Step 1: Compare very different ecosystems
Start with two contrasting marine ecosystems, such as a reef and a hydrothermal vent, so students can see how different ocean life can be.
Ocean Literacy Principle 5
The ocean supports a great diversity of life and ecosystems
Ocean life ranges from microbes to giant animals, occupies most of Earth’s living space, and forms ecosystems shaped by light, pressure, chemistry, circulation, and species interactions.
Guiding question: How do ocean habitats support so many forms of life and interaction?
What this principle means
Life ranges from microbes to giant animals
Ocean life spans an enormous range of sizes, roles, and evolutionary groups.
Ocean life ranges from microbes to giant animals.
Ocean life ranges in size from the smallest living things, microbes, to the largest animals that have lived on Earth. This wide range helps show how the ocean supports extraordinary biological diversity.
Microbes form the basis of ocean food webs.
Most of the organisms and biomass in the ocean are microbes, which are the basis of all ocean food webs. Microbes are the most important primary producers in the ocean, with fast growth rates and life cycles, and they produce a huge amount of the carbon and oxygen on Earth.
Many major groups are found only in the ocean.
Most of the major groups that exist on Earth are found exclusively in the ocean, and the diversity of major groups of organisms is much greater in the ocean than on land.
Ocean ecosystems are vast, varied, and unevenly distributed
Ocean life is shaped by environmental conditions, so biodiversity changes from place to place and from surface waters to the deep sea.
Most of Earth’s living space is in the ocean.
The ocean provides a vast living space with diverse and unique ecosystems from the surface through the water column and down to, and below, the seafloor. Most of the living space on Earth is in the ocean.
Ocean life is not evenly distributed.
Ocean ecosystems are defined by environmental factors and the communities living there. Ocean life is not evenly distributed through time or space because oxygen, salinity, temperature, pH, light, nutrients, pressure, substrate, and circulation vary across the ocean. A few regions support the most abundant life on Earth, while most of the ocean does not support much life.
Zonation patterns shape coastal and open-ocean diversity.
Tides, waves, predation, substrate, and other factors create vertical zonation patterns along the coast. Density, pressure, and light levels create vertical zonation patterns in the open ocean. These patterns influence where organisms can live and how diversity is distributed.
Estuaries provide important nursery areas.
Estuaries provide important and productive nursery areas for many marine and aquatic species.
Ocean life includes unique relationships and energy pathways
Marine ecosystems include relationships and food webs that range from sunlit plankton systems to deep ecosystems powered by chemistry instead of sunlight.
Ocean biology includes unique relationships and life histories.
Ocean biology provides many unique examples of life cycles, adaptations, and relationships among organisms, including symbiosis, predator-prey dynamics, and energy transfer that do not occur on land.
Some deep ocean ecosystems do not depend on sunlight.
There are deep ocean ecosystems that are independent of energy from sunlight and photosynthetic organisms. Hydrothermal vents, submarine hot springs, and methane cold seeps rely on chemical energy and chemosynthetic organisms to support life.
Key ideas
- Ocean life ranges from microbes to giant animals.
- Most ocean organisms and biomass are microbes.
- Microbes are the basis of ocean food webs and major primary producers.
- Many major groups of organisms are found only in the ocean.
- The ocean contains more diverse major organism groups than land.
- Ocean biology includes unique life cycles, adaptations, and relationships.
- Most of Earth’s living space is in the ocean.
- Ocean life is unevenly distributed because environmental conditions vary.
- Some deep ocean ecosystems rely on chemical energy rather than sunlight.
- Estuaries are important nursery areas for many marine and aquatic species.
Teach this principle
Step 2: Connect conditions to biodiversity
Ask which abiotic factors such as light, oxygen, nutrients, pressure, salinity, or substrate help explain why life is abundant in some places and sparse in others.
Step 3: Trace relationships
Use examples of microbes, predators, symbiosis, nursery habitats, and deep-sea communities to show how biodiversity depends on ecological interactions as well as environment.
Why this matters
This principle helps students understand that biodiversity in the ocean is not just a list of species. It includes vast living space, unique ecosystems, uneven environmental conditions, and the relationships that connect organisms to one another.
What students should take away
Students should come away understanding that most of Earth’s living space is in the ocean, that marine life is extraordinarily diverse, and that biodiversity depends on both abiotic conditions and ecological interactions.
Classroom prompt: Choose two very different ocean ecosystems on this page. What conditions and relationships help explain why the organisms in each place are different?
Teach with Blue Biome
Explore this principle with the platform
WebGIS
Compare species distributions, ecoregions, and ocean settings to see how biodiversity changes across environments.
Knowledge Graph
Trace food webs, symbiosis, predator-prey links, and ecosystem connections across the ocean system.
Cards
Use cards such as Mutualism, Apex Predator, and Thermal Vents to discuss relationships, trophic roles, and unusual ecosystems.
Start here
Ecoregion
1. Start with a highly diverse ecosystem
Use the Great Barrier Reef to discuss why some marine ecosystems support very high biodiversity.
Species
2. Start small
Use Prochlorococcus to show that microbes form the basis of ocean food webs and much of ocean productivity.
Opportunity
3. Explore a deep ecosystem without sunlight
Use Thermal Vents to discuss how some ocean ecosystems depend on chemical energy instead of photosynthesis.
Tool
4. Trace biodiversity relationships
Use the Knowledge Graph to connect species interactions, trophic roles, and ecosystem context.
Featured examples
Featured Species
Species
Prochlorococcus
Prochlorococcus helps explain this principle because microscopic primary producers support ocean food webs and contribute to planetary-scale productivity.
Species
Killer whale
Killer whales help illustrate the upper end of ocean body-size and trophic diversity, as well as predator-prey dynamics in marine food webs.
Species
Blind shrimp
Blind shrimp help explain the principle because they live in deep-sea vent ecosystems supported by chemical energy rather than sunlight.
Species
Copepod
Copepods help show how small zooplankton connect microbial production to larger animals through energy transfer in the food web.
Featured Ecoregions
Ecoregion
Great Barrier Reef
Distinctive: This reef contains complex habitats and a high diversity of interacting organisms.
Connected to the global system: It helps explain how environmental conditions and biological relationships can support extremely rich marine ecosystems.
Ecoregion
Rainbow Vent Field
Distinctive: This deep-sea ecosystem is supported by chemical energy from hydrothermal activity.
Connected to the global system: It shows that some marine ecosystems can function without sunlight, relying instead on chemosynthetic life.
Ecoregion
Amazon River Plume
Distinctive: This river-influenced marine region is shaped by freshwater, nutrients, and strong environmental gradients.
Connected to the global system: It helps explain how productivity, nursery habitat, and biodiversity depend on changing environmental conditions.
Featured Cards
Special
Mutualism
Mutualism illustrates the principle by showing that cooperation between species can shape marine ecosystem function.
Special
Apex Predator
Apex Predator illustrates the principle by highlighting predator-prey dynamics and the ecological roles of top consumers.
Opportunity
Thermal Vents
Thermal Vents illustrate the principle by showing that deep ocean ecosystems can be powered by chemical energy instead of sunlight.