Data Documentation:Zooplankton Abundance Dataset (ODER~SO Subproject 8 Ecological Functions)

1. Dataset title
Zooplankton abundance across habitats of the Lower Oder River system (November 2023 – December 2025)

2. Context and purpose
This dataset was generated within ODER~SO Subproject 8 (Ecological Function) to quantify spatial and seasonal variation in zooplankton communities across different habitats of the Lower Oder River system. The data provide a basis for assessing the role of zooplankton in regulating phytoplankton dynamics.

3. Sampling design
Study area: Lower Oder River system
•	Habitats: main channel (including groynes, shore, mid-channel), backwaters, floodplain waters
•	Sampling depth: surface water (0–50 cm)
•	Sampling period: November 2023 – December 2025

Sampling frequency:
o	Main channel: approximately monthly
o	Backwaters and floodplain waters: summer season 2024

Number of sites:
o	Main channel: 15
o	Backwaters: 5
o	Floodplain waters: 9

4. Methods summary
Zooplankton samples were collected using standardized filtration methods with plankton nets and analyzed microscopically. Abundance was calculated as individuals per litre (ind/L). Detailed methodology is provided in the README file.

5. Data structure
•	SP08a_Zooplankton_Abundance_2023-2025.csv – zooplankton abundance data (ind/L)
•	Each row represents a single sample. Each taxon is represented as a separate column. Samples are uniquely identified by SAMPLE_CODE.

6. Variables
•	Year: Year of sampling (YYYY)
•	Locality: Sampling area
•	Habitat_ty: Main habitat type
•	Sub_habit: Sub-habitat classification
•	Month: Sampling month
•	Date: Sampling date
•	SAMPLE_CODE: Unique identifier for each sample
•	Remark: Additional notes (e.g., “Not sampled”)
•	Taxon columns: Abundance values (ind/L) for each taxon
•	Detailed variable descriptions, units, and data types are provided in the Data_Dictionary file.

7. Data Processing and values
•	Raw microscope counts were used to calculate abundance (ind/L) based on filtered volume, concentrate volume, counted subsample volume, and dilution factors. 
•	Data were checked for consistency and completeness. 
•	A value of 0 indicates that the taxon was not present in the sample.
•	NA indicates that no data are available, for example when a sample was not collected or could not be analyzed.
8. Quality control
•	Calculations verified
•	Missing or invalid values recorded as NA

9. Taxonomic resolution
Taxonomic identification was performed to species level where possible. For some taxa, identification to species level was not feasible due to morphological similarity and limited diagnostic features.


10. Contact
Abrehet Kahsay Mehari
abrehetkahsay66@gmail.com
Subproject SP8 Ecological functions — ODER~SO

