Aquatic Biomes
Aquatic biomes include freshwater and marine systems. Their communities are shaped by salinity, depth, light, temperature, oxygen, nutrients, and water movement.
Aquatic Biomes
What Are Aquatic Biomes?
Aquatic biomes are large ecological regions associated with water. They are commonly divided into freshwater and marine systems. Within those broad categories are many different ecosystems with distinct physical and chemical conditions.
Unlike terrestrial biomes, aquatic systems are strongly shaped by factors such as salinity, depth, light penetration, dissolved oxygen, water temperature, nutrient availability, and water movement.
Freshwater vs. marine is the major starting distinction. Then use salinity, depth, light, nutrients, oxygen, and water movement to understand the specific aquatic environment.
Freshwater Biomes
Freshwater contains very low concentrations of dissolved salts compared with seawater. Major freshwater systems include lakes and ponds, rivers and streams, and wetlands.
Lakes & Ponds
Water generally remains in a basin. Light, temperature, oxygen, and nutrient availability can vary with depth and season.
Rivers & Streams
Flowing water creates conditions shaped by current speed, oxygenation, substrate, and upstream inputs.
Wetlands
Wetlands have water-saturated soils or shallow water for enough of the year to create distinctive biological conditions.
Marine Biomes
Marine environments contain saltwater and cover most of Earth's surface. Oceans contain many ecosystems, from shallow coastal habitats to deep open-ocean environments.
Estuaries
Where freshwater meets seawater, producing changing salinity and highly productive conditions.
Coral Reefs
Warm, shallow marine ecosystems built largely by coral organisms and associated with high biodiversity.
Oceanic Systems
Vast marine environments where depth, light, temperature, nutrients, and currents shape communities.
What Controls Life in Aquatic Systems?
These factors interact. For example, light availability decreases with depth, while water temperature and oxygen concentration can vary with depth and mixing. Nutrient availability can influence primary productivity, which affects the organisms supported by the system.
Why Does Depth Matter?
Sunlight is a major energy source for aquatic food webs. As depth increases, less light is available for photosynthesis. The upper, sunlit portion of a body of water can therefore support photosynthetic producers such as algae and aquatic plants.
Below the zone where enough light penetrates for substantial photosynthesis, organisms depend more heavily on organic matter produced elsewhere or higher in the water column. This creates strong differences in community structure with depth.
Why Are Wetlands Important?
Wetlands occur where water saturates the soil for extended periods. They include marshes, swamps, and other water-saturated environments. Wetlands can provide habitat, store water, slow runoff, and cycle nutrients.
Because wetlands occur at the boundary between terrestrial and aquatic environments, they can support organisms from both systems and provide important nursery and feeding habitats.
Wetland is a broad ecological category. Not every wetland looks like a swamp, and wetlands can contain very different plant communities depending on climate, water depth, and chemistry.
Freshwater vs. Marine
Common Misconceptions
If You See This on a Test, Think This
Quick Practice
1. What are the two broad categories of aquatic systems?
2. Name two major freshwater ecosystem types.
3. Why does light availability decrease with depth?
4. What makes an estuary distinctive?
5. Name three abiotic factors that influence aquatic ecosystems.
Key Takeaways
- Aquatic biomes are broadly divided into freshwater and marine systems.
- Freshwater systems include lakes, ponds, rivers, streams, and wetlands.
- Marine systems include oceans, estuaries, coral reefs, and other saltwater ecosystems.
- Salinity, depth, light, temperature, dissolved oxygen, nutrients, and water movement shape aquatic communities.
- Light decreases with depth, limiting photosynthesis deeper in the water.
- Wetlands connect aquatic and terrestrial environments and provide important ecological functions.
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