Biotic factors are the living organisms within the particular biome.
This definition means that any living organism within the marine biome is considered a biotic factor. This includes aquatic animals, such as sharks, crabs, dolphins, fish, and eels as well as aquatic vegetation, such as kelp, seaweed, and phytoplankton. The interactions between these biotic factors are important in order to maintain a balance within the different populations in the ecosystem.
Salinity is one of these factors in the marine biome despite the fact that 96.5% of the oceans are composed of pure water. There are more than 70 trillion tons of dissolved substances in Earth's waters. Naturally, the most common dissolved substance is sodium chloride which is commonly known as table salt. This particular factor is very important due to the fact that it salinity varies in different locations. Therefore, organisms in these particular locations have evolved to live in areas that have a certain salinity level. The amount of dissolved substances will also affect the water density.
Organic substances that are dissolved in the water are also considered to be abiotic factors. These are the particles that usually seen suspended in the ocean water and include the remains of dead marine organisms, vitamins, and products of body processes.
pH is yet another important abiotic factor. The pH of the ocean water is vital for the survival of aquatic organisms. If the pH level is either too acidic or too basic, organisms will not be able to survive in the environment, much less flourish into healthy populations.
Limiting factors can be both density-dependent as well as density-independent.
Density-dependent limiting factors are directly related to the size of the populatoins of the organisms. These factors include predation, competiton, disease, mortality, and migration patterns. Obviously, predation plays a significant role in the size of populations and is important for controling population density. Competition is also density-dependent due to the fact that it helps to separate any weak organisms from the healthy ones. Disease and mortality also funciton as density-dependent limiting factors in similar manners. Migration is density-dependent due to teh fact that the organsism will move to different locations when their current environment becomes too crowded.
Density-independent limiting factors are those such as climate extremes and limits in food sources. These factors are considered to be density-independent due to the fact that they are not related to the size of the populations of organisms that are in the ecosystem. Climate extremes are considered to be those that are usually associated with natural disasters, such as hurricanes and monsoons. These clearly affect the population sizes because the climate extremes will destroy valuable habitat as well as killing many organisms in the area. Limits in the amount of available food are also density-independent because the amount of food available will depend on whether or not the environmental conditions, such as temperatures, pH, and levels of dissolved gases, are appropriate in order to maintain an adequate food supply.