By Marine Sciences Department 

 V. S. Naval Oceanographic Office 



INTRODUCTION 



Discolored water is recognized as patches, streaks or very 

 large areas of more or less opaque brown, yellow, red and other 

 tints on the water, or under the surface. These areas fre- 

 quently resemble shoals. The purpose of this article and 

 accompanying chart is to demonstrate the geographical factors 

 in the distribution of these areas. We hope that this will be a 

 significant contribution to the mariners' problem of the clari- 

 fication and correction of erroneous notations of shoal water 

 on charts. 



Since about 1880 the Hydrographic Office has been receiving 

 discoloration records from many sources, chief among which 

 is the Merchant Marine. Reports in American and foreign 

 scientific publications and nautical journals have likewise 

 been used. The HYDROGRAPHIC BULLETIN, Hydrographic 

 Office PILOT CHARTS, and the MARINE OBSERVER of the 

 British Meteorological Office, have been most helpful. This 

 collection of observations forms the basis for the accompanying 

 chart and probably comprises the most complete record of the 

 distribution of discolored water. 



HISTORY 



The phenomenon of the discolored water has undoubtedly 

 been observed by voyagers and inhabitants of coastal areas 

 since before the beginning of the written record. One of the 

 earliest reports is found in the Bible, (seventh chapter of 

 Exodus, the twentieth and the twenty-first verses:) 



"And all of the waters that were in the river (The 



Nile) were turned to blood and the fish that was in the 



river died; and the river stank, and the Egyptians 



could not drink of the water of the river." 



Such reports may be found, also in the Iliad and the works of 



Tacitus and in the logs of a number of navigators of the 16th 



century and on. 



A few early records may be found with detailed description 

 of the discoloration and of the organisms which cause it. P"or 

 example, in l.')94. Sir Richard Hawkins, entering a cove in the 

 Straits of Magellan, observed a bright red discoloration of the 

 water. He stated, '*they sounded a cove some sixteen leagues 

 from the mouth of the straits, which after we called Crabby 

 Cove. It brooked its name well for two causes; the one for 

 that all the water was full of a small kind of red crabbes; the 

 other, for the crabbed mountains which overtopped it; a third, 

 we might add, for the crabbed entertainment it gave us." 

 Again, specifically mentioning discolored water, Simon 

 D'Cordex in 1598, reported "having passed the Rio de la 

 Plata, the sea appeared as red as blood, the water was full 

 of little red worms which when taken out jumped from the hand 

 like fleas. Some were of the opinion that with seasons of the 

 year the whales shook these worms from their bodies but of 

 this they have no certainty." The available records prior to 

 1800 attribute the discoloration in the sea to various factors 

 such as sea dust, submarine earthquakes, submarine sulphur 



springs, spawn of fish, etc. In 1729, during the voyage of the 

 ship St. George, Capt. William Dampier described an encounter 

 with discolored water off the coast of Peru as follows: 



"The 19th instance, our men all being at dinner and 

 our ship about ten leagues off shore, going with a 

 fine fresh gale of wind at East, we were suddenly 

 surprised with the change of the colour of the water, 

 which looked as red as blood to as great a distance 

 as we could see, which might be about seven or 

 eight leagues. At first we were mighty surprised; 

 but recollecting ourselves, we sounded, but had no 

 ground at one hundred and seventy fathoms. We then 

 drew some water up in buckets, and poured some in a 

 glass. It still continued to look very red, till about 

 a quarter of an hour after it had been in the glass; 

 when all of the red substance floated on the top, and 

 the water underneath was a clear as usual. The red 

 stuff which floated on top was of a slimy substance, 

 with little knobs, and we all concluded it could be 

 nothing but the spawn of fish.** 

 During the 19th century with the increase in shipping and the 

 publication of the results of scientific expeditions and private 

 investigations, considerable interest was aroused in the distri- 

 bution of and the explanation for discolored water. Sailing 

 directions requested that areas of discolored water be carefully 

 surveyed and sounded to eliminate the possibility of their being 

 recorded on the charts as shoal areas, and statements were 

 published in nautical journals to the effect that some of the 

 areas then reported as shoals were thought to be discolored 

 water. 



In recent years outbreaks of discolored water appearing off 

 the Florida and California coasts have been watched and 

 studied with increasing interest. Comparison of data from 

 the many known affected localities provides clues for the 

 study of these areas which may, in turn, contribute to the 

 discovery of the direct cause or the possibility of prediction 

 of the phenomenon. 



NOTE; In the Interest of this problem, the U. S. Navy Hydro- 

 graphic Office has issued a request to mariners to take soundings 

 in discolored water to insure correct diagnoses before reporting. 

 It has also requested reports on observations of discolored water 

 as a check on present shoal notations, 



CAUSES 



The causes of the normal color of the sea are physical. The 

 characteristic indigo of the open ocean can be explained by the 

 scattering of the light as it reflects from the water. Coastal 

 waters are generally greener, often with shades of brown or 

 yellow. These colors can be traced to the pigments in the 

 tiny plants and animals that inhabit the coastal waters, to the 

 color of the bottom sands and muds where the water is shallow, 

 and to the erosion products washed from the land by rivers and 

 rainfall. Different water masses, when they meet, as when bay 



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