The Muds of the Clyde Sea Area. III. Chemical and Physical Conditions; Rate and Nature of Sedimentation; and Fauna

Abstract

A PRELIMINARY survey of the area with regard to the distribution of the total nitrogen and phosphate content of the muds was described in a previous paper (Moore,5). A number of stations were worked, and these were further examined for nature and distribution of particles, water content, and density, and as a result of this survey certain stations were chosen as suitable for more extensive work. At the same time it became evident that the layers in which the greatest and most important changes were taking place were those within a few centimetres of the surface, and these were therefore studied most intensively.Among these stations many show very irregular deposition, owing to tidal currents or other causes. At some, conditions appear to be comparatively'stable, and a series of these was chosen to illustrate the four chief types of mud found in this area, which are as follows :-Deep Water Type. This is found in the deepest channels where there is little or no tidal action, a slow rate of sedimentation and very little influence from the land, e.g. Station 7, no metres; St. 7b, 166 metres; St. 23, 73 metres.Mid-Loch Type. This is a shallower water type than the preceding, usually in a depth of 45 to 75 metres. There is little tidal action and the small amount of matter received from streams is of very fine grade. Deposition is more rapid, and the mud tends to be softer than in the previous type, e.g. Station 8b, 37 m.; St. 9, 37 m., Kyles of Eute; St. n, 73 m., Loch Striven; St. 13, 73 m., Loch Goil; St. 13a, 82 m. ; St. 15,58 m.; St. 15a, 64 m., Loch Long; St. 16a, 26 m., Holy Loch.

Some Measurements of the Sinking Rate of Fecal Pellets1

“…Plankton fecal pellets are more friable than those produced by benthic animals ( Moore 1931a), and a 50% reduction in carbon content may occur within several days after pellet formation (Johannes and Satomi 1966). Vinogradov ( 1961) observed that even very fast sinking pteropods are generally devoid of organic matter below 500 m, presumably because density discontinuity layers significantly reduce sinking rate from that expected from experimental data.…”

“…The availability of zooplankton fecal pellets as food is related in part to the depths to which they can sink. Moore (1931a) detected zooplankton fecal pellets in nearshore sediments to depths of 166 m and followed their production and sinking characteristics during a spring phytoplankton bloom. Osterberg, Carey, and Curl ( 1963) gave an average sinking rate for Euphausia pacifica fecal pellets.…”

Muds of the Clyde Sea Area. II. Bacterial Content

“…The samples examined were all from the Clyde Sea AIea, a brief description of which is given by Marshall and Orr (12); the stations used for mud sampling are described by Moore (9,10). The bottom deposits are chiefly muds, with some sands; these are classified into four types by Moore (10), and stations representative of each of these four types were selected for bacteriological analysis as under :- The samples were obtained by means of the apparatus described by Moore and Neill (11).…”

Hydrographic Control of Meiobenthos in Bermuda1

“…Por and Masry (1968) found large populations of the nematode Eudorylaimus andrassyi (Meyl) surviving and reproducing during an 8-month anoxic period in the bottom waters of Lake Tiberias. Certain nematodes can survive anoxybiotically for up to 60 days in the laboratory (Moore 1931;Wieser and Kanwisher 1961). Some genera are highly tolerant of reducing conditions while others survive for very short periods.…”

“…The rapid disappearance of the copepods is not surprising. Both Moore ( 1931) and Tietjen (1969) found that copepods died when the medium became anoxic.…”