Chapter #8 Trace Metals

What are the two types of nutrients?

Macronutrients and Micronutrients.

What are macronutrients?

Major elements that are limiting factors for plant growth in surface waters (Phosphorus, nitrate, and silica).

What are micronutrients?

Minor and trace elements that can also be limiting.

What are the three types of distributions for minor elements in seawater?

Conservative distribution, Nutrient-like distribution, Particle-reactive distribution.

What is a conservative distribution?

Elements are in constant ratio of concentration to chlorinity or salinity.

What is a nutrient-like distribution?

Elements used in biological processes or body parts, with surface depletion due to uptake by organisms.

What is a particle-reactive distribution?

Elements that stick to the surface of sinking particles and are removed from the water column.

What elements have a conservative distribution?

Molybdenum (Mo), tungsten (W), rubidium (Rb), cesium (Cs).

What elements have a nutrient-like distribution?

Zinc, Cadmium, Nickel, Selenium, Silver, Barium, Germanium.

What elements have a particle-reactive distribution?

Lead.

What factors make Zinc a nutrient-type distribution?

Enzyme co-factor, role in catalysis, essential for phytoplankton to process phosphate.

Describe Zinc's depth distribution.

Depletion in surface waters, deep regeneration due to bacterial oxidation.

What factors make Cadmium a nutrient-type distribution?

Nutrient for phytoplankton, toxic to most other organisms, active center for enzymes.

Describe Cadmium's depth distribution.

Surface depletion, shallow water regeneration, maximum at 1 km.

What factors make Nickel a nutrient-type distribution?

Trace element for many organisms, role in catalysis.

Describe Nickel's depth distribution.

Surface depletion, deep regeneration or a combination of shallow and deep regeneration.

What factors make Selenium a nutrient-type distribution?

Needed for growth of diatoms, important for polar diatom species.

Describe Selenium's depth distribution.

Shallow and deep regeneration, depletion at surface waters, maximum at greater than 1 km.

What factors make Silver a nutrient-type distribution?

Toxic and inhibits copper metabolism in organisms.

Describe Silver's depth distribution.

Surface depletion, combination of shallow and deep regeneration, maximum past 1 km.

What factors make Barium a nutrient-type distribution?

Found in igneous/sedimentary rocks, released by hydrothermal activity.

Describe Barium's depth distribution.

Surface depletion, deep regeneration, maximum greater than 1 km.

What factors make Germanium a nutrient-type distribution?

Can substitute for Si in diatom frustules, more common in organic form.

Describe Germanium's depth distribution.

Surface depletion, deep regeneration, maximum deeper than 1 km.

What factors make Lead a particle-reactive distribution?

Toxic metal, bioaccumulated, higher concentrations in the Atlantic.

Describe Lead's depth distribution.

Surface enrichment, depletes rapidly with depth.

What factors make Aluminum a mid-depth minima distribution?

Not influenced by humans, consistent surface source from atmospheric dust.

Describe Aluminum's depth distribution.

Particle reactive from surface enrichment, mid-depth minimum from scavenging.

What is a complex distribution?

A distribution that does not fit into the standard categories.

What are some factors that make Manganese a complex distribution?

Role in catalysis, enzyme activation, nitrification; oxidation and reduction states influence behavior; source in Pacific surface waters from runoff.

Briefly describe Manganese's depth distribution.

Higher in surface waters, decreases with depth; mid-depth maxima in sub-surface zone from runoff and hydrothermal vents.

What are some characteristics of Mercury?

High surface tension, low vapor pressure, high density, low solubility in three oxidation states; photoreactive and toxic; complex biogeochemical cycling.

Briefly describe Mercury's depth distribution in the Atlantic.

Shows quasi-conservative profiles with high surface values and little depth accumulation; hydrothermal vent on Mid-Atlantic Ridge is a source.

Briefly describe Mercury's general depth distribution.

Higher near coast and in polluted areas; generally supersaturation in surface water; transport and burial in marine sediments.

What are some factors that make Copper a complex distribution?

Role in electron transport, catalysis, denitrification; binds strongly with organic ligands; toxic to invertebrates.

Briefly describe Copper's depth distribution.

Does not follow phosphate or other nutrients; acts more like a particle-reactive distribution with deep-water regeneration.

What are some factors that make Iron a complex distribution?

Exists as ferrous (Fe II) and ferric (Fe III); solubility influenced by oxidation/reduction states.

Briefly describe Iron's depth distribution.

Low solubility of inorganic iron; some ocean areas termed high-nutrient low-chlorophyll (HNLC) regions.

What are some factors that make Cobalt a complex distribution?

Important for cyanobacteria growth; incorporated into vitamin B12.

Briefly describe Cobalt's depth distribution.

Surface depletion indicative of biological utilization; mid-depth maximum observed in northeast Pacific profiles.

Why would metal profiles be higher in the Pacific?

Trace metals accumulate in older water masses; Atlantic surface waters have higher levels due to dust inputs.

Why would metal profiles be higher in coastal waters vs Open Ocean?

Higher metal levels in coastal/shelf waters due to land runoff.

Name some trace metals influenced by bonds with ligands/organic complexes.

Fe3+, Cu, Zn, Co, Cd; exceptions are Ni and Mn.

What elements are essential for the metabolism, growth, and reproduction of all marine phytoplankton?

Mn, Fe, Co, Ni, Cu, Zn, Cd; hierarchy: Fe, Zn > Mn, Ni, Cu > Co, Cd.

Which elements are geochemical tracers?

Silver, Germanium, Lead.

Which elements have high surface values, and why?

Cobalt, Mercury, Lead, sometimes Silver, Aluminum, Manganese; due to dust and anthropogenic inputs.