Tag Archives: pesticides

Fish in polluted water cannot smell

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From Scientific American:

Fish Cannot Smell in Polluted Waters

Fish in lakes tainted with heavy metals are losing their sense of smell

By Brian Bienkowski and Environmental Health News

Perca flavescens Yellow Perch

When lakes recover from metal contamination, fish can recover their sense of smell. Pictured: Yellow Perch (Perca flavescens). Image: Flickr/Matt Tillett

Fish in lakes tainted with metals are losing their sense of smell, stoking concern among experts that the problem could devastate populations.

But if the fish can just get into cleaner water – even if they’ve been exposed to pollutants their whole life – they start sniffing things properly again, according to new research out of Canada.

Fish use their sense of smell to find mates and food, and to avoid getting eaten. It helps them navigate their often murky world, and it is necessary for their growth and survival. But when metals contact fish nostrils, the neurons shut down to protect the brain.

Metals already have been linked to impaired reproduction and growth in fish but now they are proving to be “covert toxics,” said Keith Tierney, a University of Alberta assistant professor who did not participate in the new study. “If you can’t smell food, or avoid predators, you’re more likely to die – simple as that.”

Greg Pyle, a professor at the University of Lethbridge in Alberta, said he suspects that impaired sense of smell “has meaningful and profound effects” on many fish species. It may be jeopardizing entire populations of fish, including some endangered species.

“We’ve tested everything from leeches to water fleas to several species of fish,” Pyle said. “Every species and every metal we’ve observed has had effects at low, environmentally relevant concentrations.”

Most contaminated lakes have a metallic mix, making it hard to tease out which pollutants are to blame.

In the latest study, Pyle and his team of researchers took yellow perch that lived in Ontario lakes contaminated with mercury, nickel, copper, iron and manganese, and put them in a cleaner lake. Within 24 hours of basking in the clean water, the fish regained their sense of smell.

This shows “fish from metal contaminated lakes have the ability to recover once the lake recovers,” the authors wrote in the paper published in last month’s Ecotoxicology and Environmental Safety journal.

The researchers used wild fish from two lakes with metal contamination (Ramsey and Hannah lakes) and from a cleaner one (Geneva Lake). Ramsey and Hannah, located in Sudbury, Ontario, are polluted from more than a century of mining, particularly with nickel. Hannah Lake is one of the worst-polluted lakes in the area, while Ramsey is similar to other North American lakes near industrial areas. Geneva Lake is far enough northwest to escape most contaminants.

Just as the clean lake revived the sense of smell for the Ramsey and Hannah fish, Geneva Lake’s perch had decreased smell after just 24 hours of hanging out in the dirtier lakes. Their response times to substances that smelled like their food dropped 75 to 59 percent.

Similar results have been reported with minnows and perch, with metals apparently reducing their ability to escape predators.

Some metals attack specific neurons in the nostrils that respond to certain smells, Pyle said. Nickel targets the neurons that help fish smell food, while copper – at low concentrations – targets the neurons that help fish avoid predators. At higher concentrations, copper impairs their smell for everything.

“Copper is a poster child for water pollution,” said Nathaniel Scholz, an ecotoxicology program manager at the National Oceanic and Atmospheric Administration‘s Northwest Fisheries Science Center. “Copper is intensively used as a pesticide, fungicide…It’s found in cars, in boat paint, so boatyards are often contaminated. And it’s often found in industrial discharge and near legacy mining operations. It’s a rare pollutant that’s both agricultural and urban.”

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Neonicotinoids kill grassland birds

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This video from the USA is called Grassland Bird Talk.

From Wildlife Extra:

Pesticides, including neonicotinoids, leading cause of decline of grassland birds

New study finds pesticides leading cause of grassland bird declines

February 2013. A new study led by a preeminent Canadian toxicologist identifies acutely toxic pesticides as the most likely leading cause of the widespread decline in grassland bird numbers in the United States, a finding that challenges the widely-held assumption that loss of habitat is the primary cause of those population declines.

The scientific assessment, which looked at data over a 23-year period – from 1980 to 2003, was conducted by Dr. Pierre Mineau, recently retired from Environment Canada, and Mélanie Whiteside of Health Canada.

The study looked at five potential causes of grassland bird declines besides lethal pesticide risk: change in cropped pasture such as hay or alfalfa production, farming intensity or the proportion of agricultural land that is actively cropped, herbicide use, overall insecticide use, and change in permanent pasture and rangeland.

Spotlight on acutely toxic insecticides used on cropland

“What this study suggests is that we need to start paying a lot more attention to the use of pesticides if we want to reverse, halt or simply slow the very significant downward trend in grassland bird populations. Our study put the spotlight on acutely toxic insecticides used on cropland starting after the Second World War and persisting to this day – albeit at a lower level. The data suggest that loss of birds in agricultural fields is more than an unfortunate consequence of pest control; it may drive bird populations to local extinction,” Mineau said.

Many grassland bird species have undergone range contractions or population declines in recent decades. In fact, analyses of North American birds indicate that these birds are declining faster than birds from other biomes. Habitat protection has long been considered a central pillar in efforts to stem the decline of grassland bird species, such as the Vesper Sparrow, the Ring-necked Pheasant, and the Horned Lark.

Loss of habitat

“We are still concerned about loss of habitat in agriculture, range management, and urban development,” said Cynthia Palmer, manager of the Pesticides Program at American Bird Conservancy, a leading U.S. bird conservation organization. “This study by no means diminishes the importance of habitat fragmentation and degradation. But it suggests that we also need to rein in the use of lethal pesticides in agriculture, and that we need to be especially careful about any new pesticides we introduce into these ecosystems such as the neonicotinoid insecticides. It reminds us that the poisonings of birds and other wildlife chronicled a half century ago by famed biologist and author Rachel Carson are by no means a thing of the past.”

Lethal pesticides nearly four times more likely to be associated with population declines

The researchers focused on the extent to which lethal pesticides, such as organophosphate and carbamate insecticides, are responsible for the decline in grassland bird populations. The study found that lethal pesticides were nearly four times more likely to be associated with population declines than the next most likely contributor, changes in cropped pasture – an important component of habitat loss associated with agricultural lands.

The publication says that “…..large quantities of products of very high toxicity to birds have been used for decades despite evidence that poisonings were frequent even when products were applied according to label directions.”

The authors argue that only a small proportion of total cropland needs to be treated with a dangerous pesticide to affect overall bird population trends. The production of alfalfa stands out for its strikingly high chemical load, constituting the third highest lethal risk of any crop based on toxic insecticide use. Pesticide drift from croplands is also affecting birds that favor the adjoining grasslands.

Biggest declines

Using data from the U.S. Geological Service Breeding Bird Survey for the years 1980 to 2003, the study found that declines of grassland birds were much more likely in states with high use of toxic insecticides lethal to birds. The species with the greatest number of declines included the Eastern Meadowlark (declining in 33 States), the Grasshopper Sparrow (25 States), the Horned Lark (25 States), the Ring-necked Pheasant (19 States) and the Vesper Sparrow (18 States). The states with the greatest number of declining grassland species were Minnesota (12 species), Wisconsin (11 species), and Illinois, Michigan, Montana, Nebraska and New York, all with nine species.

Neonicotinoids

The current study relies on pesticide data from the 1980s and early 1990s, a time when organophosphates such as diazinon and chlorpyrifos, and carbamates such as carbofuran and methomyl, were still largely in vogue. Since that time, a new class of insecticides, the neonicotinoids, have soared to the top of global pesticide markets. Unfortunately, a major toxicological assessment soon to be released by American Bird Conservancy puts to rest any notion that birds and other organisms will fare much better under the new pesticide regime.

The study was published in PLOS One, the online peer-reviewed scientific journal.

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