What Is an Aquatic Ecosystem?

When we speak of aquatic ecosystems, as the name implies, we are referring to ecosystems or environments composed primarily of water. This also includes the biodiversity of flora and fauna and other organisms that exist in that environment.

The aquatic biome is the largest of all biomes, covering about 75% of the Earth's surface. Although they can be studied together or globally, it is common to distinguish between two basic types of aquatic ecosystems, freshwater or saltwater. Marine habitats include the ocean and salty seas, while freshwater habitats include ponds, lakes, rivers, and streams.

Main characteristics of aquatic ecosystems

• They provide habitat for an unimaginable number of species, both those that can live only in water and those that live both in water and on land and/or in the sky. These habitats are essential for species survival and biodiversity.
  
  
• Various physical and chemical elements such as salt concentration, pH, and temperature are the main components of aquatic ecosystems. These factors significantly influence the kind of life forms that can thrive in these environments.
  
  
• They are among the richest ecosystems in the world because of their enormous biodiversity. Invertebrates, vertebrates, and microorganisms share habitats and natural resources through close ecological relationships. These interactions contribute to the balance and sustainability of the ecosystem.
  
  
• The flora of aquatic ecosystems consists of algae and aquatic plants, which play a crucial role in oxygen production and water purification.
  
  
• They have vital functions for the planet, such as helping to regulate the water cycle across the planet, providing habitat for a variety of species that would not otherwise exist, and also acting as filters for pollution. Their existence is fundamental to maintaining ecological balance and supporting life on Earth.

You may be interested in this other article, where we introduce the different types of ecosystems through a list of examples with photos.

In order to facilitate our understanding of aquatic ecosystems, we divide the waters of our planet into two major groups:

• Marine ecosystems
• Freshwater ecosystems

The main difference between the two is that freshwater habitats generally have a salinity of less than 1%, while marine life must adapt to living in a habitat with a high concentration of salt. In both cases, however, the environment is the water and determines the interactions between the plants and animals that make up the ecosystem.

In addition, these types of ecosystems can also be classified according to whether the water is in motion or whether it is still or has little motion. For example, ponds and lakes are both stationary bodies of fresh water, while rivers and streams are moving bodies of fresh water.

At the beginning of a fast-moving river or stream, the water is clear and there is plenty of oxygen. However, as the water flows, impurities can accumulate, reducing the clarity and oxygen content of the water. This variation affects the type of organisms that can inhabit these areas.

Furthermore, it's intriguing to note that the movement of water can also influence sediment distribution, nutrient availability, and habitat structure. This dynamic nature of aquatic ecosystems highlights the complexity of interactions that sustain life within them.

You may be interested in this other article, where we explain what the difference is between biomes and ecosystems.

As a definition of marine or saline aquatic ecosystems, we can say that they are aquatic systems with high salinity found in areas between continents and surrounding islands. Oceanic or marine ecosystems make up 70% of the Earth's surface and 99% of the Earth's volume. It is pertinent to note that we are talking about salt waters like seas and oceans, not salt marshes, which are mixed ecosystems containing both water and land. Their salinity is lower but not as low as freshwater, i.e., brackish water.

In addition, saltwater ecosystems are characterized by great stability, which does not mean that they do not vary. Variables such as solar radiation, temperature and salt concentration and other factors play a role, especially depending on depth.

At depths greater than 1000 meters, most ecosystems are unknown, precisely because the flora and fauna at different depths are so diverse. Nevertheless, it is fair to say that coastal areas are more populous, in stark contrast to a virtually inhospitable ocean floor. This is mainly because the food chain starts with plankton, which needs sunlight to grow.

Three major zones can be distinguished, vertically divided according to the amount of sunlight they receive:

• Euphotic zone: upper layer, sunlight arrives relatively abundantly. This zone supports the majority of marine life due to the availability of light for photosynthesis.
  
  
• Dysphotic zone: layer where sunlight penetrates only weakly. Life here is adapted to less light and often exhibits unique adaptations such as bioluminescence.
  
  
• Aphotic zone: a deeper layer, which does not receive sunlight and contains few nutrients, such as the abyssal plains. The organisms here are adapted to extreme conditions and often rely on detritus falling from upper layers for sustenance.

These zones illustrate the gradient of life that exists within marine ecosystems, highlighting the adaptability and resilience of life forms in varying conditions.

You may be interested in this other article, where we discuss the issue of plastic in the oceans.

As the name implies, freshwater ecosystems are in places where we find freshwater, meaning they have low salinity, such as:

• Rivers
• Ponds
• Swamps
• Lagoons
• Lakes

The salinity of fresh water is logically much lower and is a source of water for drinking and irrigation of plants. The freshwater ecosystem is critical to the survival of most living things, whether fauna, flora, or vegetation, and has a direct impact on the various types of biomes that exist on Earth.

In these ecosystems, we also find a great variety of fish and all kinds of amphibians, with a wide range and typology of vegetation. In fact, about 41% of the world's wealth of fish species live in freshwater.

Various factors such as weather (the sum of vectors such as elevation, temperature, and humidity) and topography determine the characteristics of these habitats. For example, the flora and fauna of a shallow lake in a northern mountain range will be very different from a shallow warm-water lake in a tropical climate zone. In each environment, in each ecosystem, the ideal conditions are created for these life forms to thrive. In fact, we could say that each ecosystem is unique.

Moreover, freshwater ecosystems are vital for maintaining hydrological cycles and providing ecosystem services like water purification and nutrient cycling. These functions are essential for maintaining biodiversity and supporting human activities, emphasizing the need for their conservation and sustainable management.

If you want to read similar articles to What Is an Aquatic Ecosystem?, we recommend you visit our Ecosystems category.