570 



the American oyster, which is often called the most thoroughly studied 

 of all estuarine organisms, can starve in waters containing large popu- 

 lations of certain unicellular green algae which appear to be as suitable 

 for food as other green algae on which they thrive. There needs to be 

 more definitive work done on the actual sources of food used by various 

 estuarine organisms, particularly those of commercial importance, 

 as well as the specific kinds of food. We need to know how much of 

 the diet of the given species comes from a given source. Tliis is par- 

 ticularly true for the detritus feeders. We need to know how much 

 detritus eaten comes from salt marshes ; how much from fresh water 

 sources upriver; how much from submerged aquatic vegetation; and 

 how much from other sources. Better knowledge in this area is neces- 

 sary in order to make intelligent decisions about how much of a 

 given sort of habitat is necessary to "carry" a given level of resource. 

 A better understanding and more knowledge of carbon fixation by 

 plants in estuaries is necessary, for this is the basic source of all food 

 for all levels of animals in the estuary. 



The estuary as a nursery 



We need to identify what is in the estuarine environment that makes 

 it so suitable a nursery for larval and juvenile animals. This in turn 

 means identifying, among other things, individual steps in food webs. 

 Enough aspects should be investigated to allow us to make estimates of 

 energy turnover. We already know that ocean basins are nutrient 

 traps — places where energy is trapped and not returned to the cycle. 

 What is the role of estuaries in this "running down" process? Do 

 fine sediments act as traps for organic and inorganic particles which 

 are then used by bacteria, and what organisms might "graze" on the 

 bacteria ? 



An important link in the food webs of the estuaries is the plankton 

 serving as a food supply for higher, more predacious organisms. These 

 higher predators are in the estuary as permanent residents, as migrants 

 coming in to feed, or as organisms that may use the estuary as a 

 migratory path going upstream or downstream, during which time 

 they might be feeding. One often hears of the conservation efforts di- 

 rected toward such major sport fish as the salmon, but little emphasis 

 is placed on the conservation of lower members of the food web which 

 are quite important, not only to forms such as salmon, but also to all 

 of the other forms utilizing this basic food stuff of the ocean as a 

 food supply. In brief, we must determine the degree to which estuarine 

 and offshore commercially and recreationally important fishes, and 

 their respective food chains, depend upon the estuary. 



Habitat requirements 



We must determine the fish and wildlife habitat areas necessary to 

 maintain adequate population levels for future uses in the estuaries 

 of food organisms, as well as the desirable species themselves. This 

 question of adequate habitat has proved to be a very difficult deter- 

 mination to make, in view of the lack of positive knowledge of the 

 quantitative requirements for marsh, as well as other estuarine environ- 

 ments as nursery and habitat areas for fish and wildlife and for other 

 purposes. Substantial research must be devoted to this question, mean- 

 while attempting to preserve marsh and other coastal regions to the 



