Adaptations and Responses to Physiochemical Conditions:

1

• Adaptations and Responses to Physiochemical
  Conditions
• Hutchinson, 1957 Fundamental niche -
  hypervolume (gt3 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.

2

• 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

3

• 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)

4

• 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)

5

• 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)

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)

7

• 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 10C,
  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).

8

• Emerita talpoida - burrowing sand crabs common
  in surf zone on beaches - in the winter at 3C,
  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

9

• 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

10

• 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 -40C and some -70C
  shock for 24 hours

11

• 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

12

• 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)

13

• 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

14

• 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

15

• 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

16

• 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

17

• 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)

18

• 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)

19

• 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

20

• 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?

21

• 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.
  Blue-water high diversity plankton communities
  rarely exceed 5 trophic levels

22

• 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

23

• 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.

24

• 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
  between-habitat 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

25

• 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

26

• 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

27

• 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

28

• 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)

29

• 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

30

• 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

31

• 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)

32

• 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)

33

• 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.

34

• 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.

35

• 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

36

• 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)

37

• 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

38

• 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