Cultural Eutrophication Is Reflected in the Stable Isotopic Composition of the Eastern Mudsnail, Nassarius obsoletus

Abstract

In aquatic ecosystems, biological indicators are used in concert with nutrient concentration data to identify habitat impairments related to cultural eutrophication. This approach has been less commonly implemented in coastal areas due to the dominance of physical conditions in structuring biological assemblage data. Here, we describe the use of the stable isotopic composition of (Say), the eastern mudsnail, as an indicator of cultural eutrophication for 40 locations in coastal estuaries in New York. We found N enrichment in mudsnail tissue where watersheds had high population densities, land use patterns were more urbanized, and when sampling sites were adjacent to wastewater treatment plant discharges. Stable carbon isotopes were responsive to salinity and watershed forest cover, with more saline sites reflecting a predominantly C or algal carbon isotopic signature and more forested sites a lighter isotopic signature reflecting greater inputs of C terrestrial detrital carbon. Mudsnail nitrogen isotopic composition had a high level of separation between more affected and pristine watersheds (from 6.6 to 14.1‰), highlighting its utility as an indicator. We thus propose that stable isotope values of estuarine biota, such as the eastern mudsnail, can be used in concert with water quality data to identify areas where improvements in water quality are needed and can also be used to identify sources of detrital carbon to estuarine environments.

Human pressures on two estuaries of the Iberian Peninsula are reflected in food web structure

“…δ 13 C is typically used to determine the origin of carbon sources 28 . δ 15 N values allow the study of trophic levels of consumers 28 , and the enriched nitrogen isotopic composition of biota can be an indicator of anthropogenic wastewater 27,29 . However, nutrient contamination studies that include multiple taxa and different trophic levels in the food webs are not common 30 .…”

Use of historical isoscapes to develop an estuarine nutrient baseline

“…Additionally, spatial patterns showed that expression of eutrophication is enhanced behind tidal restrictions (Hughes et al, 2011). While these studies raised concerns about symptoms of eutrophication, biological assimilation can mask the detection of elevated N inputs by monitoring programs (Watson et al, 2017;Jeppesen et al, 2018;Sańchez et al, 2023). Datasets of multiple monitoring parameters including dissolved and sediment nutrients, oxygen and pH, phytoplankton and microalgal abundance each provide useful information for managers when setting goals for N reduction but are limited by their 30-year timescale.…”

Tidal Flushing Rather Than Non-Point Source Nitrogen Pollution Drives Nutrient Dynamics in A Putatively Eutrophic Estuary

“…Because coastal systems are changing over long periods of time, with shifting nutrient inputs, warming waters, and other effects of climate change, researchers have developed and refined methods to measure the δ 15 N values of shell-bound organic material, allowing them to glean information about historical N sources and sinks from archival samples [ 28 – 30 ]. These values serve as a record of δ 15 N of suspended particulate matter (SPM) [ 31 , 32 ] and provide information about N sources to the mollusk which reflect local nutrient processing [ 33 ]. Shells from museum collections, archives, and excavations from dated middens allow us to develop timelines of N sources and cycling that extend back thousands of years [ 22 , 31 ].…”