cyclic variation of environmental factors is a permanent feature of the estu- 

 arine environment. The organisms that have become adapted to this environment 

 must tolerate the extremes and may even require them. 



Typical of estuaries, the marine fauna and flora of the Sound dis- 

 play a greater density of individuals but fewer species than are found in the 

 open sea. The concentration of non-living particulate organic matter in the 

 Sound is generally greater than the concentration of living phytoplankton , thus 

 limiting light penetration as indicated earlier. The lack of sunlight may limit 

 algal growth below 30 feet, but surface growth is rapid because there is enough 

 tidal mixing to regenerate nutrients from the bottom waters. 



2.2 How productive is the ecosystem ? 



The basic or primary productivity of an ecological system is the 

 rate at which energy is stored by producer (photosynthetic) organisms in the 

 form of organic substances which can be used as food materials. Net production 

 is the rate of storage of the organic substances in plant tissues in excess 

 of respiration. Secondary production is the rate of use and storage of 

 the food materials already producedo Productivity is measured as a rate and 

 is generally expressed in milligrams or grams of carbon produced per square 

 meter per day (gm C/M^/day) . Productivity should not be confused with standing 

 crop which is the bioraass per unit area at any one time. Standing crop is 

 a common measure of plant and animal abundance, and in terms of marine pro- 

 ductivity, it is generally expressed as grams of carbon per square meter 

 (gm C/m2). 



In Long Island Sound, the mean rate of photosynthesis is estimated 

 at 1,300 mg C/M2/ciay (_2) • This input produces a net production rate of 530 mg 

 C/M /day at the primary level, dropping to ranges of 27 to 36 mg C/M^/day at 

 the herbivore (plant-eating) level and to 0=5 mg C/M2/day at the carnivore 

 (animal-eating) level. The standing crop in the Sound is estimated at 8 gm 

 C/m2 at the primary level, between I and 5 gm C/M^ at the herbivore level, and 

 only 0.2 gm C/M^ at the carnivore level. Table I shows how these figures com- 

 pare with other types of production. Neither lobster nor migratory pelagic 

 (near-surface oceanic) finfish are included in these approximations. 



Several key points can be made about productivity in the Sound: 



(I) At the primary trophic level (photosynthesis), the Sound is 

 highly productive. It compares favorably with the most productive of marine 

 areas, the salt marsho Primary productivity is related principally to changes 

 in light and temperature. Therefc-re, most primary production in the Sound 

 occurs in the upper 30 feet. About 200 species of phytoplankton have been 



2 



Selected technical terms are defined in Appendix 



