Figure 4: A Black Devil Angler fish common in the bathypelagic zone

1. Changes in biological communities from Epipelagic to Bathypelagic and the factors that influence them. Introduction The ocean is divided into various layers distinguished by depth and ecology. The layers include the epipelagic, mesopelagic and the bathypelagic. Each of these layers are characterised by a unique set of environmental conditions that determine where respective communities can occur. These environmental factors include light , food availability, oxygen, temperature , density and salinity. 0 m…………………………………………………………………………………………………....………………… The epipelagic zone ,also known as the photic zone is the uppermost zone of the ocean zones and stretches from the surface down to 200m. The most light is found in this zone which allows photosynthesis , which can only occur in this zone due to sufficient light, since the other zones are limited by light(figure 1). Thus it is the only zone in which plants can survive. There oxygen available is a result of the direct contact of this zone with the atmosphere as well photosynthesis which produces. Primary production occurs in the zone and as a consequence more food is available. The availability of oxygen and food results in more animals that occur in this zone. The zone is responsible for inputs that reach the other zones. With light come heat which is responsible for the wide range of warm temperatures found in this zone. The temperature in this zone varies with season and latitude. Warm waters are less dense and less saline. The pressure in this zone is low compered to the other zones as it increases with depth(figure 3). Epipelagic Zone Figure 1: The depth to which the various light wave lengths penetrate the open ocean. Figure 2: Turtles and sharks are common in the epipelagic zone. Image available from: science.kennesaw.edu Image available from: library.thinkquest.org -200 m…………………………………………………………………………………………..…………………………………………………………. The mesopelagic zone is found below the epipelagic zone and extends from 200m to 100om. Light penetrates up to only a certain depth the rest of the zone is entirely dark(figure 1). The only light is produced by organism themselves through bioluminescence. No plants occur in this zone as a result of insufficient light and therefore no photosynthesis occurs , there is also no contact with the atmosphere which leads to reduction of oxygen levels. Animals have more developed gills to deal with the reduced oxygen levels. Insufficient light leads cascading effects such as a loss of primary production which in turn leads to reduction of food supply. Therefore less animals are found in this zone. Animals found here feed on detritus that passed from the epipelagic zone, at night some animals swim to epipelagic zone to feed. The mesopelagic contains a thermocline which indicates a rapid change in temperature. The temperature decreases from surface temperature to 4-5 degrees ,with cold temperatures the waters are more dense water and more saline, there is also an increase in pressure with depth(figure 3). b Mesopelagic Zone c a Figure 3: Changes with depth: a) temperature b) salinity c) density Image available from: hurricanescience.com -1000 m……………………………………………………………………………………………………………………….…………………….…….. Directly below the mesopelagic zone lies the bathypelagic zone which expands from 1000m to 4000m. The zone has no light because the natural light available cannot reach beyond the mesopelagic zone and it is therefore completely dark in this zone. Though light is produced by bioluminescence by animals.(fiurgure 4) As a result of no light , no plants are found in this zone since they unable to photosynthesize. No primary production occurs in this zone and as a result food is scarce and oxygen depleted. Due to light unavailability there are no primary consumers, however there are predators and detritus feeders. The detritus feeders consume the debris free-falling from the epipelagic and mesopelagic zone. This zone is characterized by cold water with a constant temperature of 4degrees and more dense water. This zone also has an immense pressure and more saline conditions these conditions are less variable than in the mesopelagic and epipelagic and remains constant. Bathypelagic zone Table 1: Change in fish community from zone to zone which is associated with the environmental factors of each zone Conclusion Figure 4: A Black Devil Angler fish common in the bathypelagic zone Image available from: deepsea news.com The environmental factors which include light, food availability, oxygen, temperature , density and salinity, change with depth and either increase or decrease. The biological communities found within each layer is adapted to the characteristics that define each layer to ensure that they survive. (table 1) Nicole lockett 3032759 Pita 3030288 Jody Taft 3135346 word count : 633 >-4000 m…………………………………………………………………………………………………………………………………………………