Background. Tropical Communities. Worldwide distributions. Main Players. Coralline Algae

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1 1 Tropical Communities 2 Background Occupy less than 0.2% of planet, yet Have upwards of 5% of all species Use 50% of CaCO 3 and with it, CO 2 to build reefs; around 700 billion kg/year Very productive areas in a desert, extremely diverse 3 Worldwide distributions 4 Main Players Hermatypic Corals- with zooxanthellae; these are the reef building corals Cnidaria, class Anthozoa, order Scleractinia Calcareous Algae- provide most of the cement that holds reefs together; also large producer of CaCO 3 in their own right Reds and Greens Others: Fish, inverts, fleshy algaes 5 Coralline Algae 6 Halimeda sp. Produces most of the sand in reef areas Others cement the coral reefs together 1

2 7 Chuck does it again ,283 m- hit volcanic rock ~60 myo Types of Reefs 8 Major Physical Factors 1. Temperature- Limited to 20 C coral or zooxanthellae? 2. Depth- Must be <70 m, most <25m 3. Light- Need adequate illumination for photosynthesis 4. Salinity- Need narrow range ppt, absent in FW areas 5. Sedimentation- Decease light, cover coral 6. Wave action- Often in high energy areas, bring in O 2 and food, remove sediment 7. Emergence- Upper bound is air interface, no higher than low tide, can only handle a few hours 9 Physical Factors 10 Low tide exposure 11 Which is NOT a major factor for coral health and growth A. Amount of Sunlight B. Clarity of the water C. Adequate food in the plankton D. Sedimentation E. Proper temperature 12 Types of Coral 2

3 13 Day vs. Night 14 Figure Contracted/relaxed 15 Anatomy of a polyp 16 Corals are Farmers Plankton can only account for 5-10% of total food requirements 17 Zooxanthellae 18 Species Interactions Are nitrogen limited Host Factor Competition Interspecific battles between corals for the sun Coral vs. Algae- mediated by herbivores Coral vs. Cryptofauna Predation Predators of coral- fish, sea stars, mollusks, crabs, etc Grazing Short algal turf eaten by fish and urchins Remove urchins = 10x increase in algae = Coral kill 3

4 19 20 Figure Over fishing on reefs removes herbivorous fish (and others) Diadema increase in number and control the algae But if you have die offs of the Diadema algae takes over and corals die Jamaica- Hurricane in 1980 still not recovered 21 Fish can influence coral in many ways Predators Herbivores that control the algae and other inverts Fertilizers Fish feed in one area, seek refuge in another and poop all day / night long 22 Reef Fish Huge diversity Large amount of habitat heterogeneity Within coral, overhangs, caves, sand, etc Day/ night differences in species assemblages Still not enough to account for diversity of fish observed might it be related to recruitment? Why are there so many fish? 23 Bioerosion Cryptofauna destroys coral skeletons Sponges, echinoderms, mollusks, others. Coral build 206 tons/ year; Bioerosion = 163 tons/year 24 Threats to Coral Reefs Storms, El Nino, industrialization Coral Bleaching El Nino- water temps +2 to 4 C- some reefs >90% dead 4

5 25 Palau 26 Marine Lakes Land-locked marine ecosystems Greatly simplified flora and fauna H 2 S- Hydrogen Sulfide layer Core Points- Reefs What are the importance of reefs? Where are they found and why? What living things define them? What physical factors influence them? How are they formed? What sorts of ecological interactions are important for their health? 29 Mangroves vs. Mangal 30 Adaptations Sheltered areas, no waves, high sediment, mud (anoxic) Physiological Convergence Subtle physiological adjustments regulate responses to salinity, bright tropical sun, variable and often low nutrient availability, flooding, soil anoxia, and tidal action. Ultrafiltration process, salt glands in leaves, cell expansion, and increased leaf succulence, thick cuticle, and differences in xylem anatomy Mangroves need fresh water and must maintain tissue water potential below the osmotic potential of the very salty substrate. Water-Use efficiency enables transpiration, withdrawing water slowly from the soil and slowing the buildup of salt around the roots 5

6 31 Mangrove Lifecycle 32 Aerial Roots Support and Gas exchange in anoxic sediments- shallow roots and Pneumatophores What is it like in the understory? 35 Mangrove Distribution 36 6

7 37 38 Mangroves and Costal Protection 39 Mangroves and Aquaculture Honduras 40 Core Points- Mangroves What are mangrove communities? Where are they found? What special adaptations do the plants have? What are some of the ecological interrelations in the mangal? What are some human impacts on the mangal? 7