Influence of methane and other hydrocarbon gases on foraminifera and nematodes in the Northwestern part of the Black Sea.

This study investigates the response of foraminifera and nematodes to different types of methane and other hydrocarbon gases (alkanes, alkins) in bottom sediments of the northwestern shelf and continental slope of the Black Sea. Foraminifera are represented by 39 species from six orders, 13 families, 24 genera. Nematoda are represented by 48 species from six orders, 17 families, 27 genera. Both groups of meiobenthos are characterized by impoverished simple diversity and abundance/density as well as by much smaller sizes of foraminiferal tests compared to those from areas not affected by hydrocarbon gases, indicating stressful conditions for their life in the study areas. Among foraminifera, calcareous hyaline taxa dominate, but agglutinated forms are present as well and occasionally play a dominant role. A significant number of the identified nematode species belong to the tyobiotic type from the families Comesomatidae and Linhomoidae. They are characterized by a long, thin body and a small or completely undeveloped oral cavity, indicating their feeding on small particles of sediment or bacteria. Nine groups of foraminifera and nematodes were identified according to their tolerance and sensitivity to methane (15 species), ethane (five species), propane (eight species), butane (10 species), pentane (11 species), ethylene (20 species), propylene (two species), acetylene (three species), and isobutylene (one species). This study provides evidence for the first time that different types of methane, its homologues, and other hydrocarbon gases affect the reproduction, diversity, abundance, and growth of foraminifera, as well as density and simple diversity of nematodes.