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Open ocean areas with no oxygen have grown more than 1.7 million square miles in the last 50 years, and coastal waters have seen a tenfold increase in low-oxygen areas in the same time. [47] Measurement of dissolved oxygen in coastal and open ocean waters for the past 50 years has revealed a marked decline in oxygen content.
Decline of oxygen saturation to anoxia, measured during the night in Kiel Fjord, Germany. Depth = 5 m. Oxygen depletion can result from a number of natural factors, but is most often a concern as a consequence of pollution and eutrophication in which plant nutrients enter a river, lake, or ocean, and phytoplankton blooms are
In medicine, oxygen saturation refers to oxygenation, or when oxygen molecules (O 2) enter the tissues of the body. In this case blood is oxygenated in the lungs, where oxygen molecules travel from the air into the blood. Oxygen saturation ((O 2) sats) measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen ...
This series of reactions governs the pH levels in the ocean and also dictates the saturation state of seawater, indicating how saturated or unsaturated the seawater is with carbonate ions. Consequently, the saturation state significantly influences the balance between the dissolution and calcification processes in marine biogenic calcifiers.
Data from the World Ocean Atlas 2009. In freshwater or marine systems apparent oxygen utilization (AOU) is the difference between oxygen gas solubility (i.e. the concentration at saturation) and the measured oxygen concentration in water with the same physical and chemical properties. [1]
The UN Environment Programme reported 146 dead zones in 2004 in the world's oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometer (0.4 mi 2), but the largest dead zone covered 70,000 square kilometers (27,000 mi 2). A 2008 study counted 405 dead zones worldwide. [4] [2]
The lower the aragonite saturation level, the more difficult it is for the organisms to build and maintain their skeletons and shells. The map below shows changes in the aragonite saturation level of ocean surface waters between 1880 and 2012. [107] To pick one example, pteropods are a group of widely distributed swimming sea snails.
[1] [4] It is thought that the earliest organisms originated in the ancient oceans, long before any forms of life appeared on land. Ocean biology is dominated by organisms that are fundamentally different from organisms on land and the time scales of the ocean are much different than the atmosphere (whilst the atmosphere exchanges globally ...