OCEANIC LIFE ZONES

There are 2 major Ocean Zones: Pelagic – involves the water column Benthic – involves the sea floor These groups are subdivided into horizontal zones based on depth, and vertical zones based on coastal or open ocean areas.

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

Horizontal Zones Diagram

Horizontal Benthic Zone Littoral: the intertidal zone that is alternately covered and uncovered by the tides. Bathyl: covers the continental shelf. Abyssal: covers the continental slope down to deep ocean basins Hadal: the bottom of the deep sea trenches

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.

Vertical Zones epipelagic Extends from the surface of the ocean to a depth of 200 meters. mesopelagic the area of the ocean between 200 meters and 1,000 meters. bathypelagic extends from 1,000 meters to 4,000 meters. abyssopelagic 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

Types of Oceanic life phytoplankton = plant zooplankton = animal Plankton – float near the ocean surface. There are two types: phytoplankton = plant zooplankton = animal Nekton – Organisms that can swim purposefully. Benthos – Organisms that live on/in the ocean floor.

Phytoplankton 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 = the basis for marine food webs. Phytoplankton produce ~50 - 80% of the worlds oxygen.

Phytoplankton bloom in the Bearing sea

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

Zooplankton

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 differet 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 can kill finfish and shellfish.

Dinoflagellate blooms

How 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?

Seasonal Population Variations Seasonal populations occur with the availability of nutrients and light, temperature and predators. In NS 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 …and so on…