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MAR 333 - Unit 2 > Unit 2 - Coastal Physics and Ecosystems > Flashcards

Unit 2 - Coastal Physics and Ecosystems Flashcards

1
Q

How do nutrient concentrations in river water compare to open-ocean water?

A

nutrient concentrations naturally higher in river water

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2
Q

What human activities in the watersheds elevate nutrient concentrations in estuaries?

A

agriculture and fertilizer runoff.

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3
Q

What are some local inputs that elevate nutrient concentrations in estuaries?

A

Human waste discharge and street runoff.

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4
Q

How does primary production in estuaries respond to nutrient loads?

A

Generally positive trend

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5
Q

What are the characteristics of bioavailable nitrogen in pristine river waters?

A

Pristine river waters generally have low levels of bioavailable N (NO3 and NH4)

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6
Q

How does salt marshes affect the bioavailable nitrogen in estuarine waters?

A

Bioavailable N is stripped from river water as it passes over salt marshes

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7
Q

Why can rainfall be a significant contributor to estuarine waters?

A

N-filtering by salt marshes is very efficient

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8
Q

Where does most of the bioavailable nitrogen in estuaries come from?

A

not new, but recycled from mineralization of OM within estuarine water column and sediments

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9
Q

Why may cessation of excess nutrient input not have an immediate effect in estuaries?

A

because of sediment storage of N and P, making bottom sediments a long-term source of N and P

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10
Q

How do increases in nutrients in the Mississippi River affect the Gulf of Mexico?

A

Enhanced nutrient transport to the Gulf of Mexico

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11
Q

What does excess nutrients in coastal areas promote?

A

Excessive primary productivity

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12
Q

Where do big rivers discharge most of their sediment?

A

Open continental shelf or the upper slope

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13
Q

What happens to sediment in smaller rivers with significant estuaries?

A

Trapped in the estuaries due to slow water flow

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14
Q

Why is sediment reactions in estuaries different from water column reactions?

A

Due to low redox conditions in the sediments

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15
Q

What is a Salt Marsh?

A

A relatively flat intertidal area along the margin of an estuary where fine-grained sediment is deposited and salt-tolerant grasses grow

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16
Q

What is the channelization in a salt marsh dependent on?

A

tidal range (more tide -> more channels)

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17
Q

What leads to large amounts of import and export with tidal creeks in salt marshes?

A

Tide-induced flushing combined with groundwater flow from land

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18
Q

How does tidal flow affect salinity in salt marshes?

A

Low tide brings low salinity flow due to freshwater runoff; high tide inundates marsh w/ seawater leading to highest observed salinities.

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19
Q

How do salt marsh soils change during the daily tidal cycle?

A

During high tide, soils are inundated leading to anaerobic conditions; during low tide, soils drain, high redox potential re-established in surface sediment.

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20
Q

What factors affect dynamic equilibrium in salt marsh vegetation?

A

Rate of sediment accumulation and rate of sea level rise (or coastal subsidence)

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21
Q

How does sediment accumulation impact salt marsh vegetation?

A

As deposits accumulate, erosion + organic matter oxidation ⬆️, slowing rate of further accumulation

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22
Q

How does sea level rise affect salt marsh vegetation?

A

As sea level rises, the marsh is inundated more frequently, leading to an increased accumulation rate of sediment and peat

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23
Q

What is the consequence when the rate of sedimentation does not keep up with sea-level rise in salt marshes?

A

Marshland is lost

24
Q

How does sea level rise due to global warming impact salt marshes?

A

It could accelerate the loss of marshland

25
Q

What nutrients do salt marshes receive from rivers and groundwater?

A

NO3

26
Q

What do salt marshes convert NO3 into?

A

DON, PON, NH4, and N2

27
Q

Are salt marshes sources or sinks of C, N, and P to estuaries?

A

Sources

28
Q

What is a common limitation in salt marshes?

A

Nitrogen limitation

29
Q

What is the dominant form of nitrogen in most salt marshes?

A

NH4 (Ammonium)

30
Q

What allows for significant rates of denitrification in salt marshes?

A

Flooded, anaerobic sediments

31
Q

How does the contribution of new inputs compare to recycled nitrogen in salt marshes?

A

About equal – different from upland ecosystems where new inputs are much lower (~10%)

32
Q

What organisms may contribute significantly to the nitrogen budgets of salt marshes?

A

Cyanobacteria and soil bacteria through N-fixation

33
Q

What is the range of salinities in which salt marshes can exist?

A

Salt marshes can exist over a wide range of salinities.

34
Q

How does the wide range of salinities in salt marshes affect their biogeochemistry?

A

There will be large variations in the biogeochemistry of different marshes.

35
Q

What is the main reason for the active S cycle in estuarine sediments?

A

High concentration of SO42- in seawater (28 mM)

36
Q

What contributes to the active S cycle in estuarine sediments besides high SO42- concentration?

A

Large inputs of land- and estuary-derived organic matter

37
Q

What does LOICZ stand for?

A

Land-Ocean Interactions in the Coastal Zone

38
Q

What are the characteristics of LOICZ as a modeling method?

A

Minimal data requirements, ability to work with secondary data, widely applicable uniform methodology

39
Q

What is LOICZ informative about?

A

CNP processes and fluxes

40
Q

What assumption does LOICZ budgeting make?

A

all materials are conserved

41
Q

How is the difference between ∑inputs and ∑outputs explained?

A

processes within the system: [∑(sources - sinks) ]

42
Q

What is the outline of the LOICZ budgeting procedure?

A

I. Define physical boundaries of system of interest
II. Calculate water and salt balances to determine physical dynamics
III. Estimate nutrient balances
IV. Derive apparent net biogeochemical processes

43
Q

What are water and salt budgets used for in coastal systems?

A

Estimate water exchange

44
Q

How are system biogeochemical fluxes measured?

A

Departure of nutrient budgets from conservative behavior

45
Q

What is the assumption for nonconservative DIP flux?

A

Proportional to (primary production - respiration)

46
Q

What does the mismatch from ‘Redfield expectations’ for DIP and DIN fluxes depend on?

A

Proportional to (nitrogen fixation - denitrification)

47
Q

What is the formula for calculating net primary production (NPP)?

A

(p-r) = -∆DIP • 106(C:P)

48
Q

What is the formula for calculating nitrogen fixation minus denitrification?

A

(nfix-denit) =∆DINobs -∆DINexp

49
Q

What do derived net processes represent in stoichiometric calculations?

A

apparent net performance of system. Non-biological processes may be responsible for some nutrient uptake/release.

50
Q

What does Net Ecosystem Metabolism represent?

A

Production - Respiration

51
Q

How are the rates of Net Ecosystem Metabolism described?

A

Apparent, based on stoichiometric assumptions

52
Q

What is the typical range of values for Net Ecosystem Metabolism?

A

Most values cluster near 0

53
Q

What values of Net Ecosystem Metabolism are considered questionable?

A

Extreme values beyond ±10

54
Q

As Primary Production increases, respiration tends to exceed production. What does this reflect?

A

Apparently reflects importance of sedimentary organic matter loading

55
Q

What process dominates when values cluster near 0 in (nitrogen fixation-denitrification)?

A

Denitrification

56
Q

What is indicated when apparent N fixation is greater than 5 in (nitrogen fixation-denitrification)?

A

Too high

MAR 333 - Unit 2 (8 decks)

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