MUCILAGE FORMATION and ITS EFFECTS on the SEA of MARMARA (PART-1)
MUCILAGE FORMATION and ITS EFFECTS on the SEA of MARMARA
1. INTRODUCTION
Earth is the third closest planet to the Sun in the Solar System and is presently the only astronomical object known to have life and liquid water on it. According to radiometric dating and other evidence, it was formed more than 4.5 billion years ago.
While approximately 29% of the Earth's surface is land made up of continents and islands; The remaining 71%, which is covered with water, is called the hydrosphere, which is formed by oceans, lakes, streams and other fresh waters.
The oceans cover more than two-thirds of our planet's surface and, when viewed in three dimensions, occupies a huge volume, much of which has yet to be discovered. Rich in resources, oceans ensure humans with nutrients, energy and minerals [1]. A sea is a body of water that is connected to an ocean and envelope a large area and is generally salty. The term is often used interchangeably with the term ocean. The seas, which provide food and livelihood for more than a billion people, produce almost half of the oxygen we breathe. The seas are home to an highly rich wildlife, from microscopic plankton to the largest mammal blue whale ever.
Oceans are thermal regulators that absorb carbon dioxide. Because they cover almost the whole planet, large amounts of CO2 are absorbed by their waters. At night, they emit the heat they receive during the day when there is sunlight; frequently sends water vapor into the atmosphere, thus forming clouds. Thanks to this absorption and emission cycle, the temperature of the planet remains more or less constant. The World Ocean is home to 230,000 known species; however, as many remain undiscovered, the number of species situated in the ocean is much greater, probably over two million [2].
The pollution of the oceans, which covers a very large area, has been a great threat to sea creatures especially in the last thirty years. The most significant causes of ocean pollution are plastic waste, the increasing amount of carbon dioxide in the atmosphere and the spilling of oil transported by sea into the oceans [3].
Mucilage, which can also be called marine snow or spit (sea snot); It can be defined as a thick, sticky matter secreted or infiltrated by plants and some microorganisms in the sea. This substance; It has a sticky and gel-like structure consisting of extracellular polysaccharides with high viscosity; It can host viruses, bacteria, phytoplankton and zooplankton. While this secretion is mostly suspended in the form of a ghost network in the first stage, if it combines with the solids in the sea, it can become heavier and settle to the bottom, and if it combines with dissolved gases in the water, it can become visible on the surface of the sea. Although it is often not possible to say that the formation of mucilage is caused by a only reason, three main factors can be mentioned. These; The increase in sea temperature can be listed as the stagnation of the sea and the increase in nutrients, in other words, the pollution load. People can be exposed to marine pollution by ingestion as a result of consuming sea creatures, absorption as a result of contact, inhalation of aerosols, recreational use (swimming etc.) or occupationally [4].
2. GENERAL INFORMATIONS
2.1. Mucilage
Marine mucilage, also known as sea snot or marine snow, is a mucus-like particulate organic matter found in the sea [5]. The first event was recorded in the scientific literature in the North Adriatic Sea in 1729 [6]. Mucilage is formed when small sized lumps come together under the affect of factors such as heating of the water surface and stratifying in the water colon [7].
Phytoplankton, which is the first step of biological production in the sea, mucilage into seawater when reproduced with the trigger of some environmental determinants. Mucilage is an sometimes or recurrently occurring global phenomenon in several coastal areas[8,9,10,7 11].
2.1.1. What is phytoplankton
The term phytoplankton, first used by Victor Hensen in 1887, revolutionized the field of marine biology and it was revealed that phytoplankton consist of the basis of the marine food chain [12]. The word plankton is derivatived from the Greek word planktos meaning "drifting" and does not float on its own or stay in one place like coral; It typifies the smallest living entity in the aquatic environment that stays suspended and moves below the influence of tides, currents and other factors. At the same time, plankton form the basis of food pyramids in freshwater and marine ecosystems that procure food for a wide variety of types, from small shellfish to whales [13].
Although plankton can change their depth through active swimming and changes in buoyancy, they are unable to act independently of ocean flows. Plankton vary hugely in size from viruses and bacteria only a few microns in diameter up to jellyfish standing 10s of kg [14]
Some phytoplankton are bacteria, some are protists, and most are single-celled plants. Among the common species are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores. For example Figure 1. [15]
Figure 1: Phytoplankton are exceedingly various, varying from photosynthesizing bacteria (cyanobacteria), to plant-like diatoms, to armor-plated coccolithophores (drawings not to scale). (Collage adapted from drawings and micrographs by Sally Bensusen, NASA EOS Project Science Office.)
Like land plants, phytoplankton have chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. They consume carbon dioxide, and release oxygen. All phytoplankton photosynthesize, but some get additional energy by consuming other organisms.
Bacteria that break down phytoplankton consume the oxygen in the water, suffocating animal life; As a result, a dead zone is formed. Phytoplankton can also be the precursor of death or disease. Some species of phytoplankton produce powerful biotoxins, making them responsible for so-called “red tides,” or harmful algal blooms. These toxic blooms can kill marine life and people who eat contaminated seafood.
Figure 2: Phytoplankton are exceedingly various, varying from photosynthesizing bacteria (cyanobacteria), to plant-like diatoms, to armor-plated coccolithophores (drawings not to scale). (Collage adapted from drawings and micrographs by Sally Bensusen, NASA EOS Project Science Office.)
Harmful phytoplankton varieties become dominant by increasing with the change of trophic conditions in aquatic environments that are under the pressure of many environmental problems such as pollution, overfishing, invasive species, and climate change. The overgrowth of these harmful phytoplankton varieties is often referred to as harmful algae growth or algal bloom, and as a result; a high amount of extracellular polymeric organic substances is secreted from the large number of living cells newly formed. Figure 2. shows some of the damages it caused. These extracellular organic substances called mucilage; it is usually produced by diatoms and dinoflagellates [16].
