Sea anemone’s survival rates drop drastically amid current marsh pollution

New research conducted by the Marine Biological Laboratory (MBL), reveals that sea anemone Nematostella’s growth, development, and feeding ability are drastically impacted by present levels of common pollutants found in one of its native habitats, the US East Coast.

The sea anemone

Stationary marine organisms that spend their lives rooted to one location have evolved in order to capture prey. Sea anemone Nematostella burrows into salt marsh sediments and remains there for life. But it has developed specialised ‘stinging cells’ that hurl toxins to passing prey, immobilising the morsel so that the anemone can capture it with its tentacles. This species is currently under protection in the United Kingdom due to its concerning depletion in numbers.

“The numbers of Nematostella in the wild have been dramatically decreasing over time,” said Karen Echeverri, senior author and associate scientist in the MBL’s Bell Center for Regenerative Biology and Tissue Engineering.

The study

The MBL research team focused on phthalates (or plasticisers), chemicals that are widely used in plastic packaging or other consumer products that wash into the ocean, and potassium nitrate, which enters marshes through runoff from lawn fertilisers.

Sea anemone Nematostella embryos were exposed to phthalate and nitrate concentrations commonly found in coastal environments (1-20 µM). Observation showed that there was a gross decrease in body size two weeks after exposure. The sea anemone Nematostella’s also had fewer tentacles, and the tentacles that did grow were misshapen or uneven in length or number. Furthermore, the pollutant-exposed animals had a severely reduced number of stinging cells (or cnidocytes), which they use as a defence mechanism and to capture food.

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

Sea anemone Nematostella is sessile (stationary), and it must constantly acclimate to environmental changes, such as temperature and salinity. “They have what we call adaptive plasticity; they are resilient to change,” said Echeverri. “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.”

What is considered unusual about this study, is that it integrates assessment of the pollutants’ impact on sea anemone Nematostella’s microbiome; MBL scientists Emil Ruff and team sequenced the microbiomes of animals after ten days of pollutant exposure.

“Certain classes of microbes became much more dominant after exposure,” said Echeverri. “How this affects the physiology of the animal, we don’t completely know yet.”

Shifts in the microbiome can serve as sentinels of change in the health of the host, which has been revealed in prior studies on other animals, including corals and humans. Other studies into the impacts of phthalates on embryonic development in vertebrates, including frogs and zebrafish, identified defects in body growth similar to what was found in the sea anemone Nematostella. These 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.

“A next step is to link changes in the Nematostella microbiome to changes in the animal’s development,” Echeverri concluded.

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