Sea Star Wasting Disease and the Impact on its...
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Sea Star Wasting Disease On the west coast of North America scientists have observed a great number of sea stars dying from a mysterious disease known as the sea star wasting disease. Although this mysterious disease had been observed in the years 1970, 1980, and 1990 scientists have never seen it affect so many sea stars on such a large scale. The wasting disease was first seen on ochre stars in June of 2013 off the coast of Washington State and since then it seems to have spread as far as California. Over the course of a couple of days, sea stars experience what looks like necrosis, or rotting of the flesh. When they are exposed to this disease white lesions appear on their bodies and within couple of hours they become limp. Scientists have reported that the echinoderms' arms will fall off and necrosis kills the organisms. This disease does not only affect one species of sea stars. Species affected include the mottled star (Evasterias troschelii), leather star (Dermasterias imbricata), and six- armed stars (Leptasterias). In August of 2013 divers who were investigating subtidal habitats reported massive die-offs of sunflower stars (Pycnopodia helianthoides). And in November of 2013 similar die-offs were spotted off the coast of Monterey, California. In a matter of six months this disease spread from the coast of Washington to the coast of California. Today this mysterious disease can be seen as far as Mexico: "45 of the 84 marine sites from Alaska to San Diego sampled since that summer, and in the summer of 2014 it has spread to Mexico and parts of Oregon" (Santa Cruz Ecology Department). There are four levels of necrosis categorized by severity. Category 0 and 1 contain the least severe of the 4 categories. In category 0 sea stars appear to be completely healthy with no exposure to the disease and in category 1 sea stars have white lesions focused mainly single area. Categories 2 through 4 are more severe and show necrosis involving the whole body. In these stages sea stars can be seen with white lesions surrounding their bodies and are accompanied by missing limbs. Category 4 is the most severe stage, many sea stars are missing multiple limbs and necrosis causes death. Impact on the Ecosystem Drew Harvell, a professor of ecology at Cornell University, says "it is happening at such a large scale to the most important predators of the tidal and sub-tidal zones. Their disappearance is an experiment in ecological upheaval the likes of which we've never seen." Removal of sea stars would cause an imbalance in the ecosystem because "starfish [are] the 'keystone' species governing biological diversity in the entire intertidal zone" (Keystone Species Hypothesis). A keystone species can be defined as a species that is important to a specific community. The removal of a keystone species usually triggers a change in the community it inhabits. Robert T. Paine was an ecologist who coined the keystone species theory. He studied the removal of the purple sea star (Pisaster ochraceu) on Tatoosh Island in Washington and discovered that when the sea stars disappeared the population of mussels increased. Without the presence of sea stars the competition in the intertidal community will increase. Food and space will be limited and will most likely lead to a population decline in other invertebrates that inhabit these communities. Mussels, whose key predators are the sea star, will overtake communities leaving no room for other organisms. Sometimes the disappearance of a keystone species can lead to extinction of entire species of organisms. Sea Star Wasting Disease and the Impact on its Ecosystem By: Sue Ellen Yu Biology 115, Miramar College Abstract Sea stars believe it or not, are important species in many intertidal zone areas. They play an important role in the balance of the marine ecosystem. However, with the introduction of a mysterious disease off the west coast of North America, the sea star population has been at a decline. What is this mysterious disease that is impacting the sea star populations and what types of sea stars are affected? Although there are many questions regarding sea star wasting disease, many questions are left unanswered because research is still ongoing. This poster will introduce what sea star wasting disease is, what causes it, and how important sea stars are to their communities. Introduction Echinoderms, commonly known as sea stars, are benthic invertebrates found in many different areas like: lagoons, tide pools, surf grass, and kelp forests. Although many people refer to these organisms as starfish, they are not fish. Unlike fish, these organisms lack a backbone and are invertebrates. Sea stars are related to sea urchins, sea cucumbers, and brittle stars. They can range in size depending on species and although considerably small compared to other animals they play an important role in the ecology of their environment. However, just recently, there has been a mysterious disease plaguing the sea star community along the west coast. Cause of the Disease Since the first spotting of this disease scientists have been baffled by what causes it. At first researchers thought that the changing environment played a factor. A combination of warmer waters, ocean acidification, and microorganisms could be the reason behind the population decline. However, scientists at Cornell University believe they have narrowed it down to densovirus. This densovirus, SSaDV, was seen in museum specimens as early as 1942. Although it was found in museum specimens, the virus was only present at low levels so it served no serious threats to organisms. Scientists believe that the virus could have mutated and changed along with its environment causing the virus to grow stronger. Even though they believed to have narrowed it down to this virus, researchers still have many questions: "Why now? What is it that changed that created the conditions for this outbreak? And we don't have the answer to that. But certainly a viral mutation would be one explanation" (Drew Harvell, Cornell University). Ongoing research is still happening today and everyday researchers are discovering something new about this mysterious epidemic. Figure 1: Ochre sea star. Figure 2: Six-armed star. Sources Dunham, Will. "Virus Implicated in Massive Die-off of North American Starfish." Reuters. N.p., 17 Nov. 2014. Web. 15 May 2015. <http://www.reuters.com/article/2014/11/17/ us-science-starfish-idUSKCN0J129K20141117>. "Keystone Species." Kennesaw State University. N.p., n.d. Web. 15 May 2015.<http://science.kennesaw.edu/~jdirnber/ecology/Lecture/LecComEcol/LecCommImportance/PaineComm.JPG>. "Ochre Star." Friends of La Jolla Shores. N.p., n.d. Web. 15 May 2015. <http://friendsoflajollashores.com/marinelife/wp- content/gallery/ochre-sea-star/ochre-sea-star_7669304298_o.jpg>. "Pacific Rocky Intertidal Monitoring: Trends and Synthesis." University of Santa Cruz Ecology and Evolutionary Biology. N.p., n.d.Web.15 May 2015. <http://www.eeb.ucsc.edu/pacificrockyintertidal/data-products/sea-star-wasting/>. "Sea Star Wasting Syndrome Map." Map. Pacific Rocky Intertidal Monitoring: Trends and Synthesis N.p., n.d. Web. 15 May 2015. <http://data.piscoweb.org/marine1/seastardisease.html>. "Six Armed Star." Walla Walla University. N.p., n.d. Web. 15 May 2015. <http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Echinodermata/Class%20Asteroidea/ Leptasterias_aequalis3sDLC2005.jpg>. "Sunflower Star." Friday Harbor Marine Health Observatory. N.p., n.d. Web. 15 May 2015. <https://fhmho.files.wordpress.com/2011/04/sunflower-star2.jpg?w=300&h=225>. Virus Fingered as Top Suspect in West Coast Sea Star Wasting Disease. Washington DC: US Fed News Service, 2014. ProQuest. Web. 15 May 2015. <Including US State News Retrieved from http://search.proquest.com/docview/1626377739?accountid=38871>. Figure 4: Map of sea star wasting disease sightings along the west coast of North America. Figure 5: Category 1 sea star with lesions on the arm. Figure 6: Category 3 sea star, necrosis has begun. White lesions can be seen throughout the body. Figure 7: Category 4 sea star shown. Full decay of the body and limbs causes death in organism. Figure 3: Sunflower star. Figure 8: The sea star is the top consumer in this community. This figure shows that if the sea star is removed then its prey, the primary consumers, will take over the community. This can cause overpopulation and more competition for the already crowded intertidal community.
Transcript of Sea Star Wasting Disease and the Impact on its...
Sea Star Wasting DiseaseOn the west coast of North America scientists have observed
a great number of sea stars dying from a mysterious disease
known as the sea star wasting disease. Although this
mysterious disease had been observed in the years 1970,
1980, and 1990 scientists have never seen it affect so many
sea stars on such a large scale. The wasting disease was first
seen on ochre stars in June of 2013 off the coast of
Washington State and since then it seems to have spread as
far as California. Over the course of a couple of days, sea
stars experience what looks like necrosis, or rotting of the
flesh. When they are exposed to this disease white lesions
appear on their bodies and within couple of hours they
become limp. Scientists have reported that the echinoderms'
arms will fall off and necrosis kills the organisms.
This disease does not only affect one species of sea stars.
Species affected include the mottled star (Evasterias
troschelii), leather star (Dermasterias imbricata), and six-
armed stars (Leptasterias). In August of 2013 divers who were
investigating subtidal habitats reported massive die-offs of
sunflower stars (Pycnopodia helianthoides). And in November
of 2013 similar die-offs were spotted off the coast of Monterey,
California. In a matter of six months this disease spread from
the coast of Washington to the coast of California. Today this
mysterious disease can be seen as far as Mexico: "45 of the
84 marine sites from Alaska to San Diego sampled since that
summer, and in the summer of 2014 it has spread to Mexico
and parts of Oregon" (Santa Cruz Ecology Department).
There are four levels of necrosis categorized by severity.
Category 0 and 1 contain the least severe of the 4 categories.
In category 0 sea stars appear to be completely healthy with
no exposure to the disease and in category 1 sea stars have
white lesions focused mainly single area. Categories 2
through 4 are more severe and show necrosis involving the
whole body. In these stages sea stars can be seen with white
lesions surrounding their bodies and are accompanied by
missing limbs. Category 4 is the most severe stage, many sea
stars are missing multiple limbs and necrosis causes death.
Impact on the EcosystemDrew Harvell, a professor of ecology at Cornell University, says
"it is happening at such a large scale to the most important
predators of the tidal and sub-tidal zones. Their disappearance
is an experiment in ecological upheaval the likes of which we've
never seen." Removal of sea stars would cause an imbalance in
the ecosystem because "starfish [are] the 'keystone' species
governing biological diversity in the entire intertidal zone"
(Keystone Species Hypothesis). A keystone species can be
defined as a species that is important to a specific community.
The removal of a keystone species usually triggers a change in
the community it inhabits. Robert T. Paine was an ecologist who
coined the keystone species theory. He studied the removal of
the purple sea star (Pisaster ochraceu) on Tatoosh Island in
Washington and discovered that when the sea stars
disappeared the population of mussels increased.
Without the presence of sea stars the competition in the
intertidal community will increase. Food and space will be limited
and will most likely lead to a population decline in other
invertebrates that inhabit these communities. Mussels, whose
key predators are the sea star, will overtake communities leaving
no room for other organisms. Sometimes the disappearance of a
keystone species can lead to extinction of entire species of
organisms.
Sea Star Wasting Disease
and the Impact on its Ecosystem
By: Sue Ellen Yu
Biology 115, Miramar College
AbstractSea stars believe it or not, are important species in many
intertidal zone areas. They play an important role in the balance
of the marine ecosystem. However, with the introduction of a
mysterious disease off the west coast of North America, the sea
star population has been at a decline. What is this mysterious
disease that is impacting the sea star populations and what types
of sea stars are affected? Although there are many questions
regarding sea star wasting disease, many questions are left
unanswered because research is still ongoing. This poster will
introduce what sea star wasting disease is, what causes it, and
how important sea stars are to their communities.
IntroductionEchinoderms, commonly known as sea stars, are benthic
invertebrates found in many different areas like: lagoons, tide
pools, surf grass, and kelp forests. Although many people refer
to these organisms as starfish, they are not fish. Unlike fish,
these organisms lack a backbone and are invertebrates. Sea
stars are related to sea urchins, sea cucumbers, and brittle stars.
They can range in size depending on species and although
considerably small compared to other animals they play an
important role in the ecology of their environment. However, just
recently, there has been a mysterious disease plaguing the sea
star community along the west coast.
Cause of the DiseaseSince the first spotting of this disease scientists have been
baffled by what causes it. At first researchers thought that the
changing environment played a factor. A combination of warmer
waters, ocean acidification, and microorganisms could be the
reason behind the population decline. However, scientists at
Cornell University believe they have narrowed it down to
densovirus. This densovirus, SSaDV, was seen in museum
specimens as early as 1942. Although it was found in museum
specimens, the virus was only present at low levels so it served
no serious threats to organisms. Scientists believe that the virus
could have mutated and changed along with its environment
causing the virus to grow stronger. Even though they believed to
have narrowed it down to this virus, researchers still have many
questions: "Why now? What is it that changed that created the
conditions for this outbreak? And we don't have the answer to
that. But certainly a viral mutation would be one explanation"
(Drew Harvell, Cornell University). Ongoing research is still
happening today and everyday researchers are discovering
something new about this mysterious epidemic.
Figure 1: Ochre sea star. Figure 2: Six-armed star.
SourcesDunham, Will. "Virus Implicated in Massive Die-off of North American Starfish." Reuters. N.p., 17 Nov. 2014. Web. 15 May 2015.
<http://www.reuters.com/article/2014/11/17/ us-science-starfish-idUSKCN0J129K20141117>.
"Keystone Species." Kennesaw State University. N.p., n.d. Web. 15 May
2015.<http://science.kennesaw.edu/~jdirnber/ecology/Lecture/LecComEcol/LecCommImportance/PaineComm.JPG>.
"Ochre Star." Friends of La Jolla Shores. N.p., n.d. Web. 15 May 2015. <http://friendsoflajollashores.com/marinelife/wp-
content/gallery/ochre-sea-star/ochre-sea-star_7669304298_o.jpg>.
"Pacific Rocky Intertidal Monitoring: Trends and Synthesis." University of Santa Cruz Ecology and Evolutionary Biology. N.p.,
n.d.Web.15 May 2015. <http://www.eeb.ucsc.edu/pacificrockyintertidal/data-products/sea-star-wasting/>.
"Sea Star Wasting Syndrome Map." Map. Pacific Rocky Intertidal Monitoring: Trends and Synthesis N.p., n.d. Web. 15 May 2015.
<http://data.piscoweb.org/marine1/seastardisease.html>.
"Six Armed Star." Walla Walla University. N.p., n.d. Web. 15 May 2015.
<http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Echinodermata/Class%20Asteroidea/
Leptasterias_aequalis3sDLC2005.jpg>.
"Sunflower Star." Friday Harbor Marine Health Observatory. N.p., n.d. Web. 15 May 2015.
<https://fhmho.files.wordpress.com/2011/04/sunflower-star2.jpg?w=300&h=225>.
Virus Fingered as Top Suspect in West Coast Sea Star Wasting Disease. Washington DC: US Fed News Service, 2014.
ProQuest. Web. 15 May 2015. <Including US State News Retrieved from
http://search.proquest.com/docview/1626377739?accountid=38871>.
Figure 4: Map of sea star wasting disease sightings along the west coast of
North America.
Figure 5: Category 1 sea star with lesions
on the arm.
Figure 6: Category 3 sea star, necrosis
has begun. White lesions can be seen
throughout the body.
Figure 7: Category 4 sea star shown. Full
decay of the body and limbs causes
death in organism.
Figure 3: Sunflower star.
Figure 8: The sea star is the top consumer in this community. This figure shows that if the sea
star is removed then its prey, the primary consumers, will take over the community. This can
cause overpopulation and more competition for the already crowded intertidal community.
