WATER

Its Freezing Point and Density

- freshwater ice floats on non-frozen seawater 

- as salinity increases, temperature decreases

- as salinity increases, density increases 

- as temperature decreases, density increases

Pressure and Depth Correlation

- as depth increases, pressure increases 

Pressure with respect to Organisms 

- eurybathic: can tolerate a wide range of pressures 

- stenobathic: cannot tolerate a wide range of  pressures

Global Ocean 

Surface Currents 

- in N hemisphere, currents run clockwise

- in S hemisphere, currents run counterclockwise

- located in the middle of counterclockwise and clockwise currents 

- also known as "ocean deserts" 

Global Ocean 

Surface Currents: Gulf Stream

Global Ocean 

Surface Currents: Antarctic Circumpolar Current 

Global Ocean 

Surface Currents: Western 

Intensification 

Global Ocean 

Surface Currents: Alaskan Current 

Upwelling and Eckman Driven Currents 

- in N hemisphere, upwelling occurs due to wind

blowing from the North pushing water to the right 

- in S hemisphere, water is pushed to the left 

- upwelled water brings a lot of nutrients and tends to be the most productive areas 

Downwelling 

Global Ocean Conveyor Belt

- ice forms in the poles and causes seawater to get saltier and colder, thus sinking. 

- this water then moves along the bottom of the sea and joins the cold Antarctic water

- this water moves towards the Pacific Ocean where it gets less dense and can travel along the surface waters to return to the the poles

- this process takes about 1000 years! wow. 

The Changing Oceans (40 year span) 

- there's been +0.5 p.s.u.(saltier) increase in the Tropics 

- in the N and S poles, water has gotten fresher

Chemistry: 

Pacific Ocean Plots 

- oxygen: driven by temperature (higher temp = less oxygen)

- nitrate + phosphate = limiting reagents 

- silica: low concentration in Pacific, higher concentration in N and S poles 

Gases in Seawater and Atmosphere 

- more NITROGEN in atmosphere than in ocean

- CO2 is 83% by volume in the ocean

- oxygen is 6% by volume in the ocean

- nitrogen is 11% by volume in the ocean 

The Bjerrum Plot of the Ocean:

CO2 Buffering System

- pH of ocean ~8.1 today

- if pH moves to the left of the Bjerrum plot (decreasing pH), CO2 in water increases, which increases acidification

- this natural process is usually driven by photosynthesis and respiration 

Ocean pH varies w.r.t. CO2 Levels 

- each 0.1 unit change is significant because pH is a log scale

- this greatly affects organisms 

Sensing the Oceans 

- weather satellites

- manned space stations

- aerial surveys

- oceanographic buoys

Stations that Measure pH and CO2

1. HOTS: station in Hawaii

2. BATS: station in the middle of the Atlantic 

Data from both stations shows an increasing trend in CO2 levels and decreasing pH levels (over 20 years) 

- lowered pH could alter calcification of ocean organisms 

Ocean Biogeochemical Cycles:

C,N,O,P,S, and Si 

- sulfur fluxes coming out of sea

- CO2 coming in and out of sea

- evaporation due to solar radiation

- winds set up upwelling zones

Energy and the Elements

- autotrophs make organic compounds (living off light energy)

- chemoautotrophs live off chemical substrates

- photoautotrophs are aerobic

- heterotrophs need sugars

Carbon: Global Carbon Cycling

- 800 Gt in atmosphere

- 7000 Gt in fossil fuels 

- 38500 Gt in oceans (biggest resevoirs of carbon)

- deep ocean water pulls carbon down from the surface water where it turns it into photosynthetic material 

CO2 in the Atmosphere

- most CO2 comes from fossil fuels and deforestation

- atmospheric carbon has never been so high before (peaked ~ 1950) 

Ocean pH: Past and Present 

- ocean acidification has increased over the years

- as ocean pH declines and carbonate becomes less saturated, this is bad for calcified organisms 

Nitrogen

- less abundant 

- N gas gets fixed into an organic form

- in its inorganic form, it undergoes different pathways to either become ammonia in oxygenated water or with less oxygen

- ammonia is cycled quickly = regenerated production

- nitrate is upwelled = new production

"f-ratio" = new prod / total prod

Oligotrophic

Eutrophic

Oxygen Cycling 

- dead zones driven by nutrient-based runoff

- nutrients --> phytoplankton blooms --> more organic carbon, more O2

Pycnocline 

- boundary keeps surface mixed layers (lighter, fresher, warmer) separate from deeper mixed layers ( colder, saltier, denser) 

- phytoplankton sink through density layer --> bring organic carbon to deeper layer --> heterotrophs use up oxygen in deeper waters--> leads to mortality of animals that live there

Phosphorous Cycling 

- rarer than Nitrogen, essential to ATP, RNA, DNA

- in contrast to Nitrogen, pretty much NO transformation in P cycle is driven by microbes

- it is dependent on geo-sources: rivers, from atmosphere (dust and particles) 

Sulfur Cycling 

- inorganic: sulfides, sulfates, elemental sulfur

- organic: animal protein, plant protein, organic waste

- rarer than N

- only 2 in 20 amino acids, but no proteins needed for disulfide bridges 

- largest flux = sea spray

- human fluxes (15-40Mt) to that of net natural fluxes (20-30Mt)

- acid rain from sulfites 

An Ocean Sulfur Story

1. growth of E. huxleyi cells

2. preferential grazing on low DMSP lyase cells

3. DMSP

4. viral lysis - DMS release

5. bacterial role in regulating DMS

- phytoplankton produces DMs --> cloud condensation nuclei --> climate feedback 

Silica Cycle 

- NOT impacted by microbes, driven by terrestrial sources

- critical to diatoms 

- primary source is rivers (140Mt)

- secondary source is wind and sea bottom geology

- rapidly remineralized in the surface ocean 

Chrysophyta

- golden-brown algae + silicoflagellates

- coccolithophores

- diatoms 

Golden Brown Algae, Silicoflagellates, Coccolithophores, and Diatoms

- unicellular, often flagellated, Si/Ca structure common

- chlorophyll a and c

- xanthophyll and carotene 

Diatoms

(dinoflagellates) 

- unicellular or colonial, flagellated 

- chlorophyll a and c

- xanthophyll and carotene 

Cyanobacteria

(blue-green algae)

- unicellular, prokaryotic, nonflagellated

- chlorophyll a

- carotene and phycobilin

- responsible for much primary production

- important for fixing carbon 

Golden Brown Algae 

- naked, flagellated cells

- most mixotrophic: grazers of bacteria and cyanobacteria 

- not well studied 

Silicoflagellates 

- not very abundant 

- body wraps around siliceous framework

- 2 flagella

- most abundant in cold waters 

i.e. Dictyota

Coccolithophores

- CaCO3 instead of silica

- coccoliths cover surface

- bloom former

- significant global primary producers 

i.e. Emiliania huxleyi (dominant during blooms in the Sargasso Sea and Gulf of Alaska) 

Prymnesiophyceae

- unicellular, motile

- lack coccoliths 

i.e. Phaeocystis (blooms on beaches)

Chrysophyta: Diatoms

- unicellular/chains, non-motile

- pennate/centric

- 2 valved extracellular skeleton made of silica

- abundant

- bloom former

i.e. Chaetoceros, Thalassosira, Coscinodiscus, Skeletonema 

Dinophyta: Dinoflagellates

- unicellular (+/- theca)

- 2 flagella

- can be an auto, hetero, or mixotroph

- bloom post-diatoms

- diel vertical migration 

- NOT the most abundant phytoplankton in the nutrient poor seas

i.e. Ceratium, Gonyaulax, Dinophysis, Gymnodinium 

Diatoms (cont.) 

- first started out in centric form, then became more pennate

- 150 million years ago, the only place available was the open ocean, but as it expanded, more benthic space became available and so developed the pennate form 

Toxins

Organism: Pseudonitzschia

Disease: amnesic shellfish poisoning

Toxin: domoic acid 

Mechanism in humans: overstimulates nerve cells 

Toxins

Organism: Gambierdiscus

Disease: Ciguatera fish poisoning 

Toxin: ciguatoxin, maitotoxin

Mechanism in humans: keeps sodium or calcium channels open 

Toxins

Organism: Kareniabrevis

Disease: neurotoxic shellfish poisoning

Toxin: brevetoxin

Mechanism in humans: keeps sodium channels open 

Toxins

Organism: Alexandrium 

Disease: paralytic shellfish poisoning

Toxin: okadaic acid, pectenotoxin, yessotoxin, dinophysistoxin

Mechanism in humans: inhibit proteins that control sodium secretion by intestinal cells 

HABs

Organism: Pfisteria piscicida

HABs

Organism: Heterosigma akashiwo

Common Name: brown tide

Mechanism of Harm: unknown 

HABs

Organism: Chaetocerous convolutus

HABs

Organism: Aureococcus anophagefferens

Common Name: brown tide

Mechanism of Harm: mucopolysaccharide clogs filter feeder gills 

Cyanobacteria

- prokaryote (no chloroplast)

- unicellular or colonial

- lack protective shell

- non-motile, autotrophic

- some N-, all C-fixation