Aquatic ecosystem

**Types of Aquatic Ecosystems:**
– Marine ecosystems cover over 70% of Earth’s surface and account for more than 97% of Earth’s water supply.
– Seawater has an average salinity of 35 parts per thousand.
– Marine ecosystems can be divided into zones based on water depth, including near-shore zones like mudflats, seagrass meadows, and coral reefs.
– Marine coastal ecosystems have high biodiversity and productivity.
– Freshwater ecosystems include lakes, rivers, and wetlands, containing 41% of the world’s known fish species.
– Freshwater habitats can be classified as lentic (still water bodies like lakes) or lotic (flowing waters like rivers).
– Wetlands are biologically diverse, play important roles in water treatment, and are designed for wastewater treatment.

**Functions of Aquatic Ecosystems:**
– Aquatic ecosystems recycle nutrients, purify water, attenuate floods, and recharge groundwater.
– They provide habitats for wildlife, contribute to self-purification, and are used for human recreation and tourism.

**Biotic and Autotrophic Characteristics:**
– Wetland plants and herbivores interact in aquatic environments.
– Autotrophic organisms like algae use solar energy for biomass generation.
– Chemosynthetic bacteria feed on hydrogen sulfide in benthic ecosystems.
– Algae are key autotrophic organisms in aquatic environments.

**Heterotrophic and Abiotic Characteristics:**
– Organisms show salt tolerance in different ecosystems.
– Heterotrophic organisms consume autotrophic organisms for energy.
– Abiotic factors like substrate type, water depth, temperature, and nutrient levels influence aquatic life presence.
– Salinity and dissolved oxygen levels impact species distribution in water bodies.

**Threats to Aquatic Ecosystems:**
– Human activities exceed aquatic ecosystems’ capacity to absorb stress.
– Climate change disrupts distribution patterns of aquatic plants and animals.
– Over-harvesting, pollution, and invasive species contribute to ecosystem decline.
– Physical, chemical, and biological alterations degrade ecosystem health.