Kelp.

Phytoplankton and Sargasso

1) "The pelagic zone is also known as the open-ocean zone. The pelagic zone is further divided into sections creating a number of sub-zones based on their different ecological characteristics. These characteristics are roughly a function of depth. - Epipelagic [photic zone or euphotic zone] From the surface (MSL) down to around 200m (656 ft). The illuminated surface zone where there is enough light for photosynthesis. Due to this, plants and animals are largely concentrated in this zone. Here one will typically encounter fish such as tuna and numerous amounts of sharks,as well as colorful dolphinfish & jellies. - Mesopelagic (the twilight zone) From 200m down to around 1,000m (3,280 ft). Although some light penetrates this deep, it is insufficient for photosynthesis. The name stems from Greek μέσον, middle. Animals such as swordfish, squids, wolffish, a few species of cuttlefish, and other semi-deepsea creatures live here. - Bathypelagic From 1,000m down to around 4,000m (13,123 ft). By this depth the ocean is almost entirely dark (with only the occasional bioluminescent organism, such as lanternfish). There are no living plants, and most animals survive by consuming the snow of detritus falling from the zones above, or (like the marine hatchetfish) by preying upon others. Giant squid (as well as smaller squids & dumbo octopuses ) live at this depth, and here they are hunted by deep-diving sperm whales. From Greek βαθύς (bathys), deep. - Abyssopelagic From 4,000m down to above the ocean floor. No light whatsoever penetrates to this depth, and most creatures are blind and colourless. The name is derived from the Greek άβυσσος (ábyssos), abyss, meaning bottomless (a holdover from the times when the deep ocean was believed to be bottomless). - Hadopelagic The deep water in ocean trenches. The name is derived from the Greek Άιδης (HaidÄ“s), Hades, the classical Greek underworld. This zone is mostly unknown and very few species are known to live here (in the open areas). However, many organisms live in hydrothermal vents in this and other zones. Some define the hadopelagic as waters below 6,000m (19,685 ft), whether in a trench or not. The bathypelagic, abyssopelagic, and hadopelagic zones are very similar in character, and some marine biologists elide them into a single zone or consider the latter two to be the same." Source and further information: http://en.wikipedia.org/wiki/Pelagic_zone 2) "Benthos are the organisms which live on, in, or near the seabed, also known as the benthic zone.[1] Although the term derived from the Greek for "depths of the sea", the term is also used in freshwater biology to refer to organisms at the bottoms of freshwater bodies of water, such as lakes, rivers, and streams. Animals belonging to the benthos are sometimes referred to as zoobenthos, while plants are referred to as phyto-benthos." Source and further information: http://en.wikipedia.org/wiki/Benthos 3) "There are two different groups of open water dwellers: plankton (drifters) and nekton (swimmers). The swimmers include animals such as whales, sharks, swordfish, and tuna. Plankton, on the other hand, are something that will 1) drift or weakly swim and 2) are unable to swim against the currents. These “drifters” range in size from microscopic plants (diatoms) to gelatinous animals measuring three meters in diameter (jellies and siphonophores)." "Plankton can be either animals OR plants, and can exist in the open ocean, as well as abundantly in near shore waters, lakes, streams, rivers, and estuaries. Plant plankton are called phytoplankton and are generally smaller than the animals. It has been said that approximately 200,000 plant plankton can fit on the period at the end of a sentence." "They need both sunlight and nutrients for photosynthesis; therefore phytoplankton have adapted to living in the uppermost layers of the ocean, the photic zone, to receive optimal levels of sunlight. Nutrients needed for photosynthesis, such as nitrates and phosphates, are easily absorbed from the water, BUT these nutrients are present in fairly low concentrations in the open ocean. Consequently, there are usually lower concentrations of phytoplankton in the open ocean because of the low concentrations of available nutrients." Source and further information: http://www.cmiregistration.com/util/media.jxp?id=29573&org=261

Mostly plankton