Marsh Pollutants Have Drastic Adverse Effects on Survival of Sea Anemones

Researchers from the Marine Biological Laboratory in the U.S. have released a study that shows sea anemones are under significant threat from the current levels of pollutants in their natural habitats.

Nematostella Vectensis. Image courtesy of the Smithsonian Environmental Research Center

The sea anemone Nematostella Vectensis has a special place in research. It is very useful for studies in evolutionary, developmental, and regenerative biology.

The organism is renowned for living its entire life in the same location while using a combination of cnidocytes (stinging cells) and tentacles to get its sustenance. It constantly tries to adapt to environmental changes to survive. But its ability to continue doing that is now under a major threat from pollutants.

Researchers found that the levels of pollutants in America’s East Coast, a native habitat for these organisms have severely affected their growth, development, and feeding ability adversely.

“The numbers of Nematostella in the wild have been dramatically decreasing over time,” said Karen Echeverri, the study’s senior author.

This was the first study to assess the impact that pollutants are having on the growth, development, and microbiome of these organisms.

Nematostella enjoys less protection in the U.S. than they currently do in the United Kingdom.

Impact of pollution on Nematostella’s growth and microbiome

In this study, researchers directed their attention to phthalates or plasticizers, chemicals commonly used in plastics, and certain consumer products. They also focused on potassium nitrate, which is found in fertilizers. These chemicals regularly find their way into oceans and marshes.

The team exposed Nematostella embryos to levels of phthalates and nitrate that are commonly observed in coastal settings. A drastic reduction in body size was seen after two weeks of exposure.

In addition, the organisms showed fewer tentacles. Researchers noticed that tentacles that managed to grow were deformed or irregular lengthwise or in number.

It did not stop there. The exposure caused Nematostella to have fewer stinging cells. This reduces their ability for self-defense and for getting food, making them more likely to die.

This research is remarkable in that shows the impact of pollutants on animal microbiomes. After a 10-day exposure to pollutants, microbiomes were sequenced and some classes of microbes were found to have become more dominant.

Echeverri said it was not wholly clear how the microbiome changes can affect the animal’s physiology.

Determining health effects

Microbiome changes such as those seen in this study can be an indicator of effects on host health. Previous studies in other animals, including humans, suggest this.

The severe growth defects observed in Nematostella are comparable to those reported in other studies on the effects of phthalates on the development of embryos in vertebrates, including zebrafish and frogs. Among them are defects of cells belonging to the ectodermal lineage, such as the stinging cells.

Research has also shown that the chemicals can affect fertility and the endocrine system in certain species.

Echeverri stated that the next thing to be done is to try and discover a link between microbiome changes in Nematostella and their development.