What will a warmer, acidic ocean mean for American lobsters?
Research explores how the American lobster will respond to a changing climate
From the time lobsters hatch, it’s a struggle to survive — they must find enough food, avoid being eaten, grow, and stay alive long enough to hatch eggs of their own. But even before they hatch, lobsters face another challenge: ocean acidification and warming waters.
Researchers at the Virginia Institute of Marine Science are conducting one of the first studies to examine how lobster embryos, one of the most vulnerable stages of a lobster's life, will be affected by ocean acidification.
The project is part of the Sea Grant American Lobster Initiative , an effort to understand how the American Lobster will fare in a changing climate.
Most American lobsters landed in the United States are from Maine and Massachusetts. These lobsters live in the Gulf of Maine and Georges Bank, the area connecting the Gulf to the Atlantic Ocean. The Gulf of Maine is one of the fastest-changing ocean environments in the world, with water temperatures rising about three times faster than the global average.
"That, and acidification, make it a very alarming level of change going on," said Jeff Shields, a VIMS professor and co-lead on the project. "The lobster managers from Massachusetts and Maine are worried, as are some of the fishermen, about what will happen in the next 20 years, and what will happen in the next 50 years. I'm hoping some of the work we're doing now will lay the foundation for a better understanding of that change."
Because lobsters can take seven years or more to reach maturity, the lobsters hatching now won't be caught in lobster pots for several years. Furthermore, females don’t produce eggs every year. That means that the management decisions made today will affect lobster populations for years into the future.
The larvae hatching this year might only produce about 11 more generations before they face the warmer, more acidic waters predicted for the year 2100. Understanding how lobsters will respond to ocean acidification now will help commercial fishers and managers prepare for the future.
Video Part 1 - Research Overview
Acidic water stresses lobsters
The ocean absorbs about a third of the carbon dioxide humans produce. Although this reduces the effects of greenhouse gasses in the atmosphere, the carbon dioxide absorbed by the ocean increases the water’s acidity, a phenomenon known as ocean acidification .
"This makes it more stressful for marine organisms because it disturbs chemical reactions in their cells and costs them more energy to keep themselves healthy," said Emily Rivest, a VIMS assistant professor and co-lead on the project.
Photo: Nick Zachar/NOAA
Even small increases in acidity can harm lobsters and other marine life.
“Where these lobster larvae live has a very intense level of change from the acidic conditions caused by humans, but it's also a hotspot of acidification because of freshwater input from currents," said Brittany Jellison, a postdoctoral researcher who led the laboratory experiments.
Photo by Abigail Sisti | Virginia Institute of Marine Science
Adult lobsters are less vulnerable to ocean acidification than shellfish like oysters. That’s because oysters build their shells out of calcium carbonate, and acidic water dissolves the calcium carbonate and weakens the oysters’ shells. Lobster shells contain some calcium carbonate, but it is mixed in with other components like chitin.
Even though lobster shells aren’t as vulnerable to ocean acidification, acidic water can add an extra layer of stress on top of quickly warming waters. This is especially true in the early parts of a lobster’s life, when water quality has a bigger effect on their overall health.
Unlike adult lobsters, which have extra energy stored up that they can use to deal with stress, embryos need all the energy available from their egg yolk to grow and develop. While a mother lobster might be able to survive in warmer, more acidic water, the eggs she carries tucked in her tail aren't as hardy — and they can't swim away to better water.
“Embryos just have a more limited repertoire of ways they can respond to environmental stress,” Rivest said.
To measure the effects of ocean acidification and warmer waters on the lobster embryos, the researchers kept 24 mother lobsters and their eggs in tanks with carefully controlled pH and temperature. They sorted the lobsters into four groups: a control group experiencing normal water conditions in the Gulf of Maine, a group in acidic water, a group in warmer water, and a group in warm, acidic water.
They monitored egg growth and health over the course of six months to show how long-term exposure affects the embryos’ development. Each week, the researchers estimated the number of eggs carried by the lobster and collected a few embryos as samples. This allowed them to check for any changes caused by stress as the embryos grew.
“Say cheese”
The researchers photographed the embryos each month to measure how the eggs developed until they hatched. From these pictures, the research team can track different features of the embryos, like how quickly they're using up their egg yolks, the size of their eyes, and the size of the eggs overall.
Each of these features gives different clues about how the lobster embryos are growing, and how stressed they might be.
By comparing images from lobster eggs in different water conditions, the researchers can see whether water conditions have a measurable effect on egg health and lobster development.
Photo by Abigail Sisti | Virginia Institute of Marine Science
Growing new cells and organs takes up a lot of an embryo's effort, but basic cell function — just staying alive — also requires energy, according to Abigail Sisti, a Ph.D. student working on the project. The more stressed out the lobster is, the more energy they need just to stay alive and maintain their metabolism. That means a stressed lobster has less energy available to use for growth.
Stress in the cell
Lobsters, when stressed, need more oxygen — just like people breathe heavier when they exercise in order to get the extra oxygen their bodies need. To measure how much oxygen the lobsters use, the researchers put individual eggs in a tiny vial of water and tracked how much oxygen the embryos used up in a set amount of time — a way to estimate their respiration and metabolism.
"It's like how on a hot day, you're hot and sweaty and use more oxygen," Sisti said. "Warmer temperatures will increase respiration, to an extent. That's a well-documented relationship, but we don't know as much about how pH will affect lobsters. In some studies, increased acidity caused increased oxygen consumption, or sometimes their metabolism is lower, when the lobster shuts everything down because it's so stressful."
The researchers will also check the embryos to see if their cells show signs of a stress response. They'll also measure the overall amount of fat and protein in the embryos to see if climate change affects their energy levels.
By separating lobsters into different groups, the researchers will be able to determine how much stress for lobsters is caused by warming waters, and how much is caused by ocean acidification —and whether they cause extra stress when combined.
Two teachers, two weeks, countless students
As the research team counted lobster heartbeats, photographed the eggs, and monitored the water tanks, two high school teachers worked alongside them to learn about the experiment.
Sara Chaves Beam, Chesapeake Bay Governor’s School (left) and Meg Begley, Maine Ocean School (right)
The teachers, Sara Chaves Beam and Meg Begley, spent a week immersed in the research, and a second week planning how they could bring the research experience back to their classrooms. The lesson plans they created will extend that experience to other teachers and students.
With these activities, high school students can investigate the same cutting-edge questions and graph the same data as the NOAA-funded researcher team. Beam said this kind of lesson plan is more engaging for students than hypothetical data or science that’s already settled.
“If they know that they’re learning about something in real time, that the answer is not fully fleshed out or anything, they’re going to get really excited about that,” Beam said.
Video Part 2 - Lesson Plans
The teachers designed a variety of lesson plans to appeal to different types of learners. Presenting different ways for students to connect to the project gives them more opportunities to have meaningful educational experiences about the broader issue of ocean acidification. Begley’s students will have the chance to learn how ocean acidification affects the iconic lobsters of their home state of Maine. Beam’s students will be able to learn about the research happening nearby.
“I think this entire project will be really interesting for my students,” Begley said. “I love the experimental design, how they have this big question and separated it into these little compartments. The technology they have here is really amazing too.”
