Producers in the aquatic ecosystem are phytoplankton. Phytoplankton are microscopic, photosynthetic organisms that drift in the water column. They are the primary producers in the aquatic ecosystem, meaning they are responsible for converting sunlight, carbon dioxide, and nutrients into organic matter through the process of photosynthesis.

Phytoplankton play a crucial role in the aquatic ecosystem as they form the base of the food chain. They are consumed by a variety of organisms, including zooplankton, which are small, drifting animals. Zooplankton, in turn, serve as a food source for larger organisms such as fish and other aquatic animals.

Favorable conditions for phytoplankton growth include an adequate supply of sunlight, nutrients (such as nitrogen and phosphorus), and a stable water column. They are most abundant in nutrient-rich waters, such as estuaries and upwelling zones, where they can thrive and reproduce rapidly.

Phytoplankton are responsible for a significant portion of the Earth's oxygen production. Through photosynthesis, they release oxygen as a byproduct, contributing to the overall oxygen content in the atmosphere. Additionally, they play a crucial role in carbon cycling by absorbing carbon dioxide from the atmosphere and converting it into organic matter.

The abundance and composition of phytoplankton in aquatic ecosystems are influenced by various factors, including temperature, nutrient availability, water movement, and the presence of other organisms. Changes in these factors can have significant impacts on the overall productivity and diversity of the ecosystem.

In conclusion, phytoplankton are the primary producers in the aquatic ecosystem. They are microscopic, photosynthetic organisms that convert sunlight, carbon dioxide, and nutrients into organic matter through photosynthesis. They form the base of the food chain and are vital for the overall health and functioning of aquatic ecosystems.