Difference Between Benthic and Pelagic

Benthic vs Pelagic

Our atmosphere is divided into different atmospheric layers depending on the physiochemical properties of that particular zone, and many of us are quite familiar with those.

Similarly, any water body can be divide into different zones, which are demarcated by their own physical and chemical properties, as well as arbitrary boundaries exerted by human.

Any water body will have two distinct zones; benthic zone, which describes the layers closer to the bottom of the water body, and pelagic zone, which includes the free water column that interacts with the surface layers of a water body. Apart from their basic geospatial location difference, many other factors help us to differentiate between these.

What is Benthic Zone?

This is the layer, which you can find immediately above the bottom sediment of any water body. Referring to the sea, benthic zone start at the shoreline and extends into deep waters, away from landmass.

It is worth noticing that there isn’t a specified depth to this zone, as it could vary from few inches as in a stream to several 1000s of meters as in the open ocean.

The biotas that dwell in this zone are termed as benthos consists of organisms that have adapted to tolerate low temperatures and high pressure, as well as low oxygen levels found in this zone. Many of them have bottom-dwelling adaptations.

Since light cannot penetrate this depth, this zone lacks the ability to photosynthesis as its energy source. Main energy source of this zone consist of organic materials that drifts down the upper layers and this region is dominated by detritivores and scavengers.

What is Pelagic Zone?

Brief idea of this zone can be gained simply by referring to the Greek meaning of it, “open sea” and this zone is the uppermost layers of a water body, especially referring to the ocean, interacts directly with the atmosphere.

Physical and chemical properties of this zone vary greatly because of the vastness of this area, which extends from the uppermost waters down to the deeper layers near the benthic zone of a water column.

As the depth increases, favorable life sustaining features of the pelagic zone reduces, resulting in a decrease in the biota, as well. This zone can be divided into several sub layers that extend from the top to bottom.

They are light penetrating Epipelagic zone in which photosynthesis can take place, Mesopelagic zone, which doesn’t get enough light for photosynthesis and has lower dissolved oxygen levels, and lastly the bathypelagic zone, which doesn’t get light at all, and many of the creatures in this area has the potential to produce bioluminescence.

Most of the primary production in the water takes place in the uppermost epipelagic zone, and it is the layer with highest diversity.

What is the difference between Benthic and Pelagic?

  • Benthic zone is the layer closer to the bottom of a water body, whereas pelagic zone refers to the uppermost layers of a water body.
  • Organisms that live in the benthic region are coined as ’benthos’, and organisms found in the pelagic zones are referred as pelagic organisms.
  • Referring to the open sea, benthic zone is characterized by low temperatures, low dissolved oxygen levels, low/no light, and high pressures. However, there is a gradient of these in the pelagic zone from top to bottom.
  • If we compare the diversity in these zones, resource rich pelagic waters harbor higher diversity than the benthic zone that has lower resources.
  • Photosynthesis does take place in the epipelagic zone, but benthic zone does not get enough light for this.
  • Pelagic food webs are powered by photosynthesis whereas benthic communities are normally powered by detritus drifted from the upper layers.
  • No photosynthetic organism can be found in the benthic region; it is dominated by detritivores and scavengers. In the pelagic zone, photosynthetic organisms as well as active predators are dominant.
  • All most all the creatures in the benthic zone are bottom-dwellers or sessile animals whereas all the creatures in the pelagic zone are free-living.

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