Coral/algal Reefs IV Variation and Alternative States

Variation in Florida Keys corals, 2005

Brandt, M. E 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: Background Background –Summer & fall, 2005 – high SST in ne Caribbean –Mass bleaching documented Methods Methods –Monitor corals for 191 colonies in permanent quadrats

Bleaching was correlated with heating

Bleaching prevalence varied among spp

Bleaching incidence varied with colony size

Why and what’s next? Symbiont “clades” vary genetically Symbiont “clades” vary genetically –Corals can switch –Symbiodinium communities can vary across environmental gradients –Degree of flexibility is debated Hosts (corals) also vary 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 Climate shifts –More peak temperature events –More extreme temperature events Physiological response? Physiological response? Evolutionary response? Evolutionary response?

Competitive dynamics Exploitation competition (for light) Exploitation competition (for light) –Upright, branching corals can shade massive corals –Encrusting algae can spread over corals Interference competition (for space) Interference competition (for space) –External digestion by some corals –“Sweeper” tentacles for some species Hierarchy of competitive dominance Hierarchy of competitive dominance –Algae easily overgrow most corals –Among corals Pocillopora is nastiest

Mix of coral polyp and algae

Algal overgrowth

Shading by Sargassum, chemical effects

Herbivores on algae

Dynamics of predation on coral reef species Coral-feeding fish are present but usually not devastating 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 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., Diadema antillarum) Urchins are major consumers (e.g., Diadema antillarum) Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals) Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals) Grazing can suppress competitively dominant algae (>90% removal) Grazing can suppress competitively dominant algae (>90% removal) Indirect effects can become important 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? Why are trees found in some ocean boundaries? –Aquatic/terrestrial –salt/freshwater What are the characteristics of these ecosystems? What are the characteristics of these ecosystems? How is mangal important to marine ecosystems? How is mangal important to marine ecosystems?

Definitions: Mangrove Mangrove –A type of tree that tolerates variation in inundation and salinity Mangal 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