Sandy beach can be defined as a coastal region where the waves actively stir up the sediment. It ranges from the area in between the tides, being able to reach, in some places, up to 20 meters depth.
In Brazil our beaches have sediment consisting basically of sand and despite seeming a homogeneous environment, even almost like a desert, there is a big difference between the different areas of a beach.
The beaches are formed by the action of the sea currents, the waves and the tides. The kinds of beaches also vary according to some factors such as the proximity of rocky shores, the local wave regime, which are the characteristics of the sediment, the proximity of rivers and even the frequency in which the meteorological phenomena occur in the region.
What determines the distribution of living organisms and their adaptation such as the ability to keep exposed, buried or submerged, is the rhythm of the tides that establishes feeding conditions and provides energy to the ecosystem.
The so called tumble beaches, or wild beaches, have a strong beat of waves that constantly stir up large amounts of sand, changing the profile of the beach and preventing many species to establish themselves on site.
The calm or hard beaches, on the other hand, with their often very gentle slope that allows you to go a long way into the sea without reaching great depths, are home to an abundant and diverse fauna.
On the rocky shore, the beaches feature 3 distinctive tracks according to the variation of the tides:
- Upper strip, constantly moist, but only covered in extremely high tides, such as undertows or storms – we find species more adapted to life on earth than to aquatic life;
- Median strip always covered and uncovered by the tides twice a day – is populated by a larger number of species. Marine species that are adapted to prevent water loss during the low tide;
- Lower strip, which is always submerged and eventually is exposed during the low tides – is inhabited by organisms nearly without adaptations to life out of the water.