BIOL 311 PARTII Flashcards
wavelength to measure silicic acid
410nm by visible spectrophotometry
silicic acid
Si(OH)4
most common way to determine amount of phytoplankton in seawater
Chlorophyll (mostly Chl a)
[Chl]
index of phytoplankton biomass
intensity of fluorescence is proportional to amount of Chl and thus biomass
most common way to measure Chl
use acetone to extract Chl from filtered sample, measure fluorescent using fluoromoeter
fluorescence
photosynthetic pigments absorb light at one wavelength and emit light at another
breakdown products of chl produced by zooplankton digestion
phaeopigments
nitrate
NO3 -
Secondary production
amount of new zooplankton tissue elaborated per unit time
zooplankton are
secondary producers
key link between PP and higher trophic levels
key zooplankton species
copepods
PP regulated by
availability of light and nutrients
principle photosynthetic pigment in all phytoplankton
Chlorophyll (mostly Chl a)
Secondary production regulated by
food availability
temperature
predation
food chain in upwelling systems
pretty simple chain
phyto.–zoo–higher trophic levels
NO2-
nitrite
food chain in open ocean
more complex web
‘secondary production’ somewhat ambiguous
estimating SP
TTE
Measuring (3 methods)
TTE
Trophic Transfer Efficiency
TTE (Et) = Pt / Pt-1
TTE = amount of E; annual production at t / annual E in lower trophic level
TTE assumptions
TTE of 10% is always a good estimate
We can account for biomass of all un-fished species in food web
IS TTE reliable
TTE often 15-20% at lower levels, using 10% not always adequate, would lead to underestimates, better to measure SP directly
Why is it easy to measure PP
can measure various ways: O2 production, CO2 uptake, nutrient uptake, colour w/ satellites
Rapid generation time: can estimate PP w/i few hours
why is it not easy to measure SP
Much slower growth (weeks-months)
Have to focus on one species at a time
Methods for measuring SP
physiologic method
cohort analysis
chitobiase method
The physiologic method
only certain amount of phyto. E is transferred to zoop.; calculate all inputs and outputs; requires a lot of information
Inputs/outputs in SP
Input: phytoplankton
Outputs: respiration, excretion, defecation, death, melting, consumption by predators
Cohort analysis
follow zoopl. cohort through t; must know length of life stage and weight, very difficult at sea
Copepod life cycle
12 stages: adult, nauplii (6?), C1-C5 copepodites
seasonal vertical migration
rise to surface as nauplii early spring
SP cohort analysis, abundance vs time
Abundance (m^-2) vs Time (days)
abundance increase and decrease for each life stage, curves progress with time for successive life stages
Cohort analysis, 2ºP =
Σ G_i B_i
weight-specific growth rate of stage i * biomass of stage i
Biomass =
B = X* w X = # individuals w = weight of individual
Production =
P_t = [(X1-X2) * (w1+w2)/2] + (B2-B1) x = # individuals w = average weight B = biomass
Cohort analysis assumptions
populations are synchronous
sampling animals each day
not very accurate, makes difficult to use correctly
Landry, 1978
one of few proper cohort analyses
found production rate for single copepod species, single season, in a single lagoon
not comparable to high resolution of PP studies
synchronous populations
developing through life stages at the same time
Mesocosm
encircle large V of water + plankton
typically 2-5m wide, 3-10m deep
popularized in oceanography by Tim Parsons
Artificial cohort method
popular field method
incubate specific stages/size classes for short periods
problems with artificial cohort method
repeated handling (damaging)
container effects (food, T)
assumes asynchrony
time consuming, laborious (have to sieve samples and separate stages)
Chitobiase method
Biochemical method for rapid estimation
measure chitobiase in water sample
fast and relatively simple
what is chitobiase
crustacean moulting enzyme that recycles chitin during moulting of an individual
amount of chitobiase is proportional to body size
Chitobiase method assumptions
decay rate proportional to production
what does chitobioase method tell
estimate of average development rate of crustacean zooplankton community
what is needed for chitobiase method
rate of decay of chitobiase from seawater sample
Chitobiase method benefits
Fast, relatively simple, versatile, high resolution over short time
Zooplankton food
phytoplankton
protozoans
other zooplankton
zooplankton food use
growth
reproduction
routine metabolism and respiration
how much food do zooplankton need
smaller zoop have higher weight-specific food requirements
smaller, higher T = higher metabolic rates
food required (zooplankton)
inversely proportional to size
How much phytoplankton do zoop consume
ca. 10-40%
occasionally nearly 100% of daily PP
Zoop. food limitations
in lab higher nutrition levels required than are found in ocean, at low [food] there were lower body weights
Zoop in ocean not starving, reproduction not limited, food availability doesn’t seem limiting
Field measurement of zoop reproductive output
usually show little-no relationship w/ food concentration
What does Zoop growth rate depend on
*Temperature
body size/metabolism
resources
max zoop growth
only occurs above threshold food concentration
highest for youngest stages
zoop growth open ocean vs coastal
food-limited growth at [food] found in oceanic areas regardless of T
habitat T vs food concentration
Cm, Cc increase w/ decreasing T
oceanic organisms fall mostly below Cc, some above at very low T
Coastal zoop almost entirely above Cc
Cm
matintenance food concentration
assimilation balances respiration
below equals starvation (not enough food to meet metabolic needs)
Cc
critical concentration
above which growth rate is max
Habitat T vs Food concentration, Juvenile, Adult
Cm, Cc increase more at low T for adults, i.e. adults have more challenges reaching max growth at low T
Food limitation conclusions
food limited growth most likely in oceanic conditions and large zoop
why do only lab studies find food availability matters for zoop growth
either erroneous results or underestimate real food availability
Huntley-Lopez Model (1992)
re-analyze published data, find T alone explains >90% of growth rate variation
suggest that SP can be estimated as fn of T
Huntley-Lopez model, SP =
B * 0.445 *e^0.111T
T = temperature
B = biomass
SP in g C m^-3 day^-1
criticism of Huntley-Lopez model
relies mostly on lab data collected under unrealistic condition
doesn’t align with what is seen in field
food quality and zoop
bioindicators (e.g. fatty acids) have been shown to affect reproductive success and growth rate
Annual changes in temperate oceans
angle of sun insolation stratification nutrients compensation depth
summer in temperature oceans
sun shines straight -highest concentration of energy- high heating of water- stratification- high PP - nutrient decline- deep compensation depth
PP, SP patterns in temperature oceans
PP, SP high (peak) in spring, decrease in summer due to low nutrients, secondary bloom in fall due to upwelling (wind mixing, tides, etc), may be mini blooms throughout
why does PP decrease after bloom
decreased nutrients
increase in SP - grazing
overall temperature ocean productive pattern
strong seasonality
large export flux
polar ocean productivity patterns
only 1 bloom, in summer, phyto/zoo/ nutr curves all pretty tightly coupled, strong seasonality
tropical ocean productivity patterns
strong, permanent thermocline, barrier to mixing, low nut, low productivity year round, no blooms, very low increases/decreases (small blooms from small scale mixing), no seasonality, very little export flux
tropical ocean productivity relies on
remineralization - regenerated system
regenerated nutrients
ammonium, urea
exceptions to low productivity tropics
coral reefs
equatorial and coastal upwelling zones
temperate ocean productivity limitations
winter - light
spring/summer - nutrients
polar region limits to productivity
summer - nutrients
all other times - light
tropical region limit to productivity
all seasons - nutrients
main grazers of ‘large’ phytoplankton cells
copepods
why are phytoplankton blooms possible if they are grazed
zoo grow slower
average productivity of upwelling zone
500 gC/m2/yr
what areas of the ocean are most productive?
depends - per m2 = coastal, but coastal zones are small… overall = open ocean (pay attention to units)
front
relatively narrow region characterized by large horizontal gradient in variables (e.g. T, S, D); sharp changes
example of a frontal system in the ocean
edge of the continental shelf – increased productivity parallel to shore
between islands - different depths, flow lines changed
Island effects
vertices formed downstream of a current moving past an island, disrupt nutrient patterns
tidal effects
moving through narrow pass (e.g. estuary) causes eddies to form - disrupt water/nutreint patterns
average productivity of open ocean
125 gC/m2/yr
Large-Scab patchiness caused by
coast, river-plumes, fronts, island effects, divergence/convergence, gyres
In NH net water movement is
to the right
Continental divergence
water moving away from shore, deep water rises to replace = upwelling; always on W side of continent because waters are moving away (NH and SH)
Planetary fronts
span entire ocean basins
average productivity of continental shelf
360gC/m2/yr
example of planetary front
Antarctica circumpolar current
Between subtropic and subpolar gyres
anticyclonic gyre
clockwise circulation in NH (counter clockwise in SH)
water moves ‘in’ (to the right)
downwelling
warm water
average productivity of coral reef
2000gC/m2/yr
continental divergence =
high productivity
continental convergence
waters ‘pile up’, downwelling, poor productivity, generally E side of continents
gyre right hand rule
clockwise gyre - wrap fingers clockwise - thumb points away - water moves down
effects of anticyclonic gyre
downwelling - warm water– low productivity
warm core ring
anticyclonic gyre
where reefs are generally found
continental convergent areas
cyclonic gyre
anticlockwise circulation in NH (clockwise in SH)
water moves up/out (to the right)
upwelling, divergent, cold (NH and SH)
cold core ring
cyclonic gyre
Small-scale patchiness
Langmuir circulation
Deep scattering layer
Langmuir circulation
‘streaks’ formed between langmuir cells; from moderate, persistent wind producing convection cells in topmost layer of water w/ long axes
Deep scattering layer
result of diel vertical migration
CO2 over the last 20,000 yrs
slow, steady increase up to 1800s then major increase
effects of cyclonic gyre
upwelling - cold water - high productivity
CO2 in 1750
277ppm
CO2 in 2016
405ppm
46% increase since 1750
first daily measurements of CO2 over 400
May 2013
where are CO2 measurements made
Mauna Loa
Fossil emissions graph
CO2 emissions per year = steady incline from 1990-now
current CO2 emissions
9.9Gt C/yr
contributors to CO2 emissions
Highest to lowest: Coal, oil, gas, cement
all have increased
year-to-date globally averaged land surface T
1.48ºC above 20th century average
year-to-date globally averaged sea surface T
0.77ºC above 20th century average
RCP
Representative concentration pathways
IPCC 5th assessment RCPs
RCP8.5 =3.2-5.4ºC
RCP6 = 2-3.7ºC
RCP4.5 = 1.7-3.2ºC
RCP2.6 = 0.9-2.3ºC
Ice cores can tell how far back
800,000yrs
RCP path we are on
likely not possible to meet RCP2.6 or RCP4.5 would have to remove CO2
Dominant physical changed expected in the oceans as a result of climate change
surface layer warming
surface layer freshening
shallowing of upper mixed layer
increased stratification at base of mixed layer
changes in wind patterns and storm tracks
physical changes to the ocean from climate change greatest
at high latitudes
results of increased ocean stratification
less ‘diffusion’ of O2 down = anoxia
less mixing of nutrients up = lower productivity
freshening is the result of
increased precipitation and glacial melt
organisms in a changing climate, MAAD
Move
Acclimate
Adapt
Die
organisms in a changing climate, move
shift range poleward (or to higher elevations) following rising isotherms
organisms in a changing climate, acclimate
survive outside of normal range organisms previously existed
dependent on plasticity
organisms in a changing climate, adapt
over multiple generations
- evolve w/i existing phenotype
- evolve through genetic mutation
organisms in a changing climate, die
locally, regionally, or globally extinct
terrestrial organisms are shifting how much
2-3X faster than previously reported
17km/decade poleward
11m/decade vertically
marine organism range shifts
190+/- 38 km/decade SE
changes in fish assemblage at fixed locations
smaller, faster growing fishes increasing (sculpin, hagfish, cod)
larger fish decreasing (pout, pollock, haddock, ray)
changes in plankton with climate change
biomass peaks occurring earlier
mismatch with timing of predators (migrating, reproducing)
what happens to the ocean with an increase in CO2
increased acidity
CO2 + H20 - HCO3- + H+ – CO3^2- + 2H+
Bjerrum plot
concentration vs. pH
CO2 peak – HCO3 peak – CO3 2-
current seawater pH
ca. 8
pH =
- log [H+]
add CO2, increase H, decrease pH
problems with low pH
hard on shell-builders (coccolithophores, pteropods, corals, shellfish) that are important to marine food web and economically
onshore vs offshore pH
Onshore regions lower pH than offshore due to upwelling of lower pH waters
USA shellfish economic value
$270M
3200 jobs
threatened by ocean acidification
Canada shellfish economic value
> 12,000t oysters annually
>$18M / yr
oxygen changes in the ocean
w/ increasing T and CO2 = decreasing O2
in low O2 environment
have to work harder to obtain O2 and to expel CO2 (lower pO2, high pCO2)
Optimum aerobic performance can not be maintained – fitness window becomes narrower, and peak performance decreases
most likely increase in T by 2100
3ºC
Increase in sea level since pre-industrial
ca. 0.25m
expected sea level rise by 2100
RCP2.6 = 0.65m RCP8.5 = 1m
Ωarg
degree to which seawater is saturated with aragonite
changes in Ωarg
∆[carbonate ion] results in ∝change in Ωarg; ocean acidification = decline in Ωarg = harder for marine calcifies to precipitate skeletons/shells
Energy flow in marine ecosystem
sun - PP - SP - carnivores
all stages transfer E to decomposers
mineral cycling in marine ecosystems
(PP - SP - Carnivores) - Decomposers - Nutrients - PP
What is a trophic pyramid
size of each layer represents relative biomass of organisms at that trophic level
trophic level
group of organisms occupying same position in a food web
Amount of E available to higher trophic levels depends on
Amount of PP
TTE
# of trophic levels
e.g. of trophic levels being dependent on PP
Highly productive waters (NW Atl) have higher fish/squid populations
low productivity waters (Baltic) have low carnivore #s
Types or marine food chains
oceanic type
coastal type
upwelling type
upwelling type food chain
microphytolankton - pelagic :(macrozoop. - zooplanktiverous fish - piscivorous fish)
benthic (benthic herbivores - benthic carnivores - piscivorous fish)
upwelling type food chain
macrophytoplankton - (planktiverous fish)
megazooplankton - planktiverous whale
nanaoplankton
flagellates
oceanic piscivorous fish
tuna, squid
benthic herbivores
clams, mussels
planktiverous fish
anchovy
megazooplankton
krill
macrozooplankton
copepods
megazooplankton
chaetognaths
zooplanktiverous fish
herring
oceanic type food chan
nanoplankton - microzooplankton - macrozooplankton - megazooplankton –zoplanktivorous fish - piscivorous fish
benthic carnivores
cod
coastal piscivorous fish
salmon, shark
microphytoplankton
diatoms, dinoflagellates
Mean PP: Oceanic, coastal, upwelling
O: 75 gC/m2/yr
C: 300
U: 500
number of E transfers between trophic levels: Oceanic, coastal, upwelling
O: 5
C: 3
U: 1.5
Average TTE: oceanic, coastal, upwelling
O: 10%
C: 15%
U: 20%
mean fish production: o, c, u
O: 0.75 mgC/m2/yr
C: 1000
U: 44, 700
Microbes in the ocean
phytoplankton/algae fungi (rare, poorly known) protozoa (flagellates, ciliates) archaea (poorly known) bacteria (mainly heterotrophs) Viruses (phages, animal viruses)
Virus size
0.01-0.2µm
Marine prokaryotes
Eubacteria, Archaea
single celled, no nucleus, very small
most of genetic diversity on Earth
where are Eubacteria found
water column
sediments
where are Archaea found
in extreme environments
Bacterial cell densities in marine environment
Estuary: >5x10^6 cells/mL
Coastal: 1-5x106
Open ocean: 0.5-1x10^6
deep sea: less than 0.01x10^6
typical bacteria density in ocean
10^5-10^6/mL
overall concentration of bacteria in ocean
1.6x10^29
prokaryote sizes
0.2-1µM
Bacteria, Archae
amount of bacteria that are heterotrophic
90-95%
amount of organic C in ocean that is heterotrophic bacterial
70%
amount of organic C in ocean that is bacterial
90-95%
eukaryote microbe sizes
1-200µM
Algae, protozoa
when were marine bacteria recognized as important
1970s
why was it hard to recognize bacteria in the ocean
small - need microscopy
culturing - not useful for marine
scientific advancements that allowed the recognition of marine bacteria
fluorescent dyes that bind to nucleic acids
now we count/ID bacteria using
epifluorescence microscopy
flow cytometry
what happens to bacteria in the ocean
consumed by other plankton
lysed by viruses
lysis
the disintegration of a cell by rupture of the cell wall or membrane
what do heterotrophic bacteria eat
primarily DOM
from: phytoplankton fluid, excretory products, viral lysed cells, sloppy feeding left overs
DOM
dissolved organic matter
passes through 0.45µm filter
DOC
dissolved organic carbon
primary component of DOM
Microbial loop
fish - zooplankton - ciliates - micro flagellates - bacteria - remineralization - nutrients
Marine viruses
no metabolism, inject genetic material into host and force replication, most abundant life in ocean, ubiquitous
marine viruses known since
1990s
typical marine virus concentrations
10^7 - 10^11/mL
order of magnitude more than bacteria
rate of marine viral infections
ca. 10^23 infections /second
Marine virus habitat
greatest abundance in surface (upper 200m), nearshore
why are the majority of viruses in the surface
because thats where the majority of hosts are
main marine viral infections
heterotrophic bacteria = bacteriophages
ecological role of marine virus
bacterial mortality (including HAB) major biomass turnover
ecological role of marine heterotrophic bacteria
nutrient cycles - remineralization
microbial loop
pollution remediation
When did the Atlantic cod population collapse
1980
catastrophic in 1992
Cod
demersal, longlived (20+yrs), early maturity (2-4yrs), omnivorous, broadcast spawn, highly fecund, soniferous, easy to dry and salt
demersal
living close to the floor of the sea
East coast high productivity
front where Gulfstream meets Labrador current
Georges bank prey
phytoplankton
flagellates
ciliates
copepod nauplii
Georges bank target species
Copepods
haddock larva
cod larva
Georges bank predators
euphausiids hydroids amphipods chaetognaths ctenophore siphonophore medusa herring mackerel
early cod fish harvesting methods
handline
longline
gillnet
Cod fisheries, 1700
shipped to europe
linked to slavery, sugar cane, rum
helped start American revolution ($)
effects of bottom trawling
total destruction of deep sea habitats
fishing technology
steam powered trawl vessels catch 6X faster
diesel powered even more efficient
amounts of fish harvested
1920s - 1250,000t
1960- 200,000t
1965- 760,000t
populations declining 1966-1970
why didn’t fishing stop with declining populations
weak regulations, poorly enforced, insufficient
solution to the overfishing
extend fishing grounds from 12-200nautifcal miles (EEZ)
Fish stocks 1980
haddock, yellowtail flounder stocks collapse
rely entirely on cod
landings drop from 1.6bill-220mil to 1991
changes to allowable fishing after 1991
1994 new rules license moratorium reduced allowable days at sea (DAS) closed portions of Georges Banks new fish, mesh size restrictions designed to reduce fishing efforts 50% over 5-7yrs
total cod harvested from NWFL
100milliont
1/2 1500-1900
1/2 1900-2000
expected recovery after 1993 reduction in fishing effort
not yet occurred
why aren’t cod recovering
shrimp, crab catch has gone up significantly
took over new niche space opened up by cod
groundfish - pelagics - crustaceans
coastal zone
narrow strip of ocean from edge of continental shelf to the estuaries
waters less than 200m
coastal zones are how much of ocean surface
7%
coastal zones are how much of ocean volume
much less than 0.5%
importance of coastal waters
most biologically productive parts of worlds ocean
nutrient-rich, high PP
major role in biogeochemical cycling
most of worlds greatest fisheries
anti-cyclonic retention cycle
meeting of currents = anticyclonic gyre; productivity due to frontal zone, larvae retained in gyre, make way down to rocky bottom; Nutrients not upwelled but larvae returned
coastal processes complicated by
shallowness
freshwater input
tidal currents
upwelling events
organic carbon in coastal ocean compared to open oceans
8-30X more Corg
coastal ocean Corg burial
80% of Corg buried in coastal zone
large % of CaCO3 and SiO2 also deposited
coastal zone production
14% of total global
80-90% of new production
50% of denitrification
productivity of river/estuarine plume
high PP due to increased nutrs. and light levels; where fresh water meets the seawater mixing causes entrainment of particles from deeper water in to the surface = small-scale upwelling
increased bio activity from plumes due to river input
increased turbidity and nutrient enrichment from river (particles, sediment, nutrients)
increased bio activity at plumes from seawater input
nutrient entrainment and upwelling
increased bio activity from plumes due to stability
enhanced stability due to freshwater/dense water layering
importance of estuaries
Among most productive enviro.s on E high PP nursery grounds economically relevant important associated environments
important environments associated with estuaries
salt-marshes
mangrove swamps
where are mangrove swamps
coastal zones near equator, around N half of Australia
where are salt marshes
N coast of Europe, Asia
E/W coasts of US
SE coast SA
North Atlantic conditions
Warm (8.5ºC at depth in winter) Very low N in summer No Fe limitation Large # diatoms, photosynthetic dinofl., benthic fish HCLN poor phyto/zoo coupling high phyto. export
North Pacific conditions
Cold (3.8ºC at depth in winter) High nutrients yr round Iron limited Large # small photosyn. flagellates, large # pelagic fish HNLC close phyto/zoo coupling low phyto. export
dominant N Atl copepod
Calanus finmarchicus
dominant N Pac copepod
Neocalanus plumchrus
C finmarchicus cycle
surface before fully developed (low fitness), no significant impact on phyto., feed - grow - lag in bloom; up and down through summer, lower pressure on phyto.
N. plumchrus
cover water = reserves = greater fitness, surface as adults, keep phyto in-check through summer, much greater impact
how life stage affects ability to graze bloom
C finmarchicus
need to grow and gain energy before able to graze to full potential
concentration vs distance from shore
estuary/inner shelf = high nut., phyto bloom, decrease in euphotic zone depth
outer shelf/open ocean = low phyto., low nutrients, low euphotic zone depth
HOTS
Hawaiian Ocean Time-series Study (NPCG)
BATS
Bermuda Atlantic Time-series Study (Sargasso Sea)
HOTS/BATS
very low productivity no upwelling very stable systems permanent thermoclines low, but very deep productivity
subtropical gyres
anti-cyclonic flow
convergent - water piles in center, stabilizes, warm, oligotrophic
subtropical gyre temperatures
surface layer: ca. 18ºC (winter) - 25ºC (summer)
subtropic gyre thermocline
seasonal: 50-70m
permanent: ca. 125m
subtropic gyre productivity
Net photosynthesis positive, nitrate depleted, phosphorus nearly depleted to ca. 125m
oligotrophic
low nutrients
low productivity
high oxygen
subtropic gyre chl max
deeper than other systems (like temperate, subarctic, coastal)
why is chl max deep in subtropic system
low vertical mixing leaves high nutrients at depth
60% of deep phytoplankton is cyanobacteria
why was there found to be a high % of cyanobacteria in tropical systems
N2 fixers
nitrogen fixing cyanobacteria
Trichodesmium
Why is N2 fixation high in Sargasso Sea
N Africa aeolian dust (Fe)
Affect of N2 fixation on redfield ratio
larger supply of N so P becomes limiting factor
e.g. N:P Sargasso = 17:1 (BATS)
key feature of subtropical gyre
water column stability
Tropic mesozooplnkton
continuously active no seasonal rest phase diverse low biomass keep production nearly in balance
Normal conditions in the equatorial Western Pacific
low pressure
rising air
cloudy/rainy
trade winds come from the East
normal conditions in equatorial eastern pacific
high pressure
sinking air
clear, dry weather
trade winds blow to the West
Equatorial Pacific trade winds
southeast, move from E–>W, cause Peruvian upwelling, creates a warm ‘pool’ of water along W Pac
main places N2 fixation occurs
**Sargasso Sea
NPCG (NP Central Gyre)
what happens during ENSO
winds change direction - upwelling shuts down
Effects of ENSO
change in productivity, fishery yield, mammals/birds, weather patterns, global climate, alter jet stream, harmful and beneficial results
frequency of ENSO
2-10 yrs
ENSO index
weighted average of atmospheric and oceanic factors, shows alternating patterns of El Niño - La Niña conditions
factors involved in ENSO index
atmospheric pressure, winds, SST, etc
TAO project
Tropical Atmosphere Ocean project
monitors equatorial Pacific with ca. 70 moored buoys for detection, understanding, and prediction of El Niño
southern oscillation
atmospheric component of El Niño; oscillation in surface air pressure between E/W Pac
what was the strongest ENSO in recorded history?
1997/98 and 2015/16 both had ONI = 2.3
Anoxic/hypoxic water examples
Saanich Inlet
Norther Gulf of Mexico
The Oregon Coast
St. Lawrence Estuary
Saanich Inlet
hypoxia develops periodically (naturally)
has been occurring for ca. 10,000yrs
hypoxia
reduced oxygen content of air or water detrimental to aerobic organisms
development of hypoxia
high OM production in surface - high vertical transport of OM to deep - high remineralization of OM by heterotrophic bacteria (consumes O2)
high productivity in SI
coastal upwelling brings dense nutrient rich water into Strait of Georgia
hypoxia in SI develops because
sill blocks oxygenated water from entering
SI renewal
eventually dense O2 water builds up, spills over sill, and re-supplies oxygen
Hypoxia in Gulf of Mexico caused by
excess N delivered by Mississippi (drains majority of country) + stratification of Gulf waters
Is Gulf of Mexico anoxia anthropogenic
yes - widespread fertilizer use = high nutrient = high PP = high OM flux..
Oregon coastal water
hypoxic events occurring since 2002
upwelling zone, strengthening from intensified winds, bringing deeper water with lower O2 to surface
St. Lawrence estuary
waters are a mixture of N/S waters, the mixture is changing to more of the warm water/low O2 source
St. Lawrence water sources
LCW - Labrador coastal water (cold and oxygenated)
NACW - North Atlantic Coastal Water (warm, low O2)
St. Lawrence water source ratio
1930: 72% LCW, 28% NACW
1985: 53% LCW, 47% NACW
Why is St. Lawrence changing
change in circulation patterns
low O2 is exacerbated by human use of fertilizer
example of naturally occurring hypoxia/anoxia
SI
Is Oregon coast hypoxia natural
no, considered anthropogenic because wind pattern changes are a result of climate change