319 Marine Ecology Flashcards
Ecology is the study of
- interactions between organisms
- interactions btw organisms and their environments
- how interactions affect distribution and abundance of organisms
Scales of ecology
Individuals/ population/ community structure
Ecosystem structure
Global biogeographic patterns
aspects of individual/ population/ community structure
species composition
species ranges
organism dispersion
aspects of ecosystem structure
food webs
energy flows
How environment affects ecosystem
aspects of global biogeographic patterns
Distribution patterns
Biodiversity patterns
Baseline data for climate models
the basis of marine ecology
observations observations observations
scientific deduction
use logic to build on a premise, generate a hypothesis, and make a prediction
Question:
broad interrogative sentence about a specific ecological phenomenon
Eg. why do mussel densities vary
Premise:
Our best ecological knowledge about the phenomenon
Eg. seastars eat mussels
Hypothesis:
A testable, mechanistic, assumption about the ecological phenomenon in question, based on sound premies.
Eg. Because seastars eat mussels, there will be fewer mussels where there are seastars
Prediction
How two variables relate to each other b/c of the mechanism described in the hypothesis
eg. seastar, mussel density will be negatively correlated; mussel density will increase when you remove seastars
A statistical test tells you
if differences btw controls and treatments are significantly different, i.e. not likely to be due to chance
Intertidal old definition
areas of the shore are covered by water during high tide, and uncovered during low tide
Intertidal new definition
where land meets the sea
the interface between terrestrial and marine ecosystems
why old intertidal definition is not as good
-some shore ecosystems don’t experience big tidal changes (high/low tides) but still have characteristic features
shore ecosystem organisms
up to 10 phyla (30 in the sea)
seaweeds, bivalves, gastropods
close relationship with some terrestrial organisms (gulls, raccoons, bears)
Environmental variables in the shore
- sediment size
- water emersion and submersion
- wave exposure
Sediment size
diameter at widest part of sediment grain
based on Wentworth scale of sediment size
boulders - clay grains
grain sizes, Wentworth scale
boulders >246mm cobbles 66-246 pebbles 4-64 granules 2-4 (gravel >2) coarse sand 0.5-2 medium sand 0.25-0.5 fine sand 0.06-0.25 silt 0.004-0.06 clay - less than 0.004
dominant type of organisms in rocky intertidal
epifauna, largely sessile
eg. barnacles, mussels
types of organisms based on sediment
epifauna (rocky environment)
infauna (sandy/muddy envt)
semi-infauna
semi-infauna example
sea pen - deeply rooted stalk, protrude above sediment
common in deep sea
sediment size determines
epifauna or infauna or no fauna
middle sizes not suitable for attachment or burrowing (cobbles)
biodiversity vs sediment size
negative parabola
high diversity/richness at small and large sed size
tides are
periodic movement of water across shore ecosystem caused by the gravitational pull of the Moon and Sun
tidal range
difference between low and high tide
chart datum
reference for measuring the tide, typically the lowest possible low tide (then tides are measured as height above CD)
what creates tides
rotation of moon = bulge on either side of earth – earth rotates through both bulges in one day, 2 bulges = 2 high tides
earths rotation
counterclockwise
W –> E
types of tides
diurnal
semidiurnal
mixed semidiurnal
diurnal
1 high tide, 1 low tide in a 24 hour cycle
majority of the worlds tides
90% are semidiurnal or mixed semidiurnal
VI tides
mixed semidiurnal
tide shift
0.75 hours/day (due to the moon rotating and moving the bulges)
what causes spring/neap tide cycles
earth/ sun/ moon alignment
moon has larger affect on tides but when M+S align = additive affects = spring tide
when M+S 90º apart, cancel each other out = neap tide
semidiurnal
2 high tides approximately same height; 2 low tides in a 24hr cycle,
high tide
area of Earth covered by bulge
spring tide
sun, moon, earth aligned on same side (new moon), or opposite side (full moon)
highest high tide
lowest low tide
locational effects on tidal variation
latitude
topography
local currents
coriolis force
latitude effect on tides
poles and tropics have lower tidal ranges than the mid latitudes
distance effect on tides
distance between E, M, S changes as they pass through their elliptical orbits
tides are measured relative
to a reference
eg. lowest neap tide, average tide
measuring tidal heights relative to mean
Height above chart datum (m) vs Time (h) Extreme high water of spring tide EHWS Mean high water of spring tides MHWS mean high water neap tide MHWN mean tide level MTL mean low water neap tide MLWN mean low water spring tide MLWS extreme low water spring ELWS
tide created gradient
ecocline
environmental wetness–dryness gradient
variable based on waves
low tide
area of Earth away from bulge
one tidal cycle
24 hours, 50 minutes
emersion
the process or state of emerging from or being out of water after being submerged; being uncovered during the low tide
neap tide
sun and moon perpendicular to each other
lowest high tide
highest low tide
least difference between high and low tide
submersion
Being underwater or going underwater; being covered in water during high tide
awash
being washed in seawater as it ebbs or flows during the tide; level with the surface of water, especially the sea, so that it just washes over
exposure
affected by waves
**NOT exposed to air, do not use ‘exposed’ when talking about emersion
problems associated with emersion-submersion cycles
temperature fluxes
desiccation
oxygen concentrations
currents that cause unattached items to move
Intertidal is defined by
wet –> dry gradient
tides may move the gradient up/down
why is O2 a problem in emersion-submersion cycles
many intertidal organisms deal with T fluxes and desiccation in a way that limits their oxygen
eg. shellfish close their shells
seawater and T fluctuations
T fluctuation milder in water – water has high heat capacity due to H bonds (require high E to break)
Intertidal T fluctuations
day vs night
seasonal cycles
latitudinal gradients
intertidal seasonal temperature fluctuations
- can be extreme
- timing of low/high tide varies across seasons (eg. right now low tide is night time)
poikilotherm
organism whose internal temperature varies considerably
Q_10 rule
Q_10 = 2 - 3
metabolic rate doubles or triples with every 10ºC increase in temperature
enzyme activity vs temperature
increasing parabola
medium T = optimal T for enzyme activity
optimal T varies between and even within species (different enzymes have diff. optimal T)
what happens to enzyme activity above optimal T
activity decreases because enzymes start to degrade / denature at high T’s
problem with higher metabolic rate
more E required to maintain basic metabolic function = less E for growth = lower “scope for growth”
scope for growth and temperature
decreases with increasing T b/c animal is spending all E surviving in high T
startegies for dealing with T fluctuations
behaviour
physiological/ biochemical
adaptation
behavioural strategies for dealing with T fluctuations
short-term behaviour changes to maintain internal T
physiological/ biochemical strategies for dealing with T fluctuations
short-term physiological responses
ex. produce heat-shock proteins or antifreeze molecules
adaptations for dealing with T fluctuations
morphological or physiological feature that evolve to minimize T fluctuation
-generational timescales
examples of behavioural T control strategies
hide in crevices
bivalves close shells
gastropods clamp down on the surface
form beds to trap moisture and buffer against T
shell adaptation to T fluctuations
light colour shells - reflect more sun
ridged shell - dissipate heat, trap moisture
snail study, Australia
find high-shore light-coloured snails stay cooler than exposed rock possibly due to shell colour
LD_50
temperature at which 50% cumulative mortality occurs
T tolerance, T optima vary based on
species
geographic range
enzyme activity at the T extremes
low T = enzyme activity too low to sustain life
high T = physiological failure due to protein damage
why are low T’s bad for enzyme activity
risk of tissue freezing
metabolic rate is too low– energy limited, growth / reproduction reduced
“supra-optimal”
above optimal temperature
at “supra-optimal” T’s
enzymes fail
protein denaturation
scope of growth reduced
capacity to produce heat shock proteins
appears to be threshold-responsive
may differ between regions (study found HS proteins in subtropic species)
heat shock protein, high T
at high enough T even the proteins fail
why would an organism have a higher LD_50
better able to deal with extreme heat
antifreeze proteins
glycoproteins
not nearly as well studied
found in polar regions
why are heat-shock / glyco proteins only short-term solutions
difficult to maintain
energetically demanding to produce
hierarchical T response
short term - physiological change
medium term - acclimation
long term - evolution and adaptation
may be additive, combined
why is desiccation a problem
marine organisms are mostly water;
can’t perform physiologic fn’s if dried up;
O2 availability problems
intertidal oxygen availability problems
can’t breathe ‘air’
breathing organs collapse when dry
strategies to conserve H2O deplete O2
strategies that minimize desiccation
a lot of the strategies that manage T clamp down close shell occur in beds aggregate in shaded crevices/ tide pools
overcoming desiccation
some organisms can rehydrate
intertidal seaweeds can lose 70-90% of internal moisture (probably specialized protein, not well understood)
strategies to maintain oxygen levels
specialized gills
specialized respiration
quiescent (inactive)
intertidal organisms, specialized gills
gills enclosed in thin-walled cavity to prevent drying (bivalves, crabs)
reduced gill size, vascularized mantle cavity = lung for aerial respiration (barnacles, high tide gastropods)
intertidal organisms, cutaneous respiration
reduced gill size, proliferation of blood vessels in skin
eg. intertidal fish
quiescence
inactivity reduces oxygen needs
strategies for dealing with wave action
aggregate in sheltered location
anchor to substrate
reduce profile
flexibility and elasticity
how intertidal organisms anchor to substrate
permanently - holdfast, abyssal thread, ‘glue’
temporarily - muscular goot, mucus-glue
intertidal organism shelter
crevices, tide pools, burrowing (if possible…)
dealing with wave action in the intertidal, reducing profile
small, squat, streamlined body - temporarily or permanent;
decrease physical damage, detachment
intertidal animals with permanently low profile
crustose algae barnacles limpets chitons abalone
intertidal animals with variable profile
anemone
crab
exhibit behavioural plasticity
why do intertidal organisms want to be flattened
reduce drage
dont ‘feel’ current as much
reduce dislodging
example of intertidal organisms exhibiting flexibility to deal with wave action
kelp - bend back and forth with the currents
wave action can have significant effects on community composition by
affecting sediment distribution
creating disturbance —> community succession
ecological niche
sum of organisms biotic + abiotic environment uses
eg. space, good, temperature range
not the same as habitat
most important determinant of where an organism can live in the shore environment
sediment size
rocky shore communities
diverse phyla, epifauna, many sessile, distinct donation patterns, primary and secondary space occupants
competition
an interaction btw individuals in which each is harmed by their shared use of a resource that limits their growth, survival, or reproduction
competition between individual of the same species
intraspecific competition
competition happens when
individuals of same species or diff species use same limiting resource
what is the relative importance of intraspecific competition vs interspecific competition
competition between species is relatively more important
types of competition
exploitative
interference competition
pre-emptive competition
exploitative competition
indirect competition
eg. plants depleting nutrients to the detriment of others
interference competition
two competitors physically interfere with each other
pre-emptive competition
get there first
rocky shore organisms display this competition by settling first
when is competition especially intense
when shared resource is rare / limiting
competition increases for
species and resource similarity
interspecific competition
competition between individuals of different species
most important resources that organisms compete for in marine environments
food
space
epi-fauna’s major requirement
space - surface to attach to
space is limiting
Connell’s barnacle experiment
Chthamalus stellatus vs Balanus balanoides
why did the two barnacles show zonation
Chthamalus stellatus
small barnacle, up to 8mm diameter
brown-greyish, smooth with oval operculum
Balanus balanoides
large barnacle, up to 22mm diameter
whitish in colour, white diamond-shaped operculum, deeply ridged plates, lower desiccation tolerance due to size
barnacle life cycle
nauplii I – nauplii II – nauplii III — nauplii iV – nauplii V — Nauplii VI – cyprid stage – settlement – metamorphosis – sessile adult
Connell’s observations
barnacle adults found in distinct bands
barnacle larvae found all over the intertidal (not in bands)
very narrow overlap zone - stark transition
zonation Connell’s barnacles show
Chthamalus found in upper tidal, away from water = more emersion time
Balanus found in lower intertidal, close to water = more submersion time
Connell’s question
why isn’t Chthamalus found in lower intertidal
Connell’s hypotheses
- space competition by Balanus limits Chthamalus in lower intertidal
- Chthamalus limited by submersion tolerance (not very good hypothesis)
- other possible reasons: predators, intraspecific competition
Connell’s experiments
- remove/ exclude Baluns from patches at different tide levels to see what happens to Cthamalus
- transplanted rocks w/ Cth. from upper–> lower to see if they survive
- also tested intraspecific competition and predators
how did Connell know that Balanus could not survive in the higher intertidal
he transplanted them from low –> high in a previous experiment
Connell’s results
- removal of Balanus from overlap increased Chth survival
- transplanting Chth lower had no effect on survival unless Balanus was also removed
Summary of Connell’s experiment
donation created by competition + tolerance
when env’t conditions stressful, community composition dominated by species that can survive there
what would be the outcome of Chthamalus/Balanus competition in a hot beach
at very high T Balanus may not survive due to its low desiccation tolerance, then Chth would dominate and take over low intertidal; Chth wins and zonation moves lower or doesn’t exist at all
what do Connell’s experiments demonstrate
- competition can structure the rocky shore community
- physical/bio conditions can alter the outcome of the competition
what does it mean that physical and biological conditions can alter the outcomes of competition
Context Specific!
eg. desiccation modified the outcome of barnacle competition
fundamental niche
set of resources where organism can theoretically survive
Chthamalus fundamental niche
all over intertidal
Balanus fundamental niche
only lower intertidal due to low desiccation tolerance
what would be the outcome of Chthamalus/Balanus competition at a moderate temperature beach
Balanus will outcompete Chth for cooler areas - crevices, low tide zone; baluns wins, Connell-type zonation
realized niche
the resources that the organism actually uses; may or may not be similar to fundamental niche
Chthamalus realized niche
≠ fundamental niche
able to utilize entire intertidal but not ‘allowed’ to b/c of Balanus
Balanus realized niche
= fundamental niche
Why does Balanus’ realized niche = fundamental niche but Chthamalus’ does not
Balanus is a superior competitor - dominant
how do animals co-exist in limiting habitats
competitive exclusion principle
what is the competitive exclusion principle
- competitors more likely to co-exist if they use resources in a different way
- competitors exclude each other when they use resources in exactly the same way
what would be the outcome of Chthamalus/Balanus competition at a cool beach
Balanus can tolerate being farther from water; Balanus wins, zonation moves higher or none at all if Balanus takes over
why can’t Balanus and Chthamalus co-exist
they use resources (space) the same way
when species use resources in the same they have the same
ecological niche
when a limiting resource is used in different ways it is called
resource partitioning
resource partitioning allows
multiple species to co-exist
types of predators in the rocky intertidal
borers, drillers, crushers, crackers, external digesters, browsers, sit and wait, mobile
types of grazers in rocky intertidal
sweepers, rakers
population
group of individuals of the same species that share a habitat and experience similar environmental conditions
population size
number/ biomass of individuals in a population (units = individuals, grams, etc. )
population density
number/biomass of individuals of a population in a given area (individuals / m2)
consumer effect on prey
depress density of prey by consuming them
profitability
energy per unit time an individual is aquiring
optimal foraging theory
profitability vs. prey size
profitability is highest at intermediate prey size
predators impact is largest on the size of prey that is most profitable (optimal)
why is profitability low for small and large prey sizes
too big = hard to capture/ crush/ kill
too small = too low of nutritional value for the work it takes
percent of prey population vs sizes
generally majority of population is small, less medium, big, less biggest
what happens to percent of prey population vs size when you add a predator
the population will go down but mostly only the medium sized individuals
why might optimal foraging theory exist
reproduction is also scaled to size – leaving large prey = more reproductive abilities = more prey
why are humans unnatural predators
we draw down the biggest prey
functional response curves
prey eaten per predator vs prey density
Type I = linear response, no restriction to how much predator eats
Type II = saturating curve, at some point predator can not keep up to prey
Type III = S-shape, predator must learn how to consume new prey source
most common type of functional response curve
Type II - saturating
when a consumer has an indirect effect on prey traits
inducible defense
barnacle inducible defense
Chthamalus in presence of Acanthina predator - bent form where operculum is ‘hidden’ from predator
If bent barnacles are protected from predators why don’t they all grow this way
bent barnacles of the same age have smaller shells and reproduce less; bent form may protect against predators but decreases population size and health
predator-induced changes, green crab and herbivorous snail
green crab – risk cue– suppress snail grazing – impact on algal community
predator risk impacts the ecosystem
consumer effects
consumptive or non-consumptive biomass abundance characteristics diversity
example of indirect effects
crab indirectly impacts algae via snail
sea otter indirectly impacts kelp via urchins
oystercatcher observations
- algal cover low where limpets are abundant
- limpets not found in oystercatcher feeding areas
- algal cover is high where oystercatchers feed
oystercatcher hypothesis
oystercatchers induce a trophic cascade by suppressing limpets which feed on algae
oystercatcher exclusion experiment
w/ cages exclude limpets
algae much higher in treatment than control
oystercatcher natural experiment
observe beaches where there are and aren’t oystercatchers
at beaches w/ oystercatchers limpets did not utilize full fundamental niche
human-oystercatcher observation
site w/ human activity have less oystercatchers and less algae
human-oystercatcher hypothesis
- human-educed trophic cascade = human affected sites have less oystercatchers – more limpets – less algae
- may be why human frequented beaches have so many limpets
trophic cascade
predator suppressed abundance or alters behavior of prey, releasing the next lower trophic level from predation
inducible defences can impact the community
predator induces bent form of barnacle – bent form not edible to predator – predator preys on mussel – mussel pop decreased – algae population increases due to freed up space
types of trophic cascades in rocky shore
density-mediated trophic cascade
trait-mediated trophic cascade
cost of inducible defense
lower growth
lower reproductive capacity
less fitness
density-mediated trophic cascade
caused by consumptive, lethal effects of predator on prey
trait-mediated trophic cascade
caused by non-consumptive, non-lethal effects of predator on prey
Enteromorpha
sea lettuce, Ulva
Littorina observations
- Littorina snail prefers feeding on soft algae, Ulva
- Littorina avoids feeding on tough algae, Chondrus
Littorina reverse transplant experiment
choose tide pools (some w/ some w/o snail) – remove snails from pools that had – add snails to pools that didn’t have – compare
Littorina results
control (w/ Littorina): chondrus dominant
snail introduced pool: originally dominated by Ulva, decreases in time, eventually replaced by Chondrus
snail removed: chondrus drops and Ulva rapidly becomes dominant
what does Littorina study tell us
even grazers can have large impacts on community and environment
competitive-dominant
out-compete other species for resources
mussels
Ulva
Littorina and diversity
Evenness, Richness both show hump-shaped response
- at intermediate Littorina density, more algae species allowed to exist because competitive-dominant grazed down
- intermediate-disturbance hypothesis
species that are important for structuring the community
abundance species
keystone species
bioengineers
foundation species
keystone species
impact on ecosystem is disproportionately large relative to abundance /biomass
keystone example
Pisaster
Pisaster study
monitor intertidal - remove Pisaster and monitor - after removal mussel pop. increases 2-> 95% of pop. – everything else wiped out
Disaster study conclusion
- Pisaster decreases mussel density
- mussels are competitive dominants
- Pisasters increase community diversity
- Pisaster is keystone
variations in Pisaster results in sheltered vs. wave exposed beach
context specific
- rough waves that remove mussels and pisaster = lower seastar effect b/c their pop is reduced and their preys pop is reduced
- could be that waves bring in more nutrients, or increase/reduce disease
dominant species
high abundant species; dominate the biomass; large effect on ecosystem b/c of large abundance
ecosystem engineer
habitat forming organisms; modify environment so much it affects other organisms
ecosystem engineer examples
beavers
termites
elephants
foundation species
a type of ecosystem engineer that impacts the environment in a way that effects other organisms
Parisites
can have an effect on the community structure too
-snails infected w/ trematodes grazed down algae more than community where snails were excluded, much less than community w/ healthy snails
foundation species
species the provide habitat for other species
- habitat-forming species
- ecosystem engineers
- supply the foundation of the ecosystem
foundation species examples
kelp mangroves corals seagrasses mussels
facilitation
ecological interaction where 1+ species benefit and no species are harmed
-foundation species facilitate new habitat
types of facilitation
habitat protection from stressful environmental conditions shelter from predators supply OM for food concentrate prey items
Stress Gradient Hypothesis predicts that facilitation by foundation species is most important
- when environment stress is high
- when environment conditions are benign
- therefore facilitation relative unimportant at med. environment stress (context specific)
why is facilitation important at low/high stress
high: buffer environmental stress
low: provide protection from predators (predators more active in low stress env’t)
mussel impacts
- foundation species that provide shelter for many organisms
- competitive dominants that displace many other species
- positive and negative effects, good if their your friend bad if their not
mussels and cockles observations
- mussels form reefs
- cockles are infuana burrowers
- cockles only found upstream from mussel bed (coastward)
- cockles absent from beaches without mussels
mussel, cockle premise
negative interaction btw mussels/ cockles prevented cockles from existing beyond mussel bed, but facilitated env’t that allows cockles to grow where mussels are
mussel, cockle conclusions
- mussels make downstream conditions unpleasant for cockles (seaward)
- mussels buffer landward area from waves - calm habitat for cockles
facilitating species impacts
can be positive and/or negative
foundation species impacts
facilitate other organisms/ communities
local or large spatial scale
positive and/or negative/competitive
why is physical disturbance important
dislodges epifauna - creates space in an environment where space is limiting
deterministic
predictable
succession
no life – pioneer stage – intermediate stage – climax stage
disturbance can set the system back a stage at any time or restart
pioneer species
move in quickly
grow quickly
eventually overtaken by next succession
climax stage
stable community
succession models
based on characteristics of pioneer species
facilitation model
tolerance model
inhibition model
facilitation succession
early colonists modify environment making it less suitable for early colonizers, and more suitable for late succession colonization and growth
sea palm disturbance example
- mussels, sea palms compete for space, mussels are competitive-dominants
- at wavy beach space is made for sea palms to grow
- at calm beach mussels are not removed and eventually take over
recruitment
number of individuals [seeds/ larva] that come in /year
barnacle, seaweed facilitation experiment
- limpets feed on algae
- barnacles facilitate algae by excluding limpets
stochastic
multi-variable dependent
tolerance succession
early colonizers make env’t less suitable for subsequent colonization but have little-no effect on late colonizers
how was the barnacle seaweed experiment conducted
planted synthetic barnacles – deterred limpet grazing
succession and patch size
- small storm - small patch opens - no succession – mussels re-take over
- large storm - large patch – other species have chance to colonize
- succession may depend on patch size and disturbance –context dependent
inhibition succession
early colonists modify env’t so it becomes less suitable for both early and late successional species – exclude subsequent colonization
algae inhibition succession
boulders commonly have grown seaweed – if patch opens up Ulva moves in – Ulva takes over
Ulva actively inhibits Gigartina brown algae
succession can lead to different types of stable communities
chitons, mixed community mediated by keystone, mussel dominated community
- small patch - refilled by mussels
- large patch - filled in by bacteria/algae mat
- mat may be grazed by chitons - stable
- mat may be replaced by seaweed, replaced by barnacles
what does mussel/ chiton / barnacle succession tell us
succession is stochastic - nature and size of disturbance dictates what happens
how does disturbance affect diversity
more disturbance = more diversity
too much disturbance = less diversity
intermediate disturbance hypothesis (hump)
ecological succession in rocky shore communities is not
deterministic
intermediate disturbance hypothesis and boulders, observations
small boulders = low # species
large boulders = low # species
med boulders = just right
intermediate disturbance hypothesis and boulders, premise
small boulders = large level of disturbance, waves disrupt them, destroy/ remove organisms
large boulders = immobile, waves do not move them, space not opened up, colonized by competitive-dominants
med boulders = movement in large storms, space opened up sometimes = higher species richness
intermediate disturbance hypothesis
low disturbance - competitive dom. take over
very high disturbance - few species grow
mid disturbance - competitive-dom + patches of successional species
supply side ecology
delivery of larvae: processes that must occur, types of larvae, currents, settlement features, metamorphosis
bipartite life cycle of marine organisms
benthic adults – reproduction – pelagic larvae – grow, develop, disperse – settle – benthic juvenile – adult
reproduction strategies in shore organisms
different sexes or hermaphrodites internal or external fertilization feeding or non-feeding larvae metamorphosis present or absent huge variation
feeding larvae
planktotrophic
which type of larvae can likely travel further
probably feeding (planktotrophic)
downside to feeding larvae
have to feed
lower survival if resources too low
survival curves
number of survivors vs age/time
Type I - chair shape, high survival of juveniles, extreme mortality of adults
Type II - linear, steady decline in # survivors, constant chance of dying
Type III - slide shape, thousands of larvae, few survive, most individuals die young
Most marine organisms use which reproductive strategy
Type III (large # of young)
larval survival determined by
availability of food
predators
recruitment bottleneck
larval survival
which larvae type is more limited by predators and resources
depends! context specific!
depends on currents - how far larvae are travelling
feeding larvae may have extra stress - more vulnerable
non-feeding larvae
lecithotrophic (have yolk sac)
spring phytoplankton bloom
important to larvae food availability
marine organisms reproduce seasonally to match the bloom
if bloom is at wrong time larvae in trouble
why is there a spring bloom
more sun - longer days, angle
more nutrients - winter mixing
more heat - stratification, organisms not mixed out of surface layer
why does bloom end by summer
run out of nutrients
too much stratification - nutrients not mixed back up
mismatch between food availability and larvae
no bloom / late bloom / different species bloom can cause reproductive failure and population collapse
nauplii release in barnacles
found to be correlated with phytoplankton concentration
- Semibalanus moult and larval release correlated w/ food intake
- Urchins, mussels triggered by extracellular metabolite
consequences of planktonic larvae for benthic populations
dispersal
settlement
recruitment
dispersal
how far individuals are carried by currents
affects gene movement
settlement
describes when pelagic larvae settle onto benthos
i.e. when they arrive on the shore
recruitment
describes when a new individual joins the population
why is it difficult to study dispersal and settlement
larvae are tiny - difficult to observe, ID, tag, etc.
concentrations in water column are small
pelagic tools
pelagic tools
not that easy to design 1. sticky tile 2. funnel submerged in water at high tide, larvae settle in to top, can pour out 3. pot scrubber - good settling surface beaches patchy, need lots
important factors for dispersal
currents - how far do they get? where?
larval life stage - planktotrophic, lecithotrophic
how much fuel they have
how currents affect rocky shore communities
influence local population dynamics
influence genetic connectivity btw populations, create biogeographic patterns
influence ecological interactions on the rocky shore
example of currents impact genetic connectivity
like the hydrothermal vent dispersal study - where is the genetic material being provided by/to
example of currents impacting local population dynamics
density of population
role of currents and topography
open beach - no restriction, lots of ocean exchange, currents important, lot’s of mixing
isolated bay - limited ocean exchange
topography and flow exchange, open beach vs isolated bay
closed - exchange w/ ocean may dilute larvae and food concentrations
open - exchange w/ ocean may be only source of larvae, food
estuary flushing
settlement rate vs flushing time = linear increasing
fast flushing rate, high flow = low phytoplankton, low suspension feeder growth, low recruitment
how to study population dispersal and connectivity
tagging, chemical indicators
couple oceanographic modelling + observations
genetic anlaysis
tagging and chemical indicators in marine studies
not very useful
larvae too small to tag
chemical indicators too blunt
coupling oceanographic models with observations
see if densities or genetic relatedness matches patterns expected
marine population dispersal, genetic analysis
measure genetic info – use statistical model to compare sequences among population - compare patterns w/ currents – see if genetic differentiation patterns match currents
Point Conception, California
2 opposing currents: north of point current is s, south of point current is N
test genetics - find different genetic structures on two sides of point
rocky shore populations are all
metapopulations
a series of connected subpopulations
population sources or sinks
important for conservation science
rocky shore subpopulations connected via
dispersal
offshore / onshore currents
results of Ekman transport
important for delivering larva and phytoplankton
gyre circulation
clockwise in NH
dominant current on W NA
N –> S
Coriolis effect
deflection of currents due to Earths rotation
in N hemisphere water is deflected to the right of direction of movement
Ekman spiral
- surface water movement by wind drags deeper layers of water below
- each layer moves by friction from layer above and moves slower, movement stops ~100m
- water is deflected by Coriolis effect- each successive layer moves more to the right, creating a spiral effect
- net movement is 90º to wind direction
Ekman transport
net movement of water results in upwelling or downwelling
Ekman transport in W NA
- current dominantly N–> S
- coriolis deflects water to the right
- net movement away from shore
- water from deeper rises to replace it = upwelling
our current system
we are pretty much right between Alaska current and California current, sometimes it moves up/down
importance of upwelling
deliver new larvae
stimulates PP - food for suspension feeders, food for planktotrophic larvae
strength, direction of upwelling
change: between seasons, within seasons, between yeas, day-to-day
seasonal upwelling variability
VI upwelling strongest May-July
downwelling strongest in winter
within season upwelling variability
upwelling strength increases w/ wind speed
interannual upwelling variability
ENSO
-upwelling stronger in La Niña years
when california current is strong
upwelling
when california current is strong
upwelling
impact of strong upwelling
high nutrients but they are drawn away from coast
impact of strong downwelling
low nutrients
intermittent upwelling theory
intermittent upwelling (switch between upwelling and downwelling) is best – nutrients are supplied and aren’t carried away
intermittent upwelling hypotheses tested
- if ecological processes have unimodal rlt’shp w/ upwelling strength
- if ecological processes have monotonic rlt’shp w/ upwelling intermittency
intermittent upwelling study
measure Chl a, barnacle mussel settlement and recruitment, barnacle/mussel growth rates, competition, predation
ecological subsidies vs upwelling index
Chl a (phytoplankton) vs upwelling
recruitment (larvae) vs upwelling
both show hump-shaped response
when alaska current is strong
downwelling
intermittent upwelling hypothesis conclusions
- data support that ecological processes will have a unimodal relationship w/ upwelling strength
- only some data support the ecological process - upwelling strength monotonic relationship (most processes did not increase linearly with increased intermittency)
why do only some data support the ecological processes increasing with intermittency relationship
- over intermittent’ upwelling - not enough time to respond to nutrients
- differences in tides - the over intermittent sites were in California where tides are mixed semi-diurnal, might give predators longer stretches to feed – high predator activity might obscure results
important in determining community structure
competition (Connell)
predation (Paine’s seastars)
ecological interaction vs environmental stress, competition
competition is high in relative importance when environmental stress is low
ecological interaction vs environmental stress, predation
predation is high in relative importance when environmental stress is low
biological forces are important when
physical conditions are benign
when physical conditions are stressful
environmental conditions are more important
requires more benign conditions
predation, predators are more sensitive to environmental stress
Menge-Sutherland model
relative importance of ecological interaction vs environmental stress
predation high at low envt stress
environmental high at high envt stress
competition high in the middle
hypotheses to describe zonation
settlement
physical factors
biological factors
settlement and zonation
supply side ecology
do organisms decide where to settle
do organisms grow where they settle
physical factors and zonation
desiccation tolerance
biological factors and zonation
grazing
predation
competition
do organisms simply grow where their larvae settle
not always
some organisms move after they settle
some larvae move towards adults of their species
propagules
new settlers
do physical factors affect zonation
yes, desiccation especially
but not the only important distribution factor
critical tide level hypothesis
- old, discredited
- seaweed zonation differences due to amount of time species spend under water, physical factors determine upper and lower distribution limit
- doesn’t explain animal distributions
what really describes zonation
a mix of everything
- tolerance to abiotic conditions sets upper limit
- biotic/ ecological interactions set lower limit
updated Menge-Sutherland model
3D model
x= environmental stress
y = relative importance of ecol.
z = recruitment
relative importance vs environmental stress, competition under high supply side
high supply = more competitors = competition more important
curves shift right, competition important under higher environmental stress than before
relative importance vs environmental stress, competition under low supply side
low recruitment = lower range of competition = curves shift left
competition curve is thinner, shorter, or non-existent
why is competition low at high levels of predation
predators decrease density of competitors per unit area
relative importance vs environmental stress, predation, competition, environment, under low supply side
predation, competition both shift left or are non existent
if not organisms then no ecological interactions
Menge-Sutherland conclusions
- allows us to predict relative importance of env-org and org-org interactions
- allows us to predict community composition/ zonation
why would upwelling be important to rocky shore communities in california current system
- delivers new larvae to community
- stimulates PP (suspension feeder, larvae food)
- strength, direction of upwelling changes
sediment size
measured as: diameter, or log base 2 of diameter
plotting sediment size
cumulative % vs size
settling velocity vs size
cumulative weight graph
- plot from small to large size sediment
- plot as cumulative %
- determine Q25, Q50, Q75
- Q50 is median
stoke’s law
subject sed sample to current of known velocity, determine how much of sample is carried by that velocity and how much settles
-faster current = more E
sediment sorting
% of sample vs size
- well sorted = clear median, low variety
- poorly sorted = large variety of sizes
sorting, S =
Q25 / Q75
small S
well sorted (close to 1)
interstitial water
betweens sediment particles organic rich (POM, DOM)
porosity
proportion of sediment that is ‘empty’
porosity is measured as
volume of water needed to saturate sediment
what type of sediments are more porous
finer
well sorted
why is poorly sorted sediment less porous
smaller grains fill the interstitial space, variable grain sizes fit together better
permeability
rate of flow of water through sediments
what type of sediment has higher permeability
well sorted (more spaces) coarser
less permeable sediments are
waterlogged - water takes longer to flow through
penetrability
how easy it is to penetrate (burrow) in the sediment
penetrability depends on
sed size
porosity
sediments that appear solid but behave like fluid if they experience pressure
thixotrophic
eg. quicksand
sediments harden when they experience pressure
dilatant sediments
which types of sediments (in regards to penetrability) are easier to burrow into
thixotrophic (fluid-like)
other sediment characteristics
mineralogy
shape
mineralogy
quartz fragments - terrigenous
carbonates - biogenic
seiment shape
roundness (ragged edges not good for burrowing)
sediment and oxygen
- O2 rich in surface from o-a exchange, PP
- O2 used up at depth, respiration
O2 rich sed
lighter
O2 poor seds are dark/black
how is oxygen used up in surface sediment
heterotrophic bacteria - respiration - degrade OM
how is oxygen used up in deep sediment
anaerobic bacteria use sulphate for respiration and produce hydrogen sulfide
SO4 – H2S (black)
boundary between oxidation and reduction in sediments
RPD - redox potential discontinuity
microorganism zonation in sediment
High O2 surface: mixed photosynthetic organisms
Anoxic layer 1: fermenting bacteria
Anoxic layer 2: sulfate reducing bacteria
Anoxic layer 3: methanogenic bacteria
Oxic sediment microorganisms
benthic diatoms
cyanobacteria
heterotrophic bacteria
fermenting bacteria
- produce alcohol and fatty acids
- test for fermenting bacteria by testing for fatty acids
sulfate reducing bacteria
SO4 – H2s
methanogenic bacteria
when sulfate runs out
produce CH4
muddy sediment characteristics
more water logged more OM more bacterial productivity, and therefore anoxia shallower O2 layer shallower RDP darker, smellier
types of organic matter
allochthonous
autochthonous
examples of particulate organic matter
filamentous diatoms bacterial mats detritus (seaweed, seagrass) wood feces
importance of OM
fuels bacterial respiration
source of food for infauna
allochthonous
sediment that originated at a distance from its present position
how to measure OM in sediment
- asking - weigh sed, cook @ 500ºC, burn off OM
- use weight of small size fractions as proxy
variability in sediment
where they come from
how they are transported
sediment transport
wind
waves
tides
stream, creeks, rivers
wavelength
crest to crest or trough to trough
wave height
crest to trough
wave frequency
number of wave crests passing point A per second
autochthonous
sediment thatformed in its present position
wave period
time required to pass from one crest to the next
a wave ‘feels’ the bottom when
water is shallower than 1/2 wavelength
what happens when wave ‘feels’ bottom
slows, wavelength shortens, period remains unchanged, crests become peaked - E packed into less space, wave approaches critical ratio
critical ratio (wave)
1:7 wave heigh : wave length
wave breaks
systems of sediment transport
longshore current system
circulation cell system
longshore current
- waves hit beach obliquely
- 2 directions of sediment movement
- swash (oblique) and backwash (straight back out)
- direction of longshore drift is down the beach
circulation cell system
- current hits beach dead on
- energy bifurcates
- water concentrates on way back out = rip current
waves move sediment if
force from water flow > than threshold force required to move sediment
-bigger waves move bigger seds
if grains are too big for the waves
they will sediment out
swash vs backwash energy
swash velocity > backwash
swash carries coarser sediments
backwash carries fine sediments out
areas of fast currents =
lots of big rocks and boulders
areas of slow currents =
lots of muds and clays
tidal currents, sediments
tidal currents transport sediments
range determines strength of tide and E to transport sediment
tidal strength
flow tides typically stronger than ebb tides
tidal currents vary in strength within tidal cycle, between seasons, etc
exposed beach and sediment
bigger waves – larger sediment – waves prevent fine sed from accumulating
sheltered beach and sediment
finer sediments accumulate due to lower wave strength – mudflats
organisms in sandy beaches / mudflats
microbes - algae, cyanobacteria, other bacteria
infauna
mobile predators - crabs, shore birds, etc
in fauna are classified by
size
macro, meio, micro
photosynthesizes at the sediment surface
algae, cyanobacteria, heterotrophic bacteria
bloom cycles like pelagic primary producers
form mats at the surface
microfauna
less than 63µm
often interstitial - on or between sediment grains
meiofauna
63 - 500µm (pass through 0.5 mm screen)
can be interstitial
indicator organisms
provide a wide range of ecosystem function
macrofauna
> 500µm (0.5mm)
larger than interstitial spaces
microfauna examples
ciliates
tardigrades
cyanobacteria
diatoms
infauna convergence
meiofauna
extremely abundant, span many taxa and all have same body structure
endobenthic
meiofauna-sized organisms that move by displacing particles (burrowing)
meiofauna phyla in a bucket of sand
up to 22
rain forests have ca 15
infauna burrowing strategies
deep burrowers
shallow/fast burrowers
meiofauna examples
ostracod
copepod
annelid
nematode
deep burrowers
larger (eg. geoducks have big feet, can burrow deep)
develop heavy shell
long siphon
mesobenthic
meiofaunal-sized organisms that live and move within the interstitial space
shallow/ fast burrowers
annelid worms, small clams, crustaceans
limbs modified for digging
more delicate organisms burrow closer to surface
bivalve, polychaete burrowing
hydrostatic skeleton - extend - anchor into sediment - dig/displace sediment - extend
macrofauna examples
gastropod
polychaete
decapod
bivalve
mole crab burrowing
shovel-like legs - burrow into sand - mechanically displace sediment
burrowing strategy, sediment type
dry, coarse sediment – clam shoots water to liquefy sand before burrowing
teddy sed - rich in water and OM = sticky, bivalves/ polychaetes use proboscis to crack mud
infauna tubes
- discrete, solid structures formed by secrete material + sediment
- eg. parchment worms build parchment tubes and circulate water/food with parapodia
permanent burrows
not as solid as tubes
break apart when sampled
eg. lugworm (Arenicola spp.)
subsurface burrows
formed by animals that move continually, feeding as they go
e.g. clams
infauna morphology
all have worm-like body plans (increased SA, absorption)
tentacle-like structures for sediment attachment
how infauna deal with low O2 in sediments
siphons create currents through their burrows move/leave reduce activity to reduce O2 consumption more efficient O2 binding pigments
oxybios
live in shallow seds
high O2 requirements
poor tolerance for sulphide
live in deeper sediments
can tolerate low oxygen
can tolerate high sulfide
contain symbiotic sulphur reducing bacteria
thiobios
ingest sediments to obtain organic matter for food
deposit feeders
filter organic particles suspended in the water column with gills
suspension feeders
deposit feeder characteristics
digest OM as they move
expel digested sediment, unwanted particles as pseudofeces
deposit feeder example
lugworm
what is in sediment
water
POM
DOM
inorganic particle
POM composed of
- living microorganisms (bacteria, fungi, benthic algae)
- dead particulate OM (detritus)
major questions for deposit feeders
where does the nutrition come from? (detritus or bacteria)
how do they separate organic from inorganic?
detritus in the beach ecosystem
fragmentation - physical break-down
leaching - loss of pigment
microbial colonization and decay
why is leaching of detritus important for deposit feeding
pigments can act as deterrent for some microbes
microbial stripping hypothesis
in fauna are not just eating detritus but also the microbes that cause detritus to decay and rot
microbial stripping hypothesis, premise
- increases N content of detritus
- makes detritus easier to digest
C:N
common measure of nutrition
C generally from cellulose, low nutrition
N from proteins, higher nutrition
low ratio = higher quality
not all detritus has same nutritional value
kelp, algae = high N, P, and fatty acid
seagrass = low N, P, fatty acids; high cellulose
amount of detritus on a beach
highly variable based on:
- local production (eg. seagrass break up from waves)
- tidal activity (e.g. dead plankton brought in by tide)
- rivers (OM or sewage in streams, lakes, rivers)
deposit feeder selection
selection can occur before or after ingestion
thiobios
live in deeper sediments
can tolerate low oxygen
can tolerate high sulfide
contain symbiotic sulphur reducing bacteria
deposit feeder, before feeding selection
some sift through particles and reject them if too big or not suitable
eg. fiddler crab
deposit feeder, post feeding particle selection
defecate non-nutritious or too large particles (sand) = pseudofeces
eg. polychaetes
OM is
sticky
well-attached to inorganic particulates
possibly difficult to separate from inorganics
how do organisms separate OM from inorganics
- specialized enzymes to separate them
- secrete surfactants to separate them
surfactants
detergent-like molecules
wash the OM off
surface deposit feeding
echinoderms: roam the surface and ingest particles
polychaetes: some lay tentacles to comb through seds., tentacles may carry food back to mouth or transport particles via ciliary action
eg. spaghetti worm
types of suspension feeding
active - create current to bring particles in
eg. parchment worm, feather duster worm, barnacle
passive - rely on currents to bring particles
appendages for suspension feeding
mole crab uses comb-like antennae
bivalves use siphons
worms may use palps, tentacles
why are suspension feeders selective
otherwise would fill up w/ non-food materials
suspension feeder particle selection
- polychaetes use cilia-like structures to detect and reject particles
- bivalves use gills, palp to reject inorganic / toxic particles
palp
folded, ciliated organ
particle selection study in Pacific Oyster
- follow particles through oysters gut w/ endoscope
- find that [algal particles] increases in basal tract relative to what goes in
- gill sensory mechanism diverts OM
switching feeding modes
D. excentricus sand dollar is facultative suspension feeder depending on current - context dependent
- high tides: incline body, ‘stand up’
- low tides: flat, deposit feed
bioturbation
-local-scale biological disturbance which changes the environment in a way that influences other organisms
burrowing
- type of bioturbation
- increase physical complexity of ecosystem
burrowing impact on sediment
- changes size distribution, stirring and sorting
- oxygenation of surrounding sediment
- RDP depression
- changes to nutrient and microbe distribution, activity
sediment mixing experiment
- put inert particles at surface of burrow to see how much is brought down into burrow
- increased concentration of beads at depth in burrow
- therefore ‘sediment’ from surface is brought to depth
burrow colonization
- not just organisms making them
- potential habitat for commensal organisms
example of burrow co-habitation
goby fish, crabs in worm burrow
photoautotroph bioturbation
diatoms, cyanobacteria
- secret mucilage (extracellular polymer glue) that binds them together w/ sediments - makes sediment sticky, prevents erosion
- oxygenate sediment
Bioturbation characteristics
- increases habitat structure
- reworks sediment (changes size distribution)
- changes sediment chemistry (oxygen incursion, bio-irrigation)
- increase microbial activity (oxygen changes, microbial gardening)
- changes habitat (provide new habitat for some organisms, prevent other organisms from colonizing)
bottom-up forces
environmental factors
eg. desiccation, oxygen, temperature
top-down forces
predators, competition
e.g. starfish in rocky intertidal
Most important factors structuring rocky shores
- environmental stress
- competition
- predation
- disturbance
- supply-side ecology
what are rocky shore factors not as well known in sandy shores
experiments harder
- animals ‘invisible’
- animals move (most intertidal are sessile)
- patchiness
- have to disturb habitat to view animals (can’t observe natural habitat)
soft shore experiments
more difficult
- cages have to be designed to encompass 3 dimensions
- organisms are mobile and burrowing
- predators
important environmental factors
temperatures disturbance (waves) oxygen dessication emersion/submersion
submersion and emersion, soft sediment shore
- desiccation not as important as rocky shore, some water
- water too low for suspension feeding, not enough water
- biological stress from emersion not physical stress
oxygen, soft sediment shore
- only really an issue in low tides, anoxic water events
- organisms ok as long as ‘connected’ to the water (unless water is anoxic)
temperature, soft sediment shore
sediment are a good buffer from extreme weather
does biological stress from emersion always affect soft shore organisms
no, clam surfing - changes distance from MTL to stay in water
soft shore sediment zonation experiment
- move clams higher up in shore - growth affected
- clams normally found higher suffered less
- infauna appear to be adapted to different levels of desiccation (low-level specialists, high-level specialists)
competition in the sandy shore
- more 3D space, segregate vertically
- space competition (interference competition) not a factor
- nutrient competition? (possible, depends)
to demonstrate there is nutrient competition
have to demonstrate food is limiting
-do org’s respond to increase in food
change in health based on increase/ decrease of resource
exploitative competition
food limitations in soft shore sediments
- food resources patchy and seasonal
- changing concentrations of OM in sediment likely impact deposit feeders
- suspension feeders not likely to experience long-term limitation
soft shore sediment patchiness
food supply is patchy – communities are patchy
-Ulva patches = snail patches = behaviour response to patchiness
competitive exclusion principle
species that use limiting resources identically cannot coexist
competition among similar species might cause
character displacement
character displacement
- evolutionary process
- separation of morphological characteristics such as size, and therefore resource exploitation
example of character displacement in soft shore
-2 deposit feeding snails
-same size when at separate beaches
-different sizes when at same beach
(possibly extraneous variables, type of habitat, lagoon vs open beach)
predation in soft sediment
- prey hidden (burrow)
- defense trade-off
- secretions
defense trade-off bivalves
bivalves with thin shells burrow deeper
soft sediment anti-predation secretions
some polychaetes - secrete bromide-containing aromatic compounds - deterrent
