OCEANIC LIFE ZONES

Ocean Zonation There are 2 main groups: Pelagic – referring to water column Benthic – referring to the sea floor These groups are subdivided based on depth.

Overview of the Ocean Life Zones Horizontal Zones Littoral Zone Bathyal Zone Abyssal Zone Vertical Zones Sunlit Zone Twilight Zone Bathyal Zone Abyssal Zone

Horizontal life zones Littoral Zone – The shallow water area between high and low tides. Bathyal Zone (Neritic) – The area of the continental margin between the low tide line and the edge of the continental shelf. Abyssal Zone (Oceanic) – The deep ocean beyond the continental margin.

Horizontal Zones Diagram

Vertical Zones Sunlit Zone – (epipelagic) Extends from the surface of the ocean to a depth of 200 meters. Twilight Zone – (mesopelagic) the area of the ocean between 200 meters and 1,000 meters. Bathyal Zone – (bathypelagic) extends from 1,000 meters to 4,000 meters. Abyssal Zone – (abyssalpelagic) the area of the ocean that is deeper than 4,000 meters.

V Z E O R N T E I S C A L

Vertical Zones, Life and Light Sunlight is the energy basis for nearly all marine ecosystems and is therefore critical for life. The Sunlit Zone receives large amounts of sunlight. As a result many of the oceans organisms thrive here. This the area most of our seafood comes from.

Vertical Zones, Life and Light Twilight Zone – an area of the ocean that receives some light but is darker than the sunlit zone. Some fish and other organisms live here. Bathyal and Abyssal Zones are in complete darkness. Life forms in these zones contain tube worms, lantern fish, angler fish, as well as other forms of life.

Types of Oceanic life Plankton – float near the ocean surface. There are two types: phytoplankton, plantlike and zooplankton, animal like. Plankton are moved at the mercy of ocean currents Benthos – Organisms that live on the ocean floor. Nekton – Organisms that can swim.

Plankton or Nekton?

Benthos

Producers Producers – Organisms that capture energy from sunlight and fix this energy into their tissues. Eelgrass

Planktonic Algae Many algae are microscopic

Phytoplankton Phytoplankton are the most abundant producers in the ocean and are said to be the basis for marine food webs. Phytoplankton produce approximately 80% of the worlds oxygen.

Phytoplankton bloom in the Bearing sea

Diatoms Single shelled yellow-green algae. Its two shells fit together like a lid over a box. They can live alone or in colonies. They come in many different shapes and sizes. When they die they sink to the bottom to help form the ocean floor.

Dinoflagellates Dinoflagellates are bioluminescent. They have spinning flagella. Blooms produce toxins that kill finfish and shellfish. (be careful !!!)

Dinoflagellate blooms

Consumers Consumers – Organisms that capture their energy by eating other organisms.

Plankton continued… Zooplankton eat phytoplankton and follow them through the water column. Haloplankton- Zooplankton that spend their entire lives as zooplankton. Meroplankton- Temporary plankton such as eggs and larvae.

Zooplankton

Ways plankton stay afloat Spikes or other projections help distribute the weight over a larger surface area. Some produce oil sacs which help float. Some produce air filled sacs to help float. WHY DO THEY NEED TO STAY NEAR THE SURFACE??? LIGHT

Seasonal Population Variations Seasonal populations occur because of the complex nature and availability of nutrients and light, temperature and predators. In Nova Scotia we have blooms in spring and fall. Daily movements occur as some sink to deeper levels to avoid the midday sun. They move up in the morning and evening. Zooplankton follow the phytoplankton…