22 



introduce artifacts that may appear to be small areas of depth increase or decrease. As a 

 result, the lateral extent of a disposal mound or apron is often below the threshold of the 

 bathymetric data products. Other monitoring techniques are often employed to define the 

 thinner margins of the disposal mound (i.e., sediment-profile photography). 



2.2 REMOTS® Sediment Profile Photography 



REMOTS® sediment-profile photography is a benthic sampling technique used to 

 detect and map the distribution of thin (<20 cm) dredged material layers, map benthic 

 disturbance gradients, and monitor the process of benthic recolonization over the disposal 

 mound. This is a reconnaissance survey technique used for rapid collection, interpretation 

 and mapping of data on physical and biological seafloor characteristics. REMOTS® 

 utilizes a Benthos Model 373 1 Sediment-Profile Camera, designed to obtain undisturbed, 

 vertical cross-section photographs (in situ profiles) of the upper 15 to 20 cm of the 

 seafloor, for analysis and interpretation. 



The REMOTS® hardware consists of a wedge-shaped optical prism having a 

 standard 35mm-camera mounted horizontally above in a watertight housing (Figure 2-3). 

 The prism resembles an inverted periscope, with a clear Plexiglas window measuring 

 15 cm wide and 20 cm high and an internal mirror mounted at a 45° angle to reflect the 

 image in the window up to the camera. Light is provided by an internal strobe that resides 

 within the optical prism. In order to equalize pressure and reduce refraction, the prism is 

 filled with distilled water. The prism sits inside a stainless steel external frame, and the 

 entire assembly is lowered to the seafloor using a standard winch mounted aboard the 

 survey vessel. Upon contact with the bottom, the prism descends slowly into the seafloor, 

 cutting a vertical cross-section profile of the upper 15 to 20 cm of sediment, and a 

 photograph is taken of the sediment in contact with the window. The resulting 35-mm 

 slides (images) showing relatively undisturbed sediment profiles are then analyzed for a 

 standard suite of measured parameters (Rhoads and Germano 1982; 1986). 



Computer-aided analysis of each REMOTS® sediment profile image yielded a series 

 of measurements. The standard measured parameters include sediment grain size major 

 mode, camera prism penetration depth (an indirect measure of sediment bearing 

 capacity /density), small-scale surface boundary roughness, depth of the apparent redox 

 potential discontinuity (RPD), infaunal successional stage, and Organism-Sediment Index 

 (a summary parameter reflecting the overall benthic habitat quality). A detailed 

 description of REMOTS® photograph acquisition and interpretive rationale is given in 

 DAMOS Contribution No. 60 (Parker and Revelas 1989), as well as in Rhoads and 

 Germano (1982; 1986). The following paragraphs provide brief descriptions of the 

 interpretive framework and methods used for the various measurement parameters. 



Monitoring Cruise at the New London Disposal Site, 1992 - 1998 



