Module 10

Question 1

What is an estuary?

Answer 1

A semi-enclosed body of water where freshwater and seawater meet and mix

Question 2

What are euryhaline species?

Answer 2

Species that can tolerate a wide range of salinities

Question 3

What are stenohaline species?

Answer 3

Species that can tolerate a narrow range of salinities

Question 4

What does brackish refer to?

Answer 4

Water that is less salty than seawater but saltier than freshwater

Question 5

What are wetlands?

Answer 5

Estuarine areas of high elevations that are periodically covered with water

Question 6

What are mudflats?

Answer 6

Wide expanses of an estuary that are exposed during low tide

Question 7

What are meiofauna?

Answer 7

Microscopic organisms living in between marine sediment particles

Question 8

What are channels?

Answer 8

Estuarine areas where water is present both during high and low tide

Question 9

What major geological event caused the formation of most of the world’s estuaries?

Answer 9

The melting of large masses of ice after an ice age

These caused worlwide ocean levels to rise, resulting in the formation of the most common type of estuaries.

Question 10

What are the three pieces of evidence for the existence of at least one ice age in earth’s history?

Answer 10

Glacial deposists, large boulders that were clearly transported to their current location, and geological features such as deep lakes that are best described by the action of glaciers.

All of these occur in areas that are temperate today, but they give evidence that at one time these areas were covered by glaciers.

Question 11

What are the main differences betwen the uniformitarian view and the catastrophist view when it comes to the ice age?

Answer 11

The uniformitarian thinks that several ice ages occured throughout earth’s history and that they all came and ended rather slowly. The catastrophist thinks that there was only one ice age, and it came about very quickly.

Question 12

What conditions are necessary to form a glacier?

Answer 12

Wet winters that are not too cold and cooler summers that do not allow for a lot of snow to melt

(also can be described with warmer oceans or extra snowfall)

Question 13

What is the most common type of estuary?

Answer 13

Drowned river valleys

Question 14

Of the five types of estuaries, which has water most similar to costal waters that are not a part of estuaries?

Answer 14

Fjords

Question 15

Name the three abiotic factors of a shallow estuary and their causes.

Answer 15

1. Fluctuating salinity: caused by evaporation and the mixing of fresh and saltwater
2. Higher temperature: caused by shallow waters
3. Murky water: caused by suspended sediments

Question 16

A sessile organism is living at a given point on the substrate of an estuary. At which tide (high or low) does the organism experience the highest salinity?

Answer 16

High tide

This is because high tide brings in an increase of seawater

Question 17

In an estuary, a stenohaline saltwater organism can survive further inland along one side of the river of the river than on the other. Why?

Answer 17

Gyres

The gyres in the ocean bend the outflow of a river in one direction.

Question 18

You are floating on the ocean and look back to the coast.

If a stenohsline organism can live further inland on the left side of the river, is this estuary in the Northern or Southern Hemisphere?

Answer 18

Northen Hemisphere

Because the organism requires high salinity we can conclude that the saltier side is the left. When the saltier side is the left side of the river it is in the Northen Hemisphere.

Question 19

In general, is the substrate of an estuary sandy or muddy?

Answer 19

Muddy

Finer sediments get deposited in estuaries because that is what is commonly carried in the rivers they border.

Question 20

An organism is able to live in all areas of an estuary. Is it a euryhaline, stenohaline, or brackish-water species?

Answer 20

Euryhaline

Euryhaline species can tolerate a wide range of salinities within an estuary

Question 21

Which kinds of organisms are most prevalent in an estuary: osmoconformers or osmoregulators?

Answer 21

Osmoregulators

Osmoregulators are able to regulate their own internal solute concentration making them less affected by drastic salinity changes.

Question 22

If an organism cannot tolerate strong changes in salinity, how can it manage to stay in a single location near the middle of an estuary over a long period of time?

Answer 22

Reduce exposure to water

Bivalves and other species can achieve this by burrowing in the sand. Bivalves specifically are able to shut down during salinity changes.

Question 23

Suppose you are looking for a center of an estuary, but you do not have a map. What type of species (euryhaline, stenohaline, or brackish-water species) would you look for to indicate the center of an estuary?

Answer 23

Brackish-water species

Brackish water is a mixture of fresh and saltwater and would be able to signify where the salt and freshwater meet.

Question 24

A scientist is studying a wetland in a temperate area of the world.

Is it most likely a salt marsh or a mangrove forest?

Answer 24

Salt marsh

Question 25

Name three types of mangroves.

Answer 25

Red, black, and white mangroves

Question 26

What is a special feature of red mangroves?

Answer 26

Prop roots that prop up the tree above water; tolerant of high salinities

Question 27

What is a special feature of black mangroves?

Answer 27

Pneumatophores that grow out of the soil for more oxygen exposure; less tolerant of high salinity than the red mangrove

Question 28

What is a special feature of the white mangrove?

Answer 28

Two salt glands at the base of the leaves that excrete excess salts; least tolerant of high salinities

Question 29

# You are traveling through a mangrove forest. If you start at low elevations and travel so that your elevation increases, what is the order in which you will encounter the three types of mangrove trees?

Answer 29

1. Red mangroves 2. Black mangroves 3. White mangroves ## Footnote The lower the elevation the higher the salinity.

Question 30

What is the major kind of grass in a salt marsh?

Answer 30

Cordgrass

Question 31

# Mudflats can support few plants# that somewhat help primarily produce What are the *major* primary producers here? | #flowering plants, eelgrass, turtlegrass, etc.

Answer 31

Diatoms, photosynthesizing plankton, and bacteria

Question 32

# When looking at a estuarine mudflat, there seems to be little life. Is this so? Why or why not?

Answer 32

There is plenty of life in an estuarine mudflat. The major primary producers are microscopic (diatoms and bacteria), and most of the other organisms living there are buried in the muddy sediment.

Question 33

Why are deposit feeders more common than filter feeders in mudflats?

Answer 33

Suspended sediments in the water clog the filtering organs of filter feeders, but there are plenty of deposits on the surface of the mud for deposit feeders.

Question 34

Are mudflat predators more prevalent at high tide, low tide, or equally in both?

Answer 34

Equally in both ## Footnote At high tide the predators are fish and at low tide the predators are birds and land animals.

Question 35

# Some large mudflats up to 11,000 shorebirds can move at one time to feed Why is the population of infauna living there not decimated?

Answer 35

The large populations of infauna combined with the varying depths at which they are buried keep the birds (with varying bill lengths depending on species) from overfeeding.

Question 36

Compared to other ecosystems, do estuaries have a large numb er of species? Do they have a relatively large number of organisms?

Answer 36

Estuaries do not have a large number of species, but they do have a large number of organisms living there.

Question 37

In an estuary, where are you likely to find juvenile fish? Why?

Answer 37

You tend to find them in the channels, because that's the portion always covered by water, the food is plentiful, and there is good protection from predators there. ## Footnote You could also say within the shelter of red mangrove roots in tropical estuaries.