dissolved or aggregated organic matter, liberated by the coral and 



algoflora, detritus, bacteria, algae, protozoa which is washed out into 



the water from the coral sand, and periphyton of the shallow zones of 

 the reef by the action of the waves and currents. 



The wet biomass of phytoplankton over the reef averages 20-100 

 mg/m'^; the production averages 10-30 mg C/m'^ (Sorokin, 1971c, 1973b). 

 It is significantly higher on reefs located in eutrophic regions, for 

 example. New Guinea or Puerto Rico (Glynn, 1973). The lowest biomass 

 and production of phytoplankton are reported for reefs located in 

 oligotrophic waters of the ocean (Table 8). The seasonal nature of 

 phytoplankton development is of great significance. During periods of 

 maximum development, the biomass and production of phytoplankton may 

 increase by an order of magnitude in comparison to the mean annual 

 values (Sournia, 1969). Periods of massive appearance and precipitation 

 of benthos larvae in the tropics coincided with the period of 

 phytoplankton maximum (Fig. 5). 



The phytoplankton is usually dominated by diatoms (Sournia, 1969; 

 Glynn, 1973). According to our observations, the important components 

 of the phytoplankton in the water above reefs Are the dynoflagellates of 

 the genus Porocentrum , as well as filamentous blue-green algae, washed 

 out from the periphyton and phytobenthos by the surf. If the blue-green 

 alga, Trichodesmium rubrum is developing in the surrounding waters of 

 the ocean, it appears in a significant quantity in the water above the 

 reef, as well, at times representing as much as 90% of the total 

 phytoplankton biomass. 



In spite of the intensive water exchange, the distribution of 

 phytoplankton and its production above the reef are usually not 

 uniform: The maximum values are observed above the outer slope of the 

 reef (Br-FR zones), the minimum values in the lagoon. This may be 

 either a result of the consumption of the phytoplankton by the reef 

 fauna (Emery, 1968; Glynn, 1973) or a result of a more intensive 

 breeding of phytoplankton over the outer slope of the reef which is 

 enriched by the runoff of nutrients and biologically active substances 

 from the reef flat. 



The primary component of the plankton in the water over the reef in 

 most cases is not phytoplankton, but rather bacterioplankton. The 

 biomass of phytoplankton over reefs usually does not exceed the limits 

 characteristic for oligotrophic waters the biomass of bacterioplankton 

 corresponds to the level of mesotrophic waters, and sometimes of 

 eutrophic waters of the ocean. The biomass of bacteria exceeds the 

 biomass of phytoplankton by an average of 5-10 times, production--by 

 1.5-2 times. The total population of bacteria in the water above the 

 reef averages 0.5-1.5*10^ cl/ml, their biomass--20-80 mg C/m-^ (0.2-0.8 

 g/m^ wet mass). In certain cases, the population of bacteria may reach 

 3 million cl/ml with a biomass of over 130 mg C/m'^. These magnitudes 

 were noted in New Guinea (organic-rich terrigenous runoff) and in the 

 lagoon of the polluted reef of Kaneohe Bay, Oahu, Hawaii (Sorokin, 

 1973e). ^bst of the bacterioplankton consisted of rod-shaped forms. 

 About 30% of the cells were joined into aggregates--accumulations 5-15 

 wn in diameter. Their formation is a result of the property of a part 



180 



