4. Other Significant Factors in the Living Environment. 



The offshore environment is dynamic and ever-changing. Seasonally it is characterized 

 by stocks of migrating fish and numerous eggs and larvae of pelagic and bottom-dwelling 

 organisms. Thus, the picture gained as a result of a short-term study probably would not 

 typify the area. A study must consider the seasonal and cyclical year-to-year aspects. For 

 an accurate picture of the biota of an area, it is also important to use a wide range of 

 sampling gear designed for capture of the variety of types of life to be expected— both 

 mature and immature— and to quantify the results. 



A wide range of information concerning the life of a marine area can be obtained from 

 the National Oceanographic Data Center, or major marine laboratories, in the form of raw 

 data covering such characteristics of the environment as productivity and bottom biomass. 



Attempts to piece together all the parts— from primary productivity to final 

 consumption and the various ecosystem cycles— have been too few and are badly needed. 

 Such attempts could provide a better ecological picture, bring out the more elusive 

 interractions between the many components, and reveal the possible effects of man's 

 interference. Such attempts can provide practical, usable information on which to base 

 action, monitor effects, or evaluate impacts. Such syntheses that have been attempted have 

 been largely in estuaries or sheltered bays. Offshore ecological syntheses are lacking. 



The major purpose of this introduction to ecological continuity is to provide a sense of 

 flow or integration to the consideration of ecological effects caused by interference with 

 natural conditions. Thus, interference with worms could be as important as interference 

 with fish or clams or other organisms of direct importance to man through changing the 

 food-web flow. 



5. Ecological Impacts of Offshore Dredging. 



It must be recognized that the bottom provides homes for innumerable living organisms 

 that are parts of energy webs culminating (from man's viewpoint) in commercially usable 

 species. 



Anything that affects the bottom, will necessarily affect or have impact on the 

 ecological balance and ultimately man's use of coastal areas. 



Dredging involves disturbance and removal of parts of the bottom. This affects the 

 environment. What are the effects produced and how great are they? Several aspects should 

 be considered. 



a. Mechanical Disturbance. The most obvious effect on the offshore environment is 

 mechanical, due directly to removal of substrate and indirectly to redeposition of 

 suspended sediment and turbidity. Since a varied fauna depends on the substrate, removal 

 or disturbance of the bottom material will reduce the fauna. The effect on the total system 

 depends on the magnitude of the disturbance created. Factors to be considered include 

 (a) nature of the grounds— shifting or stable, (b) type of dredging operation, (c) extent of 

 dredging and amount of substrate removed, (d) temporal nature of the disturbance, and 

 (e) ability of disturbed biota to withstand or recover from the disturbance. 



These factors can be discussed separately to highlight needed research and indicate 

 certain restraints to be exercised in the interim. 



