Foraminifera as proxies for monitoring organic pollution

A field-based approach was combined with an experiment-based approach to investigate the validity of using foraminifera as proxies for monitoring organic pollution (OP) from sewage outfalls. The characteristics that make these protists useful biomonitoring organisms include ecological significance, ubiquitous distribution, abundance, short life-cycles, and fossilization. The potential threat of OP from sewage is still present despite increased levels of treatment, so continual monitoring is essential. The impact of this OP on marine intertidal benthic environments was assessed using foraminifera as proxies. During field surveys, the seasonal pattern of foraminiferal ecology was also investigated to isolate these from the consequences of OP. To assess foraminifera as proxies for monitoring OP: 1. The causality of previously observed positive responses were investigated experimentally. 2. Foraminiferal responses were observed during field surveys in southern UK estuaries (a two-year time-series study of a polluted and comparable clean site, and two field transects across outfalls at two different locations) A petri-dish experiment deduced that Haynesina germanica did not directly consume (and thus did not directly benefit from) sewage-derived particulate organic matter (POM). Ammonia beccarii and Miliammina fusca were also shown to not consume POM directly, in later field/experimental studies. The lipid sewage biomarker coprostanol was used to determine consumption. Mesocosm experiments (allowing other variables to be controlled) indicated that foraminifera did not benefit indirectly from POM increasing food availability. During the field surveys, sewage increased sedimentary algal and bacterial food sources (indicated by the lipid biomarkers, fatty acids), but foraminifera decreased, hypothesized to be due to food increasing predator abundance. Seasonal peaks, dominance and spatial distributions were all affected by sewage, but diversity, assemblage composition and reproduction were not.