Читать книгу Plastic and Microplastic in the Environment - Группа авторов - Страница 48

Phytoplankton are considered the main contributor to the primary productivity in the oceans, which fixes almost half of the carbon dioxide of the earth during photosynthesis process by using photosynthetic active radiation (PAR) from Sun and carbon dioxide (Uitz et al. 2010). The MP deposition over phytoplankton decreases the chlorophyll concentration, photosynthesis, cell growth, and morphology of phytoplankton. Microplastics deposited upon the phytoplankton penetrate the cell walls and interfere with the chlorophyll mechanisms in green algae (Nerland Bråte et al. 2014). Phytoplankton absorb persistent organic pollutants released during the degradation of MPs which is further transferred along the marine food web (Chandra et al. 2020). This hazardous chemical has the property of bioaccumulation in successive trophic levels, which causes toxicity to them. When MPs are deposited over harmful alga, they release phycotoxin, which is transferred to phytoplankton, bivalves, and crustaceans (Sharma & Chatterjee 2017). The toxins are then bioaccumulated in their bodies and move to the next trophic level. These are then consumed by humans, which may result in many health issues. The coral reef, which has the highest biodiversity in the tropical shallow parts of marine realm, is also badly impacted by MPs. These coral reefs have the mutual collaboration of algae and fungi. However, most of the time, algal partners depend on phytoplankton, zooplankton, etc., for their food requirements, but they are confused by the colorful MPs and consume them. The digestive tracts of coral reefs (coral polyps) cannot deal with MPs and they have very harmful impacts on their health.

Figure 3.1 Flow diagram of the fate of plastic entering the environment.

These phytoplankton are trapped as part of the marine snow and an important constituent of marine organic matter, this organic matter is taken as food by benthos and nektons. Marine algae aggregates over the floating MPs and settle down to the sediment water interface. This reduces the residence time of floating organic matter in the water column, which in turns lowers the food availability to those organisms residing in the water column. Furthermore, hetero‐aggregates of MP and phytoplankton are consumed by zooplankton and have harmful impacts to them. These MP contaminated zooplankton are bioavailable to the predator and transferred to successive trophic levels. In these ways MP potentially disturbs the food transfer and, most importantly, reduces the energy flow from primary producers level.