Data from: The key role of nitrogen in boosting algal growth in Arctic rivers
Data files
May 30, 2025 version files 61.07 KB
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NDS_data_Huttunen_et_al_rev2.xlsx
56.03 KB
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README.md
5.04 KB
Abstract
Increasing nutrient loads are impairing water quality and the ecological status of aquatic ecosystems globally, but their effects on Arctic freshwaters remain less studied. Nutrients in Arctic freshwaters are increasing due to expanding anthropogenic land use and climate change induced alterations in nutrient leaching and transport. Also, increased occurrences of non-native semelparous Pacific pink salmon (Oncorhynchus gorbuscha) in the northern European rivers can enhance nutrient availability. These additional nutrients may be readily available for aquatic primary producers in often inherently (ultra-)oligotrophic Arctic freshwaters. We used an experimental field set-up with nutrient diffusing substrates to study temporal and spatial differences in the response of primary producers to increased phosphorus (P) and nitrogen (N) levels in Arctic rivers. Additional NO3-N enhanced algal growth (chlorophyll-a (Chl-a) amount) of epilithic biofilm. PO4-P alone had no effect, indicating N as the primary limiting factor for algal growth. This was particularly evident in autumn, while early summer showed evidence for secondary P limitation. The response to nutrient additions was mostly dictated by the background availability of inorganic N. Our results suggest that Arctic rivers are highly sensitive to nutrient additions, especially N. Thus, any increase in nutrients can boost algal growth, causing cascading effects throughout Arctic ecosystems.
https://cdnsciencepub.com/doi/full/10.1139/as-2024-0074
Description of the data and file structure
Use of nutrient diffusing substrates to study the reactivity of epilithic algae to additional nutrients across a network of various-sized Arctic rivers at the two extremes of a growing season: early summer and autumn.
Files and variables
File: NDS_data_Huttunen_et_al_rev2.xlsx
Description: The xlsx-file includes four sheets i) the measured (non-transformed) Chl-a values as total amounts and as daily values; ii) location of the study sites; iii) incubation periods; and iv) environmental data.
Sheet 1 (Chl-a values)
- Includes the values for the response variables. Chl-a values are given for each replicate (block) separately.
- Sample = sample code including information for site, treatment and block
- Treatment = C (control), N (nitrogen), P (phosphorus), NP (nitrogen & phosphorus)
- Season = indicates the season (Early summer vs. Autumn)
- Area = defines the geographic area, from each area we sampled one small, one intermediate and one large river
- Site = defines the study river
- Size = defines the size of the study river based on Strahler stream order (1 = small, 3 = intermediate, 5-6 = large)
- Block = defines the within-site replicates (4 for each treatment / site / season)
- chl_a_total = total amount of Chl-a (μg/cm2) in a sample
- chl_a_per_day = daily amount of Chl-a (μg/cm2/day) in a sample, i.e., total Chl-a divided by the number of incubation days
Sheet 2 (Location)
- Gives information on the location of the study sites
- River_name = full name of the study river
- Area (see above)
- Site (see above)
- Size (see above)
- N = latitude (ETRS TM35)
- E = longitude (ETRS TM35)
Sheet 3 (Incubation days)
- Gives information on the timing and duration of the study
- Site (see above)
- Season (see above)
- Start_date = the date of commencement of the treatments (dd.m.yyyy)
- End_date = the date of closing the treatments (dd.m.yyyy)
- Number_of_full_days = the number of full days for the incubation (used to calculate chl_a_per_day on Sheet 1)
Sheet 4 (Environmental data)
- Gives information on the explanatory / descriptive variables
- River_name (see above)
- Size (see above)
- Site (see above)
- Catchment_area_km2 = size of the catchment area (km^2)
- Urban_and_agricultural_areas_% = cover of urban and agricultural area within the catchment area (%)
- Simpsons_substrate_diversity = the value for Simpson's substrate diversity used to describe the heterogeneity of the substrate (range 0-1; high values indicate high heterogeneity)
- Bryophyte_cover_% = average percentage cover of stream bryophytes (%)
- Stream_velocity_ms = average stream velocity measured as meters per second (m/s)
- Scrapers_% = percentage of invertebrates defined as scrapers regarding their feeding habits (%)
- Collector_gatherers_% = percentage of invertebrates defined as collector-gatherers regarding their feeding habits (%)
- Water_temperature_C_summer = average water temperature (°C) during the early summer sampling period
- Water_temperature_C_autumn = average water temperature (°C) during the autumn sampling period
- Light_intensity_lux_summer = average light intensity (lux) during the early summer sampling period
- Light_intensity_lux_autumn = average light intensity (lux) during the early summer sampling period
- pH_summer = pH value in the water chemistry analysis for the early summer samples
- pH_autumn = pH value in the water chemistry analysis for the autumn samples
- PO4_ugL_summer = PO4 (phosphate, ug/L) value in the water chemistry analysis for the early summer samples
- PO4_ugL_autumn = PO4 (phosphate, ug/L) value in the water chemistry analysis for the autumn samples
- DIN_ugL_summer = DIN (dissolved inorganic nitrogen, i.e. NO2+ NO3+NH4, ug/L) value in the water chemistry analysis for the early summer samples
- DIN_ugL_autumn = DIN (dissolved inorganic nitrogen, i.e. NO2+ NO3+NH4, ug/L) value in the water chemistry analysis for the autumn samples
Code/software
saved as an Excel file with four separate sheets: i) chl-a data; ii) location of the study sites; iii) incubation periods; and iv) environmental data
Access information
Data was derived from the following source: Collected from the field by the authors
The study was conducted within the Teno River catchment in northern Finland. In total, 18 spatially independent study sites were selected from the catchment area based on their location and size (1st, 3rd and 5-6th order). We used Nutrient Diffusing Substrates (NDS) to test the reactivity of epilithic algal communities to additional nutrients and, consequently, to identify the resources limiting algal productivity. The experiment was conducted in 2022 and replicated at the same study sites twice: June-July and August-September. NDS were prepared following the instructions by Tank et al. (2006; Methods in Stream Ecology. Elsevier, pp. 213-238) with minor adjustments. Sets of NDS cups (each treatment replicated four times) were incubated in the rivers for 23 – 26 and 25 – 29 days in early summer (13.6.-13.7.2022) and autumn (15.8.-16.9.2022), respectively. After each incubation period tiles were removed from the NDS cups and stored in a dark cold box until freezing to -20°C within the same day. To obtain chl-a from the tiles we used acetone extraction following closely the protocol presented in Steinman et al. (2017; Methods in Stream Ecology. Elsevier, pp. 223–241). Extraction was done separately for each tile resulting in four replicates per treatment per site and per time.