6 Intertidal Rocky Shores Flashcards

Question

The biotic environment of intertidal rocky shores is mainly influenced by what? (categorization)

Answer 1

1. dominant forms 2. zonation patterns 3. patch and temporal dynamics 4. trophic structure

Answer 2

- tolerant to desiccation stress (Austrocknen) e.g. seaweeds have - morphologies and alginate content that help retaining moisture -complex physiological adaptations to desiccation

Answer 3

- isophasic strategy - isospatial strategy most organisms have mixed complex patterns

Answer 4

Forms adapted to either the marine or air environment which, through a high vagility, access the intertidal zone in the periods in which it is hit by the favorable phase. Dynamic colonization of the intertidal environment

Answer 5

Organisms that manage to remain in the intertidal belt regardless of the temporal alternation of the two phases. The activity of these anymals is limited to the time that is suitable for moving and feeding

Answer 6

- intertidal species tat show marked distributional patterns from high to low shore: - marked changes in species composition - increase of species diversity and biomass

Answer 7

regular variation in the distribution and abundance of organisms along gradients in space

Answer 8

- One of the main research topics in rocky shores has focused on understanding the relationships between environmental gradients and species distribution and the processes that generate them - Gradient analysis: study of the effects of varying a factor on the way populations are distributed (are there clear boundaries?)

Answer 9

- In addition to relatively predictable gradients, the distribution of organisms exhibits great small-scale heterogeneity (patchiness) - Sometimes patchiness is prevalent to the point that we are talking about mosaic populations

Answer 10

disturbance. - Disturbance events in nature (storm surges, herbivores, abrasion, etc.) that are heterogeneous in space and time originate populations consisting of patch mosaics with different colonization dynamics. - A patch is a portion of the localized, discrete and uniform habitat in which the effect of a disturbance is homogeneous and within which the subsequent dynamics are similar (Petraiti et al. 1989)

Answer 11

- temporal patterns (seasonal/ non seasonal) -cyclic dynamics

Answer 12

- abiotic factors (mainly wave motion, tidal regime) - Studies have focused on the physiological tolerance of the different species to drying, temperature, hydrodynamics, in order to identify tolerance limits

Answer 13

biotic factors (interaction between species)

Answer 14

* common resources must be limited in quantity * damage is generated by competition on each species. Often this damage is not homogeneously distributed among the species → asymmetry

Answer 15

- intraspecific - interspecific difficult to separate

Answer 16

- by exploitation (indirect competition) - by interference (direct competition)

Answer 17

there is no direct contact between competing organisms, and competition is mediated by the resource → a resource exploited by one organism will no longer be available for another organism

Answer 18

There is direct contact between organisms

Answer 19

* Competition by "consumption" (eg. of nutrients, light, etc.) * Competition by "pre-emption" (filling of space and inhibition of recruitment)

Answer 20

* Competition by "overgrowth" (competition for space) * Competition by "allelopathy" (chemical) * Competition by "aggression" (clash or defense of the territory) * Competition by "physical damage"

Answer 21

- competition between Semibalanus and Chthamalus hypothesis - previous explanation was that the net boundary between the two species was determined by their different physiological tolerances to drying - abiotic factors: hypothesis 1) Chthamalus is excluded from the lower areas because it does not tolerate long periods of immersion 2) Semibalanus is excluded from the higher areas because it does not tolerate drying - biotic factors: hypothesis 1) Semibalanus excludes Chthamalus in the competition

Answer 22

Organisms of the lower horizons cannot survive the higher horizons, while those of the upper horizons can adapt to the environmental conditions of the lower horizons but are outclassed by those of the lower horizons in terms of metabolic performance, growth, ability to exploit resources

Answer 23

- It is the consumption of an organism (the prey) by another organism (the predator), in which the prey is alive when the predator attacks it for the first time. - It is a direct trophic interaction that implies a negative effect of the predator on the prey and a positive effect of the prey on the predator - The predator is an agent of mortality → it influences the structure and evolution of communities

Answer 24

Situation: - mussel bed on a relatively flat rocky bench - large numbers of Pisaster ochraceus at the lower part of the bed (starfish) - they have a limited time for feeding at the time of high tide - they tend to feed on the lower part of the mussel bed, which is here dominated by Mytilus californianus Hypothesis: - Pisaster causes the discontinuous zonation by preying on the competitive dominant species Demonstration of 3 key ecological concepts: 1) predation affects not only the dynamics of prey populations but also the structure of the community 2) Pisaster is a keystone species 3) The control exerted by pisaster is an indirect interaction – keystone predation

Answer 25

Predation can control the outcome of competition (or other interactions) between species, with outcomes that affect the diversity of communities

Answer 26

It has a much greater community structure control effect than that of other predators in the system e.g., Nucella and disproportionate to its abundance

Answer 27

- strong controlling effect - Grazing is a method of feeding in which a herbivore predator feeds on low-growing plants such as grasses or other multicellular organisms, such as algae - Many marine organisms are grazers, including many molluscs (e.g. limpets, chitons, snails), echinoderms (e.g. urchins) and fish species (e.g. salemas)

Answer 28

Observation: - Jane Lubchenco observed that in her region tide pools tended to have either high density of green seaweeds or high density of red seaweeds. - She knew that Littorina snails graze on seaweeds and in the lab it has a preference for the green Enteromorpha over the red Chondrus. Experiment: - She manipulated Littorina abundance in rock pools Result: - Enteromorpha is the competitively dominant seaweed in rock pools - Littorina controls algal species diversity similarly to what done by Pisaster What caused differences in Littorina densities? - snails were in turn controlled by their predators (green crabs) which in turn were controlled by their predators (sea gulls). - Sea gulls would quickly eat all crabs, but crabs escape by hiding in the seaweeds

Answer 29

trophic cascades + keystone predation

Answer 30

- Differences along gradient of wave exposure can be explained by differences in grazing pressure - What factors cause observed patterns on rocky shores? * Hydrodynamic forces caused by waves? * Biological interactions, mainly predation? * Other abiotic stress factors, e.g. heat & desiccation? - Do hydrodynamic forces limit macroalgae? --> Transplantation experiment - Does limpet predation limit macroalgae? --> experiment limpet removal - Overall Conclusion * Hydrodynamic exposure and grazing interact to control macroalgae * In absence of grazing, algae will recruit but waves will prune or dislodge plants * Recruitment is prevented if limpets exceed a critical density * Limpets are favoured by wave exposure??

Answer 31

- 3 treatments - sometimes large effects on fucoid canopy algae - results show less macroalgae in Southern Europe (picture) - why? from Northern to Southern Europe 1) Increase in pool of grazer species 2) Increasing grazing pressure 3) Increase in physical stress - Potential explanations 1) Limpets and other grazers actually are major structuring agents in southern Europe: -so effective at preventing development of fucoids that they eliminate the propagule supply 2) Fucoids are not adapted to increased physical stress in southern Europe 3) Combination of above reducing likelihood of fucoid establishment

Answer 32

- were considered as a refuge - experimental work shows: NOT TRUE

Answer 33

facilitation is synonymous with mutualism - facilitation is a broader term - mutualism is most often associated with symbiosis - Interaction between species resulting in a mutual benefit: individuals of a population of each of the mutualistic species grow and / or survive and / or reproduce at a higher rate when in the presence of individuals of another species. - The benefit can be food resources, protection from enemies, or a favorable environment in which to grow and reproduce. - It can occur both between individuals of the same species (density- dependent survival) and between individuals of different species. - Often asymmetrical benefits

Answer 34

- direct: without the action of intermediaries (resources or other species) - indirect: depends on the effects on an intermediary (resource or other species)

Answer 35

- stress: desiccation (drying out) - benefactor (has positive effect on the other): canopy forming microalga - beneficiary (the facilitated species): barnacles every interaction has pros and cons the same type of interaction can change depending on the circumstances - Survival of barnacles decreases in South when Canopy cleared - Opposite in north - Competition for space or food, could be both - south: lots of stress: interaction between seaweed and barnacles is a facilitation - In north there is not that much stress: canopy not needed - different interaction depending on environmental factors

Answer 36

hypothesis: mussels facilitate macroalgae at exposed sites - Macro alga could not withstand the wave exposure unless mussels there

Answer 37

- Greater abundant of competitive interaction in more bellin(?) environment where good conditions - X-achse rechts: Very stressed environment - Few that survive have a lot of positive interaction - Less stressed zone : more negative competition

Answer 38

- trophic web ≠ trophic cascade - trophic web: the transfer of energy within a system (who eats what)

Answer 39

- a discrete and localized event that determines the removal of individuals from the population - creates the opportunity for new individuals to settle (Sousa 1984) → frees up resources, mitigating the intensity of competition

Answer 40

1) Physical factors: Sea storms Sediment (abrasion / suffocation) Landslides Fires Prolonged drying Floods Prolonged drought 2) Biological factors Predation Illnesses 3) Anthropogenic factors Removal of organisms Trampling

Answer 41

- Type of disturbance - Extension - Intensity - Duration - Frequency - Localization

Answer 42

- suggests that ecological communities are most diverse and stable at intermediate levels of disturbance - According to IDH, low levels of disturbance may allow competitive species to dominate and exclude less competitive species, leading to lower diversity. - On the other hand, high levels of disturbance may prevent any species from establishing and maintaining a stable population, also reducing diversity. - Intermediate levels of disturbance are thought to create a balance, allowing both competitive and less competitive species to coexist and maintain higher biodiversity. - looks like curve from predation effects - Not too different theories, matter of scale, basically the same - If you have a with system with no disturbance there will be predators destroying the ecosystem - Aim is to create patch - Species can colonize a patch

Answer 43

* It is able to reach it (dispersion) * appropriate conditions exist (patch characteristics) * other species do not preclude it (interspecific interactions)

Answer 44

patch characteristics, such as - size - shape - location - time of patch creations - characteristics of the substrate

Answer 45

fucoids --> fucales --> brown algae - Classical experiment on rocky shores! (Hawkins) - Seaweeds grow where limpets have been removed - Real story: limpets removed --> empty * After months: strip with seaweeds * After 5 years: strip is rock and all around seaweeds - Why?? * System keeps moving from one state to another one * Cyclical dynamic * State depends on patchiness * Each patch can be at one stage  they alternate

Answer 46

- Fucus = algae - P. vulgata = limpet (--> dispersal) - Vulgata eats fucus but also needs it for protection (special relationship) - Vulgata tends to aggregate near fucus

Answer 47

- driven by recruitment fluctuations - Complex relationship (patella, seaweed) - Positive in terms of food and shelter - Seaweed and barnacle: compete for space - Patella and barnacles: B have neg. effect in limpets - Also the other way around - recruitment fluctuatins - Systems shift depending on which species recruits another one?

Answer 48

- cyclical dynamic - P. vulgata: specific aggregative behavior (near Fucus) --> Fucus = food --> also facilitated by Fucus (not sure exactly how) → aggregative behavior - Here: state1) dominated by barnacles - Basically empty rock - What recruits first? Barnacles - They limit grazing by limpits because they are very hard - Seaweeds can grow - State 2) Fucus starts growing --> reduces barnacles abundance - Also limpet grows, has a different behavior - Limpets start growing. Fucus disappears, but limpets need fucus - Fucus moves to side –> Strip becomes empty again! (process of years)

Answer 49

- Clear isolation-by-distance: populations are strongly structured - If it increases they will be separated - Means: needs to take into account for restauration plans - Be careful where to do it - Connectivity within population is very important - Try to create stepping stones for the dispersal when trying to restore - Restore the connectivity - regional genetic variability bec. of stepping stone and habitat continuity

Answer 50

- top-down: Density variations of top predators produce variations in population density at lower trophic levels - bottom-up: the community structure is regulated by the basal energy trophic input

Answer 51

- top-down - bottom up had little consideration

Answer 52

-Can be a limiting factor in intertidal rocky shore - IRS as a stressful environmnet - Nutrient availability can vary a lot on local and regional scale (Generally Mediterranean nutrient poor --> pretty blue waters)

Answer 53

- Local: experiments: structure of IRS different where certain birds-colonies are and where not - Birds as predators e.g. limpets (top-down) - Diff. view: guano rich of nutrients - Bottom-up through nutrients from the guano (verwitterung von exkrememnten von seevögeln) - guano has positive effect on algae - increase in algae has effect on limpets: increased growth rate, max size, max reproductive potential - also effect on other invertebrates associated with algae

Answer 54

- local scale: guano effect from bird colonies - differences in exposed and sheltered environments - Wide geographical difference linked to oceanographic gradients of upwelling and productivity

Answer 55

1) Filtering biomass (e.g. mussels) 10-50 times more abundant on exposed reefs than on sheltered reefs. Possible explanations: - Either: Lower predation and higher recruitment - Or: greater contribution of debris material 2) They show that in exposed sites the concentration of debris is twice as high as in sheltered sites 3) Often insufficient in situ productivity → intertidal reef organisms supported by food inputs from other systems (in South Africa 60/85% food is detritus that comes from subtidal kelp beds)

Answer 56

- Strong upwelling along the western coasts - Little or no upwelling along the eastern coasts - Productivity gradient reflects the oceanographic gradient because: * From west to east: grazer biomass and filter feeder biomass decreases * less biomass --> more chlorophyll (clearer water) --> increase of shell length (limpets)

Answer 57

- habitat loss - coastal population and shoreline degradation - urban constructions - industrial, transport and tourism infrastructure - tourism and trampling - pollution - invasive species - overharvesting - climate changes

Answer 58

- e.g. UK: claim has affected >85% of estuaries and losses if intertidal habitats between 25-80% - e.g. Europe: > 22000 sq-km are artificial coasts - also

Answer 59

- a mussel (Mytillus galloprovinciales) introduced in South Africa in 1970's - growth rate rapid, desiccation-tolerance high - has outcompeted limpet and mussel that used to dominate mid to low intertidal west coasts - mussel and limpet interaction influenced by wave-action/-exposure - semi-exposed: limpets dominate - more exposed: mussel dominates

Answer 60

- expansion depends on oceanographic conditions, temperature and physical barriers - warmer waters at east-coast, cooler at west-coast --> transition between temp. as main factor limiting recruitment spread - currents

Answer 61

! Transition from algae- to invertebrate-dominated ! - through direct predation on birds that forage in the intertidal - rats keeps number of certain birds low - less limpets and snails are eaten - more limpets and snails etc that forage on algae

Answer 62

- creates lots of new space - may create space for invasive species - key stone species may be harvested

Answer 63

e.g. - sea level rise - changing shores --> shifting intertidal extent and slopes

Answer 64

- sea level rise changes the proportion of vertical and horizontal surfaces that are available for colonization - that will cause quantitative changes and qualitative changes

Answer 65

Reduction of the intertidal area extent. This is likely to reduce numbers of species via species-area relationships alone.

Answer 66

Changes in the inclination of the substratum. This is likely to affect species composition and distribution

Answer 67

--> coastal squeeze - intertidal habitats trapped in a coastal squeeze - trapped between human population and climate changes sea-wise (rising sea level) - intertidal zone shrinks, no migration landwards

Answer 68

- projected losses range between 20% and 70% of current intertidal habitat - most severe at sited where the coastline is unable to move inland (due to steep topography or seawalls)