A biome is a large-scale ecological community defined by its climate, vegetation, and animal life. Aquatic biomes are major life zones found in water environments, covering about 75% of Earth’s surface. These biomes encompass a vast array of habitats across the globe, supporting a wide diversity of species.
Key Characteristics of Aquatic Biomes
Water serves as the primary medium for aquatic biomes, possessing unique properties. Salinity, the salt concentration, is a fundamental characteristic differentiating aquatic biomes into freshwater and saltwater categories. Light penetration, another factor, creates distinct zones: the photic (or euphotic) zone, where sunlight allows photosynthesis to occur, and the aphotic zone, where light is insufficient for this process.
Temperature variations influence aquatic environments, leading to thermal stratification in many bodies of water. This layering occurs because water density changes with temperature, with warmer, less dense water often floating above cooler, denser water. Dissolved oxygen levels are important, as aquatic organisms require oxygen for respiration. Cold water holds more dissolved oxygen than warm water. Water movement, such as currents, waves, and tides, shapes aquatic environments by distributing nutrients, oxygen, and influencing the types of organisms.
Freshwater Biomes
Freshwater biomes are characterized by low salt content. Organisms in these environments have adapted to low salt conditions. These biomes are found across terrestrial landscapes and are influenced by surrounding land-based factors.
Lakes and ponds are examples of standing freshwater bodies. They often exhibit zonation, including littoral (nearshore), limnetic (open water), profundal (deep, dark), and benthic (bottom) zones, each supporting different life forms.
Rivers and streams, in contrast, are flowing freshwater systems with characteristics like current strength and oxygenation impacting their inhabitants. These flowing waters can transport sediments and nutrients. Wetlands, such as marshes and swamps, are areas where the soil is saturated with water for at least part of the year. They are highly productive and play a role in filtering water.
Saltwater Biomes
Saltwater biomes have a high salt concentration. These biomes cover approximately 71% of Earth’s surface. Marine organisms possess specialized adaptations to manage their salt balance in these environments.
Oceans represent the largest saltwater biome, characterized by size, depth, and pressure. They are divided into vast zones, including the intertidal (shoreline), neritic (over the continental shelf), oceanic (open ocean), benthic (ocean floor), and abyssal (deepest parts) zones.
Coral reefs are biodiverse ecosystems found in warm, shallow ocean waters. They are built by coral polyps that have a symbiotic relationship with algae, which contributes to their productivity.
Estuaries are transitional zones where freshwater from rivers mixes with saltwater from the ocean. These productive areas serve as nurseries for many marine species due to their unique blend of conditions. Intertidal zones, found between high and low tide marks, experience daily exposure to air and water. Organisms living here must adapt to fluctuations in moisture, temperature, salinity, and strong wave action.
Ecological Roles of Aquatic Biomes
Aquatic biomes are important to global ecological processes. They support a wide variety of species, many of which are found nowhere else. This biodiversity is important for maintaining healthy ecosystems worldwide.
These biomes also play a role in global cycles, including the water cycle through evaporation and precipitation. Oceans, in particular, are important for regulating Earth’s climate by absorbing and distributing heat around the planet.
Aquatic environments facilitate the cycling of nutrients like nitrogen, phosphorus, and carbon. Microorganisms within these biomes are important in transforming and recycling these nutrients, making them available for primary producers. Aquatic biomes also provide resources, serving as sources of food, such as fisheries, for human populations.