The effects of increasing salinity on ecosystem function, resilience and diversity

"July 2005".

Project Number: The effects of increasing salinity on ecosystem function, resilience and diversity - M/BUS/42; CRCFE Project C240.

MDFRC item.

The objectives of the project are therefore: To quantify the effect of a gradient of salinity on key biodiversity (microbes, algae, zooplankton and aquatic plants) and ecological processes (microbial activity, algal production and respiration, zooplankton and aquatic plant recruitment) and, To explore the relationships between the function, diversity and resilience of aquatic systems along a gradient of salinity. These objectives will test the following hypothesis A. Community diversity and structure hypotheses Increased salinity: i) changes the species richness and abundance of biotic groups (aquatic plants, microinvertebrate, phytoplankton and microbes) under experimental mesocosm conditions. ii) decreases the numbers and richness of grazers, causing the numbers and richness of algal populations to increase through reduced grazing and increased nutrient availability. B. Functional hypotheses Increased salinity: iii) will promote a decrease in methanogenesis. If this occurs in association with sulfate-containing waters, a shift to sulfate reduction as the terminal anaerobic respiration process will result, leading to changes in phosphorus dynamics. iv) decreases the sediment’s capacity to retain ammonia, but increases mobilization of iron, leading to a decrease in available phosphorus in sediments and overlying water. v) reduces the concentrations of dissolved nutrients so that the relative importance of benthic algae increases over phytoplankton. vi) affects the capacity of algae to take in nutrients, with the impact being dependent on salt concentration, salt composition and relative nutrient concentration. This impacts productivity and community composition. vii) differentially restricts the photobiology of algae causing changes in primary production, system productivity (and community composition). viii) changes the capacity of biotic groups to reproduce. ix) will change recruitment of microinvertebrates and aquatic plants.