Aquatic Ecosystems and Biomes Quiz

Aquatic Ecosystems or Biomes

• Aquatic ecosystems are primarily classified by abiotic factors, like salinity, which determine the boundaries of aquatic life zones.
• Salinity (the concentration of dissolved salts, such as sodium chloride) in a body of water influences the types of organisms present, as does the dissolved oxygen content.
• Water significantly hinders light penetration, causing photosynthetic aquatic organisms to remain near the surface and bottom vegetation to grow only in shallow water.
• Other factors affecting aquatic species composition include water depth, temperature and pH, and the presence/absence of waves and currents.

Three Main Ecological Categories of Organisms in Aquatic Ecosystems

• Plankton: Free-floating, usually small or microscopic organisms that are weak swimmers. They're carried by currents and waves. Plankton are subdivided into phytoplankton (photosynthetic—the base of most aquatic food webs) and zooplankton (non-photosynthetic—includes protozoa, tiny crustaceans, and larval stages of animals).
• Nekton: Larger, strong swimmers like fish, turtles, and whales.
• Benthos: Bottom-dwelling organisms. Some attach to surfaces (e.g., sponges, oysters, barnacles), others burrow into substrates (e.g., worms, echinoderms), and still others move on the bottom (e.g., crayfish, brittle stars).

Freshwater Ecosystems

• Each freshwater ecosystem has unique abiotic conditions and specific organisms.
• Freshwater ecosystems cover a small portion (about 2%) of Earth's surface but are important in the hydrologic cycle, assisting in recycling precipitation.
• Freshwater also moderates daily and seasonal temperature fluctuations on nearby land. It provides habitats for many species.

Streams and Rivers

• Streams and rivers are flowing-water ecosystems, changing from their source to their mouth (where they empty into a larger body of water).
• Headwater streams are typically shallow, clear, cold, fast-flowing, and highly oxygenated.
• Downstream rivers are wider, deeper, contain suspended particles, are less cold, flow slower, and have less oxygen.
• Human activities (e.g., water pollution, dam construction) affect river and stream ecosystems, altering flow, causing flooding, and changing upstream and downstream conditions.

Lakes and Ponds

• Lakes and ponds are standing-water ecosystems characterized by light penetration zones.
• Littoral zone: Shallow water along the shore with rooted vegetation, many plants and algae, and high productivity. Animals in this zone include frogs, turtles, worms, crayfish, insect larvae, and fish.
• Limnetic zone: The open water beyond the littoral zone, where sunlight penetrates and permits photosynthesis. The main organisms are microscopic phytoplankton and zooplankton, and some fish.
• Profundal zone: The deepest zone, lacking light, where plants and algae do not exist. Dead plants and animals decompose, releasing nutrients.

Freshwater Wetlands

• Freshwater wetlands are transitional ecosystems between aquatic and terrestrial ecosystems, characterized by shallow water, characteristic soils, and tolerant vegetation, including marshes dominated by grasslike plants and swamps dominated by woody trees.
• Wetland plants are highly productive, serving as food sources for a variety of organisms.
• Wetlands also provide wildlife and migratory waterfowl habitats. They store floodwater and reduce flooding in surrounding areas.

Estuaries

• Estuaries are coastal bodies of water where fresh and saltwater mix. Water salinity varies from freshwater at the river entrance to saltwater at the ocean end, creating brackish water.
• Estuaries' salinity, temperature, and other physical properties fluctuate with tides, seasonal changes, and precipitation.
• Organisms in estuaries have a wide tolerance to these changes. Mangrove forests are stable environments for aquatic life, developing in estuaries.

Marine Ecosystems

• The large and complex marine environment is divided into the intertidal zone, the benthic environment (ocean floor), and the pelagic environment (open ocean water).
• Intertidal zone: The shoreline between the highest and lowest tides, high light and nutrient levels.
• Benthic environment: The ocean floor. Zones include Abyssal zone (extending to 4000 – 6000 meters depth) and Hadal zone (more than 6000 meters). Shallow zones consist of seagrass beds, kelp forests, and coral reefs.
• Kelps: Large brown algae. Common in cooler temperate waters.
• Coral reefs: Built from calcium carbonate. Warm waters and higher than 2 degrees Celsius. Growing areas in shallow waters where light penetrates. Consist of many diverse species of marine life.
• Pelagic zone (Open Ocean): Neritic Province (extends from shoreline to 200m depth). Organisms include plankton-eating nekton such as herring, sardines, and manta rays.
• Pelagic zone (Open Ocean): Oceanic Province (deeper than 200m). Organisms are primarily zooplankton and nekton (sharks, tuna, dolphins).

Ecotones

• An ecotone is a transition zone where two communities or biomes meet and integrate.
• Ecotones vary greatly in size and can shift due to changes over time. Examples include where an agricultural area meets a forest or the border between tundra and taiga.

Test your knowledge on aquatic ecosystems and the factors that define different aquatic biomes. This quiz covers essential concepts such as salinity, light penetration, and the ecological categories of organisms like plankton. Challenge yourself and learn more about the fascinating world of aquatic life!