Eastern Indo-Pacific Marine Realm

Explore the Eastern Indo-Pacific Marine Realm: Coral Reefs, Volcanic Islands, Hawaiian Wildlife and Ocean Biodiversity

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2. Introduction

The Eastern Indo-Pacific (EI) Marine Realm encompasses the warm tropical waters surrounding the volcanic islands scattered across the central Pacific Ocean. Stretching across one of the largest expanses of ocean on Earth, this realm includes Hawaiʻi, the Marshall Islands, and much of Polynesia, excluding New Zealand. Although separated by vast distances of open ocean, these islands are connected by marine currents that transport larvae, nutrients and migratory species across the Pacific Basin.

The Eastern Indo-Pacific is renowned for its spectacular coral reefs, crystal-clear lagoons, volcanic coastlines and deep pelagic waters. Its extreme isolation has allowed many species to evolve independently, particularly in Hawaiʻi, resulting in some of the highest levels of marine endemism anywhere in the world. Many fish, invertebrates and algae found in Hawaiian waters occur nowhere else on Earth.

While the realm shares many species with the biodiversity-rich Central Indo-Pacific, the number of marine species generally decreases towards the eastern Pacific as the distance between island groups increases. This gradual decline reflects the challenges marine organisms face when dispersing across thousands of kilometres of open ocean.

The Eastern Indo-Pacific Marine Realm remains an important ecological bridge connecting tropical marine life across the central Pacific. Healthy coral reefs, open-ocean ecosystems and coastal habitats support biodiversity, protect island communities, sustain fisheries and contribute to the cultural heritage of Pacific peoples.

In This Article

• Where the Eastern Indo-Pacific Marine Realm is located

• Why isolated islands create unique biodiversity

• Coral reef and volcanic island ecosystems

• Marine wildlife found throughout the region

• Environmental challenges affecting Pacific islands

• Practical conservation and stewardship actions

What Is Happening?

The Eastern Indo-Pacific Marine Realm continues to support diverse coral reef ecosystems, migratory marine species and unique island biodiversity. However, these ecosystems face increasing pressures from climate change, marine heatwaves, coral bleaching, invasive species, coastal development and plastic pollution.

Because many islands are isolated and have relatively small populations of endemic species, environmental disturbances can have significant ecological consequences. Coral bleaching events linked to rising ocean temperatures have affected reefs throughout the Pacific, while sea-level rise threatens low-lying islands and coastal habitats.

Despite these challenges, marine protected areas, traditional stewardship practices, scientific research and community-led conservation initiatives are helping improve the resilience of many island ecosystems.

Quick Facts
Main environmental issue	Climate change, coral bleaching, invasive species and marine pollution
Location or ecosystem	Tropical central Pacific Ocean including Hawaiʻi, Polynesia and the Marshall Islands
Species affected	Corals, reef fish, sea turtles, seabirds, sharks, whales and endemic Hawaiian marine species
Best time to visit	Year-round, with seasonal variation between island groups
Region	Hawaiʻi, Marshall Islands and much of tropical Polynesia
Practical action level	Support sustainable tourism, reduce plastic pollution and protect coral reefs
Evidence confidence	High for biodiversity patterns, oceanography and conservation; local conditions vary between islands

Why It Matters

Healthy tropical island ecosystems provide benefits far beyond the Pacific Ocean.

Plants

Marine algae, seagrasses and coastal vegetation stabilise shorelines, provide habitat and contribute to healthy reef ecosystems.

Soil

Native coastal vegetation reduces erosion while helping maintain water quality entering lagoons and coral reefs.

Water

Coral reefs naturally filter wave energy, helping protect coastlines from storms and reducing coastal erosion.

Wildlife

The realm supports colourful reef fish, manta rays, sea turtles, reef sharks, humpback whales, dolphins, seabirds and numerous endemic Hawaiian species found nowhere else on Earth.

Food

Sustainably managed fisheries provide food security and support the livelihoods of many Pacific Island communities.

People

Healthy marine ecosystems underpin tourism, cultural traditions, recreation and local economies throughout the Pacific.

Community Resilience

Healthy reefs, mangroves and coastal habitats improve resilience to storms, sea-level rise and changing ocean conditions.

Main Causes

Direct evidence

• Rising ocean temperatures

• Coral bleaching

• Coastal development

• Marine pollution, including plastics

• Unsustainable fishing practices

• Habitat degradation

Possible contributing factors

• Ocean acidification

• Invasive marine species

• Nutrient runoff

• Increasing tourism pressure

• Extreme weather associated with climate change

What the Evidence Shows

Avoid	Do this instead
Standing or walking on coral reefs	Observe reefs without touching corals
Purchasing coral or protected marine wildlife products	Choose sustainably produced local goods
Feeding marine wildlife	Observe animals naturally from an appropriate distance
Leaving rubbish on beaches	Dispose of waste responsibly and reduce single-use plastics
Anchoring directly on coral reefs	Use designated mooring buoys where available

What You Can Do at Home

Home Gardens

Reduce fertiliser and pesticide use to minimise nutrient runoff entering rivers and oceans.

Balconies

Choose water-wise plants and reduce plastic waste that may eventually reach marine environments.

Schools

Teach students about coral reefs, island ecosystems and the importance of marine biodiversity.

Community Gardens

Promote composting, sustainable water use and native planting to improve environmental health.

Local Groups

Participate in beach clean-ups, reef monitoring programs and citizen science projects.

What Communities Can Do

Communities can strengthen marine conservation by:

• Restoring degraded coastal habitats.

• Supporting coral reef restoration projects.

• Expanding marine protected areas.

• Reducing land-based sources of pollution.

• Encouraging sustainable fisheries management.

• Supporting Indigenous and Traditional Pacific stewardship practices.

• Promoting environmental education.

• Monitoring reef health and marine wildlife.

Conservation and Safety Notice

• Identification warning

• Toxic look-alikes

• Allergy or handling concerns

• Legal restrictions

• Landholder permission

• Contamination risks

Identification Warning

Marine organisms should never be harvested or consumed based solely on photographs or visual similarity. Correct identification remains essential.

Toxic Look-alikes

Some reef fish, shellfish and marine invertebrates resemble edible species but may contain natural toxins or accumulate harmful substances.

Allergy or Handling Concerns

Many marine animals, including corals, sea urchins, jellyfish and some fish, can sting, puncture or trigger allergic reactions.

Legal Restrictions

Marine parks, protected species and fishing regulations vary between countries and island jurisdictions. Always follow local laws and permit requirements.

Landholder Permission

Some beaches, reefs and coastal areas occur within protected reserves, culturally significant sites or private property where access restrictions apply.

Contamination Risks

Avoid collecting seafood or marine organisms from polluted waterways or areas affected by harmful algal blooms or contamination advisories.

Key Takeaways

• The Eastern Indo-Pacific Marine Realm spans thousands of kilometres across the tropical Pacific Ocean.

• Isolated volcanic islands have produced exceptionally high levels of endemic marine biodiversity, particularly in Hawaiʻi.

• Coral reefs support fisheries, tourism, coastal protection and remarkable wildlife.

• Climate change, coral bleaching and pollution present significant conservation challenges.

• Sustainable stewardship, traditional knowledge, marine protected areas and community conservation all contribute to healthier oceans.

References

Food and Agriculture Organization of the United Nations. (2024). The State of World Fisheries and Aquaculture 2024.

Intergovernmental Panel on Climate Change. (2023). Climate Change 2023: Synthesis Report.

National Oceanic and Atmospheric Administration. (2024). Coral reef conservation program.

Spalding, M. D., Fox, H. E., Allen, G. R., et al. (2007). Marine ecoregions of the world: A bioregionalisation of coastal and shelf areas. BioScience, 57(7), 573–583.

UNESCO World Heritage Centre. (2024). Papahānaumokuākea.

United Nations Environment Programme. (2023). Marine and coastal ecosystems.

World Wide Fund for Nature. (2024). Coral reef conservation.

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