IMIS

This dataset contains time-series of environmental and zooplankton data from the estuary of Urdaibai and from the estuary of Bilbao since 1998. Data are obtained from monthly sampling at high tide during neap tides at the 30 salinity zone. Zooplankton are collected from below the halocline by 2 to 3 min horizontal tows using a 200 µm mesh size net (mouth diameter 0.25 m) equipped with a Digital Flowmeter, preserved in 4% buffered formalin and identified and counted under a stereomicroscope. Vertical profiles of water temperature, salinity and dissolved oxygen are measured in situ using WTW Water Quality Meters. Water samples are collected also at the depth of zooplankton sampling using a Niskin bottle for measuring chlorophyll a, which is analysed spectrophotometrically in triplicate samples according to the monochromatic method with acidification. Secchi disk depths are also recorded.