Why Study Benthic 

 Communities? 



Most people don't have any direct 

 contact with the abundant but small 

 organisms that live in marine bottom 

 sediments. Therefore, it may be diffi- 

 cult to appreciate the importance of 

 benthic communities even though we 

 are all familiar with some of the larger 

 bottom-dwellers such as the crabs, 

 lobsters, clams and shrimp that are 

 commonly enjoyed seafood items. But 

 close study shows that ecosystems, in- 

 cluding those of the benthos, are com- 

 plex. The existence of one component 

 of this system, such as crabs, depends 

 on the normal functioning of all 

 ecosystem components from bacteria 

 to top predators such as striped bass. 

 Many delicately balanced variables 

 create an intricate marine ecosystem in 

 which each component has some in- 

 fluence on all the others. 



And so benthic communities are closely 

 studied because the stationary lifestyle of 

 such organisms makes them good pollu- 

 tion indicators, and because benthic 

 communities play an essential role in 

 the functioning of the ocean ecosystem. 



Importance of 

 Benthic Communities 



Food Web Functions - One phenomenon ob- 

 served in ecosystems is the transfer of energy 

 up the food web, from plants to plant eaters or 

 herbivores, to predators. Benthic organisms 

 have a critical role in the transfer of energy to 

 fish species, especially juveniles, the young of 

 the species, and bottom feeding fish. Some 

 benthic organisms concentrate food and energy 

 from the water column by filtering out minute 

 plants and animals. Others ingest sediment, in 

 order to digest out the myriad microorganisms 

 that in turn survive by breaking down dead plant 

 and animal matter. Thus the benthic community 

 might be thought of as an array of energy 

 packets distributed at different sediment depths 

 and available in different sizes and types. These 

 energy packets may be grazed upon by a variety 

 of finfish and shellfish, many of which are com- 

 mercially important species. 



Provision of Habitat - A structured or shelter- 

 ing habitat is needed by many marine animals. 

 The plants found in marshes and grass beds, 

 which are associated with near-shore benthic 

 communities, provide the habitat that helps 

 make these areas so highly productive. These 

 plants supply protected spawning areas, hiding 

 places for small fish, and points of attachment 

 for a host of sessile or attached marine species 

 that are low in the food web, such as barnacles. 

 This promotes the use of marshes and grass 

 beds as nursery areas for many marine animals, 

 including off-shore and commercially important 

 species. 



Lack of Motility - Many benthic organisms 

 cannot relocate. Once the free-swimming larvae 

 settle out of the water column and change into 

 adults, they stay in the same location for the re- 

 mainder of their existence. Although some ben- 

 thic organisms are capable of relocating, for 

 most it is a slow, poorly directed process, not at 

 all comparable to the motility enjoyed by finfish. 



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