Biological traits analyses in the study of pollution gradients and ecological functioning of marine soft bottom species assemblages in a fjord ecosystem

Abstract In the present study, biological traits analysis (BTA) was used to explore and characterise effects of pollution on functional attributes of soft bottom infaunal species assemblages. The data comprised 38 sampling stations in the Oslofjord, Norway, ranging from heavily polluted to minimally impacted areas. At each station, species composition (113 taxa in total), contaminants (cadmium, mercury, lead, DDT, PCB) and sediment parameters were determined. Species functions were analysed for eight biological traits defined for activity and life history features. Traits were scored according to the fuzzy coding technique. The most distinct patterns were shown for mobility, size, sediment dwelling depth, feeding type and larval development in relation to contaminants, sediment physical structure and sediment oxidation status. At high levels of contaminants, particularly cadmium, features such as shallow sediment dwelling depth, small size, subsurface deposit feeding and lecitotroph larval development prevailed, while at low contaminant levels characteristic features included deeper sediment dwelling depth, larger size, surface deposit feeding and permanent attachment. Deep sediment dwelling depth (> 15 cm) was related to minimally contaminated oxidised sediments at greater water depths. Mobility and carnivorous feeding prevailed in coarser sediments. The study showed that BTA detected and depicted specific features that correlated with gradients in pollution and may be important for sediment reworking and nutrient cycling. As part of the present work, trait information for > 500 macrofaunal taxa have been assembled and entered in a comprehensive database.