The following figures are in PDF format. Figure 27 Figure 28A Figure 28B Figure 28C Figure 29 Figure 30 Figure 31

During the 4-month instrument deployments, the systems were frequently affected by biological and, occasionally, mechanical fouling. Different organisms of varying densities appeared on surfaces at different water depths (fig. 27). Biological fouling typically was heaviest on the near-surface instruments and lightest on the near-bottom instruments.

All surfaces of the tripod frames, current sensors, and some instrument cases were painted with antifouling paint (Pettit Marine Paint Trinidad Anti Fouling, Cuprous Oxide 65%, Inerts 35%, EPA regulation #60061-49). This strategy generally, but not always, minimized fouling over the 4-month deployment (fig. 28A, 28B, 28C). The current data files have been truncated when the data begin to be affected by fouling.

The optical windows of the cameras (fig. 29) and transmissometers (fig. 28B) were almost always affected by some biological growth after a 4-month deployment. Beginning in 1991, the windows of the transmissometers were surrounded by a porous plastic ring impregnated, using a vacuum technique, with Controlled Environmental Chemical Antifouling Protection (CECAP, manufactured by Oceanographic Industries, Miami, FL), which contains trialkyltin (Strahle and others, 1994). The toxin slowly leached into the water in front of the transmissometer window to retard the growth of barnacles. Between deployments, the ring was cleaned and a new application of CECAP was impregnated into the material. Although this protection discouraged macrofaunal growth and increased the length of time that "good" data were obtained (Strahle and others, 1994), accumulation of algal slime on the transmissometer windows continued to gradually block light transmission, resulting in a gradual upward drift of the beam-attenuation coefficient (for example, see the time-series plots of beam attenuation). The beam-attenuation data have not been corrected for biological fouling and should be used qualitatively. Statistics were not computed for the beam-attenuation observations.

The ports for all of the conductivity cells (on SEACATs, MicroCATs, and the bottom tripod systems) were fitted with hollow porous plastic tips impregnated with trialkyltin to reduce fouling (Oceanographic Industries). Salinities measured by the bottom tripod systems from 1989 to 1996 were erroneously low by as much as 1 psu by the end of the 4-month deployment. Salinities have not been corrected for these errors. The conductivity cells were apparently affected by a slow, gradual buildup of a biological film on the electrodes and also occasional sudden deposits of material (possibly sediments) inside the measurement volume of the conductivity cell. In June 1996 (mooring 470), pumps manufactured by Sea-Bird Electronics were added to the bottom tripod system to flush the conductivity cell prior to making a measurement, reducing the effect of deposits on the conductivity measurements. The conductivity cells mounted on the subsurface mooring were hypothesized to be less sensitive to the buildup of sediments because of the stronger currents and vibration of the mooring. Statistics of salinity at LT-A at 31 m do not include the observations obtained prior to 1996.

When recovered, mooring 407 was entangled with lobster gear (fig. 30). This recovery followed the December 1992 storm, the largest during the period 1990-2006 (Butman and others, 2008c), during which a large amount of lobster gear was lost; it is hypothesized that some of this drifting gear became entangled on the tripod. In general, the tripods remained unfouled by debris during the deployments.

The openings of the tube traps and the Anderson traps contained a honeycomb-like baffle (cells 0.5 cm in diameter, 7.6 cm long) composed of phenolic resin in order to reduce turbulence and prevent fish occupation. The larger time-series traps had a larger baffle with a 1 nylon mesh (1 cm cell diameter) over the top. In some instances, these baffles were extensively fouled during the deployment (fig. 31). It was not possible to quantitatively determine the effect of progressive bio-fouling on the sediment-collection rate.

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