Question

Zonation in benthic community structure is common, particularly in intertidal systems. Describe patterns of zonation that occur across the tidally influenced zones of rocky shores, salt marshes, and estuarine habitats, using examples of specific organisms that might inhabit different zones or regions within the habitat in question. What are the causes of zonation in each habitat? How do zonation patterns differ between rocky intertidal and salt marsh habitats in particular?

Answer 1

Rocky shores : On Rocky shores, horizontal banding of creatures is obvious, thus called as intertidal zonation. Varying lunar-month tide levels or indicator species have been used to define these levels.

Organisms that habitat -

Low tide level - shore crabs

Mid tide level - conniwinks

High tide level - high shore barnacles

Salt marshes : Generally exhibit gradients from low to high marsh that correspond with elevation and the frequency of tidal inundation.

Organisms that habitat -

Low marsh - spartina

Mid marsh - salicornia

Upper marah - Juncus

Estuarine habitat : There is a wide range of habitats in an estuary. Close to the estuary or river mouth, the shore is usually sand. As the wave energy is not so strong, the sand is usually packed down, so it is unsuitable for intertidal animals.

Low tide - seagrasses

Mid tide - mud flats, mangroves

High tide - maritime forest

Alternating emersion and submersion are the primary causes of zonation on rocky shores. Various modifying factors such as exposure may greatly modify these zones.

Salt marshes zonation results from species-specific adaptations to physical and chemical conditions.

In estuaries, zonation is controlled by the environment near the sandbar and competition away from it.

The main difference in zonation patterns between rocky intertidal and salt marsh habitats is horizontal gradient on rocky shores and in salt marshes vertical gradient in seawater exposure.