Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The Rising Tide of Ocean Plagues: How Humans are Changing the Dynamics of Disease

20.02.2006


A leading group of epidemiologists, veterinarians and ecologists report that humans are affecting the oceans in ways that are changing the dynamics of disease. Previously harmless pathogens are becoming killers when combined with contaminants; “good” parasites that invisibly control the balance of species in an ecosystem are disappearing; and changes in sea surface temperature can trigger cholera outbreaks thousands of miles away.



“Human activities are knocking things out of balance,” says Andrew Dobson of Princeton University. “For some pathogens, we’re seeing nasty synergistic effects with contaminants, such as PCBs. Paradoxically, diseases also play an important role in healthy ecosystem functioning. These changes tend to slip under the radar screen until they show up in ecological cascades that lead to wildlife and human health problems.”

Lethal Domoic Acid Poses New Threats to Sea Lions & Humans


Scientists studying sea lions in California are seeing an increase in the number of animals affected by domoic acid, a toxic compound produced by specific types of algal blooms. In high doses, domoic acid is fatal. At lower doses, it can trigger miscarriages and cause gradual, irreversible decay of brain tissue.

Many scientists agree that increases in algal blooms in California and around the world are caused by a combination of factors, including agricultural run-off, oceanographic properties, and global warming. Many of these blooms produce chemicals that are dangerous to humans when concentrated in the food chain. In the case of domoic acid, both shellfish and fish can concentrate the toxin.

Scientists first saw domoic acid poisoning in 1998, when over 70 sea lions died in one weekend. “We thought at the time that it was linked to the fact that it was an El Nino year, but we’ve seen it every year since then,” says Frances Gulland of The Marine Mammal Center in Sausalito, California. “It’s a big mystery.”

In the last five years, over 1000 animals have died from domoic acid poisoning, and there has been an increase in the number and extent of harmful algal blooms that produce the compound.

“Sea lions eat the same foods we do, but more of them – foods like anchovies, squid, salmon, and mussels – we may see the effects of domoic acid in them before we see it people,” says Gulland. Researchers are already seeing signs of serious health problems, such as miscarriages and epilepsy, in sea lions. “Sea lions may be an early warning sign for humans,” she says.

While harmful algal blooms are often termed “red tides” because of the color of some algal species, we cannot always see these blooms just by looking at the water. To detect these harmful blooms, scientists monitor plankton and domoic acid levels in mussels. In California, harvesting of mussels and other shellfish is banned when their tissues contain levels of domoic acid over the deadly 200 parts per million. At lower levels, however, there is no public warning system.

“I wouldn’t eat shellfish during any sort of harmful algal bloom, especially not if I was pregnant,” says Gulland.

Sugar Kills – New Clues in the Mystery of Coral Diseases

In the struggle to understand and prevent coral diseases, scientists are finding that sugars released in sewage and agricultural run-off play an unexpected role in killing corals.

In the 1970’s there were only a few diseases documented on coral reefs. Today there are over thirty, and the numbers are increasing exponentially. “The scary thing is that even in the Great Barrier Reef, one of the most protected reefs in the world, researchers are seeing more diseases every time they look,” says David Kline of the Smithsonian Tropical Research Institute.

Nailing down the causes of these diseases has been difficult. Kline and his colleagues, Forest Rohwer and Nancy Knowlton, examine a variety of stressors to understand the origin and spread of coral disease.

“It’s unexpected. The water quality components governments typically monitor – nitrogen and phosphorus – aren’t killing the coral directly,” says Kline. “It’s sugars making bacteria on corals grow out of control.”

Bacterial communities live in healthy corals and are beneficial when kept in check: they may actually protect corals from disease and likely collect and concentrate needed nutrients from the water. But, like an infected cut, rapid growth of bacteria is problematic. It can cause disease or make corals more susceptible to new pathogens.

Sugars that promote this dangerous overgrowth reach the ocean directly from human waste and agricultural run-off, but are also produced by fleshy algae. This link to algae reveals an escalating feedback loop. Nitrogen and phosphorus pollution in run-off enhances the growth of algae that produce simple sugars as they photosynthesize. The sugars, in turn, promote the growth of bacteria, which kills or weakens the coral. This leaves more room for the algae to take over, smothering corals and increasing sugar production, starting the cycle over again and rapidly changing reefs to fields of algae.

In healthy systems, some of this algal growth would be kept in check by fish and other algae-eaters, but overfishing has wiped out many of these populations. “Corals are tough, they’ve been around for millions of years. But multiple threats such as pollution, overfishing, and global warming may prove to be too much for them,” Kline says. “I’ve seen Staghorn reefs go from brilliant areas that form a nursery for fish, to completely wiped out, in a matter of months.”

The good news is that sugar levels can be monitored and significantly reduced. According to recent reports, eighty percent of sewage in the Caribbean is released directly to the water untreated. “I think we can save reefs in the Caribbean and the Pacific,” says Kline. “But we need proper water treatment systems throughout the world and large enough networks of marine reserves.”

Parasites – Losing Them Can Be Hazardous to Your Health

We typically think of parasites as energy-sucking creatures synonymous with ill-health, but high abundance of parasites in coastal environments can actually be a positive indicator of ecosystem health.

“Parasites are absolutely a bad thing if you’re the individual infected by them,” says Kevin Lafferty of the US Geological Survey. “But they are a very natural component of ecosystems. Parasitism is the most popular animal lifestyle on the planet.”

Because parasites have complex life cycles, often relying on a variety of animals and interactions to survive, they are especially sensitive to environmental change. This susceptibility of parasite populations allows scientists to use the abundance of these small animals as an early detection and monitoring device: a change in the ecosystem will show up as an increase or decrease of parasites before scientists can see those changes in populations of host animals like fish or birds.

Lafferty and his colleagues study small worms called trematodes to monitor the health of salt marshes and wetlands in California. One particular worm starts its life in a snail where it reproduces and is released to the water as a free-swimming larvae that burrows into the tissue of clams, crabs, or fish. Once there, it waits for its new host to be eaten by a bird. In fish, it can hasten the process, swimming to the brain of the fish where it creates a cyst that causes the fish to flash on its side at the surface of the water – making it an easy target for nearby birds. Ultimately, the parasite returns to the water in the feces of birds and starts all over with the next snail encounter.

“Trematodes require all of the pieces of the puzzle to complete their life cycle – when we see a lot of parasites in an estuary, we know it’s in good shape. For example, an estuary with high infection rates tells you that it is visited by many birds, and many types of birds,” explains Lafferty.

If habitat loss, fishing, hunting, or pollution degrades the system, scientists will see a decline in parasite populations. In the end, reductions in parasite populations may be an equally important indicator of ecosystem malfunction as the more publicly alarming increases in disease.

“Often, we don’t realize we miss infectious diseases until we have invasive species that become pests without their natural enemies,” explains Lafferty. “Parasites act like thermostats – when a species becomes abundant it is more susceptible to infectious diseases. The disease acts like a safety valve, keeping populations in check.”

Climate Variability & Cholera

We are also affecting human health on a global scale by changing the physical factors that influence the spread of disease. In the latest evidence of our ties to the ocean, researchers have discovered how changes in sea surface temperature in the Pacific Ocean are linked to cholera epidemics across the globe in Bangladesh.

To predict and prepare for future outbreaks, cholera expert Mercedes Pascual and her colleagues are studying cholera outbreaks in Bangladesh, where extensive health records stretching back to the late 1800’s (when the British Empire was carefully keeping track of disease threats in its colony) and bi-weekly case reports taken during a 1966 surveillance program document disease trends in unique detail. A waterborne diarrheal disease, cholera is still a serious health concern in many areas of the world, including parts of India, South America, Bangladesh, and Africa. It takes a large economic toll on poor communities and, if untreated, can kill in as little as 24 hours.

Pascual and her team have discovered that cholera transmission is highest during high rain and flooding, when sanitary conditions tend to breakdown and people are forced into tight quarters. And now they have reason to believe that these high rain events are linked to warmer ocean conditions in the Pacific during El Nino events. This newly revealed connection to remote sea surface temperatures via increased local rainfall is especially striking because it points to the possibility of using ocean temperatures as an early warning system to predict and prevent disease outbreaks.

“We can think of changes to the oceans locally, but in terms of human health we have to look globally,” says Pascual. “This is a global connection. As we change ocean properties through climate change, remote consequences are likely to arise – we may not even know what they are yet.”

“As children, if we cut ourselves at the beach, our mothers told us to wash it in the ocean - seawater was always perceived to be clean and healthy. We are seeing ominous signs that this is changing - surfers in California are now advised to have regular hepatitis inoculations and you really don’t want to expose an open wound to near shore water,” says Dobson. “We should begin to worry deeply about the health of the oceans.”

Jessica Brown | alfa
Further information:
http://www.seaweb.org

More articles from Ecology, The Environment and Conservation:

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Comet or asteroid? Hubble discovers that a unique object is a binary

21.09.2017 | Physics and Astronomy

Cnidarians remotely control bacteria

21.09.2017 | Life Sciences

Monitoring the heart's mitochondria to predict cardiac arrest?

21.09.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>