Aquatic ecosystem

Lore & Background

Aquatic ecosystems perform many important environmental functions, including recycling nutrients, purifying water, attenuating floods, recharging ground water, and providing habitats for wildlife. The biota—microorganisms, phytoplankton, higher plants, invertebrates, fish, bacteria, protists, aquatic fungi, and more—contribute to self-purification through organic matter destruction and water filtration. These ecosystems are reliably self-maintained and also serve human recreation, tourism (especially in coastal regions), religious purposes (such as religious tourism to the Jordan River by Christians), and educational purposes (such as the usage of lakes for ecological study).

Biotic characteristics are mainly determined by the organisms that occur. For example, wetland plants may produce dense canopies covering large areas of sediment, or snails or geese may graze vegetation leaving large mud flats. Aquatic environments have relatively low oxygen levels, forcing adaptations such as aerenchyma in many wetland plants to carry oxygen to roots. Other biotic characteristics include the relative importance of competition, mutualism, or predation, with growing cases where predation by coastal herbivores (snails, geese, mammals) appears dominant.

Autotrophic organisms, such as algae, use solar energy to generate biomass from carbon dioxide and are possibly the most important autotrophs in aquatic environments. In shallower water, rooted and floating vascular plants contribute greater biomass. Chemosynthetic bacteria in benthic marine ecosystems feed on hydrogen sulfide from volcanic vents, supporting great concentrations of animals like giant tube worms and clams. Heterotrophic organisms consume autotrophs, and euryhaline organisms tolerate salt while stenohaline species live only in freshwater.

Reader's Guide

Aquatic ecosystems are significant because they perform essential environmental functions such as nutrient recycling, water purification, flood attenuation, groundwater recharge, and wildlife habitat provision. Their self-purification capacity relies on a diverse biota including microorganisms, phytoplankton, higher plants, invertebrates, fish, bacteria, protists, and aquatic fungi. These ecosystems are also used for human recreation, tourism, religious practices, and education. Abiotic factors like substrate type, water depth, nutrient levels, temperature, salinity, flow, and dissolved oxygen determine the kinds of organisms present. Dissolved oxygen is frequently the key substance controlling organic life; fish need it to survive, though tolerance varies, and plants may produce aerenchyma or alter leaf shape. Nutrient levels, especially nitrogen and phosphorus, control algae abundance, which can become over-abundant and cause fish declines or hypoxic dead zones. Salinity determines species composition, with marine organisms tolerating salt and many freshwater organisms intolerant. Threats include physical, chemical, or biological alterations that exceed the ecosystem's ability to absorb stress, such as changes in water temperature, flow, light, nutrient loading, toxins, over-harvesting, and exotic species introduction. Human populations impose excessive stresses, and climate change disrupts distribution patterns, negatively impacting deep sea biodiversity, coastal fish diversity, crustaceans, and coral reefs. Human-made aquatic ecosystems like ditches, aquaculture ponds, and irrigation channels can harm natural ecosystems by trading off biodiversity.

Did You Know?

• The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.
• Freshwater ecosystems include lentic (slow moving water), lotic (faster moving water), and wetlands.
• Dissolved oxygen is frequently the key substance determining the extent and kinds of organic life in a water body.