mesocosms

Mesocosms are controlled experimental systems that simulate aspects of natural ecosystems within a contained environment. They bridge the gap between laboratory microcosms, which are highly simplified, and field experiments, which occur in open ecosystems. By enabling deliberate manipulation of key variables such as nutrient input, temperature, light, or contaminant exposure, mesocosms preserve ecological interactions and biodiversity while allowing replication and systematic study.

Mesocosms are typically larger than microcosms and may be conducted outdoors to expose organisms to natural light cycles and weather, or indoors for tighter control over climate. Common forms include aquatic mesocosms, which contain water, sediments, and aquatic organisms; and terrestrial or semi-terrestrial mesocosms, which involve soil, plants, and soil fauna. Design considerations include size, containment, replication, randomization, and monitoring of physical, chemical, and biological parameters. Potential artefacts—such as tank or edge effects—must be mitigated to avoid bias.

Applications span ecological research, environmental risk assessment, ecotoxicology, climate-change experiments, nutrient cycling and food-web dynamics, restoration experiments, and studies of invasive species. While mesocosms offer realism beyond microcosms, they remain simplifications of true ecosystems and can suffer from scale limitations, unrepresentative species, and artificial boundary conditions. Properly designed mesocosm studies emphasize clear hypotheses, adequate replication, and transparent reporting.