shifting beach sands constantly respond to changes in wind, waves, and 

 currents. Cycles of erosion and deposition are essential features of 

 the sand beach environment. Low wave energy permits the accumulation of 

 fine sediments which fill the interstitial spaces. This cuts off the 

 supply of oxygen and leads to the promotion of a sulfide layer character- 

 ized by a black color. A high-energy beach, however, is permeable and its 

 pore spaces are frequently in contact with the air or oxygenated water. 



Another characteristic of the high-energy beach is its slope. High- 

 energy beaches tend to have slopes of about 2 to 11 percent; low-energy 

 beaches have slopes of less than 1 percent. Distinguishing character- 

 istics of both types of beaches, as described by Cox (1976), are com- 

 pared in Table 1. 



Table 1. Characteristics of high-energy and low-energy beaches 

 (modified from Cox, 1976). 



High-energy beach 



Steep, about 2 to 11 percent 

 slope 



Interstitial water, well 

 oxygenated 



Low proportion of particles 

 <2S0 um; median diameter (Mj) 

 <250 pm 



Well -developed interstitial 

 community; high diversity 



Low carbon content: 

 ug C/g sediment 



70 to 400 



High turnover rate with no 

 accumulation of carbon 



Low-energy beach 



Less steep, usually <1 percent 

 slope 



Pronounced On gradient; sulfide 

 layer 



High proportion of particles 

 <250 pm; M^ <250um 



Small or nonexistent interstitial 

 community; low diversity 



High carbon content: 220 to 2,250 

 yg C/g sediment 



Lower turnover rate with carbon 

 accumulation 



Open-coast sand beaches support a faunal community that is low in 

 biomass. Diversity of organisms is high; organism density is low. 

 Animals living on and in the bottom must contend with many adverse 

 environmental factors. Sand is inhospitable to many organisms because 

 of a movable substratum which offers no "footholds" for animals such as 

 anemones, limpets, or barnacles. Strong wave action also discourages 

 animals which cannot maintain their position. There are more endofaunal 

 than epifaunal species on sandy bottoms because their burrowing protects 

 them. 



III. PLANNING FIELD TRIPS 



1. Prerequisite Information . 



Data oh the local geology, weather and sea conditions, and manmade 

 features of the high-energy sand beach to be sampled must be gathered. 

 Grain-size analysis is generally available from coastal engineering 



