ENVIRONMENT

As the ocean temperature rises, it may be the little things that make the biggest difference to the survival and resilience of all living things. (Hakai)

What are limpets?

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

 

Discussion Ideas

• New research indicates the lowly limpet may be one of the most efficient adapters to climate change. What are limpets?
  • Limpets are a type of small aquatic snail (mollusk) easily spotted by their telltale conical shape. Like most gastropods, limpets have a single strong, muscular foot. This allows them to adhere to a surface (usually a rock) and withstand the punishing turbulence of ocean waves. Some limpets have gills, while others have a primitive lung.
  • Almost all limpets feed on algae, although some also feed on microscopic detritus.
  • Limpets live in both freshwater and marine habitats. The marine habitat occupied by the limpets in the study is the intertidal zone, but other marine limpets live in deeper water. Some species even live in deep-sea hydrothermal vents.

 

• How was the new study carried out?
  • From Hakai: Scientists placed four sets of plates in the intertidal zone of Salt Spring Island, British Columbia, Canada. Scientists restricted limpets’ access to half of the plates, while the animals were free to graze on the other half. Scientists also simulated the effects of ocean warming by tinting some of the plates black to attract the sun’s heat. For 16 months, researchers tracked plants and animals established themselves on the four different plates.

 

• What was the outcome?
  • Pretty straightforward: “when limpets had access to plates, there was no effect of warming on community composition.” (!)
    • Researchers found that “when limpets’ access is restricted, the artificially warmed intertidal ecosystem collapsed—the diversity of life [was] largely replaced by a mat of microalgae. Limpets with access to the plates, however, maintained a healthier ecological community, even in a warming environment.”

 

• So, what is it about limpets that helps maintain a diverse and complex community, even when their environment warms?
  • Diet! “Limpets eat huge amounts of microalgae … This [feeding behavior, called “limpet grazing”] clears the terrain for a variety of life. ‘When limpets are allowed in, they make space for things like barnacles, and then those barnacles in turn create little condos for other animals to live in,’” says lead researcher Rebecca L. Kordas. Other animals include snails, amphipods, and isopods.
    • Barnacles, amphipods (similar to shrimp) and macroalgae, in turn, are food for consumers such as fish and crustaceans. This creates what the authors call a healthy herbivory community.

 

• The Hakai magazine article calls limpets “ecosystem engineers,” while the research calls barnacles “habitat modifiers.” What are ecosystem engineers or habitat modifiers? Take a look at the “Ecosystem Engineers” section of our “keystone species” resource for some help.
  • Ecosystem engineers are organisms that modify, create, and maintain habitats.
  • Ecosystem engineers modify their habitats through their own biology (autogenic engineers) or by physically changing biotic and abiotic factors in the environment (allogenic engineers).

 

• Are the limpets and barnacles in the study examples of autogenic or allogenic engineers? Warning: Trick question.
  • allogenic engineers. The limpets and barnacles in the study consistently clear the rocky shore for other organisms to colonize, thereby modifying the surrounding biotic and abiotic factors in their environment.
  • autogenic engineers. Limpets provide a living substrate on which micro-habitats of algae and barnacles can survive. (Take a look at the top photo on this page for a beautiful example of this!)

 

• What are some other examples of ecosystem engineers? Read through the Hakai article and our own Ecosystem Engineers section for some help.
  • beavers. Beavers are a classic example of ecosystem engineers. Beavers help maintain woodland ecosystems by thinning out older trees and allowing young saplings to grow. Converting these trees into timber for dams radically alters woodland meadows and streams, changing them into wetland habitats. (allogenic engineer)
  • sea stars. Sea stars, the first animal identified as a keystone species, are a major predator of mussels—in many ways, sea stars are a balance to the limpets in the new study. Without sea stars, mussels take over habitat and crowd out other species, including algae that support communities of sea snails, limpets, and bivalves. Lacking sea stars, the tidal plain’s biodiversity is radically reduced. (allogenic engineer)
  • wolves. Starting in the 1990s, the U.S. government began reintroducing wolves to the Greater Yellowstone Ecosystem. The results have been noteworthy. Elk populations have shrunk, willow heights have increased, and beaver and songbird populations have recovered. (allogenic engineer)
  • corals. As corals grow, they are a living part of the environment, providing food and shelter to other organisms. The hard exoskeletons left as corals die continue to define and modify the ecosystem. (autogenic engineer)
  • kudzu. Invasive species, like the so-called “vine that ate the South” can be dangerous ecosystem engineers. Lacking natural predators or abiotic factors to constrain them, these introduced species modify the existing environment in ways that inhibit the growth of the indigenous ecosystem. Kudzu regularly outcompetes native species for space and nutrients. As it crowds out native species, kudzu limits the pollinators, insects, and bird species that inhabit an area. (allogenic engineer)
  • humans. Human activity alters the environment in every way possible. (allogenic engineer)

 

TEACHERS TOOLKIT

Hakai: How Tiny Limpets Do the Heavy Lifting of Climate Resilience

Nat Geo: What is a keystone species?

Nat Geo: Marine Communities

Nat Geo: Limpets Sink Their Teeth In

(extra credit!) Science Advances: Herbivory enables marine communities to resist warming