introduction to Reef Ecology



Coral reefs are very intricate and complex ecosystems.

An ecosystem is a community of living organisms in conjunction with the non-living components of their environment (such as substrate, humidity, radiation, temperature, salinity, pH, etc.), interconnected through nutrient cycles and energy flows. 

Healthy coral reefs are characterized by an incredibly high abundance of different species (high biodiversity). Most estimates say that about 25-33% of all marine species can be found on coral reefs; an impressive number, especially considering that the surface area of coral reefs is estimated to be less than 1% of the surface of the oceans. If this small area was lost, one quarter to one third of all marine life would be instantly lost with it, which would then inevitably cause the collapse of the whole marine food web.

As shown in the picture below, coral reefs are mostly found in shallow waters around the equator, where the water temperature is between 26°C (79°F) and 32°C (90°F). Temperature directly influences their growth speed of coral and can cause death if too low or too high.

Nutrient Cycles

All organisms within an ecosystem are interconnected through nutrient cycles and energy flows. While these cycles are very complex when analyzed in detail, they can be easily envisioned thanks to visual representations that can go from being as simple as a circle to complex multilayered webs.

As the name suggests, all nutrient cycles are closed circuits, which means that the principle of conservation of mass must be maintained. This implies that all elements within a closed cycle are never truly created or destroyed, but they simply change form, become incorporated in different molecules, possibly going from being part of organic matter to inorganic and vice versa. Organisms absorb the nutrients they need to grow from their environment; when they die or get consumed by another organism, all these elements get reabsorbed, digested and then transformed and incorporated into different molecules.

The most known cycles are those of Carbon, Oxygen, and Water, although the same model can be used for any element or molecule present in an ecosystem, such as Nitrogen, Phosphorus, etc.

Importance of Coral

Coral is by far the most abundant organism on reefs and it plays a key role in creating and maintaining a balance in the marine environment. While it is easy to accept this as a factual truth, it is important to understand how coral is interconnected with almost every other marine organism and how its survival and the reef’s well-being affect humanity’s quality of life as well.  

The ecological functions that coral reefs perform in the marine ecosystem are so complex and essential that they cannot be duplicated or replicated by any form of manmade substrate, artificial reef, or machinery:

  • Base of the food web
  • Nursery grounds for juvenile fish and invertebrates
  • Key role in the carbon cycle
  • Important water conditioning factor
  • Effective pollution indicator

Economically speaking, the coral reef plays a key role in sustaining multiple human industries such as:

  • Fishing
  • Tourism
  • Aquarium Trade
  • Pharmaceutical
  • Coastal Protection
Threats to the Coral Reef

The coral reef is a very intricate ecosystem which draws strength from the diversity of species that inhabit it. A high biodiversity means a high capacity to adapt and thrive despite environmental changes, a property known as resilience.

As reefs continue to lose species due to various causes, its resilience also diminishes, rapidly approaching a tipping point where most species won’t be able to adapt to new stressors and will disappear completely.

There are many factors that can prove to be detrimental to the reef’s health, especially when not monitored and dealt with effectively and in a timely manner.  The vast majority of the threats to coral reefs, just as for many other environments, comes from excessive and unregulated human activity.

  • Natural Threats (Cyclones/Tsunamis/Excessive Rainfall, etc.)
  • Destructive Fishing (Dynamite Fishing, Cyanide Fishing, Bottom Trawling, etc.)
  • Overfishing
  • Runoff Water (Pollution, Eutrophication, etc.)
  • Coastal Development (Oversedimentation, Coastal Destruction, etc.)
  • Careless Tourism (Boat Anchoring, Reef Walking, etc.)
  • Climate Change (Global Warming, Altered Weather Patterns, Coral Bleaching, Ocean Acidification, etc.)

Coral Reefs play an irreplaceable role in the marine environment, as well as the terrestrial one. They are the direct source of food and sustenance for over a third of the human population, and are indirectly linked to the survival of the human race as a whole. Their very low surface area and extremely high biodiversity make them very delicate and important ecosystems, which warrant for our best efforts to be preserved and maintained healthy.

Human activity is causing the disappearance of coral reefs due to a number of environmental changes linked to excessive consumption of fossil fuels, as well as creation of pollutants and interference with many natural regulation systems, all of which are direct causes of coral bleaching and species loss.

Humanity has to shift its focus towards the conservation of key natural environments in order to rebalance broken ecosystems and reduce the impact that it is having on multiple fronts. Failure to do so will result in the progressive loss of key ecosystem functions, which will eventually render the planet uninhabitable to many species, including humans.

Reducing our carbon footprint is at the top of the list. Since climate change knows no political or geographical boundaries, it is having the most effect on the most sensitive ecosystems worldwide, regardless of where they are located; first and foremost, the coral reefs.

Trash and pollution in general are also problems that are not localized to the country of production: once they reach the sea, ocean currents will transport them across the globe, making it virtually impossible to track their origin and to contain the damage they cause.

We need to become responsible consumers: we need to start thinking about the ecological cost of products, not just what their price tag is. Electricity derived from clean and renewable energy sources, pesticide free produce, energy efficient diets, locally sourced food; these are all examples of environmentally friendly methods to obtain the products we have grown accustomed to in our modern lives, without sacrificing the environment in the process. We need to make an effort to look for these products and be ready to spend some extra money to support responsible, environmentally friendly producers, instead of cheap, irresponsible ones.