title: Human impacts on large benthic foraminifers near a densely populated area of Majuro Atoll, Marshall Islands.
abstract: Human impacts on sand-producing, large benthic foraminifers were investigated on ocean reef flats at the northeast Majuro Atoll, Marshall Islands, along a human population gradient. The densities of dominant foraminifers Calcarina and Amphistegina declined with distance from densely populated islands. Macrophyte composition on ocean reef flats differed between locations near sparsely or densely populated islands. Nutrient concentrations in reef-flat seawater and groundwater were high near or on densely populated islands. delta(15)N values in macroalgal tissues indicated that macroalgae in nearshore lagoons assimilate wastewater-derived nitrogen, whereas those on nearshore ocean reef flats assimilate nitrogen from other sources. These results suggest that increases in the human population result in high nutrient loading in groundwater and possibly into nearshore waters. High nutrient inputs into ambient seawater may have both direct and indirect negative effects on sand-producing foraminifers through habitat changes and/or the collapse of algal symbiosis.
authors.affiliation: Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Osawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Fujita
authors.forename: Yu
authors.initials: Y
authors.lastname: Umezawa
authors.forename: Hajime
authors.initials: H
authors.lastname: Kayanne
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ide
authors.forename: Tatsutoshi
authors.initials: T
authors.lastname: Nagaoka
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Miyajima
authors.forename: Hiroya
authors.initials: H
authors.lastname: Yamano
mesh_terms: D004777:Environment; D004784:Environmental Monitoring / Q000379:methods*; D056908:Foraminifera / Q000254:growth & development*; D005618:Fresh Water / Q000737:chemistry; D006801:Humans; D008849:Micronesia; D009584:Nitrogen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D011156:Population Density; D012623:Seawater / Q000737:chemistry; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D010710:Phosphates; D014873:Water Pollutants; D009584:Nitrogen