Rocky shores Flashcards
Physical characteristics of rocky shores?
High energy - wave exposure removes soft sediment = stable substrate.
Rocky shore productivity?
Autochthonous = high productivity derived from same location it's used. Turbulent water = high O2. Plankton w/ tides = recruitment. Land runoff. Broken organic matter. Shallow water = high light.
Challenges of rocky shore?
Desiccation when exposed. Wave action. Temp, salinity, + light fluctuations. Double predation (marine + birds). Pollution.
Intertidal zone features?
Main physical factor = submergence.
Most intertidal species = marine origin.
Zonation due to competition, physical factors, + predation = resource partitioning.
Small, hard-shell at top. Big, fleshy, mobile at bottom.
Zonation physical factors?
Desiccation, wave action, light, turbidity (water clarity), temp, + slope.
UK seaweed zonation?
Pelvitia: Waxy. Needs emersion (rots in water). Grows slowly = outcompeted lower down. Fucus spiralis: Spiralled fronds trap water. Fucus vesiculosus (bladder wrack): Large SA = susceptible to desiccation. Laminaria: Kelps w/ long fronds. Require immersion. Surge zone = strong anchors (microhabitat).
Macroalgae zonation factors?
Ability to maintain photosynthesis in air.
Upper limits: Desiccation tolerance.
Lower limits: Competition for space, + grazing (eg: limpets).
Seaweed microhabitats?
Seaweed mats = moist when tide out = microhabitat for epiphytes + cryptic species.
Eg: Bryozoan colonies on fucoid fronds, + Tricolia pullus (pheasant shell) found on red algae (linked distributions).
Rocky shore grazers?
Limpets + periwinkles (Littorina litorea) - radula graze to bare rock.
Urchins.
Mussels.
Urchins?
Lower shore + subtidal zone. Fleshy macroalgae + kelp.
Keats et al (1990) - experimental removal of urchins = canopy algae dominates.
Sea urchin barriers destroy ecosystems (sea otters).
Mussels?
Beds form microhabitats. No preferential settlement - mortality determines distribution.
Upper shore limit = desiccation. Lower shore limit = starfish predation.
Must submerge to feed. Moved = affected growth.
Lower shore mussels can reproduce more (trade-off).
Adaptations to emersion?
Prevent water loss: Mucous layer, shells, + behaviour.
Respire when tide is out:
- Limpets have secondary gills around shell margin = use water trapped on rock surface.
- Anaerobic respiration (tolerate long-term O2 debt).
- Suppress metabolic rate = reduced O2 demand.
- Tolerate acidity from CO2 buildup.
Adaptations to heat - limpets?
Upper shore: Domed = less body surface in contact w/ hot rock + higher in air (increased air flow).
Lift shells off surface = air flow under.
Adaptations to wave action?
Molluscs: Low-profile, hydrodynamic shells.
Mussel tethering: Byssal threads + glues.
Sea stars: Suctioning feet.
Isopods: Hook-like appendages.
Kelps: Hold-fasts (strong + flexible).
Periwinkle zonation?
Top shore: Small periwinkle Melarhaphe neritoides.
Upper shore: Littorina saxitalis (internal fertilisation + live young).
Midshore: Flat periwinkle Littorina obtusa (fucoid seaweeds).
Lower shore: Common periwinkle Littorina littorea.
Periwinkle adaptations?
Avoid heat/water loss: Crevices + cluster.
Light-coloured shells reflect light. Thick shells prevent water loss.
High enzyme thermostability.
Produce uric acid, not ammonia = reduced water loss.
Lower metabolic rate during exposed periods = lower O2 consumption.
Tomenak + Somero (1999).
T funebralis (upper shore, T brunnea (mid shore), T montereyi (lower shore). Heat stress (find mortality temp). T funebralis coped w/ highest temp.
Rocky shore predators?
Limited to lower shore (can’t cope w/ desiccation + thermal stress).
Need moisture to move = rock pools, crevices, seaweed.
Eg: Dog whelks (Nucella lapillus) - Radula bores into shells (mussels + bivalves). Secrete paralysing chemicals + digestive enzymes, + suck out body using proboscis.
Connell (1961).
Importance of competition in barnacle distribution.
Barnacle settlement: 7 larval stages (6 nauplii + 1 cyprid). Test habitat before settling.
C. stellatus cyprids better at surviving heat + desiccation. Upper limit determined by desiccation.
S. balanoides cyprids grow faster (don’t waste energy on heat shock proteins) = undercut C. stellatus.
If S. balanoides removed, C. stellatus can live on lower shore.
Dog whelk predation sets lower limit of S. balanoides.
Paine (1969).
Role of starfish in maintaining diversity.
Piaster ochraceus predates mussels = lower shore limit.
Remove starfish = mussels take over = reduced diversity = top-down control.
Rock pools?
Affected by height on shore, wave exposure, + algae abundance (affects O2).
Palaemon shrimp = stenohaline = only found in lower rock pools.
Harley et al (2009).
Rocky shore temp can increase from 10-40C in single low tide.
Patella has higher thermal tolerance in summer than winter (more heat shock proteins?).
Increased ridges in shells only effective in high-wind environments (eg: S. gigas has deep ridges, but still has lower thermal tolerance than P. vulgata, w/ small ridges).
Original thought: Does this concept apply to all intertidal invertebrates (eg: barnacles + encrusting organisms unexplored).
Shell plasticity may help limpets adapt to future climate change, but limited by ecology + genetics?
Tomanek + Helmuth (2002).
Physical factors originally seen as most important in controlling distribution.
Now combine biotic factors (eg: competition, predation) w/ physical factors.
Eg: Piaster ochraceus (seastar) predation on Mytilus californianus depends on temps from near-shore upwellings.
Need to combine physical + ecological approaches when predicting consequences of climate change.
Trade-offs: Increased byssal thread strength in response to seasonal changes in wave force - constrains reproductive output.
Physical variability = selective force for genetics.
- Aminopeptidase enzymes in M. edulis differ in rate of action based on salinity.
Future: Find markers for sublethal stress experienced in natural conditions.
