The concentration of dissolved oxygen in the lagoon 

 waters of Caroline Atoll reached 1 15 to 126%, and the vertical 

 distribution of hydrochemical parameters were relatively 

 homogeneous. Salinity in lagoon waters was slightly higher 

 than in water sampled outside of the lagoon (ocean water); the 

 average values for lagoon and adjacent ocean water were 

 36.05 and 35.85 parts per thousand, respectively. Nutrient 

 concentrations were lower in lagoon water than in coastal 

 water: silicon and phosphorus were two times lower, nitrates 

 were one and one-half times lower. According to studies of 

 hydrooptical characteristics the lagoon waters do not differ 

 significantly from the ocean waters. 



The mean rate of biosedimentation of particulate organic 

 matter (POM) in the water column from to 100 m in the area 

 investigated in the tropical zone of the Pacific Ocean was found 

 to be 14.2 to 72.5 mg of dry matter/m'/day. In coastal waters 

 of the atoll this rate was 64.5 mg dry matter/mVday. The rate 

 of biosedimentation in the surface water was two times higher 

 than the rate at a depth of 100 m. 



The most probable number (MPN) of heterotrophic 

 saprophytic bacteria in the water inside and outside of the 

 Caroline Atoll lagoon was 1,000 to 10,000 cells/ml. The MPN 

 ofparaffin-oxidizing,benzo(a)pyrene-transforming,andPCB- 

 transforming bacteria in the water near the atoll was 10 to 

 1,000 cells/ml. In the water inside of the lagoon the MPN of 

 microorganisms of these groups was less: 3 to 10 cells/ml. This 

 information gives us the ability to characterize the atoll's water 

 as clean, without anthropogenic pollutants. 



The dominant pollutant in the atoll's ecosystem, in the 

 widely investigated range of chlorinated hydrocarbons, was 

 DDT and its metabolites (approaching 1 ng/1). Other substances 

 observed in the pollutant benzo(a)pyrene were more intensive 

 at Caroline Atoll than in the tropical zone of the ocean. In one 

 hour, the amount of benzo(a)pyrene destroyed approached 

 85%, and after three hours more than 95% of experimentally 

 added benzo(a)pyrene was destroyed. Ecotoxicity experiments 

 conducted in situ dealing with the influence of benzo(a)pyrene, 

 PCB's, copper, and cadmium on planktonic communities of 

 the atoll's waters showed higher vulnerability of planktonic 

 organisms to toxic metals and were relatively more resistant to 

 benzo(a)pyrene and PCB's in comparison with the northern 

 seas. 



The distinctive feature of the zooneuston of the Caroline 

 lagoon in comparison with the adjoining oceanic waters is the 

 presence of a neuritic complex of organisms (larval stages of 

 benthic animals and the early stages of Copepoda). The mean 

 number of organisms was 64 ind/m\ 26 less than in the coastal 

 waters of the atoll. Nevertheless, the zooneuston of the lagoon 

 play an important role in the formation of the coastal water 

 fauna. 



A unique Acropora-Tridacna reef, dividing the lagoon, 

 was discovered in the southern part of the atoll. Its length was 

 more than one kilometer and its width was 15 to 20 m. At 

 certain places along the reef, the Tridacna formed a dense 

 aggregation with numbers approaching 40 ind/m : . 



More than 42,000 m 2 of Pacific Ocean surface water were 

 sampled for plastic debris and macroscopic spherules. Plastics 

 were recovered at six of the 29 different stations sampled. 



At two of these stations, tar balls were also recovered. The 

 density of surface plastics in areas that had positive samples 

 ranged from 0.00782 to 0.19481 mg plastic/nr. Because 

 marine growth on the surface of plastics may alter the specific 

 gravity of floating debris, sampling was also done at the 

 thermocline to determine if plastic could be contaminating this 

 important subsurface stratum. None of the 5 1 ,600 m 3 of water 

 sampled at the thermocline at nine different stations contained 

 any plastics or anthropogenic materials. The surface water of 

 the Caroline Atoll lagoon was sampled at two locations using 

 a 102 neuston net. More than 21,500 nr of water sampled 

 showed no evidence of plastics or other debris. Extensive 

 sampling of surface and subsurface water was also done in the 

 South China Sea. Although a wide variety of anthropogenic 

 materials were recovered in surface tows, few plastic cylinders 

 (raw material) were found. One sample from the thermocline 

 contained plastic line, the most common form of plastic 

 recovered in this area. Another surface sample from the South 

 China Sea contained more than 1 64 tar balls greater than 4 mm 

 in diameter. 



Detailed data on the plants, seabirds, landbirds, mammals, 

 reptiles, and human disturbance were obtained from 39 islets at 

 Caroline Atoll. The flora consists of 19 species (one new to the 

 island) organized into 4 natural and 4 anthropogenic plant 

 communities; 92% of the islets are pristine. Eleven species of 

 seabirds breed (red-tailed tropicbird is a new record): the sooty 

 tern, with 189,000 breeding pairs, was the most abundant 

 species. The long-tailed cuckoo was recorded for the first time 

 in the Line Islands. 



At-sea observations of marine birds indicated high 

 densities near uninhabited islands and in known areas of high 

 productivity. Low densities were observed in areas of 

 low ocean productivity and in areas with high human 

 disturbance (Gilbert Islands, and the Bohol, Sulu, and South 

 China Seas). 



Beach surveys for anthropogenic debris were done on nine 

 islands of Caroline Atoll. Plastic and styrofoam objects 

 accounted for 75 to 80% of the total number of items observed; 

 however, glass bottles and fishing gear were significantly more 

 important with respect to volume and biomass of debris. 

 Observations were also made at sea to determine the amount of 

 floating debris. 



Samples were collected at Caroline Atoll and selected 

 ocean sampling stations for radiological analyses. These 

 analyses will compare natural versus anthropogenic 

 radioisotopes. Radioisotope concentrations at Caroline Atoll 

 will be compared to similar samples obtained in the Marshall 

 Islands that contain contamination from atmospheric nuclear 

 weapons testing 30 years ago. 



At the end of the joint expedition on board the Akademik 

 Korolev, there was an exchange of preliminary data. Future 

 exchanges of data and results of analyses will occur in a series 

 of three exchanges: 1. 1 March 1989; 2. 1 June 1989; and 

 3. 1 October 1989. 



Both sides note with satisfaction the friendly and 

 constructive atmosphere of the expedition's work and the 

 effectiveness of joint observations allowing for a variety of 

 oceanographic and ecological studies. 



