The effect of oxygen stress (hypoxia and anoxia) on free-living marine nematodes in coastal ecosystems
Oxygen stress, including hypoxia and anoxia in the coastal waters, is increasing worldwide due to natural and anthropogenic reasons. As free living marine nematode prefer to live in oxic condition, their response to oxygen stress can include changes in density, community structure, diversity and altered abundance of some dominant species. Furthermore, responses of nematode communities are species–specific and related to oxygen stress duration. In addition, different sediment types are characterised by different biogeochemical environments, which is reflected in the natural adaptation of nematode communities to oxygen stress events.
In this PhD thesis, we investigate the response of different nematode communities (in terms of densities, diversity, community composition and vertical profiles) to the induced hypoxia and anoxia events in the overlying water over time.
Our results showed that subtidal nematode communities in the three contrasting sediment types were tolerant against short-term hypoxia (1 and 7 days) . Furthermore, our preliminary results indicated that 9 days anoxia could not effect on marine nematodes while in longer periods (1 and 10 months) density, species number and diversity decreased sharply.
In conclusion, our results showed that nematodes were tolerant to short term oxygen stress (hypoxia and anoxia) . This may relate to adaptation mechanisms of nematodes to live naturally in low oxygen environments. Furthermore, longer stress duration can make unfavourable conditions in the sediment (e.g increasing H2S concentration) which can increase the negative effects of oxygen stress.