Meiofaunal Effects on Nutrient Fluxes and Profiles in Marine Sediments

[摘要] The main objective of my work has been to assess the effects of meiofauna on fluxes of dissolved nutrients through the sediment- water interface and on nutrient profiles in sediment porewaters. This work has been carried out using a combination of laboratory experiments and field surveys. My laboratory work has concerned the effects of meiofauna on interfacial nutrient fluxes under a range of biological, physical and chemical conditions. My field work has concerned the correlations between porewater nutrient profiles and various biological, physical and chemical parameters in two very different environments. Manual chemical methods have been developed for the analysis of silicate, phosphate, sulphate, nitrate and ammonia on two millilitres of sample. The smear-ratio direct counting method for soil micro-organisms has been modified for use on marine sediments. Modified diffusion cells have been developed for studying interfacial fluxes in marine sediments in the laboratory. These cells have been used for all of my laboratory experiments. The effects of macrofauna, meiofauna and micro-organisms have been compared. Meiofauna generally have the greatest effect on nutrient fluxes. Macrofauna may reduce the effects of meiofauna. Micro-organisms alone tend to have the least effect on fluxes. The effects of meiofaunal type and density on nutrient fluxes have been examined. Nematodes and copepods, the most prevalent meiofaunal groups in my sediment, usually have the most effect on fluxes. Less prevalent groups of meiofauna may alter the direction and magnitude of fluxes. Changes in meiofaunal density have less effect than changes in types of meiofauna. The effects of salinity, compaction, oxygen saturation and particle size range on fluxes in the presence of nematodes and copepods have been examined. Those of salinity are generally greatest. Physical and chemical parameters are more important in determining fluxes from and to the overlying water. Meiofaunal factors are more important in determining transfer of nutrients within the sediment column. A survey of seven deep-sea sites in the central Pacific ocean has been conducted , and correlations between the biological and chemical parameters measured and porewater nutrient concentrations have been calculated. Nutrient concentration is most strongly correlated with microorganism density, water content and metazoan meiofauna densities. A survey of four sites in the Tamar estuary, Plymouth, has been conducted and correlations between the biological, chemical and physical parameters measured, and porewater nutrient concentrations calculated. Nutrient concentration is most strongly correlated with salinity, water content, meiofaunal and microbial density. The relationship between nutrient fluxes and concentration profiles, and the biological, physical and chemical parameters I have measured have been discussed, as have the possible causes of meiofaunal effects on nutrient fluxes and the interaction between biological, physical and chemical parameters.

[发布机构] University:University of Glasgow

[关键词] Biological oceanography, Chemical oceanography