Benthos: Reflective Questions Your essay answer should be clear and succinct, amounting to perhaps 3-5 sentences totaling 50 to 80 words; longer essays are

Benthos: Reflective Questions Your essay answer should be clear and succinct, amounting to perhaps 3-5 sentences totaling 50 to 80 words; longer essays are strongly discouraged. It is recommended that you prepare your answer in a separate document from which you copy it into Canvas.

Question 1 5 pts

Explain why both rocky and sandy shores can be divided into different zones based on the variations in the organisms that dwell in these habitats and describe examples of distinct adaptations of biota within each of the environments that aid their survive in that setting.

A strong answer will describe the natural variations within both rocky and sandy shores and how organisms adapt to these conditions, including specific characteristics that distinguish the communities of organisms found in these distinct environments, citing examples.

Question 2: 1 pts

Clams are filter feeders that burrow into soft sediment, and this lifestyle places them in which of the following categories of benthic organisms?

Infauna
Epifauna
Epiflora
inflora
Exfauna

Question 3 :1 pts

Many environmental factors influence how the planktonic larvae of benthic organisms select sites for settling, but which of the following factors is the principal agent in their dispersal?

Ocean temperature
Ocean currents
Chemical released by adult benthos
Ocean salinity
Intensity of sunlight

Question 4 : 2 points

The ecosystems on Shemya Island and Amchikita Island differ in their abundance of kelp which is coupled to the populations of sea urchins and sea otters. Match the differences in kelp populations to the abundance of the organisms in the ecosystems that they sustain.

Thin kelp- 1. scarce sea urchins and abundant sea otters, or 2. scarce sea urchins and scarce sea otters, or 3. Abundant sea urchins and abundant sea otters, or 4. abundant sea urchins and scarce sea otters.

Abundant kelp- 1. scarce sea urchins and abundant sea otters, or 2. scarce sea urchins and scarce sea otters, or 3. Abundant sea urchins and abundant sea otters, or 4. abundant sea urchins and scarce sea otters.

Question 5 :1 pts

Which description best describes how oyster beds grow over time?

Vertically, as oyster spat settle on adults
Laterally, as oyster spat settle beside existing oyster beds
Independently, oyster spat settle away from exisiting beds
Randomly, as oyster spat can settle anywhere
Variably, dependent on changes in tidal ranges Oceans & Global Environment
Module 12: Marine Ecology
Rocky
shores
•Benthic Organisms
• Classification of Benthos – infauna,
epifauna & epiflora.
• Adaptation to rocky & sandy shores:
attachment to rocks & zonations based
on ability to withstand desiccation.
What are Key Concepts?
•Benthic Habitats & Lifestyles
• Classification based on habitat
• Di?erent adaptations to rocky & sandy
shores – attachment & burrowing – both
zoned according to water levels.
Sandy
shores
G131 Oceans & Global Environment
Benthic Organisms
Epiflora, Epifauna & Infauna
•Epiflora & epiflauna: surface plants & animals.
• Attached: filtering seawater; mobile: predation, .
•Infauna: buried animals, deposit or filter feeders.
• Attached: filtering seawater; mobile: predation, .
Benthic
Organisms
Blue clam
Anenome
Starfish
G131 Oceans &
Global Environment
Benthic Organisms: Zonation
Rocky Shores
•Organisms adapted to tides.
Zonation of organisms
reflecting water availability:
permanently wet to
intermittently wet
Zonation evident
in occurrences of
di?erent
organisms
Range of
tides
associated
with spring/
neap cycle
G131 Oceans & Global Environment
Benthic Organisms: Zonation
Sandy Shores
Polychaete worm
•Organisms adapted to tides.
•Epifauna & infauna, including
burrowing organisms that ingest sediment.
Sand dollar
G131 Oceans & Global Environment
Eastern seaboard of U.S.
Rocky & Sandy Shores
Zonation association with variations in water level produced by tides
G131 Oceans &
Global Environment
Oceans & Global Environment
Module 12: Marine Ecology
•Benthic Larvae & Oysters,
• Dispersal of benthic organisms by planktonic larvae.
Oyster beds
Vertical
growth
of
oyster
beds.
•
• Dispersal of hydrothermal vent
biota within rift valleys.
Key Concepts
•Benthic Lifestyles
• Benthic invertebrates disperse as
planktonic larvae.
• Oyster spat settle on adults.
• Vent biota dispersed within rifts.
G131 Oceans & Global Environment
Hydrothermal vent biota
Planktonic Larvae of Benthos
Benthic Organisms: Dispersion
•Planktonic larvae respond to environmental
factors influencing Environmental
factors
their selection of
seafloor sites.
Currents aid
dispersal
polychaete
worm
sea urchin
crab
snail
Benthic organisms
with planktonic larvae
G131 Oceans & Global Environment
Successive
generations build
oyster beds – higher &
broader
Oyster Beds
Grow Vertically
•Spat settle on adults.
Oysters
Oyster bed or
reef: vertical
structure
Oyster veliger: final larvae stage
Vertical build-up:
new spat settle on
older oysters
G131 Oceans & Global Environment
Hydrothermal Vent Biota
Dispersal of Vent Biota Larvae
•Achieved by currents flowing
through axial rift valleys of
mid-ocean ridges:
Dispersal of
• Di?erent vent communities.
invertebrates
Yeti crabs
G131 Oceans &
Global Environment
Tube worms
Oceans & Global Environment
Module 12: Marine Ecology
•Kelp Forests
• Benthic brown algae with holdfasts as
anchors & fronds to maintain buoyancy.
• Provide protective habitat for many
di?erent species, notably sea otters.
• Grow as dense communities in nutrientrich waters creating canopy at surface.
Kelp forest
Key Concepts?
•Understanding Kelp Ecosystems
• Photosynthetic brown benthic algae.
• Vital coastal environment for many species
of invertebrates, fish, and mammals.
G131 Oceans & Global Environment
Macro Benthic Algae: Kelp
Create Forest Canopy
Kelp fronds
•Macrocystis: brown algae
• Secured to seafloor by holdfast.
• Can grow to 60m in length.
• Require nutrient-rich water
Kelp
Kelp forest
Kelp forest
G131 Oceans & Global Environment
Sea Otter/Sea Urchin/Kelp
Ecosystem Dynamics
•Controls on kelp
& sea urchins.
Sea urchins
feeding on kelp
Sea otter feeding
on sea urchin
Sea urchin populations & kelp
Kelp
abundant
Kelp
grazed
Sea Otter/Sea Urchin/Kelp Ecosystem
Populations of
di?erent islands
regulate extent
& growth of kelp
G131 Oceans &
Global Environment

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