Coral Reef Biology and Ecology Lecture Slides PDF

BI2MBC1 – Marine Biology and Conservation The Biology and Ecology of Coral Reefs  Coral Biology, Distribution Importance Lifecycle and of Coral reefs of Coral Reefs Forms Threats to Coral Reef...

BI2MBC1 – Marine Biology and Conservation The Biology and Ecology of Coral Reefs  Coral Biology, Distribution Importance Lifecycle and of Coral reefs of Coral Reefs Forms Threats to Coral Reefs Coral Reef (Bleaching, Conservation Acidification …) Lecture Plan – Learning Outcomes The Greek word “cnidos” means “stinging nettle” ylum Cnidaria (±3000 species); general characteristics: sue level of organisation, diploblastic (2 tissue layers; ecto- and endoderm) dial symmetry ve specialized stinging structures called cnidae ve only one opening to the body cavity / digestive cavity ve to head, no centralized nervous system (only a nerve net) discrete gas exchange, excretory or circulatory systems creted Calcium Carbonate (CaCO3) skeletons achieved by binding of CO2 with Ca2+ ions in seawa Two Sub-Classes: Octocorallia (soft coral) V Hexacorallia (hard coral or Scleractin Distribution of coral reefs in the world 20 indicated in dashed lines Wells (1957) noted that no reefs develop below 18 Optimal 23-25 West coast of Africa and S. America – absence of coral Genera of reef corals (Miller, 2018) Coral triangle in Indo-Pacific – Philippine Sea Biodiversity of the Philippines Coral Triangle considered centre of global marine biodiversity Philippines lies to the north of the triangle.: 7100 islands 25000km2 reef Philippines has been further labelled as the ‘the center of the center’ of marine biodiversity (Carpenter People and the Sea 12 Coral distribution 6 major Limiting Factors Temperature Depth Light Salinity Sedimentation Emergence into air Growth rate of the massive coral Porites lobata versus depth (Grigg, 2005) Hermatypic vs. Non-Hermatypic Corals Hermatypic Corals (a): Corals that form large colonies called reefs. a. Brain coral (Diploria) b. Mushroom coral (Fungia) Ahermatypic Corals (b): Corals that are solitary or form small colonies (often lack zooxanthellae and do not help build reefs). Consider Deep Sea Corals  Coral Growth Forms © 2019 McGraw-Hill Education. 14-18  Environmental Gradients along reef control species distribution Wave energy declines with depth Light energy declines with depth Temperature declines with depth Sedimentation increases with depth Coral Biology and Ecology Corallite or Cup  1 2 4 1 3 6 5 20 um 2 um Coral Reefs Have High Primary Productivity Coral Reef primary production ranges from 1500 to 5000 g of C/m2/yr Open tropical oceans 18-50 g of C/m2/yr This makes Coral Reefs one of the most productive communities on earth! Polyps and Zooxanthellae Mutualism Benefits of the coral–zooxanthella symbiosis Nutritional benefits Autotrophy, arising from the translocation of energy-rich photosynthetic products (e.g. glycerol, glucose) from zooxanthellae to the coral; these products support coral respiration, tissue growth, gamete production and survival. Enhanced availability and retention of nutrients, arising from: – capture of planktonic food by the coral and the supply of excretory waste (containing nitrogen and other elements such as phosphorus) to the zooxanthellae. – nitrogen conservation, due to the preferential use of energy-rich photosynthetic products rather than amino acids for coral respiration. – nitrogen recycling, arising from uptake of the coral’s nitrogenous waste by the zooxanthellae, its incorporation into amino acids and their translocation back to the coral. Coral skeleton formation and reef accretion Light-enhanced calcification (i.e. CaCO3 deposition) and the provision of photosynthetically fixed carbon for the coral skeleton’s organic matrix. Fixed position in the water column and a favourable light regime for the zooxanthellae, due to the coral’s physical properties (e.g. branch orientation, light scattering by the skeleton or fluorescent pigments in the tissues), which optimize harvesting of downwelling light. Protection of zooxanthellae from planktonic grazers by the coral’s tissues. Detoxification of coral cells, via the uptake and utilization of potentially toxic nitrogenous (NH4 +) waste by the zooxanthellae. Supplementary O2 for coral metabolism arising from zooxanthellar photosynthesis. Supplementary CO2 for photosynthesis arising from coral respiration. Goniopora stokesi Polyp balls Climate Change impacts on Coral Increases in Increased Changes to Changing Ocean Sea level sea storm precipitatio ocean acidificatio rise temperatur frequency n, drought circulation n e and and run-off intensity Coral reefs very sensitive to changes in the ocean’s temperature Over 60% of the earth’s coral reefs may be lost by the  Coral Bleaching Occurs when corals become stressed They expel the zooxanthellae living in them They lose their color and become whitened Can be caused with warmer surface waters (maybe even by 1-2 degrees) Pollution can also be a cause Full recovery takes decades Coral bleaching Mass bleaching events in 1998, 2002, 2006, 2016, 2017, 2020-2022 were caused by unusually warm sea surface temperatures during the summer season. Bleaching in 2008 and 2011 was caused by an influx of freshwater. Increasing in occurrence and severity Coral can recover but needs time  Predicted rise of 15-95 cm in next century Coral growth will not be able to keep up Corals will be deeper and receive less sunlight Effects on coastal protection Sea level rise  Ocean acidification One-third of the carbon dioxide we produce ends up in the ocean. When carbon dioxide is mixed with water it creates carbonic acid. Human activities are making the oceans more acidic than they have been in hundreds of thousands of years. More acidic oceans will mean: Corals and animals with calcium shells and skeletons may grow slower (coral growth on the Great Barrier Reef has already declined 14 per cent since 1990)  Pollution Increased levels of fertilizer and agrochemicals 80% of marine pollution originates from the land Exponential increase of pollution in last decades Coral reefs are very vulnerable Explosion of invasive red algae – sunlight Overfishing of herbivorous fish Disease is another major factor limiting growth. Here is an example of elkhorn coral (Acropora palmata) infested by “white band disease.” Stony Coral Tissue Loss Disease Dynamite fishing  Coral reefs are found off the coasts of about 100 countries. Coral reefs are home to about 25% of all marine life. Coral: Among the most fragile and endangered ecosystems. Some Over the last few decades 35 million acres of coral sobering reefs have been destroyed. facts Reefs off of 93 countries have been damaged. If the present rate of destruction continues 70% of all coral reefs will be destroyed. As of now 2/3 of coral reefs are dying and 10% can no longer be recovered Coral Reef Conservation Hope on the Horizon! CNN Report Mineral accretion (limestone accumulation) Mineral Accretion Artificial Reef in Maldives https://research.reading.ac.uk/scenario/ Reefs are essentially massive deposits of calcium carbonate (CaCO 3) produced primarily by corals (Phylum Cnidaria, class Anthozoa, order Scleractinia) – Soft corals Alcyonacea (Octocorallia) Occupy 600,000 square miles of surface of Earth (0.17%) Greatest diversity per unit area of any marine ecosystem – the Rainforests of the Seas Estimates that 5% of all species on Earth (25% of marine life) live in Coral reefs Half the Calcium that enters world Oceans taken up and bound to Coral reefs as calcium carbonate Each bound Calcium atom requires a molecule of CO 2 – 700 billion kilograms of Carbon sequestered per year $375 billion annually in goods and services Coral Reef Facts and Figures