Human waste, often called “poop,” enters ocean environments. Human activities significantly increase the volume and alter the composition of organic waste in oceans. This material transforms and moves within the marine environment. Understanding its fate is important for its ecological and health implications.
The Journey of Waste
Organic waste enters the ocean from sources like marine animal waste, human sewage, and land runoff. Sewage, in particular, represents a large volume discharged globally, often due to inadequate sanitation, aging infrastructure, or overwhelmed treatment facilities during heavy rains.
Upon entering the ocean, organic waste disperses and dilutes due to currents and waves. Physical breakdown also occurs, with larger particles fragmenting into smaller pieces.
The waste’s initial density determines if it floats or sinks. Human feces typically sink, though some can float due to trapped gas. As organic matter breaks down, it forms dissolved organic matter (DOM) and particulate organic matter (POM).
Biological Transformation
Marine microorganisms break down complex organic waste into simpler compounds through decomposition. This microbial activity occurs throughout the water column, but is most significant where organic matter accumulates.
During decomposition, these microorganisms release nutrients such as nitrogen and phosphorus back into the marine environment. These nutrients then become available for other marine life, including phytoplankton, which form the base of the marine food web. The organic matter from waste also serves as a carbon and energy source for these microbial communities.
Detritivores and filter feeders also consume particulate organic matter, integrating it into the marine food web. This continuously recycles organic waste throughout the ocean ecosystem.
Ecological and Health Consequences
The influx of organic waste, particularly human sewage, can lead to ecological and public health issues. One major consequence is eutrophication, the over-enrichment of nutrients like nitrogen and phosphorus in the water. This nutrient overload can trigger rapid growth of marine plants and algae, resulting in large algal blooms.
When these algal blooms eventually die, their decomposition by bacteria consumes large amounts of dissolved oxygen in the water. This process can lead to hypoxia (low oxygen) or anoxia (no oxygen) conditions, creating “dead zones” where marine life cannot survive due to oxygen depletion.
Human waste also carries pathogens, which pose risks to both marine life and human health. These pathogens can contaminate seafood or cause illnesses in swimmers who come into contact with contaminated waters. Other pollutants, such as microplastics, pharmaceuticals, and heavy metals, can also be transported into the ocean by human waste, potentially bioaccumulating in marine organisms and affecting human health through the food chain.
Human Role and Management
Human activities influence the quantity and characteristics of organic waste discharged into the ocean. Untreated or inadequately treated wastewater contributes more pollutants compared to properly treated wastewater. An estimated 80% of sewage globally is discharged into the environment without treatment.
Wastewater treatment plants reduce the negative impacts of human-derived waste by removing solids, breaking down organic matter, and disinfecting the effluent before discharge. These facilities aim to reduce the biological oxygen demand and pathogen load of wastewater. However, even treated wastewater can still contain nutrients and other contaminants.
Regulations and individual actions mitigate the burden of human-derived waste on marine environments. Stricter discharge standards, investment in improved wastewater infrastructure, and advanced treatment technologies can reduce pollution. Individual efforts, such as proper waste disposal and supporting sustainable practices, also contribute to minimizing the amount of organic waste entering the ocean.