Skip to main content

Research Repository

Advanced Search

Shallow water phytoplankton responses to nitrate and salinity enrichment may be modified by benthic processes

McGowan, Suzanne; Leavitt, Peter R.; Barker, Tom; Moss, Brian


Suzanne McGowan

Peter R. Leavitt

Tom Barker

Brian Moss


The effects of salinity (as chloride [Cl] at 600, 1000, 1600, and 2500 mg L−1) and nitrate (as nitrogen [N] loading rates using concentrations of 1, 2, 5, and 10 mg L−1) additions on phytoplankton communities (as chlorophyll and carotenoid pigments) were determined using a fully factorial 3 m3 mesocosm pond experiment. Redundancy analysis followed by variance partitioning analysis (VPA) statistically compared phytoplankton with water chemistry, zooplankton, phytobenthos (aquatic plants and periphyton), and zoobenthos to understand relationships among benthic and pelagic components. Repeated measures analysis of variance (RM-ANOVA) indicated no interactive effects of the 2 treatments. In VPA, physicochemical variables explained the most variance (33.6%) in the phytoplankton pigment dataset relative to benthic primary producers (0.4%) and invertebrates (2.3%). Salinisation led to an increase in biomass of planktonic siliceous algae (Cl ≥1600 mg L−1) and chlorophytes and cyanobacteria (Cl ≥2500 mg L−1), which we infer was caused by increased phosphorus release from sediments while aquatic plants and periphyton declined. Nitrate additions increased the biomass of cryptophytes and chlorophytes at intermediate N loading rates using concentrations of 5 mg L−1 (associated with greater ammonium [NH4-N] availability and shifts in aquatic plant composition). These findings support the hypothesis that the relative availability of reduced versus oxidised N forms is an important driver of phytoplankton composition. Together, these results suggest that pelagic biota are highly sensitive to salinity and nitrate increases, and that the phytoplankton compositional shifts are driven by indirect effects on water chemistry (bioavailable P mobilisation, changes in N forms), which are mediated by benthic processes.


McGowan, S., Leavitt, P. R., Barker, T., & Moss, B. (2019). Shallow water phytoplankton responses to nitrate and salinity enrichment may be modified by benthic processes. Inland Waters, 10(1), 137-151.

Journal Article Type Article
Acceptance Date Jun 23, 2019
Online Publication Date Oct 24, 2019
Publication Date Oct 24, 2019
Deposit Date Mar 23, 2020
Publicly Available Date Oct 25, 2020
Journal Inland Waters
Print ISSN 2044-2041
Electronic ISSN 2044-205X
Publisher Routledge
Peer Reviewed Peer Reviewed
Volume 10
Issue 1
Pages 137-151
Keywords Aquatic Science; Water Science and Technology
Public URL
Publisher URL
Additional Information This is an Accepted Manuscript of an article published by Taylor & Francis in Inland Waters on 24/10/19, available online:


You might also like

Downloadable Citations