Particulate matter in the oceans and trace elements Flashcards

1
Q

Name two methods of measures ocean particulate matter

A

Light scattering (Nephelometry - to get a bulk picture (size and shape unknown). Sediment traps to produce an intergrated picture (different sampling times)

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2
Q

What are limitations of sediment trap data?

A

The hydrodynamics across top. Swimmers caught and poisoned. Problems worse in traps shallower than 1000m - more lateral currents and swimming organisms.

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3
Q

Name 4 sources of particles

A

Suspended matter from coastal erosion - Airborne dust - Cosmic dust - Biological particles from within system.

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4
Q

Name 6 forms of biological debris

A

Phytoplankton - Zooplankton - Faecal matter - Shell Debris - Fish and waste products - Marine snow

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5
Q

What does gross suspended matter distribution in the oceans depend upon?

A

On where you are in the oceans - short term seasonal changes - the effect of wind patterns/aridity on dust loading

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6
Q

In a particulate matter profile where is the maximun, and minimum?

A

Maximum at the surface from river and external input and productivity. Minimum in the middle of the water column

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7
Q

In a particle concentration map of the Atlantic why is there more suspended matter in the west than the east?

A

Western boundary currents - increases turbidity and potential to suspend and transport load

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8
Q

What is significant about bigger and denser particles?

A

They fall more quickly and therefore spend less time in mid water

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9
Q

What is significant about dust fallout into the oceans?

A

It acts as a mineral ‘ballast’ to create denser and larger particles and aid more rapid downward transport

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10
Q

WHat is POM?

A

Particulate organic matter

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11
Q

What is significant about settling POM?

A

Short bursts of rapid POM transport from productivity events control the composition of settling particles - chemical characteristics of the settling POM change significantly during transit through the water column,

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12
Q

What is important about re-suspension and lateral advection of particle matter?

A

Has an impact on the BBL (benthic boundary layer) (important in species reproductive strategies such as larvae dispersal - contains nutrients important to species)

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13
Q

What is the PAP (porcupine abyssal plain) in the North Eat Atlantic characterized by?

A

Strong seasonal fluxes of POM which are related to cycles of primary productivity in overly eutrophic surface waters

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14
Q

What is important to remember about trace element data in the oceans gathered before mid 1970’s

A

The data is probably wrong due to contamination and analytical problems

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15
Q

What controls trace element distribution?

A

Horizontal and vertical distribution is controlled by relative rates of supply and removal. Profiles are likely to be conservative in the oceans with a linear correlation to salinity

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16
Q

Why is zinc and silica found with similar depth profiles in the North Pacific (California coast)

A

High correlations provide evidence for the incorporation of the trace elements into the biogenic part of nutrient (Zn and Ni with Si because it is the soft skeleton of organisms - Cd with P in soft skeleton)

17
Q

What happens to trace element concentrations that undergo scavenging

A

The concentrations decrease with depth - surface water enrichment from rivers and atmosphere - removal from rapid precipitation or adsorption onto sinking particles - short residence time

18
Q

What is the impact of land on trace elemental concentrations?

A

Some trace elements come from runoff and anthropogenic outflows. For instance Pb from leaded petrol or Mn from coastal zone or from continental shelf through advection

19
Q

What happens to trace elements if water is anoxic?

A

Poor circulation can mean bottom waters become anoxic if O2 removal > O2 input. (Black sea). Some minor elements can be more soluble in reducing conditions and are in particulate form in oxidizing conditions

20
Q

Where does much of trace metal demand for plankton come from?

A

Plankton in surface waters - less effect from lateral movement or advective processes therefore much comes from the aeolian transport of dust.

21
Q

Show the link between aeolian dust and limitation of plankton by trace elements

A

If some trace elemnts limit plankton then dust is effectively a control of plankton. Plankton controls the biological pump which impacts CO2 levels in the atmosphere.

22
Q

Show the feedback system linking dust to plankton and CO2 changes

A

Climate change - desertification - more wind and aeolian dust - more trace elements - more organic matter and effects on deep ocean circulation (Plankton produce dimethyl sulphide - CCN - more precipiation - increased dust precipitation into oceans - feedback)

23
Q

What is Fe fertilization?

A

In equatorial pacific ocean and Gulf of alaska phytoplankton populations are low despite no nutrient or sunlight limitation - it is the lack of dissolved iron (Fe) causing the issue. Fe fertilization is bio engineering bio adding more Fe to increase production

24
Q

In context of behaviour of salts what do conservative and non-conservative mean?

A

Conservative - unaffected by biological processes. Non-conservative - elements are taken or required by biological processes (essential nutrients) N, P, Si, O2, C, Fe.

25
Q

What is a HNLC?

A

High nutrient, low chlorophyll area. Unporductive seas with high levels of limiting nutrients (N,P,Si)

26
Q

Why are there HNLC’s?

A

Research indicates that 40% of the worlds oceans Fe concentrations are so low that plankton production in Fe limited.

27
Q

When and why were there high Fe levels in oceans?

A

Ice ages from aeolian transport of dust from dry continents.