• What Is El-Nino ?
• Boy Scouts to Girl Guides
• The starfish family - Nature Watch

What Is El-Nino ?

El-Nino refers to a warm surface ocean current that occasionally appears along the coast of the South American countries like Ecuador and Peru. This warm current cuts off the usual ups welling of cold, nutrient-rich bottom water that supports the economically and environmentally important fish population. El-Nino typically starts toward the end of the year, and hence the name "El-Nino", which has the meaning of "the child" for the Christmas season in Spanish. Appearances of El-Nino have been documented as far back as 1726. El-Nino can be described as a natural process taking place in the earth's atmosphere in order to balance the heat accumulated at different parts of the atmosphere. It occurs approximately once in every 2-7 years and causes adverse weather conditions in some parts of the world.

The effect of the El-Nino is felt most strongly in the east Asian region (around Indonesia) and in the tropical regions of the Pacific ocean.

El-Nino is associated with the southern oscillation, a sea saw pattern of air pressure variation between the eastern and western tropical Pacific. Surface air pressures are normally lower in the region of northern Australia and Indonesia than over the Southeast Pacific. Consequently, the trade winds of the equatorial Pacific have an east to west component. This persistent easterly flow literally drags warm surface waters toward the west. Along the coast of tropical south America, cold bottom water wells up to the surface to replace the warm water that is dragged westward.

One of the first signs of El-Nino is a drop in air pressure over large areas of the Southeast Pacific, while pressures rise over the Western Pacific (the southern oscillation). This shift in pressure pattern causes the equatorial easterlies to reverse direction. Westerly winds then drag warm surface waters towards the east. When the warm waters reach the South American coast, they are deflected southward along the coastlines of Peru and Ecuador.

In 1997, El-Nino began around June and by December the warming of surface waters was unprecedented in magnitude and extent. The unusual warming spreads westward along the equatorial Pacific to near the international dateline (180° west), and in several places, sea-surface temperature anomalies (departures from normal) reached + 6 o. This anomalously warm water over vast areas has led to major changes in atmospheric circulation patterns over tropical and middle latitudes. Circulation changes, in turn, has led to weather extremes in many areas.

The winter storm tract has been displaced hundreds of kilometers southeast of its normal position, which has resulted in destructive high winds and heavy rains in California. Excessive rains in November 1997 to January 1998 have caused heavy flooding in several areas in the southern parts of the United States. At the other extreme, there has been a severe drought in Australia, Indonesia and South Africa resulting heavy losses in crops, and farm animals.

El-Nino also has a devastating impact on marine life in the eastern tropical Pacific, particularly off the coast of South America. El-Nino has brought warm surface waters eastward, thus preventing upwelling of nutrient-rich cold water from the ocean depth. As a consequence, the growth of microscopic algae that normally flourish in the upwelling areas diminished sharply resulting a decline in the fish population, marine birds and other marine animals like sea lions and seals.

El-Nino provides a remarkable example of the vast complex interconnections between the atmosphere, the ocean, and the many forms of life, not only in the equatorial Pacific, but around the entire globe. Scientists are studying these interconnections for many years in an attempt to understand and predict the origin and impact of future El-Ninos.

Nixshaka Dissanayake

Mahamaya College,

Kandy

Stamp News 23

Boy Scouts to Girl Guides

Parallel to the Boy Scout movement (which was featured last week) is the Girl Guides movement aimed at character building for girls from the ages of 7 to 21.

The 'father' of scouting, Lord Baden Powell founded the Girl Guide movement in 1912 helped and inspired by his wife Olave St Clair Soames. Guiding was introduced to Sri Lanka five years later and the first Girl Guide Company in the country was established at Girls' High SChool Kandy in March 1917 by Miss Jenny Calvery (later Mrs Green).

Having completed 60 years, when the Girl Guide movement in Sri Lanka celebrated its diamond jubilee in 1977, a 75 cent stamp was issued to mark the occasion. Although the celebrations were held in March, the stamp was issued on December 13th. Over 3,000 guides comprising of Rangers, Girl Guides, Girl Scouts and Little Friends attended an International Camp held at the Vihara Maha Devi Park in Colombo. Not only Girl Guides from all parts of the country but also from Bangladesh, India, Japan, Malaysia, Singapore and Seychelles attended this historic event.

The 75th anniversary of Girl Guiding in Sri Lanka was also commemorated by the issue of two stamps on 10th May 1993. The Re 1 stamp depicted a Guide pointing to the Sri Lanka Girl Guide Trefoil which symbolise the vision of Girl Guides - a united, peaceful and harmonious nation enlivened by the radiance of the golden sun. The Rs 5 stamp featured various activities of the guide programme, which is necessary to equip them to serve the community. The new world batch signifies that world guiding is a dynamic organisation which reflects modern development trends and needs and the flame of the love of humanity.

It is interesting to note that these two stamps carried the country's name as 'Shri Lanka' as against the usual form 'Sri Lanka'.

Today, with over 25,000 guides spread throughout the country, guiding is not mere1y fun and games but instills skills and correct attitudes in young minds for good citizenship. This enables the girls to step out into the wide world as responsible adults, patriotic citizens with a concern for others, love for the country and the will to carry out to the best of their ability, any job that is entrusted to them. Guiding is built on values expressed in the four signposts - Health, Handicrafts, Intelligence and Service. Each age level has something special for the development of the mind and body.

The movement has grown rapidly over the years and is not confined to urban areas. It's quite popular in the rural areas too. It has been recognised by educationists as a positive force in character building and has been geared to national development.

The Sri Lanka Girl Guides Association has been incorporated by an Act of Parliament and has been a full member of the World Association of Girl Guides and Girl Scouts since 1951.

The starfish family

The starfishes and their relatives be- long to one of the major groups of invertebrates, or animals without backbones. The group is called the echinoderms. Echinoderm means having a spiny skin.

Some species live in the parts of the sea shore between the high and low tide mark, while others live off shore or in the deep sea.

They all have a body cavity, or coelom.

Symmetry

The body-plan is the same in all echinoderms. They have the parts of their body arranged in sections around a central point - like a wheel. This arrangement is called radial symmetry. Most echinoderms have five sections.

Five classes

There are five sub-groups or classes of echinoderms. These are the starfishes, brittlestars, sea urchins, sea cucumbers and crinoids. Many members of these five classes have spines either on their shell-like outside, or test, or embedded within the layers of their skin.

Water-vascular system

There is a tube inside the body running close to the surface in each of the radial sections. The main radial tubes, or canals, are connected to each other by a ring canal surrounding the mouth. These canals act as a sort of hydraulic skeleton, helping to support the body. This is called the water-vascular system.

On each side of the radial canals there are two regular series of muscular side branches. These stick out through the body wall to form tube feet. These are used for walking and feeding. Some tube feet are specialized to help clear left-over food from around the mouth. Echinoderms move by pushing their tube feet either through a groove in their arms (starfishes and brittlestars) or through holes in the test (sea urchins). They can form suckers on the end of their tube feet which help them to hold on to or climb up vertical surfaces.

Sea urchins

Sea urchins, or echinoids, have a ball-shaped or flat bun-shaped body, covered with hundreds of moveable spines.

The spines are attached to the test by a ball and socket joint. The "socket" is on the base of the spine. It fits on to the corresponding "ball" or knob on the test. These knobs are usually arranged in regular patterns. When the sea urchin dies the spines usually break off, and the knob pattern can be seen.

The mouth is on the underside, at or near the centre of the body. Sea urchins eat almost anything. Some prefer plant material while others prefer animal matter. They have a powerful jaw-like structure made up of five shelly "teeth" around the mouth. This is called "Aristotle's lantern", because Aristotle compared it to a lantern.

Starfishes

The starfishes, or sea stars, belong to the class Asteroidea. This name comes from a Greek word that means star-like. Most starfish have five arms, but some have more.

Starfish have many shelly plates embedded in their skin. These have spines which stick out through their skin and make a prickly surface. These spines help protect the skin gills through which the starfish breathe. The mouth is on the underside of the body and the digestive tract loops upwards to the anus, which is at the top.

Brittlestars

Brittlestars belong to the class Ophiuroidea. They look like starfish, with longer, thinner arms and smaller more disc-shaped bodies.

Sea cucumbers

Sea cucumbers are animals which look like cucumbers. They belong to the class Holothuroidea. They have no spines, but they have microscopic spicules in their skin to support their soft bodies. Some of their tube feet are modified to make feeding tentacles.

Sea lilies and feather stars

Sea lilies and feather stars belong to the class Crinoidea. They look like a starfish turned upside-down with its arms upwards.

Sea lilies are attached to the sea floor by a stalk. On the bottom of the stalk may be off-shoots called cirri. These help to anchor the animal on the sea bottom.

Feather stars do not have a stalk but they do have a number of cirri attached to their back. They use these to cling to rocks and coral.

Feeding and breathing

Many echinoderms eat microscopic particles of organic matter in the sea water. They make water currents by beating their hair-like cilia. This moves particles along the food grooves to the mouth.

The water currents also bring a fresh supply of oxygen-rich water to the surface gills for breathing.

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