Tropical marine ecosystem
By Marjorie Henry, Contributor

Shanique Coleman speaks during The Gleaner's Student Forum on Agriculture at William Knibb High School, in Trelawny, recently. - Claudine Housen/Staff Photographer

The tropical marine ecosystem is the last aspect of the general topic of ecosystem that you are required to do. In terms of its location, the tropical marine climate occurs along the eastern areas of regions having a tropical continental climate. The lowlands of Central America and the West Indies are examples of areas where this climate is best developed. The latitudinal location is 10° to 20° from the Equator.

Let us now turn our attention to the characteristics of the climate. A very important factor here is that the sea influences the climate, hence the term 'marine'.

• The region receives steady rainfall from the trade winds, blowing across warm ocean currents. They blow throughout the year.
  
  
• There is rain almost every day, with rather heavier falls in the hot season. In short, there is no month without any rain.
  
  
• The amount of rainfall varies from 1,000mm to 2,000mm (40 to 80 inches) depending upon the location.
  
  
• The rainfall is both orographic where the trade winds meet upon upland masses, and convectional due to intense heating during the day and in summer.
  
  
• Temperatures are generally very high, although there is a slightly cooler season when the overhead sun appears to have migrated into the opposite hemisphere.
  
  
• The annual temperature range is about 8°C (15°F) with hot season temperatures of 29°C (about 85°F) and cool season temperatures of 21°C (about 70°F).

Note that, due to the steady influence of the trades, the tropical marine climate is prone to hurricanes.

The vegetation of the tropical marine climate is our other area of interest. I would like to refer you to the new edition of the text The Caribbean Environment for CXC Geography by Mark Wilson for this section of the study. He provides a detailed account on this.

Let me highlight some of the major points here and trust that you will source the text and go through the information carefully. He starts with a general comment that the vegetation is adapted to seasonal drought and varies locally with climate, soil, relief and drainage. He groups the varied vegetation types as follows:

• Hygrophytic ecosystems (from the Greek words for wet plant) develop where there is a short dry season, broken by intermittent spells of rainfall. The soil always holds enough water for plant growth. Ecosystems are close to true rainforest, as in northern and eastern Trinidad, in many areas of the Windward Islands and Belize, and in the wettest parts of Jamaica.
  
  
• Mesophytic ecosystems (Greek for middle plant) are found where there is a longer dry season with fewer rainy spells. In these areas, the most important ecosystem is semi-evergreen forest, which can be seen in areas such as Turner's Hall Woods in Barbados.
  
  
• Xerophytic ecosystems (Greek for dry plant) or dry woodlands are found on islands such as Antigua, and in rain-shadow areas of the Windward Islands and Jamaica, where there is lower annual rainfall and a long dry season with very little rain. They also develop on soils which drain rapidly, where there is a permeable rock such as limestone or volcanic ash.
  
  
• Thorn scrub
  
  
• Vegetation due to local variations, namely

  (i) Mangroves in coastal wetlands called hydrophytic ecosystems

  ii) Coastal vegetation may be adapted to dry, sandy soil.

  iii) Montane forest and elfin woodland develop where mountainous relief brings cool. Moist conditions.

As you go on your Christmas break from school, may I encourage you to take some time to review this topic on 'ecosystems'. Here are some pointers for this.

• Be able to define the term ecosystems.
  
  
• Know the components of the ecosystems and the link between them.
  
  
• Be aware of the factors that influence the ecosystems.
  
  
• Be able to discuss fully, the equatorial, tropical marine and tropical continental ecosystems.

Incidentally, I hope that you have already purchased a copy of the syllabus for yourself. You certainly need it to guide you along.

Best wishes for the festive season and the New Year.

References:

General Geography in Diagrams by R. B. Bunnett

Certificate Physical and Human Geography by Goh Cheng Leong

The Caribbean Environment by Mark Wilson

Marjorie Henry teaches at Glenmiur High School.