Environmental and biological data from urban ponds in Brussels

This dataset consists of a single file, “environmental_biological_data_urban_ponds_2021_to_2023.xlsx”, which contains geo-referenced measurements collected in nineteen urban ponds in Brussels, Belgium, between 2021 and 2023. The dataset includes water pH, conductivity (µS cm-1), Secchi depth (m), light attenuation coefficient (m-1), total phytoplankton chlorophyll-a concentration and chlorophyll-a concentrations of the major phytoplankton groups (µg chlorophyll-a L-1). All ponds have pontoons, raised above the water surface, which allow sampling at least 2 m further from the banks. Water pH and conductivity were measured by a VWR MU 6100 H probe 5 cm below the surface. Secchi depth was measured using a Secchi disk. The light attenuation coefficient for photosynthetically available radiation (PAR, 400–700 nm) was estimated from the slope of the semi-log relationship between ln(PARz/PAR₀) and depth (z), using PAR measurements collected in 10 cm increments from the surface to 50 cm depth (when possible), using a Li-Cor LI-250 surface light meter paired with a Li-Cor LI-192 underwater quantum sensor Water was collected in 2L polypropylene bottles for subsequent analysis of chlorophyll-a and other pigments. Filtration on Whatman filters 0.7 µm GF/F glass microfibres with diameter of 47 mm was carried out. Chlorophyll-a concentration and phytoplankton community composition were inferred from algal pigment concentrations, determined by high-performance liquid chromatography (HPLC) coupled with a photodiode-array (PDA) detector and subsequently analysed using CHEMTAX, a chemical taxonomy software. CHEMTAX is a matrix factorization program that relies on concentration matrices of marker pigments, namely chlorophylls and carotenoids (mainly xanthophylls) to estimate the contribution of each specified phytoplankton group to the total chlorophyll-a concentration[1]. Marker pigment extraction and analysis followed the procedure described by Descy[2]. Filters were kept frozen (-18°C) until pigment extraction with 90% v/v acetone. Extraction was followed by filtering through 0.2 µm syringe cartridge. HPLC analysis was carried out using the gradient elution method of Wright et al.[3], with a Waters Alliance System 2695, a Waters 2996 photodiode array detector, and a Waters NovaPak C18 column. Results were processed using Empower software (®2002 Waters Corp.). Chlorophyll-a was used as a proxy of total phytoplankton biomass. References: 1. Mackey, M., Mackey, D., Higgins, H., & Wright, S. (1996). CHEMTAX - a program for estimating class abundances from chemical markers:application to HPLC measurements of phytoplankton. Marine Ecology Progress Series, 144, 265–283. https://doi.org/10.3354/meps144265 2. Descy, J.-P. (2016). Estimation of Cyanobacteria Biomass by Marker Pigment Analysis. In Handbook of Cyanobacterial Monitoring and Cyanotoxin Analysis (pp. 343–349). John Wiley & Sons, Ltd. https://doi.org/10.1002/9781119068761.ch37 3. Wright, S., Jeffrey, S., Mantoura, R., Llewellyn, C., Bjornland, T., Repeta, D., & Welschmeyer, N. (1991). Improved HPLC method for the analysis of chlorophylls and carotenoids from marine phytoplankton. Marine Ecology Progress Series, 77, 183–196. https://doi.org/10.3354/meps077183