Correlation between textural characteristics of marine sediments and benthic foraminifera in highly anthropogenically-altered coastal areas

The coastal zone is the most variable area in the marine system in terms of environmental parameters and it is characterised by the highest granulometric variability. Considering that the distribution of benthic foraminifera is controlled by several biotic and abiotic factors, including sediment texture, this may be considered one of the main factors influencing foraminiferal assemblage composition. The role of sediment grain size on foraminiferal species distribution has been recognised by several studies, but only in a few cases it has been considered from a quantitative viewpoint. On this rationale, 137 sediment samples collected in three different Italian National Relevance Sites (Bagnoli, Baia and Augusta), affected by different type and degree of pollution, were analysed for grain size and benthic foraminifera. Although the influence of pollution on foraminifera distribution in these areas had been recognised in earlier studies, the present research applied statistical analysis (Pearson Correlation and Co-Inertia Analysis) in order to highlight the correlation between sediment fractions and foraminiferal species. The correlation found in all sites between the most abundant species and specific sediment fractions indicated that sediment grain size is a primary factor controlling species distribution. The effect of sediment type conditions the distribution of previously recognised pollution tolerant species, which show preference for silty and/or clayey sediments. Because muddy sediments favour contaminant accumulation, such species are more exposed to polluted habitats and consequently their tolerance to anthropogenically-altered conditions may be considered an adaptive strategy.

► We studied the preference of foraminiferal species for selected sediment fractions.
► A general preference of some species for specific sediment fractions was recognised.
► Sediment controls species distribution both in moderately and heavily polluted sites.
► Groups of species with different trophic needs showed preference for sand or mud.
► Species selecting fine sediment may be pollution tolerant due to adaptive strategy.