Lecture 12- Heterogeneity the ocean- BIO OCE

where does the ocean lean towards in terms of heterogeneity and homogeny

heterogeneous, towards patchiness

3 types of patchiness

1. uniform

2. random

3. patchy

chi square

tells us if the area is patchy and at what scale

chi square equation

χ² = SS/mean

sum of squares

(individual value)²/mean

what is chi square important for

important to know how predator/prey works

index of dispersion formula

D = σ² /μ

μ

mean

σ

std

D = 0

constant distribution

D< 1

under-dispersed: even, regular

D= 1

poisson distribution, random

D> 1

over-dispersed: patchy, clumpy

morisita’s index of dispersion equation

Id = n((sumχ²)-N/(N(N-1))

Id

index of dispersion

n

number of plots

N

total number of individuals counted

χ²

square of indivduals per plot (then summed over all plots)

Id=0

perfectly uniform

Id = 1

random

Id = n

maximally aggregated

example of domain independent methods

Lloyd index of mean crowning

what is the Lloyd index of mean crowding based on

perspective of the individual (number-1(you))

mstar formula

mstar = sum χi/N

mstar meaning

average number of other individuals per plot

examples of causes of patchiness produced by the physics of fluid motion

turbulence, horizontal displacement and shear, internal waves, langmuir circulation and non-langmuir streak formation

what do internal waves need to be corrected for in causes of patchiness

corrected for moored instruments

langmuir circulation

shallow, slow, counter-rotating surface water vortices aligned nearly parallel (0° to 20°) to a steady wind

examples of causes of patchiness by biological factors

growth, bloom formation, grazing causing holes, swarming/schools of fish, vertical migration

langmuir vortices

particles that aggregate according to their buoyancy or vertical migration patterns

threshold of wind speed of langmuir vortices

3m/s

what happens to spacing between cells in langmuir vortices

get larger with wind speed

langmuir circulation pattern

wind pushing away with rotating counter vortices in middle of water column

what rides the langmuir circulations and why

scyphozoan for predation on zooplankton

3 types of vertical migration

1. annual/interannual vertical

2. diel vertical

3. tidal vertical

life cycle of calanus pacificus

eggs > nauplii< copepod

6 copepod stages

CI -CVI

when do copepods breed

breed as an adult in spring, cycle before in winter they develop into their late copepod stage

what happens during NI-CV

development from march to july

what happens to copepods during CV

migrate 300m

what happens when copepods mature into CVI

reproduce in jan-feb

when do copepod eggs hatch

prior spring bloom when they float to the surface

general pattern of diel vertical migration

descent during the day and ascend to the surface at night

what is the largest migration in terms of biomass/time on earth

diel vertical migration

what are the hypotheses as to why diel vertical migration occurs

1. predator abundance to avoid visual predators

2. energy balance to save metabolic fuel in colder waters

3. foraging strategy to exploitate food patches

why does tidal vertical migration occur

position maintenance of estuarine organisms

diapause

programmed delay of development because of unfavorable conditions

examples of why diapause may occur

cold temperature, reduced food, drought

life cycle of calanus hyperboreus

3-5 yearlife cycle

two types of diel vertical migration

normal and reverse

normal diel migration

abundance during night at surface and go back down during night

where do some zooplankton hide during the day in diel cycles

suboxic zone

reverse vertical migration cycle

go deep during the night and come up during the day

why do zooplankton do reverse vertical migration

if their predators are usually at depths during the day, you adapt to have the opposite

what does reverse diel vertical migration depend on

whether mortality is dominated by predator population of visual predators or nocturnally hunting predators

result of having predators such as nocturnally hunting predators such as euphasusids, chaeotognath and large copepods

reverser vertical migration

what predators may result in reverser vertical migration

euphausids, chaetognaths, large copepods

predators that may result in normal vertical migration

visual predators such as fish

what determines how something may do vertical migration

predation

why may everyone NOT migrate vertically

is nutritional status, if you are full, you wont migrate

ebb tide

the period when the sea level falls and water flows away from the shore toward the ocean

ebb tide in estuary meaning

salt wedge moving upstream

tidal vertical migration

plankton maintaining horizontal position in estuary by vertical positioning with tidal cycle

behavioral aggregation

schooling or shoaling in fish

why do fish school

predator defense

what is an example of small scale patchiness

thin layers

thin layers

spatially and temporally coherent horizontal layers of organisms of not more than 5m thickness, often as thin as a few cm

crirtical scales

scales at which variability of physical and biologically processes matter

what do idealized profiles of the water column ignore

highly patchy plankton distributions

where is a famous study site for thin layers

washington, orca islands

example of a device used to do thin layer profiling

free falling CTD rosette that you attach buoys to so it float free

example of how thin layers form with alexandrium catanella

they accumulate due to:

• higher cell number per chain due to slower cell division in turbulent conditions bc chain length affects motility

• turbulent affects growth so they move to an area less turbulent (thin layer)

where do alexandrium catanella accumulate

mixed layer where there is minimum shear and minimum turbulence

what does the thin layer usually follow

pycnocline

where do copepods and most other zooplankton aggregate

density discontinuities (pycnocline)

what was found from rotifers feeding pn isochrysis

sometimes copepods go up and down in water column to hit the thin layers of phytoplankton and leave to not get eaten by fish

in the SF estuary why is light limiting

turbidity

what is the source of vertical heterogeneity in estuaries

runaway stratification

runaway stratification

a self-reinforcing feedback loop where density differences between ocean layers become so large that vertical mixing nearly stops

why should we care about processes at critical scales in oceans

we get correct estimates flux of nutrients through the food chain and gives information on toxic phytoplankton

how do processes at critical scales give us info about toxic phytoplankton

toxic phytos may exclusively occur in thin layers and may escape detection with conventional sampling

what does it mean that toxic phytoplankton have much stronger accumulation of toxins that if homogeneously distributed

toxic phytoplankton do not spread out evenly like dye in a glass of water; instead, they clump together into dense pockets, thin layers, or surface scums

possible sources of variability

hydrogel or organic matter continuum (blending of POM and DOM)

phycosphere

halo microzone around phytoplankton colonized by TEP, contains bacterial communities

particle plume

a moving, turbulent stream or cloud of solid particles or droplets suspended in a fluid

particle plume (DOM wake)

the invisible, comet-like chemical trails of dissolved nutrients left behind in the water as organic debris sinks toward the seafloor

copepod scent trail

male following female pheromone trail for mating

what are other ways copepods detect females

hydrodynamic signature

the cube in a drop of seawater

artwork illustrates the hidden microscopic world inside a single drop of seawater, showing how marine microbes experience the ocean as a complex, structured landscape of chemical gradients rather than a uniform liquid

how are large scale patchiness observed

mesoscale eddies and gulf stream warm core rings

what are mesoscale eddies strong enough to do

transport deep sea sediments