The Open Ocean
The Pelagic Zone! The open ocean is called the pelagic zone.!
Epipelagic! We will focus on the top 200 m or 650 feet called the epipelagic zone.!! The photic zone is to a depth where light no longer reaches.!
The Epipelagic The epipelagic zone is divided into! two main regions. The continental shelf is the area near the shore and the area away from the shore is called the oceanic part.!
Plankton Like all other ecosystems the! epipelagic zone is fueled by solar energy. The microscopic to small organisms found drifting with the current here are the primary producers called plankton.!
Examples of Plankton
How to Study Plankton! Planktonic organisms are very small and hard to study. They are trapped by plankton nets or by pumping water through filters.!
Phytoplankton vs. Zooplankton! Phytoplankton are very small organisms that perform photosynthesis while zooplankton are small organisms that feed on other planktonic organisms.!
Importance of Zooplankton Zooplankton eat phytoplankton or! other zooplankton and are the base of the food chain in the ocean. They are food for everything for small fish and clams up to the largest whales. These animals eat by filter feeding.!
Filter Feeding Animals
Protozoan! Protozoan are small enough to eat the phytoplankton but big enough to get eaten. Without them, most of the nutrients found in the phytoplankton would go unutilized.!
Copepods Copepods are the most numerous! animals on Earth. They are practically found everywhere in the ocean, from the coldest waters of the poles to the warm clear waters of the tropics.!
Krill! Krill are members of the zooplankton. They are shrimp-like in their structure and can be found in huge dense swarms in slightly colder water.!
Salps! These are members of the planktonic community that are non-crustaceans. They filter out the plankton by pumping water and catching the plankton in a mucous net.!
Arrow Worms! Arrow Worms feed on copepods and are important predators of the zooplankton. They are also prey for many animals in the epipelagic.!
Haloplankton vs. Meroplankton! Haloplankton are organisms that spend their entire life in the plankton.!! Meroplankton are organisms that spend a portion of their life in the plankton either as larvae or as adults. Examples include; sea anemones, some crustaceans and corals.!
Planktonivores! These are organisms that eat members of the planktonic community. These range from small fish like herring and anchovies, invertebrates like squid, birds like penguins and larger animals like whale sharks and many baleen whales like the blue whale. Whales will filter the small organisms with the tough hairlike structures in their mouth.!
Baleen
Lantern Fish! Lantern fish spend their days at the bottom and will come up at night to feed on small members of the planktonic community.!
Living in the Epipelagic A major problem for organisms in the epipelagic zone is that their bodies are denser than the ocean water they live in. If they have a shell or a skeleton life is even harder because they are heavy.!
Phytoplankton in the Photic Zone Photosynthetic algae CANNOT sink or be brought down to deeper water because they rely on the sun for an energy source. Without enough sunlight, the algae cell will die.!
Staying Afloat To keep from sinking, planktonic organisms have two choices:! 1. Increase resistance to sinking! 2. Increase buoyancy!
Increase Resistance The speed an organism sinks depends on the resistance or drag the water has on the organism. Organisms can increase the drag by being FLAT or having SPINES.!
Increase Buoyancy Here they are not looking for resistance to sinking, they are looking for a way to float. They may use lipids which are lower in density to help them stay afloat. Diatoms are an example of this method. Cyanobacteria use pockets of gas to help them float.!
Animals That Swim Animals that swim have other adaptations. They include swim bladders/oily livers and pectoral fins. Fish have a unique internal structure called a swim bladder which helps them stay afloat in the water column. This is like an internal swimmy. It is located slightly below the center point of the body, so that explains why when a fish dies it goes belly up.!
Belly Up
Disadvantages of a Swim Bladder For all of the good a swim bladder does for a fish there are also some drawbacks. Gasses change volume under different pressures. If a fish changes it depth too fast, the swim bladder may expand or explode.!
Oily Liver/Fins Sharks use oily livers and fins to help stay up in the water column. The liver has lipids which are less dense than water and the pectoral fins act like a plane s wings providing lift.!
Jellyfish Jellyfish have a number of strategies to help stay afloat in the water column. Some are considered neuston. That means that they live near the surface but remain underwater.!
Portuguese Man-of- War Some jellyfish have a portion of their body that sticks up out of the water. These are known as pleuston. These include the Portuguese Manof-War jellyfish. They use a gas filled sac and may move with the current or use it as a sail and move with the wind.!
Floating Sea Slugs Sea slugs have the ability to float up into the water column. They do so by swallowing air bubbles which makes their density decrease so they can float.!
Ocean Insects The water strider is the only insect that lives in the open ocean. Unfortunately, it cannot swim, so if it finds itself under water, it will die.!
Sense Organs Life in the epipelagic is very challenging and many animals may be predators but they are also prey. It is important that they have finely tuned sense organs that help them survive.!
Eyes There is plenty of light in the epipelagic zone. Because of this, eyesight is very important. Most organisms in the epipelagic have excellent eyesight.!
Lateral Line Fish have another remote sensing system called a lateral line. This runs the length of the fish and can detect vibrations to help hunt as well as avoid being eaten. This is also how fish can tell the proximity of other fish within the same school.!
Schooling
Echolocation Echolocation is a remote sensing system where animals like dolphins and whales send out vibrations that bounce back off of prey and allow them to locate it, even in the dark or murky water.!
Coloration Protective Coloration-This is how epipelagic fish use camouflage to blend in. Some, like jellyfish are clear, while other like the barracuda simply disappear with their shiny skin.!
Counter-Shading This is the most common coloration of fish in the epipelagic. Fish are dark on the top so you can t see them when you look into the water. The are white on the bottom so you can t see them when you look up from the bottom.!
Streamlined Bodies Fast swimming fish need a sleek body plan with strong muscles. Tuna are perfect for this type of swimming. Their tail must also have a crescent shape.!
Myoglobin Myoglobin is a protein found in the deep red muscles of swimming fish. The muscles with this protein can store a lot of oxygen and are capable of swimming fast for long distances.!
Superfast Swimmers Sailfish are amazing swimmers. It does not look possible with that giant sail, but when they need speed they can fold it down.!
Flying Fish Flying fish are preyed upon by many fish in the ocean. To avoid predation, they jump out of the water and use their large pectoral fins to glide or fly just above the surface of the water.!
Vertical Migration Many fish will live the days at a great depth (more than 200 m) to avoid being preyed upon. They move nearer the surface at night to feed. At this time they are less likely to get eating by hungry predators.!
Food Web in the Plankton
Energy Transfer Most of the organisms and energy in the epipelagic food web is found in the phytoplankton and zooplankton. As you move up, the amount of available energy and number of organisms decreases.!