Nav: Home

It's a fish eat tree world

March 22, 2017

(Millbrook, NY) Most of the planet's freshwater stores are found in the northern hemisphere, a region that is changing rapidly in response to human activity and shifting climatic trends. An international team of scientists analyzed 147 northern lakes and found that many rely on nutrients from tree leaves, pine needles, and other land-grown plants to feed aquatic life.

The study, published today in Science Advances, offers the most comprehensive analysis to-date on terrestrial subsidies to lake food webs. Findings underscore the interconnectedness of terrestrial and aquatic systems and deliver a key message: to maintain lakes in the northern hemisphere, managers must understand how landscape changes - such as forest clearing or agriculture - impact lake food webs.

Dr. Christopher Solomon, a scientist at the Cary Institute of Ecosystem Studies and a coauthor on the paper, explains, "Because terrestrial support of aquatic food webs differs across lakes, there has been some controversy about its relative importance. We set out to reveal the degree to which freshwater organisms rely on terrestrial nutrients to survive, and the factors that influence variability between lakes in a broad geographic area."

To uncover the link between watersheds and lake food webs, the research team focused their attention on zooplankton. These tiny animals form the base of the aquatic food web and are essential to the survival of fish and other aquatic life.

More than 550 zooplankton samples were taken at lakes across a range of conditions, from boreal to subtropics. Many of these sites are clustered in the Great Lakes region and throughout northern Europe. Stable isotope techniques were used to determine if zooplankton in a given sample were feeding primarily on aquatic plants, or instead focusing on leaves, pine needles, and other organic material that washes into lakes from their watersheds.

Potential nutrient sources - such as leaf litter, soil organic matter, phytoplankton, and algae - contain unique isotopic signatures. Zooplankton carry the isotopic signature of the food source they derive most of their nutrients from. In half of the zooplankton samples, the animals were made up of at least 42% terrestrially derived material. In some instances, terrestrial sources accounted for up to 83% of total zooplankton biomass.

Solomon comments, "If you are what you eat, then many lake-dwelling fish are, in part, made up of plants from their watersheds. Understanding how lakes are tied to the land is vital to effective freshwater management."

To that end, the team also investigated how physical characteristics of the land draining into lakes influence terrestrial subsidies to lake food webs. Differences in tree cover, vegetation density, soil carbon concentrations, lake area, and lake perimeter can impact the amount of terrestrial matter available to aquatic life.

When lakes were nestled into landscapes with abundant trees and vegetation, the team found that zooplankton relied more on land-generated nutrients. Lakes with small surface areas relative to the length of their shorelines were also more reliant on terrestrial inputs. At these sites, changes to shoreline vegetation, such as clearing a tract of forest for a recreational parking lot, could have a significant negative impact on lake life.

But not all lakes are reliant on terrestrial inputs. In lakes with plentiful algae, animals often favor these resources over terrestrial alternatives because they are higher in fatty acids and macronutrients. Land use that increases terrestrial organic matter in these lakes, such as reforesting a cleared site, could create shade that reduces algae growth, forcing organisms to shift their feeding to terrestrial sources.

Lead author Dr. Andrew Tanentzap of the Department of Plant Sciences at the University of Cambridge notes, "Everything is more connected than we think it is. Our goal is to help identify which lakes are reliant on terrestrial subsidies - and which aren't - so that land use planning accounts for impacts to downstream waters."

"Management depends on what you want to achieve. If the system is one in which algal growth is a problem, a good way to combat that is with terrestrial resources that shade algal growth, but at the same time can support zooplankton," Tanentzap explains. Creating riparian buffers could be an effective strategy for managing terrestrial input in freshwater systems.
-end-
The Cary Institute of Ecosystem Studies is one of the world's leading independent environmental research organizations. Areas of expertise include disease ecology, forest and freshwater health, climate change, urban ecology, and invasive species. Since 1983, Cary Institute scientists have produced the unbiased research needed to inform effective management and policy decisions.

Cary Institute of Ecosystem Studies

Related Algae Articles:

Algae: The final frontier
Algae dominate the oceans that cover nearly three-quarters of our planet, and produce half of the oxygen that we breathe.
Photosynthesis in the dark? Unraveling the mystery of algae evolution
Researchers compared the photosynthetic regulation in glaucophytes with that in cyanobacteria, to elucidate the changes caused by symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways.
Making oil from algae -- towards more efficient biofuels
The mechanism behind oil synthesis within microalgae cells has been revealed by a Japanese research team.
Hydrogen production: This is how green algae assemble their enzymes
Researchers at Ruhr-Universit├Ąt Bochum have analyzed how green algae manufacture complex components of a hydrogen-producing enzyme.
A better way to farm algae
Researchers at Syracuse University have developed a method that improves the growth of microalgae, which could have big implications for production of biofuels and other valuable chemicals.
More Algae News and Algae Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...