//
you're reading...

Biology

Fatal attraction: Under climate change, fish swimming towards predators, not away from them

Paper: Welch, M. J., Watson, S.-A., Welsh, J. Q., McCormick, M. I., & Munday, P. L. (2014). Effects of elevated CO2 on fish behaviour undiminished by transgenerational acclimation. Nature Climate Change, 2(October), 2–5. doi:10.1038/nclimate2400

Background

Many studies have already been done showing that more carbon dioxide (CO2) in the water (a condition called hypercapnia) can affect the behavior of fish. It causes them to lose their sense of direction, behave strangely, process smells differently, and even increases their stress levels. All of those aspects may seem inconsequential, but when you’re a fish, whether you live or die depends on your ability to get away from predators.

One of the ways that fish communicate in the water to each other is through chemical cues, similar to smells. The chemical molecules dissolve in the water immediately around the fish and spread outward from that point, much like an open bottle of perfume will soon be smelled throughout a room. Some of these chemical signals attract mates, called pheromones, and others communicate danger, called alarm cues. Fish innately know to swim towards the pheromones and swim away from the alarm cues, much like you innately know to go towards the smell of cooking and away from the smell of rotting food.

Studies have already shown that fish raised under high CO2 conditions don’t process chemical signals correctly. Instead of swimming away from these chemical alarm cues, they won’t notice them at all, or worse, they’ll swim towards them. This study is different in that it wanted to see if these fish could adapt to high CO2 conditions. They raised parents in control and higher CO2 environments, then saw how their offspring were responding to these chemical alarm cues.

Methods

This study was conducted using a common fish found on coral reefs, the spiny chromis (Acanthochromis polyacanthus), as the model species.

 

Spiny Chromis

Spiny Chromis

The researchers tested their hypothesis, that these fish would be (hopefully!) be able to adapt to higher CO2 conditions, using a purely factorial design illustrated in the diagram below. The reason they chose to do this was to test out all possible combinations of parent and offspring conditions to get the most correct picture of what was happening to these fish.

Experimental design, testing all the alternatives.

Experimental design, testing all the alternatives.

They raised parents in control conditions (representing CO2 levels right now), mid-CO2 conditions (what’s expected in 50 years) and high CO2 conditions (what’s expected by 2100). They then took the eggs and raised them in one of the three CO2 levels, then tested their sense of smell.

To do that, the researchers used a flume tank, illustrated below. The researchers pumped one side with regular, untreated seawater, and the other side with seawater treated with the chemical alarm cue. The fish is free to swim back and forth between the sides, and the researchers can calculate how much time the fish spends in either side of the tank to determine its preference. Each trial involved 2 minutes of the fish in this tank, then a rest period, then 2 more minutes of the fish in the tank with the treatments switched to eliminate any preference the fish had for the side of the tank.

Visual explanation of how the flume tank works.

Visual explanation of how the flume tank works.

Results

The offspring showed the same trends regardless of the CO2 level in which the parents were raised. The offspring that were raised in a high CO2 environment sent an average of 75% of their time in the tank swimming in the side with the alarm cue. That suggests that they’re not recognizing the cue as something they should be afraid of, and instead something they should be attracted to. The offspring raised in the mid-CO2 environment were moderately attracted to the alarm cue and spent about 55% of their time on that side of the flume tank.

The offspring raised in the control environment showed a more variable result. If the parents were also reared in that control environment, the offspring showed the “correct” response to the chemical alarm cue and stayed away from it (only 10% of their time was spent on that side of the tank). However, if the parents were raised in a higher CO2 environment (either mid or high CO2), the offspring spent more time in the alarm cue (30% of the time). That suggests that even if the oceans go back to normal CO2 levels, those offspring are already likely to spend more time not responding correctly to the alarm cues just because their parents came from a high CO2 environment.

Results of the chemical alarm cue experiment.

Results of the chemical alarm cue experiment.

Significance

These results illustrate that there is very little to suggest that these reef fish will be able to adapt to a high CO2 ocean. Even when the parents also came from a high CO2 environment, the offspring were at a significant disadvantage for dealing with that high CO2 and went towards the cue that normally indicates the presence of a predator. They showed a small decrease in time spent in the alarm cue (75% with control parents to 70% with high CO2 parents) but overall, the capacity for acclimatization doesn’t look promising. As the ocean gets more and more CO2, these fish will continue to move towards alarm cues instead of away from them and will get eaten more often.

One of the best hopes we have for dealing with climate change in general is that animals will adapt to the new conditions, just like they have to different conditions in the past. However, we are changing the conditions too rapidly for these animals to gradually adapt, and instead we’ll see more results like this that could result in changing food web dynamics and the loss of biodiversity.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 weeks 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 1 month 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 3 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 3 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 3 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 3 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 4 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 4 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 5 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 5 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 5 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 5 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 6 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 6 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 7 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 7 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 8 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 9 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 9 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 
  • by oceanbites 9 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
WP2Social Auto Publish Powered By : XYZScripts.com