Digging into the issue concerning the effect of water sedimentation on organisms, I decided to figure out the meaning of the term water sedimentation. I found out that it is a process in which particles (silt, sand, and gravel) settle to the bottom of water’s body due to gravity, centrifugal acceleration or electromagnetism.
In aquatic environments, the presence of sediment is inevitable because it is a part of the ecosystem. Plants and animals inhabiting waters can be neutrally or negatively affected by sediment. Much depends on its type: it can be algae or suspended particles of soil from an eroded shoreline. Many owners of farms in the United States dump wastes into waters. Toxic materials contained in wastes damage the habitat of aquatic dwellers and sometimes even kill them.
Storms, floods and extreme tides can also cause severe changes in sedimentation, but it is also humans’ fault. Many freshwater species go extinct on that ground since sediment contributes to the alteration of local food webs and habitat. The water becomes turbid, thus decreasing light penetration into the body of water. As a consequence, phytoplankton reproduces weaker. Moreover, more importantly, turbidity increase causes a reduction in plant growth, including algae. Herbivorous insects and fishes starve to death because there aren’t enough resources for all. Large plants (macrophytes) lose useful nutrients when sediment settles on it. “Increases in sedimentation rates can also alter the interactions between organisms and their habitats. Juveniles of many fish species and other organisms depend on mangroves and seagrass bed for food and shelter, moving to deeper waters and offshore reefs as they mature. Deterioration of any of these ecosystems can lead to a decline in fish populations” (Rogers, 1990).
As everything is connected, the reduction of phytoplankton will result in a decrease of available food energy. Macroinvertebrates also suffer from sedimentation because it actively destroys its habitat. The reduction of the hyporheic level of oxygen makes its existence impossible.
Well, it is not so bad for insects; such an environment contributes to its burrowing, while density and biomass in benthic macroinvertebrate communities decrease. “An increase in turbidity of only 5 NTU decreased primary production by 3 to 13%, and increases of 25 NTU decreased primary production up to 50%” (Henley et al., 2000).
Finally, about mussels, they get food by filtering water through their bodies and toxic materials can easily contaminate mussels’ tissues. It seems that the ecosystem will be ruined and many fish and other inhabitants will suffer from lack of resources and deterioration of the environment. Deposited and suspended sediments negatively affect the survival of freshwater mussels. For example, Yellow sandshell will not survive if the level of deposited silt is 0, 6 cm and higher. F. Flava and P. Grandis are the most vulnerable species. At the same time, three-horn wartyback, maple leaf, and monkeyface are more resistant to such environment. Such species as giant floater prefers to live in detritus, sand or silt.
By this data, I can conclude that there are species of freshwater mussels, which are sensitive to silt and sand but they are in the minority. A significant number of species is still tolerant of such an environment. Vulnerable species (a pimple black, southern pigtoe and Mississippi pigtoe) faced starvation, and resilient (blue mussel, the eastern oyster) have learned to adjust. Many of the endangered freshwater mussel species have evolved in streams with low levels of suspended sediment that is why they can be unable to distinguish organic from inorganic particles in water. All this leads to a lack of food and further reduction of reproduction volumes.
Henley, W.F., Patterson, M.A., Neves, R.J., Lemly, A.D. (2000). “Effects of sedimentation and turbidity on lotic food webs: A concise review for natural resource managers.”
Rogers, C.S. (1990). “Responses of coral reefs and reef organisms to sedimentation.”