you're reading...

Sharkbites Saturday

It’s Getting Hot In Here: How Ocean Acidification and Warming Affect Shark Hunting and Behavior

Article: Pistevos, J. C. A., Nagelkerken, I., Rossi, T. and Connell, S. D. (2017), Antagonistic effects of ocean acidification and warming on hunting sharks. Oikos, 126: n/a. doi:10.1111/oik.03182

Featured Image: Port Jackson Shark. Credit: Dave Harasti/Australasia Scuba Diver 2008: Issue 4


Sharks have an advanced sensory system that allows for efficient foraging using various senses such as sight, hearing, smelling, and touch.  They can even detect movement, and differences in pressure! Because of this, some sharks are high in the food web. So, any changes in their physiology and behavior due to the changing climate is likely to trickle down into lower trophic levels and alter the structure of the marine food web. What causes such changes, though?  When we burn fossil fuels such as coal, oil and gas for energy or transportation, excess carbon dioxide (CO2) gets released into the atmosphere. This excess CO2 acts like a heat trapping blanket and the ocean absorbs much of this heat. The ocean also absorbs about quarter of this excess CO2 where it reacts with seawater and making the ocean more acidic. This is called ocean acidification.

Studies have looked at how ocean warming and ocean acidification affects sharks separately. For example, a rise in ocean temperature increases the hunting activity of sharks. However, studies observing the combined result of these ocean changes are far and few. Thus, Pistevos et al. set out to investigate what the combined effect was on shark behavior and physiological responses. To do so, they studied the Port Jackson shark (Heterodontus portusjacksoni) which is an egg-laying shark found only in the mild or temperate waters of Southern Australia. It forages primarily on bottom-dwelling animals like mollusks, sea urchins, crustaceans, and fish.

Methods & Results

Figure 1. A port jackson shark egg capsule containing a single embryo. Credit: Kate Bunker/Flickr

Recently hatched sharks are more sensitive to environmental changes, which is why the authors wanted to focus on studying their responses. As many as 95 eggs were collected from the Gulf of St. Vincent in Adelaide, Australia. The eggs were brought to the lab to study the effects of ocean warming and acidification on the baby sharks’ foraging ability.

The sharks were put to the test within 24 hours of when they hatched by placing them in an arena with two metal containers on either side of the tank, one containing an odor cue (urchin) and the other the same size as the urchin but without an odor cue. The urchins were collected from the same site as the shark eggs, possibly to test odor cues they might encounter in their habitat. The sharks were observed for the time spent and the distance traveled between the control zone to the urchin. After the odor tracking test, the motivational drive to forage or accept prey was studied by placing prawn meat and/or mussel meat on opposite sides of the tank, thus, containing both visual and odor cues. Sharks either ate any of the food introduced within 2 min or were hand fed the food with steel forceps for 2 min. While undergoing these hunting tests, the juvenile sharks were exposed to different temperatures and CO2 levels separately and in combination.


Temperature and increased CO2 levels did not affect foraging behavior in sharks based on odor cues. Surprised? Increase in temperature alone: (1) increased the amount of time sharks spent near chemical cues of prey by 55% (2) increased swimming activity during hunting, and (3) reduced the time sharks spent accepting prey. The positive effect of temperature was canceled out in combination with higher CO2 resulting in minimal response towards prey odor cues and more time spent accepting prey. Interestingly enough, there was no effect on swimming speed due to acidification.

Sharks face a dodgy future because of the rapidly changing ocean. Elevated temperatures raise the energetic demands of sharks and acidification can hinder the ability of sharks to meet those demands by preventing successful prey encounters and adversely affecting growth. With some sharks being at the top of the food web, reduced hunting by sharks could result in a major shift in the food web and distorted predator-prey interactions, and ultimately, extinction. Therefore, it is important to look at different interactions of stressors on sharks. Further studies focusing on the possibility of sharks not meeting their exceeding energy requirement could shed more light on their future as some of the top predators of the marine ecosystem as well.


No comments yet.

Post a Comment


  • by oceanbites 3 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 4 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 5 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 6 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 7 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 7 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 7 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 8 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 8 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 8 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 8 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 9 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 9 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 10 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 10 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 11 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 11 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 12 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 12 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 1 year 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