Marine biology lab report- Mitchell Ray Pranata

Title: The effect of different salinities on the rate of

activity, physique and mortality of sandworms and

bloodworms.

Abstract:

This report presents the effects of changing different

salinities (20 ppt, 30 ppt and 40 ppt) on two species of

worms, the bloodworm (Glycera dibranchiata) and the sand worm

(Nereis Virens). All worms were placed in six different

aquariums (three tanks for each species, with each tank

containing 35 worms) that were filled with different

salinities and were weighed using a precision scale after

several time periods (at 0 hour, 4th hour, 8th hour and 24th

hour). Their activity levels and mortalities were also taken

into account. The values obtained were prone to inaccuracy

corresponding to the difference in removal of free surface

water off the worms before weighing them. However, the

results were supportive of the hypothesis. The sandworm,

being osmoregulators, is shown to be returning to a 0%

1

(normal) weight change whereas the bloodworm, being

osmoconformers (low tolerance), is shown to be drifting

further apart from the 0% (normal) weight change mark as

time increases. Analysis shows that sandworms have a lower

mortality rate and are able to withstand different

salinities in comparison to the bloodworms, vice versa. It

also shows that the sandworms, being osmoregulators, are

returning to their normal weight whereas the bloodworms are

drifting further apart from its initial weight as time

progresses.

Introduction:

Each organism has a set of individual requirements and

adaptations needed in order to thrive in its environment.

For instance, the musk ox that lives in the vast Alaskan

Tundra is well adapted to the harsh, cold environment by the

presence of its thick fur-coat that shields the ox from

frigid temperatures. However, significant changes in the

environment can affect an organism and different organisms

may react at variance.

Estuaries, by definition, are partially enclosed water

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bodies that form at the transitional areas between

freshwater and seawater. Despite of being interconnected,

estuaries and oceans are dissimilar environmental

ecosystems. Safeguarded from the ocean’s rough oceanic

forces by peninsulas, estuaries, or ‘nurseries of the sea’

are highly productive environments with a rich ecosystem for

various organisms.

Salinity, as the word suggests, is the measure of

concentration of salt in a solution of water. The more

saline a water solution is, the more salt it contains, vice

versa. Some organisms are well suited and can only survive a

certain level of salinity, while other organisms are able to

tolerate and adapt to different salinity levels.

In the open ocean, the salinity is measured at a

constant 35 ppt (parts per thousand), while in estuaries,

salinities range from 0-35 ppt depending on each estuary.

The highest salinity is recorded where the ocean water flows

in, and lowest where freshwater flows in. The salinity, or

concentration of salt in freshwater is so low that it’s

close to zero.

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Organisms that reside in the ocean are generally

‘stenohaline’, meaning that they are unable to tolerate wide

fluctuations in salinity levels. On the other hand, since

estuaries have an unstable salinity level, organisms that

live in estuaries are generally ‘euryhaline’, meaning that

they are able to tolerate wide fluctuations in salinity.

Poikilosmotic organisms (also known as osmoconformers) match

their body’s osmolarity with the environment through

osmosis, which in turn provides identical salinity with the

organism’s surrounding environment. On the other hand,

homoiosmotic organisms (also known as osmoregulators)

regulate an independent osmolarity in their bodies

regardless of the environmental conditions, therefore

keeping a constant salinity level inside their bodies.

Oysters for example, are Poikilosmotic organisms and

stenohaline as well because a huge fluctuation in salinity

levels would affect their growth and activity negatively. On

the other hand, the salmon fish is euryhaline organism which

is able to self-regulate its body to suit both ocean and

fresh water.

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Two species of worms from different genus will be

experimented on; the sand worm (Nereis virens) and the blood worm

(Glycera dibranchiata). Both these worms live alongside one

another in estuaries, but are different from one another.

They are both annelids (segmented bodies). The sand worm has

more than 200 segments that have parapods (similar to legs)

on each segment that allow them to squirm and limp in order

to move themselves. Sand worms can be found on both sides of

the North Atlantic, France and the United States east coast.

These carnivorous worms feed on tiny invertebrates and on

organic waste material (such as glutamic and aspartic acid).

These worms are capable of inflicting a bite through two of

their sharp jaws found in their mouth, painful even for a

human. Furthermore, they have a pair of antennae and two

pairs of eyes and prefer to reside in muddier environments.

They are euryhaline and are able to tolerate various

salinities, even one ranging to near zero. (*See figure 5)

In contrast, bloodworms are osmoconformers and

stenohaline organisms. Each one has over 300 segments in its

body with less developed parapods compared to the sandworm

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and an eversible proboscis which houses four sharp jaws that

can inflict a poisonous bite. Bloodworms receive their names

due to their translucency, which enables its red body fluids

to be visible through the naked eye. Like the sand worms,

they are also carnivores and will prey upon invertebrates.

They can be found from Florida to the Atlantic, and on the

West Coast of United States. Another similarity with the

sand worm is that bloodworms prefer the mud and burrow

themselves so deep within that oxygen and salinity levels

are low. By exposing these two estuarine worms in three

different salinities, we can measure their weight loss or

gain. The loss or gain in their weights meant that osmosis

had taken place and water had either entered or exited the

worms. (*See figure 6)

Hypothesis: This experiment serves to study the effects of

various salinities on the two species of estuarine worms by

placing them in different saline solutions. The sand worms,

being osmoregulators (rather tolerant to changes in salinity

by regulating their own suitable salinities), will have a

higher mortality rate than the bloodworms. On the other

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hand, the bloodworms will have more deaths as they are

osmoconformers (low tolerance level) and will adjust to

their surrounding salinities, which may not be suitable for

their survival. Furthermore, the sand worm (euryhaline)

should not experience any weight changes, if any, little, as

they are regulating their own osmolarity. Contradictory, the

bloodworm (stenohaline) will initially increase or decrease

in weight and will maintain that weight, if not increase or

decrease more throughout the time period. The bloodworm’s

weight will continue to get further away from its initial.

Bloodworms will experience higher weight changes in

comparison to the sand worms because they will take in salt

from their surrounding through osmosis as to synchronize

themselves with their surrounding environment. Sand worms

are going to be more active in comparison to the bloodworms,

as they will not get affected by the different salinity

levels and will function normally. However, the bloodworms

will have difficulties, as they are unable to tolerate the

change in salinity levels, therefore they will become less

active.

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Rationale: By conducting this experiment, we will learn the

bloodworm and sand worm’s reaction towards different

salinities, and study their physical and psychological

status accordingly. It will show the range of effectiveness

of both euryhaline and stenohaline organisms on their

mortality rate. Through this experiment, we can learn about

the different mechanisms that these different species of

worms use in order to thrive in their environment, and how

they adjust to new ones. By knowing this, we will know the

approximate level of salinities that these worms are able to

tolerate and which ones they are unable to tolerate. We are

also able to predict the approximate internal salinities of

the worms through the weight changes and observing the

osmotic gradient trends.

Materials and method:

Setup: This experiment was done in the museum of

comparative zoology laboratory room 5088, at Oxford St,

Cambridge. It was done under normal room temperature and

conditions. The constant variables were the water saline

water used throughout, the worms, light, temperature and

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pressure in the room. There were six aquariums set up, of

which three are for sand worms and the other three are for

bloodworms. For each species, out of the three tanks, one

was filled with 20 PSU (practical salinity units) artificial

seawater, the other with 30 PSU and the final one with 40

PSU. This was done for both species of worms. There were 35

worms in each of the tank. We had been provided a precision

scale, plastic gloves and tissue in order to dry out the

worm before weighing it. Furthermore, we had a considerable

size plastic jar to move the worm from the aquarium to the

table where we were to weigh and observe them. Finally, we

had a small glass plate to place the worms after measuring

their weights, as to separate them from the worms that have

not been weighed yet. The worm’s weight at 0 hour (initial

hour, before placing them in the saline solutions) was

already measured. We were to measure the weight of the worms

at the 4th hour of submersion. Additionally, the weight of

the worms had to be measured at the 8th and 24th hour.

Method: My group consisted of three people. Initially, we

put on plastic gloves on both hands as a precaution from the

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worm’s potential danger, as both worms are capable of biting

and bloodworms have poisonous bites. Then, we chose a

designated tank (in this case, we chose the 40 PSU tank of

sand worm) and filled the plastic jar with the water from

the tank, not too much, but enough for the worms to be

submerged. Subsequently, we picked up the sand worms with

our gloved hands from the aquarium and moved it to the

plastic jar. We then took it to our table for our

observation. Before weighing out the worms, we had to blot

them on tissue paper to dry them of excess water. This was

done by gently patting the worms with tissue paper, and not

by drying them thoroughly. After removing the surface water

from the worm, we weighed the worm using the precision scale

to the nearest 0.1-gram. Before weighing the first worm, we

pressed ‘tare’, and did so after weighing every subsequent

worm. To make sure that we did not re-weigh the same worm

again, we did not rejoin the worm we had weighed back to the

plastic jar. Instead, we placed them on a dry glass plate.

Before placing them on the glass plate, we also noted down

their activity rate which ranged from being less active,

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moderately active, active and very active. We also took into

account whether there are dead worms during the observation.

We used statistical analysis and put the means into a t

test to find out the trend in weight change of the worms in

different salinities and to find out the p values.

Results:

This section provides the data collected from the sand

worm and bloodworm experiment. The experiment was conducted

with success and had very little errors in data collection.

At 0 hour, the worms were weighed as a reference to

calculate the change in weight from the 4th hour onwards.

Changes in actual percentage weight of the sandworms and

bloodworms on the 4th hour were roughly similar (in general

context). For instance, in 20 ppt, the sandworms had 40.9%

increase in their weight at the 4th hour and the bloodworms

had 46.3% increase in their weight as well (*see figure 1

and 2). Furthermore, in 30 ppt (at the 4th hour), the sand

worms had an increase of 6% in weight, while the bloodworms

had 8.2% increases in their weight (*see figure 1 and 2).

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At 40 ppt at the 4th hour, the sand worms had a decrease of

10% in their weight and the bloodworms had a decrease of 11%

in their weight (*see figure 1 and 2). The increases and

decreases at the 4th hour for all salinities on both species

of worms were similar to each other.

However, the data starts to change at the 8th hour. As

per the data, the sandworm’s actual percent change is

nearing to normal weight (0) as time progresses (*see figure

1) At the 8th hour, the sandworm’s change in weight at 20

ppt had become 38.1% and drops again to 24% in the 24th

hour. This is in line with the other salinities as well. In

30 ppt salinity, the sandworm’s percent change in weight

dropped to 4.5% in 8th hour and then to a further 1.6% in

the 24th hour time period. Lastly, at 40 ppt, the decrease

of weight in the sandworm is becoming lesser and nearing

normal weight; at the 8th hour, it only decreased by 8.1%

and at the 24th hour, it decreased by a mere 3.1% (in

comparison with the 4th hour, at which the sandworm lost 10%

in weight). This shows that after the 4th hour, the

sandworm’s change in weight is returning to an equilibrium

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and will eventually have 0 change in percent weight if

recorded over more time.

On the other hand, the data shows an opposed trend for

the species of bloodworms as the change is shown to become

further apart from 0 as time progresses (at 8th and 24th

hour- *see figure 2) Case in point, in 20 ppt solution, the

bloodworms had 48.2% change in weight at the 8th hour, and

47.1% change in weight at the 24th hour. The percentage

weight change increased from the 4th hour and it shows that

it is not returning to 0% (normal) weight change (as it is

on the species of sandworms). Additionally, in 40 ppt, the

decrease in weight for the 8th hour and 24th hour is becoming

larger and further apart from normal weight (0%). At the 8th

hour, it increased from 1.1% (4th hour) to 1.3% and then on

to 1.5% in the 24th hour.

However, some results were inconsistent. For instance,

for the species of bloodworms, the 20 ppt solution (at the

24th hour), the change in weight dropped from 48.2% (in 8th

hour) to 47.1%, although it was meant to further apart from

0 (*see figure 2). Furthermore, for the species of

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bloodworms in 30 ppt, the changes in weight generally

decreased as time progresses. It should be increasing,

however it is shown to be decreasing. There may be a logical

explanation to this and will be talked about later on in

discussion (*see fig 2, red line)

In addition to that, there was more mortality in

bloodworms than in sandworms. It is shown that in all

salinity levels, the first four hours experienced no

mortalities whatsoever. However, at the 8th hour, there was

one sandworm dead in the solution of 40 ppt. As for the

bloodworms, at the 8th hour, there was one death at 20ppt

and another two at 40 ppt. Furthermore; there were two more

sandworm deaths after 24 hours in the 40 ppt solution.

Finally, there are six more bloodworm mortalities after 24

hours, two of which belong to the 20 ppt and the other four

belonging to the 40 ppt. (*see figure 3 and 4 of mortality).

This shows that the bloodworms have a higher mortality rate

compared to the sandworms as more deaths occurred at the end

of 24 hours.

Standard deviation for the sandworms under all

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salinities is shown to decrease as time progresses. For

instance, at 30 ppt, it was 4% at the 4th hour, and then

drops to 31% in the 8th and to a further 2.8% in the 24th

hour. Contrastingly, the bloodworm’s standard deviations

were increasing as time progresses. At 20 ppt, standard

deviation at the 4th hour was 2.9%, then rose to 4.5% in the

8th hour and lastly, 5.7% in the 24th hour.

P values are less than 0.05 for both species at the 4th

hour, and are much larger than 0.05 during the 8th hour. In

the 24th hour, P values for the sandworms became smaller

than 0.05 (with one exception, which was valued at 0.075)

whereas P>0.05 in the 24 hour bloodworm category. There were

a total of 3 sandworm deaths (one died in the 40 ppt during

the 8th hour, and the other two died in 40 ppt during the

24th hour). A total of 9 bloodworm deaths were recorded

(one died in 20 ppt during the 8th hour, two in the 40 ppt

during the 8th hour, and the other 6 died during the 24th

hour, two in 20 ppt and the other four in 40 ppt).

Discussion:

The results clearly bring forth the effects different

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salinities had on the two species of worms. It was in line

with the hypothesis. As the sandworms are euryhaline

creatures, and are also osmoregulators, they are rather

tolerant and were expected to be more resistant and in turn,

have a lower mortality rate. This was shown to be true, as

the results show that at the end of the experiment, the

sandworms have less death count than the bloodworms. The

sandworm’s total death was only three. This is because they

regulate their osmolarity regardless of the unsuitable

environment outside. On the other hand, the bloodworms are

stenohaline organisms, and are also osmoconformers.

Bloodworms will match their surrounding salinity, as they do

not have control of their own osmolarity. If the salinity on

the outside is unsuitable for their survival, and it enters

their bodies, there would be mortalities. This particular

hypothesis was also accurate. There are as many as 9

bloodworm deaths in total (*see figure 3 and 4).

In both species, most of the worms are shown to be

tolerant to changes in salinity levels. However, the deaths

were irreversible damage and points out that if the salinity

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was further increased or decreased to an extreme level, it

may cause a significant increase in the mortality. Even

though bloodworms are osmoconformers and are only suited to

30 ppt salinity, they are able to tolerate both 20 ppt and

40 ppt (excluding the few deaths, which is but a small

number in comparison to the amount of worms experimented

on).

At the first 4 hours, the sandworms and the bloodworms

experienced similar weight gains and losses. It was

predicted that the sandworm, being osmoregulators, should

not experience any weight changes or just a slight change.

However, it is shown that the sandworms did experience

weight changes, even as high as 40.9%. Moreover, the

sandworms did begin to show signs of weight change

retractions, as they are slowly returning to a 0% weight

change (which is the normal weight; due to their

osmoregulation).

On the contrary, the bloodworms were expected to

regulate their salinities according to the environment they

were provided with, as they are osmoconformers. This meant

17

that they would experience a constant weight change (either

decrease or increase) and will maintain that weight change,

or become further apart than the 0% weight change. It should

diverge away from the normal weight. As soon as they take in

a salinity they’re not suitable with, they will have

difficulty adjusting and might die out. At the 4th hour,

they were shown to experience weight changes. For the 20 ppt

and 40 ppt, the hypothesis was followed as they are

diverging away from normal weight as time progresses.

However, at 30 ppt, the bloodworm’s weight change is shown

to be decreasing as time progresses (8.2% to 6.9% to 5.3%),

although not as fast as the sandworm’s decrease in weight.

This was initially thought to be an error, however it is

decreasing because of the fact that 30 ppt is very close to

normal ocean salinity. As bloodworms do live in the open

ocean, they would be very used to this salinity and adjust

easily. Therefore, their weight change is decreasing and

nearing normal weight as time progresses. Furthermore, this

also explains why the mortality rate of bloodworms at 30 ppt

is 0, whereas in 20 ppt its 2 and in 40 ppt its 4. It is

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because the bloodworms are suited to the 30 ppt and thus

will survive. On the other hand, if we changed the salinity

to 20 ppt and 40 ppt, there would be a few mortalities as

they are osmoconformers and are stenohaline.

Sandworms are very tolerant to the change in salinity

and therefore there are lesser deaths, although it is shown

that a total of 3 sandworms have died, its possible that it

is because some of them take a longer time to regulate their

bodies, as they could be weaker, or younger specimens. The

deaths could also result from psychological issues such as

stress. It is also plausible that the worms might attack one

another, resulting in their deaths.

Moreover, the sandworms are shown to be undergoing

recovery as shown in figure 1. Initially, their weight has

increased and decreased significantly under different

salinities, which means that at that point of time, there

are not yet regulating their body osmolarity. This in turn,

fashion that their body’s salinity is the same as the

environment’s salinity and might not be suitable for them.

However, since sandworms are tolerant to different

19

salinities, they do not get much affected even though they

experience a weight change (change in body’s salinity) and

it is shown in figure 1 that they are returning back to

normal weight change as time progresses.

At the 4th hour, both species had P values smaller than

0.05 in all three salinities, therefore meaning that it is

statistically significant and did not occur by chance.

However, at the 8th hour for both species, the P values were

larger than 0.05. Nonetheless, this does not mean that it is

not statistically significant, for the data is reliable and

did not happen by chance, there is just lack of strong

evidence. Furthermore, at the 24th hour, the P values for

the sandworms were much smaller than the P values of the

bloodworms. (At 20ppt 24 hour, the sandworm had P value of

0.002 whereas the bloodworm had a high 0.513). There is a

huge variance in the p values.

For both species, the rate of inflow during the first

four hours for both 20 and 30 ppt were more than the

outflow, as there was an increase in weight (positive

change). For 40 ppt during the first four hours, the rate of

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outflow was more than the rate of inflow, as a decrease of

weight is shown (negative change). The sandworm, in the 8th

hour, experienced 38.1% in weight change, which means that

the rate of inflow is still more than the rate of outflow.

However, it is smaller in comparison with the 4th hour,

which had a bigger rate of inflow that caused 40.9% change

in body weight. In 40 ppt, the sandworm’s rate of outflow

was greater than the rate of inflow throughout the time

period as the change is continuously negative. Nevertheless,

the rate of outflow in 40 ppt sandworm is becoming lesser as

the time progresses. For the bloodworms, the rate of inflow

at 20 and 30 ppt were greater than the outflow. At 40 ppt

however, the rate of outflow was greater.

The negative values in 40 ppt for both species suggests

that the osmolarity of both estuarine worms were less than

40 ppt, because they are losing weight to their environment,

which can only occur through osmosis from a lower

concentration to a higher concentration. It means that their

osmolarity is somewhere between 30-40ppt. A reasonable

assumption would be 35 ppt, which is normal seawater

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salinity. Therefore, the difference in the direction and

rate of water flow between these salinities depends on the

salinity contained in the worms. If the worm has a higher

concentration than the saline solution, it will gain weight,

meaning that the change will be positive. On the opposite

side, if the worm has a lower concentration than the saline

solution, it will lose weight, as water will go out to the

aquarium due to the osmotic gradient; thus it will cause

negative values in change. Bloodworms would be found mostly

near the ocean, as the salinity would be 35 ppt. Sandworms

would be found in both near ocean sites (where salinity is

quite high), and in other places (nearer to freshwater) as

well (where salinity is lower).

As to improve the accuracy of the experiment, we have

to make sure that most of the extra surface water from the

worms are removed prior to weight measurement. During the

experiment, some worms were dried more thoroughly than

others; some worms were just given a light pat.

Furthermore, the time at which the weights are recorded

could be extended to 48 hours instead of 24. This would

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allow greater visibility in data trends and validate the

hypothesis to a greater extent. More worms could also be

taken as to provide a wider range from which averages can be

taken and will reduce sampling error. Weight (in grams)

should not be rounded off, and taken as they are shown on

the scale as to improve accuracy. Each worm could be weighed

several times; as to make sure the readings are consistent.

Devoting all our attention towards the experiment can also

reduce human errors and making sure that every step taken is

necessary and done correctly.

The sandworms that my group recorded were from the 40

ppt (high salinity) aquarium and were observed to be

generally active. None of the worms were observed to be

inactive, and there were no mortalities. This may be because

sandworms are osmoregulators and do not get bothered by the

change in salinity. However, bloodworms may be less active

in 40 ppt conditions because they are osmoconformers and are

not suitable to live in that salinity (although most

tolerate it, they could potentially start to die out if they

were exposed for more than 24 hours).

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Urination is not only a process of removing metabolic

waste, it is also a technique used for osmoregulation. The

worm’s parapods move in rhythm and draws fluid inside the

tubular system, which enters the nephridia. These tubular

structures reabsorb essential substrates such as amino

acids, and removes excess water, metabolic waste and ions.

This process allows the worms to osmoregulate themselves.

In conclusion, both the estuarine worms were able to

tolerate the different salinities, even though there were

mortalities. The bloodworm has less tolerance and hence had

more deaths; opposite goes for the sandworm. I learnt that

although the worms co-exist alongside each other in the same

environment, they are completely different in the sense that

one is a euryhaline and another is stenohaline. Each species

adjusted to the different salinities, and some died because

they couldn’t adjust to the new saline environment. The

bloodworm, although used to living in 35ppt, could well

adjust to 30ppt condition. However, when it is pushed too

far from the comfort zone (say, 40 ppt), then the worms

start to die out. This shows that osmoconformers are able to

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adjust to slight changes in environment, but if pushed too

extensively, they will not be able to adjust. It applies to

the sandworm, if they were placed in a saline solution that

is much too high or low in concentration, they might be

shocked and die out before self-regulation kicks in.

To further this investigation, an experiment should be

done with different and more extreme salinities (ranging

from 0-70ppt). More estuarine animals (other than worms)

should also be experimented on, such as fishes or crabs as

to further the research and see its application and effects

on different types of organisms. Overall, the experiment was

successful and yielded the results that were laid out in the

hypothesis.

Table and Figures:

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Figure 1. Shows the sand worm’s change in weight over time (0

hour, 4 hour, 8 hour and 24 hour). Y-axis shows the change in

weight, and X-axis shows the time in hours. Measurements were

taken at 20ppt, 30ppt and 40ppt. The graph shows the weight is

nearing normal weight.

26

0 5 10 15 20 25 30

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Sand Worm's change in weight with respect to time

20 PPT30 PPT40 PPT

Time (hours) cha

nge

in w

eigh

t

Figure 2. Shows the bloodworm’s change in weight over time (0 hour, 4 hour, 8 hour and 24 hour). Y-axis shows the change in weight, and X-axis shows the time in hours. Measurements were taken at 20ppt, 30ppt and 40ppt.

27

0 5 10 15 20 25 30

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

Bloodworms

20 PPT30 PPT40 PPT

Time (hours)

change in weight

Figure 3 shows the mortality of bloodworms after being exposed to the three different salinities. Mortalities are recorded from 0 hour, 4 hour, 8 hour and finally 24 hour. The x-axis shows the time in hours, and the Y-axis shows thenumber of worms that have died.

28

0 4 8 240

0.51

1.52

2.53

3.54

4.5

Mortality of Bloodworm

20 ppt30 ppt40 ppt

Time (hours)

Worm Deaths

Figure 4 shows the mortality of bloodworms after being exposed to the three different salinities. Mortalities are recorded from 0 hour, 4 hour, 8 hour and finally 24 hour. The x-axis shows the time in hours, and the Y-axis shows thenumber of worms that have died.

29

0 4 8 240

0.5

1

1.5

2

2.5

Mortality of Sandworm

20 ppt30 ppt40 ppt

Time (hours)

Worm Deaths

Figure 5 shows a bloodworm with its transparent skin that allows its red color to be exposed to our naked eye. It hasparapods, four jaws jaws and over 300 segments.

Figure 6 shows a sandworm with its greenish brown skin colorand its much more developed parapods that enables it to limpfaster. It has two jaws and over 200 segments.

Literature cited:

Manual:

30

Laboratory Manual. Science of living systems 22. Human influences on life in the Sea. 2011, Harvard University, Cambridge, MA.

Text:

Wilson, W.H, Jr, and R.E Ruff. 1988. Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic)—sandworm and bloodworm. U.S Fish. Wildlife. Serv.Biol. Rep. 82(11.80) U.S Army Corps of Engineers, TR EL-82-4. 23 pp.

Internet:

Kenneth S. Saladin. Osmoregulation. Retrieved from http://www.biologyreference.com/Oc-Ph/Osmoregulation.html

Restore America’s estuaries (est. 1995) what is an Estuary. Retrieved from http://www.estuaries.org/what-is-an-estuary.html

United States Environmental Protection Agency (EPA, est. Dec1970) what is an estuary. Retrieved from http://www.epa.gov/owow_keep/estuaries/kids/about/what.htm and http://water.epa.gov/type/oceb/nep/about.cfm

Laney P. Austin. May 2011. Nereis Virens. Retrieved from http://wiki.hicksvilleschools.org/groups/hsbiology/wiki/ebe67/Nereis_virens.html

Pictures:

Figure 5 (bloodworm) retrieved from http://zottoli.files.wordpress.com/2011/01/glycera-dibranchiata-coiled-worm-orrs-island-bridge-mud-flat-october-5-2006-054.jpg?w=576&h=499

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Figure 6 (sandworm) retrieved from http://www.dkimages.com/discover/Projects/AA605/previews/50490967.JPG

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