An apparatus is described which has been used at three sites in Southampton Water for the continuous collection of sedimenting detritus. The collected detritus was removed at monthly intervals for measurement, and for analysis of the organic carbon and nitrogen content.
The total quantities of dry detritus varied from 4 mg/cm2/month to 980 mg/cm2/month, and because of the variable collection of resuspended bottom material show no clear seasonal variation. The carbon content was 0.1–7.3% of the total and nitrogen varied from 0.02 to 0.62%. The organic content did show some seasonal variation which tended to follow changes in the abundance of phytoplankton.
The amounts of total detritus collected and the organic content are high compared with some other areas and this is thought to be due partly to the high primary productivity of the area and partly to the complex water movements in the estuary.
The importance of detritus in suspension in the sea and as a superficial layer on the sediment is well recognized. The quantity of detritus in sea water has been measured (Armstrong & Atkins, 1950; Fox, Isaacs & Corcoran, 1952; Krey, 1950, 1961a, b, 1964; Krey, Banse & Hagmeier, 1957; Hagmeier, 1962) and usually exceeds the amount of living material in suspension by at least a factor of ten. Study of deposited detritus has mainly involved measurement of the amount of organic matter in bottom sediments (Waksman, 1933; Anderson, 1939; Southward, 1952; Morgans, 1956; Sanders, 1960).
In studies of marine productivity it is important to know not only the amount of detritus present in the water column, but also its composition and rate of sedimentation.