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Rocky shore

Publicado em 31 de janeiro de 2014

costao

 

Rocky shore is the name given to the coastal environment formed by rocks between land and sea. It is considered more as an extension of the marine environment than the terrestrial environment, since the vast majority of organisms than can be found on the rocky shore are related to the marine environment.

 

There are rocky shores all along the Brazilian coast. Its limit of occurrence ranges from Torres (RS) until Baía de São Marcos (MA). The highest concentration of this formation is in the southeast region, where the coast is rather indented.

 

The rocky shore can be shaped and modified by different aspects: physical, chemical and/or biological. Erosion by wave beats, winds and rain is the main physical aspect in addition to temperature variation. The chemical aspects depend on the type of rock that forms the coastline, since minerals, such as iron, react chemically with water. As biological factors the erosion of rocks can be caused by organisms such as urchins, sponges and mollusks.

 

This ecosystem can be very complex and the greater the complexity, the greater the diversity of organisms in a particular environment. There are basically two different types of rocky shores:

 

Exposed shore: Is the type of coastline that suffers more impact of waves. The diversity is smaller than the ones less exposed to the waves. With the intensity of the waves and their beat against the rocks hinders fragile organisms to fix onto the rocks.

Protected shore: Is the type of shore where the impact of waves is weak. There is a great diversity of associated species. The fact that it suffers less impact of waves helps fixing organisms.

In general, the rocky shores present a rich and complex community. The substrate favors the fixing of larvae of invertebrates, mainly of species that live attached (sessile animals).

The occupation of the rocky shore occurs according to the establishment of the species, in well defined areas, and happens according to how each organism adapts to environmental factors (abiotic and biotic).

This occupation is known as zonation. There are different methodologies to establish the limits between one zone and another, but in general they can be divided into 3:

 

  1. Where organisms live that stay above the high tide, in a transition area between the dry land and the sea = SUPRA COASTLINE. Crustaceans and some gastropod mollusks can be found.
  2. Area where organisms live between the tides, being partially covered and uncovered daily = MESO COASTLINE. These are barnacles, which are fixed crustaceans, gastropod and bivalve mollusks such as mussels and some crustaceans, like crabs.
  3. Regions always covered by water where organisms live below the low tide line, or rarely uncovered = INFRA COASTLINE. Example: Algae, echinoderms, porifera (sponges), crustaceans, mollusks (including octopus), fish etc.

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