In Situ Analysis of a Sea Star Wasting Episode in Carmel Bay

8/10/2019 In Situ Analysis of a Sea Star Wasting Episode in Carmel Bay

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IN SITU ANALYSIS OF A SEA STAR

WASTING EPISODE IN CARMEL BAY

Ari Freedman

Carmel High School

Abstract

When I became interested in scientific diving, I learned about a current sea star wastingdisease episode plaguing West Coast sea stars and decided to investigate if this disease

was affecting local Asteroids. After preliminary visits to my study sites, the shallowsubtidal and intertidal zones of North Monastery Beach, I observed that two Asteroid

species, Asterina miniata and Dermasterias imbricata, were very resistant to the spreadof the disease, and I hypothesized that collecting more data would substantiate this

observation. On every data-collecting session, my advisor and I would stretch out 30meter transect lines and tally off every sea star species along the way. I observed signs of

wasting disease at North Monastery Beach in an episode that seemed to be morestochastic than deterministic in its distribution and lasted two months, from early

December 2013 to late January 2014. I found that Pycnopodia helianthoideswas the firstspecies to be affected, then Pisaster ochraceus, and Pisaster giganteus was the last

species to experience die-offs. Asterina sp. and Dermasterias sp. showed hardly anysigns of mortality. The distribution of wasting disease seems to be more stochastic than

deterministic geographically and on a species level. The other species of stars I studiedwere not numerous enough to lead to any reliable conclusions. Thus, my hypothesis was

strongly supported, leading to questions for further study, such as documenting sea starrecovery from wasting disease and investigating the scientific reason behind the

resistance to wasting disease ofAsterina sp.andDermasterias sp.


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Introduction

In reference to the sea starPisaster ochraceus, Ed Rickets, a biologist and good friend ofJohn Steinbeck, once said that anything that can damage this thoroughly tough animal,

short of the acts of God referred to in insurance policies, deserves respectful mention(Ricketts and Calvin 215). Thus, it is quite dramatic to see up to 95 percent of [this]

particular species of sea star in some tide pool populations essentially melt in front ofyou (Widespread starfish deaths reported on West Coast).

Sea star wasting disease is a cyclical event that effects sea stars along the Pacific coast. A

large outbreak of it has recently occurred over a widespread range, from Alaska toSouthern California, and though it began during this past Summer, 2013, media reports

covering this wasting phenomenon only came to my attention last November.

During last summer, I decided to get certified for Open Water Diver, the most basic

SCUBA diving certification, for simply recreational purposes. It was only when schoolstarted that year that my physics teacher, Mike Guardino, mentioned that he

could take me diving locally and teach me the basics of scientific diving. So onsubsequent dives, Mike taught me the fundamentals of scientific navigation and

sampling, including finding study sites using a compass, the calibration of kickcycles, and sampling using line transects and square and circular quadrats. This

went on until November 10, when an article in the Monterey Herald caught myeye, entitled Widespread Starfish Deaths Reported on West Coast. In it, the

article raised the issue of sea star wasting disease suddenly erupting in starfishfrom Alaska to Southern California usually affect[ing] one species,Pisaster

ochraceus. With this in mind, I practiced my sampling techniques that day atNorth Monastery Beach on justP. ochraceusand its close relativeP. giganteus,

instead of sampling other species of stars like we had previously been doing. Although I

saw no stars that were wasting that day, I noticed that there had been a significant declinein both species, especially P. ochraceus, and presumed that it was due to wasting. The

fact that this was a serious current and local biological problem suggested that this wouldmake an excellent opportunity for a science fair project, so I decided to study the wasting

problem in more depth at my study site of North Monastery Beach.

Over the next several dives, Mike and I resumed sampling in the same consistent manner,using 30m transect lines parallel to the shore, but opening the surveys up to more local

species. And although I still saw no wasting disease on these dives, I recorded significantdeclines in other species in addition toP. ochraceus, commonly known as ochre stars. In

fact, it seemed that the only sea stars not afflicted with the die-offs were bat stars

(Asterina miniata) and leather stars (Dermasterias imbricata). That is not to say thatthese two species never showed signs of wasting, but compared to some of the moreaffected stars, like sunflower stars (Pycnopodiahelianthoides), bat and leather stars were

hardly touched. So I decided to make it the goal of my project to get as large a samplesize as possible in order to support the claim that there is some biological aspect of these

two stars that sets them apart from the curve. I knew that to find out the cause would beimpossible, since not even the worlds top scientists had yet been able to discover the

main cause of the disease itself.

An ochre star afflicted withwasting disease in North

Monastery Beachs intertidalzone


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The data I collected fell into two categories: pre-wasting and post-wasting. Even though

there was already wasting disease present, I called everything from before November 30pre-wasting to signify that the peak of mortality had not yet hit. After this, a long hiatus

of diving for my project ensued, which was broken on December 27 when Mike wentdiving solo (I did not go since I was sick) and recorded the peak of the wasting episode at

Monastery Beach. So all of the data including and after this date became known as post-wasting, ending on January 25. Since on my first two dives for this project, I was able to

finish 3 and then 4 transects, I made it a norm to collect data in chunks of 7 transects. Iwas able to only do 1 group of 7 pre-wasting transects, but in the post-wasting time

range, I completed 2 groups of 7 transects. Thus, I successfully sampled subtidalAsteroids on 6 occasions. Although I initially went on 7 data-collecting dives, the last

one, on January 26, 2014, turned out to lead to unscientific data due to variouscomplications and I had to omit its results from my project.

I also translated these same procedures into intertidal studies at Monastery. To make the

subtidal and intertidal study sites as close together as possible, I did all of my diving in

the very shallow subtidal, no deeper than 6m, and made sure that my intertidal site wasright next to this. I also made sure to do exactly 7 transects on both of my intertidal visits,one pre-wasting and the other post-wasting. However, the intertidal data does not really

transfer into the area of my project, which is to demonstrate the resistance of bat andleather stars, since there are almost none of these species present in the intertidal. Instead,

the intertidal zone at Monastery is rife with ochre stars, in which I saw a largeprogression of wasting. However, I was not able to draw any rigorous conclusions from

this intertidal data, or from data that I collected in Monterey Bay Aquariums Kelp ForestExhibit, because I only collected data from each of these places on two occasions, and

have no baseline data to compare either of them to. I was also able to get access toPISCO (Partnership for Interdisciplinary Studies of Coastal Oceans) subtidal data from

Monastery from past years to use as baseline data. Even though it was taken from South,instead of North, Monastery, there is not much geographic difference between these two

locations. I also had to manually omit all of the data taken from transects deeper than 6mbefore averaging it out, since 6m is the deepest depth from which my data was collected.

I used this baseline data as a control group with which to compare my own data, so as tobetter evaluate the effects of wasting disease on various species.

I was able to show the there was a major wasting episode occurring at North Monastery

and that something was definitely allowing bat and leather stars to resist the full effects ofwasting. It was especially curious to see bat stars feeding on other wasted stars, but

despite this direct contact with the disease, the bat stars still went away unharmed. I came

up with hypotheses as to the nature of this resistance, but I will have tosave these as questions for further study. With the limited knowledge ofthe situation and my own lack of experience, I was unable to determine

the causes behind either of these phenomena. While I learned a lotabout sea star wasting disease, in reality I came away with more

questions than answers. One important question that I could study nextis how juvenile recruitment helps to bring sea star densities back to

their baseline levels in the absence of wasting disease.A ray that fell off of a wasting giant

star in the subtidal zone


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Background Information

To understand more about the nature of sea star wasting disease, it is important to have

knowledge of some of the more general characteristics of sea stars. Sea stars are alsoknown colloquially as starfish, but since they are not fish in any sense of the word, I will

refer to them only as sea stars. Sea stars are a group of organisms belonging to the classAsteroidea. Asteroidea in turn belongs to the phylum Echinodermata, whose members are

categorized as pentaradially symmetric marine invertebrates. There are approximately7,000 extant species of Echinoderms, falling into 5 classes: Asteroidea (sea stars),

Ophiuroidea (brittle stars), Echinoidea (sea urchins and sand dollars), Holothuroidea (seacucumbers), and Crinoidea (feather stars and sea lilies).

Out of the estimated 1,500 species of extant sea star species, most have pentaradial

symmetry, with five rays radiating from a central disc. However, many species regularlyhave more, such as Leptasterias hexactis, with 6 rays, and Pycnopodia helianthoides,

which usually has anywhere from 16 to 24 rays. Irregularities in development can also

cause stars to grow extra rays, or to develop fewer than normal. For example, thoughAsterina miniatanormally has five rays, they occasionally have as many as nine (BatStar). Sea stars are opportunistic feeders that eat by bringing their stomach out of their

mouth, which is located on the bottom of the star. Because of this, the bottom side isreferred to as the oral side and the top is called the aboral side. Each ray has a groove

going down the middle of the ray on the oral side, called the ambulacral groove.Distributed along these grooves are hundreds of tiny tube feet, which are used for suction

to clamp the star onto surfaces and for locomotion, which is generally very slow. Sincesea stars lack blood, the circulation of dissolved gases and nutrients throughout their body

is instead carried out with their water vascular system. This system takes water in throughthe madreporite, a small hole located on the aboral side of the central disc, and sends it

through various canals around the central disc and down all of the rays to each and everytube foot. Reproduction in sea stars is usually done through broadcast spawning, in which

the sperm and eggs are distributed into the water column. However, certain species, likeLeptasterias hexactis, brood their young, which leads to more localized populations.

Another aspect of sea star anatomy that is present in most species is the pedicellaria.Pedicellariae are small claw-shaped structures found on both the oral and aboral surfaces

that help clean microscopic debris off the stars skin gills and keep the planktonic larvaeof sessile organisms from landing on the star. However, some species completely lack

pedicellariae, such as Asterina miniata and Dermasterias imbricata, as well as allmembers of the order Spinulosida. Since these stars do not have pedicellariae to keep

themselves clean, there are various other ways that they prevent settlement of foulingorganisms, such as with microscopic cilia or chemical defenses. Sea stars are very

important organisms to study because they are keystone predators, due to the widevariety of their diets, from scavenging to all-out predation.

Sea stars and other echinoderms seem especially vulnerable to epidemics of microbial

diseases, and instances of mass die-offs with the spread of disease are well documented(Robles 167). One major and fairly current example of this is sea star wasting disease, a

general description of a set of symptoms that are found in sea stars (Raimondi).


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The symptoms of this disease are very diverse, but most notably, affected stars showlesions in their tissue that spread from the rays to the central disc, causing necrosis and

eventually death. Also, wasting stars can be seen with their rays crossed, an unusualbehavior for sea stars, usually as a way of covering these lesions. It seems that the disease

hinders the sea stars ability to regenerate its rays, causing it to gradually melt away. Thiswhole process occurs over the span of just a few days. Though no one has yet been able

to pinpoint one universal causal agent of the disease, bacteria of the genus Vibriohavebeen shown to be involved in most cases on the West Coast. However, in other cases, it is

a virus that seems to cause the disease. It is generally speculated by authorities that anafflicted star does not die of wasting disease itself, but of a secondary infection that is

able to infect the star only once it has been compromised by wasting disease.

From past records, the onset of disease is associated with increased temperature(Robles 167). Thus, large historical events from 1983-84 and 1997-98 have both

overlapped with El Nio events that caused warm water cycles. As of this last summer,2013, the Pacific coast of the United States has experienced an episode of wasting

disease that is particularly troubling because of its spatial extent (Raimondi). This

episode, first noticed in Seattle, Washington, ranges from as far north as Alaska down toSouthern California, however, instead of hitting everywhere along the coast all at once, ithas started in the northern part of its range and gradually moved southward. Although at

first it seemed like justPisaster ochraceuswas affected, it soon became evident that mostother species of stars suffered as well, with seemingly only Asterina miniata and

Dermasterias imbricata being somewhat resistant. Just like previous wasting outbreaksalong this coast, little is known about the reason behind this epidemic, but it is certainly

puzzling that there was no warm water cycle that seemed to correlate to it. Instead, somepeople have proposed that the nuclear disaster at Fukushima could have put radiation in

the water that spread to the East Pacific by way of the North Pacific Gyre. However, thisseems not to be the case, since the radiation is due to arrive later this year, and when it

does, it probably will be too diluted to lead to mass mortalities of sea stars (Sahagun).The fact that no other marine organisms have been affected outside of Asteroidea also

refutes the possibility of radiation. It is known that the disease is transmitted through thewater column and that sea stars get infected when the pathogen gets passed through their

water vascular system, but this still does not explain why other echinoderms that alsohave water vascular systems would not be affected by this disease.

Although there has been a general trend of wasting disease moving southward during this

current episode, it has been very patchy over space and time. For example, wasting wasnoticed at Hopkins Marine Station in Monterey Bay at least two months before it hit my

study site at Monastery Beach. Even before manifesting itself there, wasting episodes

jumped down to points farther south.

Overall, this current episode of wasting disease has posed many more questions than

answers, humbling top authorities on the subject. Even in my own experience, I haveheard some of these leading authorities, including Dr. Pete Raimondi, Dr. David

Kushner, Dr. James Watanabe, Dr. John Pearse, and Dr. Sarah Cohen, admit openly thatwasting disease has left them mystified in many respects.


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When sampling sea stars for my project, I chose to focus on the ten most common seastars at North Monastery Beach, my study site in Carmel Bay. Here is a bit of information

on each of them and how they relate to wasting disease:

Asterina miniata: Also called the bat star because of the webbingbetween its rays, they lack pedicellariae and are, by far, the most

ubiquitous star in the subtidal zone, but are sparse in the intertidal.Although they scavenge on other wasted stars, they seem to be the most

resistant to wasting disease.

Pycnopodia helianthoides: Its common name is the sunflower star due toits many rays and giant size, making it the largest star in the world. In

this area, they are common, voracious predators and one of the firstspecies to die-off from wasting disease.

Henricia leviuscula: The Pacific blood star, named for its red hue, is

thought to actually be a species complex, rather than just one clear-cutspecies. It is the only local star of the order Spinulosida that I studied,and thus lacks pedicellariae, however, it is too uncommon to conclude

how it reacts to wasting disease.

Dermasterias imbricata: This is known as the leather star because of itssmooth texture. They also lack pedicellariae and are the only other star

found locally that showed obvious resistance to wasting disease. Theyare relatively common in the subtidal, but less abundant in the intertidal.

Orthasterias koehleri: Its common name, the rainbow star, comes fromits variety of hues of yellow to pink. It was a prime target for wasting,

making it almost impossible to find after the onset of the wasting event.

Pisaster ochraceus: By far the most abundant species in the intertidal,this star, commonly known as the ochre star because of one of its color

morphs, is found only in the very shallow subtidal. It showed signs ofwasting disease early on, and because it is the most conspicuous of the

open-coast animals, it was the first species with wasting to catch thepublics eye (Rickets and Calvin 214).

Pisaster giganteus: This close relative to the ochre star, commonlycalled the giant star due to its large size, is fairly common subtidally,however not intertidally, and showed the most conspicuous signs of

wasting subtidally in this area.


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Pisaster brevispinus: This is the giant pink star, scientifically named forits short spines and is closely related to the ochre and giant stars. It is too

uncommon in this area to draw any conclusions on how it reacted towasting disease, but it seemed to have been wiped out by it.

Mediaster aequalis: This star is sometimes called the vermillion sea starbecause of its rich, consistent color. It is one of the only local stars

belonging to order Valvatida, along with Asterina miniata andDermasterias imbricata, but is too rare to conclude how it reacted to

wasting disease.

Leptasterias hexactis: Just like Henricia sp., the six-rayed sea star has

been proposed to be a species complex due to its localized populations,caused by being the only species in this area to brood its young. Though

they are relatively common, their small size and cryptic coloration makethem very tough to find, and consequently, to draw conclusions about

their vulnerability to wasting disease.

The following cladogram demonstrates the phylogenetic relationship between thesespecies and other echinoderms.

)*+,-+./+01.234516 758.. 9:;+:


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Hypothesis

I hypothesize that a sea star wasting episode of finite duration will occur at North

Monastery Beach, and that some species will be more vulnerable than others. From my

preliminary surveys, I suspect that Asterina miniataandDermasterias imbricatawill be

the most resistant to this wasting episode.

Materials

Subtidal (North Monastery Beach):

SCUBA gear

Transect tape measure (at least 30m long)

2 metal measuring sticks cut off at exactly 1m

2 blank data tables printed on Rite in the Rain All-Weather Writing Paper

2 underwater slates 2 Cretacolor graphite sticks

Underwater camera (PENTAX Optio WG-2)

Intertidal (North Monastery Beach):

Transect tape measure

2 metal measuring sticks cut off at exactly 1m

2 blank data tables printed on Rite in the Rain All-Weather Paper

2 clipboards

2 rubber bands to hold papers to clipboards

Several pencils (in case one gets lost) Underwater camera (in case it gets wet)

Aquarium (Monterey Bay Aquarium):

Surveying the Kelp Forest Exhibit

o MBA volunteer diver status

o SCUBA gear (see subtidal materials for more detail)o Blank piece of Rite in the Rain All-Weather Writing Paper

o Underwater slates

o Cretacolor graphite stick

Surveying the touch poolso Blank data table printed on regular paper

o Clipboard

o Rubber bando Pencil

o Camera (iPhone)

Intertidal surveying setup, with

transect line, clipboard, and metalmeter sticks


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Procedures

Subtidal (North Monastery Beach):

1. Get in the ocean, swim along the edge of the kelp forest, and drop down at around 3mdepth.

2.

Stretch out the 30m measuring tape parallel to shore for use as a transect line.3. For each transect, two people swim along the transect line, each on one side, holding

the 1m metal measuring stick perpendicular to the line to count all of the stars withina meter of it, tallying them off on the data table along the way with the graphite stick.

4. Once at the end of the transect line, roll it back up and swim to a nearby location to

start another transect parallel to the shore.5. Finish anywhere from 2 to 5 transect lines on one dive depending on air capacity, and

making sure to finish a total of 7 transects on consecutive dives.6. Along the way, take pictures with an underwater camera of

wasted stars and healthy stars for comparison.7. Once out of the water, create a dive log to record the technical

aspects of the dive, then transfer the star counts from the datatables into Microsoft Excel, adding up the tallies from both

divers data tables.

Intertidal (North Monastery Beach):

1. Stretch out the 30m measuring tape along the edge of theintertidal to use as a transect line.

2. At the end of each transect line, roll it back it up and start another where the previousone ended.

3. Finish 7 transects in one visit, since air is not a limiting factor.4. Along the way, take pictures with an underwater camera of wasted stars and healthy

stars for comparison.5. Later, create a tidepooling log to record the technical aspects of the excursion, then

transfer the star counts from the data tables into Microsoft Excel, adding up the talliesfrom both peoples data tables.

Aquarium (Monterey Bay Aquarium):

One person surveys MBAs Kelp Forest Exhibit1. Divide the blank piece of underwater paper into sections of Sand, Rock Reef,

and Walls/Windows/Ledges.

2. Fasten the data table on waterproof paper into the underwater slate.

3.

Enter the Kelp Forest Exhibit, and after fulfilling maintenance duties, swimaround the exhibit and, with the graphite stick, tally off every bat star into one ofthe three mentioned categories based on where they were found, and any other

species of star gets tallied on the side regardless of its location.4. Along the way, hold wasted stars up to glass for the person outside surveying the

touch pools to take pictures of.5. After getting permission from MBA to use their data, enter into Microsoft Excel

Investigator demonstrating subtidal transe

procedure


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Another person surveys MBAs upstairs and downstairs touch pools.1. Mark one column on the data table as the upstairs touch pool and another column

as the downstairs touch pool.2. Put the data table on regular paper into the clipboard, and fasten the bottom of it

with a rubber band.3. Starting at the upstairs touch pool, walk around it and carefully tally every star

onto the data table under the upstairs touch pool column.4. Go to the downstairs touch pool and do the same procedure, only tallying on the

column for the downstairs touch pool.5. Along the way, take pictures of stars in the touch pools and the wasted stars that

the person surveying the Kelp Forest Exhibit holds up to the glass.

Results

From the various graphs displayed in my report, one can draw numerous conclusions

relating to sea star wasting disease for five of the species I studied subtidally. The other

five species I investigated (Henricia leviuscula, Orthasterias koehleri, Pisaster

brevispinus, Mediaster aequalis, and Leptasterias hexactis) were too uncommon or

obscure to begin with at North Monastery Beach for comparison with the baseline data to

yield any conclusive statements about them. It is important to note that the relative peak

of wasting overall was noticed on December 27, 2013, and everything before this peak is

referred to as pre-wasting, while everything afterwards is post-wasting. Before delving

into the details of these graphs, it is also necessary to go over how each was derived and

their significance, noting that all densities referred to are over an area of 60m2, the

sample area of the transects done for this project.


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Analysis

Asterina miniata:

Looking at Graph 1, it is made obvious that Asterina miniata clearly was not affected

adversely by wasting in the timeframe studied. On the contrary, they showed a significant

increase, from an average density of 14 to 53.33, an increase of nearly 4 times. However,

Graph 2 shows that the densities go from a meager 31.78% to 121.07% of the baseline for


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Asterina sp. This shows that it is not the end result that is significantly high, but rather the

beginning that is significantly low. Analyzing Graph 3 shows that in comparison with

some of the other species, the progression of Asterina sp. is not actually very spread out

in relation to its universal average, meaning that this seemingly enormous increase is not

actually very unusual. Graph 5 demonstrates that the growth of this species is a fairly

linear progression, since the beginning and end are similar distances away from theuniversal average, which falls around the middle of the time period. Graph 5 also

supports the fact that Asterina sp. did not start out very numerous compared to its

baseline and breached the baseline very late in the duration of the study. All of these

pieces of information suggest that for some reason, numbers of this species started out

initially low, and then thrived as a result of the wasting disease. However, this initial low

point could not have been caused by wasting disease, since it was outside of the duration

of the North Monastery episode. Graph 4 supports this by showing that at the peak of

wasting near the end of December, 2013, only 10.08% of stars were affected, while

Pisaster spp.were not so fortunate. The Aquarium data is perhaps the largest supporter of

the claim that Asterina sp. is almost resistant to wasting disease. In the Kelp Forest

Exhibit, a normally diverse arrangement of Asteroids, there were 172 Asterina sp. and

only 4 stars of other species on December 21, 2013, and on January 11, 2014, there were

182Asterina sp.and only 2 stars of everything else. The numbers of Asterina sp. stayed

fairly normal for this exhibit, while everything else became extraordinarily scarce as a

result of maintenance divers having to constantly pull wasted stars out of the exhibit.

Pycnopodia helianthoides:

Graph 1 certainly gives a dismal first impression for the numbers of Pycnopodia

helianthoides, with all of the densities 0 except for those from the first two days. It is not

truly apparent just how significant this number of 2.33 is until it is compared with the

baseline forPycnopodia sp.Graph 2 does this by showing that the density of 2.33 on the

first day is 277.38% of the baseline average, almost 3 times as much. Graph 3

accomplishes a similar task, but in a much more dramatic way, showing this first density

to be the most unusual number of all the data, with a tremendous 613.16% of its universal

average from my data. This large number implies that the universal average of the data

for Pycnopodiasp. is relatively small, taking into account all of the 0 entries for its

density. Therefore, this shows that this species had a speedy, significant decline, perhaps

the most so of any of the species studied. The line for Pycnopodia sp. is invisible in

Graph 4, due to all of the 0 entries and the division by zero that arises from using thisgraphs formula. This suggests that there was so much wasting in this species, that they

just disappeared. Graph 6 nicely exhibits the shape of the steady decline that occurred

with this species in response to wasting, and shows that, first date aside, the densities of

Pycnopodia sp.are consistently far below its baseline number.


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Dermasterias imbricata:

As forDermasterias imbricata, Graph 1 is not very helpful, other than showing that this

star is the most common aside from Asterina miniata. It is not until comparing

Dermasterias sp.with its baseline number in Graph 2 that it becomes apparent just how

significant their densities were, as much as 9 times greater at one point. These high

percentages come from the fact that the historical baseline average forDermasterias sp.is so low, only .84, which is the same as the baseline forPycnopodia sp.Comparing the

two species on this graph thus shows just how much better off Dermasterias sp.was than

Pycnopodia sp.throughout this wasting episode. Though Graph 2 may make the densities

ofDermasterias sp.look rather spread out and sporadic, Graph 3 shows that, along with

Asterina sp., its distribution is the most stable and compact compared with its universal

average. However, unlikeAsterina sp., no correlation can be made withDermasterias sp.

showing that it steadily increased as a result of wasting, as is made apparent by the

enlarged shape of its distribution shown in Graph 2. Graph 4 shows that very few stars of

this species were wasted, with the most being 7.89% during the wasting peak, even less

than that of Asterina sp. As a result of not suffering from wasting disease, Graph 7

illustrates that the densities ofDermasterias sp.were consistently higher than its baseline.

Pisaster ochraceus:

Graph 1 shows that Pisaster ochraceus was the least common of all the subtidal stars

shown in these graphs. However, this is to be more or less expected, sinceP. ochraceusis

primarily an intertidal species and is relatively scarce in the intertidal, especially at depths

deeper than 6m. Thus, its baseline number is also very small, only .21 stars per 60m2.

However, Graphs 2 and 8 show that just like Pycnopodia sp., Pisaster ochraceus was

always lower than this baseline except on the first day. But unlike Pycnopodia sp.,

Pisaster ochraceusdid not have a nice steady decline, but instead was very sporadic and

relatively spread out, as is shown by Graph 3. The jumpiness of the distributions of P.

ochraceus is attributed more than anything to its rarity in the subtidal. Instead, the

intertidal data is more valuable in showing the affect of wasting on P. ochraceus. Not

only did the average intertidal density ofP. ochraceusdecrease from 5.29 on November

30, 2013 to 2.71 on December 29, 2014, but on these same two days, the average percent

of wasting rose from 0% to 15.79%, with many other wasted stars seen on the second day

off-transect.

Pisaster giganteus:Just looking at Graph 1, it seems that Pisaster giganteusfollowed a very similar trend to

Dermasterias sp.in its densities over time. However, compared with their baseline data,

P. giganteusdid not even come close toDermasterias sp., as is shown in Graph 2. And

unlike P. ochraceus, P. giganteus is normally more abundant in the subtidal, with a

baseline average of 3.95 stars per 60m2. Graphs 2 and 9 both show that despite a low data

point on the first day of sampling,P. giganteusstarted out right around the baseline, and


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then plummeted below the baseline for the rest of the duration of the disease. The small

increase shown on the last day in Graph 9 could possibly show signs of recovery, but is

more likely just due to the error involved in sampling any star species. It could also be

due to the fact that wasting disease caused the populations of P. giganteusto be relatively

unstable, as is shown in Graph 3. Perhaps the largest piece of evidence that correlates the

decline of P. giganteus with wasting disease is shown in Graph 4. Not only does thepercentage of wasting show a steep and fairly linear increase inP. giganteusover time,

but it even reaches 100% on January 18, 2014, the only species to do so. The fact that

despite this dramatic showing of wasting disease,P. giganteusdid not show as marked of

a decline as P. ochraceusor Pycnopodia sp.suggests that P. giganteusprobably takes a

longer time to die as a result of wasting disease than do these other species.

Conclusion

After thoroughly analyzing the data collected at North Monastery Beach, I found that my

hypothesis concerning the relative resistance of Asterina miniata and Dermasterias

imbricata to sea star wasting disease was strongly supported. Pycnopodia helianthoides,

Pisaster ochraceus, Pisaster giganteus, on the other hand, suffered major declines as a

result of wasting disease, with the die-offs occurring roughly in the order just mentioned.

The wasting episode fell fairly accurately within the timeframe I studied, from November

25, 2013 to January 25, 2014, with the wasting peak for most species (except for Pisaster

giganteus) recorded right in the middle, on December 27, 2013.

This duration of roughly 2 months seems to be consistent with wasting episode durations

from other places, such as Hopkins Marine Station in Monterey, California and Seattle,

Washington. Since the disease was seen much earlier in Seattle and Alaska and still has

not been noticed down south in the Channel Islands off of Santa Barbara, it seems that

wasting disease has been moving generally south, probably in accordance with the North

Pacific Gyre.

On a more specific scale, however, the spread of wasting seems to be more patchy. For

example, after wasting disease first showed up at Hopkins Marine Station north of

Monastery Beach, it initially skipped over Monastery, instead manifesting itself in Jade

Cove 60 miles to the south before arriving at Monastery a month later. Rather than being

completely deterministic, wasting disease is more stochastic in its distribution. Even on aspecies level, there are always some individuals that will be infected with wasting and

then others that stay completely healthy. Since wasting disease is so stochastic in its

nature, it is impossible to run categorical statistical analyses on my data, such as a chi-

square test. Also, since the average densities of some stars are so low, the expected values

derived from a chi-square test are too low to yield accurate statistical results.


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Although my data led to fairly conclusive results, there were many possible error sources

that were not within my control to resolve. First of all, there is always a lot of error

involved in sampling sea stars, or any life form. For example, in Monterey Bay

Aquariums Kelp Forest Exhibit, the number of Asterina miniata rose from 172 on

December 21, 2013 to 182 on January 11, 2014. Since no new stars were added to the

exhibit between these dates, the variability must come from stars hiding in crevices alongthe exhibits fake rock walls. Also, some sea stars, like Leptasterias hexactis and

Henricia leviusculaare so small and cryptic in coloration that it takes intense scrutiny to

find them.

The PISCO baseline data I utilized also may have its faults. For one, the people who

collected it may have deployed different or inconsistent techniques from those that I

utilized. Also, many of their transects were taken at locations much deeper than mine.

Taking the averages of the beginning and end depths for each of my transects, I found

that the deepest of mine was 6m, so I took out all of the PISCO transects that were deeper

than 6m to make it more controlled. However, on average, their transects were still a lot

deeper, since their shallowest one was at 4.6m, whereas mine was shallowest at 3m. This

discrepancy explains why their numbers for Asterina miniata(a deep water species) are

so high in relation to mine and why their numbers forPycnopodia helianthoides,Pisaster

ochraceus, Pisaster giganteus, and especially Dermasterias imbricata (all shallow

subtidal species) are so low. A possible reason the great increase ofAsterina sp.over the

wasting duration may have come from the observation that they scavenge on wasted

stars, giving them a more abundant food source. Another minor discrepancy in the

PISCO data may have come from the fact that their two sampling areas came from South

Monastery, whereas mine were all done at North Monastery, 300m to the north. As for

intertidal and Aquarium baseline data, I was not able to get access to these, which

disallowed me from drawing scientific conclusions from my data at these locations

In the future, there are many new directions I could take to continue my research on

wasting disease. One obvious follow-up to documenting the decline of sea star

populations due to wasting disease would be to document their recovery over an extended

period of time and note how sea star populations return to baseline conditions. If I were

to take up on this, then I could also measure levels of juvenile recruitment and note how

this contributes to the stars recoveries. Another research question that arises would be to

search for the cause of wasting disease, however, this is probably out of my scope,especially since top authorities still have not been able to isolate a cause and I am far

away from even being eligible for a collecting permit. Likewise, trying to scientifically

prove what the reason behind the resistance of Asterina miniata and Dermasterias

imbricatato wasting disease would be equally difficult. However, I have come up with a

few speculations as to why this resistance exists. One attribute that sets these two species

apart is their phylogeny, namely that they are the only stars, along with Mediaster


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aequalis, that belong to the order Valvatida. It is possible that there is some characteristic

that all members of Valvatida share that is absent in all other orders of starfish, and this

characteristic may lead to a resistance to wasting disease. If this were the case, then

Mediaster sp. should also be resistant to wasting disease, however, they are too

uncommon in this area to determine if they are. Another possibility could come from the

fact thatAsterina sp.andDermasteriassp.are the only local species, along withHenricialeviuscula, that lack pedicellariae. Thus, as a replacement mechanism for fending off

fouling organisms, these species may use chemical defenses that other species do not

have which may help them resist wasting disease. Again, if this were true, then Henricia

sp.should also show resistance to wasting disease, but they are too hard to find to prove

or disprove this hypothesis. As has been a common phenomenon when studying wasting

disease, my project has led to far more questions than answers.

Acknowledgements

Along the way, I received assistance and guidance from many people, all of whom I am

indebted to. The most thanks goes to Mike Guardino for bringing me up to the level of

scientific diving. In the past, he taught a class on Subtidal Marine Research at Carmel

High School, and during the summer, he dives for the National Park Service at the

Channel Islands. He took me diving and tidepooling on numerous occasions, each time

getting me the proper equipment and filling up

the SCUBA tanks. Since it is standard protocol

to never dive alone, I dove and collected all of

my data in conjunction with him. He only

collected data without me for the purposes of my

project twice, both times because I was sick. He

drove me to our dive and intertidal sites, once to

Santa Cruz, and a few times to the Monterey Bay

Aquarium. At the Aquarium, he took me behind

the exhibits, since he volunteers there, and he

surveyed all of the stars in the Kelp Forest

Exhibit two times, since I am not certified to

dive in the Aquarium. My parents helped me out

in buying me an underwater camera and by

driving me to Mr. Guardinos house, My dad

also connected me with marine biologists who

aided me in deciding the aim of my research and helped in formatting my display board.

Dr. Dave Kushner, who runs the marine lab at Channel Islands National Park, gave me

the idea that wasting is a cyclical event from which sea stars will always recover. Mike

drove me up to Santa Cruz to talk with Dr. Pete Raimondi, who is tackling the wasting

problem from USCSs Long Marine Lab, and he confirmed a lot of the effects of wasting

From left to right: Dr. James Watanabe, investigator, and Dr. John

Pearse. This image was taken at Hopkins Marine Station next to Dr.

Watanabes lab.


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that I had been seeing. He also suggested that I could study the resistance of bat and

leather stars, and, like all of the other scientists I conferred with, admitted that there are

many more question than answers pertaining to wasting disease. Dr. Sarah Cohen from

UCSF suggested that I could look at the effects of wasting on the brooding populations of

Leptasteriasspp.Dr. James Watanabe and Dr. John Pearse at Stanfords Hopkins Marine

Station told me that I could study the duration of wasting and how that changesgeographically. I also thank Dr. Watanabe for allowing me to use pictures from his

website in my Background Information. Emily Saarman at Long Marine Lab was

immensely helpful in sending me PISCO baseline data to use as a control to compare my

own data to. And lastly, George Tattersfield helped me construct and statistically analyze

the graphical representations of my data.

Works Cited

"Bat Star."Animals and Experiences. Monterey Bay Aquarium, 2014. Web. 02 Mar.

2014.Gong, Allison. "A Plague of Stars." Web log post.Notes from a California Naturalist.

WordPress, 7 Sept. 2013. Web. 02 Mar. 2014.Hoppin, Jason. "Sea Stars Wasting Away." The Monterey County Herald17 Nov. 2013:

n. pag. Print.Raimondi, Pete. "Pacific Rocky Intertidal Monitoring: Trends and Synthesis."Ecology

and Evolutionary Biology. UCSC, 2012. Web. 02 Mar. 2014.Ricketts, Edward Flanders, and Jack Calvin.Between Pacific Tides. Stanford, CA:

Stanford UP, 1968. Print.Robles, Carlos. "Pisaster ochraceus." Starfish: Biology and Ecology of the Asteroidea.

Ed. John M. Lawrence. Baltimore: Johns Hopkins UP, 2013. N. pag. Print.

Sahagun, Louis. "Study to Look out for Radioactive Kelp." The Monterey County Herald17 Jan. 2014: n. pag. Print.

Turner, Richard L. "Echinaster." Starfish: Biology and Ecology of the Asteroidea. Ed.John M. Lawrence. Baltimore: Johns Hopkins UP, 2013. N. pag. Print.

Watanabe, James M. "Asteroidea." SeaNet. Stanford, 10 Oct. 2009. Web. 02 Mar. 2014."Widespread Starfish Deaths Reported on West Coast." The Monterey County Herald10

Nov. 2013: n. pag. 10 Nov. 2013. Web. 22 Jan. 2014.Zubi, Teresa. "Echinoderms (Starfish, Brittle Star, Sea Urchin, Feather Star, Sea

Cucumber)." Starfish. N.p., 27 Feb. 2013. Web. 02 Mar. 2014.

Picture Credits for Background Information: James Watanabe, Hopkins Marine Station

In Situ Analysis of a Sea Star Wasting Episode in Carmel Bay

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