In stratified lakes, a large portion of phytoplankton biomass is found—not at the surface, where sampling is easiest—but somewhere down the water column, in what is known as a subsurface chlorophyll maximum (SSCM). Researchers in Global Lake Ecological Observatory Network (GLEON) compared automated high-frequency chlorophyll fluorescence (ChlF) profiles with surface samples and discrete depth profiles. In 7 of the 11 lakes studied, automated sampling captured the presence of SSCM’s that would have been missed by conventional sampling.
How-and when-do ecosystems change character? Are those shifts reversible? And what signs might precede them? Such questions are hard enough to answer in a single place. One might think that incorporating different kinds of ecosystems would only complicate the problem. But a group of scientists in the Long-Term Ecological Research Network is finding a remarkably consistent pattern by combining models and data across several long-term ecological experiments.
Novel ecosystems can emerge through many kinds of changes, including changes in mean climate, species invasions, and increased or decreased variability. Researchers at Jordana Basin LTER have highlighted the role of interannual climate variability in changing the outcome when an exotic grass species invades dry shrubland. Using a process-based model, they predicted three outcomes, depending on the degree of variability and timing relative to invasion.
Climate-change is predicted to have a larger impact on Arctic regions than on temperate ecosystems. As a result, rural communities relying on local wild resources, or subsistence harvesting, are vulnerable to climate-change-induced environmental trends affecting the availability of fish, waterfowl, and other key resources.
Landscape ecologists and nature-lovers are well aware of the way that valleys collect deeper, moister soils than neighboring hill slopes and crests. Now, researchers at Coweeta LTER have have found that cool air, sliding downslope from higher elevations and pooling in mountain valleys, subsidizes productivity in a different way. The cold air drainage was most prevalent at night and in the evenings, so it had little effect on photosynthesis, but reduced plant and soil respiration by about 8 percent. Overall, the authors estimate it boosted annual net carbon uptake by about 15 percent.
Individuals—even individuals of the same species—don’t always respond to a stimulus in the same way. Studying calcification in a key coral species, Acropora pulchra, researchers at the Moorea Coral Reef LTER found greater variety in the corals’ response to temperature than to high levels of CO2 in seawater. Since individual variation is the raw material of evolution, the contrast suggests it may be easier for this coral species to adapt to rising temperatures than to increased ocean acidification.
The global carbon cycle doesn’t have many off-ramps, but the deep ocean is one of them. Researchers with the California Coastal Ecosystem LTER have found that twice as much carbon finds its way to the deep ocean at mesoscale ocean fronts as elsewhere in the ocean.
Snowshoe hares prefer many other plants to white spruce seedlings, but when the population of hares skyrockets—as it does about once a decade—they can decimate even a bumper crop of spruce seedlings. Researchers with the Bonanza Creek LTER reconstructed over 40 years of browsing history by analyzing the age and browse scars of thousands of seedlings and saplings at 18 locations on the floodplain of Alaska’s Tanana River.
Urban watersheds—with their fertilized lawns, street runoff, treated and untreated wastewater—have proportionally more nitrogen flowing through them than undeveloped landscapes do. But are urban streams somehow less able to process that nitrogen? New research out of the Baltimore Ecosystem Study LTER says: no. The study, based on 385 urban watersheds and published in the journal FEMS Microbial Ecology, found that urban watersheds have similar, if not higher, nitrogen processing rates than natural areas.
Wetlands exist on every continent save Antarctica and manifest as a variety of habitats, from salt marshes to mangrove forests. They provide important ecosystem services, such as water purification and flood protection—often tied to their high productivity and diversity.