DOI: 10.5061/dryad.dfn2z353f
title: Measurements in flowing freshwater ecosystems taken in Ohio (US)

description: Knowledge of ecological responses to changes in the environment is vital
 to design appropriate measures for conserving biodiversity. Experimental
 studies are the standard to identify ecological cause-effect
 relationships, but their results do not necessarily translate to field
 situations. Deriving ecological cause-effect relationships from
 observational field data is, however, challenging due to potential
 confounding influences of unmeasured variables. Here, we present a causal
 discovery algorithm designed to reveal ecological relationships in rivers
 and streams from observational data. Our algorithm (a) takes into account
 the spatial structure of the river network, (b) reveals the complete
 network of ecological relationships, and (c) shows the directions of these
 relationships. We apply our algorithm to data collected in the US state of
 Ohio to better understand causes of reductions in fish and invertebrate
 community integrity. We found that nitrogen is a key variable underlying
 fish and invertebrate community integrity in Ohio, likely negatively
 impacting both. We also found that fish and community integrity are each
 linked to one physical habitat quality variable. Our algorithm further
 revealed a split between physical habitat quality and water quality
 variables, indicating that causal relations between these groups of
 variables are likely absent. Our approach is able to reveal networks of
 ecological relationships in rivers and streams based on observational
 data, without the need to formulate a priori hypotheses. This is an asset
 particularly for diagnostic assessments of the ecological state and
 potential causes of biodiversity impairment in rivers and streams.
description: This dataset covers the ecological integrity of fish and
 invertebrate assemblages in rivers in Ohio, based on a dataset covering
 measurements at 1,826 biomonitoring sites sampled between 2000 and
 2007. The integrity of the fish community is captured by the Index of
 Biotic Integrity (IBI). The IBI is constructed by comparing the fish
 community at a given site to an undisturbed reference community, located
 in a river of similar size and in a similar region. Reference communities
 are obtained from sites with minimal human influence based on expert
 judgment. The IBI is composed of 12 sub-metrics indicative of various
 aspects of community integrity, including the total number of species,
 number of individuals, and the proportion of top predators, with each
 sub-metric getting a score of 1, 3, or 5. A low score represents a high
 deviation from the reference site (Fausch et al., 1984). Similarly, the
 Invertebrate Community Index (ICI) combines 10 sub-metrics including the
 total number of taxa and the percentage of tolerant organisms in
 comparison to a reference community. For the ICI, the possible scores for
 each sub-metric are 0, 2, 4, or 6. The IBI ranges from 12 to 60
 whereas the ICI ranges from 0 to 60. Fausch, K. D.,
 Karr, J. R., and Yant, P. R. (1984). Regional application of an index of
 biotic integrity based on stream fish communities. Trans. Am. Fish. Soc.
 113, 39–55. doi:
 10.1577/1548-86591984113&lt;39:RAOAIO&lt;2.0.CO;2
description: Missing values indicate missing measurements. Variable names are
 explained in the readme file and in Mielke et al. (2021). The dataset is
 further described by Zijp et al. (2017). Mielke, K. P.
 , Schipper, A.M., Heskes, T., Zijp, M.C., Posthuma, L., Huijbregts,
 M.A.J., and Claassen, T. (2021). Discovering Ecological Relationships in
 Flowing Freshwater Ecosystems. Front. Ecol. Evol. 9:782554. doi:
 10.3389/fevo.2021.782554 Zijp, M. C., Huijbregts, M. A.
 J., Schipper, A. M., Mulder, C., and Posthuma, L. (2017). Identification
 and ranking of environmental threats with ecosystem vulnerability
 distributions. Sci. Rep. 7:9298. doi: 10.1038/s41598-017-09573-8