Warming Waters Unexpectedly Alters Growth of Antarctica’s Sea Life

By Gene Yang ’19

Figure 1. The benthic zone, which includes the sea floor, sediment, and surrounding waters, is the lowest ecological level in a body of water.

Figure 1. The benthic zone, which includes the sea floor, sediment, and surrounding waters, is the lowest ecological level in a body of water.

In shallow Antarctic waters, a nine-month long study was the first of its kind to artificially warm conditions in the sea floor to predicted climate change levels, and in doing so, the researchers saw an increase in the growth rates of select species.

Scientists placed artificial “settlement panels” on the sea floor of shallow Antarctic waters. The composition of these panels mimicked the ground sediment, and all except the control panels radiated heat that simulated either +1°C or +2°C environments—the predicted increase in sea temperature due to climate change in 50 and 100 years, respectively. Over a period of nine months, various sea floor species colonized these panels, and the rate of population growth, percentage area colonized, and biodiversity of each panel was recorded.

Growth rates in the +1°C panels increased far beyond expected fundamental biological temperature relationships. This long standing relationship, established by Arrhenius more than 100 years ago, predicts an increase in growth rate of 7% to 12% per 1°C warming. However, in the +1°C panels, the spatially dominant bryozoan Fenestrulina regula doubled its growth rate in just two months, and populations of the spirorbid worm Romanchella perrieri was on average 70% larger than the control. The +1°C panels also had significantly different species composition relative to its control, with an analysis of similarity (ANOSIM) producing an R statistic of 0.33 (p = 0.03). While nearly all species in the +2°C panels experienced the same increase in growth rate as species in the +1°C panel, results were more variable because an ANOSIM test on species composition yielded no significant differences.

Although the rapid growth of a select few species did lead to slightly lower biodiversity, the increase in growth rates suggest that populations in these benthonic zones have the potential to adapt well to climate change. However, shallow benthic communities and their relationship to the larger ocean is still poorly understood. This research was the first of its kind to pioneer such a community-based in situ study, and more like minded research will be needed to better understand broader interactions within the marine ecosystem.

 

References

  1. G. V. Jaramillo, et al., Warming by 1°C drives species and assemblage level responses in Antarctica’s marine shallows. Current Biology 24, 1-8 (2017). doi: 10.1016/j.cub.2017.07.048.
  2. Image retrieved from: http://mail.tehnomaster.info/wppoimg-ocean-floor-depth-map.asp
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