Nutrients, their cycling, and upwelling · Nutrients, their cycling, and upwelling • Nitrogen cycling – Living is easy when there is upwelling – But when the going gets tough…

Nutrients their cycling and upwelling

bull Nitrogen cyclingndash Living is easy when there is upwelling ndash But when the going gets toughhellip cycle

bull Silica is THE upwelling nutrient ndash Has a deep ocean cycle

Taking the story from the oligotrophic to eutrophic systems

Biolimiting constituents (aka nutrients)

Nitrate (NO3-) Does not limit growth of bluegreen algae

(cyanobacteria) they fix nitrogenSilicate (H2SiO4) Limits the growth of diatoms

Phosphate (HPO4=) the ultimate limiting nutrient for plant growth

Vertical distribution of nutrients

Libes 1992

nitrate 10-6 molliterPhosphate 10-6 molliter silicate 10-6 molliter

nutrients become fully depleted during stratification

Nutrient distribution varies among oceans

bullMixed layer is deeper in Atlantic than in PacificbullRemineralized nutrients accumulate in deep water transported by ocean conveyer belt

Light and nutrients

determine where the productivity

is

Seasonal evolution of mixed layer (physics) sets up the annual cycle of the biologyhellip

PhytoplanktonZooplankton

NutrientsR

elat

ive

incr

ease

Mixing MixingStratified

Light Temperature

Spring bloom

Fall mini-bloom

Productivity follows the nutrient availability

Oligotrophic ocean

bull The nutrient point of view

bull The underlying chemistrybull The controlling chemistry

New versus regenerated production

Lalli and Parsons

Note the biggest arrow is upwelled NO3

Cycling of nitrogen in the ocean

Uptake and use is the dominant parthellip

Biopump of nitrogen in the ocean

Nitrogen limitation and low oxygen

bull ldquoLeaksrdquo in the simple nutrient storybull Nitrogen fixation uArrbull Denitrification dArr

The simple Nitrogen cycle

+V

+III -III

0

-III

Different oxidation states of nitrogen

Libes 1992

The Nitrogen cycle- reality

+V

+III -III

0

-III

PhytoplanktonZooplankton

NutrientsR

elat

ive

incr

ease

Mixing MixingStratified

Light Temperature

Spring bloom

Fall mini-bloom

Annual Stratification sequence

Recycling of nutrients at itrsquos peakhellip and nutrients at a minimum productivity slows down respiration picks uphellip

The Nitrogen cyclehellip when nutrients are low the saviors come along

Energy intensive

+V

+III -III

0

-III

Cycling of nitrogen in the ocean

Uptake and use is the dominant parthellip

The Nitrogen cyclehellip when things get tough

Anaerobic Energy intensiveThe spoilers The saviors

You see the other half of the cycle

Low oxygen and the

ldquospoilersrdquo ΣCO2

The Nitrogen cyclehellip the spoilers

Anaerobic respiration

+V

+III -III

0

-III

Lost to the system

The Nitrogen cyclehellip the whole story

Anaerobic respiration

Energy intensive

+V

+III -III

0

-III

Lost to the system Input to the

system

Input to the system

The Marine nitrogen cycleAerobic versus anaerobic

The Eutrophic ocean

bull In the open ocean upwelling is the eutrophicendmember

bull The ecosystem is different and so is the controlling nutrient

Vertical distribution of nutrients

Libes 1992

nitrate 10-6 molliterPhosphate 10-6 molliter silicate 10-6 molliter

nutrients become fully depleted during stratification

Hydrocast gear

Niskin bottle ldquorosetterdquo with 36 bottles for collecting sub-surface water

Deploying the CTD

CTD preparation and deployment at nighthttpswwwyoutubecomwatchv=wO_Dh97v4QM

CTD Rosette System Deployment and Retrievalhttpswwwyoutubecomwatchv=f_SHCc5Ton4

Underwater view of a CTD casthttpswwwyoutubecomwatchv=LEn2qxSrPm0

Rigging the bottles

Water sampling

Drawing samples from the bottles

Processing the samples

Silica the upwelling nutrient

Silicate (H2SiO4) Limits the growth of diatoms

SiO2 (Silica) is an important nutrient only for diatoms

Siliceous plankton make siliceous oozesDiatoms

Shells are composed of silicon (Si)- (glass)

Form silica deposits on ocean floor (siliceous ooze)radiolaria

silicoflagellates

Vertical distribution of nutrients

Libes 1992

nitrate 10-6 molliterPhosphate 10-6 molliter silicate 10-6 molliter

In upwelling zonesduring upwelling phosphorous and nitrate are generally not fully depleted

The silica cycle (global view)

Silica is undersaturated and dissolveshellip it only forms deposits under major productivity areas

Biological fixation and bio-pump sinking

Siliceous sediments

Upwelling of silica rich water

Enhanced Diatom growth

( Siliceous based productivity)

River input

The biological pumphellip Not only controls carbon but the nutrients including silica

Silica Siliceous sediments

The conveyor belt circulation

And thermohaline circulation moves through the systemhellip

Horizontal distribution of Silicate

We see a dramatic difference in distribution between the Atlantic and the Pacific

Emerson and Hedges (2008)

Silica the upwelling nutrient

Silicate (H2SiO4) Limits the growth of diatoms

SiO2 (Silica) is an important nutrient only for diatoms

Upwelling zones are areas with high diatom productivity because silica is plentiful

This is because silica from deep water is upwelled there

Coastal Upwelling zones in the world ocean

Mann and Lazire

Open ocean zones of upwelling hellip

Mann and Lazire

Distribution of siliceous sediments

Distribution of siliceous sediments largely aligns with upwelling zones

Silica cycling in an upwelling zone

Dissolved silica is present in deep waters

Silica is fixed in the mixed layer

Silica upwells

1

2

34Diatoms die and the

silica tests sink to the sediments while dissolving and may begin to release SiO2

5 Silica dissolves in the sediments releasing SiO2 to the overlying water

This replenishes the SiO2 content of the water locally and can enhance its silica content

Silica cycling in a coastal upwelling zone

Dissolved silica is present in deep waters

Silica is fixed in the mixed layer

Silica upwells

1

2

34

Diatoms die and the silica tests sink to the sediments while dissolving and may begin to release SiO2

5 Silica dissolves in the sediments releasing SiO2 to the overlying water

This replenishes the SiO2 content of the water and can enhance its silica content

Siliceous phyto planktonDiatoms radiolarians silicoflagellates

Diatoms - plants

Cell walls are composed of silicon (Si)- essentially glass

Fixed this lecture

bull Fix this lecturebull The video is broken find a new onebull The Silica portion needs revision so that it

goes logically through global and then to local coastal upwelling rather than back and forth