Biome Travel Blog: Marine Pelagic

The Marine Pelagic Biome is a vast realm of open water. The oceans cover 70% of the earth's surface. This biome covers 3,500 feet below the sea surface. The most obvious difference for organisms living in the sea is that the oceans are wet. In water sound travels faster than in air. Sand covers the ocean floor. Marine organisms have to deal with extreme pressure when they go to great depths. When the pressure gets higher, the biodiversity is lower because there is limited food, the temperature drops and there is less light. Marine organisms are faced with a challenge as they swim through different areas to deal with differing levels of salinity in the water. The ocean also is always moving with its constant currents and surface winds. 

Abiotic and Biotic Interactions: Sunlight affects the amount of algae growth. Plants underwater take in carbon dioxide and release oxygen.

There are 5 different zones to the Marine Pelagic Biome:

Epipelagic Zone (First 500 ft below the surface)- Sunlight Zone

This zone has only cyanobacteria and phytoplankton in it. It receives enough light for the tiny organisms to go through photosynthesis. At night, zooplankton rise toward the surface to feed on algae and bacteria. Most predators, both invertebrate (copepods) and vertebrate (fish) feed at night. The carnivores hunt by sight, so because of natural selection, zooplankton are transparent. Fish that come up to eat are dark on top and light on their bellies so predators don't come up and eat them. Many marine animals come up here, from plankton to great blue whales. 

Blue Marlin Photo by Tony Arruza/Corbis

Mesopelagic Zone (660-3,300 ft)- Twilight Zone

The temperature varies from 68 F- 39 F based on what part of the world you are at. This zone is known as the twilight zone because it does not have enough sunlight for photosynthesis. Fish in this zone have light producing organs and gas filled bladders to help them control buoyancy. Predators have upward-oriented eyes and mouths. Examples of animals in this zone: swordfish, squid, eels, cuttlefish

Cuttlefish Photo by Wolcott Henry

Bathypelagic Zone (3,000-8,000 ft)- Midnight Zone 

The average temperature is 39 F. This zone has the highest diversity of organisms. Fish here are black and have an antennae to help with buoyancy. Bioluminescence is important for species and gender recognition, luring prey, and confusing predators. There are no plants because there is no sunlight. 

Organisms in this zone: Viperfish, frill shark, squid, whales, octopus

Sponges, brachiopods, sea star

Octopus Photo by Espen Rekdal

Abyssopelagic Zone (13,123 to 19,685 ft)- Bottomless Abyss

This area has immense pressure and constant cold (35-37 F) Animals here are able to withstand the pressure (black swallower, deep-sea anglerfish and the giant squid) Some of these creatures have underslung jaws to sift through the sand to catch food. 

Deep Sea Anglerfish from Disney's Pixar "Finding Nemo"

Hadopelagic Zone (20,000 ft to the bottom of the ocean)- Hades/Greek Underworld

This zone has low population and low diversity of marine life. The most common organisms here: jellyfish, viperfish, tube worms, and sea cucumbers. 

Viperfish Photo by Danté Fenolio

These zones all work together because the animals eat the other animals in the zone above them. It is a circle of life. 

Producers: Phytoplankton and aquatic plants (seaweed and algae)- Every species in the marine biome need organic carbon to survive and these tiny organisms produce it. Phytoplankton make their own energy by using photosynthesis. 

Consumers: 

Herbivores- Zooplankton- eat the phytoplankton and invertebrates (like sea urchins) and other fish eat seaweed. 

Carnivores- Small carnivores (like sardines) eat herbivores (like zooplankton), but serve as a meal for bigger animals; Top predators (like sharks, tuna, seals and birds) eat the small carnivores.

Decomposers: Hagfish, worms, fungi and bacteria

Human Influence: We eat fish.