{"id":599841,"date":"2023-01-20T17:00:00","date_gmt":"2023-01-20T23:00:00","guid":{"rendered":"https:\/\/news.sellorbuyhomefast.com\/index.php\/2023\/01\/20\/plastic-pollution-and-prescription-drugs-are-making-fish-act-erratically\/"},"modified":"2023-01-20T17:00:00","modified_gmt":"2023-01-20T23:00:00","slug":"plastic-pollution-and-prescription-drugs-are-making-fish-act-erratically","status":"publish","type":"post","link":"https:\/\/newsycanuse.com\/index.php\/2023\/01\/20\/plastic-pollution-and-prescription-drugs-are-making-fish-act-erratically\/","title":{"rendered":"Plastic, pollution, and prescription drugs are making fish act erratically"},"content":{"rendered":"
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This article was originally featured on Undark<\/a>.<\/em><\/p>\n

The world\u2019s aquatic habitats<\/span> are a heady brew of pollutants. An estimated 14 million tons<\/a> of plastic enter the ocean as trash<\/a> each year. Further inland, more than 40 percent<\/a> of the world\u2019s rivers contain a pharmacopeia from humans, including antidepressants and painkillers. Heavy metals like mercury<\/a> from industrial waste<\/a> can also make an appearance. And agricultural fertilizer<\/a> can leach from the soil into rivers, eventually reaching the ocean.<\/p>\n

There are an estimated 20,000 species<\/a> of fish in the world \u2014 and possibly many more. They and many other organisms that live in \u201ccontaminated systems are contaminated with a cocktail of chemicals,\u201d said Michael Bertram, a behavioral ecologist at the Swedish University of Agricultural Studies.<\/p>\n

Bertram and other researchers are increasingly finding that these compounds may alter fish behavior. In some experiments, the pollutants appear to alter how fish socialize, either by exposing them to psychoactive drugs or by altering their natural development, which may change how they swim together and mate. Others appear to make fish take more risks which, in the wild, could increase their odds of getting unceremoniously taken out by predators.<\/p>\n

The effects of the pollution, according to researchers working in the field, still have many unknowns. This is due in part to the vast number of variables in real ecosystems, which can limit scientists\u2019 abilities to infer how pollutants impact fish in the wild, said Quentin Petitjean, a postdoctoral researcher in environmental sciences at Institut Sophia Agrobiotech in France, and co-author of a 2020 paper<\/a> that looked at existing literature on pollution and fish behavior. \u201cIn the wild, fish and other organisms are exposed to a plethora of stressors,\u201d he said.<\/p>\n

Still, these altered behaviors could have big impacts, according to Bertram. Like many living things, fish are important parts of their ecosystems, and changing their behavior could hinder or alter their roles in unexpected ways. For instance one study<\/a> suggests that various chemical pollutants and microplastics can impact the boldness of prey fish species. Although the authors note that this isn\u2019t likely to lead to population collapse, these \u201csubtle behavior modifications\u201d could reduce fish biomass, alter their size, and ultimately harm predators as well. Just this one effect, they add, \u201cmay be a hidden mechanism behind ecosystem structure changes in both freshwater and marine ecosystems.\u201d<\/p>\n

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B<\/span>ut humans have<\/span> a funny way of showing their appreciation. One example: People regularly flush psychoactive substances, which then find their way into aquatic ecosystems. In 2021, Bertram and a team of researchers published a paper<\/a> digging into how a common antidepressant, fluoxetine, better known under the brand name Prozac, affected guppies\u2019 propensity for shoaling, or swimming in groups. Over two years, the team exposed groups of guppies to different concentrations of fluoxetine: a low concentration (commonly seen in the wild), a high concentration (representative of an extremely contaminated ecosystem), and no fluoxetine at all.<\/p>\n

At the high exposure concentration, the guppies appeared to be more social, spending more time shoaling. However, this was only the case in of male-female pairs, not when the fish swam solo. Previous research<\/a> by Bertram and colleagues shows that the medication increases the amount of time guppy males spend pursuing females. \u201cBeing intensely courted\u201d by males, Bertram said, the females will preferentially choose the larger school to distract them and \u201cto avoid this incessant mating behavior.\u201d<\/p>\n

While drugs like Prozac are designed to change brain function, there are other, perhaps less obvious ways pollution can change behavior. For instance, pollutants may alter the microbiome<\/a>, the collection of microscopic organisms like fungi and bacteria that exist on or in an organism. In humans, disruptions of microbial life have been linked to disorders such as autism spectrum disorder<\/a>, dementia<\/a>, or even simply cognitive impairment<\/a>. Research published in 2022 suggests that fish brains may also rely on the collection of minuscule organisms<\/a>.<\/p>\n

In the study, researchers worked with two groups of zebrafish embryos that they had rendered germ-free, functionally stripping them of microbes. Into the containers holding one group of embryos, the team immediately introduced water from a tank with full-grown zebrafish to give the disinfected population a microbiome. After a week, they did the same for the other group.<\/p>\n

After yet another week, the researchers ran a series of experiments, putting two fish from the same group in neighboring tanks to see if they would swim alongside each other, a shoaling behavior<\/a> previously identified.<\/p>\n

The fish deprived of an early life microbiome spent much less time doing this behavior than those in the control group. Of the 54 control fish, nearly 80 percent spent their time near the divider between the tanks, compared to around 65 percent of the 67 in the other group. Exposure to microbes early in life is important for the development of social behavior, said Judith Eisen, a neuroscientist and one of the paper\u2019s authors.<\/p>\n

The researchers also looked at the brains of the fish using powerful microscopes. Normally, cells called microglia move from the gut to the brain early in the fishes\u2019 lives, Eisen said, around the time their microbiome starts to develop. The fish that lived without microbiomes for a week, she and the team found, had fewer microglia in a particular brain region which has been previously linked to the shoaling behavior. In normal brains (including human<\/a> ones), these cells perform synaptic pruning<\/a>, which clears away weaker or less used connections.<\/p>\n

Of course, the germ-free state of those zebrafish, Eisen said, would not exist in nature. However, some human pollutants like pesticides<\/a>, microplastics<\/a>, and metals<\/a> like cadmium appear to alter fish microbiomes. Considering shoaling is often a protective behavior, a diminished shoaling response may cause problems in the wild. \u201cIf it doesn\u2019t want to hang out with other fish \u2014 that might open it up to predation,\u201d Eisen said.<\/p>\n

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