DOI: 10.5061/dryad.41ns1rnk1
title: Data from: Substantial pulses of aquatic insects emerge from tidal freshwaters along the James River Estuary, Virginia, USA

description: Tidal freshwaters in upper estuarine reaches provide important ecosystem
 services but are threatened by relative sea-level rise and
 pollution from increased development. Tidal freshwaters are
 highly productive and support estuarine and riparian food webs alike.
 Aquatic insects are common prey subsidies crossing into riparian
 habitats; however, the magnitude, timing, and composition of
 insect emergence in tidal systems has received little attention.
 Our objective was to better understand the magnitude and
 variability of aquatic insect emergence in tidal freshwaters. To
 do so, we quantified insect emergence from tidal creeks and
 estuarine shorelines of the James Estuary, Virginia, USA, and
 characterized spatial and temporal patterns in the amount of
 emergent biomass. We continuously monitored insect emergence from 7
 April to 8 November 2019 with floating emergence traps to
 estimate daily emergence, then used generalized additive mixed
 models to analyze spatial and temporal variation in daily
 emergence rates. We estimated aquatic insect biomass to emerge at
 a mean rate (±1 SE) of 15.6 ± 2.0 g dry mass m −2 y −1, which is
 among the highest of previously published estimates from nontidal systems
 (mean ±1 SE = 12.9 ± 6.2 g dry mass m −2 y −1 ). Spatial variability in
 emergence was highly taxon specific. Diptera and Trichoptera had
 more biomass emerging from the subtidal than intertidal zone,
 Odonata biomass emerged more from tidal creeks than along the
 estuarine shoreline, and the amount of Trichoptera biomass
 increased, whereas Ephemeroptera decreased, with distance from
 the estuarine shoreline. The magnitude and composition of emergent
 taxa varied throughout the sampling period, with sequential peaks
 in biomass that altered the prey available to riparian consumers.
 Our results suggest that tidal freshwaters export
 substantial quantities of aquatic insects, which are valuable
 prey items for riparian consumers in these systems.
description: At each site, we placed 4 emergence traps along the estuarine
 shoreline near the creek–estuary confluence (hereafter, shoreline) and 9
 traps longitudinally along the creek, reaching 1050 to 1540 m from the
 confluence. We positioned all traps within 3 m of the shore (creek or
 estuarine) at high tide. Variation in water depth resulted in some traps
 resting on exposed substrate at low tide (intertidal), whereas others
 always remained over water (subtidal). Additionally, variation in
 streambank slope resulted in different tidal zone sampling patterns
 between sites. At Deep Bottom, we sampled Bailey Creek primarily in the
 subtidal zone and the shoreline primarily in the intertidal zone. At the
 Rice Center, we sampled Kimages Creek primarily in the intertidal zone and
 the shoreline primarily in the subtidal zone. We
 continuously monitored aquatic insect emergence from 7 April to 8 November
 2019, capturing all emergence events within the sampling period. We
 constructed floating emergence traps following Cadmus et al. (2016) with a
 few modifications to increase stability and allow for continuous field
 placement in a tidal system. We used white no-see-um mosquito netting
 (30.5g/m<sup>2</sup> ; Ripstop by the Roll, Durham, North
 Carolina) to capture small-bodied insects and reduce shading by the trap,
 which has been found to cause insect avoidance (Davies 1984). We tethered
 each trap to a 3-m metal conduit pole driven into the sediment to limit
 drift but allow for vertical movement with tidal changes. Traps covered a
 basal area of 0.4 m<sup>2</sup> and included a collection
 bottle containing 50 to 100 mL of 70% isopropanol to preserve insects
 between field collections. We accessed traps by canoe at high tide every 3
 to 7 d (mean ±1 SD: 5.1 ± 1.7 d) to collect samples, which is within the
 range of collection intervals from other studies (e.g., Whiles and
 Goldowitz 2001, Martin Creuzberg et al. 2017). To collect the most
 accurate estimate for large-bodied taxa known to avoid emergence traps
 (MacKenzie and Kaster 2004), we added to the sample large bodied insects
 (i.e., Odonata, Ephemeroptera) that were found within the trap net but not
 yet in the collection bottle. We stored samples in 70% isopropanol until
 processing, which began after the 1 st collection event and continued
 through August 2020. We identified the following
 insects to order or suborder: mayflies (Ephemeroptera, suborders
 Schistonota and Pannota), stoneflies (Plecoptera), caddisflies
 (Trichoptera), dragonflies and damselflies (Odonata, suborders Anisoptera
 and Zygoptera), and aquatic flies (Diptera, suborder Nematocera) based on
 diagnostic morphological features (Thorp and Covich 2001). We recorded the
 number of individuals in each order or suborder, dried the insects for 48
 h at 60°C in a drying oven, then recorded dry mass (DM) to the nearest 0.1
 mg for each sample after equilibration to room temperature. For samples
 containing many dipterans (&gt;200 ind.; 47% of samples), we counted a
 representative sample of 100 ind. and pooled the remaining insects. We
 used the DM of the representative sample and the remaining pooled insects
 to estimate the total number of dipterans in the sample. We then
 standardized emergent DM and density estimates from each sample and taxon
 m<sup>–2</sup> d<sup>–1</sup> based on trap area
 and collection interval (mg DM m<sup>−2</sup>
 d<sup>−1</sup> and ind. m<sup>−2
 </sup>d<sup>−1</sup> ).
description: # Data from: Substantial pulses of aquatic insects emerge from tidal
 freshwaters along the James River Estuary, Virginia, USA
 The dataset
 *emergenceDataProcessed.csv* includes standardized biomass and density
 estimates (m-2 d-1) for each emergent insect taxon collected during the
 sampling period, as well as covariates used in downstream modeling of
 insect emergence rates, organized by sample collection (CollectionID). The
 dataset *emergenceData_daily.csv* expands standardized biomass and density
 estimates (m-2 d-1) to include each emergent insect taxon on each day at
 each trap during the sampling period, as well as covariates used in
 downstream modeling of insect emergence rates. Daily estimates can be
 summed to obtain emergence estimates over longer time periods (e.g.,
 annual estimates, peak emergence estimates). This dataset is created from
 emergenceDataProcessed.csv and is the input dataset for insect emergence
 models. ## Description of the data and file structure ######
 *emergenceDataProcessed.csv* Each **CollectionID** (specified as
 TrapID_CollectionDate) has 7 records, corresponding to the taxa collection
 during this study. **Taxa** is one of 7 taxa identified:
 Diptera_Nematocera, Ephemeroptera_Pannota, Ephemeroptera_Schistonota,
 Odonata_Anisoptera, Odonata_Zygoptera, Plecoptera, or Trichoptera.
 **TrapID** includes site and trap number. Each site had 13 emergence
 traps. **StartDateTime** refers to the date and time of trap/sample
 deployment and is usually the same as the previous collection EndDateTime.
 Exceptions occur for new trap deployments following instances of missing
 or damaged traps. StartDateTime == NA if a new trap was deployed for a
 CollectionID (i.e., trap was not in place during previous collection
 period). **EndDateTime** refers to the date and time of sample collection.
 Date matches the the CollectionDate in CollectionID. EndDateTime == NA if
 trap was missing or sample was unusable (e.g., filled with river water,
 insects not well preserved) for a particular CollectionID. **Duration** in
 days for a sample collection, calculated using EndDateTime -
 StartDateTime. Duration == NA if either StartDateTime or EndDateTime is
 missing. **Site** of trap location is Deep Bottom Park (DB) or Rice Rivers
 Center (RC). **Latitude** of trap location in decimal degrees.
 **Longitude** of trap location in decimal degrees. **Inundation** refers
 to whether the trap rested on sediment at low tide (Intertidal) or was
 always over water (Subtidal). **Placement** refers to whether the trap was
 located at the confluence of the creek and estuarine shoreline
 (Confluence) or at a point along the tidal creek (Creek). **Distance_10m**
 is the distance to the nearest 10m of the trap to the confluence with the
 estuarine shoreline. Distance was estimated on ArcGIS Pro and was measured
 along stream length. Traps with Placement == Confluence have Distance_10m
 == 0. **BiomassSqmDay** is the standardized biomass estimate (m-2 d-1) for
 a collection. If a taxon was not collected in a valid sample (i.e.,
 emergent insects were absent in sample), the the corresponding
 BiomassSqmDay == 0. If there was not a valid sample for a taxon (i.e.,
 sample compromised, missing data), the corresponding BiomassSqmDay == -1.
 **CountSqmDay** is the standardized density estimate (m-2 d-1) for a
 collection. If a taxon was not collected in a valid sample (i.e., emergent
 insects were absent in sample), the the corresponding CountSqmDay == 0. If
 there was not a valid sample for a taxon (i.e., sample compromised,
 missing data), the corresponding CountSqmDay == -1. ###### ######
 *emergenceData\_daily.csv* **Taxa** is one of 7 taxa identified:
 Diptera_Nematocera, Ephemeroptera_Pannota, Ephemeroptera_Schistonota,
 Odonata_Anisoptera, Odonata_Zygoptera, Plecoptera, or Trichoptera.
 **TrapID** includes site and trap number. Each site had 13 emergence
 traps. **Site** of trap location is Deep Bottom Park (DB) or Rice Rivers
 Center (RC). **Inundation** refers to whether the trap rested on sediment
 at low tide (Intertidal) or was always over water (Subtidal).
 **Placement** refers to whether the trap was located at the confluence of
 the creek and estuarine shoreline (Confluence) or at a point along the
 tidal creek (Creek). **Distance_10m** is the distance to the nearest 10m
 of the trap to the confluence with the estuarine shoreline. Distance was
 estimated on ArcGIS Pro and was measured along stream length. Traps with
 Placement == Confluence have Distance_10m == 0. **BiomassSqmDay** is the
 standardized biomass estimate (m-2 d-1) for a specific day. If a taxon was
 not collected in a valid sample (i.e., emergent insects were absent in
 sample), the the corresponding BiomassSqmDay == 0. If there was not a
 valid sample for a taxon (i.e., sample compromised, missing data), the
 corresponding BiomassSqmDay == NA. **CountSqmDay** is the standardized
 density estimate (m-2 d-1) for a specific day. If a taxon was not
 collected in a valid sample (i.e., emergent insects were absent in
 sample), the the corresponding CountSqmDay == 0. If there was not a valid
 sample for a taxon (i.e., sample compromised, missing data), the
 corresponding CountSqmDay == NA. **endDate** is the date that the
 estimated emergence occurred (YYYY-MM-DD). Each date within the sampling
 period (2019-04-07 to 2019-11-08) is included.