hardbottoms to reproduce. 

 If there are strong nutri- 

 tional links, then protec- 

 tive zones may also be 

 required in the surround- 

 ing softbottom communi- 

 ties. 



Ambrose and Posey 

 are also studying the 

 organism development 

 near the areas with 

 groundwater seeps. Scott 

 Snyder is studying several 

 microscopic animals that 

 inhabit the substrate, 

 particularly foraminifera. 



The research team's 

 scientific instruments are 

 as simple as the sawed-off 

 tops of 55-gallon drums 

 modified to monitor flow 

 of groundwater seepage 

 and as sophisticated as the 

 battery-powered submers- 

 ible through which the 

 scientists investigate, 

 photograph, videotape and 

 collect rocks, sediments, 

 plants and animals. The 

 168-foot research 

 vessel Edwin-Link 

 is the launching pad 

 for the Florida- 

 based Johnson Sea- 

 Link submersible. 

 The team is 

 studying five 

 geologically 

 diverse sites within 

 Onslow Bay. The 

 field work began in 

 1991 and will continue through 1994 

 under currently funded projects. 



Riggs worked with both Scott and 

 Steve Snyder throughout the 1980s 

 on a National Science Foundation- 

 funded project to study the origins of 

 the continental margin and associated 

 phosphate sediment in Onslow Bay. 

 Sea Grant also funded part of that 

 project. It was then that the scientists 



Hardbottoms Project Team 



Another significant area of biological study is the benthic — 

 or ocean bottom — sand community in the periphery oj 

 hardbottoms. Hardbottom reefs were once thought 

 of as islands that sustained themselves, but it turns out that the 

 surrounding sand flats or u softbottom" areas may be critical 

 in sustaining the system's foraging fauna. 



first got an inkling of the high levels 

 of nutrients in groundwater leaking 

 from the Miocene-age rock bottom 

 and observed the spectacular reefs 

 they are now studying. 



From that research, the team 

 already had an extensive data set 

 from Onslow Bay that included 

 seismic profiles — or cross-sections 

 — of the rock layers below the 



seafloor and side-scan 

 sonar images, which when 

 pieced together provide a 

 graphic mosaic much like 

 an aerial photograph of the 

 ocean bottom. 



Steve Snyder is continu- 

 ing to work with those and 

 new data sets to map the 

 habitats on the seafloor, as 

 well as analyzing the 

 nutrient chemistry of the 

 water column and the seep 

 fluids. 



The fifth research site, 

 which will be studied this 

 summer, is in an Oligo- 

 cene-age area in the bay, 

 where lithology — or rock 

 formation — is completely 

 different from the previous 

 four study sites. It is a little 

 bit west of the Miocene-age 

 study sites, and it, too, 

 likely has groundwater 

 seeps. 



"The source of the 

 nutrients in the seep fluid is 

 unknown at this point," 

 says Steve Snyder. 

 "It could be coming 

 from fertilized 

 watersheds on the 

 adjacent coastal 

 plain. The dissolved 

 nutrients then flow 

 into the aquifer 

 system and percolate 

 to the surface 

 someplace on the 

 continental shelf. If 

 that's the case, then we should see 

 nutrient-enriched fluids in this Oligo- 

 cene area as well." 



If the fluids are actually coming 

 through the phosphate-rich units and 

 stripping out soluble nutrients that 

 were buried there 15 million years ago, 

 then Snyder says the team should see a 

 big difference between the fluid 

 character seeping out of the Miocene 



6 MARCH /APRIL 1993 



