Benthic foraminiferal assemblages from Kiritimati (Christmas) Island indicate human-mediated nutrification has occurred over the scale of decades

Community assemblages of live and dead benthic foraminifera from Kiritimati (Christmas) Island, Kiribati, were used to investigate changes in nutrification before and after human occupation. Benthic foraminiferal assemblages have previously been shown to have strong empirical relationships with water quality: mixotrophic, symbiont-bearing foraminifera dominate in clear, nutrient-poor waters, while heterotrophic and/or opportunistic foraminifera are more prevalent in polluted or nutrified waters. After human occupation, the proportion of mixotrophic taxa decreased significantly at all sites on Kiritimati with the largest decreases observed at sites with the highest fishing pressure. These changes in the benthic foraminiferal assemblage indicate that nutrification has occurred on Kiritimati over the scale of decades, possibly due to changes in trophic structure and nutrient cycling caused by fishing.