How has marsh pollution affected the survival of sea anemones?

marsh pollution, sea anemones

Scientists say the stationary sea anemone, Nematostella, has been decreasing in numbers – as it becomes severely impacted by pollution

The sea anemone, Nematostella, burrows into salt marsh sediments and stays there for life, with its ‘stinging cells’, which hurl toxins into passing prey, it can immobilise morsels and snatch it with its tentacles. This study finds the Nematostella are declining in numbers and changing biologically due to pollution in their habitats.

These stationary marine organisms don’t travel the ocean, but instead spend their lives rooted in one spot, evolving to impressive methods in catching prey. Its stationary lifecycle can easily be impacted by food shortages and changes.

Has pollution threatened the protected species?

The study from the Marine Biological Laboratory (MBL), discovered that Nematostella’s growth, development, and feeding ability have been severely affected by common pollutants found in one of its native habitats, the marshlands along the U.S. East Coast.

Focusing on phthalates – phthalic acid esters or plasticizers – which are chemicals that are widely used in plastic packaging and other consumer products that wash into the ocean, as well as potassium nitrate, which enters marshes through runoff from lawn fertilizers, they found that the marine organisms are declining in numbers due to this threat of toxic chemicals which are affecting their life patterns and food accessibility.

Nematostella embryos exhibited a gross decrease in body size two weeks after exposure to phthalate and nitrate concentrations, commonly found in coastal environments. The animals additionally had fewer tentacles – and of the tentacles that did grow, were misshapen or uneven in length or number.

The pollution exposure harshly reduced the number of stinging cells (cnidocytes) the Nematostellas have, which they use as a defence mechanism and to capture food.

Senior author Karen Echeverri, associate scientist in the MBL’s Bell Center for Regenerative Biology and Tissue Engineering, said: “The numbers of Nematostella in the wild have been dramatically decreasing over time. They have what we call adaptive plasticity; they are resilient to change. But we think there is a limit to that resilience. And as you bring in more pollution, they reach that limit of resilience much faster.”

“At a certain point, the animals just die, because they can’t defend themselves or feed themselves properly.”

Due to the Nematostella’s sessile, or stationary, nature, it must continually acclimate to environmental changes. These changes can involve outside factors like temperature and water salinity.

The team sequenced the microbiomes of animals after 10 days of pollutant exposure, led by MBL scientists Mitchell Sogin and Emil Ruff, they found the alterations in the microbiome can serve as sentinels of change in the health of the host, as shown by prior studies in other animals, including corals and humans.

Other studies of the effects of phthalates on embryonic development in vertebrates, including subjects like frogs and zebrafish, recognised defects in body growth similar to the changes in the Nematostella. These changes include slower body growth and defects of cells in the ectodermal lineage (such as the cnidocytes). Impacts on the endocrine system and on fertility have also been documented in other species due to the effects of pollution.

Echeverri added: “Certain classes of microbes became much more dominant after exposure. How this affects the physiology of the animal, we don’t completely know yet. A next step is to link changes in the Nematostella microbiome to changes in the animal’s development.”


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