Invasive seaweed shelters tiny native critters on Georgia mudflats
Oct24

Invasive seaweed shelters tiny native critters on Georgia mudflats

On the tidal mudflats of Georgia and South Carolina, the red Japanese seaweed Gracilaria vermiculophylla is gaining a foothold where no native seaweeds live. Only debris and straggles of dead marsh grass used to break the expanse of mud at low tide. Crabs, shrimp, and small crustaceans mob the seaweed in abundance. What makes it so popular? Not its food value. On mudflats near Savannah, Ga., Jeffrey Wright and colleagues found that the tiny native crustacean Gammarus mucronatus (one of the 9,500 species of amphipod, which includes sand fleas) does not eat much of the seaweed. Rather, its attraction is structural. The seaweed protects the small crustaceans from predators at high tide and from the dry heat of the flats at low tide. G. mucronatus was up to 100 times as abundant on seaweed invaded mudflats, the authors report in the October issue of Ecology, out this week. The arrival of an aggressive invader disrupts the food webs and physical and chemical characteristics of the environment it enters. Disruption is often bad for native species that get shaded, crowded, or eaten by the invader, and reports of the disastrous consequences of invasive species have grown familiar. But the story for individual species is more complicated, as the presence of the invader is sometimes a benefit, either as a new source of food or, as in this case, of shelter. Engineering or food? Mechanisms of facilitation by a habitat-forming invasive seaweed (2014) JT Wright, JE Byers, JL DeVore, and E Sotka. Ecology 95(10): 2699-2706.  [open...

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Pikas act as ‘climate indicators’
Aug01

Pikas act as ‘climate indicators’

The Oscar-winning Disney movie “Frozen” includes a living snowman character named Olaf that would melt and die under the 70 degree temperatures humans and many other animals prefer. Of course, there are a number of species in the animal kingdom sensitive to heat conditions humans generally find preferable. Some of these are fellow mammals , but not all, are limited to the extreme cold Arctic and Antarctic climates. At home in loose rock areas in alpine and subalpine mountain regions, American pikas are one such species. Though they bear a resemblance to rodents, pikas are actually members of the lagomorpha order, which includes rabbits and hares. Their North American range includes British Columbia in Canada and the US states of California, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, Utah, Washington and Wyoming. Much like the Disney’s Olaf, pikas cannot endure the mid-to-upper 70s temperatures we humans deem comfortably warm for more than a short period.  In fact, pikas would die if exposed to temperatures above 77 degrees for longer than six hours. Alas, the thick-furry coats that keep them snug through a cold-mountain winter prevent them from ever taking in the rays on a warm summer day at the beach. This heat intolerance largely prevents their existence below 8,202 feet in the regions of New Mexico, Nevada and southern California. And yet, this distinct temperature sensitivity makes them interesting specimens for studying the profound impacts of climate change on ecosystems. During the most recent edition of the Ecologist Goes to Washington podcast, 2014 Ecological Society of America Graduate Student Policy Award winner Johanna Varner (University of Utah) discusses her research into pikas and their importance as climate indicators. A recent study found that extinction rates for American pikas have increased five-fold in the last 10 years while the rate at which the pikas are moving up mountain slopes has increased 11-fold. The US Fish and Wildlife Service ruled in 2010 that the American pika does not warrant Endangered Species Act protection, but this could change if this population decline significantly worsens. Luckily, some pikas have proven to be adaptable in their foraging mannerisms. One population of pikas in Oregon’s Columbia River Gorge have adapted to warming temperatures by increasingly eating (and re-ingesting) moss.  Eating moss, which grows in the shadier parts of the animal’s habitat, helps the pikas avoid the blistering (deadly in their case) summer sun while also helping minimize their becoming a victim of predation. Aside from their obvious appeal as “charismatic fauna”, deserving of Disney characterizations in their own right, some might question why research into preserving pikas is important. As Varner notes in the podcast,...

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Poo pump: whales as ecosystem engineers
Jul03

Poo pump: whales as ecosystem engineers

The brown cloud bursts forth among the pod of sperm whales, dispersing a wealth of nitrogen and iron into the surface waters over the deep ocean. The whale-borne windfall is eagerly received by phytoplankton, the microorganisms at the foundation of the ocean food chain, which quickly capitalize on the surge of fuel. Poop packs a powerful energetic punch. And an adult sperm whale packs a lot of poo. Enough to dump 50 metric tons of iron into the ocean every year, according to Trish Lavery and colleagues at Flinders University in Adelaide. Sperm whale poop is particularly rich in iron thanks to the whales preferred diet of squid and fish. Scarce iron is essential to the growth of phytoplankton, the photosynthesizing primary producers of the sea. (The other major source of iron in the ocean is wind-borne desert dust.) Sperm whales dive over 2000 meters to hunt squid, but defecate at the surface, transporting nutrients between ocean realms. Blue whales also act as a “whale pump”, diving to 150 meters to capture krill (small, shrimp-like crustaceans, which in turn feed on phytoplankton). The turbulence of diving, surfacing and exhaling stirs the water column as well. In their migrations, the baleen whales transport nutrients latitudinally, from the food rich summer feeding grounds of the polar oceans to the safer, but hungry, tropical waters. Mother Humpbacks fast through birth and lactation, burning through their summer fat stores, and leaving behind the waste products of their metabolism in the warm coastal waters. Great whales exert powerful effects on the environment as predators, prey, and bodies sinking to a final rest in the deep dark, sometimes boosting the productivity of ecosystems in non-obvious ways. The mass disappearance of the great whales in the last few centuries, leaving them at a tenth of their historical numbers, has likely changed the functioning of ocean itself. A group of marine ecology heavyweights led by Joe Roman review the science on the influence of whale on ocean ecosystems for Frontiers in Ecology and the Environment in an article published online today. Read more from the University of Vermont news site.   Joe Roman, James A Estes, Lyne Morissette, Craig Smith, Daniel Costa, James McCarthy, JB Nation, Stephen Nicol, Andrew Pershing, and Victor Smetacek (2014). Whales as marine ecosystem engineers. Frontiers in Ecology and the Environment (e-View 3 July; scheduled for August print edition) http://dx.doi.org/10.1890/130220  ...

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National parks aren’t doing the trick in Kenya

Elephants have changed the ecology of Amboseli and other national parks in Kenya. Credit: David Western Research in PLoS ONE today shows that animals in Kenya’s national parks are declining at the same rate as the same species outside the parks.  This means, potentially, that the protection of animals in safe spaces may not lead to their recovery or success. David Western, the author and founder/director of the African Conservation Centre in Nairobi, said in a statement that pressures around the parks are affecting the wildlife in the parks. When protected areas are delineated, human-made infrastructure, such as agriculture, can jut up against it. Many large mammals migrate seasonally, and the small areas within the parks can thwart their travels. The parks, said Western, were formed around places where people saw large aggregations of mammals, including elephants, giraffes and impala. This technique ignored the animals’ season migrations, mostly because people just didn’t know where the animals were migrating to.  What’s more, elephants are effective ecosystem engineers. Said Western: “Elephants need a lot of space. They move around. But now that they have been limited to smaller areas, they’re taking out the woody vegetation and reducing the overall biodiversity in the national parks. We’re seeing throughout our parks in Kenya a change from woody habitats to grassland habitats. As a result, we’re losing the species that thrive in woody areas, such as giraffe, lesser kudu and impala.” Another reason these national park populations might be declining, said Western, is that local farmers perceive it as a threat. Because they can’t use the lands to grow food, they willingly invite poachers onto the land.  In fact, the biggest parks are experiencing the worst declines, possibly because they’re in pastoral lands surrounded by farmers. In smaller parks near cities, Western said, the population is more educated and financially stable, so they don’t view the parks negatively. Western suggests that to end farmers’ antagonism toward national parks, the government should share some of the financial benefits with local communities. Read more in the PLoS ONE (open access). Western, D., Russell, S., & Cuthill, I. (2009). The Status of Wildlife in Protected Areas Compared to Non-Protected Areas of Kenya PLoS ONE, 4 (7) DOI:...

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Evolution and ecosystem engineers

Evolutionary biologists agree that the natural environment shapes the evolution of life. A study published in Nature today, however, finds that the evolution of a species can also have big impacts on the surrounding environment. Threespine stickleback are famous as an example of rapid, adaptive radiation. These small freshwater fish have evolved in the lakes of British Columbia to have very different lifestyles.  In large lakes, there are two varieties:  The benthic variety hangs out at the bottom of its lake and feeds on invertebrates that live in the sand, while the limnetic variety stays in the water column and eats floating plankton.  Strong competition for food is thought to have produced these two species from a common ancestor in as little as 10,000 years, which is practically light speed in evolutionary time. A third generalist variety lives in smaller lakes where the competition for food is not as vicious. Adept at both feeding strategies, these fish are thought to have undergone little adaptive evolution, and therefore are similar to the other forms’ common ancestor. Luke Harmon of the University of Idaho and his colleagues created miniature replicas of the lakes in their laboratory and observed the effects introduced fish had on their surroundings.  In experiments including the two specialized species, the researchers detected more dissolved organic carbon in the water.  They found that two parts didn’t make a whole: Even though the specialists were covering the same foraging area as the generalist species, something unbeknownst to the researchers was different about their foraging habits. This dissolved carbon inhibited light penetration through the water, disrupting the growth of aquatic plants and other carbon-producing organisms. Harmon concluded that the evolution of two varieties would likely have very different effects on the environment, and that the specialists could be seen as ecosystem engineers. The authors write that these results could have far-reaching effects on other species; they write that “adaptive radiation may modify the environmental conditions of ecosystems and shape the selective pressures of other species.” Harmon, L., Matthews, B., Roches, S., Chase, J., Shurin, J., & Schluter, D. (2009). Evolutionary diversification in stickleback affects ecosystem functioning Nature DOI:...

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