Female lobsters are getting smaller, but what about the next generation?

BAR HARBOR — As Maine’s waters are growing warmer and more acidic, lobster researchers are looking at how that’s affecting both the mothers and offspring of the state’s most prized crustacean.   

One thing is known for sure: Mature female lobsters have been shrinking.  

Over the past three years, Jesica Waller, a lobster scientist at the state’s Department of Marine Resources, has collected and analyzed more than 1,200 female lobsters along the coast. She has found that since the 1990s, mature females are getting smaller.  

“DMR research shows that the carapace/shell length at which most females reach maturity has decreased coastwide over the last 25-30 years,” she wrote in an email. “We sampled and analyzed females along Maine’s coast, and we found that the length at which most females reach maturity has decreased between 5.6 mm and 6.7 mm over this period (mid-1990s to today).”  

While we know mother lobsters are getting smaller, Bigelow has also done work to see how the species offspring in the larval stages handle rising temperatures and ocean acidification.  

The larvae seemed to be able to handle ocean acidification. Previous research showed it had little effect on their growth and metabolism, but a study published earlier this year by Maura Niemisto, a research associate at Bigelow, found that it is changing them at a molecular level.  

Through genes, all living organisms can regulate a range of biological processes that can be influenced by changes in the environment.  

Niemisto’s study focused on the post-larval stage of lobsters that live in the upper water column where ocean acidification and temperature are changing quickly. At this stage, the lobsters are planktonic, meaning they have limited control on their movement and can’t simply move on to more favorable environments.  

The scientists exposed the post-larval lobsters to the temperature and acidity levels projected for the end of the century and found that the lobsters’ cells adjusted gene regulation to support shell structure and immune functions.  

The response was stronger in relation to increased acidity than increased temperature, but when the environment was both warm and acidic, the lobsters showed significantly more genetic response than when exposed to either one alone. 

“Stressors on an organism have the ability to compound into something that makes it really hard to grow through all the developmental stages to get to a full-grown lobster,” Niemisto said in a statement earlier this year.  

Lobsters may be able to adapt to a changing environment, but it takes a significant amount of energy that comes from a limited budget.

Ethan Genter, The Ellsworth American, 9 June 2021. Article.

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