden, Svalbard. Within the species column there is a 'Digitate kelps' value. This is due to the complication of the visual similarity of Laminaria digitata and Hedophyllum nigripes. Because these are field data, and the distinction between these species requires genetic lab work, the exact species identification is not possible so they are listed with the WORMS code for Laminariales. Historically these kelps were considered Laminaria digitata.

A survey for macroalgal fresh biomass was performed in the high, mid and low intertidal zone at five sites along the fjord axis of Porsangerfjorden in July 2022. This dataset is part of a space-for-time comparison between low-Arctic Porsangerfjorden and high-Arctic Kongsfjorden. The aim was to document differences in macroalgal biomass and community composition between two Arctic fjord systems at different stages of cryosphere loss to understand how benthic vegetation in the high-Arctic will likely develop in the future. The data contains a fresh biomass data for a range of macroalgal taxa in the intertidal. Macroalgae were identified to the lowest taxonomic level possible. The taxonomic 'Class' of the taxon is provided to indicate to which type of canopy-forming Fucales or which macroalgal lineage the understory intertidal taxon belongs to. Within the taxon column there is a 'Fucus vesiculosus spiralis distichus', a 'Acrosiphonia Spongomorpha' and a 'Dictiosiphon Chordaria Stictyosiphon' value. Because these are field data, and the distinction between these species requires genetic lab work, the exact species identification is not possible.

Macroalgal fresh biomass was collected in the subtidal fringe level at Guovolesuolu in Porsangerfjorden in July 2022. This dataset is part of a space-for-time comparison between low-Arctic Porsangerfjorden and high-Arctic Kongsfjorden. The aim was to document differences in macroalgal biomass and community composition between two Arctic fjord systems at different stages of cryosphere loss to understand how benthic vegetation in the high-Arctic will likely develop in the future. The data contains fresh biomass data for a range of macroalgal taxa at the subtidal fringe level. Macroalgae were identified to the lowest taxonomic level possible. The taxonomic 'Class' of the species is provided, as well as a 'Category' that shows if the species is a kelp, or was found in the understory of the canopy-forming kelps. Within the taxon column there is a 'Fucus vesiculosus spiralis distichus', a 'Acrosiphonia Spongomorpha' and a 'Dictiosiphon Chordaria Stictyosiphon' value. Because these are field data, and the distinction between these species requires genetic lab work, the exact species identification is not possible.

A survey for macroalgal fresh biomass was performed in the high, mid and low intertidal zone at six sites along the fjord axis of Kongsfjorden in June-July 2024. This dataset is part of a space-for-time comparison between low-Arctic Porsangerfjorden in Northern-Norway and high-Arctic Kongsfjorden in Svalbard. The aim was to document differences in macroalgal biomass and community composition between two Arctic fjord systems at different stages of cryosphere loss to understand how benthic vegetation in the high-Arctic will likely develop in the future. The data contains a fresh biomass data for a range of macroalgal taxa in the intertidal. Macroalgae were identified to the lowest taxonomic level possible. The taxonomic 'Class' of the taxon is provided to indicate if it is a canopy-forming Fucus distichus or which macroalgae lineage the understory taxon belongs to. Within the taxon column there is a 'Dictiosiphon Chordaria', a 'Planosiphon Scytosiphon' and a 'Urospora Ulothrix' value. Because these are field data, and the distinction between these species requires genetic lab work, the exact species identification is not possible.

Due to the global rise in temperature, recent studies predict species shifts towards higher latitudes. The temperate kelp Laminaria hyperborea (Phaeophyceae) is an abundant European bioengineering species that is widely distributed between northern Portugal and northern Norway, however not yet found in the High Arctic. To investigate its ability of the species to invade the high latitudes under past, present and future temperature scenarios, we conducted a long-term multi-factorial experiment using tissue of adult sporophytes of L. hyperborea collected from Porsangerfjorden, Norway. The samples were exposed to three different photoperiods (PolarNight, PolarDay, LongDay) at 0, 5 and 10°C for three months. The maximum photosynthetic quantum yield of photosystem II (Fv/Fm; Imaging-PAM, Walz GmbH Mess- und Regeltechnik, Effeltrich, Germany) was monitored once a week. For monitoring of potential growth, the size of the algal discs was photographed every two weeks and analyzed with ImageJ (Version 1.52a). Every four weeks, subsamples for monitoring the dry weight and for the biochemical analyses were taken. Laminarin content was determined following via enzymatic digestion. Mannitol concentration was analyzed using a HPLC. Phlorotannins were analyzed following the photometric Folin-Ciocalteu method. Absolut pigment concentrations were also analyzed using a HPLC and pool sizes, the de-epoxidation state of the xanthophyll cycle (DPS), and the ratios calculated afterwards. Treatment details – multi-factorial experiment--------------------------------------------------------------------------------------------------Laminaria hyperborea samples from the Porsangerfjorden, Finmark, NorwayPolarDay: 24:0 light:dark-cycle; 30–35 μmol photons m-2 s-1 (PAR)LongDay: 18:6 light:dark-cycle; 30–35 μmol photons m-2 s-1 (PAR)PolarNight: 0:24 light:dark-cycle; total darknessSample: These values are used to differentiate multiple similar samples within the same replicate. They do not denote a relationship between weeks. E.g. Sample #3 from week 0 (w0) of Replicate 2, is not necessarily a sample of the same organism for Sample #3 from week 1 (w1) of Replicate 2. Meaning that Samples should not be taken as time series of measures of the same organism through time.w0 = week 0 (start)w4 = week 4w8 = week 8w12 = week 12 (end)set-up:2-L aerated Kautex bottles, 1/40 PES, medium changed 2x/week

Surveys were performed for macroalgae fresh biomass, dry biomass, leaf area index and kelp morphometry at Hansneset, Blomstrand in Kongsfjorden, Svalbard, from the infralittoral fringe down to 15 m depth in June - August 2021. This dataset is part of a time series currently spanning over 25 years and complements the studies conducted in 1996/98 (Hop et al., 2012, doi:10.1515/bot-2012-0097) and 2012-14 (Bartsch et al., 2016, doi:10.1007/s00300-015-1870-1). The aim was to document changes in Arctic kelp forests dynamics in an Arctic fjord system influenced by glacial melt by repeatedly sampling the same site in a standardized manner. As ocean temperatures in the Arctic have risen substantially and underwater light climate continuously deteriorated over this time period, alterations were observed in the seaweed community, especially kelps as major coastal foundation species.The data file contains a range of standard morphometric measurements of individual kelps (and associated seaweeds) by depth, quadrat (replicate), and species. The taxonomic 'Class' of the species is provided, as well as a 'Category' that shows if the species is a kelp, or was found in the understory of the kelp forest. Within the species column there is a 'Digitate kelps' value. This is due to the complication of the visual similarity of Laminaria digitata and Hedophyllum nigripes. Because these are field data, and the distinction between these species requires genetic lab work, the exact species identification is not possible here. Historically these kelps were considered Laminaria digitata. In some rare cases, the leaf area and/or Total FW and Total DW were measured together for multiple specimens (especially juveniles together with others). When this was done, a comment can be found for that row of data.