What process is characterized by excess nutrients leading to algal blooms and low oxygen levels?

Eutrophication is the process that occurs when excess nutrients, particularly nitrogen and phosphorus, are introduced into water bodies, typically from agricultural runoff, sewage discharge, or fertilizers. This nutrient overload stimulates the rapid growth of algae, leading to algal blooms. As these algae die and decompose, a significant amount of oxygen in the water is consumed during the decomposition process, resulting in low oxygen levels, or hypoxia. This reduction in oxygen can create an environment inhospitable to aquatic life, often resulting in the death of fish and other organisms.

Photosynthesis, while related to algae and aquatic plants, refers specifically to the process through which plants and algae convert light energy into chemical energy using carbon dioxide and water, producing oxygen as a byproduct. Osmosis involves the movement of water across a semi-permeable membrane and is unrelated to the nutrient dynamics that characterize eutrophication. Transpiration is the process by which water evaporates from the surfaces of plants, contributing to the water cycle, but it does not pertain to nutrient levels or algal growth in aquatic ecosystems.