The Saltwater Biome for Middle School Science

Mar 13

4 min read

Saltwater biomes, also known as marine biomes, are ecosystems found in oceans, seas, and coastal regions. They cover about 71% of Earth’s surface and contain high levels of salt, typically around 3.5% salinity. These biomes are home to a wide variety of plant and animal life that have adapted to survive in saltwater conditions. Saltwater biomes play a critical role in regulating Earth’s climate, producing oxygen, and supporting global biodiversity.

Saltwater biomes are found all over the world in different forms:

Oceans – The largest saltwater biome, including the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.
Seas – Smaller saltwater bodies like the Mediterranean Sea, the Caribbean Sea, and the South China Sea.
Coral Reefs – Found in warm, shallow waters near coastlines, such as the Great Barrier Reef in Australia.
Estuaries – Areas where freshwater from rivers mixes with saltwater from the ocean, creating brackish water.
Mangrove Forests – Found along tropical and subtropical coastlines, where salt-tolerant trees grow in shallow waters.

The Different Zones of the Saltwater Biome

The ocean is divided into different zones based on depth, sunlight, and temperature:

Sunlight Zone – The top layer (0–200 meters deep) where sunlight penetrates, allowing photosynthesis. Most marine life is found here.
Twilight Zone – A deeper layer (200–1,000 meters) with limited light. Some fish produce bioluminescence to survive.
Midnight Zone – A dark, cold layer (1,000–4,000 meters) where extreme pressure and scarce food make survival challenging.
Abyssal Zone – Even deeper (4,000–6,000 meters), home to creatures adapted to complete darkness.
Hadal Zone – The deepest part of the ocean (below 6,000 meters), found in deep-sea trenches.

Plants of Saltwater Biomes

Plants in saltwater biomes must adapt to high salinity, strong waves, and changing tides. Many have specialized structures to store water, filter salt, or anchor themselves to the ocean floor.

Seagrass – Seagrasses grow completely submerged in shallow coastal waters. They have flexible, ribbon-like leaves that reduce water resistance and help them withstand ocean currents.
Mangroves – They have specialized roots, called pneumatophores, that stick out of the water to absorb oxygen. Their leaves excrete excess salt to prevent damage from high salinity.
Kelp – A type of large brown algae found in cold, nutrient-rich waters. Kelp has gas-filled bladders that help it float toward the surface to access sunlight for photosynthesis.
Salt Marsh Grass – Found in coastal marshes, this plant has salt glands in its leaves that filter out excess salt.
Sargassum – A type of floating seaweed found in warm ocean waters. Instead of roots, it has air-filled bladders that allow it to stay at the surface, where it can absorb sunlight for photosynthesis.
Red Algae – This algae can grow at deeper depths because it contains special pigments that absorb blue and green light, which penetrate deeper into the ocean.
Sea Lettuce – It grows attached to rocks or floats freely and has a thin, broad structure to maximize sunlight absorption.

Animals of Saltwater Biomes

Marine animals have adapted to saltwater environments in various ways, such as developing salt-excreting glands, streamlined bodies, and the ability to survive in extreme depths.

Dolphins – Use echolocation to navigate and hunt in ocean waters.
Sharks – Have specialized gills to extract oxygen from seawater and sharp, replaceable teeth for hunting.
Octopuses – Can change color and texture to camouflage, and have ink sacs to escape predators.
Jellyfish – Lack bones and brains but use stinging tentacles to catch prey.
Anglerfish – Live in deep waters and use a glowing lure to attract prey in complete darkness.
Sea Turtles – Have flipper-like limbs for swimming and can hold their breath for long periods.
Clownfish – Live in symbiosis with sea anemones, gaining protection from predators.

People of Saltwater Biomes

Many Indigenous communities have traditionally lived along coastlines, relying on marine resources for food, transportation, and cultural practices.

The Polynesians (Pacific Ocean) – Expert navigators who used stars and ocean currents to explore and settle islands.
The Inuit (Arctic Ocean) – Depend on marine mammals like seals and whales for food, clothing, and tools.
The Bajau (Southeast Asia) – Known as “sea nomads,” they live on boats and dive for fish using traditional techniques.
The Haida (Northwest Coast, North America) – Skilled fishers and canoe builders who depend on salmon and shellfish.
The Moken (Thailand and Myanmar) – Semi-nomadic people who have deep knowledge of tides, fish behavior, and marine ecosystems.

Current Challenges for Saltwater Biomes

Saltwater biomes are under threat due to human activities and climate change. Some of the biggest challenges include:

Pollution – Plastic waste, oil spills, and chemical runoff harm marine life and disrupt ecosystems.
Overfishing – Unsustainable fishing practices deplete fish populations and endanger marine species.
Climate Change – Rising ocean temperatures and acidification threaten coral reefs and marine food chains.
Coral Bleaching – Warmer waters cause corals to lose their symbiotic algae, leading to mass die-offs.
Habitat Destruction – Coastal development, dredging, and deforestation of mangroves destroy important marine habitats.
Invasive Species – Non-native species, like lionfish, disrupt local ecosystems by outcompeting native species.

Saltwater biomes are vital to life on Earth, supporting millions of species and playing a key role in the planet’s health. Conservation efforts, such as reducing pollution, protecting marine habitats, and promoting sustainable fishing, are essential to preserving these important ecosystems for future generations.

Check out my biome resources at Teachers Pay Teachers! I have reading passages, picture cards for sorting, and flashcards! You can also check out the flashcards right here!

Here is a preview of the sorting picture cards!