Lecture 19- Rocky Intertidal Corals and Whales Flashcards
vertical zonation
- hallmark of intertidal zone
- communities are divided into distinct bands or zones as characteristic heights
how are species arranged?
species are not randomly distributed throughout the zone by arranged within narrow vertical vertical ranges
how do the zones look like?
sharply divided belts easily distinguished by the colors of the assemblage (community) of organisms that live there
physical stresses
often set the upper limit to species distributions
physical stresses examples
- desiccation
- temperature
- food availability
- wave energy
- salinity
- dissolved oxygen
biological interactions
- often set the lower limit to species distributions
upper limit of grey and rock barnacles
determined by emersion, larvae that settle too high in the intertidal dry out and die (physical factor)
little grey barnacles
can tolerate drying better than rock barnacles so they settle higher in the intertidal
lower limit for rock barnacles
determined by competition from mussels and predation by whelks or sea stars (biological factors)
biological factors
- competition for space: space on rock to attach is a valuable source that is in short supply
- predation
general rule of zonation
- upper limit is usually determined by physical factors
- lower limit is determined by biological factors
physical disturbance
- can regulate species diversity within a community
- examples: wave energy from storms and log damage
- can open up gaps or patches in the rocky intertidal
intermediate disturbance hypothesis
disturbance maximizes species diversity by periodically removing competitively dominant species and allowing less competitive species to reestablish themselves
too much disturbance
keeps the rock bare with few species
too little disturbance
allows the dominant competitor for space to take over and form a monoculture (single species)
starfish predation
- produces high intertidal community diversity
- Sets lower limits of mussel distributions in rocky intertidal
- Leads to higher species diversity within a rocky intertidal community
mussels
out compete most of the other intertidal organisms for valuable space
pisaster (starfish) predation
- sets the lower distributional limit to mussels and below this distributional limit other species can settle in
- its removal allow mussels to take over
keystone species
- species that have effects on their communities that are proportionally much greater than their abundance would suggest
- example is pisaster
sea otters and sea urchins
- sea otters eat sea urchins which eat tiny kelp before they grow large
- removal of sea otters allow increase of sea urchins and decrease in kelp
coral anatomy
- calcium carbonate support structure
- process of building calcium carbonate reef structure is very slow: <1 mm per year to about 20 mm per year
Zoozanthellae
- chlorophyll-containing algal symbionts that live in the coral polyp
- give corals their colors
corals receive — of their overall nutrition from photosynthetic-derived products
60-90%
Limits to Coral Growth
- temperature
- sunlight
- space to grow
- predation
temperature and corals
- Limits most coral growth to tropical latitudes
- Optimal: 26-28 C
- Restricted: 18-36C
- Boundary for 20C isotherm: most corals live within this boundary
sunlight and corals
- Limits coral growth to a depth range extending from the ocean surface down to maximum of about 25 meters
- Light required for zooxanthellae to photosynthesize
drowned reefs
dead reefs that occur when the island sinks too fast or sea level rises too fast and the reef cannot keep up with its upward growth because it becomes too submerged in deep/dark waters
the competitive advantage for taking over space is shifted in favor of macroalgae when
nutrients from agricultural activities run off the coast and onto coral reefs
crown of thorns starfish (acanthaster)
- important predator of corals
- eutrophic conditions increase phytoplankton which increases growth of acanthaster
— of the Great Barrier reef has been bleached since 2016
half
increases in CO2 in atmosphere leads to
- increase in ocean acidity
- above 490 ppm enhances coral loss, we are at 406 ppm and it increases 2ppm to 3 ppm each year so we will reach 450 in 20 years
pre-industrial atmospheric CO2
550 ppm
1.5 C world
Coral reefs will decline by 70-90%
2C World
virtually all (>99%) coral reefs will be lost
