Page 229 - NS-2 Textbook

life in the Seas

So far in this unit we have talked about some physical, Iieved to contain a large percentage of the world's total
geological, and chemical aspects of oceanography. There protein supply.
is a fourth major scientific area: biology. Mari11e biologt) Upwelling, El Nino, a11d La Nina. Upwelli11g is the
deals with the living, or organic, content of the sea-its movement of deeper layers of water toward the surface.
plants and animals. This happens when prevailing winds along a shore cause
There are many separate areas of study within mod- movement of upper water layers away from the coast.
ern marine biology, and we cmmot explore them all in The Coriolis force is also a factor in this process. The re-
this text. One important field is biological oceanogra- sultant vertical circulation from great depths brings de-
phy, or marine ecologt). This field is concerned with cayed materials high in nitrogen and phosphates to the
marine organisms and their environment. It is directly surface. Upwelling occurs near the steepest gradient of
related to (1) human use of the sea for food and the continental slope.
employment, and (2) the effect of marine life on naval The most remarkable upwelling occurs along the Pe-
operations. This latter includes how marine organisms ruvian coast behveen the shoreline and the northward-
affect ships, installations, and equipment; the ability flowing Humboldt Current. The nuh'ients and minerals
of people to live and work on and under the sea; the nourish plankton, which, in turn, attract great numbers
effectiveness of sonar equipment; and many other im- of fishes, large and small, to the area. Great flocks of
portant things. seabirds feed on these fish, and the islands on which the
birds nest are covered with tons of their droppings,
called gua11o. Over 330,000 tons of guano are "mined"
PLANKTON, START OF THE LIFE CYCLE
annually for high-grade fertilizer. Fishermen catch up to
Pla11kton, both plant and animal, are those billions of tiny 100,000 tons of anchovies and sardines and the larger fish
floating organisms that wander with the ocean currents that feed on them each year.
or drift in the uppermost layers of the sea. The plankton Every now and then, for reasons not yet fully under-
provides the II ocean pasture" for the smallest animals stood but probably related to reduced trade winds, the
and fish. Materials in suspension in the sea, including de- Hlllnboldt Current meanders from its normal course or
cayed plant and animal life, provide the nutrients plank- actually disappears, allowing warmer currents to come
ton need. along the coast and make the surface layers of water
Phytopla1lkto1l are microscopic marine plants that warmer than usual. This stops upwelling, and without
start the food chain, an ecological system in which al- the life-supporting nutrients, fish begin to die. Addition-
most every form of life becomes the food for another, ally, millions of sea birds may die in such famines. The
usually highe!; form of life. Next are the zoopla11kto1l, tiny hydrogen sulfide from the decaying bodies of both fish
animals and larvae of larger sea life. Finally there is a and birds is so thick that ships' hulls are turned black.
whole range of larger fish and sea animals, which ex- This occurrence is locally called the Callao Pai11ter, nruned
tends from fishes and crabs to the giant blue whale, the after the nearby port of Callao, Peru. The phenomenon
world's largest mammal. that causes upwelling to stop is called El Nino ("little
To show how small plankton are-and to see if boy" in Spanish). TIle El Nino effect results in unusually
enough could be gathered for a meal-explorer TIlOr warm surface waters in the Equatorial Pacific. For ma-
Heyerdahi dragged a plankton net behind his balsawood rine life, it is one of the most destructive oceanographic
raft, K011-Tiki, for many hours across the southern Pacific conditions in the world. It can also cause dramatic cli-
in 1947. He managed to gather a small amount of edible matic changes in Central and North America and else-
plankton, which he made into a sort of fish paste. He where.
found it to be very salty. Studies have now proved that TIle most recent and severe episodes of the El Nino
this material is almost pure protein. In fact, the sea is be- effect occmred in the winter of 1997-98. During this time

224