Long-term ecological research in freshwaters enabled by regional biodiversity collections, stable isotope analysis, and environmental informatics

Abstract

Biodiversity collections are experiencing a renaissance fueled by the intersection of informatics, emerging technologies, and the extended use and interpretation of specimens and archived databases. In this article, we explore the potential for transformative research in ecology integrating biodiversity collections, stable isotope analysis (SIA), and environmental informatics. Like genomic DNA, SIA provides a common currency interpreted in the context of biogeochemical principles. Integration of SIA data across collections allows for evaluation of long-term ecological change at local to continental scales. Challenges including the analysis of sparse samples, a lack of information about baseline isotopic composition, and the effects of preservation remain, but none of these challenges is insurmountable. The proposed research framework interfaces with existing databases and observatories to provide benchmarks for retrospective studies and ecological forecasting. Collections and SIA add historical context to fundamental questions in freshwater ecological research, reference points for ecosystem monitoring, and a means of quantitative assessment for ecosystem restoration.

Keywords: biodiversity collections; ecosystem restoration; environmental stressors; freshwater biology; stable isotope analysis.

Figure 1.

A histogram superimposed on a cumulative distribution (the solid dark line) of georeferenced lots plotted by decade for the 10 most abundant freshwater fish species identified in Fishnet2 (https://fishnet2.net), a data portal and aggregator for US fish collections. The term lot refers to a sample of specimens of a particular species collected at the same place and time and cataloged as a unit. Important time blocks and transitions are identified by events (text) that correspond to the summary processes column in table 1.

Figure 2.

Spatial distributions of georeferenced lots for the 10 most abundant freshwater fish species, aggregated within time frames that correspond to those identified in table 1 and figure 1. The Panels represent time frames (a) from before 1900 to 1930, (b) 1931–1965, (c) 1966–1999, and (d) from 2000 to the present. The dark lines and numbers demarcate major watershed areas of the continental United States. Georeferenced lots were identified in Fishnet2 (https://fishnet2.net), a data portal and aggregator for US fish collections.

Figure 3.

The Extended Specimen Network multiplies inferential and explanatory power of stable isotope analysis (SIA), and SIA contributes fundamental insight into community and ecosystem changes that can be integrated with other data inherent to the specimen. The extensions represent changes in scale of inference and additions of other data. Because SIA provides a record of change in units (e.g., delta values, δ) linked explicitly with biogeochemical processes, it can be directly integrated into other hydroclimatic data sets. The primary extension is stable isotope ratios of various elements that can be used to infer ecological processes and the physiological state of the specimen at the time and place of capture. The secondary extension puts isotopic data into the biological context of the population or community. The tertiary extension maps isotopic ratios of organisms, communities, and other biotic and abiotic drivers onto spatial landscapes with a time axis that can span decades.