A SEMINAR ON-

Artificial reefs

SUBMITTED TO-

Dr.S.K.RoutDept.- AEM

SUBMITTED BY-

Riddhiman Saha

Fs- 17/13F. F. Sc

What is Artificial reef ?

• An artificial reef is a structure that is deliberately or accidentally introduced to the seabed and that attracts marine life.• It provides shelter from predation and surfaces for larvae to settle on.• Coastal communities in some countries have traditionally used artificial reefs to increase their catches.

Purpose to establish:• Fisheries enhancement.• Coastal protection.• Reef rehabilitation and recreational diving.

These are quite common in western Indian Ocean…….

Materials required:

Before choosing any material we have to go through some criteria:

Compatibility

Durability

Stability

Function

• Wood, including bamboo, log cribs.

Benefits:1. Availability.2. Attracted large

concentrations of fish. Drawbacks:1.Short life span.2.Wood is a very light

material and must initially be heavily ballasted to keep it on site.

Shells:• Shells have historically been used by most

coastal states to create or replenish oyster reefs.

Benefits:1. These types of reefs do not pose a

substantial threat to fishing gear, such as trawls.

2. Clean mollusk shells are compatible with the marine environment.

Drawbacks:1. Oyster or clam shells are generally not

donated materials and must be purchased

Rocks:Benefits:1. Limestone is comprised of

calcium carbonate.2. Most of the rocs are a

very dense, stable, and durable material.

3. Different size particles of rock can be used to accommodate different life stages of species of interest.

Drawbacks :1. Transportation costs to

both the staging and reef sites is expensive and will require the use of heavy equipment.

Ash byproducts:• Several categories of ash byproduct material have been proposed as

artificial reef materials.• Ash byproducts from the combustion of coal, oil, and municipal solid

refuse have been combined with cement or other bonding agents and pressed into pellets or blocks.

Benefits:1. Analyzed pellets or blocks from one source of coal burning particles is a

quite cheap source. Drawbacks:1. Variable leaching rates may occur with different environmental

conditions.2. Testing of fly ash for toxic components is expensive and may be cost

prohibitive to programs.3. Ash characteristics, particle size and composition, and bioaccumulation

rates also vary in response to site specific factors. Also different types of tires, vehicles, White Goods, Reef balls are also being used to make the same.

Artificial reefs and their construction:

Some pictures of artificial reefs:

These kinds of reefs can be seen in japan , gulf of Maxico and at different places as well…….

Ecosystem in artificial reef:• ARs are known to affect nearby sandy benthic sediments and their

communities.

• When an AR obstructs current flow, a stationary wave is formed, which can trap drifting larvae and seaweeds.

• Moreover, fish attracted to ARs can significantly increase nutrient production in the water column - by excreting ammonium, urea and faeces - which is then incorporated into the reef food web.

• This process contributes to the organic enrichment of sediments due to entrapped drift algae and other organic materials driven from reef biological activities and deaths of reef associated organisms.

• Sediment nutrient enhancement from deposited organic material can be incorporated into the reef food web, enhancing sandy benthic production which contributes to the rehabilitation of sandy coastal areas via sediment chemical trophic chain pull-out.

• The biochemical role of ARs in this respect is particularly important in shallow coastal areas (less than 50 m deep), where productivity in the overlying water column is heavy.

• Nevertheless, sandy benthic communities have an important role in coastal food webs since they are an important food/energy source and a crucial link between lower and higher trophic levels , such as commercial fish feeding on benthic ARs resources.

Food web in artificial reef:

Fish production is an important part of artificial reef. We can get animals of large variety as well…..

Red snapper Octopus tyranus

Drum fish

• Benthic fish population is present and covered with soft corals and algal growth.

INFERENCE • Natural reefs are grown naturally.

• Artifical reefs are artificial reefs we do tweak the physical architecture and complexity of the structure in ways that presumably help our purposes and that can affect growth, survival, and other processes.

• Aquatic lives have been also blessed with their new destination.

• Though, this artificial reefs have some bad effects over the hydrosphere we have to use this for our own interest as well as to get more fishes.

REFERENCES•WEBSITES:www.google.comOnline encyclopedia

Book:Guideline for marine artificial reef materials 2nd edition

THANK YOU