Man-made structures often provide ideal habitats and attachment points in areas of the marine environment that would otherwise be relatively barren. Shipwrecks can provide an "oasis" of life in an otherwise feature-less ocean floor.

In areas more assessable to the common man or women, Sea defences have a similiar affect most noticeable in areas of sandy or stone beach.

Sea-defences on sandy beaches provide excellent attachment points in a constantly moving and dynamic environment of the sandy shore. The first type of plant life to attach itself to these structures is filamentous algae closely followed (depending on season and temperature) by the Macroalage (see below)

The picture on the right shows the early stage of colonisation with small macro -algae attached to the concrete structure.

In a short period of time the filamentous algae is replaced and the space becomes dominated by various species of macro-algae (seaweed's). In this particular location the majority of colonisation is confined to above the mid-line of the structures this is likely to be due to the constant abrasion of the lower regions by the action of the tide lifting the sand and small stones from around the base of the structure.

A number of seaweeds can be found in this type of environment although there is usually a few dominant species.

When the macro-algal growth has reached levels (seen in the picture on the left), mobile organisms which feed on the seaweed and in turn the organisms which feed on them can then colonise the sea defences.

Various species of snail and limpets can usually be found in the lower shore regions close to the low tide mark.

When the sea defenses are covered by water small fish sometimes seek shelter and food within the fronds on the algae. In some areas fish nursery's are born especially around structures that are permanently below the waterline.

As you get closer to the lowtide mark the level of seaweed cover increases due to reduced time exposure to the air and the decreased dessication (drying out) effects of the sun. The photo on the left is taken further down the shore than the one on the right.

The changes in the concentration and type of marine algae found as you move though the intertidal zone can be "mapped" into different zones. These changes in marine organismas and environmental effects such as desication rates has been extensively studied and is given the name: ZONATION.

The exposure and type of material both natural (rocks placed on the shore by man) and unatural (concrete structures) are colonized by a wide range of species determined by the environmental conditions. In protected harbours or areas of low water movement more delicant and faster growing seaweeds can dominate (see below). A vast mat of small bundles of delicate seaweeds going on rocks placed on the shoreline to protect the harbour and expensive boats and ships.

Photograph Location: cannes - France