Microbial turnover is the continuous cycle of death, decomposition and replacement of microorganisms, including bacteria, fungi and archaea. This process is fundamental to nutrient cycling, ecosystem functioning, and overall biodiversity.
Microbes die due to factors such as predation by protozoa, competition for resources, viral infections, chemical fluctuations (such as in pH and oxygen levels) and environmental stresses. As they die and decompose, they release essential nutrients back into the environment, making them available for other organisms.
While microbes are individually extremely small, with bacteria typically ranging from about 0.5 to 5 micrometers (0.0005 to 0.005 millimeters) in length, they collectively contribute significantly to the earth's biomass. Bacteria alone can account for a large fraction of microbial biomass in many ecosystems. Microorganisms together have an enormous total carbon mass, currently estimated at roughly 70 to 100 billion metric tons, or about 15 to 20 percent of the earth's total biomass of 550 billion tons of carbon. This immense presence underscores their critical role in environmental health.
Turnover rates can affect microbial community composition and diversity, and thus affect ecosystem resilience and function. They are crucial for biogeochemical cycles, such as those for carbon, nitrogen and phosphorus, because they represent the rate at which nutrients are cycled between microbial biomass and the environment.
Microbial turnover rates are influenced by several factors, including temperature, moisture, nutrient availability, and community composition. Generally, higher temperatures within biologically suitable ranges accelerate both the growth and death rates of microbes, leading to increased turnover. However, extremely high temperatures can inhibit microbial activity. Similarly, abundant nutrients can speed up turnover, while nutrient limitations can slow microbial growth and decay.
Human activity, such as agriculture and the burning of fossil fuels, strongly affect microbial turnover by altering soil properties, nutrient availability and temperature patterns. These changes can disrupt the balance and diversity of microbial communities, which in turn influence resource cycles and even contribute to climate change. Additionally, altered microbial turnover due to human activity can negatively affect local plant health and biodiversity.
Strategies to help maintain or restore favorable microbial turnover include (1) reducing environmental stresses that harm microbes, such as pollution and soil salinity, (2) protecting natural habitats to preserve the diversity of microbial communities, (3) adopting sustainable agriculture practices such as crop rotation, reduced tillage, and the use of organic inputs to improve soil health and microbial diversity, (4) carefully managing nutrient inputs to avoid excesses or deficiencies that disrupt microbial balances, (5) utilizing biotechnological solutions such as biofertilizers and microbial inoculants to enhance beneficial microbes and (6) mitigating climate change and thus its effects on temperature and moisture patterns.