International Journal of Marine Science, 2024, Vol.14, No.1, 6-13 http://www.aquapublisher.com/index.php/ijms 11 rates of planktonic organisms (Sun and Ning, 2005). Some planktonic species exhibit stronger feeding capabilities under high salinity conditions, while others may have a competitive advantage under lower salinity conditions. Furthermore, salinity can impact the efficiency of nutrient absorption and utilization by plankton. For instance, some planktonic organisms may have more efficient absorption and utilization of nutrients such as nitrogen and phosphorus in high salinity environments. Planktonic organisms play crucial roles in marine food webs, including photosynthesis, predators, and decomposers. Salinity fluctuations can influence their growth rates, biomass, and population structure, thereby altering their positions and impact within the food web. Under high salinity conditions, certain planktonic plants may exhibit higher growth rates, which can affect the grazing pressure and competitive relationships among planktonic animals. Salinity also influences biological interactions among planktonic organisms, such as symbiosis, predation, and competition, further leading to changes in the overall structure and ecological functions of plankton communities. Salinity is one of the key driving factors for the mixing and stratification processes in oceanic water. Variations in salinity can affect water density and stability, subsequently influencing vertical mixing and the formation of water masses. These mixing and stratification processes directly impact the distribution and geographical dispersion of planktonic organisms. Salinity gradients can result in vertical stratification and spatial heterogeneity in the marine environment, leading to the existence of different types of planktonic communities under varying salinity conditions. Some planktonic organisms are better adapted to the high-salinity surface waters. This vertical distribution and spatial heterogeneity have significant implications on the ecological processes and population dynamics of plankton, including growth, reproduction, and migration (Gasol et al., 2003). 3 The Impact of Human Activities on Surface Floating Biological Communities Human activities have caused a large amount of pollutants (including acoustic pollution) and carbon dioxide to enter the ocean, such as chemicals, petroleum products, pesticides, industrial wastewater, waste, and noise generated by marine engineering activities (Figure 4). These pollutants have direct or indirect impacts on surface floating biological communities (Barry et al., 2023). Toxic substances can cause damage to the survival and reproductive abilities of plankton, leading to population declines or extinctions. Pollutants may disrupt the ecological functions of plankton, such as photosynthesis, feeding, and decomposition, thereby affecting the stability of food webs and nutrient cycling. The influx of significant amounts of carbon dioxide into the atmosphere, a portion of which is absorbed into the oceans, results in ocean acidification. Ocean acidification has a particularly noticeable impact on surface floating biological communities. Acidified seawater can reduce the calcification ability of planktonic organisms' shells and skeletons, affecting their biological structure and function. Organisms like corals and foraminifera are especially sensitive to acidification, putting their survival and reproductive capacities at significant risk. Figure 4 Marine microplastic pollutants (Image source: https://cn.bing.com/)
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