Deep Water Renewal in Fjords

Abstract

Benthic faunal reactions to oxygen deficiency in ten fjords and estuaries in northern Europe are reviewed. Chosen areas exhibit both permanent and temporary oxygen deficiency due to organic enrichment and/or geomorphological conditions. Number of species, abundance, biomass, and faunal composition are given in relation to oxygen concentration. Results show that the measured faunal parameters do not change gradually with oxygen concentration, but abruptly at approximately 2 mg O2 litre −1Benthic faunal reactions to oxygen deficiency suggest the following grouping: 1. Non-tolerant species; most species 2. Tolerant species; mainly molluscs 3. Transitory opportunists; pioneer polychaete colonists appearing when conditions improve 4. Transitory emigrants; mobile species