Measurement of biological oxygen demand in sandy beaches

Abstract

Measurements of biological oxygen demand in a sandy beach using conventional in situ techniques are compared with laboratory measurements of interstitial oxygen changes in intact cores. Oxygen uptake as measured in the laboratory was approximately three times that measured in the field despite the fact that the cores were undisturbed. In addition, the effect of disturbance on sediment cores was investigated and it was found that oxygen demand in disturbed cores increased by up to 60%, due mainly to an increase in bacterial activity. This effect was still evident after 24 hours of incubation. The applicability of conventional respirometer techniques to well-drained systems such as open sandy beaches is questioned and an alternative approach suggested.

Bepalings van biologiese suurstof aanvraag deur gebruikmaking van in situ tegnieke word vergelyk met laboratorium bepalings van interstitiele suurstof verandering in intakte sediment kerne. Suurstof opname, soos bepaal in die laboratorium, was ongeveer drie maal hoer as wat in die veld bepaal is, ongeag van die feit dat die kerne ongesteurd gelaat is. Boonop was die effek van versteuring op die sediment kerne ondersoek en die resultate dui daarop dat suurstof opname in die versteurde kerne tot soveel as 60% verhoog, hoofsaaklik te wyte aan verhoogte bakteriese aktiwiteit. Hierdie effek was reeds waarneembaar na 24 uur inkubasie. Die toepasbaarheid van die konvensionele respirometer tegnieke op goed gedreineerde sisteme soos oop sandstrande word bevraagteken en 'n alternatiewe benadering word voorgestel.