Arctic Food Web

Arctic Snow Harbours Deadly Fungus

Heavy and prolonged snowfall can bring about unexpected conditions that encourage fungal growth, leading to the death of plants in the Arctic, according to experts.

A new international study confirms that whilst snow has an insulating effect which helps plants to grow bigger, heavy and prolonged snow can, in certain circumstances, also encourage the rapid and extensive growth of killer fungal strains.

The research results, published in the journal Nature Climate Change, show for the first time the potential long term effects of unexpected fungal development on an arctic landscape. Extensive damage to a pervasive species under snowier conditions would leave gaps for another plant to take its place over time but could also alter the food-web for insects, voles, lemmings and their predators.

Co-author of the report, Dr. Robert Baxter, School of Biological and Biomedical Sciences, Durham University, said: "We were surprised to find that this extremely hardy tundra vegetation was killed off by fungal attack.

"In the first few years, as expected, the insulating effect of the snow helped the vegetation to grow, but after six years a tipping point was reached where the fungus spread with great speed and destroyed the plants.

"We need to look more carefully in the future at longer term vegetation and fungus life cycles to see if this is something that could recur and be more destructive over time."

The research team from Durham University, UK; Umeå University, the Swedish University of Agricultural Sciences, Uppsala, Sweden; and the Finnish Forest Research Institute, compared the effects of normal snowfall conditions and increased snow conditions on vegetation.

Researchers used snow fences to maintain increased snow conditions, and found that the fungus, Arwidssonia empetri, increased under heavier and prolonged snow cover killing the majority of the shoots of one of the dominant plant species in that area - the dwarf shrub Empetrum hermaphroditum. The team's unexpected finding followed a decision to keep the experiment running longer than was originally planned.

The researchers believe that the findings highlight unforeseen elements that should be factored into future modelling of the impacts of climate change and its effects on vegetation and food-web chains.

Co-author of the report, Johan Olofsson, Department of Ecology and Environmental Science, Umeå University, Sweden, said: "We set out to look at the effects of climate change and the potential of heavier precipitation and snowfall on plants and the processes that influence growth, decomposition and soil nutrients.

NASA to go boldly … to the Arctic once again | Global Warming

NASA scientists are ready to set sail on the second leg of their voyage to study the changing waters of the Arctic Ocean.

On June 25, the ICESCAPE mission (which stands for “Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment”) resumes its investigation of the impacts of climate change in the Chukchi and Beaufort Seas along Alaska’s western and northern coasts.

Research teams depart from Dutch Harbor, Alaska, aboard the U.S. Coast Guard Cutter Healy. The mission involves 47 scientists who will spend five weeks exploring parts of the Arctic Ocean that were previously too ice-covered for ships to penetrate.

The first leg was completed during the summer of 2010, and the second year of sampling seeks to find year-to-year differences of the Arctic waters. The data gathered during the mission will also be compared to NASA satellite observations of the Arctic Ocean.

Basis of the food web Phytoplankton, microscopic organisms that live in watery environments, are a key focus of the campaign. They form the base of the aquatic food web and cycle Earth’s carbon between the atmosphere and the ocean. They are also vulnerable to climate change. NASA has monitored changes in phytoplankton from space worldwide with the Aqua satellite and the Sea-viewing Wide Field-of-view Sensor.

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“Last year, ICESCAPE nailed down quite a few things in terms of the phytoplankton work,” said the mission’s chief scientist, Kevin Arrigo of Stanford University in Palo Alto, Calif. “We know pretty well now how fast they are growing and what they are responding to. The repeat measurements from this voyage will help us confirm what’s going on.”

The 2010 ICESCAPE campaign gave researchers a glimpse of what might be happening in Barrow Canyon, one of most productive areas for phytoplankton growth in the Beaufort-Chukchi region. While many blooms last just a few weeks before consuming all of the local nutrients and declining, the bloom in Barrow Canyon gets its start in spring and carries on through summer.

Scientists think the extended bloom can be explained by unique patterns in the path and timing of ocean currents in the area. In spring, a stream of water carries nutrients from the Pacific Ocean up through the Bering Strait and delivers them to Barrow Canyon. The water hugs the coast and arrives quickly, providing the nutrients for the bloom to get its start. Two other streams take a more circuitous route and arrive later, sustaining the bloom through summer.

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