NASA	National Aeronautics and Space Administration (USA).
navigation	The act or practice of navigating.
neap tide	The tides produced when the gravitational pull of the Sun is in quadrature, i.e. at right angles to, with that of the Moon. These occur twice a month at about the times of the first and last quarters. In these situations the gravitational pull of the sun/ moon produces high/ low water or vice-versa, and as such the differences between high and low tides are unusually small, with both the high tide lower and the low tide higher than usual. The tidal height is about .375 that of maximum during neap tides.
nekton	Those actively-swimming pelagic organisms able to move independently of water currents; typically within the size range 20 mm-20 m, divided into three categories on the basis of body size: centimetre nekton, decimetre nekton, metre nekton.
NERC	Natural Environment Research Council (UK).
Neritic province	A pelagic division of the ocean, located above the continental shelf.
neural	Relating to the nervous system.
nitrite	A compound containing nitrogen bound to two oxygen atoms. Inhibits the uptake of oxygen by haemoglobin and is toxic to fish.
Nitrobacter	Aerobic bacteria capable of converting nitrite into nitrate by a process termed nitration.
nitrogen fixation	The conversion of gaseous nitrogen, usually by bacteria, into a form usable by plants.
Nitrosomonas	Aerobic bacteria capable of oxdising ammonia to nitrite in a two-step process.
no-man's land	1. Land between boundaries, esp. an unoccupied zone between opposing forces 2. An unowned or unclaimed piece of land.
NOAA	Abbreviation for National Oceanic and Atmospheric Administration, a U. S. Government agency including the National Ocean Survey, National Weather Service, Marine Fisheries and other related services.
non-biodegradable	Not capable of being decomposed by bacteria or other biological means.
nuclear waste	Waste deriving from a nuclear source.
nursery ground	In the wild, refers to the site occupied by juveniles between the larval and adult stages.
nutrient	A substance which provides nourishment; the term is often used to refer to dietary components.