you're reading...


Larval Donkey’s ear abalone threatened by climate change




Tahil, A.S., and Dy, D.T. 2016. Effects of reduced pH on the early larval development of hatchery-reared Donkey’s ear abalone, Haliotis asinina (Linnaeus 1758). Aquaculture doi: 10.1016/j.aquaculture.2016.03.027.

Aba-what now?

Unless you’re like me and read Island of the Blue Dolphins by Scott O’Dell at a formative age, you’ve probably never heard of abalones.  These are a group of edible sea snails (Fig 1).  They’re consumed raw or cooked, and are considered a delicacy in many cultures (Fig 2).  In 2004, abalone meat could cost up to $75 for a restaurant-sized portion (around 4 ounces).  They have calcified shells made of nacre, also known as mother-of-pearl, a valuable substance used for decorative purposes (Fig 3).  While they are naturally found all around the world, especially in the cold waters off the coast of New Zealand, South Africa, Australia, and Japan, abalone farming became popular in the mid-90’s in order to keep up with consumer demand. Farming began in the 1950s and 60s in China and Japan, but now is seen in countries all around the world, including Taiwan, Korea, Ireland, the US, Mexico, Canada, and Australia (to name a few).  Clearly, this is an important group economically and culturally across the world, and it’s being threatened by global climate change.

4.16 1

Fig 1: A live abalone in its natural habitat. Source: public commons

How climate change hurts marine critters that need to grow shells

Researchers have long thought that climate change might be particularly devastating to marine organisms that use calcium to build shells or other external structures.  In fact, we’ve had a number of Oceanbites posts on the topic (e.g. http://oceanbites.org/ocean-acid-peekaboo-shrimp/). To recap briefly, as carbon dioxide builds up in the atmosphere, the oceans take up a lot of it.  As CO2 dissolves, it reacts with water to form several chemicals that act to lower the pH of seawater.  Calcified marine organisms, like abalone, use a lot of calcium carbonate, which is less likely to form or remain stable in a low-pH system.  Calcium carbonate helps these organisms build important structures like shells, which help them avoid being eaten by predators and protect them from drying out.  Here’s a great video talking about the impact of ocean acidification on calcified marine organisms.  pH is measured on a scale of 0-14; most organisms can only tolerate a narrow range of pH levels.  Seawater pH is expected to drop by .3-.5 units by the year 2100.

4.16 2

Fig 2: Cooked abalone on the menu! Source: flickr

Studying the effect of lower pH on larval abalone

These authors examined the effect of reduced seawater pH on baby Donkey’s eared abalone (that *is* in fact the species name!) in a hatchery in the Philippines.  They raised larval abalone in boxes with filtered seawater under four treatments (based on that expected reduction of seawater pH by .3-.5 units):

  • pH of surrounding seawater – ambient pH/control group (7.97)
  • Ambient pH reduced by .2 units (7.78)
  • Ambient pH reduced by .4 units (7.60)
  • Ambient pH reduced by .6 units (7.40).

They maintained constant temperature, salinity, and dissolved oxygen levels across these four treatments.  Treatments were maintained for about 6.5 hours, since abalone larvae will hatch after 5-6 hours under normal conditions. They placed fertilized eggs from naturally spawning abalone within the hatchery into those treatments. They measured the following responses:

  • Hatching rate
  • Percentage of normal vs. malformed larval abalone
  • Survival rate
4.16 3

Fig 3: Iridescent mother-of-pearl comes from the shiny inner layer of calcified shells, which is called nacre. This is abalone nacre. Source: flickr


Hatching rate, percentage of normal larvae hatched, and survival rate all decreased significantly with a decrease in pH (e.g. Fig 4).  Survival rate in the control group was close to 100%. Survival rate was almost 0% in the most extreme treatment, which mimics expected seawater pH conditions about one hundred years from now! Very few of the abalone that hatched in the treatment which reduced ambient pH by .4 units appeared normal under a microscope, and survival rate dropped to about 30% – a drastic difference from the control.

4.16 4

Fig 4: Survival rate between the different treatments – ambient pH on the left, and progressively more extreme reductions in pH as you move to the right. Source: Tahil & Dy 2016


An average change of .4 units in one hundred years may not sound like a major drop in pH from our human perspective, but it is clearly enough to have drastic evolutionary and developmental effects on these larval abalone.  In the coming years, we can expect to see fewer and fewer surviving abalone (and other calcifying organisms like them), which will have major economic and environmental impacts.  Filter-feeders, like abalone and other shellfish, play a key role in their ecosystems, filtering out and containing nutrients and toxins that are harmful to other marine life.  In fact, the Hudson River Foundation is growing oysters (another calcified filter feeder) to clean up the Hudson River!   Losing abalone and other species like abalone could prove devastating to marine environments.  These organisms may evolve to survive better in a post-climate-change world, but for now it’s clear we need to mitigate the effects of climate change on ocean pH levels if we want to keep them around.


Questions?  Comments?  Please sound off below!  I’d love to hear from you :)




  1. […] you caught my post in April, I talked a little bit about the process of ocean acidification.  Essentially, as carbon dioxide […]

Post a Comment


  • by oceanbites 2 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 3 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 4 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 5 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 7 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 8 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 9 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 9 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 9 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 10 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 11 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 11 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com