R-/ 



RAPIDS 



Areas of a stream where velocity of current 

 is great enough to keep the bottom clear of 

 all loose materials, thus providing a firm 

 substrate . The surface of the water is 

 disrupted by turbulent currents. This area 

 is occupied largely by specialized benthic 

 or periphytic organisms that can firmly attach 

 or cling to a firm substrate . (See Pools , 

 Riffles) 



RED TIDE 



A visible red-to-orange coloration of an 

 area of the sea caused by the presence of a 

 bloom of certain plankton . These blooms are 

 often the cause of major fish kills. 



REDD 



A type of fish spawning area associated with 

 flowing water and clean gravel. Fishes that 

 utilize this type of spawning area include 

 trout, salmon, some minnows, etc. 



REDUCERS 

 (Decomposers) 



Those organisms, usually bacteria or fungi, 

 that break down complex organic material into 

 simpler compounds. (See Producers , Consumers) 



REEF 



A ridge of rocks, sand, soil or coral projecting 

 from the bottom to or near the surface of the 

 wat er . 



RESPIRATION 



The complex series of chemical and physical 

 reactions in all living organisms by which 

 the energy and nutrients in foods is made 

 available for use. Oxygen is used and carbon 

 dioxide released during this process. (See 

 Metabolism) 



