Unformatted text preview: Name: Abhilash Mangamuri Block: 1 Worksheet 1: Questions for Chesapeake Bay Food Web Before Large-scale
Fishing. PLEASE PUT ALL ANSWERS IN A DIFFERET COLOR FONT!! 1. Examine the food web before humans lived in the Chesapeake. Notice
which species groups are abundant (dark circles) and which species groups
are rare (light circles). Color or check the squares on the chart below to
indicate which species groups were rare or abundant. 2. Are most species abundant or rare? Which species groups are rare?
Most are abundant. The ones that are rare are jellyfish, worms, floating algae, microbes, and detritus. 3. How is it possible that the worms/amphipods are considered part of two
groups? In which group are they more appropriately placed? Hint: Worms and
amphipods cause rot on the plants that they eat.
The worms and amphipods eat detritus and seafloor plants. 4. What is group F? What is the role of detritus in the food web?
Detritus. They provide nutrients to the base of the food web. 5. List the number of strong and weak interactions for each of the species
groups listed at the top of this chart. Count the number of strong and weak
connections (arrows going to or from a species group) to complete the chart
Connection Sea Floor Plants Predatory Fish Grazing Fish Floating Algae Strong: Strong: Strong: 6 Strong: 2 Weak: Strong: 1
Weak: 1 Weak: Weak: Total: Total: 2 Total: 7 Weak: 7
0 1 0 Total: Total:
6. The producers can be organized based on where they are found in the water.
Some float and some grow from the seabed. Which producers float and which
producers grow from the sea bottom?
Floating algae float and seafloor algae, grasses, and plants.
7. In this ecosystem, which type of producers are more abundant, the producers
that float or the producers that grow from the sea bottom?
The ones that grow on the sea floor
8. If whales and turtles become rare in this ecosystem what would you expect to happen to the number of jellyfish?
The jellyfish population would probably increase.
9. If whales, sharks, seals and alligators were removed from the ecosystem what
would you expect to happen to the numbers of predatory fish?
Their population would increase. Worksheet 2: Questions for Chesapeake Bay Food Web After LargeScale Fishing (USE FOOD WEB FOR AFTER FISHING) 1. Now examine the food web after humans became part of the Chesapeake Bay
ecosystem through fishing. Complete the same chart that you completed for the
previous food web, and color or check which species groups are now rare or
abundant. If a species group has gone extinct, then cross out both boxes with
an X. 2. Which organisms went locally extinct?
Alligators and manatees.
3. Are more organisms rare or abundant after large-scale fishing? Which
organisms are abundant?
Most organisms are rare. The abundant organisms are birds, jellyfish,
worms/amphipods, floating algae, and microbes.
4. Are these the same organisms that were abundant in the pre-human food
No. Most of them rare back then. The birds were abundant.
5. What happened to the top predators? Were they more or less affected than
other trophic groups?
All the top predators were affected more than the trophic groups. 6. List how many species groups depend on each of the species groups listed at
the top of this table. Count the number of strong and weak connections (arrows
going to or from a species group) to complete the table below:
Connection Sea Floor Plants Predatory Fish Grazing Fish Floating Algae Strong: Strong: 0 Strong: 1 Weak: Weak: 3
Total: 3 Strong: 1
Weak: 7 Strong: 1
Weak: 1 Total:
7. Total: 8 Weak: 7
Total: 8 Total: 2 In general, do these species groups have more connections or less after fishing?
They have around the same number of connections. 8. How does the strength of the interactions compare between this food web
and the one before fishing?
Many of the interactions are weaker now.
9. What does it mean for the ecosystem when most of the interactions are weak?
If means that the complexity of the ecosystem has been reduced. There is a lot less going on now.
10. How is this food web similar/different to the food web without people?
Many of the same organisms are still there and birds are common in both food webs. Some organisms
are now locally extinct. Many common organisms then are now rare. Jellyfish are now abundant.
12. Why are there fewer predatory fish if there are fewer whales, sharks, seals
People may be overfishing and eating them as well. 13. Which producers are now more common in this ecosystem, the floating
algae or the sea floor algae and plants and seagrass?
Floating algae 14. From what you know about the relationship between high levels of nutrients
and algae growth, why have the floating algae increased?
Fertilizer in run off from the land could have caused an increase in algae that live on the surface. 15. What happened to the sea floor algae and plants? If fewer organisms are eating them, shouldn’t their numbers have increased? Why are they rare now?
Hint: Like all plants, what do the sea floor algae and plants need to grow? How
do more floating algae limit this important resource that sea floor algae and
plants need? Explain.
Thick layers of floating algae blocked the sunlight from reaching the sea floor algae and without
sunlight, the seafloor algae cannot grow and dies.
16. How does this food web connect to the present-day problem of high nutrient
levels in the water? (Hint: Oysters filter the nutrients, microbes and floating algae
from the water.) Use the food web to explain what happened to their numbers and
People started overfishing oysters, which led to decreased oyster population. Without the oysters
as filters, there is now excess nutrients in the water.
17. Based on your answer to question seventeen make a hypothesis for how
catching oysters affects floating algae levels?
If people catch and eat too many oysters, then there will be an increase of floating algae. Worksheet 3: Oyster Catch vs Nutrient Levels in the Chesapeake Bay
Testing the hypothesis that oysters maintain healthy plankton levels in the Bay
USE THE GRAPH TO ANSWER THESE QUESTIONS: 1. What was the ratio of floating algae to sea floor algae in 1700? _ 1 2. How does it compare to the ratio today?
There are more floating algae than sea floor algae today. And the algae ratio is higher than the
oyster catch. The excess wast from the runoff of the fertilizer used enabled the floating algae to
3. What does the increase in floating algae indicate about today’s level of
nutrient pollution as opposed to the nutrient levels 300 years ago?
The nutrient levels are higher now than back then. 4. Why do you think the ratio of floating algae to sea floor algae levels in the
Bay began to increase around 1750? (Hint: In the 1700s Europeans settlers
began to establish farms in the Chesapeake region).
The farms' fertilizer would have contributed to the run off and excess nutrients. 5. Did the increase in the ratio of floating algae to sea floor algae in 1750 have
anything to do with the oyster catch? Why or why not?
No. This is because people did not catch many oysters back then. _
6. The ratio of floating algae to sea floor algae held steady for a very long time
at around three and then suddenly increased towards eight starting after 1950.
Use your graph to determine what happened to the oyster catch over the same
More oysters were being harvested from the bay and the oyster population started falling.
7. How might the decline of oysters lead to the sudden increase in the ratio of
floating algae to sea floor algae levels? Use what you know about the role of
oysters in the Bay food web to answer this question.
Oysters filtered nutrients, and without them there was excess nutrients.. This led to an increase of
8. How does this graph help us to understand how oysters affect the ratio of
floating algae to sea floor algae?
It shows that as the oysters decreased the algae increased.
9. Why are so few oysters being caught today as compared to the end of the
1800s? _ We could have overfished the oysters so that there are few left. 10. How would you propose to solve the problem of algae overgrowth and also
help the oyster industry?
Stop fishing oysters from the bay and introducing more of them to the bay. Fishing responsibly.
And stopping fertilizer and nutrients from getting into the water. Worksheet 4: Summary
1. How have humans affected the Chesapeake Bay food web? People have over-fished so many different species of fish and wildlife in the bay. We let fertilizer
runoff into the bay and made increased algae blooms. We decimated the oysters and made it even
harder to contol the blooms and nutrients. We made rare jellyfish very common while making common fish very rare. 2. Explain the role that oysters play in keeping the ratio of floating algae to sea
floor algae levels of the Bay healthy.
Oysters filter the excess nutrients from runoff. This makes it so that algae can not overpopulate
because of the nutrients. 3. Use your food webs, charts and data to list at least five consequences of the altered food web of the Chesapeake Bay.
lots of nutrient pollution, lots of jellyfish, less tutles, less oysters, and way too many worm and
4. How can understanding historic ecosystem food webs help us understand
today's ecosystems? ...
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