Particulate matter in the oceans and trace elements Flashcards
Name two methods of measures ocean particulate matter
Light scattering (Nephelometry - to get a bulk picture (size and shape unknown). Sediment traps to produce an intergrated picture (different sampling times)
What are limitations of sediment trap data?
The hydrodynamics across top. Swimmers caught and poisoned. Problems worse in traps shallower than 1000m - more lateral currents and swimming organisms.
Name 4 sources of particles
Suspended matter from coastal erosion - Airborne dust - Cosmic dust - Biological particles from within system.
Name 6 forms of biological debris
Phytoplankton - Zooplankton - Faecal matter - Shell Debris - Fish and waste products - Marine snow
What does gross suspended matter distribution in the oceans depend upon?
On where you are in the oceans - short term seasonal changes - the effect of wind patterns/aridity on dust loading
In a particulate matter profile where is the maximun, and minimum?
Maximum at the surface from river and external input and productivity. Minimum in the middle of the water column
In a particle concentration map of the Atlantic why is there more suspended matter in the west than the east?
Western boundary currents - increases turbidity and potential to suspend and transport load
What is significant about bigger and denser particles?
They fall more quickly and therefore spend less time in mid water
What is significant about dust fallout into the oceans?
It acts as a mineral ‘ballast’ to create denser and larger particles and aid more rapid downward transport
WHat is POM?
Particulate organic matter
What is significant about settling POM?
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,
What is important about re-suspension and lateral advection of particle matter?
Has an impact on the BBL (benthic boundary layer) (important in species reproductive strategies such as larvae dispersal - contains nutrients important to species)
What is the PAP (porcupine abyssal plain) in the North Eat Atlantic characterized by?
Strong seasonal fluxes of POM which are related to cycles of primary productivity in overly eutrophic surface waters
What is important to remember about trace element data in the oceans gathered before mid 1970’s
The data is probably wrong due to contamination and analytical problems
What controls trace element distribution?
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
Why is zinc and silica found with similar depth profiles in the North Pacific (California coast)
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)
What happens to trace element concentrations that undergo scavenging
The concentrations decrease with depth - surface water enrichment from rivers and atmosphere - removal from rapid precipitation or adsorption onto sinking particles - short residence time
What is the impact of land on trace elemental concentrations?
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
What happens to trace elements if water is anoxic?
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
Where does much of trace metal demand for plankton come from?
Plankton in surface waters - less effect from lateral movement or advective processes therefore much comes from the aeolian transport of dust.
Show the link between aeolian dust and limitation of plankton by trace elements
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.
Show the feedback system linking dust to plankton and CO2 changes
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)
What is Fe fertilization?
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
In context of behaviour of salts what do conservative and non-conservative mean?
Conservative - unaffected by biological processes. Non-conservative - elements are taken or required by biological processes (essential nutrients) N, P, Si, O2, C, Fe.
What is a HNLC?
High nutrient, low chlorophyll area. Unporductive seas with high levels of limiting nutrients (N,P,Si)
Why are there HNLC’s?
Research indicates that 40% of the worlds oceans Fe concentrations are so low that plankton production in Fe limited.
When and why were there high Fe levels in oceans?
Ice ages from aeolian transport of dust from dry continents.
