Time-series photographs of the sea floor were obtained from an instrumented tripod deployed in western Massachusetts Bay at LT-A (42° 22.6' N, 70° 47.0' W; nominal water depth of 32 m; fig. 1) from December 1989 through September 2005. The photographs provide time-series observations of physical changes of the sea floor, near-bottom water turbidity, and life on the sea floor. Several reports present these photographs in digital form (table 1). This report, U.S. Geological Survey Data Series 265, Version 2.0, contains the photographs obtained from December 1989 to October 1996, adding to (and replacing) Version 1 of Data Series 265 (Butman and others, 2007a) that contained photographs from 1989 through 1993. Data Series 266 (Butman and others, 2008b) contains photographs obtained from October 1996 through September 2005. The photographs are published in separate reports because the data files are too large for distribution on a single DVD. These reports present the photographs, originally collected on 35-mm film, in digital form to enable easy viewing and to provide a medium-resolution digital archive. The photographs, obtained every 4 or every 6 hours, are presented as individual photographs (in .png format) and as a movie (in .avi format).

The time-series photographs taken at LT-A were collected as part of a U.S. Geological Survey (USGS) study to understand the transport and fate of sediments and associated contaminants in Massachusetts Bay and Cape Cod Bay (Bothner and Butman, 2007). This long-term study was carried out by the USGS in partnership with the Massachusetts Water Resources Authority (MWRA) (http://www.mwra.state.ma.us/) and with logistical support from the U.S. Coast Guard (USCG). Long-term oceanographic observations help to identify the processes causing bottom sediment resuspension and transport and provide data for developing and testing numerical models. The observations document seasonal and interannual changes in currents, hydrography, suspended-matter concentration, and the importance of infrequent catastrophic events, such as major storms, in sediment resuspension and transport. LT-A is approximately 1 km south of the ocean outfall that began discharging treated sewage effluent from the Boston metropolitan area into Massachusetts Bay in September 2000. See Butman and others (2004d) for a description of the oceanographic measurements at LT-A, and Butman and others (2007c) and Warner and others (2008) for discussion of sediment transport in Massachusetts Bay.