//
you're reading...

Pollution

The Otter Guys: How heavy metal pollution affects Alaskan northern sea otters

Reference: Brown, Kristin L., et al. “Metals in the stomach contents and brain, gonad, kidney, and liver tissues of subsistence-harvested northern sea otters (Enhydra lutris kenyoni) from Icy Strait, Alaska.” Marine Pollution Bulletin 166 (2021): 112183. https://doi.org/10.1016/j.marpolbul.2021.112183

Heavy Metal Pollution

Pollution has become an increasingly large problem in our oceans. While a lot of work has gone into solving the visible issues of plastic pollution, the effects of heavy metals on ocean ecosystems, especially as they affect marine mammals, are not fully understood.

Heavy metals, such as mercury, lead, and copper, can sometimes get into marine waters naturally through glacial or mineral deposits, but they can also be introduced into oceans via mining activity. Once in the ecosystem, these metals are essentially a permanent fixture, as they take a long time to naturally degrade. In addition, plants and animals cannot quickly eliminate these metals from the environment, as they do not require large amounts of heavy metals for normal body function. As animals absorb excess heavy metals from the water, the metals move up the food chain, and can end up in high concentrations inside top predators. These high concentrations at the top of the food chain can sometimes be much greater than the levels in animals lower on the food chain, a process known as biomagnification.

A northern sea otter resting on ice in Kenai Fjords National Park, Alaska. These otters tend to live in shallow waters, and rely on their dense coats of fur for warmth. They eat mostly small, hard shelled prey items, such as crabs and clams. Photo by Gregory “Slobirdr” Smith via Wikimedia Commons.

All heavy metals in high doses can cause irreparable damage to top predators, and marine mammals especially, from birth defects to blood disorders. Given that heavy metals can have such a negative effect, it begs the question: are there high levels of heavy metals present in marine mammals that are near sources of heavy metal pollution? To answer this question, researchers from the University of Alaska Fairbanks focused on one marine mammal in particular, the northern sea otter.

Finding the Northern Sea Otters

The researchers zoomed in on the northern sea otter population that lives in the waters of Icy Strait, Alaska, as these otters have never been studied with regard to heavy metals. This population lives near mining sites in Alaska, as well as around glaciers, and are likely exposed to heavy metals in the water. The otters in this area are considered threatened and are an important point of conservation in this ecosystem. They are protected by the Marine Mammal Protection Act of 1972 and the Endangered Species Act.

Part of Icy Strait, Alaska with visible glaciers on the mountainside. This area is home to a wide variety of wildlife aside from the northern sea otters, such as bears, deer, and puffins. Photo by pirateecu via Wikimedia Commons.

This meant that to examine the bodies of otters for heavy metals, researchers had to get creative when finding specimens. Normally when scientists study marine mammals, they will make use of dead specimens that wash up on shore. However, this has its disadvantages, as it is unclear what washed up animals may have died from (i.e. disease, birth defects, or starvation), and they may not accurately reflect the patterns of the healthy population. To avoid this issue, researchers in this study used the bodies of otters that were killed by Native Alaskan hunters, who can hunt the otters for food and cultural purposes under current laws. The brains, stomachs, gonads, liver, and kidneys were removed from these hunted otters, and researchers detected the amount of heavy metals present in each organ. In particular, the presence of arsenic, lead, cadmium, copper, mercury, and selenium were examined.

Were there heavy metals in the otters?

Overall, northern sea otters in the Icy Strait had higher concentrations of heavy metals in their organs compared to otters from other parts of Alaska, Washington state, and even Russia. Some heavy metals, namely cadmium, copper, and selenium, biomagnified in the otter’s kidney and liver tissues. This means that the concentrations of these metals were much higher in otters than they were in the otters’ prey items. The concentrations of heavy metals tended to increase in all the body organs examined as the otters got older. The one exception to this was mercury. This metal showed an interesting relationship where very young and very old otters had the highest concentrations, but otters in intermediate ages had very low concentrations. Researchers believe this may be due to female otters transferring some mercury to their pups via the placenta before they are born.

What does this mean for otters?

Fortunately, though the concentration of heavy metals in these Icy Strait otters was higher than anticipated, none of the heavy metals were present in dangerous amounts. The bodies of the otters showed no damage that could have been caused by heavy metals, and all the organs appeared healthy. This is good news, as it means that heavy metal pollution is not currently a conservation issue in this species.

An example of a mining site in Alaska. Note that the water surrounding the mining site is very cloudy. These mining operations can leach heavy metals into the water, causing pollution. Photo by Dennis Garrett via Wikimedia Commons.

However, there are many ongoing mining operations in Alaska which could release more heavy metals into the waters there. As climate change continues to make the oceans warmer, melting glaciers could also leach more of these harmful elements into the ecosystem. This could quickly increase the amount of heavy metals present in these otters’ bodies, which could cause a sharp decline in their populations if metals increase to dangerous levels.

Given the threatened status of this species, it is important to avoid this outcome. For now, this study represents an excellent way to glean information about the effects of heavy metals in northern sea otters without using washed up and potentially unhealthy specimens. The methods used here can easily become a very useful conservation tool for these furry ocean dwellers.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 2 hours 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 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 2 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 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 4 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 7 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 
WP2Social Auto Publish Powered By : XYZScripts.com