What is the Role of Humic Acids in Seawater

Humic acid is the major component of humus which is an organic component of soil. Humic acid is produced by the biodegradation of dead organic matter, and it forms through the combination of acids containing carboxyl and phenyl compounds. Humic acid is usually used as a soil supplement in agriculture, and less frequently, as a nutritional supplement for humans. Humic acids are contained in a variety of sources, most of which come from decomposing vegetation. These substances enter lakes, rivers as a result of soil erosion or industrial wastes, finally reaching the oceans. Humic acid has an adverse effect on marine life.  

Humic acids are the end product of plant and animal microbial degradation, and are one of the major components of fertile soil. They are a complex mixture of partially decomposed organic materials. The process by which humic acid forms is not well understood; however, it is believed that it accumulates as a residue from the metabolism of microorganisms contained in dead organic matter. Its structure is characterized by a loose assembly of aromatic polymers of varying acidity and reactivity. Humic acid formation is partially mediated by aquatic bacteria and enzymes. The components of humic acid include phosphorus, sulfur, nitrogen, as well as over 60 different mineral elements.

Deposition of humic acid on water can occur directly when the contents of humic acid are thrown or sink in the sea or indirectly through soil erosion and industrial spill. The introduction of humic acid into the oceans produces an oversupply of nutrients, which increases the phosphorus and nitrogenous compounds, leading to nitrification (oxidation of ammonia with oxygen).  This decreases the oxygen available in the ocean, which is essential for algal growth, causing the formation of un-ionized ammonia. Light penetration is hindered due to increase algal growth. Algae growth covers a large ocean surface area, preventing sunlight penetration to support plant growth.

Increased quantities of humic acid in the ocean cause an increased production of marine phytoplankton. These organisms have to use oxygen for respiration, which reduces oxygen content in sea water. Without sufficient oxygen, some organisms are unable to survive and die. The remains of marine plants and animals pollute the ocean. Organisms are forced to migrate to other ocean environments for survival. New organisms also migrate to the new created environment. The biodiversity that exists in the oceans is tremendously affected, since only those organisms that can adapt to the changing environmental conditions are able to survive.

Some scientists think that a certain level of humid acid can be beneficial for the oceans, while others warn that high levels of this substance may be harmful. Hemic acids or molecules with similar characteristics to humid acids have probably always been around since the creation of Earth, and organisms have evolved over thousands of years in waters with high concentrations of humid acids. The effect of aquatic humus, also called “yellow substance,” which is composed of fulvic and humid acids has been documented by the American Society of Limnology and Oceanography.

Ocean humic acid substances differ structurally from those of terrestrial origin; this could be due principally from the lignin content in the marine environment and the differences between the terrestrial soil and ocean physical environment . The chemical characteristics of humic and fulvic acid substances were studied using a newly developed procedure of absorption. The formation of seawater humic substances from amino acids, sugars and lipids, and their effects in the sea are discussed in the following research paper in darchive.mblwhoilibrary.org.