Mucilage Formation and Its Effects on the Sea of Marmara (Part-2)

2.1.2. Marine snow, which is natural macroscopic lumps rich in organic matter and containing , is seen in open seas and oceans, and forms an significant component of carbon transport and cycling (biological pump) in large masses of water [17].

The “biological pump” is the process through which photosynthetically-produced organic matter in the ocean is exported from the surface layer to depth by a combination of sinking particles, advection or vertical mixing of dissolved organic matter, and carrying by animals.

Figure 2. 3 Central role of marine snow in the ocean carbon pump

Phytoplankton fix CO2 in the euphotic zone using solar energy and produce particulate organic carbon (POC). POC formed in the euphotic zone is processed by microbes, zooplankton and their consumers into organic aggregates (marine snow), which is thereafter exported to the mesopelagic (200–1000 m depth) and bathypelagic zones by sinking and vertical migration by zooplankton and fish. Export flux is defined as the sedimentation out of the surface layer (at approximately 100 m depth) and sequestration flux is the sedimentation out of the mesopelagic zone (at approximately 1000 m depth). A portion of the POC is respired back to CO2 in the oceanic water column at depth, usually by heterotrophic microbes and zooplankton, thus maintaining a vertical gradient in concentration of dissolved inorganic carbon (DIC). This deep-ocean DIC returns to the atmosphere on millennial timescales through thermohaline circulation. Between 1% and 40% of the primary production is exported out of the euphotic zone, which attenuates exponentially to the base of the mesopelagic zone and just about 1% of the surface production reaches the sea floor [18].


2.2. Possible Mechanisms-Causes of Mucilage
Mucilage needs oxygen dissolved in water to be broken down. An substantial variable for equilibrium the oxygen level in the water is the ideal temperature of the water. But, with global warming and pollution of sea waters (such as sea pollution, flocculation, the accumulation of sun rays, causing an increase in temperature; increasing oxidation and lowering the oxygen level), the sea waters get warmer and the oxygen level decreases [19].
Among the different possible mechanisms in the context of mucilage formation processes, the following can be listed:
• The release and leakage of carbohydrates produced as excess primary production (photosynthesis) by phytoplankton under stress conditions to the marine environment,
• death and cell fragmentation and the mixing of structural polysaccharides from cell wall residues into the marine environment,
• As a result of death and cell fragmentation/lysis, cellular contents containing high amounts of dissolved organic matter (DOM) and polysaccharides are mixed into the marine environment,
• accumulation of high molecular weight organic compounds/polymers over time due to limited bacterial hydrolysis and biodegradation,

• mixing and accumulation of organics in the cell contents into seawater as a result of viral infection and cell lysis of prokaryotes and phytoplankton in the entity of viruses [7].