PARASITE 



m 



An organism that lives on or in a host organism 

 during all or part of its existence. Nourishment 

 is obtained at the expense of the host. 



PATHOGEN 

 PELAGIC ZONE 



An organism or virus that causes a disease. 



The open sea, away from the shore. Comparable 

 with the limnetic zone of lakes . 



PERIODIC DRIFT 



Drift of bottom organisms at regular or 

 predictable intervals such as diurnal , 

 seasonal, etc. (See Drift Organisms . 

 Catastrophic Drift . Incidental Drift) 



PERIPHYTON 

 (Aufwuchs) 



Attached microscopic organisms growing on 

 the bottom, or other submersed substrates , 

 in a waterway. 



PESTICIDE 



Any chemical preparation used to kill pests . 

 Includes insecticides, herbicides, fungicides, 

 etc. 



PESTS 



(Nuisance Organisms) 



PHOTOSYNTHESIS 



The metabolic process by which simple sugars 

 are manufactured from carbon dioxide and 

 water by plant cells using light as an 

 energy source. (See Chlorophyll) 



PHOTIC ZONE 



( Euphotic Zone) 



