communitiesalgae

Communitiesalgae, or algal communities, are assemblages of photosynthetic organisms that occupy a shared habitat and interact ecologically. They range from microscopic biofilms and periphyton on submerged surfaces to macroscopic assemblages of seaweeds and macroalgae, and include phytoplankton that inhabit the water column.

These communities occur in freshwater, marine, and terrestrial environments, including streams, lakes, coastal reefs, rocky shores, and arid soils where biological soil crusts form. Their structure and diversity reflect gradients of light, nutrients, salinity, and disturbance.

Ecological roles of algal communities are fundamental to ecosystem function. They provide primary production and oxygen, fix carbon, and drive nutrient cycling. They form the base of aquatic food webs and create habitat and food for a range of micro- and macrofauna. Algal assemblages also influence light availability, sediment stabilization, and interactions with bacteria and other microorganisms, contributing to complex microbial networks.

Community composition and dynamics are governed by environmental conditions and biotic interactions. Light, temperature, nutrient availability, grazing, and competition shape which taxa predominate. Disturbances such as pollution, storms, or water management actions can shift assemblages, and succession can move communities through stages toward more stable configurations. In some systems, rapid growth of certain groups leads to harmful blooms that affect water quality and ecosystem health.

Researchers study algal communities with microscopy, pigment analysis, and molecular methods such as DNA metabarcoding, as well as flow cytometry. Satellite and aerial remote sensing of chlorophyll and color indices helps track large-scale phytoplankton patterns. Algal communities are also used as bioindicators of water quality and environmental change.

Threats to algal communities include eutrophication, climate change, ocean acidification, and habitat loss. Conserving diverse algal assemblages supports nutrient cycling, primary production, and the broader resilience of aquatic and terrestrial ecosystems.