Rising Temperatures Threaten Biodiversity Along the Antarctic Peninsula

The 800-mile-long Antarctica Peninsula, which extends northward off of western Antarctica, is one of the fastest warming regions on the planet. The peninsula’s climate has warmed 3 degrees Celsius over the last 50 years, according to the British Antarctic Survey.

The Antarctic Peninsula, boxed in red (Source: United States Geological Survey)

Hundreds of glaciers, such as Crane and Sheldon, scatter the peninsula’s icy terrain. Rising temperatures have led to significant glacial melting on the Antarctic Peninsula. Large-scale glacial meltwater flows into nearby seas resulting in ecosystem disruption, which increases biodiversity vulnerability. Plant and animal species that cannot adapt to the changing conditions face extinction on the peninsula.

In an article published in Limnology and Oceanography, researchers examine how the changing climate of the Antarctic Peninsula impacts the biodiversity and decomposition of macroalgal communities.

Aquatic macroalgae are large, photosynthetic planets that can be seen without the use of a microscope. Macroalgae include a variety of seaweed species that are usually attached to the sea floor.

All three types of macroalgae, brown, red, and green algae, inhabit the coastal waters off of the Antarctic Peninsula.

When storms, erosion, and ice movement occur, macroalgae detach from the seafloor and become free-floating. Free-floating seaweed gets eaten, washes ashore, or decomposes in the ocean. Excess free-floating seaweed leads to biodiversity loss within the local ecosystem.

Red algae (Source: Peter Southwood, Creative Commons)

Lead-author Ulrike Braeckman from the Marine Biology Research Group at Ghent University and twelve additional authors from research institutions in Germany, Argentina, the Netherlands, and Belgium examined the accumulation and degradation of free-floating seaweed over time. Braeckman and her colleagues traveled to King George Island, which is located to the west of the northernmost tip of the Antarctic Peninsula, to complete the study.

Specifically, the researchers analyzed two native seaweed species—red algae, Palmaria decipiens, and brown algae, Desmarestia anceps.

To examine the degradation rates in a lab setting, the researchers sampled sediment cores from the research site. Each core was roughly 9.8 inches long. Next, freeze-dried, shredded versions of the macroalgae and seawater were added to the sediment cores. Seawater was replaced every second day to avoid metabolite accumulation or improper chemical breakdown.

The researchers used stable isotope labeling of carbon and nitrogen, two chemical elements found in decomposed plant material, to understand the seaweed degradation rates. Stable isotope labeling is a valuable research technique used to measures the ratios of chemical elements.

Brown algae, Lobophora variegata (Source: John Turnbull, Flickr)

The results of the study indicate that Palmaria decipiens degraded quicker than Desmarestia anceps. In the research setting: Plamaria decipiens degraded in 31 days while Desmarestia anceps degraded in 48 days. The results confirmed the researchers’ initial hypothesis.

Increasing glacier melting results in expanding macroalgae growth associated with detritus [decomposition] accumulation at the seafloor in this area …the degradation of the macroalgal detritus [decomposition] in this study evolved over time, and the patterns were indeed species specific”, state Braeckman et al.

Therefore, some macroalgae species such as Palmaria decipiens decompose faster than other macroalgae species, which makes these species more susceptible to extinction on the Antarctic Peninsula. Climate change on the peninsula will likely contribute to future biodiversity loss as species struggle to adjust to the altered environment.  

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