This size range is composed mostly of eukaryotes, organisms whose cells contain complex membrane-bound structures ("organelles"), including the cell's nucleus and chloroplasts. Open ocean heterotrophs include bacteria as well as more complex single- and multi-celled "zooplankton" (floating animals), "nekton" (swimming organisms, including fish and marine mammals), and the "benthos" (the seafloor community of organisms). 2. Click here or below to download hands-on marine science activities for kids. 3. 1988). However, the typical dominance of diatoms in Si-bearing waters, and the tendency of diatom-associated organic matter to sink out of the surface ocean, make Si availability a major factor in the broader ecology and biogeochemistry of surface waters. Wind or another source of energy is required to drive mixing across the pycnocline, and so the transport of water with its dissolved chemicals between the sunlit surface and the dark interior is sluggish. We have already protected nearly 4 million square miles of ocean and innumerable sea life -but there is still more to be done. Most of the world is covered in ocean. Connect and share knowledge within a single location that is structured and easy to search. Along the coasts, the seafloor is shallow, and sunlight can sometimes penetrate all the way through the water column to the bottom, thus enabling bottom-dwelling ("benthic") organisms to photosynthesize. This very efficient recycling elevates NPP relative to NEP, yielding a low NEP:NPP ratio (~0.050.3) in nutrient-poor systems (Figure 3a). Furthermore, sinking organic matter isintercepted by the seabed, where it supports thriving benthic faunal communities, in the process being recycled back to dissolved nutrients that are then immediately available for primary production. Generally speaking, this zone reaches from the sea surface down to approximately 200 m (650 feet). Not enough water so very little photosynthesis. Thus, satellite chlorophyll observations tend to over-accentuate the productivity differences between nutrient-bearing and -depleted regions. The microzooplankton that graze these small cells do so effectively, preventing phytoplankton from sinking directly. It would be a different story if we were to regard algae as potentially suitable for mass harvesting, so that their ability to grow like wildfire in the presence of fertilizer runoffs from the land was regarded as "productivity" rather than as a profound nuisance. 1991, Buesseler 1998) (Figure 3). Sunlight is the ultimate energy source directly or indirectly for almost all life on Earth, including in the deep ocean. While the new nutrient supply and export production are ultimately linked by mass balance, there may be imbalances on small scales of space and time, allowing for brief accumulations of biomass. so if we define "productivity" as "increase in dry weight of algae" then the productivity is zero. On the whole, only a tiny fraction (typically much less than 1%) of the organic carbon from NPP in the euphotic zone survives to be buried in deep sea sediments. Warm water is more buoyant than cold, which causes the upper sunlit layer to float on the denser deep ocean, with the transition between the two known as the "pycnocline" (for "density gradient") or "thermocline" (the vertical temperature gradient that drives density stratification across most of the ocean, Figure 2). This connection is evident in multiple places. The most broadly accepted paradigm for the controls on surface nutrient recycling efficiency. Working with a small group, imagine you represent the interests of one the following: consumers, workers, clothing makers, or environmentalists. 2009) that we will not address further. Humans have only explored 5 percent of the worlds oceans. It 's because the ocean 's volume ( mostly open space ) in comparison to the amount of producers is massive . Why does the open ocean have a low NPP? So the NET amount of O2 released by the oceans is something close to zero. Initially, the cyanobacteria were identified largely with colonial forms such as Trichodesmium that play the critical role of "fixing" nitrogen (see below). Thus, most open ocean biomass, including phytoplankton, zooplankton, and nekton, is found within ~200 m of the ocean surface. The dry weight of the algae at the end of the of the process is the same as at the beginning. A big problem in the oceans is availability of nutrients; these tend to deposit or react with water or other chemical compounds, even though the marine photosynthetic organisms are essentially found on the surface, where, of course, light is present. Organisms in the bathypelagic live in complete darkness, 24 hours per day. Because of the density difference between surface water and the deep sea across most of the ocean, ocean circulation can only very slowly reintroduce dissolved nutrients to the euphotic zone. But

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