The Culprit Behind Sea Star Wasting Disease

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Healthy sunflower sea star (left), sunflower sea star with SSWD (right). Photos taken by Neil McDaniel.

By Amanda Ojeda

The old man strolled down the desolate beach, enjoying his daily early morning walk. During this time of the day, the beach hosts usually one old man, but today was different. The old man squinted his eyes, furrowed his brow, and saw a small figure shuffling along the shore. The tiny person was quite repetitive in his motions- shuffle, kneel, throw, move, repeat. A now curious old man slowly approached the boy.

As he neared, he called out the words, “What are you doing there, young boy?”

The young boy then replied, “I’m saving these stranded starfish. They wash up on the shore, and if they stay on the beach they will dry out and die; I’m putting them back into their home so they can live.”

However, the old man couldn’t quite understand the purpose of the young boy’s actions. “Let me tell you something young boy, this stretch of the beach must have more than one hundred stranded starfish. The beach and its entirety must have millions of stranded starfish. Trust me, I have walked this beach every day for 10 years, I have seen them every day for 10 years. I’m sorry young man, I’m afraid you will never make a difference.”

With a confident smile the boy simply said, “well I just made a difference for that one”.

This famous tale of the boy and the starfish is often told to young children, to teach them the importance of the little things. The animal activist in the making, detailed in the story, saved a few starfish from the harsh sun rays that would have otherwise killed them. Unfortunately, the sun is not the only issue these starfish face. Something else is lurking in the water, a microscopic killer: bacteria.

Sea Star Wasting disease appeared at a great magnitude in 2013/2014, when the starfish population drastically decreased. However, the syndrome has been present for decades. Veterinarian Joe Gaydos, referred to the SSWD situation as an “underwater zombie apocalypse”, which is a quite accurate name when one discovers the symptoms. Many starfish that were analyzed, who had died from the disease, showed the same symptoms. This includes lesions appearing on the ectoderm of the starfish, curling arms, a deflated appearance, and the loss of limbs and internal organs. To simplify, the disease physically decays the body leading to death.

The pycnopodia helianthoides, or the sunflower sea star has been categorized as critically endangered and is one of the more than 20 species affected by this disease. The regions affected are mostly in the West Coast from Mexico to Alaska. Some parts have also seen as much as a 90% decline in the local starfish population. SSWD has even reached certain captive sea stars, such as those in the Vancouver Aquarium.

Marine ecologist, Mark Carr, describes this marine epidemic as, “not just a population reduction, this is virtually the loss of a key species over thousands of miles. We’ve never seen anything like this before.”

The effect of the disease is not limited to solely sea stars. In northern California, studies show a loss of more than 90% of their kelp forests. SSWD killed most of a once common starfish species in the area, the sunflower sea star. The predator sea star feeds on sea urchins and the sea urchins’ source of food is kelp. Without the sunflower sea star to control the sea urchin population, the sea urchins have eaten through the kelp, leaving the kelp forests barren and unable to provide food for other species.

While plenty of research has been done on the effects of SSWD, little is known about the cause. Prior to recent discoveries, scientists believed that it was an infection that was transmitted one by one and spread to the thousands of miles it affects currently. 

The true cause is a group of bacteria known as copiotrophs. Copiotrophs live in nutrient filled environments and were present in much higher levels in the days prior to lesions developing on the starfish. Along with copiotrophs oxygen depleting bacteria aided in starfish contracting SSWD. This lack of oxygen and nutrients deprives the starfish and initiates their gradual death. This research disproves the previous belief that the disease is caused by a contagious pathogen.

Most bacteria, including copiotrophs, thrive in warmer temperatures. Warmer water also proves to have less oxygen than colder water. Therefore, scientists are now questioning how climate change may worsen the SSWD spread. They are also conducting studies to understand why some places have a greater decrease than other locations. With the new research available, and a known cause, treatment methods are being formulated. One of the methods in discussion is to treat starfish within labs by placing them in water tubs with higher oxygen levels. Although this may not solve the high rates of SSWD in the ocean, many are grateful for this new step in the right direction.

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