Relations between macroinvertebrates, nutrients, and water quality criteria in wadeable streams of Maryland, USA

Abstract

In an ongoing effort to propose biologically protective nutrient criteria, we examined how total nitrogen (TN) and its forms were associated with macroinvertebrate communities in wadeable streams of Maryland. Taxonomic and functional metrics of an index of biological integrity (IBI) were significantly associated with multiple nutrient measures; however, the highest correlations with nutrients were for ammonia-N and nitrite-N and among macroinvertebrate measures were for Beck's Biotic Index and its metrics. Since IBI metrics showed comparatively less association, we evaluated how macroinvertebrate taxa related to proposed nutrient criteria previously derived for those same streams instead of developing nutrient-biology thresholds. We identified one tolerant and three intolerant taxa whose occurrence appeared related to a TN benchmark. Individually, these taxa poorly indicated whether streams exceeded the benchmark, but combining taxa notably improved classification rates. We then extracted major physiochemical gradients using principal components analysis to develop models that assessed their influence on nutrient indicator taxa. The response of intolerant taxa was predominantly influenced by a nutrient-forest cover gradient. In contrast, habitat quality had a greater effect on tolerant taxa. When taxa were aggregated into a nutrient sensitive index, the response was primarily influenced by the nutrient-forest gradient. Multiple lines of evidence highlight the effects of excessive nutrients in streams on macroinvertebrate communities and taxa in Maryland, whose loss may not be reflected in metrics that form the basis of biological criteria. Refinement of indicator taxa and a nutrient-sensitive index is warranted before thresholds in aquatic life to water quality are quantified.

Water quality related macroinvertebrate community responses to environmental gradients in the Portoviejo River (Ecuador)

“…x is consistent with the literature, as it has been shown that there is a strong relationship between nutrient concentrations and macroinvertebrate communities (Ashton et al, 2014).…”

Inexpensive spot sampling provides unexpectedly effective indicators of watershed nitrogen status

“…When the focus is on differences in average nitrogen levels among watersheds driven by different amounts of nitrogen enrichment, frequent sampling may not be needed. Our results also support stream assessment protocols that collect one spring nitrate sample to assess watershed and stream nitrogen status (Ashton et al 2014, Stranko et al 2017).…”

“…For each site, we selected from the CBNTN concentration database the first uncensored TN and NO 3 measurements taken in March 2012 (see Moyer et al [2012] for information on censoring). The month of March begins the period when streams are commonly visited for stream assessment (e.g., Ashton et al 2014, Stranko et al 2017). We call these potential predictors fsTN and fsNO 3 in the rest of the paper.…”

Headwater stream condition and nutrient runoff: Relating SWAT to empirical ecological measures in an agricultural watershed in Pennsylvania

“…Although nutrient pollution is part of the human disturbance gradient, studies investigating the link between macroinvertebrate responses and nutrients vary and, at times, conflict in their results (Calhoun, Gregory, & Weyers, 2008; Wang, Robertson, & Garrison, 2007). Although macroinvertebrates exhibit decreasing trends with increasing nutrient concentrations, relationships are often inconsistent and confounded by co‐occurring factors related to instream habitat, hydromorphology, riparian condition, and surrounding land use (Ashton, Morgan, & Stranko, 2014; Genito, Gburek, & Sharpley, 2002; Kyriakeas & Watzin, 2006; Miltner & Rankin, 1998; Wang et al., 2007; Yuan & Norton, 2004).…”