From Ice to Ecosystems: NSF Backs ACRC Study of Glacial Carbon Sources
Glaciers are rapidly melting across the globe, yet there is still much that we do not understand about their impacts on downstream ecosystems. While increased volumes of water released from melting glaciers may be apparent to most people, glacier meltwater also contains large quantities of dissolved organic material, known as DOM, which contains carbon that is exported downstream. Dissolved organic matter derived from the glacial ecosystems is important to downstream food webs due to its high “bioavailability” to stream microbes compared to other sources of carbon in the environment (e.g., from soils in deglaciated portions of the watershed).
ACRC researcher Dr. Amy Holt describes this phenomenon as “a buffet where stream microbes are the diners choosing from a selection of foods [or carbon sources]. Some are more delicious than others [in this case, the glacially-derived carbon in DOM], and microbes keep going back for more”. This ‘tasty’ glacially-derived carbon comes from both modern and ancient sources, such as the deposition of fossil fuel combustion byproducts, or carbon-fixed by microorganisms like algae living on the glacier’s surface.
However, it is currently unknown whether modern or ancient carbon is the source of the high bioavailability of glacier DOM. ACRC researchers Jason Fellman, Eran Hood, and Amy Holt recently received a National Science Foundation grant for $250,000 from the Division of Environmental Biology in order to investigate the composition of DOM exported from glacial rivers, and understand which carbon source(s) drive bioavailability.
The project aims to determine whether the increased bioavailability of glacial carbon arises from modern microbial production on the glacier surface or industrial-era atmospheric deposition of fossil fuel-derived carbon. The researchers will achieve this using carbon isotopic analyses, radiocarbon dating, and a novel respiratory carbon recovery system to directly analyze the age and source of glacier DOM used by aquatic microbes. Ultimately, these results will provide critical insights into how glaciers function within the carbon cycle and how their loss may affect downstream ecosystems. Fellman, Hood, and Holt plan to share their findings at future installations of the Mendenhall Glacial Visitor Center Fireside Chat and Evening at Egan Lecture Series, so stay tuned to hear whether ancient or modern carbon is the secret ingredient in a glacial river’s tasty recipe!
