DIVER-OPERATED PISTON CORER FOR NEARSHORE USE

A diver-operated piston corer suitable for collecting cores of >3 m le ngth from fine-grained nearshore sediment has been developed. The core r uses a platform that rests on the sediment surface supporting both t he operators and a derrick that maintains the piston at the sediment-w ater interface. The core is inserted into and recovered from the sedim ent manually. The technique offers several advantages: low cost, minim al disruption of the sediment-water interface, little compaction of th e sediment, the ability to collect longer length cores than is possibl e with gravity corers, and the ability to be deployed from relatively small boats. Dissolved ammonium and inorganic carbon data are presente d from a 3.3-m core collected by this technique from Tomales Bay, Cali fornia.