Coral Reefs and Lagoons The 3D Theory of Atoll Formation The protective role of reefs and the causes and effects of reef erosion Reconstructing the history of Reefs

Important engineers of biodiversity “Rain forests of the ocean” Cover less than 1/10% of ocean floor Habitat for 25% of all marine species

2. Does coral perform photosynthesis? POP QUIZ 1. Are corals plants? No - coral is an animal. 2. Does coral perform photosynthesis? No - animal cells do not have chloroplasts. 3. What is the process that animals perform to survive called? RESPIRATION

What does this mean for organisms that live symbiotically and can perform both photosynthesis (zooxanthellae) and respiration (zooxanthellae and coral)? Sunlight Glucose Heat Carbon Dioxide Oxygen Water Waste (nutrients) Nutrients Water Energy transfer: In Photosynthesis and Respiration, energy changes forms but does not get used up. It begins as light energy, then is converted into chemical energy during photosynthesis (energy is stored in food), and is released into the atmosphere as heat when respiration is complete. Matter: Matter is anything with mass. All matter is recycled in the system.

Which type of symbiotic relationship do coral and zooxanthellae exhibit? MUTUALISM They both benefit from the interaction in the following ways: CORALS receive energy from zooxanthellae, which is stored in the glucose that the zooxanthellae produce during photosynthesis. The rest of their energy (and nutrients) is obtained from their food, zooplankton, which they catch with their stinging tentacles. Corals need lots of energy to reproduce new individuals that can add to the size of a reef. ZOOXANTHELLAE receive protection from a coral’s hard skeleton and stinging cells. Zooxanthellae also use some of coral waste as nutrients. More interesting information about the relationship: Reef-building corals get their coloration from the zooxanthellae in their tissues, so it is difficult to identify coral species based on their coloration. When corals are stressed, they release their zooxanthellae and become all white (what we know as coral bleaching).

Zooxanthellae live within the tissue of the polyp. Corals share a mutualistic relationship (mutually beneficial) with zooxanthallae (unicellular algae). Zooxanthellae live within the tissue of the polyp. They can comprise up to 75% of the polyp’s body weight. FIGURE 12.17d: Mutualism.

Zooxanthellae Zooxanthellae are dinoflagellate algae and live in coral tissue. They provide nutrients such as sugars and oxygen that are essential for the production of calcium carbonate (coral reef skeleton). Provide coral with beautiful coloration (without them corals are clear or white = coral bleaching). More than 50% of the corals’ nutrients are derived from photosynthetic products produced by zooxanthellae.

Zooxanthellae Unicellular yellow-brown dinoflagellate algae which live in the gastrodermis of corals Provide corals with food in the form of photosynthetic products Live in coral’s tissues at a density of 1million cells/cm² Due to need for light, they only live in ocean waters <100 m Recently found that there are 10 different species that live in corals

What are Corals? Start their lives as free-swimming young Once they find a hard bottom, they attach themselves and quickly change into a polyp Coral polyp splits in 2 and makes an identical copy of itself Form a colony and secrete a hard calcium carbonate skeleton Each polyp makes a small skeletal cup which aids in feeding As coral colony grows, it secretes new skeletal material on top of the old Over thousands of years of accumulation, a coral reef is formed

Coral Reefs Coral Reefs are most diverse and productive communities on Earth. They are referred to as the “Tropical Rainforest of the Ocean” Found in warm, clear, shallow waters. Provide zooxanthellae with a protected environment, steady supply of carbon dioxide, and nitrogen.

Common Reef Fishes FIGURE 12.23a: Grouper. FIGURE 12.23d: Lion Fish. Courtesy of Mohammed Al Momany/NOAA FIGURE 12.23d: Lion Fish. © Doxa/ShutterStock, Inc. FIGURE 12.23b: Angel fish. © Ian Scott/ShutterStock, Inc. FIGURE 12.23e: Parrot Fish. © Wolfgang Amri/ShutterStock, Inc. FIGURE 12.23c: Soldier Fish. © stephan kerkhofs/ShutterStock, Inc.

Corals can be either solitary or colonial. Coral reefs flourish in water that is warmer than 20º C They are found in tropical and subtropical latitudes. Corals cannot survive in fresh, brackish water or highly turbid water. Corals do best in nutrient poor water. They are easily out-competed by benthic filter feeders in nutrient-rich water (where phytoplankton and seaweed are abundant).

Symbiotic Relationship between Corals and Zooxanthellae Provide Corals with food in the form of organic matter Corals Provide zooxanthellae a safe place to live Excrement is taken in by dinoflagellates and are recycled

FIGURE 12.17b: Coral Structure. Corals belong to the phylum Cnidaria. The animal is the coral polyp. The corallite is the exoskeleton formed by the polyp. Coral Reproduction FIGURE 12.17a: Coral Polyps. FIGURE 12.17b: Coral Structure. Courtesy of Brent Deuel/NOAA

Coral Bleaching Coral Bleaching is a stress condition in coral reefs that involves the breakdown of zooxanthellae.

Factors Affecting Coral Bleaching Temperature: Fluctuation of low and high sea temperature accompanying intense upwelling. Winter: Change from -3 C to -5 C for 5 to 10 days Summer: Change from 1 to 2 C for 5 C to 10 days (more common) Salinity: Zooxanthellae are sensitive to low salinity due to precipitation and runoff. Therefore, they tend to live near shallow, clear waters (no deeper than 100m) with plenty of sunlight. UV radiation: High levels of photosynthesis leads to high amounts of nitric oxide production by zooxanthellae.

More Factors Natural Phenomenon: Violent storms, flooding, ENSO (El Niño Southern Oscillation), predatory outbreaks, and tsunami are devastating to coral reefs. Anthropogenic Phenomenon: Overexploitation, overfishing, increased sedimentation, and nutrient overloading. Map of coral bleaching over the past 15 years, and major coral bleaching events (yellow dots). www.iper1.it/.../ index/cerca/reef

Research Study done by Rosenberg and Ben-Haim (2002): The actual agent leading to bleaching of hard coral, Oculina patagonia, is caused by an infectious bacteria called Vibrio shiloi. Purpose of the experiment was to test the growth of bacteria within two different sea water temperatures in an aquaria environment. Results showed bacteria produced an extracellular toxin that blocked photosynthesis within the zooxanthellae The toxin would bind to the algal membranes and prevent the ammonia and lead to the destruction of pH gradient across the thylakoid membrane.

Research 2 Study done by Rosenberg and Falkovitz, 2004: Similar study done with Oculina patagonica, hard coral and Vibrio shiloi, bacteria. Results showed the inability of the bacteria to bleach the coral at cold temperatures due to increased resistance of the coral and in hot temperatures the bacteria was able to produce. Laboratory experiment demonstrated high temperature would cause bleaching by the bacteria. Temperature at 29 C there was rapid and complete bleaching At 25 C bleaching was slower and incomplete Below 20 C there was no bleaching, even with large amounts of the bacteria exposed.

Conclusion Both studies showed the bacteria was unable to grow in cold temperatures. A theory was the zooxanthellae provided protection to the coral from the intracellular bacteria. Based on an alternative explanation of the zooxanthellae production and concentration of oxygen to the coral was toxic to the bacteria. Results suggested the zooxanthellae are essential in providing nutrients to coral, as well as, providing protection to coral from the bacteria, V. shiloi. Future studies are to be done on the symbiotic relationship between zooxanthellae and coral reefs. Human interaction should also be taken in consideration.

Assignment Find a full text, peer reviewed article of an experiment involving “coral,” “zooxanthellae” and “symbiosis”. Read your article, and make notes (or highlight) key passages that help you understand the research. Email me the article (link) or print and turn in– we will have a class discussion on the research. 23

Global Warming Global warming is a major concern: If temperatures continue to increase to 1-2 C, for the next 20 years there will be mass coral bleaching worldwide. The high seawater temperature elevation will affect over 95% of the species living within the coral and lead species to become extirpated or extinct.

Vocabulary Check Zooxanthella (zooxanthellae = plural): A single-celled algae (dinoflagellate) that can often be found living within the tissue of certain Cnidarians, especially reef-building corals. Ecology: The study of how organisms interact with each other and their physical environment. Barrier Reef: A reef that is parallel to the shore and usually separated from land by a lagoon. Symbiosis: A close relationship between two organisms. Many symbiotic organisms share a living space. Symbiont: Usually the smaller organism in a symbiotic relationship. Host: Usually the larger organism in a symbiotic relationship. Mutualism: A relationship between two organisms (host and symbiont) in which both benefit from the interaction. Parasitism: A relationship between two organisms in which one organism benefits at the other organism's expense. Commensalism: A relationship between two organisms in which the host neither benefits nor is hurt by the relationship. Producer: An organism capable of making its own food. Photosynthesis: Process of using energy in sunlight to convert water and carbon dioxide into carbohydrates (sugar, energy) and oxygen. Chlorophyll: A specialized pigment found in producers that allows them to attract and absorb sunlight rays. Chloroplast: The organelle where photosynthesis takes place in a plant or algal cell. Inputs: Resources organisms use to function. Matter: Anything with mass. Energy: Anything that can be converted into and measured as heat.