More than ten seagrass blades per photo were observed in hundreds of
the 5300 photographs examined (Roper and Brundage, 1972). There is no information on the average area covered per photo, but in Figute y9 about 20 apparent blades occur within an area of about 40 mi, After a hurricane, 48 blades per photograph were recorded on the Blake Plateau at 516 m depth(Menzies et al., 1967); the area covered tr photo is not stated.
A considerably higher concentration than those previously recorded prevails in the Tongue of the Ocean, a deep"fjord" in the shallow Great Bahama Bank. This is evidenced, partly by a photograph taken from D.S.R.V. "Alvin at 2375 m depth(Fig. 6i), partly by da:a which were kindly supplied by Dr. G. T. Rowe: Several thousand photographs taken from the''Alvin'' along a transect of the Tongue for the amount of seagrass on the bottom were analyzed by P. Polloni and N. Staresinic The total area surveyed was 904 m2, and no less than 11.3 m' or 1.2% of the bottom proved to be covered with a layer of detrital Thalassia. The quantities dredged by the"Pilisbury" and the"Akad. Kur- chatov" are recorded in Table 1(p. 202). The former vessel used a 41- foot otter trawl, usually working for 4 hours at depths greater than 4500 m and for 2 hours at shallower depths. The hauls of the"Kurchatov" with a 3-m sledge trawl lasted about one hour. However, the speed over the bottom is not known, and it is also uncertain whether the trawl was actually on the bottom during the whole period. Thus, the quantities por station are not easily comparable. Larger samples P15 g) were obtained only at 12 of the 31"Kurchatov “trawling stations occupied at depths exceeding 1000 m, and a 31"Pillsbury" stations. 10 of which contained no larger samples occurred at all.
The larger samples occurred stations(except a few) in the trough Puerto Rico and Cayman Trenches. and in addition particularly the Yucatan Basin, which is close to the extensive Thalassia areas the adjacent Mexican coast. This occurrence probably reflects sportation by slumping and/or turbidity currents rather than by the 1fing method.