Benthic-Pelagic Coupling

Question 1

Define an ecosystem.

Answer 1

An energy driven complex of all the organisms in a community and the abiotic factors with which they interact

Question 2

Define productivity.

Answer 2

The rate at which energy is added to organisms in the form of biomass

Question 3

What are photoautotrophs?

Answer 3

Photosynthetic organisms such as phytoplankton

Question 4

What are phytoplankton?

Answer 4

Single-celled free-floating plants

Question 5

What are heterotrophs?

Answer 5

Primary, secondary or tertiary consumers. NOT producers - cannot gain all of their energy through photosynthesis

Question 6

Give examples of heterotrophs.

Answer 6

Bacteria, zooplankton, nekton

Question 7

What are zooplankton?

Answer 7

Single- and multicellular free-floating animals

Question 8

What are nekton?

Answer 8

Swimming animals

Question 9

What are the surface waters also called?

Answer 9

Photic zone

Question 10

What organisms are interacting at the photic zone?

Answer 10

Phytoplankton plus zooplankton and bacteria

Question 11

Where do nutrients come from that are used by phytoplankton, zooplankton and bacteria at the photic zone?

Answer 11

Upwelling and mixing (turbulence brings transport from deeper in the ocean to the surface)
Feedback loops - Changes in phytoplankton populations will change those of herbivores, in turn affecting nutrient recycling through heterotrophic respiration

Question 12

What is net ecosystem production?

Answer 12

NEP provides a measure of the net carbon uptake or release by the ecosystem

Question 13

What is upwelling?

Answer 13

Upwelling events bring nutrient-rich waters from the ocean’s deeper layers to the surface, where they can fuel primary productivity in the photic zone. Upwelling occurs when winds blow surface waters away from the coast, causing deeper, nutrient-rich waters to rise and replace them.

Question 14

What is diapause?

Answer 14

A period of dormancy in juvenile development. During diapause, metabolic activity decreases, and growth and reproduction are temporarily halted until conditions become more favourable for survival and development.

Question 15

What are the advantages of diapause?

Answer 15

• Minimize energy expenditure in low food availability, allowing survival when it would otherwise not be possible
• Makes organisms less conspicuous, lowering predation
• Increases dispersal ability as organisms remain dormant during transport to new locations via wind, water currents or animal vectors

Question 16

What forms on the sea bed as a result of diapause?

Answer 16

Egg banks

Question 17

What can diapause indirectly aid?

Answer 17

Bacterial remineralisation in sediment as organic matter is deposited on the sea bed

Question 18

What happens in anaerobic bacterial remineralisation in sediment of the benthos?

Answer 18

No oxygen - bacteria utilizes other electron acceptors such as nitrate, nitrite, iron oxides etc. for respiration

Question 19

Why is physical action needed for bacterial remineralisation in sediment to occur aerobically?

Answer 19

Oxygen must be diffused into the underlying sediment of the benthos to ensure that bacteria have the oxygen necessary to carry out aerobic respiration

Question 20

What is the process of aerobic bacterial remineralisation in sediment?

Answer 20

Bacteria respire aerobically in the presence of oxygen, breaking down organic matter into energy which can be used

Question 21

What helps to speed up the process of bacterial remineralisation in sediment?

Answer 21

Suspension feeders

Question 22

Describe in basic steps the process of organic material in the cycle of benthic-pelagic coupling.

Answer 22

1. Organisms die and decay
2. Organic material sinks to benthic zone
3. Organic material is transformed to inorganic
4. Resuspension of inorganic material
5. Resource for pelagic organisms

Question 23

What is the subtidal pump?

Answer 23

Water, nutrients and organic matter are circulated within benthic sediments by wave action and tidal currents. Oxygen-rich water enters the sediment interstitially, allowing aerobic nutrient remineralisation

Question 24

Explain the role of bioturbation in facilitating aerobic nutrient remineralisation in the sediment?

Answer 24

Burrowing of animals in the sea bed introduces oxygen and organic matter into the sediment.

Question 25

How is biological mixing from the benthos to pelagic areas aided by suspension feeders?

Answer 25

Suspension feeders - bivalves and polychaetes are filter feeders. The filtering of organic matter creates localised water currents, contributing to mixing of water. This allows resuspension of sediment and nutrients back up into the water.

Question 26

What are physical upwellings?

Answer 26

Physical upwellings are oceanographic phenomena characterized by the upward movement of cold, nutrient-rich water from the deeper layers of the ocean to the surface.

Question 27

What can physical upwellings be driven by?

Answer 27

Ekman transport - surface waters move away from the coast. This leads to a deficit of surface water, replaced by deeper waters. Thus, upwellings often occur along land margins.

Question 28

What are emergent zooplankton?

Answer 28

Zooplankton which reside in the benthic substrate until larval or juvenile stages, when they emerge and transition to a pelagic environment.

Question 29

What triggers the emergence of zooplankton from benthic substrate?

Answer 29

Physical factors such as photoperiod (the period of time that light is available within 24 hours) and temperature

Question 30

What is the role of emergent zooplankton in benthic-pelagic mixing?

Answer 30

When zooplankton emerge as larvae or juveniles, they disrupt the sediment of the benthos and may carry organic materials. Zooplankton within the water column can then feed on other organisms such as phytoplankton, contributing to remineralization and nutrient release. Additionally, zooplankton may become prey for other nekton, creating a feedback loop of nutrient cycling.

Question 31

How are tides caused?

Answer 31

By the gravitational pull of the sun and the moon, although the effect of the moon is greater.

Question 32

When are there higher high tides and lower low tides? What is this called?

Answer 32

When the sun and the moon are aligned. Spring tides.

Question 33

When are the tides smaller? What is this called?

Answer 33

When the sun and the moon are not aligned. Neap tides.

Question 34

What is the supralittoral zone also called?

Answer 34

The ‘splash zone’

Question 35

What are the features of the supralittoral zone?

Answer 35

Extremely exposed to salt spray.
Conditions are extremely variable.
Dominated by lichens and rarely submerged.

Question 36

What are the features of the littoral fringe?

Answer 36

Very exposed with very variable conditions.
Low diversity - dominated by channelled wrack and small periwinkles.
Submerged for short periods but exposed for long periods.

Question 37

What are the features of the eulittoral zone?

Answer 37

Dominated by fucoids, barnacles, molluscs and gastropods.
Species depends on exposure
Submerged and exposed every tide

Question 38

What are the features of the subtidal zone?

Answer 38

Less exposed, conditions relatively stable.
High diversity of specially adapted marine species
Dominated by kelps, red algae, sea squirts and sponges
Submerged most of the time, only exposed on low spring tides

Question 39

What is the order of coastal zones, from land to submerged underwater.

Answer 39

1. Supralittoral zone (never submerged)
2. Littoral fringe (rarely submerged)
3. Eulittoral zone (submerged with tides)
4. Subtidal zone (submerged most of the time apart from low spring tides)