A novel bioassay to assess phytoplankton responses to soil-derived particulate nutrients

Hannah M Franklin; Alexandra Garzon-Garcia; Joanne Burton; Philip W Moody; Robert W De Hayr; Michele A Burford

doi:10.1016/j.scitotenv.2018.04.195

A novel bioassay to assess phytoplankton responses to soil-derived particulate nutrients

Sci Total Environ. 2018 Sep 15:636:1470-1479. doi: 10.1016/j.scitotenv.2018.04.195. Epub 2018 May 5.

Authors

Hannah M Franklin¹, Alexandra Garzon-Garcia², Joanne Burton², Philip W Moody³, Robert W De Hayr³, Michele A Burford⁴

Affiliations

¹ Australian Rivers Institute, Nathan Campus, Griffith University, 170 Kessels Road, Nathan, Brisbane, Queensland 4111, Australia. Electronic address: h.franklin@griffith.edu.au.
² Australian Rivers Institute, Nathan Campus, Griffith University, 170 Kessels Road, Nathan, Brisbane, Queensland 4111, Australia; Landscape Sciences, Department of Environment and Science, PO Box 5078, Brisbane, Queensland 4001, Australia.
³ Landscape Sciences, Department of Environment and Science, PO Box 5078, Brisbane, Queensland 4001, Australia.
⁴ Australian Rivers Institute, Nathan Campus, Griffith University, 170 Kessels Road, Nathan, Brisbane, Queensland 4111, Australia; School of Environment and Sciences, Griffith University, 170 Kessels Road, Nathan, Queensland 4111, Australia.

PMID: 29913607
DOI: 10.1016/j.scitotenv.2018.04.195

Abstract

Terrestrial particulate nutrients transported during flood events are known to indirectly fuel phytoplankton blooms in rivers, lakes and coastal waters, although the mechanisms are poorly understood. Quantifying the response of phytoplankton to nutrients in sediments eroded from catchments is fundamental to prioritizing areas for erosion control. This study developed a novel bioassay technique for rapidly assessing the effects of nutrients released from suspended sediments on the growth of marine and freshwater phytoplankton communities. A range of sediment slurries were placed in bioassay bottles within dialysis tubing in the presence of phytoplankton and their photosynthetic efficiency (F_v/F_m) was measured over 72 h. This allowed an assessment of the effects of dissolved nutrients released from sediments without the confounding effects of suspended sediments. Chlorophyll a concentrations were also measured for comparison with F_v/F_m. Our study showed F_v/F_m was an effective method for measuring phytoplankton responses to sediment slurries. Photosynthetic efficiency was a more sensitive response metric than chlorophyll a. Applying the method to a range of suspended sediments from two tropical catchments in Australia that drain into Great Barrier Reef coastal waters, we identified a subset of sediment types (~40%) that increased F_v/F_m under the bioassay conditions. These sediments have the potential to stimulate marine and freshwater phytoplankton growth under the loads simulated in this study. The bioassay has the advantage of being a rapid and relatively simple method where a large number of sediments can be simultaneously tested for a phytoplankton response. To our knowledge this is the first time F_v/F_m has been used to assess phytoplankton responses to sediments in a bioassay. This approach advances the use of F_v/F_m as a sensitive indicator of phytoplankton responses to nutrients and could be used to develop indices of the relative risk various sediments pose, hence support decision making for erosion control measures.

Keywords: Fluorescence; Freshwater; Great Barrier Reef; Marine water; Maximum quantum yield of PSII; Microalgae.

MeSH terms

Australia
Biological Assay / methods*
Chlorophyll
Chlorophyll A
Environmental Monitoring / methods*
Geologic Sediments
Nitrogen / analysis*
Phosphorus / analysis*
Phytoplankton / physiology*

Substances

Chlorophyll
Phosphorus
Nitrogen
Chlorophyll A