Water for nitrate (NO3), nitrite (NO2), phosphate (PO4) and silicate (SiO4) was filtered using an acid-washed 60-mL luer-lock syringe combined with an Acrodisc filter (GF/F 0.7 µm). Triplicate samples of filtrate were collected into 15-mL acid-washed polyethylene tubes. Two replicates were kept in the dark at -20°C while the third replicate was poisoned with 24 µL of mercuric chloride and subsequently stored in the dark at 4°C prior to analysis (Hansen & Koroleff, 2007; doi:10.1002/9783527613984.ch10). Nutrient concentrations were determined using an automated colorimetric procedure described in Aminot & Kérouel (2007 (see further details)).

Empty cells = NA