The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the world ocean is conventionally divided. Separate names are used to identify five different areas of the ocean: Pacific (the largest), Atlantic, Indian, Southern (Antarctic), and Arctic (the smallest). Seawater covers approximately 361,000,000 km2 (139,000,000 sq mi) of the planet. The ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth. Acting as a huge heat reservoir, the ocean influences climate and weather patterns, the carbon cycle, and the water cycle. Oceanographers divide the ocean into different vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column from surface to ocean floor throughout the open ocean. The water column is further categorized in other zones depending on depth and on how much light is present. The photic zone includes water from the surface to a depth...

Over the past several decades marine conservation policy has supported the implementation of protected areas in ocean and coastal environments to restrict some elements of human use for ecological benefits. The appropriate extent of protection and the allowable uses are often the subject of public debate about marine protected area policy. Local community dynamics around marine protected area designation and management have been the subject of much ocean and coastal management social science research. However, broader public opinions and attitudes about marine protected areas are not well understood and are critical for managers seeking to maintain their public trust obligations in environmental management. This paper provides a model for understanding the attitudes and beliefs that foster public support for or opposition to marine protections. We explored the relationships between awareness, attitudes and beliefs towards coastal and marine resource issues and uses, and demographics among a sample of Oregon, USA residents (n = 459), and tested their influence on support for expanding Oregon's recently established marine reserves. We found that Oregonians have relatively low familiarity with Oregon's marine reserve system, but that familiarity did not influence public support for Oregon's marine reserves. Instead public support was lower among coastal residents and those with positive attitudes towards commercial fisheries, and higher for those concerned with the ecological integrity of Oregon's ocean and supportive of some limits to human uses of the ocean. Our findings highlight the need for managers to engage both coastal communities and the general public to make a case for the value of marine protected areas in safeguarding the public trust.

The Ocean Twilight Zone project combines exacting science, innovative technology, and broad engagement to turn knowledge into actions that improve understanding of our planet and how to live sustainably on it.

A key question when trying to understand the global carbon cycle is whether the oceans are net sources or sinks of carbon. This will depend on the production of organic matter relative to the decomposition due to biological respiration. Estimates of respiration are available for the top layers, the mesopelagic layer, and the abyssal waters and sediments of various ocean regions. Although the total open ocean respiration is uncertain, it is probably substantially greater than most current estimates of particulate organic matter production. Nevertheless, whether the biota act as a net source or sink of carbon remains an open question.

The hypothesis that one or more biodiversity drops in the Phanerozoic eon, evident in the geological record, might have been caused by the most powerful kind of stellar explosion so far, known Gamma Ray Bursts (GRBs), has been discussed in several works. These stellar explosions could have left an imprint in the biological evolution on Earth and in other habitable planets. In this work, we calculate the short term lethality that a GRB would produce in the aquatic primary producers on Earth. This effect on life occurs because of ultraviolet (UV) retransmission in the atmosphere of a fraction of the gamma energy, resulting in an intense UV flash capable of penetrating tens of meters into the water column in the ocean. We focus on the action of the UV flash on phytoplankton as they are the main contributors to global aquatic primary productivity. Our results suggest that the UV flash could cause a significant reduction of phytoplankton biomass in the upper mixed layer of the world's oceans.

The hypothesis that one or more biodiversity drops in the Phanerozoic eon, evident in the geological record, might have been caused by the most powerful kind of stellar explosion so far known Gamma Ray Bursts (GRB) has been discussed in several works. These stellar explosions could have left an imprint in the biological evolution on Earth and in other habitable planets. In this work we calculate the short-term lethality that a GRB would produce in the aquatic primary producers on Earth. This effect on life appears because of ultraviolet (UV) retransmission in the atmosphere of a fraction of the gamma energy, resulting in an intense UV flash capable of penetrating tens of meters in the water column in the ocean. We focus on the action of the UV flash on phytoplankton, as they are the main contributors to global aquatic primary productivity. Our results suggest that the UV flash could cause a significant reduction of phytoplankton biomass in the upper mixed layer of the World Ocean.

ocean life

Current understanding of the last stages of planetary accretion suggests that mass and energy accumulation are dominated by a few large impacts. An important thermal consequence of such impacts is melting and formation of a large melt pond. If the planet's isostatic adjustment time scale is short compared to the magma pond's cooling time scale, the melt may be extruded onto the surface and form a magma ocean of approximately uniform depth. Although a giant impact striking at 10-15 km s-1 deposits enough energy to melt the entire planet, the distribution of that energy is important in determining the thermal outcome of the collision. We examine the thermal effects of giant impacts by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, we examine the effects of the planet's initial temperature on the generated melt volume. The Hugoniot curve plotted in pressure-entropy space is used to determine the shock pressure required to completely melt the material. For room temperature dunite, this pressure is about 150 GPa and the partial melt region is narrow. For dunite initially at the solidus temperature, this pressure is about 115 GPa. The partial melt region extends throughout the planet. Once the melting pressure is known, an impact melting model based on the second Hugoniot equation, the linear shock-particle velocity relationship, and the empirical particle velocity-distance relationship is used to estimate the radial distance melting occurred from the impact site. Once the distance is found, the melt region's geometry determines the associated melt volume. Partial melt volume is also estimated. The melt fraction that is not excavated during crater formation is estimated and magma ocean depths resulting from both excavated and retained melt are calculated. The model is also used to estimate the fraction of a planet melted by the initial shock wave. Nominal conditions of the Moon-forming giant impact (projectile/planet mass=0.14, impact speed=15 km s-1) generate melting of 30-65% of the planet depending on its initial temperature. Whole planet melting requires projectile/planet mass ratios of <0.4 for a 15 km s-1 impact if the planet was near its solidus before the impact. Isostatic relaxation may generate a significant volume of additional melting.