© 2014 Pearson Education, Inc. Chapter 15 Animals of the Benthic Environment Rocky and sandy shores Coral Reef Deep Sea

© 2014 Pearson Education, Inc. Animals of the Benthic Environment- Overview Benthic communities include a variety of habitats. Corals need specific environmental conditions. Hydrothermal vents support diverse communities that rely on chemosynthesis.

© 2014 Pearson Education, Inc. Chapter 15 Coral Reefs What Organisms Are Part of the Coral Reef and What Are Their Adaptation? Reefs – shallow water communities restricted to tropics

© 2014 Pearson Education, Inc. Coral Reefs Most corals live in large colonies and have a calcium carbonate structure that provides protection. Polyps – individual corals Polyps capture prey with their nematocyst.

© 2014 Pearson Education, Inc. Coral Reef Distribution Corals are found throughout the ocean but coral accumulations called reefs are restricted to the shallow warm waters as shown above.

© 2014 Pearson Education, Inc. Conditions for Coral Reef Development 1.Warm seawater 2.Sunlight for zooxanthellae – symbiotic photosynthetic microscopic dinoflagellates in coral tissues 3.Strong waves or currents 4.Clear seawater 5.Normal salinity 6.Hard substrate

© 2014 Pearson Education, Inc. Symbiosis of Coral and Dinoflagellate Coral reefs made of algae, mollusks, foraminifers as well as corals Hermatypic (reef building) coral – mutualistic relationship with dinoflagellates –Photosynthetic dionflagellates provide food –Corals provide nutrients –90% of the nutrition of the corals is provided by the zooxanthellae.

© 2014 Pearson Education, Inc. Coral Reefs Other reef animals with symbiotic relationships Mixotrophs – derive part of nutrition from marine algae –Include foraminifers, sponges, and mollusks

© 2014 Pearson Education, Inc. Coral Reef Zonation The zonation is caused by the following conditions: 1.Sunlight 2.Wave energy 3.Salinity 4.Water depth 5.Temperature Each zone will have a specific type of coral and organisms. Many fish species inhabit shallow waters near reef Reef lagoon habitat for other animals

© 2014 Pearson Education, Inc. Coral Reef Zonation Coral Reefs show vertical and horizontal zonation.

© 2014 Pearson Education, Inc. This is a non-reef building coral. It is a soft coral with small feeding polyps extended from the branching network. Corals cover less than half the surface of the oceans and are home to 25% of all marine species.

© 2014 Pearson Education, Inc. Importance of Coral Reefs Largest structures created by living organisms –Great Barrier Reef, Australia, more than 2000 km (1250 miles) long 1.Great diversity of species 2.Provide shelter, food and breeding grounds for many marine fish 3.Important tourist locales 4.Fisheries 5.New medical compounds 6.Reefs protect shorelines

© 2014 Pearson Education, Inc. 1. Nutrient Levels Fishing, tourist collecting, and sediment influx due to shore development harm coral reefs. Sewage discharge and agricultural fertilizers increase nutrients in reef waters. –Phytoplankton overwhelm at high nutrient levels –Bioerosion of coral reef by algae-eating organisms Destruction of Coral Reefs Hermatypic corals thrive at low nutrient levels

© 2014 Pearson Education, Inc. Crown of Thorns Phenomenon Sea star eats coral polyps Outbreaks (greatly increased numbers) decimate reef Destruction of Coral Reefs 2. Predators

© 2014 Pearson Education, Inc. 3. Diseases Coral bleaching – loss of color in corals –Symbiotic zooxanthallae die, leave, or become toxic –Bleached coral lacks nourishment from algae Linked to climate changes Destruction of Coral Reefs

© 2014 Pearson Education, Inc. Coral Bleaching Some causes –High surface water temperatures –Elevated UV levels –Decrease in sunlight-blocking atmospheric particles –Pollution –Salinity changes –Disease

© 2014 Pearson Education, Inc. Other Diseases Causes still under investigation –Bacteria, viruses, fungi –Human population stressors –Increased nutrients and turbidity –Environmental stress Black Band disease

© 2014 Pearson Education, Inc. Coral Reefs in Decline 30% healthy today, 41% healthy in 2000 One third of corals – high risk of extinction Humans – greatest threat Other threats –Hurricanes –Global warming –Floods –Tsunami