Midterm 2 Flashcards
1
Q
what is ecology
A
- study of biotic and abiotic interactions between organisms and their environment
- typically involves measuring distribution and abundance in various environments and what resources are available to organisms
2
Q
interactions between organisms
A
- +- Territoriality
- +- Predation
- Parasitism
- ++ Mutualism
- 0 Commensalism
3
Q
Teritoriality (– or +-)
A
- Maintenance of home range and defense against intruders
- Individuals maintain territories to:
– protect a feeding area
– breeding site
– a specific nest site
4
Q
Predation (+-)
A
- Mobile and non-mobile predators
- search for prey using chemical, mechanical and/or visual stimuli
5
Q
optimal foraging theory
A
- Diet breadth - rule: food scarce, increase breadth (or when food is plentiful - focus on nutritious items)
- Time spent in a patch - rule: greater the distance between patches, spend more time in a given patch
- Size selection - maximize energy intake, usually leads to selection for
intermediate size
6
Q
predator avoidance
A
- Characteristics that increase resistance to predation are SELECTED for
- Examples of adaptation are:
– crypsis (camouflage)
– deceit
– escape responses - Mimicry
- Müllerian (not known in marine organisms) and Batesian
- mechanical defense
- inducible defense
- chemical defence
- Visual cues
7
Q
chemical defense
A
- Toxic compounds
- Conspicuous colour plus chemical defense
- Many very poisonous marine organisms are brightly coloured (aposematic colouration)
- These defenses (chemical and mechanical) vary with latitude, habitat and oceanic basin
- Organisms without such defences may hide or grow fast (e.g. sponges, seaweeds) to enhance survival
8
Q
Parasitism (+-)
A
- Parasites evolve to reduce damage to host
- Commonly involve complex life cycles with more than one host
- Parasites may invade specific tissues, such as the reproductive tissue of the host
9
Q
commensalism (0+)
A
- Commensal crab and fish live in this burrow of Urechis caupo
10
Q
Mutualism (++)
A
- Coral + zooxanthellae
- cleaner fish + predators
11
Q
Effects of disease
A
- Destruction of important species, e.g., shellfish disease attacks
- Removal of ecologically important species (example: removal of key grazer)
- Interaction with other factors such as climate change & pollution (? Sea star wasting disease)
12
Q
ecological processes
A
- Competition
- Predation
- Parasitism
- Disturbance
- Facilitation
- Larval dispersal (unique to ocean)
- Larval settlement
13
Q
populations level
A
- Group of individuals that are affected by the same overall environment and are unconnected with other populations of the same species.
- Changes in populations come from survival, birth, death, immigration and emigration
- Marine populations are
dynamic - Survival of adults is a major factor in populations
- Many marine species produce hundreds of thousands of eggs per
female - Reproduction is seasonal and corresponds to food and environmental factors
- Population size and extinction are closely related - low density of adult individuals can result in population extinction
- Many marine species spawn eggs & sperm in the water if density is low the likelihood of sperm fertilizing an egg is low
14
Q
modes of populations change
A
- exponential growth
- logistic growth
- random change
15
Q
allee effect
A
Correlation between population size, density & fitness
16
Q
community level
A
- Communities are organized around the habitat or around foundational species
- Species that determine structure -
foundation species, interacting species - Processes: Competition, predation,
disturbance, disease, parasitism, facilitation - Environmental influences: temperature, salinity, light, water energy, depth, nutrient regime
17
Q
foundation species
A
- These organisms play a role in facilitation which is a + + relationship. - E.g. retention of water by seaweeds at low tides for small organisms to remain moist
18
Q
larval access
A
- Many marine organisms have planktonic larvae that can disperse across large areas.
- Suitable substrate upon which these larvae can settle is a limiting factor in marine communities.
- There are many factors that can result in good and bad recruitment and this can result in affecting adult population sizes
19
Q
competition: limiting resources
A
- Renewable - e.g., copepods exploiting diatom population
- Non-renewable - space on a rock exploited by long-lived sessile species
20
Q
outcomes of competition
A
- Competitive exclusion - one species outcompetes another for a resource
- eg. extinction
- Coexistence - two species exploit different resources, some process allows two species to exploit same resource without displacement
- eg. “niche shift” - character displacement - evolution of shift in morphology or behaviour
21
Q
heterogeneity in habitat
A
- Niche structure - predictable partitioning by co-existing species of a habitat into subhabitats
- Extensive coexistence with apparent resource limitation
22
Q
evidence for interspecific competition
A
- Field experiments - remove hypothetical competitor (e.g., barnacles)
- Laboratory experiments - e.g., growth experiments with one and multispecies combinations -disadvantage is lack of field conditions
- Displacement in nature- e.g., invasive species, increase of resource exploitation in estuaries.
- Problem - other factors could be at work.
- Contiguity of resource use - e.g., “adjacent niches”
- could arise by evolutionary change
23
Q
predation and herbivory
A
- Predation or Herbivory can suppress the competitive success of superior species over inferior species, especially if predator prefers competitively superior prey
- E.g. Piaster ochraceus & Mytilus californianus or sea urchins, sea otters & seaweeds (keystone species), or removing urchins results in dominance of a fast growing seaweed
- Seasonal influx of predators can decimate some local communities
- E.g. Migratory seabirds in the intertidal zone
24
Q
disturbance
A
- Usually refers to physical change in environment that causes mortality or affects reproduction (storm, ice scour).
- Habitat wide (storms, ice, oil spill)
- Localized in patches (horseshoe crabs, logs)
- Suppresses effect of competition (Intermediate disturbance-predation effect)
25
Q
levels of disturbance or predation
A
- Low levels of disturbance or predation: Competitive dominant species takes over
- Intermediate levels: Promotes coexistence, more species present
- High levels: most individuals removed, reduces total number of species
26
Q
parasitism and disease
A
- Parasites can result in the reduction of growth and reproduction in the host. Recall the complex life histories of parasites - marine parasites often have several possible hosts
- Population declines have been attributed to disease that results in massive mortality (E.g. Pacific sea star wasting, Toxoplasma gondii & sea otters)
- Diseases are not well understood in the marine environment.
- All of these can affect the dynamics in a community
27
Q
facilitation
A
- Positive interaction between species where some species facilitate the other’s presence
- E.g. seaweeds retaining moisture or providing substratum
- Foundation species
28
Q
succession
A
- Predictable order of appearance and dominance of species, usually following a disturbance.
- Examples of disturbance and colonization:
- volcanism–> coral colonization; deep-sea invertebrate colonization
- Deposition of sand –> colonization by burrowers
29
Q
factors in succession
A
- Initial colonists - properties: not specialized, high reproductive rate, dispersal-oriented
- Later colonists - better competitors that displace earlier species?
- Prevention of invasion - good competitor? Good at resisting predation? Environment altered, which prevents further colonists from invading?
- Is there a climax community? Assemblage of competitively superior species? Resistant to predators? Evidence for such communities? Dominance?
30
Q
direct and indirect effects of ecological interactions
A
- Direct effects: Predator consumes prey, prey population decreases
- Indirect effects: Sea otter consumes urchins; as a consequence, seaweed prey of urchins increases in population size
- Density mediated indirect effect: Density at one feeding level increases, which reduces prey of another species, and, in turn results in an increase of the prey of the second species
- Trait-mediated indirect effect: Presence of a predator, causes prey to be active less and feed less on their own prey, so prey of second species increase in abundance, even though the second species did not decline (their feeding activity declined).
31
Q
ecosystem level
A
- Ecosystem: group of interdependent biological communities and abiotic factors in a single geographic area that are strongly interactive.
- Nearly all ecosystems have primary producers (mainly photosynthetic), secondary producers (herbivores), and carnivores. Material escaping this cycle is material to be decomposed in the saprophytic cycle.
- Food webs may be controlled by top-down processes where top predators have strong effects or bottom-up processes where changes in primary production drive changes in food web.
- Strong top-down linkages or bottom-up linkages generate a tropic cascade through the food web
32
Q
productivity
A
- Biomass (standing crop) – mass of organisms in a defined area or volume
- Primary productivity – amount of living material produced in photosynthesis per unit area per unit time
- Secondary productivity – primary consumers per unit area per unit time
- Tertiary productivity – consumers of herbivores.
- Example: energy transfer to an adult herring
- However, marine communities do not exist as simple food chains
33
Q
keystone species
A
- Some organisms have strong effects on competitive interactions and on entire ecosystems
- Examples, otters & killer whales on urchins, seastars and mussels.
- These are top-down effects
- Bottom-up effects, e.g. phytoplankton can affect the number of apex preditors (e.g. algae, sea ice, krill, fish, whales)
34
Q
marine biogeography
A
- No marine species occurs worldwide
- Two factors limit distribution:
– habitat-physiology limitations
– barriers to dispersal - The marine assemblages are known as provinces
- Currents and temperature changes affect differences
- Present distribution due to evolutionary history - vicariance and dispersal
35
Q
how do organisms respond to changes in the marine environment
A
- Seasonal and daily changes - cyclic
- Rapid environmental changes (flooding, rain)
- Organisms must have receptors to sense the change in order to respond
– Receptors-antennae, tentacles, protein systems
– Transfer systems - nervous connections to muscle systems, endocrine systems - Responses can be adaptive (e.g. organisms in a tide pool) and maximize fitness
36
Q
types of responses
A
- Behavioural
- Physiological (cellular changes at large systemic level)
- Biochemical (changes of concentrations of enzymes, ions within specific cell types)
- Gene regulation
- Metabolic rate (total rate of energy used by an organism, usually oxygen consumption) is typically used to get an overall impression of a response to a change in the environment
37
Q
what is acclimation
A
response followed by new equilibrium
38
Q
what is regulation
A
maintenance of constancy despite environmental change
39
Q
what is conformance
A
internal state changes to match external environmental change
40
Q
scope for growth
A
- The difference between energy assimilated and the cost of metabolism
- Measure of energy reserves: Scope for growth minus excess energy beyond that needed for maintenance
- Surplus energy may be divided between somatic growth & reproduction
- More food, scope of growth will increase
41
Q
measure of physiological condition
A
- Can be measured by scope that the organism has for activities e.g. swimming
- Organisms need to have reserves and oxygen systems for quick muscular responses
- Mortality rate can also measure effect of changes in the environment (e.g. temperature)
- LD50 - where 50% of the population dies (24h)
42
Q
temperature
A
- Temperature variation is common in marine environment:
– Latitudinal temperature gradient, regional differences
– Seasonal temperature change
– Short term changes (e.g., weather changes, tidal changes) - Temperature regulation:
- Homeotherms - regulate body temperature, usually higher than ambient
- Poikilotherms - do not regulate body temperature
- Species evolve differences in temperature tolerance
- Populations living along a latitudinal gradient might evolve local physiological races, with different temperature responses
- Freezing - winter & high latitudes
- Some fish have glycoproteins and glycopeptides, which function as antifreeze and bind to incipient ice crystals to prevent further growth
43
Q
poikilotherms
A
- Have the advantage of no cost of keeping temperature constant and high, but at the price of metabolic efficiency
- Heat gain - problem for poikilotherms in intertidal zone at low tide or tidal pools on a hot day
– Circulation of body fluids - brings heat to surface of body so it can be dissipated
– Evaporation - also allows heat loss to avoid overheating - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature
44
Q
homeotherms
A
- Homeotherms - advantage of constancy of cellular chemical reactions, disadvantage of heat loss
- Heat loss - problem for homeotherms who maintain high body temperatures
- Insulation - used by many vertebrates (blubber in whales, feathers in birds)
- Countercurrent heat exchange - circulating venous and arterial blood in opposite directions while vessels are in contact to reduce heat loss
- Marine mammals typically have a higher metabolic rate compared to terrestrial mammals of similar size
45
Q
heat
A
- Heat Shock - has effects on physiological integration of biochemical reactions in cells, can denature proteins that cannot function at high temperature
– heat shock proteins - are formed during heat stress, which forestall unfolding of protein 3D structure
– ubiquitin - low molecular weight protein
46
Q
seasonal changes in temperature
A
- Seasonal extremes of temperature affect both activity and reproduction
- Effects are different at northern and southern limits of geographic range
- Seasonal changes in timing and amount of egg and sperm production and release are highly correlated to temperature
47
Q
salinity
A
- Variation of salinity: estuaries, tide pools, intertidal zone
- Many marine groups intolerant of salinity change (low salinity)
- Populations in open ocean often less tolerant of salinity change: e.g., pelagic planktonic organisms
- Regulation of vertebrates of ionic
concentrations to very narrow variation, other groups show more variation and response to external change
48
Q
diffusion and osmosis
A
- Diffusion - problem of regulation of ion concentration
- Osmosis - problem of regulation of
cell volume - Osmosis - movement of pure water across a membrane permeable to water, owing to difference in total dissolved material on either side of membrane
- Example of osmosis problem -animal with a certain cellular salt content is placed in water with lower salinity: water will enter animal if it is permeable - cell volume will increase, creating stress
- Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations
- Problem - diffusion makes it difficult to regulate concentration of physiologically important ions such as calcium, sodium, potassium
- Most marine organisms have ionic concentrations of cell constituents similar to seawater
49
Q
ion regulation
A
- Done by many species, but best by crustacea (e.g., crabs), vertebrates
- Accomplished when isolation of body possible (e.g., crab carapace) so exchange and regulation localized
- Poorly accomplished by species with poor isolation (e.g., echinoderms, sea anemones)
50
Q
cell volume regulation
A
- Osmolytes: organic substitute for inorganic ions - allows regulation of cell volume and maintenance of inorganic ion concentrations
- Free amino acids used by many invertebrates, bacteria, hagfishes. Use uncharged amino acids that have little effect on protein function (e.g.,
glycine, alanine, taurine) - Urea used by sharks, coelocanths
- Glycerol, mannitol, sucrose used by seaweeds, unicellular algae
51
Q
oxygen
A
- Oxygen - synthesis of ATP; energy source in cells
- Some habitats are low on oxygen
- Low tide for many intertidal animals
- Within sediment: often anoxic water
- Oxygen minimum layers in water column: where organic matter accumulates at some depths
- Seasonal oxygen changes: hypoxic zones, “dead zones”
- Oxygen consumption increases with increasing body mass, but weight specific oxygen consumption rate declines with increasing total
body mass - Oxygen consumption increases with activity
- Nearly all animals are obligate aerobes, but many animals have a mix of metabolic pathways with and without use of oxygen
- Anaerobic pathways:
- Vertebrates and some invertebrates use glycolysis - breakdown product is lactic acid, which accumulates in muscle tissue
- Many invertebrates have alanine and succinic acid as anaerobic breakdown products
- Oxygen uptake mechanisms:
- diffusion
- feathery gills
- Larger animals have circulatory systems and oxygen-carrying blood
pigments
52
Q
blood binding pigments
A
- Blood pigments: substances that greatly increase blood capacity for transporting oxygen
- Haemocyanin - copper-containing protein, found in molluscs, arthropods
- Haemoerythrin - iron-containing protein, always in cells, found in sipunculids, some polychaetes, priapulids, brachiopods
- Chlorocruorin - iron-containing protein, found in some polychaetes
- Haemoglobin - protein unit (globin) and iron-bearing unit (heme), found in many phyla (Myoglobin is part of this family of proteins)
- Blood pigments can serve as reservoirs for animals living in low oxygen environments
53
Q
oxygen association- dissassociation
A
- Bohr effect: Hb ability to hold oxygen decreases with decreasing pH
- pH is less near capillaries that are starved for oxygen, owing to presence of CO2 released from cells (respiring); Hb releases oxygen, which
diffuses into cells
54
Q
low oxygen environments
A
- Low tide (not immersed in seawater)
- Oxygen minimum layer
- Climate change:
–Thermal stratification
–Loss of movement of layers of water to depth
–Hypoxic zones
–Decrease in O2 over 50 years (solubility decreases as temperature increases)
55
Q
light
A
- Many animals detect light with aid of a simple layer of sensory cells, but many species have complex eyes with focusing mechanisms (and can see colour)
- Allows detection of prey, predators
- Aids in navigation
- Behaviour (including mating)
- Photosynthetic organisms can also sense light and have phototropic responses - some have eye spots that sense light as well as the direction of light
56
Q
Vision
A
- Relies on pigments that absorb light
- Rhodopsins
- Vertebrates have rods & cones
- Retina focuses the light
- Colour vision is widespread among
vertebrates and invertebrates in the marine environment
57
Q
Bioluminescence
A
- Bioluminescence - light manufactured by organisms, using specialized light organs, sometimes with the aid of symbiotic bioluminescent bacteria
- Functions to confuse predators
- Perhaps other as yet undiscovered
functions
58
Q
life in sea water
A
- Life in seawater is a selective force on marine organisms
- Primary effects - direct results of properties of seawater
- Secondary effects - secondary impacts of properties of seawater
59
Q
properties of fluids
A
- The properties of water are different from air
- Density (greek letter rho - ρ)
–seawater is more dense than freshwater - Dynamic viscosity (greek letter mu - μ)
–molecular “stickiness” between layers of a fluid
–the more “sticky” the more energy that is required to move within - Kinematic viscosity (greek letter nu - ν)
–“gooeyness” under gravity (how it falls) - Two forces compete in fluids: viscous forces and inertial forces - Reynolds number (Re) is an estimate of the relative importance of each of these
60
Q
reynolds number
A
- When Re is less than 1000 then viscous forces are dominant
- If Re is much greater than 1000 then inertial forces predominate
- Objects exist under very different conditions in the same seawater, depending on their size and velocity
- Re=Vlρ/μ
- Low temperature: viscosity dominates
- High temperature: inertia dominates
– Temperature range of 5-15°C - kinematic viscosity decreases 45%! - Energetically less costly to swim at higher temperature
61
Q
movement of water
A
- If Re is high = flow is turbulent
- If Re is low = flow is laminar
- Shear can result in microturbulence
62
Q
principle of continuity
A
- Assume fluid is incompressible and moving through a pipe
- What comes in must go out!
- Velocity of fluid through pipe is inversely proportional to cross section of pipe
- Allows organisms to regulate water flow
63
Q
sponge pumping
A
- Sponges consist of networks of chambers, lined with cells called choanocytes
- Velocity of exit current can be 1-2 cm/s (10,000- 20,000 μm per sec)
- But, velocity generated by choanocytes is 50 μm per sec. How do they generate such a high exit
velocity? - Cross-section of flagellated chambers adds up to several thousands of times the cross sectional area of the exit canal
64
Q
water movement and organisms
A
- Bernoulli’s principle: pressure varies inversely with fluid velocity (if total energy is constant)
- If diameter of a pipe decreases then velocity will increase but pressure will decrease
- Can provide lift or create a current
65
Q
pressure current
A
Water moving past an object
creates drag
- At high Reynolds number, the pressure difference up- and downstream explains the pressure drag. Streamlining and placing the long axis of a structure parallel to the flow will both reduce pressure drag
- At low Reynolds number, the interaction of the surface with the flow creates skin friction
- Fast and continually swimming fish (e.g. sharks) are very streamlined to reduce drag, many also have adaptations such as arrangement of scales to reduce minor irregularities as well as having slime on their skin
66
Q
sessile forms- how to reduce drag
A
- Problem: You are attached to the bottom and sticking into the current
- Drag tends to push you down stream - you might snap!
- Examples : Seaweeds, corals
- Solutions:
–Flexibility - bend over in current
–Grow into current
–Strengthen body
67
Q
reproduction
A
the replication of individuals
68
Q
dispersal
A
the spread of offspring from one area to another
69
Q
migration
A
directed movement between areas and populations
70
Q
sex
A
- Sex is complex
- Sex is inefficient
- Sex is costly
- Is sex necessary?
–Sex means genetic recombination - Crossing over & segregation
- Matings between non-related individuals
- Genetic recombination is believed to be why sexual reproduction is so successful
- Sex produces genetically diverse offspring
71
Q
trends in reproduction
A
- Many organisms can reproduce asexually & sexually
- Rarely is sex wholly absent
- Exclusively sexual reproduction is also rare (mammals)
- Asexual predominates in small organisms
- Sexual predominates in large organisms
- Sexual selection can result in traits that are useful in attracting a mate or competing for a mate
72
Q
sexual selection
A
- Selection for extreme forms that breed more successfully
- major claw of fiddler crabs,
- Can involve selection for display coloration, enhanced combat structures
- Female choice often involved; selection for fit males (good genes hypothesis)
- Intrasexual selection: within a sex
- Intersexual selection: between males & females
73
Q
sexuality
A
- Separate sexes: gonochoristic
- Hermaphroditism: individual can have male or female function, simultaneously or sequentially, during sexual maturity
74
Q
Sequential hermaphroditism (protandry)
A
- first male then female
- Eggs costly in terms of resources, so more offspring produced when individual functions as female when large
- Male function does not produce great increases in offspring when it gets larger
- Therefore, there is a threshold size when female function begets more offspring; smaller individuals do better as males
- larger females with smaller males produce more offspring
75
Q
Sequential hermaphroditism (protogyny)
A
- first female, then male
- Male function must result in more offspring when male is older and larger
- Important when aggression is important in mating success, e.g., some fishes where males fight to maintain group of female mates
76
Q
male polymorphism
A
- Males may occur as aggressive fighting morphs, or less aggressive morphs
- Observed in a number of groups, e.g., some fishes and some amphipod or isopod crustaceans
- Determination of morphs can be environmental, genetic
- Less aggressive morphs can obtain mates by “sneaky” tactics, which are often successful
77
Q
reproductive success
A
- Percent investment in reproduction - reproductive effort
- Age of first reproduction (generation time)
- Predictability of reproductive success
- Juvenile versus adult mortality rate
78
Q
factors in fertilization
A
- Planktonic sperm (and eggs in many cases): problem of timing, specificity
- Direct sperm transfer (spermatophores, copulation): problem of finding mates (e.g., barnacles, timing of reproductive cycle)
- Planktonic sperm:
– Specialized binding/fertilization proteins in sperm and receptors in eggs (bindin in sea urchin sperm, lysin in abalone sperm)
– Sperm attractors in eggs
– Binding proteins are species specific, proteins with high rates of evolution
79
Q
epidemic spawning
A
- known in mussels, stimulus of one spawner causes other individuals to shed gametes
80
Q
mass spawning
A
- known in coral species, many species spawn on single nights
81
Q
timing of spawning
A
- (also production of spores by seaweeds) at times of quiet water (slack high or low tide) to maximize fertilization rates
82
Q
life history theory
A
- Tactics that maximize population growth
- Evolutionary “tactics”: variation in reproductive effort, age of reproduction, whether to reproduce more than once
- Presume that earlier investment in reproduction reduces resources available to invest in later growth and survival
- Examples:
– Strong variability in success of reproduction: reproduce more than once
– High adult mortality: earlier age of first reproduction, perhaps reproduce only once
– Low adult mortality: later age of first reproduction, reproduce more than once
83
Q
parental care
A
- Parental care is non- existant in many marine animal species
- but there are instance where females or males provide care.
- Courtship can be related to parental care
84
Q
asexual reproduction
A
- Clone - descendants are genetically
identical - Colonial - individuals are genetically
identical, comprise a module; each module may have arisen from a sexually formed zygote - Fragmentation is also a form of asexual reproduction seen in many seaweeds and some corals
85
Q
migration
A
- Dispersal is undirected whereas migration is directed and return
specific - Fish, crustaceans, turtles and marine mammals migrate between mating/spawning and feeding grounds
86
Q
migrating types
A
- Anadromous - fish live as adults in salt water, spawn in fresh water (shad, striped bass, salmon), more common in higher latitudes
- Catadromous - fish live as adults in fresh water, spawn in salt water (eel), more common in lower latitudes
- Diadromous - divide their lives between freshwater and marine
- Fully oceanic - herring, green turtle, cod
87
Q
Larval dispersal
A
Three spatial scales to understand
dispersal and recruitment
–microscale (cm)
–mesoscale (m-km)
–macroscale or biogeographic scale
- Marine invertebrates may be:
–brooded - direct release
–dispersed a small degree - lecithotrophic
–dispersed a great degree - planktotrophic
88
Q
Planktotrophic dispersal
A
- female produces many (103 to 106) small eggs, larvae feed on plankton, long dispersal time (weeks), some are very long distance (teleplanic) larvae - cross oceans
89
Q
Lecithotrophic larvae
A
- female produces fewer eggs (102 to 103), larger, larvae live on yolk, short dispersal time (hrs to days usually)
90
Q
Direct Release
A
- female lays eggs (oviparous) or broods young, juveniles released and crawl away (viviparous)
91
Q
two scales of larval dispersal and settlement
A
- Larger scale (mesoscale) - 10 - 10 3 km. Small scale movements to take advantage of currents, seasonal release and settlement
- Smaller scale (microscale) - Positive, neg phototaxis, timing, near cues (< 10 -1 m)
92
Q
settling problems of larva
A
Presettling problems:
–Starvation
–Predation in plankton
–Loss to inappropriate habitats
- Larval recruitment is the result of habitat selection & mortality
93
Q
Biogeography of larva
A
- Species with a planktonic larval dispersal form have a greater biogeographic range than species without planktonic larvae
94
Q
why disperse
A
- Local extinction - to export young
- Hedging bets - spread over habitats
- Not for dispersal! Feeding in plankton
95
Q
life in the open sea
A
- Planktonic organisms are dependent on the movement of masses of water
- Phytoplankton require light and zooplankton rely on phytoplankton as food
- Hence both need to remain in surface waters (or migrate into surface waters)
- In order to remain in the surface waters plankton must:
– be less dense than seawater
– increase surface area and hence drag
– swim
96
Q
Plankton definitions
A
- Plankton: organisms living in the water column, too small to be able to swim counter to typical ocean currents
- Phytoplankton or Zooplankton:
– Mixoplankton (or mixotrophic)
– Holoplankton - permanent residents
– Meroplankton - temporary residents
– Neuston - associated with slick
– Pleuston - sticking up above water surface
97
Q
cephalopods
A
- Phylum Mollusca
- Carnivores (squid feed on smaller fish, larger zooplankton)
- Mouth - powerful beak
- Mantle + siphon = rapid movement
- Squids and octopus have an ink
gland; ink expulsion confuses predators - Squid, cuttlefish (demersal), octopods (benthic) - photophores that allow rapid colour change, camouflage, deception of predatory cuttlefish
98
Q
Nekton
A
Nekton: organisms living in the water column that can swim strongly enough to move counter to modest water currents
- Nekton: live under high Reynolds number, meaning that inertial forces dominate over viscous forces
- Boundary layer on fast moving forms is thin
- Minimizing pressure drag is important for fast and continual motion
99
Q
cephalopod locomotion
A
- Locomotion of squid - rhythmic muscular movement of fins, rapid expulsion of water through siphon
hypnome) from mantle cavity. - Nautilus - gas-water balance keeps animal stationary, also can expel water through siphon for rapid attack over short distances
- Cuttlefish - cuttlebone + osmotic pump
100
Q
Chondrichthyes
A
–cartilaginous fishes including sharks, skates, rays - cartilaginous skeleton, replaceable tooth rows
101
Q
Osteichthyes
A
–bony fishes, true bony skeleton - much more diverse than Chondrichthyes, teeth fixed in jaws
- Form of fishes strongly related to their locomotion type and feeding ecology
102
Q
oxygen in gills
A
- Water over gills
- Water flows over gill lamellae and oxygen diffuses into gills
- Blood flow is in opposite direction of water flow - countercurrent exchange - same principle as for heat conservation in dolphins
103
Q
Buoyancy
A
- Fish can regulate bulk chemistry
- Sharks - high lipid content - reduces
bulk density - Bony fish - lower salt content than sea water - reduces bulk density
- Swim Bladder - most bony fish
- Most bony fish - swim bladder; fish can acquire air at surface and esophagus is connected to swim bladder
- Gas gland - gas uptake and release
- Rete mirabile - intertwined capillaries and veins - countercurrent exchange to retain oxygen near the gas gland
104
Q
fish feeding
A
- Two mechanisms in water column:
suction and ram feeding - Many fish chew prey by means of teeth; some have specialized crushing teeth (puffer fish, some sculpins)
- Some species suspension feed, trap
zooplankton, phytoplankton, or particulate organic matter on gill rakers
105
Q
sensory
A
- Bony fish and sharks have a lateral-
line system - This consists of mechanoreceptors
that respond to disturbances in the
water - All elasmobranchs and some fish can sense prey via electroreceptors
- Lateral line system
- Eyes - fish often have excellent vision
- Otoliths in contact with hairlike fibers
- Sounds can be produced during mating seasons
106
Q
schooling
A
- Behaviourally based aggregation of fish
- Most tightly schooling species have silvery sides, which would confuse predators
- Schools sometimes in the form of “fish balls”
- Behaviour related to predation; fish leaving school are attacked successfully
- Schooling may also reduce drag, save on energetic cost of swimming
107
Q
body temperature
A
- Most fishes - temperature
conformers - Tunas and relatives, some sharks, use countercurrent heat exchange to reduce heat loss - have elevated body temperature
- Elevated body temperature allows higher metabolic rate, localized heating of nervous system in some species (e.g., swordfish)
108
Q
mesopelagic fish
A
- Fish living 150-2000 m
- Fish have well developed eyes, often large mouths for feeding on large prey
- Many have ventral photophores, serves purpose of counterillumination - camouflage to blend in with low light from above
109
Q
mammals
A
Cetaceans: whales and porpoises
Pinnipeds: seals, sea lions, walruses
Mustelids: sea otters
Sirenians: sea cows, dugong
110
Q
whales and porpoises
A
All belong to the Cetacea
* Odontoceti-toothed whales
* Mysticeti-baleen whales
* All homeothermic
* Reproduce much the same as terrestrial mammals
* Posterior strongly muscular- propulsion by means of flukes
111
Q
cetaceans
A
Whales and dolphins:
– Very different from other marine mammals
– Adapted to a completely oceanic existence
* No hair
* Breath through blowholes
* Very streamlined body plans
* Have broad horizontal tail flukes (similar to dugong)
* No pelvic appendages
* Two major groups of Cetaceans—toothed and
baleen whales
– Toothed whales are carnivores and relatively small.
* Dolphins, pilot whale, orca
– Baleen whales are filter feeders and relatively large.
* Humpback whale, blue whale
112
Q
odontoceti
A
- Toothed, usually good hunters, feed on squid, fish, small mammals
- Good divers
- Oral communication common
- Many species have bulbous melon, filled with oil - function could be sound reception
- Usually social, killer whales live in pods, maternally dominated
113
Q
orcas
A
- Most widely distributed marine mammal species
- Males have distinctly larger body parts than females (sexual dimorphism).
- Up to 22,000 lb
- 22 ft long
- Resident, transient, and offshore forms that vary.
– Food choice depends on location. - North Pacific populations (Puget Sound) eat salmon.
- Transients feed on larger prey (seals, porpoises, other
cetaceans). - In New Zealand, eat sharks and stingrays
114
Q
Mysticetes
A
- Lack teeth
- Have rows of comb-like baleen
- Use baleen to filter the water
- Filter huge volumes of water to capture enough plankton to
meet energetic needs - The largest whales, in fact, the largest creature on earth (blue
whale) - Adults have horny baleen plates, which strain zooplankton
- Right whales are continuous ram feeders
- Rorqual whales (e.g. Blue) are intermittent ram feeders,
periodically squeeze water out of large mouth chamber
115
Q
ram feeding
A
- continuous
- intermittent
116
Q
Sirenians
A
- Includes manatee, dugong, extinct Stellar Sea Cow
- Sluggish, herbivorous
- Live in inshore waters, estuaries
117
Q
Mustelids
A
- Sea otters are weasels that evolved to live their entire lives in the water.
- Care for young out in the water, so do not use haulout sites.
- Actually use tools to open shelled prey items
118
Q
Diving by marine mammals
A
- Must breathe at surface - no “bends”
- Problem oxygen for long dives
- Most have increased volume of arteries
and veins - Have increased blood cell concentration
- Can decrease heart beat rate and O2
consumption - Can restrict peripheral circulation and
circulation to abdominal organs
119
Q
seabirds
A
- Often colonial breeders
- Believed to be monogamous
- Courtship involves elaborate
displays - Crowded breeding sites,
often with several species,
protected from predators
such as mammals - Feeding involves either
diving or underwater
swimming - Long-distance migration
between nesting and
feeding areas is common
120
Q
marine birds
A
- Penguins - flightless, southern
hemisphere, high latitude,
divers, insulated by blubber and
feathers, countercurrent heat
exchange in circulation to wings
and feet, colonial breeders - Petrels - great gliders, colonial
breeders, often divers from air - Pelicans - generally tropical,
heavy, diverse hunting from
diving to underwater swimming - Gulls, auks, puffins - feed on
fish, often very abundant
121
Q
shorebirds
A
- Include sandpipers, plovers, other groups
- Great dependence upon terrestrial sites, especially for feeding
- Often migrate great distances between feeding and nesting
areas - Variety of feeding mechanisms, ranging from probing beaks
into sediment to catching crustacea and other organisms in
the surf to clipping bivalve adductors and scooping out bivalve
flesh
122
Q
penguins
A
- Flightless birds - wings have evolved
into flippers.
– Can dive at speeds up to 17 mph! - 17 to 20 species
- Adaptations for life in cold
environments
– Very thick layer of insulating feathers.
– Control blood flow to extremities—reduces
amount of blood that is cold at any one time - Reproduce with only one partner each
season
– Both parents care for young once eggs hatch.
– Caring for young is very stressful and strains
parents
123
Q
marine reptiles
A
- Sea snakes - common through the Indo-
Pacfic region - are venomous. Some
lay eggs on land or breed at sea with live
young - Marine Iguanas - Galapagos Islands
(studied by Darwin), not fully adapted to
marine life - Saltwater crocodiles – not fully adapted
but do have a salt gland to excrete
excess salt - Extinct marine reptiles
– Mosasaur
– Icthyosaurs
– And others
124
Q
sea turtles
A
- Eight species, thought to be tropical
or subtropical, but also found in
temperate seas (e.g., California) - All species either threatened or
endangered status
– Easily disturbed by humans
because they have a land
component to their habitat for
nesting
– Have flippers for swimming - Excellent eyesight
- Some of the longest breath-holders
of all air breathing marine
vertebrates—up to 8 hours!
– Specialized nasal glands - Located below each eye
- Salts concentrated by salt-
excreting glands, then leave the
body by dripping down or being
blown out the nose - All nest on sandy beaches and migrate
to feeding grounds; females return to
beach where they hatched, usually
repeatedly; several species shown to
use earth magnetic field to navigate in migrations - Feeding of adults varies (e.g., green
turtle consumes seagrasses and
seaweeds, Kemp’s Ridley eat bottom
invertebrates, leatherbacks eat jellyfish - Leatherbacks distinct from other species,
have temperature conservation
mechanisms, including a countercurrent
exchange heat retention
125
Q
organisms in the pelagic zone
A
- Nekton:
– Most nekton are vertebrates, and most are teleost fishes.
– Squids are a molluscan exception.
– Small squids live in high densities.
– Giant squids reach 18 m in length and live at great depths. - Zooplankton:
– Holoplankton spend their whole lives as plankton.
– Meroplankton are planktonic only as larvae
126
Q
epipelagic zone
A
- Most pelagic animals reside in this zone
- Bright colouration is not common in epipelagic
organisms - countershading is much more
common - occurs within the photic zone - (~200 m)
- A few major habitats are apparent:
- Tropical, subtropical, temperate, polar
127
Q
orienting in the sea
A
- How do pelagic organisms orient
without a solid reference point? - Environmental and seasonal
factors - Changes in time are indicated by:
– Night/day
– Water temperature
– Changes in food source - Changes in space are indicated
by:
– Position of the sun
– Olfaction
– Ocean currents
– Earth’s magnetic field - magnetoreception
128
Q
plankton in the open ocean
A
- Planktonic organisms are dependent on the
movement of masses of water - Phytoplankton require light and zooplankton
rely on phytoplankton as food - Hence both need to remain in surface waters
(or migrate into surface waters) - In order to remain in the surface waters
Plankton must
– be less dense than seawater
– increase surface area and hence drag
– swim
129
Q
patchiness of plankton
A
- Spatial changes in physical-
chemical conditions - Depth gradients in salinity,
temperature, oxygen - Water turbulence and current
transport - Zooplankton grazing balanced
against phytoplankton growth - Localized reproductive behavior
- Localized feeding behavior
130
Q
diurnal migration of plankton
A
- Planktonic organisms often migrate on a diurnal basis (response to light)
–towards the surface during the day
–descend during the night
–or vice versa - Largest migration on earth
- Copepods can migrate ~400 m (upwards
15 m/h, downwards 100m/h) - Some migrations can be ~1000 m
- Highly variable
131
Q
vertical migration
A
- Some zooplankton and some fish are poor long-
distance swimmers. - Small changes to vertical position can change
their environment drastically. - Life in the mesopelagic is always dark with little
food. - Life in the epipelagic is light during the day and
has a lot of food. - Diel vertical migration
- Allows organisms to remain in the dark mesopelagic
during the day - Organisms move into the dark epipelagic at night to feed
132
Q
what drives the cycle
A
- Rhythm is set by day - night cycles
- But then after it is
set, animals can be
placed in a constant
environment (lab,
dark) and day-night
vertical migration will
continue. - After a few days-
weeks the cycle will
dampen
133
Q
Hypotheses to explain migration
A
- Strong light hypothesis
–zooplankton are affected by strong light and
UV - Phytoplankton recovery hypothesis
–zooplankton migrate to let phytoplankton
recover - Predation hypothesis - avoid predators
- Energy conservation hypothesis
–less cost to spend energy in cold waters - Surface mixing hypothesis
–hope for better surface waters upon return
134
Q
movement of nekton at different spatial scales
A
- Small spatial scale - Schooling - usually single
species of fish - Larger spatial scale - Migrations between
reproduction and feeding sites
135
Q
schooling
A
- Behaviourally based
aggregation of fish - Most tightly schooling species
have silvery sides, which would
confuse predators - Schools sometimes in the form
of “fish balls” - Behaviour related to predation;
fish leaving school are attacked
successfully - Schooling may also reduce
drag, save on energetic cost of
swimming
136
Q
large scale migrations
A
- Movement over large
distances detected with
tracking devices. - GPS tag implanted, and
detaches and floats to
surface - sends signal to
satellite - Other tags are permanent in
fish - can produce acoustic
signal, give evidence of
where tag was implanted
137
Q
descending to the depths
A
- Most production is in the surface waters -
phytoplankton - photosynthesis - Not all phytoplankton is consumed by zooplankton
- Plankton sink to deeper waters - supplies organic
matter to many consumers in deeper water - Sinking and vertical position of dead plankton is
related to bulk density of the organism, structures that
create - Drag (bell of jellyfish), water motion, and swimming
ability. - Meals scarcer at depth - organisms adapted to low
input of food from above
138
Q
buoyancy
A
- Bone and muscle tissues are needed for locomotion
of many pelagic organisms. - Maintaining position in the water column is a struggle
with a body that is more dense than seawater. - A variety of factors that offset dense body parts are
used by pelagic organisms. - Adaptations to increase buoyancy
– Stored fats and oils
– Blubber
– Gas-filled floats
– Lungs full of air
– Swim bladders
139
Q
vision
A
- Many animals detect light with aid of a
simple layer of sensory cells, but many
species have complex eyes with focusing
mechanisms (and can see colour) - Allows detection of prey, predators
- Aids in navigation
- Retinas in twilight zone fish
have fewer cones (high
intensity & colour) than
rods (low light) and cones
are often completely absent
in deep sea fish
140
Q
Bioluminescence
A
- Bioluminescence - light manufactured by
organisms, using specialized light organs,
sometimes with the aid of symbiotic
bioluminescent bacteria - Functions to confuse predators
- Perhaps other as yet undiscovered functions
141
Q
mesopelagic zone
A
- Below the photic zone, also called the twilight zone
- 200 m to 700 or 1000m
- organisms rely on food that rains down from above, marine snow, or predation
- Fishes of the mesopelagic have a variety of unique
adaptations. - Small size (usually <10 cm)
- Large teeth and mouths
- Large eyes
- Photophores
142
Q
types of bioluminescence
A
Defensive:
- Startle (flash to confuse predators): squid
- Counterillumination: fish, crustaceans, squids
- lit smoke screen (release of luminescent slime): fish, crustaceans, squid, ctenophores
Offensive:
- lure prey or attract host: angler fish, cookie cutter shark
- illuminate prey: dragonfish, flashlight fish
143
Q
mesopelagic fish
A
- Fish living 150-2000 m
- Fish have well developed eyes, often
large mouths for feeding on large prey - Many have ventral photophores, serves
purpose of counterillumination -
camouflage to blend in with low light
from above
144
Q
below mesopelagic zone
A
- Below 700 to 100 m - Bathylpelagic and
Abyssalpelagic - Fish tend to be black and have fewer photophores
(except angler fish) - Eyes are reduced as is central nervous system
- Weakly ossified skeleton
- long jaws
- unique adaptations for mating
145
Q
Tidal Rhythms
A
- Predictability of tides induces tidal rhythms in organisms
- Affects life history and ecological
characteristics of various species - E.g. spawning, laying eggs, feeding etc
146
Q
zonation
A
- Universal feature of rocky shores, also true of soft
sediments but not as distinct - Zonation claimed to be universal in mid- and high-
latitude rocky shores, but there often are
exceptions - Generally
– a lichen zone
– a periwinkle (littorine gastropod) zone with sparse barnacles
– a barnacle-dominated zone either overlapping with mussel-dominated
zone or with mussels below
– a zone dominated variously, but usually by seaweeds - Two Gradients:
– Vertical – tide levels, time of exposure to air/water
– Horizontal - changing wave exposure
147
Q
vertical gradient
A
- Conditions
–Heat stress, desiccation
–Gas exchange - dissolved oxygen
–Reduced feeding time
–Wave shock
–Biological interactions - competition, predation - Higher intertidal organisms - more resistant to heat
and desiccation stress than lower intertidal
organisms, less time to feed, sessile forms grow
more slowly. - Mobile carnivores can feed only at high tide, usually
feed more effectively at lower tide levels, which are
immersed a greater proportion of the day
148
Q
heat stress/ desiccation
A
- Varies on small spatial scales
- Body size, shape are both
important - reduction of surface
area/volume reduces heat gain
and water loss - Evaporative cooling and
circulation of body fluids aids in
reduction of heat loss - Well-sealed exoskeletons aid in
retarding water loss (acorn
barnacles, bivalves) - Heat Shock proteins
149
Q
oxygen consumption
A
- Intertidal animals usually cannot respire at time of low
tide - Respiratory organs (gills of polychaetes, bivalves)
must be moist to acquire oxygen, and therefore are
usually withdrawn at low tide - Some animals reduce metabolic rate at time of low
tide - Some high intertidal animals can respire from air (e.g.,
some mussels) even at low tide, as long as air is not
too dry Pacific sand bubbler crab,
Scopimera inflata, has
membrane on each leg
(shaded green), which
exchanges gas from air into
arterial blood
150
Q
wave shock
A
- Abrasion - particles in
suspension scrape delicate
structures - Pressure - hydrostatic pressure
of breaking waves can crush
compressible structures - Drag - impact of water can
exert drag, which can pull
organisms from their
attachments to surfaces, erode
particles from beaches, and
carry organisms from their
burrows or living positions - Swash riders: move up and
down to maintain burrowing
position in moist sand, as tide
rises and falls; includes some
bivalves, burrowing mole crab
Emerita
151
Q
causes of vertical zonation
A
- Physiological tolerance of different species at
different levels of the shore - Larval and adult preference - larvae may settle at
time of high tide at high levels, mobile
juveniles/adults have a series of behavioural
responses that keep them at certain levels of
shore - Competition - species may be capable of
excluding others from certain levels of the shore - Predation - mobile predators more effective
usually on the lower shore: affects distributions
of vulnerable prey species - Behaviour - selective movement
152
Q
interspecific interactions and zonation
A
- Why are there vertical zones, with
dominance often of single sessile species
within a zone? - Possible explanations:
–(1) differences in tolerance of species at
different tidal heights
–(2) competitive interactions
–(3) predation changes with tidal level
–(4) larval and adult preference
153
Q
connell field manipulation experiments
A
- Studied factors controlling vertical zonation by
selective inclusion and exclusion of
hypothesized interacting species - Species
–Chthamalus stellatus - acorn barnacle, ranging
from subtropical latitudes to northern British isles
–Semibalanus balanoides - acorn barnacle,
ranging from Arctic to southern British isles,
overlapping in range with C. stellatus
–Nucella lapillus - carnivorous gastropod, drills and
preys on barnacles - Experiment:
–Transplanted newly settled Chthamalus to all tidal levels
–Caged some transplants, excluded Nucella
–Allowed Semibalanus to settle and cleaned newly settled
Semibalanus off some rocks - Results:
–Chthamalus survival poorer in presence of Semibalanus
–Chthamalus survival decreased where Semibalanus grew
the fastest
–Chthamalus survival increased in high intertidal due to its
resistance to desiccation
Conclusion: - Predation important in lower intertidal
- Biological factors control lower limit of species
occurrence - Physical factors control upper limit
- Community structure a function of very local
processes (larval recruitment not taken into
account as a factor) - Predators reduce prey density
- Prey species compete
- Conclude: predation may promote coexistence
of competing prey species
154
Q
Robert Paine
A
- Rocky shores of outer coast
of Washington State - 1966
American Naturalist. - Principle predator - starfish
Pisaster ochraceus - Pisaster preys on a wide
variety of sessile prey
species, including barnacles,
mussels, brachiopods,
gastropods - Removal of Pisaster ochraceus
- Successful settlement of recruits
of mussel Mytilus californianus - Other species greatly reduced in
abundance, Mytilus californianus
became dominant - Conclude: Pisaster ochraceus is
a keystone species, a species
whose presence has strong
effects on community
organization mediated by factors
such as competition and
predation
155
Q
Disturbance
A
- Disturbances are physical events that
influence the distribution and
abundance of organisms (biological
disturbance can occur as well) - Disturbances may also reduce
abundance of competing species - Disturbances may therefore allow
coexistence of competitively inferior
species or may allow colonization of
species adapted to disturbance - A very small scale disturbance in a mussel
bed might just result in the mussels moving
and sealing off the opened patch - Larger patches might be colonized by other
species, and the patch might last many
months or even indefinitely - Therefore, spatial scale of disturbance
might affect the spatial pattern of
dominance of species, creating a mosaic
of long-lived patches
156
Q
why spatial scale matters
A
- Cannot extrapolate all
interactions at small
scales to large scales - Alternative stable states
at some large spatial
scale - Thus large patches
created by disturbance
may be qualitatively
different than small scale
interactions - outcomes
may be different
157
Q
larval recruitment
A
- Results from manipulative experiments usually
depend upon steady recruitment of larvae of
competing species - What if recruitment is variable?
- Competitively superior species might not take
over, owing to low rates of recruitment - Recruitment might be reduced if currents are not
favourable, high water flow results in flushing of
larvae from inshore habitats, poor year for
phytoplankton results in poor year for success of
plankton-feeding larvae
158
Q
soft sediment intertidal
A
- Higher intertidal species burrow more
deeply - Zonation not as distinct as on rocky shores
- Water retention reduces vertical desiccation
and temperature stress gradients
159
Q
vertical stratification
A
- Dominant species found at
different levels below
sediment-water interface - Experimentally reduce density
of deep-dwelling clams,
remaining individuals grow
faster; demonstrates effect of
density - Removal of shallow dwelling
species of bivalves has no
effect on growth of deeper-
dwelling species
160
Q
food supply in soft sediment intertidal
A
- Suspended phytoplankton for suspension
feeders (e.g., bivalves, polychaetes) - Microalgae and bacteria for deposit feeders
- Decomposing organic matter (phytodetritus
and decomposing seaweeds) - Input can be spatially variable
161
Q
beaches and wave action
A
- Exposed beaches - strong erosion
and sediment transport - Difficult environment for macrobenthos
to survive and maintain living position - Swash riding - means of moving up
and down with rising and falling tide -
maintain position in wet but relatively
noneroded tidal levelm
162
Q
mangrove forests
A
- Dominated by species of mangroves, common in
subtropical and tropical protected shores - Mangroves broadly rooted but only to shallow depth
in quite anoxic soils - Underground roots have projections into air that
allow gathering of oxygen - Highly salt tolerant
- High primary productivity
- High supply of particulate
organic matter, especially
falling leaves, which subsidize
animal growth - Zonation of mangrove
species - Roots support a rich
assemblage of sessile marine
invertebrates
163
Q
sea grasses
A
- Sea grasses are marine
angiosperms, or flowering
plants, that are confined to
very shallow water - Extend mainly by subsurface
rhizome systems within soft
sediment - Found throughout tropical
and temperate oceans - Grow best in very shallow
water, high light and modest
current flow
164
Q
ecology of seagrass
A
- High primary production, support
a diverse group of animal species - Sea grass beds reduce current
flow - Deter the entry of crab and fish
predators from side - May enhance growth and
abundance of infaunal suspension
feeders near edge, although
phytoplankton may not penetrate
far into bed
165
Q
grazing and community in sea grass
A
- Grazing on sea grasses variable: in
temperate zone, grazing on Zostera
marina (eel grass) is minimal - In tropics, sea grass beds comprised
of several species that are grazed
differentially because of different
toughness, cellulose content - Green turtles nip leaf tips,which
encourages growth of more soft and
digestible new grass - Even tough grasses grazed by turtles,
urchins, dugongs. Green turtles have
extended hindguts with intestinal
microflora, digesting cellulose
166
Q
decline of sea grass
A
- Sea grasses very vulnerable to eutrophication -
phytoplankton shade sea grasses, strong
reductions of eel grass beds in North America - Possible that overfishing results in reduced
grazing and overgrowth of epiphytes, which
smothers sea grasses - Dredging, boat traffic, also causes decline of sea
grasses - Disease important, fungus caused eelgrass
epidemic in 1930s, recovery, but other fungi are
now cause of sporadic diseases in tropical sea
grasses
167
Q
kelp forest
A
- Kelp forest - rocky reef complex found in cooler
coastal waters with high nutrients - Kelp forest–rocky reefs are often dominated in
shallow waters by kelps and seaweeds and by
epifaunal animals in deeper waters animal-
dominated rocky reefs - Switch from cover dominance by rapidly growing
seaweeds in shallow water to epifaunal animal
dominance in deeper water - Dominated by brown seaweeds
in the Laminariales - Found in clear, shallow water,
nutrient rich and usually <
20°C, exposed to open sea - Generally laminarian seaweeds
have high growth rates, often of
the order of centimeters/day
(Macrocystis -60 cm/day) - “Forests” can be 10-20 m
(Macrocystis - 50 m) high or
only a meter in height
168
Q
rocky reefs
A
- Abundant communities of algae
and invertebrates, often dominated
by colonial invertebrates. - Often are very patchy, with
alternations of rocks dominated by
rich invertebrate assemblages and
turf-forming calcareous red algae - Subtidal rock wall patches of
animals often are short on space,
suggesting the importance of
competition
169
Q
kelp forest and urchins
A
- Herbivory - herbivorous sea urchins
- Carnivory - sea otter Enhydra lutris
can regulate urchin populations - Result: trophic cascade; add otters,
have reduction of urchins and
increase of kelp abundance;
reduce otters: kelp grazed down by
abundant urchins - Recent history: otters hunted to
near extinction, their recovery has
strong impacts on urchin/kelp
balance - In lower-latitude California kelp
forests, a larger diversity of
predators beyond sea otters exerts
top-down effects
170
Q
kelp forest community structure
A
- Effect of storms: remove kelp
- El niño: storms + warm water = kelp
mortality - California kelp forests: storms
remove kelp, urchins roam, and
inhibit kelp colonization and growth:
barrens - California kelp forests: if kelp growth
is rich, urchins stay in crevices and
capture drift algae - This leads to two alternating states:
barrens and kelp forest
171
Q
coral reefs
A
- Geological importance:
often massive physical
structures - Biological importance:
biological structure, High
diversity, - Economic importance:
shoreline protection,
harbours, fishing, tourism - Compacted and cemented assemblages of
skeletons and sediment of sedentary organisms - Constructional, wave-resistant features
- Built up principally by corals, coralline algae,
sponges, and other organisms, but also
cemented together - Reef-building corals belong to the Scleractinia,
have endosymbiotic algae known as
zooxanthellae; high calcification rate - Topographically complex
172
Q
reef building corals
A
- Belong to the phylum
Cnidaria, Class Anthozoa,
Order Scleractinia - Secrete skeletons of calcium
carbonate - Are colonies of many similar
polyps - Can be divided into branching
and massive forms - Have abundant
endosymbiotic zooxanthellae
173
Q
zooxanthellae
A
- Dinoflagellate:
– Once considered as one
species: Symbiodinium
microadriaticum
– at least 10 distinct taxa with large
genetic distance among species - Observed in species of anemones,
hermatypic corals, octocorals,
bivalve Tridacna, ciliophora
(Euplotes) - Found in corals within tissues
(endodermal), concentrated in
tentacles
174
Q
types of corals
A
- Hermatypic: Reef
framework building,
have many
zooxanthellae, hi
calcification - Ahermatypic: not
framework builders, low
calcification
175
Q
coral growth
A
- Branching: grow in linear
dimension fairly rapidly 10
cm per year - Massive: Produce lots of
calcium carbonate but
grow more slowly in linear
dimensions, about 1 cm
per year
Costa Rica, Acropora palmata
(elkhorn coral)
Costa Rica, Colophyllia natans
(brain coral)
K. Müller
K. Müller
176
Q
coral biodiversity
A
- Coral species usually first identified on basis of
morphology - Problem: coral species have a large degree of
morphological plasticity - variable growth
response to variation in water energy, light,
competitive interactions with other species - Problem: nearly morphologically identical species
- Species now identified more with DNA
sequencing
177
Q
bleaching
A
- Bleaching - expulsion of zooxanthellae
- Causes - stress (temperature, disease)
- Mechanisms - poorly understood - zooxanthellae cells
appear to die and are expelled - Test among mechanisms with fluorochromes; support for
cell death under temperature stress (Strychar et al. 2004 J.
Exp. Mar. Biol. Ecol.)
178
Q
limiting factors of corals
A
- Warm sea temperature (current problem of global
sea surface temperature rise) - High light (symbiosis with algae)
- Open marine salinities
- Low turbidity - coral reefs do poorly in near-
continent areas with suspended sediment - Strong sea water currents, wave action
- Reef growth a balance between growth and
bioerosion - Reef growth must respond to rises and falls of sea
level - pH? Increasing ocean acidity a problem?
179
Q
type of coral growth structures
A
- Coastal reefs - wide variety of reefs from massive
structures ( Great Barrier Reef), to small patches such
(Eilat, Israel) - Atolls - horseshoe or ring-shaped island chain of
islands atop a sea mount
180
Q
physical environment of deep sea
A
- Absence of Light
–Hence, absence of
Photosynthesis
–Adaptations of organisms
reflect this absence of light - to find food
- to find a mate
- Pressure
–considerable range
–has significant effect - Salinity
–tends to be quite constant - Temperature
–Thermocline - isothermal - no
changes (unusual)
–Some exceptions (e.g.
hydrothermal events) - Oxygen
–due to thermohaline
circulation and O2 rich waters
from arctic and antarctic
181
Q
pressure in the deep sea
A
- Effects of pressure are not well understood,
but there are some apparent trends.
–Lower metabolic rates
–Lowered growth rates
–Lowered reproductive
rates
–Longer life spans
–Gigantism
182
Q
composition of sea floor
A
- Sedimentary materials from planktonic organisms
- Siliceous ooze - Radiolarians, Diatoms
- Calcareous ooze - Foraminiferans (foraminiferan ooze) or
coccolithophores - Accumulate very slowly (1cm/1000 years)
183
Q
sampling of subtidal benthos
A
- Types of bottom samplers:
–Dredges
–Sleds
–Grabs
–Corers
