Temporal stability of phytoplankton functional groups within two agricultural irrigation ponds in Maryland, USA

Authors: SMITH, JACLYN - ORISE FELLOW; WOLNY, JENNIFER - FOOD AND DRUG ADMINISTRATION(FDA); STOCKER, MATTHEW - ORISE FELLOW; HILL, ROBERT - UNIVERSITY OF MARYLAND EASTERN SHORE (UMES); Pachepsky, Yakov

Submitted to: Frontiers in Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2021
Publication Date: 11/1/2021
Citation: Smith, J.E., Wolny, J.L., Stocker, M.D., Hill, R.L., Pachepsky, Y.A. 2021. Temporal stability of phytoplankton functional groups within two agricultural irrigation ponds in Maryland, USA. Frontiers in Water. https://doi.org/10.3389/frwa.2021.724025.
DOI: https://doi.org/10.3389/frwa.2021.724025

Interpretive Summary: Phytoplankton are a fundamental microbial population found in various water bodies. They are primary producers and a staple to aquatic food webs. Phytoplankton have been previously found to be effective bio-indicators of water quality and the waterbodies health. Populations of phytoplankton are often divided into functional groups based on their morphology, physiology, and ecological attributes. These functional groups and their influence on water quality have been studied in various types of water bodies but have yet to be studied in agricultural irrigation ponds. It has been established that freshwater bodies tend to lack uniformity in phytoplankton populations across the water body, Improvements in the monitoring of phytoplankton populations may be achieved if consistency can be found in the phytoplankton spatial patterns. We studied two working agricultural irrigation ponds located in Maryland, USA over two summer sampling campaigns in 2017 and 2018. Concentrations of four phytoplankton functional groups, along with sensor-based and fluorometer based water quality parameters were measured. Both ponds contained locations where specific phytoplankton functional group concentrations tended to be consistently higher or lower than the pond’s average concentration for each sampling date. Such patterns were caused with by conditions, pond morphology, and human activities. The existence of patterns of consistent irregularities in phytoplankton functional group concentrations can affect the outcome of a water quality assessment and should be considered in water quality monitoring designs. Results from this work will be useful for researchers, professionals, and consultants in the water quality field who utilize in situ sensing, to monitor or assessphytoplankton populations across freshwater bodies.

Technical Abstract: Phytoplankton functional groups and their influence on water quality have been studied in various types of water bodies but have yet to be studied in agricultural irrigation ponds. Freshwater sources (e.g., lakes, creeks, streams) have been previously shown to exhibit high spatial and temporal variability in phytoplankton populations. Improvements in the monitoring of phytoplankton populations may be achieved if patterns of stable spatial variability can be found through time. The objective of this work was to determine if temporally stable spatial patterns in phytoplankton communities could be detected in agricultural irrigation ponds using a functional group approach. The study was performed at two working agricultural irrigation ponds located in Maryland, USA over two summer sampling campaigns in 2017 and 2018. Concentrations of five phytoplankton groups, along with sensor-based and fluorometer based water quality parameters were measured. Temporal stability was assessed using mean relative differences between measurements in each location and averaged measurements across ponds on each sampling date. Temporally stable spatial patterns of major phytoplankton functional groups were found for both ponds over the two sampling years. Both ponds had locations where specific phytoplankton functional group concentrations were consistently higher or lower than the pond’s average concentration for each sampling date. Temporally stable spatial patterns were also found for subgroups of diatoms, green algae, and cyanobacteria. Zones of consistently higher or lower than average concentrations were associated with flow conditions, pond morphology, and human activities. The existence of temporally stable patterns of phytoplankton functional group concentrations can affect the outcome of a water quality assessment and should be considered in water quality monitoring designs.