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Macroalgal forests dominate shallow hard bottom areas along the northern portion of the Western Antarctic Peninsula (WAP). Macroalgal biomass and diversity are known to be dramatically lower in the southern WAP and at similar latitudes around Antarctica, but few reports detail the distributions of macroalgae or associated macroinvertebrates in the central WAP. We used satellite imagery to identify 14 sites differing in sea ice coverage but similar in terms of turbidity along the central WAP. Fleshy macroalgal cover was strongly, negatively correlated with ice concentration, but there was no significant correlation between macroinvertebrate cover and sea ice. Overall community (all organisms) diversity correlated negatively with sea ice concentration and positively with fleshy macroalgal cover, which ranged from around zero at high ice sites to 80% at the lowest ice sites. Nonparametric, multivariate analyses resulted in clustering of macroalgal assemblages across most of the northern sites of the study area, although they differed greatly with respect to macroalgal percent cover and diversity. Analyses of the overall communities resulted in three site clusters corresponding to high, medium, and low fleshy macroalgal cover. At most northern sites, macroalgal cover was similar across depths, but macroalgal and macroinvertebrate distributions suggested increasing effects of ice scour in shallower depths towards the south. Hindcast projections based on correlations of ice and macroalgal cover data suggest that macroalgal cover at many sites could have been varying substantially over the past 40 years. Similarly, based on predicted likely sea ice decreases by 2100, projected increases in macroalgal cover at sites that currently have high ice cover and low macroalgal cover are substantial, often with only a future 15% decrease in sea ice. Such changes would have important ramifications to future benthic communities and to understanding how Antarctic macroalgae may contribute to future blue carbon sequestration.
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Nutritional consistency of macroalgae across a sea ice cover gradient along the Western Antarctic Peninsula
Abstract Sea ice can profoundly influence photosynthetic organisms by altering subsurface irradiance, but it is susceptible to changes in the climate. The patterns and timing of sea ice cover can vary on a monthly to annual timescale in small sub‐regions of the Western Antarctic Peninsula (WAP). During the latter part of the 20th century, sea ice coverage significantly decreased in the WAP, a trend that aligns with warming in this area. Macroalgal biochemical components are impacted by light availability, often showing a close relationship between photosynthesis and biochemical compositions. We used satellite imagery of annual sea ice duration and extent as well as water turbidity during ice‐free periods to identify 14 study sites that differed dramatically in sea ice coverage but were similar in terms of turbidity along the central WAP between 68° S and 64° S. The common macroalgal speciesDesmarestia menziesii,Himantothallus grandifolius,Sarcopeltis antarctica, andIridaeasp. were collected by scuba divers between 5 m and 35 m depth at each site where they occurred, for later biochemical analyses. Overall percentages of major biochemical components as well as carbon and nitrogen percentages and C:N were determined and correlated with four different sea ice indices. Surprisingly, most of the chemical components were not significantly correlated with sea ice cover. The few significant correlations varied between species and chemical components. This indicates that although patterns of sea ice coverage have major implications for macroalgal abundance, on a per‐biomass basis, sea ice coverage does not impact the nutritional contributions of macroalgae to food webs.
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- Award ID(s):
- 1744550
- PAR ID:
- 10578678
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Phycology
- Volume:
- 61
- Issue:
- 1
- ISSN:
- 0022-3646
- Format(s):
- Medium: X Size: p. 218-230
- Size(s):
- p. 218-230
- Sponsoring Org:
- National Science Foundation
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