Pelagic Environments and Ecosystems (1)
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The pelagic zone is the largest habitat on Earth, encompassing 330 million cubic miles of the open ocean. Within this zone, various species of pelagic fish and plankton are found throughout in numbers and distributions that vary depending on factors like light availability, nutrients, temperature, and pressure. The photic zone near the ocean's surface experiences a daily cycle of light and dark that is a powerful environmental signal, influencing diel vertical migrations of organisms seeking their optimum light intensity. Upwelling regions bring nutrients into surface waters, supporting highly productive marine ecosystems and fisheries. Plankton are primary producers and consumers that drift with ocean currents, and include phytoplankton like diatoms, dinoflagellates
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Pelagic Environments and Ecosystems (1)
- 2. The Pelagic Zone “The pelagic zone is the largest habitat on earth with a volume of 330 million cubic miles. Different species of pelagic fish are found throughout this zone. Numbers and distributions vary regionally and vertically, depending on availability of light, nutrients, dissolved oxygen, temperature, salinity, and pressure.” https://oceanservice.noaa.gov/facts/pelagic.html
- 6. “Photic Zone” “Light” “For animals in the photic zone of the world's oceans, the daily cycle of light and dark is perhaps the most powerful environmental signal available. One of the earliest reports indicating light as a primary factor in vertical migration was by Russell in 1927, who suggested that zooplankton occupied depths that had an optimum light intensity. He further suggested that, as animals moved away from this optimum intensity, physiological reactions controlled by photochemical mechanisms stimulated them to return to the zone of optimum light intensity. Later reviewers concluded there was abundant (albeit circumstantial) evidence implicating light as a significant factor regulating the vertical migration of fish. This evidence included the timing of vertical migration with respect to dusk and dawn, a lack of vertical migration at high latitudes, and the results from experiments with artificial lights and during solar eclipses. “Researchers have elaborated on the concept of a preferred level of illumination by developing mathematical models to describe the diel vertical migration of fish based on light, and have developed expressions to predict the depth range over which vertical migration should occur. However, other studies have suggested that differences in water transparency will have a stronger influence on diel vertical migrations of fish than the surface illumination, since the attenuation coefficient determines the light intensity at depth.” -- J.D. Neilson, R.I. Perry, in Encyclopedia of Ocean Sciences (Second Edition), 2001 https://www.sciencedirect.com/topics/earth-and-planetary-sciences/photic-zone
- 10. “Upwelling Ecosystems” “Upwelling brings inorganic nutrients into surface waters of the ocean that, in well- lit surface layers, results in some of the most productive marine ecosystemsworldwide. Upwelling regions can broadly be divided into coastal Eastern boundary currents and open ocean systems, both characterized by surface layer Ekman divergence. Major commercial fisheries associated with Eastern boundary currents are based on shoals of sardines, anchovies, and mackerel that thrive on abundant phytoplankton and zooplankton food resources. Planktonic algae and animals avoid being swept away from upwelling centers to less favorable habitats by evolving behavioral adaptations to overcome this, but the survival of small pelagic fish are particularly affected by physical circulation patterns. Community structure in upwelling ecosystems is therefore sensitive to climate variability and change, with fluctuations in fish numbers impacting on both higher and lower trophic levels.” --T.R.Anderson & M.I.Lucas Encyclopedia of Ecology 2008, Pages 3651-3661 https://www.sciencedirect.com/science/article/pii/B9780080454054003633
- 11. https://www.youtube.com/watch?v=KfEOh-tjmoM “THE EXTREME LIFE OF THE SEA” (Steve Palumbi, Stanford)
- 12. Plankton “The word “plankton” comes from the Greek for ‘drifter’ or ‘wanderer.’ An organism is considered plankton if it is carried by tides and currents, and cannot swim well enough to move against these forces. Some plankton drift this way for their entire life cycle. Others are only classified as plankton when they are young, but they eventually grow large enough to swim against the currents. Plankton are usually microscopic, often less than one inch in length, but they also include larger species like some crustaceans and jellyfish. “Scientists classify plankton in several ways, including by size, type, and how long they spend drifting. But the most basic categories divide plankton into two groups: phytoplankton (plants) and zooplankton (animals).” • https://oceanservice.noaa.gov/facts/plankton.html
- 14. Phytoplankton
- 24. “Primary Producers: Phytoplankton” “Resource competition is one of the key ecological processes that control species composition, diversity, and succession of phytoplankton communities. The ability to utilize these resources effectively will give a phytoplankton species a competitive advantage over other members of the community and thus, contribute to its overall fitness. The first section of the chapter briefly reviews how the utilization of resources such as nutrients and light is described and how competitive ability for these resources is defined. This is followed by a discussion on the implications of the vertical heterogeneity in resource distribution: a vertical gradient in light, with irradiances decreasing exponentially with depth and an opposing gradient in nutrient concentration that increases with depth. Phytoplankton also often exhibit vertically heterogeneous distributions that can be both the cause and the consequence of the vertical heterogeneity in light and nutrients.” Elena Lichtman , “Resource Competition and the Ecological Success of Phytoplankton,” Evolution of Primary Producers in the Sea 2007, Pages 351-375 https://www.sciencedirect.com/science/article/pii/B9780123705181500175