Algal bloom species with two deadly toxins could disrupt marine food web

Aug 15, 2012 By Christine Buckley
The algal bloom species Alexandrium, which looks like Saturn in the lower-left, and several of its single-celled predators. Photo courtesy of Hans Dam

(Phys.org) -- When tiny aquatic organisms reproduce in large amounts, algal blooms occur that take over portions of open water up to hundreds of miles in area.

And when these oceanic happen to be the toxic kind, they can be deadly to other living things crossing their path.

One of the most poisonous and abundant of these plankton, the species Alexandrium tamarense, produces paralytic shellfish toxin (PST), a that can result in death when ingested in large amounts by , including humans.

Now, Professor Hans Dam and his research group in the Department of have shown that this microscopic alga also produces a second kind of deadly toxin, one that attacks some of the ’s tiny predators and, along with PST, could ultimately upset entire marine food chains. Dam published his findings in the May 2012 issue of the journal Aquatic Microbial Ecology.

“The amazing thing is, when you look at these algae under a microscope, they’re so beautiful – but they’re so deadly,” says Dam. “We call them the beautiful assassins.”

Like plants, these one-celled organisms make their own food from the light of the sun. The Alexandrium species lives in cold seawater in the northern and southern hemispheres, and is found from the Long Island Sound up to the northernmost Canadian borders. In 2005, a major bloom – sometimes referred to as a red tide – occurred throughout the northeast coast, severely affecting the Cape Cod area.

Hans Dam in a lab in Chile, where he is working with researchers at the University of Los Lagos to understand how Alexandrium may affect important commercial species. Photo courtesy of Hans Dam

In small numbers, Alexandrium is virtually harmless to humans, says Dam. But when they’re eaten by clams, mussels, or other microorganisms – which are then eaten by small crustaceans, which are in turn eaten by larger crustaceans or fish – the toxins can build up in large amounts. So in some parts of the world, eating contaminated lobsters, clams, and fish has led to illness or death.

However, says Dam, PST only affects animals that have central nervous systems.

“This toxin blocks sodium channels in anything that has a well-developed nervous system,” he says. “But most of the organisms in the ocean are not those kinds of organisms. They’re single-celled, similar to the algae themselves, and they don’t have a well-developed nervous system.”

Scientists had begun to notice that even though Alexandrium’s toxin isn’t supposed to affect single-celled animals, when the alga was in the vicinity of some of its one-celled predators, some of those predators got sick and died. Dam’s post-doctoral researcher Hayley Flores showed in laboratory experiments that in fact the alga produces a different toxin, called a species, that kills its predators by popping their cell membrane.

“If you only have one cell, losing your cell membrane is all it takes to kill you,” says Dam. “This new mechanism of toxicity, combined with the other, is pretty evil.”

Dam speculates that this ability to harm both large and small oceanic predators could lead to disruptions in the marine food web during large Alexandrium blooms.

“These small predators that are being affected by the reactive oxygen species are the things that typically eat large amounts of the algae and keep them from growing like crazy,” says Dam. “This brings up a whole new line of inquiry for us: What will actually control these algae in the future?”

Dam notes that although harmful have been linked to human activities, such as pollution runoff from rivers, there are many different factors that could affect the blooms, and scientists still aren’t sure exactly how they begin. He speculates that the algae may have become more toxic over time, which has led to their proliferation.

His group will next try to understand how the alga produces the reactive and whether it also affects multicellular animals. He’s also working with researchers at the University of Los Lagos in Chile to understand how Alexandrium may affect important commercial species such as salmon and king crab. And his group recently received funding from Connecticut Sea Grant to study the effects of temperature on plankton in the Long Island Sound.

Dam says that even though humans have little to fear, the marine world could see shifts based on just this one group of species.

“If it’s killing multicellular animals with one toxin and small protists with another,” he says, “it could be the killer of the ocean world.”

Explore further: Citizen scientists match research tool when counting sharks

More information: Full study: www.int-res.com/abstracts/ame/v66/n2/p199-209/

add to favorites email to friend print save as pdf

Related Stories

Toxic red tides: Scientists track neurotoxin-producing algae

Sep 30, 2011

which can increase the amount of harmful toxins in the shellfish that California residents consume — ramping up in frequency and severity locally, scientists at USC have developed a new algae monitoring method in hopes ...

Loss of rare species can harm ecosystems

Mar 19, 2012

(PhysOrg.com) -- Here’s another reason to cheer for the little guy. A new study co-authored by Matthew Bracken, assistant professor of biology in Northeastern’s College of Science, has found that ...

Recommended for you

Citizen scientists match research tool when counting sharks

10 hours ago

Shark data collected by citizen scientists may be as reliable as data collected using automated tools, according to results published April 23, 2014, in the open access journal PLOS ONE by Gabriel Vianna from The University of Wes ...

Researchers detail newly discovered deer migration

17 hours ago

A team of researchers including University of Wyoming scientists has documented the longest migration of mule deer ever recorded, the latest development in an initiative to understand and conserve ungulate ...

How Australia got the hump with one million feral camels

18 hours ago

A new study by a University of Exeter researcher has shed light on how an estimated one million-strong population of wild camels thriving in Australia's remote outback have become reviled as pests and culled ...

Former Iron Curtain still barrier for deer

Apr 23, 2014

The Iron Curtain was traced by an electrified barbed-wire fence that isolated the communist world from the West. It was an impenetrable Cold War barrier—and for some inhabitants of the Czech Republic it ...

Humpback protections downgrade clears way for pipeline

Apr 22, 2014

Environmentalist activists on Tuesday decried Canada's downgrading of humpback whale protections, suggesting the decision was fast-tracked to clear a major hurdle to constructing a pipeline to the Pacific ...

Maine baby lobster decline could end high catches

Apr 22, 2014

Scientists say the number of baby lobsters settling off the rocky coast of Maine continues to steadily decline—possibly foreshadowing an end to the recent record catches that have boosted New England's lobster fishery.

User comments : 0

More news stories