1.3 Marine Provinces

In section 1.2 we learned about the regions that make up the . So before we leave this topic, we will look at some of the other ways we can categorize the ocean environments.

The first major distinction is between the pelagic and benthic zones. The zone refers to the water column, where swimming and floating organisms live. The zone refers to the bottom, and organisms living on and in the bottom are known as the .

The pelagic zone is divided into two provinces: the province corresponds to all of the water from the low tide line to the shelf break, while the province represents all of the other water in the open ocean regions.

The oceanic province is divided into depth zones (Figure 1.3.1):

  • 0-200 m is the zone (“epi” = “upon”, as in on top of the pelagic zone). This is the region where enough light penetrates the water to support (see section 7.3), so it is also called the or zone.
  • 200-1000 m is the zone (“meso” = “middle”). There is some light here, but not enough for photosynthesis, so it is called the , or the .
  • 1000-4000 m is the zone (“bathy” = “deep”). There is no light at these depths, so it is referred to as the zone. About 75% of the living space in the ocean lies at these depths or deeper.
  • 4000-6000 m is the or abyssalpelagic zone, which extends to the seafloor in most areas.
  • 6000 m and below is the or hadalpelagic zone (named for Hades or “hell”). This refers to the water in deep ocean trenches.

Inhabitants of these regions are referred to according to their habitat, for example mesopelagic fish, or epipelagic squid.

Figure 1.3.1 The major benthic and pelagic oceanic divisions (K. Aainsqatsi at en.wikipedia [Public domain, GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0], via Wikimedia Commons).

The environment is also divided into zones, most of which correspond to the pelagic divisions:

  • The zone lies above the high tide line. Also called the spray zone, it is only submerged during storms or unusually high waves.
  • The zone is the region between the high and low tides. Thus it is also referred to as the zone.
  • Below the littoral zone is the (shelf) zone, extending from the low tide mark to the , essentially covering the .
  • The zone extends along the bottom from the shelf break to 4000m, so it generally includes the and .
  • The zone is found between 4000-6000 m, including most of the . The abyssal zone represents about 80% of the benthic environment.
  • The zone includes all benthic regions deeper than 6000 m, such as in the bottom of trenches.


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Introduction to Oceanography Copyright © by Paul Webb is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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