Diatom Assemblage Changes in Agricultural Alluvial Plain Streams and Application for Nutrient Management

Abstract

In large, alluvial floodplains dominated by agriculture, small streams have the potential to experience nutrient enrichment affecting algal assemblage structure and metabolism. Nutrient enrichment is largely driven by application of nutrients and altered hydrologic regimes. To inform stressor–response‐based nutrient reduction goals for agricultural alluvial plain streams, diatom assemblages were sampled from 25 streams located within the Mississippi Alluvial Plain (MAP) with various land management practices and associated P and N inputs. From August through September 2015, epidendric diatom assemblage samples were collected from instream woody debris. Field nutrient gradients were skewed toward higher concentrations, and ranges of previously reported diatom assemblage response thresholds indicative of oligotrophic conditions were not well represented. Ordination analysis identified a gradient in species composition associated with increasing P and decreasing dissolved oxygen. A significant shift in diatom assemblage structure occurred when total P concentrations in the MAP streams exceeded 0.12 mg L−1. Phosphorus‐enriched systems were represented by a distinct set of indicator species, lower abundances of ubiquitous species, greater abundances of highly tolerant species, and greater abundances of high‐P indicator species. No relationships were observed among diatom assemblage measures or traits with increasing N. Current results do not address potential criteria for identifying high‐quality, oligotrophic streams. However, measures of diatom assemblage structure have potential for helping set benchmarks to reduce nutrient impacts and monitor effects of agricultural best management practices on MAP streams. Core Ideas Identifying stream nutrient indicators is difficult in agricultural landscapes. Diatoms found in Mississippi Alluvial Plain streams are sensitive to changes in P concentrations. Diatom assemblages shifted when stream total P concentrations exceeded ∼0.12 mg L−1. Diatom measures can help set nutrient reduction goals for agricultural streams. Stream diatom indicators may improve monitoring success of nutrient best management practices.

Diatom communities and ecological status classification in the upper Po River basin

“…Recently, homogenization of diatom communities has also been observed in response to hydrological alterations and urbanization in Mediterranean rivers which also led to significant species loss at both local and regional scales (Falasco et al, 2021a) and a reduced role of diatoms in the total benthic chlorophyll-a (Piano et al, 2016). Moreover, the present study confirmed the high trophic value of some species, mainly collected in the R-C macrotype, such as N. gregaria (Hicks and Taylor, 2019;Hausmann et al, 2016;Szczepocka et al, 2016), Nitzschia palea (Licursi et al, 2016;Szczepocka et al, 2016;Yang et al, 2015), Gomphonema parvulum (Lu et al, 2020;Szczepocka et al, 2016) and C. euglypta (Trábert et al, 2020). S. nigri was confirmed as one of the most tolerant diatom species (see Hausmann et al, 2016 as Eolimna minima;Yang et al, 2015).…”

Diatom Taxonomic Composition as a Biological Indicator of the Ecological Health and Status of a River Basin under Agricultural Influence

“…Understanding how diatom community assembly is linked to environmental factors is a vital key to improving agricultural eutrophic rivers ecosystem management [2]. In Lalin River Basin, the main factors emanating from agricultural activities that impacted the aquatic organisms were organic and persistent organic pollutants [1,20].…”

“…During the past decades, however, agricultural practices have significantly increased, causing visible effects on rivers (overuse of pesticides or fertilizer, etc. ), but their impacts have been very difficult to assess [2,3]. Ice-covered periods of rivers can play an essential role in nutrient cycling and biodegradation in rivers of the temperate zone [4].…”

DNA metabarcoding effectively quantifies diatom responses to nutrients in streams

“…However, many diatom species are indicators of TP concentrations >100 µg/L (Potapova and Charles 2007), suggesting that additional changes in taxa and assemblage structure in high nutrient systems could be expected. Though less common, some studies have reported changes in diatom species and assemblages at higher TP (up to 156 µg TP/ L) and TN (up to 1,100 µg TN/L) concentrations (Smith and Tran 2010, Chambers et al 2012, Lavoie et al 2014, Hausmann et al 2016, Taylor et al 2018, Hicks and Taylor 2019.…”