Transcript No Slide Title

Adaptations and Responses to Physiochemical
Conditions:
• Hutchinson, 1957: Fundamental niche - hypervolume
(>3 axes) within which a species can survive or
reproduce: 2 bivalve species (see graph)
• Realized niche - actually occupied by the species
• If niche is a lot smaller than the fundamental niche genetic adaptations might be lost
• Thus, we would expect a loss of physiological
adaptation to varying temperatures when a species has
lived in a constant environment over time.
Time Scales:
• Ecological
time vs. evolutionary time
• Ecological time - individuals in a population
must respond to environmental change while
restrained by genetic makeup
• Evolutionary time - time scale in which
changes in genetic structure of species through
time permit adaptations to change
• Acclimatization
- changes in tolerance with
seasonal environmental change
• If collect mussels from field and place in lab
conditions that are different (i.e., temperature)
the bivalves may survive - in doing so there may
be a shift (i.e., oxygen consumption rate)
• Such a compensatory process is known as
acclimation (see graphs)
Adaptive Response:
EA = EG + ER + EM
• A = energy assimilation/time
• G = growth
• R = reproduction
• M = respiration
S = EG + ER - EM : when surplus energy is
available there is a positive (S) - E can be
partitioned between somatic growth and gametes
(see Fig. 2-3)
• Lethality
is more commonly measured than scope for
growth
• Experimental population kept at standard lab
conditions permitting acclimation
• Lethal temperature can be determined by (a) slow
decline or rise in temperature, or (b) rapid transfer of
the lab-acclimated individual to a constant extreme
temperature
• LD50 - lethal dose required to kill 50% of the
experimental population after a specific shock time
(24 hr common period) is determined
• LD50 - common to vary parameters (i.e.,Temp.) in
steps, then interpolate LD50 (see Fig. 2-6)
Temperature:
• Probably the most pervasively important and
best-studied environmental factor affecting
marine organisms
• Large latitudinal gradient because many of our
continents have N-S trending coasts
• Major shifts in marine biota at these latitudinal
shifts (i.e., Cape Cod, MA, Cape Hatteras, NC,
Point Conception, CA)
• Tropical
intertidal invertebrates have lower body
temperatures than would be predicted from an
inanimate object
• Color of shells - temperature affects the rate of
metabolic processes – example later
• Oxygen consumption - with an increase of 10°C, the
corresponding change in metabolic rate as measured
by O2 consumption is called the Q10 - for most
poikilotherms, Q10 is 2-3. Q10 will decrease as the
upper lethal limit is approached. Homeotherms
regulate body temp. (marine mammals).
• Emerita
talpoida - burrowing sand crabs
common in surf zone on beaches - in the winter
at 3°C, consume oxygen at a rate of 4x greater
than animals collected in summer that are tested
at the same temp. – results from acclimation.
Latitudinal gradients - oysters
• Crassostrea virginica and sea-squirt Ciona
intestinalis, from different regions, have
different breeding temperatures - termed
physiological races
• Eurythermal-
wide in temp. tolerance
•Stenothermal – narrow range in temp. tolerance
•Heat Death - protein denaturation - thermal
deactivation of enzymes; lower solubility of
oxygen at higher temperatures might limit the
individual capacity for efficient respiration
• In algae, rate of photosynthesis typically
decreases
Cold Temperatures:
• In tropical fishes, cold can depress the
respiratory system and lead to anoxia and death
• Freezing in marine environments presents
problems - fish larvae and forams - found
encased in pack ice in Antarctic
• Body fluids freeze - intertidal fleshy algae can
survive extended periods of -40°C and some 70°C shock for 24 hours
• Salts
depress freezing point - similarly, freezing
point depressed in organismal fluids
• In Labrador temperatures reach freezing points
of seawater and cellular fluids of many
invertebrates and fishes
• Shallow-water fish Trematomus counteracts
freezing by synthesizing glycoproteins - which
depress freezing point
• Temperature
also affects growth and reproduction; in
bivalves, members of the same species have been
found to grow more slowly, but survive to older age
and reach larger size in higher latitudes
• Pisaster ochraceus - gamete synthesis is correlated
with temperature
• Temperature can also affect morphology - ribs on
mussel shells - Mytilus edulis occurs in 2 color
morphs, blue and light brown stripes. It has a genetic
basis - blue mussels absorb more heat and have higher
body temperatures than light brown mussels (blue
morph inc. from VA to ME)
Salinity:
• Diffusion / Osmosis - see table 2-1
• Organisms actively regulate ionic concentration
• Scyphozoans and Ctenophores actively eliminate
sulfate, replace it with a lighter ion - lowering overall
specific gravity
• Some organisms are osmoconformers (or
poikilosmotic) – others are osmoregulators
• Porphyra tenera in dilute seawater take up water and
elongate over time
• Bivalve
mollusks - do not osmoregulate extracellular
fluids but do regulate the osmotic character of
intracellular fluids
• They achieve constant volume by regulating the
concentration of dissolved free amino acids;
concentration of amino acids change with salinity
gradient (Bayne et al., 1976)
• Lysozomes have been implicated at site of protein
degradation and amino acid release
• Anguilla rostrata reproduce in Sargasso Sea and
juveniles return to salt marshes; they mature and live
in freshwater - Catadromous
• Fundulis
leteroclitus can live in fresh and seawater
• Salmonids born in freshwater, migrate to sea, return
to spawn
• Teleosts are hypoosmotic, subject to water loss in
seawater, and salts must actually be eliminated to
maintain lower salt content
• As Teleosts drink to maintain water balance - salts
are also taken in - gills maintain salt balance by
excreting salts (see Fig.)
• Elasmobranchs (sharks and rays) can also actively
eliminate ions such as Na; high concentration of urea
to maintain osmotic balance - similar to amino acids
for bivalve mollusks
Oxygen:
• Controlled by diffusion and biological processes;
oxygen increases with decrease in temperature
• Cold deep water - high or low oxygen?
• Photosynthetic plankton in shallow waters can
supersaturate the water with oxygen
• Oxygen consumption - ml/g-1/hr-1
• ml oxygen cons. = kWb
• b = fitted exponent
• W = body weight
• k = constant
• Many
poikilotherms have b less than 1.0,
indicating that metabolic rate fails to increase
linearly with increased body weight
• Several reasons:
1) surf./vol. ratio
2) increase in non-respiring mass (skeleton,
fat) in organisms with respiratory apparatus
• Active species consume more oxygen (see Fig.
2-9)
• At
low tide animals (infaunal) are subjected to
oxygen depletion
• The end products of anaerobic metabolism (alanine
and succinic acid) build up in tissues. In mollusks, a
portion of the succinic acid is neutralized by
dissolution of CaCO3. In winter the inner layer of the
shell of Guekenzia demissa is pitted due to a
dissolution process. Low temp. causes decrease in
transport rates of oxygen to cell.
• Blood pigments (Hb) - Hemocyanin - copper
pigment - Cephalopods (Limulus)
• More pigments in animals that live in environment
with little or no oxygen - M. californianus consumes
oxygen in air at comparable raters to its respiration in
water (Bayne et al., 1976)
Waves and Currents - Table 2-3
Light:
• Ascophyllum nodosum & Fucus vesiculosus photosynthetic rate relatively constant over a
wide range of light regimes
• Acclimatization - changes in plant pigments
• chlorophyll-b, phycobiliproteins - dim light
• carotenoids - high light adaptation
Marine Biotic Diversity
• The # of species in a region is the end product
of a long evolutionary process of speciation
events balanced by extinction events
• There are less than 10 species of benthic
forams in the northeastern U.S. shallow subtidal
regions, but more than 80 living on the abyssal
plain of the N. Atlantic. WHY? What
evolutionary and ecological processes caused
this?
Good Fossil Record Needed:
• 2 types of among-species change seem to accompany
the evolution of diverse communities
1) Variety can be increased through the
multiplication of trophic levels. This is a limited
process because energy is lost through trophic
levels (Slobodkin ca. 10% efficiency)
Inshore low-diversity plankton communities
usually have about 3 trophic levels or more. Bluewater high diversity plankton communities rarely
exceed 5 trophic levels
2) Increase in ecological specialization with
increased diversity. Given that resources are
limiting, the evolution and migration of species
into communities should be accompanied by
greater levels of specialization.
• Is there a limit to how diverse a community
can get?
• Theoretically, the number of species cannot
exceed the number of resources
• Eveness-
Rare species are especially important
in disturbed communities in the process of
recovery. This will come out in this measure unlike H’ which largely ignores common or rare
species
•*Newly disturbed environments have low
species richness. High dominance and hence
low H’ and J’. With further succession, species
richness increases, but dominance may be high
due to competitive superiority of a few species.
H’ generally increases in later successional
stages.
• In
any comparative study of diversity, a
homogeneous habitat with few resources or
microhabitats will support fewer species than one with
more
• A comparison of diversities between 2 habitats of
different structural complexity would be a betweenhabitat comparison
• A within-habitat approach is preferable in comparing
diversity between different regions (i.e. muddy
bottoms of the deep sea and muddy bottoms of
shallow-water lagoons)
• Still problems - other variables change within
Patterns and Gradients of Species Diversity:
• Latitudinal - most well-known gradient is an
increase of S from high to low latitudes in
continental-shelf and planktonic organisms - see
Fig. 5-2
• This pattern has been recorded in detail for
bivalve mollusks, gastropods, plankton,
forams, and many terrestrial groups
• Spight 1977 compared species richness to
habitat diversity at differing latitudes
Prosobranch Gastropod Diversity
• Washington vs. Costa Rica beaches
• Spight found that the tropical site contained
more habitat specialists. Substrate diversity was
greater in tropics - not due to competing species
Between Ocean Basins:
• The Pacific Ocean has more species than the
Atlantic. This fact has been documented for
hermatypic corals, bivalves, fishes and probably
most other groups
• Table 5-1 - Polychaetes are the exception;
climate more variable on the east coast
Continental Shelf - Deep-Sea Gradient:
• Sanders 1968 - samples from mud bottoms
ranging from shelf to deep-sea depths
• Diversity of polychaetes and bivalves increased
dramatically with water depth
• Rex 1973 - similar pattern for benthic forams and
gastropods
• Diversity decreased again from continental rise to
the abyssal plain - decrease in food supply (will
discuss Sanders later)
Inshore - Offshore Plankton Community:
• Temperate zone planktonic communities near
shores (bays) support fewer species than offshore
assemblages. Fewer trophic levels inshore
• Similar pattern can be seen from species-poor
upwelling areas (i.e. Humbolt current off Peru)
relative to high diversity blue-water plankton
communities at the same latitudes
•Estuary versus open marine habitats: In estuaries, decrease in
diversity often accompanied by expansion of the species that
penetrate brackish water -relaxation of competiton - salinity
gradient as well
Area:
• Habitat area - (MacArthur & Wilson 1967) -
• Islands - at a given distance from the mainland
- larger islands support more species than
smaller islands
• Also holds for species on continents (Flessa
1975)
• Area complicates matters when comparing the
larger Pacific coral reef province with that of the
smaller Caribbean province
Models Explaining Diversity Gradients:
• Stability-Time Hypothesis - Community in
physically stable and geologically ancient
environment accumulates more species than
variable environments
• The age of an environment is thought to
determine the extent to which more specialized
species have been added
• This hypothesis finds support in the high species
richness of large, stable, and ancient lakes (i.e.,Rift
valley lakes of east Africa; Lake Baikal, Siberia)
• Unpredictable
environments are thought to be
more important in depressing diversity than
predictable variable environments
• Sanders 1968 - fluctuating-environment, low
diversity communities physically controlled and
the constant-environment, high diversity
communities biologically accommodated
•(not really true)
• The
time aspect of the “hypothesis” is different
to consider since it is based on ancient lakes
(east Africa and Lake Baikal) and large young
lakes such as the Great Lakes and Great Slave
Lake of Canada. These lakes are only 11,000
years old or less - making them too young to
expect major evolutionary events
• Furthermore, there is no evidence that the
deep-sea is older than shelf or intertidal zones.
•Shallow water platforms have been
present in varying abundance through
geologic time (Valentine, 1973)
Abyssal faunas, if anything, are younger
than shelf faunas – so the stability aspect
seems to be more important.
Resource Stability:
• This explanation emphasizes the fluctuation of
primary production and its role in selecting for
generalized and specialized species (Valentine
1973, 1999)
Predation:
• Cropping of prey species prevents competitive
displacement and allows the coexistence of more
species
• Dayton & Hessler, 1972 - cropping increases
diversity in deep-sea
• As
diversity increases - the # of trophic levels
increases - resulting in a greater incidence of
predatory depression of competition in the lower
trophic levels
• Competition Hypothesis difficult to test
• No current evidence that predation is more
important quantitatively in tropics than in
temperate zone
• However, it is true that trophic gastropods seem
morphologically superior in resisting predation
(Vermeij, 1977, 1998)
• Jackson
1977 presents compelling evidence
that the co-occurring array of nearly 300 species
of invertebrates living under colonies (cryptic
species) of the foliaceous coral Agaricia do not
experience much predation at all and occupy
nearly 100% of the available space
Environmental Stress:
• An extreme environment can be successfully
colonized by fewer species than a less extreme
environment
• Although some species may inhabit hot springs
(bacteria) most phyla have not evolved
representatives capable of such an invasion
• Other Stress Zones: Highly polluted
environments, estuaries, intertidal areas scoured
by ice, hypersaline lagoons