Coral reefs are some of the most colorful and diverse ecosystems on the planet. But contrary to what some may imagine, healthy coral reefs are not predominantly pink. The striking colors of coral reefs come from the tiny animals that live on the reef – the coral polyps. Let’s take a closer look at why coral reefs are colorful, what makes up their palette of colors, and why pink is not the most common hue.
Quick Answers
Are coral reefs pink? No, coral reefs are generally not pink. While there are some pink and purple corals, coral reefs display a wide array of colors including yellow, green, brown, blue, red, orange, and more. The predominant color of a reef depends on the species of corals that make it up.
What colors are coral reefs? Coral reefs can display a rainbow of colors including red, orange, yellow, green, blue, purple, pink, brown, black, and more. The colors depend on the different coral species, algae, and other marine life living on the reef.
What makes coral reefs colorful? The colors of coral reefs primarily come from the coral polyps themselves as well as symbiotic algae called zooxanthellae that live within the coral tissue. Different coral species and algae combinations produce different colors.
What Causes the Color of Coral Reefs?
Coral reefs derive their colors primarily from two sources – the coral animal itself, and symbiotic algae that live within the coral’s tissues. Corals are marine invertebrates that build calcium carbonate skeletons around themselves, slowly forming the underlying structure of the reef. The living part of the coral that extends from the skeleton is called a polyp. Coral polyps come in a diversity of colors, shapes, and sizes based on the species.
Inside the polyp tissues, most corals also harbor a type of algae called zooxanthellae. The coral provides the algae with shelter, nutrients, and carbon dioxide while the algae perform photosynthesis to produce energy-rich compounds for the coral. The different pigments of the zooxanthellae also influence the color of the coral polyps.
Some of the common pigments that contribute to coral coloration include:
- Green fluorescent proteins – Give corals a green, yellow, or brown hue.
- Red fluorescent proteins – Give corals a red, orange, or pink hue.
- Blue chromoproteins – Absorb orange and red light, making corals appear more blue.
- Purple chromoproteins – Absorb blue and green light, making corals appear purple.
- Brown melanin pigments – Absorb all light, giving corals a dark brown or black hue.
The specific combination of coral animal pigments and zooxanthellae pigments produces the wide spectrum of coral colors we see on reefs. Some corals may even fluoresce, glowing brightly under certain light wavelengths.
Common Coral Reef Color Palettes
While the possibilities are endless, here are some of the most common color palettes and examples of corals that make up coral reefs around the world:
- Yellows and Browns – Many stony corals in the family Faviidae like brain corals and maze corals have brown, green, or yellowish hues. Yellow pencil coral is another reef-builder with a bright yellow color.
- Greens – Green coloration is common among corals with high levels of green fluorescent proteins or zooxanthellae. Examples include cauliflower coral, star polyps, and leafy sea rods.
- Blues – Blue chromoprotein pigments lend a deep blue color to corals like the endemic blue coral of Hawaii. Other blue corals include Heliofungia actiniformis and lobed star coral.
- Purples – Vibrant purple comes from chromoproteins and can be seen in corals like cephalochordate coral and some sea fans.
- Reds and Oranges – Red fluorescent protein pigments create fiery shades in corals like the bubble coral, torch coral, and orange cup coral.
- Pinks – A small subset of corals like Galaxea astreata and Lobophyllia display various pinkish hues.
- Blacks and Grays – Melanin and shading give some corals dark colors, like black coral used in jewelry.
The predominance of different coral species and their innate coloration gives each reef a distinctive palette. Location also plays a role, as available light wavelengths influence the zooxanthellae and pigments that are most adaptive for the corals in that area.
How Common are Pink Corals?
There are a few hundred known species of pink and purple corals in reef ecosystems around the world. Some examples include:
- Galaxea astreata – Pale pink and green moving to purple at the tips
- Lobophyllia corymbosa – Bright pink or purple disks
- Lobophyllia hemprichii – Green base with pinkish oral disks
- Eusmilia fastigiata – Pink to orange tree-like coral
- Dendrophyllia spp. – Yellow or pink branching coral
- Tubastrea coccinea – Small fluorescent orange-pink polyps
However, compared to the thousands of known coral species that span the entire color wheel, pink corals make up a relatively small percentage of reef-building species. Their numbers are also declining due to factors like warming oceans that cause coral bleaching.
Are Healthy Coral Reefs Pink?
Pink coral species can be found on healthy coral reefs around the world. But predominantly pink reefs are not considered healthy ecosystems. Here’s why:
- Coral reefs require high biodiversity of many species and colors for ecological balance.
- Massive overgrowth by one or few species can indicate an imbalance.
- Pink corals may gain advantage during bleaching events that kill off other species.
- Predominantly pink reefs have often lost diversity of juvenile coral recruits.
- They have also lost other colored corals from factors like warming, disease, storms, or human impacts.
For example, some areas of the Great Barrier Reef have seen pink and purple corals spread aggressively while other species died off. Though visually striking, this low diversity indicates a reef under pressure.
Typical Coral Reef Color Profile
Here is an overview of the typical color profile of a healthy, diverse coral reef ecosystem:
| Color | Percentage Cover |
|---|---|
| Browns | 25-40% |
| Greens | 15-25% |
| Yellows | 10-20% |
| Blues | 5-15% |
| Oranges/Reds | 5-15% |
| Purples/Pinks | 1-5% |
| Blacks/Grays | 1-5% |
As this table shows, while pink corals are present on most reefs, they normally comprise a small fraction (1-5%) of total coral cover. Browns, greens, and yellows from more dominant species make up a larger share of the color palette.
Changes in Coral Color Over Time
Coral reefs can change color over time for a number of reasons:
- Bleaching – Loss of zooxanthellae results in white, pale coral.
- Growth and regeneration – Young coral polyps are often lighter in color.
- Seasonal variations – More zooxanthellae in summer may deepen color.
- Water conditions – Sedimentation, pollution, or low light impacts hue.
- Species shifts – Changing environment favors different species.
- Diseases – Infections cause tissue loss and exposure of white skeleton.
- Storms – Damage can break, abrade, and expose skeleton.
For example, mass coral bleaching has hit the Great Barrier Reef in recent years causing large expanses of coral to turn white. Lack of juvenile coral growth also means fewer young brown and green colonies.
In other areas like the Caribbean, diseases have wiped out previously dominant species like the long-spined sea urchin. This allowed rapid spread of purple sea fans across the seabed.
Such shifts in color over time provide insight into changes happening on the reef. Predominantly pink or bleached reefs are a warning sign of environmental threats.
Conclusion
Coral reefs display a rainbow of colors that arises from the combination of coral species diversity and their fluorescent, chromatophore, and melanin pigments. While pink corals exist in small numbers, healthy coral reefs are not predominantly pink. A balanced color profile across many hues signifies a thriving, biodiverse reef ecosystem.
Changes in color over time, especially loss of variation and depth of color, can provide early indications of environmental stressors. Coral reef conservation should focus on preserving the full spectrum of coral species and their innate colors as a marker of ecological resilience.
