Why Are Starfish Dying? Threats and How You Can Help Save Them (2024)

Unlike their name suggests, starfish aren't actually fish, but marine invertebrates. That's why you might also see them being referred to as sea stars. As they belong to the class Asteroidea, scientists often refer to them as asteroids.

These charismatic marine organisms face huge population losses that in turn affect their broader habitat. In this article, we'll tell you more about the main threats to starfish, as well as what's being done to protect them.

Threats to Starfish

The main worldwide threat to starfish is thought to be sea star wasting (SSW) disease, also called sea star wasting syndrome (SSWS).

While this is a problem in its own right, it can also be linked to other threats including rising sea temperatures due to climate change. Independently, these threats have the potential to decrease starfish populations in affected areas. The combination of SSW disease and rising sea temperatures may have even more devastating effects.

How Long Do Starfish Live?

Around the world, there are almost 2,000 different species of starfish. In the wild, the average lifespan across all species of starfish is 35 years. Due to threats like climate change and sea star wasting disease, many starfish won't reach those upper limits of their age range.

Sea Star Wasting Disease

First properly documented in 2013, seastar wasting disease can cause the mass mortality of starfish. It can manifest as a wide range of different signs and symptoms including discoloration, twisting of arms, deflation of starfish, and lesions of the body wall.

The lesions caused by SSW disease are often white and develop on the body or arms of a starfish. As the lesions spread, the starfish's affected arm falls off. Usually, most starfish can recover from this stress response, but in the case of sea star wasting syndrome, the remaining body tissue starts to decompose and the starfish dies soon afterward. This is usually through rapid degradation, where the starfish literally melts away.

This disease progresses extremely quickly and can decimate local populations of starfish within days.

The exact cause of SSW disease is still unclear. While early research suggested thecause was a desnovirus(Parvoviridae),it's thought this may only affect one species of starfish, thePycnopodia helianthoides,or sunflower star. More recent research suggests the cause is more likely to bemicroorganisms located at the animal-water interface.

So far,20 different speciesof starfish have been identified as suffering from SSWS. This disease is most common along the West Coast of America and has been recorded from Mexico to Alaska.

Climate Change

The rising temperatures of our oceans are thought to play a role in SSW disease. While the exact link between higher temperatures and SSW disease isn't clear yet, some scientists think this may be due to the fact thatwarmer waters contain less oxygen yet higher levels of nutrients.

Lower levels of oxygen in seawater make it harder for starfish to diffuse oxygen across their body surface. If the oxygen levels in the surrounding ocean are too low, starfish cannot obtain enough and willeffectively suffocate.

This effect is exacerbated by the fact that warmer waters contain higher levels of bacteria, which are also linked to algal blooms andocean dead zones.

The problem with higher levels of bacteria is that they reduce the oxygen levels in the waters they inhabit. As starfish start to die, this organic matter becomes available to any bacteria in the surrounding area. Bacteria levels then increase, creating even worse environmental effects for the starfish.

Studies have also foundthat fewer starfish are found in areas of the ocean with higher temperatures. In areas where starfish cannot retreat to deeper, cooler waters, there's a higher chance of them becoming infected with SSW disease, leaving whole areas devoid of these marine organisms.

The Impact of Decreasing Starfish Populations

Why Are Starfish Dying? Threats and How You Can Help Save Them (1)

As the population of starfish within a particular habitat decreases, this affects the other species within the same area. For example, certain species of starfish help control the local population of sea urchins. As the starfish die, the sea urchin population explodes out of control. The sea urchins then overgrazekelp forests. Kelp is an important marine habitat and has the potential to sequester carbon and reduce pollution levels.

Somestarfishspecies are also what's known as keystone species within their habitats. Their existence is critical for the health of the overall ecosystem because they either provide essential resources for other species within the habitat or control the population of species that could potentially dominate it.

Pisaster ochraceus,one of thestarfishspecies affected by SSW, is considered a keystone specieswithin specific areas along the northwest coast of the U.S. When thestarfishin these regions are removed, the musselpopulation that they would usually feed on explodes. As a result, other species cannot establish themselves. These kinds of population changes have serious consequencesfor the overall health of an ecosystem.

Evolution Helps Starfish

In some areas, certain starfish species seem to be evolving rapid adaptations to cope with the threats.

Scientists compared DNAtaken from starfish before and after the largest outbreak of SSW disease in 2013. They found evidence of "microevolution," indicating the species ochre/purple star (Pisaster ochraceus) responded to this extreme event by undergoing a rapid genetic shift.

After a mortality rate of 81% between 2012 and 2015,significant genetic differenceswere found in the surviving population. There was also an increase in the density of juvenile starfish.

This may be an isolated occurrence, and while promising for this particular species, the results don't necessarily indicate that all species of starfish will be able to rapidly respond to and recover from environmental threats. Action still needs to be taken to protect starfish species and their habitats.

What Is Being Done to Protect Starfish

As well as researching the causes of starfish death, in particular the causes of SSW disease, marine scientists are finding ways to try and rebalance the population. One of the main species affected by SSW disease, the sunflower star, is now on theIUCN critically endangered list.

Scientists at the University of Washington arebreeding sunflower stars in captivity. The goal is to learn more about the species and work towards reintroducing captive-bred starfish into the wild, if appropriate.

Manyresearch institutions are taking collective actioncalling for increased efforts to protect marine species impacted by mass mortality events like those caused by SSW disease. Long-term monitoring of existing populations is still ongoing, in an attempt to understand more about these marine species and their wider ecological impact.

Afederal petitionhas also been submitted by The Center for Biological Diversity, calling for the sunflower sea star, one of the main species affected by SSW disease, to be listed as a threatened or endangered species, under theU.S. Endangered Species Act. Granting the species endangered status could help inform coastal development projects that risk impacting the population of this already rare species.

How You Can Help Save Starfish

Even if you don't live near the beach, there are actions you can take to protect populations of starfish. We all havepersonal power when it comes to taking action against climate change, which appears to be a significant driver of SSW disease.

Don't be tempted to bring starfish home from the beach as a memento. Preserving starfish for decoration decreases their population in the wild.

If you observe any starfish you think may be affected by SSW disease,send the details and location to MARINe(Multi-Agency Rocky Intertidal Network). You can also use this form to submit details of healthy starfish.

Why Are Starfish Dying? Threats and How You Can Help Save Them (2024)


Why Are Starfish Dying? Threats and How You Can Help Save Them? ›

Climate Change

What are the threats to starfish? ›

The biggest threats to starfish are a reduction of coral reef habitat, pollution, and marked changes in water temperature.

What is currently being done to protect starfish? ›

Now, ocean scientists in Oregon have developed a technique in an effort to save them. Since implementing their technique, researchers at Oregon Coast Aquarium have rehabilitated over 15 of them and hope that scientists across the Pacific Northwest can mimic the method and help this keystone species avoid extinction.

What can starfish do to protect themselves? ›

Some starfish species have chemical based defenses such as slime (see below), others have bad tasting or toxic chemicals in their body wall, while others have physical deterrents such as spines or armor. For a general account on sea star defenses, visit this page .

Why are starfish dying? ›

The main worldwide threat to starfish is thought to be sea star wasting (SSW) disease, also called sea star wasting syndrome (SSWS). While this is a problem in its own right, it can also be linked to other threats including rising sea temperatures due to climate change.

Are starfish dying out? ›

Massive Starfish Die-Off Is Tied To Global Warming

Sea stars along the Pacific Coast are dying in the largest disease epidemic ever documented in a wild marine species. New research suggests warmer water is making the disease even more deadly.

What is killing starfish? ›

Sea star wasting disease or starfish wasting syndrome is a disease of starfish and several other echinoderms that appears sporadically, causing mass mortality of those affected. There are approximately 40 species of sea stars that have been affected by this disease.

Is it OK to touch starfish? ›

Everyone needs to understand the importance of not touching and not removing starfish from the sea. The reason starfish die outside water is that they cannot breathe. This leads to carbon dioxide poisoning and ultimately asphyxiation. Another common cause of death is stress from handling them too much.

Can starfish bite? ›

Most starfish are not poisonous, and since they can't bite or sting us, they pose no threat to humans. However, there's a species called the crown-of-thorns starfish which is venomous, and if their spines pierce the skin they can be venomous.

Can I keep a starfish alive? ›

Well yes, but you need a constantly moving source of sea water. You have to feed them live shellfish, like clams, oysters or mussels. They are difficult to take care of, but some public aquariums have starfish displays. You need a LOT of circulating water and you need access to clean natural seawater.

Do starfish still exist? ›

There are approximately 2,000 species of sea star, all of which live in marine waters. Sea stars live underwater, but that is where their resemblance to fish ends.

What do starfish eat kids? ›

Sea Stars Are Carnivores

They usually feed on coral, sponges, clams, oysters, sand dollars, and mussels because these animals also attach themselves to rocks and move slowly, so they're nearby. Some starfish will also eat other animals, such as fish, if they are injured and unable to move away in time.

How do starfish survive for kids? ›

They have no brain or blood!

However, they find very clever and simple ways to get around it. Seawater is pumped throughout their body as a replacement for blood, with the water delivering key nutrients to the starfish allowing its organs to function properly.

How do starfish protect their babies? ›

When most sea stars reproduce, they release their swimming larvae to the sea. But the blood star (Herica) holds on to her eggs, forming a pouch with her arms to protect her young. She holds them there, hunched over, until they are fully formed and ready to be released.

What are the predators of starfish? ›

Many different animals eat sea stars, including fish, sea turtles, snails, crabs, shrimp, otters, birds and even other sea stars. Though the sea star's skin is hard and bumpy, a predator can eat it whole if its mouth is large enough. Predators with smaller mouths can flip the sea star over and eat the softer underside.

What disease is killing starfish? ›

Sea star wasting syndrome is a general description of a set of symptoms that are found in sea stars. Typically, lesions appear in the ectoderm followed by decay of tissue surrounding the lesions, which can lead to eventual fragmentation of the body and death.

How do humans negatively affect starfish? ›

Humans impacted the starfish in many ways. Human beings used starfish as source of entertainment and sell. Human beings have polluted the water sources and destroyed their habitats and finally kill the starfish.

What animal hunts starfish? ›

Predators (animals that eat them) include crabs, lobsters, bottom dwelling fish, other sea stars, and seagulls. Sometimes a predator will grab onto a sea star's arm and the sea star can detach or let go of it to get away.

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