Exam 2- Aquatic Systems Flashcards
A. List the 5 state factors that control ecosystem processes.
B. Explain what the interactive controls are, and how these differ from the state factors.
C. Explain what feature moderates these controls more in aquatic than terrestrial ecosystems.
A. Time, Climate, Parent Material, Topography, Potential Biota
B. The interactive control happens with in the system and both are control and consoles by ecosystem processes- for instance nutrient availability can impact photosynthetic capacity. This happens in smaller temporal scale than state factors (happens faster).
C. The feature that moderates these controls more in aquatic than terrestrial is the input arrow in aquatic systems is much larger than in terrestrial.
Explain what residence time tells us about an ecosystem & explain how to calculate the residence time of a given element.
- Residence time tells us/ helps us understand an ecosystems openness.
- N, Rt in streams will be longer than in coral reef systems bc the N is being used up by organisms & remaining in the coral reef system for longer than in the headwater streams where a lot of N is being flushed downstream quickly.
RT=Amount in resevoir/rate of (output/ input)
A. Provide three examples of terrestrial-aquatic interactions that are weak.
B. Explain if internal processing is considered to be stronger in aquatic or terrestrial systems & why?
A. Stream->land, lake-> land, ocean-> land
B. Internal processing is stronger in terrestrial systems. Input arrow in aquatic systems is variable but it’s also much bigger which inherently means there is less residence time and less internal processing. In terrestrial systems, a forest for ex., has less exogenous inputs and is constantly recycling a lot of it’s own nutrients, it’s a more closed system - not very leaky, compared to a stream which has a lot of exogenous inputs like leaves which are broken down and then flushed down stream.
Explain what the P/R ratio is and what the values represent. Explain what the ratio tells us about energy flow through an ecosystem that is assumed to be at equilibrium i.e.., not following a disturbance event.
Production/ Respiration.
Aquatic systems have huge exogenous inputs. this changes their equilibrium - equilibrium for headwater streams is net heterotrophic.
P/R= NEP= GPP(P)-ER(R)
IF:
P/R>1= Net Autotrophic (more plants doing photo)
P/R<1= Net Heterotrophic (more respiration)
P/R=1= system is @ equilibrium
Two lakes, one is Oligotrophic and the other Eutrophic, explain why the pH changes differently with depth in the two lakes?
The pH changes differently bc of nutrient availability which increases primary production and therefore respiration increases as well, releasing more CO2 which reduces pH.
Oligotrophic lake- the pH remains generally the same there is not much primary production, therefore no organic carbon falling into the lake floor & affects pH. no microbial breakdown of organic matter
Eutrophic Lake- CO2 increases bc of increased respiration and increased primary production.
Explain how the bicarbonate equilibrium allows aquatic systems to buffer pH. Explain the primary controls on this equilibrium, and a primary way in which human activity is altering this equilibrium
-An abundance of bicarbonate= ions that can break apart acids by taking positive charges, therefore, creating high alkalinity (ability to buffer pH).
H2CO3HCO3- CO3^2-
-Primary control -mineral weathering (slow)
Biotic control- on CO2 are respiration and photosynthesis
-Co2 becomes carbonic acid upon coming in contact with water. Bicarbonate takes hydrogen ions & neutralizes pH. Human activity is altering this by pumping more Co2 into the atmosphere & pushing ocean systems to the edge of the buffering capacity
Explain why Vitousek & Reiner’s model breaks down in a system that gets most of its energy from allochthonous resources.
Make sure to explain how this relates to the system being in equilibrium (inputs=outputs) or not
This model assumes energy is autochthonous (derived from within the system) an example are seed banks which then generate after a disturbance as primary succession forest and quickly reaching the same biomass as mature forest.
Aquatic ecosystems on the other hand rely on exogenous inputs. In headwater streams, for example, outputs & inputs would be similar ( so at equilibrium), with a negative NEP, but this is not the case with the terrestrial model.
The main difference is that terrestrial depends on GPP.
A. Explain the typical gradient of nutrient limitations as one moves from nearshore to offshore in coastal ecosystems.
B. Explain how this gradient can be influenced by parent material.
C. Provide an example of how human impacts may, in turn, weaken or alter this gradient
A. N comes in from the coast, P comes in from upwelling. So more N closer to the cost and more P further and deeper from the coast.
B. Calcium carbonate for example comes from the seafloor off the Florida bay.
C. N inputs from human activity impact P levels in aquatic systems, bc they are coupled. Humans are increasing the amount of N leaching into headwater streams that then filter into oceans bc these nutrients are coupled this excess of N impacts P.
Explain the mechanism by which nutrient enrichment alters: A.) the flow of Carbon through and up the food web and in headwater streams, and B.) ecosystem-level processing of C in headwater streams
A. Nutrient enrichment speeds up the processing of Carbon. Added N makes microbes on leaves more delicious and can lead to bigger insects. ex. the caddisfly that got too big and the predator couldn’t eat it bc it was too big - creating a trophic dead end.
B. Speeds up processing of carbon- shredders are eating leaves that fall into streams much faster and the whole chain is being ramped up through the addition of nutrients.
A. What ratio is the daphnia and the copepod recycling nutrients? ( Daphnia 8:1.5) (copepod 12:1) (Diatom 16:1)
B. How these ratios affect nutrient limitation of the phytoplankton.
A. Daphnia= needs 2 diatoms (32:2)-> recycles (24N: .5P)
Copepod= need 1 diatom (16:1)->recycles (4N: 0P)
B. In both situations (copepods or daphnia) the system would be P limited but with Daphnia a lot more N is being recycled back (24:.5)
How does detritus on terrestrial and aquatic ecosystems differ in terms of quality and why? Explain how this relates to the shape of biomass and production pyramids in terrestrial vs. aquatic systems?
Detritus in aquatic systems is of much higher quality compared to plant detritus in terrestrial systems, bc Terrestrial plants are slower growing and need structural support due to gravity. So they produce more lignin, which is not of high nutrition.
Biomass pyramids, in general, are inverted in aquatic systems related to terrestrial with much of the biomass concentrated at the highest trophic level bc the autotrophs are faster growing and higher quality allowing for higher herbivory.
Production is also higher in aquatic systems.
A. Explain the more contemporary presumed mechanism of how a pant can be nutrient “co-limited” for N and P and how it contrasts to Leibi’s law of the minimum.
B. Explain what the implications of co-limitation are for predicting ecological outcomes.
A. Leibig’s law of the minimum: plant growth is limited by nutrients in lowest abundance. Contrast-> we find that nutrients can’t be measured in isolation from one another (effects are really additive and more often synergistic or antagonistic)
B. co-limitation means we need to be looking at the bigger picture when predicting ecological outcomes, we can just limit P inputs, for example, in water systems bc this will effect the fate & behavior of N within the system.
Explain the mechanism by which cutting off P inputs, but not N, could increase downstream export of nutrient pollutants in freshwater ecosystems.
The presence of P encourages loss of N from aquatic systems into the atmosphere through denitrification. When there is less P within the system, less denitrification happens and more N is transported downstream.
if you reduce the amount of P but not the amount of N, the system can not process bc it is now listed by P so the N just flashes out & goes down stream. Historically there has been tons of processing of N& P and the system also retains and buried a lot of those nutrients. Now if we limit P the process to retain or bury the nutrients isn’t happening.
A. Explain what the Gross Growth Efficiency (GGE) of an organism is.
B. How is GGE expected to differ for terrestrial and for aquatic consumers and why?
C. Explain what this tells us about the extent to which terrestrial and aquatic systems are stoichiometrically constrained.
A. GGE= Proportion of what is ingested needed for growth.
Ingested C for growth = Proportion used.
B.Aquatic consumers have higher GGE bc aquatic heterotrophs are of higher quality, allowing more of proportion eaten to be used for growth.
C. Terrestrial systems are constrained by nitrogen as the trophic level is generally of lower quality. Aquatic systems (stoichiometrically) are more P limited.
