Abstract

The coastal waters of Al-Mukalla, Hadramout Governate, Republic of Yemen, receive considerable amounts of treated and untreated domestic and industrial effluents, which carry a variety of contaminants including heavy metals. We surveyed benthic foraminiferal assemblages as potential indicators for pollution and collected geochemical, sedimentological and water-quality data. Cluster and canonical correspondence analyses delineated three areas: unpolluted areas east and west of Al-Mukalla harbor (biofacies I), a moderately polluted area in and around the harbor (biofacies II), and a highly polluted site within the main harbor (biofacies III). Biofacies I is characterized by sandy sediments with moderate proportions of CaCO3, low total organic matter and low heavy metal concentrations. This biofacies is characterized by pollution-sensitive smaller species (Ammonia parkinsoniana, Discorbinella bertheloti and Pararotalia nipponica). Biofacies II includes sites exposed to southwest monsoon winds, which are characterized by coarse sand relatively rich in CaCO3, as well as more protected sites that are somewhat more muddy, with somewhat higher concentrations of organic matter and heavy metals. Foraminiferal assemblages include larger taxa (Amphistegina lessonii, Peneroplis pertusus, Neorotalia calcar, and Sorites orbiculus), as well as smaller species (Elphidium crispum, Glabratella patelliformis, and Discorbis turbo). Biofacies III is found at a relatively muddy site that is rich in organic matter and heavy metals, particularly Cu and Zn. The foraminiferal assemblage is characterized by pollution-tolerant species, including Ammonia tepida, E. advenum, E. gerthi, Quinqueloculina eburnea, Q. bosciana, Haynesina germanica and Bolivina variabilis. The deleterious effects of pollution on the foraminiferal assemblage of biofacies III are clearly manifested by the highest incidences of test deformation.

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