210 likes | 222 Views
Coral/algal Reefs IV. Variation and Alternative States. Variation in Florida Keys corals, 2005. Brandt, M. E. 2009. The effect of species and colony size on the bleaching response of reef-building corals in the Florida Keys during the 2005 mass bleaching event. Coral Reefs 28:911-924.
E N D
Coral/algal Reefs IV Variation and Alternative States
Brandt, M. E. 2009. The effect of species and colony size on the bleaching response of reef-building corals in the Florida Keys during the 2005 mass bleaching event. Coral Reefs 28:911-924. • Background • Summer & fall, 2005 – high SST in ne Caribbean • Mass bleaching documented • Methods • Monitor corals for 191 colonies in permanent quadrats
Why and what’s next? • Symbiont “clades” vary genetically • Corals can switch • Symbiodinium communities can vary across environmental gradients • Degree of flexibility is debated • Hosts (corals) also vary • Different fluorescent proteins for protection • Different abilities in heterotrophy • Coral structure affects the light environment
Will coral reefs respond to fast climate change? • Climate shifts • More peak temperature events • More extreme temperature events • Physiological response? • Evolutionary response?
Competitive dynamics • Exploitation competition (for light) • Upright, branching corals can shade massive corals • Encrusting algae can spread over corals • Interference competition (for space) • External digestion by some corals • “Sweeper” tentacles for some species • Hierarchy of competitive dominance • Algae easily overgrow most corals • Among corals Pocillopora is nastiest
Dynamics of predation on coral reef species • Coral-feeding fish are present but usually not devastating • Territorial damselfish create safe zones (up to 60% of surface area) • Coral-feeders have their own predators • Starfish, such as “Crown-of-Thorns” can be problematic • Population “outbreaks” can damage living corals
Dynamics of grazing on algal reef species • Urchins are major consumers (e.g., Diademaantillarum) • Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals) • Grazing can suppress competitively dominant algae (>90% removal) • Indirect effects can become important
Evidence for herbivorous fish indirectly helping corals R = redband parrotfish S = ocean surgeonfish Burkepile & Hay, 2010, PLoS One, 5 (e8963)
Mangrove /Mangal A tropical and subtropical boundary community
Questions: • Why are trees found in some ocean boundaries? • Aquatic/terrestrial • salt/freshwater • What are the characteristics of these ecosystems? • How is mangal important to marine ecosystems?
Definitions: • Mangrove • A type of tree that tolerates variation in inundation and salinity • Mangal • A community (set of species) on the marine fringe • Dominated by a special set of salt-tolerant trees • Includes many other, associated species, both of terrestrial and marine origins
Characteristics: very low wave action, with silty substrates (sometimes sand)
Extent: 2/3 – 3 /4 of tropical shores were fringed with mangal