Roundup: Decaying Matter, Glacial Bacteria, and CO2 Uptake

Transport of Nutrients and Decaying Matter by Rivers and Streams

From “Intermittent Rivers and Ephemeral Streams”: “The hydrological regimes of most intermittent rivers and ephemeral streams (IRES) include the alternation of wet and dry phases in the stream channel and highly dynamic lateral, vertical, and longitudinal connections with their adjacent ecosystems. Consequently, IRES show a unique ‘biogeochemical heartbeat’ with pulsed temporal and spatial variation in nutrient and organic matter inputs, in-stream processing, and downstream transport. Given that IRES are widespread, their improper consideration may cause inaccurate estimation of nutrient and carbon fluxes in river networks… Our purpose is to contribute to the flourishing knowledge and research on the biogeochemistry of IRES by providing a comprehensive view of nutrient and organic matter dynamics in these ecosystems.”

Read more about the findings here.

Photo of intermittent river in Boliva
An intermittent river in Bolivia (Source: Thibault Datry‏/Twitter).


Glacial Bacteria Originated on Slopes Near Alaskan Glacier

From Microbiology Ecology: “Although microbial communities from many glacial environments have been analyzed, microbes living in the debris atop debris-covered glaciers represent an understudied frontier in the cryosphere. The few previous molecular studies of microbes in supraglacial debris have either had limited phylogenetic resolution, limited spatial resolution (e.g. only one sample site on the glacier) or both. Here, we present the microbiome of a debris-covered glacier across all three domains of life, using a spatially-explicit sampling scheme to characterize the Middle Fork Toklat Glacier’s microbiome from its terminus to sites high on the glacier. Our results show that microbial communities differ across the supraglacial transect, but surprisingly these communities are strongly spatially autocorrelated, suggesting the presence of a supraglacial chronosequence… We use these data to refute the hypothesis that the inhabitants of the glacier are randomly deposited atmospheric microbes, and to provide evidence that succession from a predominantly photosynthetic to a more heterotrophic community is occurring on the glacier.”

Learn more about glacial bacteria here.

Topographic map of bacteria sample sites
Topographic map of bacteria sample sites on the Middle Fork Toklat Glacier (Source: Darcy et al.).


Simulated High Alkalinity Glacial Runoff Increases CO2 Uptake in Alaska

From Geophysical Research Letters: “The Gulf of Alaska (GOA) receives substantial summer freshwater runoff from glacial meltwater. The alkalinity of this runoff is highly dependent on the glacial source and can modify the coastal carbon cycle. We use a regional ocean biogeochemical model to simulate CO2 uptake in the GOA under different alkalinity-loading scenarios. The GOA is identified as a current net sink of carbon, though low-alkalinity tidewater glacial runoff suppresses summer coastal carbon uptake. Our model shows that increasing the alkalinity generates an increase in annual CO2 uptake of 1.9–2.7 TgC/yr. This transition is comparable to a projected change in glacial runoff composition (i.e., from tidewater to land-terminating) due to continued climate warming. Our results demonstrate an important local carbon-climate feedback that can significantly increase coastal carbon uptake via enhanced air-sea exchange, with potential implications to the coastal ecosystems in glaciated areas around the world.”

Read more about the study here.

Photo of the Gulf of Alaska from space
The Gulf of Alaska from space (Source: NASA Goddard Images/Twitter).