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SOES1006 - Marine Ecology & Evolution > Sandy/Muddy Shores & Estuaries > Flashcards

Sandy/Muddy Shores & Estuaries Flashcards

1
Q

What did Fenberg (lecturer) study when looking into global patterns of the sedimentary environment?

A

How the distribution of rock affected rocky shore species

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2
Q

How did Fenberg (lecturer) study the effect of rock distribution on rocky shore species?

A
  • Used Google Earth
  • Measured the length of each beach or soft-sediment stretch of coastline across the most eastern Pacific coast, from Chile up to N. Washington State, USA (>90° Latitude, spanning 23,000km of coastline)
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3
Q

What did Fenberg (lecturer) find in his study of the effect of rock distribution on rocky shore species?

A
  • In the southern and northern latitudes it is very rocky
  • In mid-latitudes areas around the equator is was sandy and muddy
  • Lot more beaches in the tropics
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4
Q

What are the gaps found in relation to the rock distribution along coastlines and how big are the?

A
  • Northern Peruvian Gap (171km)
  • Columbian Gap (289km) (mostly mangroves)
  • Central American Gap (671km)
  • Northern Gulf of California Gaps (317km combined)
  • Nayarit/Sinaloan Gap (207km)
  • 2 Sinaloan Gaps (701km combined)
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5
Q

Is the coastal rock distribution that Fenberg (lecturer) found in his study a global pattern?

A
  • Has been done globally using satellites
  • Similar findings:
    > On average there is a lot less rock in the tropics
    > Sandy beaches are NOT evenly distributed across the globe
    > Has been known since the 1960s but never made it out of marine geology literature
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6
Q

What possible explanations are there for global coastal rock distribution patterns?

A
  • Tropics: possibly impacted by rainfall, big rivers create large estuaries and beaches, lot more erosion/river influx
  • Polar regions: glaciation & isostatic rebound = more rocky
  • Seems to be related to coastal climate, freshwater inflow and glaciation history
  • Abiotic factors influence biotic factors - beaches create abiotic barriers which inhibits gene flow
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7
Q

What are rocky shores usually inhabited by?

A

Sessile and mobile epifauna

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8
Q

What are soft shores usually inhabited by?

A

Mobile epifauna and infauna - usually burrow down

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9
Q

What is porosity of a shoreline?

A

The volume of pore space between each sediment particle

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10
Q

How does particle size of sediment effect porosity of a shoreline?

A
  • Small particles fill up more space and reduce porosity

- Large particles = more empty spaces and increased porosity

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11
Q

What is permeability of a shoreline?

A

The rate of percolation of water through the sediment

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12
Q

On the shoreline how does porosity effect permeability?

A
  • Low porosity = low permeability

- High porosity = high permeability

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13
Q

What is water content of a shoreline related to?

A
  • Particle size
  • Beach profile
  • Water table height
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14
Q

What are trait of dilatant sands?

A
  • When pressure is applied, the sand becomes dry and hard packed as water is driven out
  • Harder to burrow into = less biodiversity
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15
Q

What are the traits of thixotropic sands (quick-sands)?

A
  • Sands with high clay content become wetter and more easily penetrated when agitated
  • Sand it easier to burrow in to = more biodiversity
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16
Q

What are the traits of muds?

A
  • Do not drain and are saturated with water - very soft

- Easiest to burrow in to = more biodiversity

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17
Q

Oxygen & sediment chemistry: What does aerobic bacteria in sediment do?

A

Decompose organic material at the surface where oxygen is abundant

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18
Q

Oxygen & sediment chemistry: What does oxygen consumption at the surface do?

A

Deprives deeper layers of oxygen, so sediments below the surface are anaerobic

19
Q

Oxygen & sediment chemistry: Why does the depth of the oxygenated layer vary?

A

It varies according to grain size of the shore - which determines its permeability

20
Q

Oxygen & sediment chemistry: What happens as oxygen concentrations diminish with depth?

A

Anaerobic bacteria start to dominate

21
Q

Oxygen & sediment chemistry: What is the redox continuity layer?

A

The transition layer between oxygen rich and oxygen poor sediment layers

22
Q

Oxygen & sediment chemistry: How does beach profile effect oxygen concentrations?

A
  • Exposed beach = larger particles - aerobic yellow sand
  • Semi-sheltered beach = smaller particles - aerobic yellow sand & anaerobic black sand
  • Sheltered beach - much smaller particles - aerobic black sand / small top layer of aerobic brown sand
23
Q

Oxygen & sediment chemistry: What do burrowing animals do?

A

Generate a respiratory current within their burrows to receive oxygen

24
Q

Oxygen & sediment chemistry: What do some animals do to be able to respire and feed whilst sheltered from predation deeper in the sediment?

A
  • Extend a long siphon into the oxygenated waters

- E.g. some bivalves / Geoduck (Panopea generosa) – largest burrowing clam in the world! Can live >140 years old

25
Q

Biodiversity: What plants can be found on Spartina mudflats?

A
  • Generally no macroalgae
  • Sometimes see blooms of Enteromorpha & Ulva (sea-lettuce)
  • Brown seaweeds (e.g. Fucus) present if attached to pebbles
26
Q

Biodiversity: What do single cell diatoms do in coastal environments?

A

Create biofilms that animals graze upon

27
Q

Biodiversity: What is found in large abundances in soft sediment habitats?

A

Deposit feeders:

  • Corophium volutator
  • Amphipods
  • Arenicola (Lugworm)
28
Q

Biodiversity: What are examples of predators in coastal environments?

A
  • Shore crab
  • Cerianthus
  • Sagaritia
  • Nereis (Ragworm)
29
Q

Biodiversity: What are examples of detritivores in coastal environments?

A
  • Heart urchin
30
Q

Biodiversity: What are examples of omnivores in coastal environments?

A
  • Cerianthus (anemone)

- Nereis (Ragworm)

31
Q

Biodiversity: In coastal environments, what are grazers dominated by?

A

Hydrobia - snails

32
Q

Biodiversity: What are examples of filter feeders in coastal environments?

A
  • Lanice
  • Cerastoderma - Cockle (most common)
  • Mya - soft-shelled clam
33
Q

Biodiversity: What is special about Macoma balthica clams?

A
  • They are both deposit feeders and filter feeders
  • High flow (more food = filter feed)
  • Low flow (less food = deposit feed)
  • Not too many species can switch feeding modes dependent on whether its high or low flow
34
Q

Biodiversity: What are the macrofauna feeding modes?

A
  • Deposit feeders

- Suspension/filter feeders

35
Q

Biodiversity: What determines meiofauna?

A

Pass through 0.5 or 1mm sieve but retained on 45um mesh

36
Q

Biodiversity: What are examples of meiofauna that can be found in the sediment?

A
  • Nematode
  • Polychaete (temporary)
  • Ostrocod
  • Ciliate
  • Gatrotrich
  • Harpacticoid
37
Q

Biodiversity: How many individual meiofauna can be found per m^2?

A

Estimated to be >1 million

38
Q

Biodiversity: What percentage of all individuals on earth do meiofauna make up?

A

~80%

39
Q

Biodiversity: What is the issue with the role of meiofauna in benthic ecology?

A
  • Very few people study it
  • There are few marine ecologists or taxonomists that study meiofauna
  • We know very little about their spatial distribution, seasonal abundance, diversity, between and within habitats
40
Q

Biodiversity: What is the differences in abundance of meiofauna and macrofauna?

A

Typical sandy beach in Europe:

  • More meiofauna than macrofauna
  • Macrofauna has larger biomass but there’s greater numbers of meiofauna
41
Q

Distribution: What is the relationship between meiofauna and sediment particle size?

A
  • Species richness, abundance and total biomass increase with increasing sediment stability (decrease wave exposure)
  • Hard for animals to burrow into exposed zones - less biodiversity
  • Highest biodiversity in muddy/sheltered habitats - easier to burrow
42
Q

Distribution: What is the relationship between macrofauna and tidal height?

A
  • Number of individuals overlap - not a distinctive gradient
  • Lack of vertical zonation in muddy/sandy shore habitats
  • Sediments buffer physical stresses and organisms are mobile
  • Organisms can burrow deeper in intertidal regions
  • Distribution related to particle size, emersion period, depth and water table
  • On sandy shore, zonation schemes have been related to hydrodynamics (water table and wave action)
43
Q

Distribution: What is the relationship between macrofauna and sediment depth?

A
  • Slight zonation pattern
  • Lot of overlap to how far animals can burrow
  • Not that many studies into depth zonation patterns as it’s hard to do

SOES1006 - Marine Ecology & Evolution (4 decks)

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