Ecology of Sandy Beaches

Expectations ?? ?

Objectives The Biological Study of Sandy Beaches Typical sandy Beach animals (Characters & features) Cryptic animals Meiofaunal Vs Macrofaunal Sand Sample The importance of developing and understanding of sandy shore ecosystems. Physical Environment. Sand. Waves: Surface gravity, Internal & Edge waves. Wind.

The Biological Study of Sandy Beaches When has the biological study started? It started only fifty years ago after intensive studies of rocky shore. Why was there an early neglect of sandy beach ecosystem? It seems always devoid of life (why?).

The early neglect of sandy beach ecosystem was due to Rocky shore 1- Obvious life-presenting fascinating prospect to scientific research. 2- Plants & animals are large and highly colored. 3- Many animals are sessile or very slow moving, easy to collect and study. Sandy Shore 1- No attached plants. 2- Animals are so small. 3- Few species of macrofauna are cryptic. 4- On sheltered beaches burrows excavated by Arenicola and Callianosa (evidence to life). 5- On exposed beaches, sand is unstable to support burrows intertidal. 6- Animals are highly mobile to maintain their position.

Cryptic animals They are hiding within sand. They appear only when necessary to feed, perform other vital functions. Mobility and cryptic mode of life render sandy beach observations.

Typical sandy Beach animals (Characters & features) 1- Millimeter or so in length. Small enough to live and move between sand grains. 2- Migrating up and down through the sand column in response to environmental factors. 3- Those animals are named MEIOFAUNA 4- Although the collection and identification of meiofauna is difficult than macrofauna, the diversity of meiofauna is higher than macrofauna.

Meiofaunal Vs Macrofaunal Sand Sample A single sand sample Numerous species of A Nemertina M N Turbellaria U Tardigrada E A Foraminifera I F O Nematodes Ostracoda Annelids Gastrotrichs Harpacticoida

Very Few Species of In Contrast: Typical permanent intertidal sandy beach MACROFAUNA Very Few Species of Polychaete Mollusca Donax sp. Two or few Crustacea species Although of this distinction, macrofauna has intensively studied Our knowledge about meiofauna and microbiota are poor.

The importance of developing and understanding of sandy shore ecosystems ¾ of the world’s Ice free coastline Consists of sandy Shores. Appropriate management & successful conservative Can only be achieved. Beaches and dune Systems are fragile ecosystems need management.

Physical Environment Physical Habitat Structure is determined by Sand Sandy Coastal line = Shores +Beaches It is Dynamic environment Physical Habitat Structure is determined by Sand Air Water

Sandy Beach is one of the most stable dynamic coastal line (why?). Due to its ability to absorb wave energy. Beach is characterized by Wave driven sand transport Aeolian (wind) transport Sediment transport in Dunes by wind action. Sediment transport in Surf zone by wave action.

Originates from

Surface Gravity Waves: 1-Generated by wind stress on water surface. 2-Friction (wind & water) 3-A viscous drag 4- Stretches the surface like an elastic membrane undulation Wind Surface tension waves Distortion Restoration

What happens if strong wind blows up? 1-Waves grow. 2-Gravity replaces surface tension. 3-Waves move off before the wind. 4-Waves transfer energy from wind at sea to coastal zone.

Internal waves Generated by Tide Wind They occur at the boundary between water layers of different densities. Generated by Tide Under water avalanches Wind Internal waves may causes fluctuations in surf zone

Edge waves They are waves running along the shore and contained in surf zone. ًWind They are important in shaping wave characteristics. Surface water movement is about 2% of wind speed. Strong on shore winds Off shore winds Wave Height Size of surf zone Wave Height flatten Size of surf zone Affect sediment transport between Beach and Dunes

ٍٍ Summary

Sand Movement Sand moves in two ways Bed Load Suspended Load It is moving close to the bed Coarser materials Suspended Load It is transported above Bed Finer materials The steeper the waves and the beach, the greater the tendency for accretion.

In Practice: Strong erosion or sea ward movement of sediment for short periods Is balanced by Gradual accretion or land ward