DOI: 10.5061/dryad.8931zcs1v
title: Data from: Effects of salinization on tropical freshwater wetland primary producers and aquatic invertebrates

description: Sea level rise is expected to transform coastal aquatic ecosystems
 worldwide. The freshwater wetlands of tropical northern Australia are
 among the most biodiverse and productive ecosystems on the
 continent, but owing to high regional rates of sea level rise
 coupled with low-lying land and large tides, they are
 increasingly affected by saltwater intrusion. The propagule bank,
 including seeds of aquatic primary producers and eggs of aquatic
 invertebrates, stored in wetland sediment, is vital for
 the establishment of ecological communities, and ultimately for
 primary and secondary production. This experimental study
 examined the impact of increasing salinity on the emergence of
 primary producers and invertebrates from sediment cores collected
 from tropical freshwater wetlands between Darwin and Kakadu
 National Park in Northern Australia. Sediment cores (n=216) were
 placed in microcosms and inundated with one of four salinity
 treatments: 0 ppt (freshwater/control); 7 ppt; 16 ppt, and 35
 ppt (seawater) and decanted on approximately days 10, 20, and 90.
 In comparison to freshwater controls, median chlorophyll a of
 phytoplankton and benthic algae declined sharply with increasing
 salinity, and in the highest salinity treatment, were reduced by
 93% and 60% respectively. Macrophyte biomass, aquatic
 invertebrate density, and richness were reduced to near zero in
 all salinity treatments. Increasing salinity decreases the
 abundance of primary producers and aquatic invertebrates that
 emerge from sediment cores in seasonally inundated tropical freshwater
 wetlands. Macrophyte emergence exhibits no tolerance to
 salinities above freshwater (0 ppt), and aquatic
 invertebrate emergence declines rapidly in both abundance and
 diversity as salinity increases. Our results suggest that
 freshwater aquatic primary producers and aquatic invertebrates
 will be severely impacted by sea level rise and saltwater
 intrusion. Reduced freshwater aquatic primary production
 and aquatic invertebrates may have important implications for
 food webs, and other social and biodiversity values of tropical
 freshwater wetlands.
description: Nine wetlands within three coastal floodplains in the Northern
 Territory, Australia, were sampled in October 2021. Twenty-four sediment
 cores were collected from each of the nine wetlands. The samples were
 collected from around the edge of the wetland’s remaining water while
 avoiding the water’s edge. The cores were collected using an 80 mm PVC
 pipe and trowel to remove the top 30 mm of sediment. Each core was placed
 into an individual 1 L plastic container and stored at room temperature at
 Charles Darwin University and left to dry completely for at least 26 days
 before the commencement of the experiment. The cores from each wetland
 were stored at room temperature 25 °C and exposed to 12 hr light/dark
 cycles of full spectrum double fluorescent lights. The 1 L containers were
 randomly allocated to one of four salinity microcosm treatment groups:
 control/0 ppt (freshwater), 5-10 ppt (approx. 7 ppt), 15-20 ppt (approx.
 16 ppt), and 30-35 ppt (approx. 35ppt) (sea water), resulting in n= 216
 cores broken down into six replicates per treatment per wetland. In
 addition to the treatments, three empty containers without a sediment core
 were included for each of the four treatments (totaling 12 containers), to
 provide a control for potential primary and aquatic invertebrate
 production arising from the saline bore water used to create
 treatments.Treatments were created using reverse osmosis freshwater and
 purified saline bore water which had been modified to represent the
 composition of seawater. The bore water was modified by removing excess
 iron and manganese and supplemented with silicate and potassium. Salinity
 was adjusted to match sea water by addition of KCl and Na₂SiO ₃.
 Each of the 1 L containers with a dry sediment core (n= 216) were
 inundated with the allocated salinity treatment in November 2021 and
 topped up to maintain a water level above the sediment at all times. The
 samples were completely decanted on three occasions at approximately days
 10, 20 and 90 post-inundation. During each decant, all zooplankton and
 other aquatic invertebrates were collected using a 125 µm sieve and stored
 in 50% ethanol for subsequent identification. To measure phytoplankton
 chlorophyll a concentration a 250 ml water column sample was filtered onto
 a filter (47 mm, 0.7 µm pore size Whatman binder free glass microfiber
 filter). Filters were stored in a freezer until analysed with a
 fluorometer. A sample of the benthic algae (chlorophyll a) was collected
 during the final decant using a 32 mm circular felt scrubbing pad attached
 to plywood (Davies and Gee 1993). The felt scrubbing pad was used to
 scrape algae off a 32 mm (diameter) circle of the benthos (Davies and Gee
 1993) and placed into a glass sample jar and stored frozen prior to
 analysis. Phytoplankton and benthic algal chlorophyll a were measured
 using the nonacidification technique for acetone-extracted chlorophyll
 with a Triology®laboratory fluorometer (Turner Designs, Sunnyvale,
 California) (Welschmeyer 1994). All aquatic macrophytes were collected on
 the final decant and were qualitatively separated based on visual
 characteristics at the end of the experiment, but since they did not
 flower or reach mature adult stages it was not possible to identify
 species. The macrophytes were then combined by sample and dried in an oven
 at 60° C for 48 hours, and total dry weight biomass (g) was measured.
 Zooplankton and other invertebrates were counted and identified to family
 or genus level, except ostracods which where were sorted into two
 morphological groups (Ostracoda 1 and Ostracoda 2). This was done, due to
 the lack of a key to juvenile ostracods, to prevent the mixing of
 juveniles and adults of the same taxa into different groups.
description: # Data from: Effects of salinization on tropical freshwater wetland
 primary producers and aquatic invertebrates Dataset DOI:
 [10.5061/dryad.8931zcs1v](https://doi.org/10.5061/dryad.8931zcs1v) ##
 Description of the data and file structure The data consists of three
 files containing the results for zooplankton, macrophytes, and algae. This
 data was collected as part of the inundation salinity experiment using
 sediment cores from one of nine wetlands across three coastal tropical
 floodplains which examined the impacts of increasing salinity on emergence
 of primary producers and aquatic invertebrates at the start of the wet
 season. Files contain sample details, including treatment and
 wetland/catchment, as well as, the biological data of the three biota
 groups.  ### Files and variables #### File: Zooplankton_R_Data_Upload.xlsx
 **Description:** Results of the aquatic invertebrates collected during the
 experiment. ##### Variables * Wetland: Name of wetland sediment cores were
 collected at. * Sample: label from 1 to 24 of sediment cores collected
 from each wetland. * Catchment: Name of catchment wetland is located at. *
 Treatment: A = 0 ppt, B= 7ppt, C = 16 ppt, D= 35 ppt. * Time: 10 = day 10,
 20 = day 20, 30 = day 30. * Zooplankton Richness: Number of different
 invertebrates found. * Total Abundance: Total Number of all invertebrates
 found. * The following columns list the number of invertebrates in each
 group: Collembola, Elimidae, Oribatida, Hydrophilidae, Ostracoda_1,
 Ostracoda_2, Nematoda, Chironomidae, Tipulidae, Trombidiidae, Trichoptera,
 Dytiscidae, Chrysomelidae, Staphylinidae, Chydoridae, Calanidae, Sididae,
 Macrothricidae, Planorbidae, Cyclopidae, Conchostraca, Culicidae,
 Lymnaeidae, Moinidae. #### File: Macrophyte_R_data_Upload.xlsx
 **Description:** Results of the macrophytes collected at the end of the
 experiment. ##### Variables * Wetland: Name of wetland sediment cores were
 collected at. * Sample: label from 1 to 24 of sediment cores collected
 from each wetland. * Floodplain: Name of catchment wetland is located at.
 * Treatment: A = 0 ppt, B= 7ppt, C = 16 ppt, D= 35 ppt. * Day 9, Day 21,
 Day 34, Day 98: States if macrophytes were either present or absent in the
 sample on the stated day. * Species Richness: Number of different
 macrophytes based on simple morphological differences. * Biomass dryweight
 g: The dry weight of the total collected biomass of macrophytes from each
 sample in grams.  #### File: Algae_R_Data_Upload.xlsx
 **Description:** Results of the phytoplankton sampled during the
 experiment and benthic algae collected at the end of the experiment. #####
 Variables * Wetland: Name of wetland sediment cores were collected at. *
 Sample: label from 1 to 24 of sediment cores collected from each wetland.
 * Catchment: Name of catchment wetland is located at. * Treatment: A = 0
 ppt, B= 7ppt, C = 16 ppt, D= 35 ppt. * Time: 10 = day 10, 20 = day 20, 30
 = day 30. * Phytoplankton_Chl_a_ug_L: Phytoplankton density measured in
 the amount of chlorophyll *a* per microgram per L. * Benthic_algae_ug_m2:
 Benthic algae density measured in the amount of chlorophyll *a* per
 microgram per meter squared, sampled only at Time 90. * NA indicates a
 sample in which a variable was not measured. In the benthic_algae_ug_m2
 column this occurred as benthic algae was only measured at Time 90 and not
 at Time 10 or Time 20. #### File:
 Microcosm_Methods_Supplementary_file_Oikos **Description:** Supplementary
 information of the experiment, which gives more context to the data. *
 Figure S1: Google Earth image with pins indicating locations in which
 sediment cores were collected. Acronyms used to indicate each site are
 described in Table S1. Coloured pins indicate wetlands in the same
 floodplain catchment with: blue pins indicating Howard River floodplain
 wetlands; yellow pins indicating Adelaide River floodplain wetlands; and
 red pins indicating Mary River floodplain wetlands. * Figure S2: Graph
 with the climate averages at Darwin airport with is the major city located
 near the floodplains. Based on the Australian Bureau of Meteorology online
 data. Red line = average maximum temperature per month, blue line =
 average minimum temperature per month, grey bars = average rainfall per
 month. * Table S1: Table with the names and locations of wetlands in
 Figure S1. Columns include floodplain, wetland names, longitude and
 latitude, and elevation in relation to MSL (Mean Sea Level).  Elevation
 data obtained from Google Earth (Version 10.61.0.4). * Table S2: Table
 with the mean water quality measured in the field at each wetland site.
 Includes site (wetland name), temperature (measured in degrees Celsius),
 conductivity (measured in millisiemens per centimeter), dissolved oxygen
 (O2) ( measured in milligram per litre), pH, and turbidity (measured in
 NTU (Nephelometric Turbidity Unit)). ## Code/software Files are saved in
 .xlsx format and can be viewed using Excel. The data is formatted for
 analysis in R studio. ## References * Davies, A. L. and J. H. R. Gee.
 (1993). A simple periphyton sampler for algal biomass estimates in
 streams. *Freshwater Biology*, 30:47–51.
 doi:[ doi.org/10.1111/j.1365-2427.1993.tb00787.x ](https://doi.org/10.1111/j.1365-2427.1993.tb00787.x) * Welschmeyer N. A. (1994). Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. *Limnology and Oceanography*, 39(8): 1783-2018. doi: 10.4319/lo.1994.39.8.1985.