Benthic-Pelagic Coupling Flashcards
Define an ecosystem.
An energy driven complex of all the organisms in a community and the abiotic factors with which they interact
Define productivity.
The rate at which energy is added to organisms in the form of biomass
What are photoautotrophs?
Photosynthetic organisms such as phytoplankton
What are phytoplankton?
Single-celled free-floating plants
What are heterotrophs?
Primary, secondary or tertiary consumers. NOT producers - cannot gain all of their energy through photosynthesis
Give examples of heterotrophs.
Bacteria, zooplankton, nekton
What are zooplankton?
Single- and multicellular free-floating animals
What are nekton?
Swimming animals
What are the surface waters also called?
Photic zone
What organisms are interacting at the photic zone?
Phytoplankton plus zooplankton and bacteria
Where do nutrients come from that are used by phytoplankton, zooplankton and bacteria at the photic zone?
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
What is net ecosystem production?
NEP provides a measure of the net carbon uptake or release by the ecosystem
What is upwelling?
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.
What is diapause?
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.
What are the advantages of diapause?
- 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
What forms on the sea bed as a result of diapause?
Egg banks
What can diapause indirectly aid?
Bacterial remineralisation in sediment as organic matter is deposited on the sea bed
What happens in anaerobic bacterial remineralisation in sediment of the benthos?
No oxygen - bacteria utilizes other electron acceptors such as nitrate, nitrite, iron oxides etc. for respiration
Why is physical action needed for bacterial remineralisation in sediment to occur aerobically?
Oxygen must be diffused into the underlying sediment of the benthos to ensure that bacteria have the oxygen necessary to carry out aerobic respiration
What is the process of aerobic bacterial remineralisation in sediment?
Bacteria respire aerobically in the presence of oxygen, breaking down organic matter into energy which can be used
What helps to speed up the process of bacterial remineralisation in sediment?
Suspension feeders
Describe in basic steps the process of organic material in the cycle of benthic-pelagic coupling.
- Organisms die and decay
- Organic material sinks to benthic zone
- Organic material is transformed to inorganic
- Resuspension of inorganic material
- Resource for pelagic organisms
What is the subtidal pump?
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
Explain the role of bioturbation in facilitating aerobic nutrient remineralisation in the sediment?
Burrowing of animals in the sea bed introduces oxygen and organic matter into the sediment.
How is biological mixing from the benthos to pelagic areas aided by suspension feeders?
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.
What are physical upwellings?
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.
What can physical upwellings be driven by?
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.
What are emergent zooplankton?
Zooplankton which reside in the benthic substrate until larval or juvenile stages, when they emerge and transition to a pelagic environment.
What triggers the emergence of zooplankton from benthic substrate?
Physical factors such as photoperiod (the period of time that light is available within 24 hours) and temperature
What is the role of emergent zooplankton in benthic-pelagic mixing?
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.
How are tides caused?
By the gravitational pull of the sun and the moon, although the effect of the moon is greater.
When are there higher high tides and lower low tides? What is this called?
When the sun and the moon are aligned. Spring tides.
When are the tides smaller? What is this called?
When the sun and the moon are not aligned. Neap tides.
What is the supralittoral zone also called?
The ‘splash zone’
What are the features of the supralittoral zone?
Extremely exposed to salt spray.
Conditions are extremely variable.
Dominated by lichens and rarely submerged.
What are the features of the littoral fringe?
Very exposed with very variable conditions.
Low diversity - dominated by channelled wrack and small periwinkles.
Submerged for short periods but exposed for long periods.
What are the features of the eulittoral zone?
Dominated by fucoids, barnacles, molluscs and gastropods.
Species depends on exposure
Submerged and exposed every tide
What are the features of the subtidal zone?
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
What is the order of coastal zones, from land to submerged underwater.
- Supralittoral zone (never submerged)
- Littoral fringe (rarely submerged)
- Eulittoral zone (submerged with tides)
- Subtidal zone (submerged most of the time apart from low spring tides)
