Biology

Ocean acidification has unexpected consequences for some species

The acidification of the ocean is one of the serious consequences of the climate change in the ocean. Not only can it affect the absorption of CO2, due to the acid-base imbalance, but also due to other consequences that are gradually being discovered.

In a study published in PLOS ONE , Mirko Mutalipassi and colleagues at Stazione Zoologica Anton Dohrn in Italy have found that shrimp fed seaweed grown in acidic water do not experience the sex change that is characteristic of their reproductive life.

Shrimp as a model species affected by ocean acidification

The Hippolyte inermis marine shrimp lives in the seagrass beds of Posidonia oceanica and has two breeding seasons per year , with some males born in spring developing rapidly and becoming females that produce eggs the following fall.

This sex change depends on a bioactive compound produced by the microalgae present in their spring diet ( Cocconeis scutellum parva ) that causes male endocrine cells to die. Cocconeis scutellum parva is an epiphytic diatom that lives on the leaves of Posidonia oceanica plants .

To investigate the impact of ocean acidification on this rare reproductive cycle, the researchers fed shrimp algae grown in waters at a pH of 8.2 representing current conditions, or a pH of 7.7 representing predicted levels of ocean acidity. by 2100.

They found that algae growth correlated with the amount of carbon dioxide dissolved in the water , with four times more algae cells in acidic waters compared to current ocean conditions.

However, the H. inermis shrimp populations fed algae cultured at normal pH were 63% female, while those that received an algae diet from an acidic environment contained 36% female, similar to the sex ratio of the control populations. shrimp fed algae that did not produce these compounds.

This indicates that, under acidic conditions, the algal compound was not produced or was not effective in triggering a sex change , suggesting that the fall breeding season may be affected by predicted declines in ocean pH over the next century.

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