Objectives:The objective of the project is to to determine pre-eutrophication aquatic plant communities in Hoveton Great Broad and Hudson’s Bay and to determine seed and oospore viability in the sediments of the two broads
ENSIS met with NE to agree survey/sampling techniques, particularly for zooplankton, as those proposed are either unsuitable for shallow lakes (ECN protocols) or have not been fully documented (EA protocols). The ECN zooplankton method was replaced by tube sampling of whole water columns, with multiple tubes pooled to account for spatial patchiness of zooplankton populations. ECN Phytoplankton sampling methods were also amended to ensure volumetric consistency in these shallow waters. Samples were preserved using alcohol as opposed to the formaldehyde suggested in published protocols.
An initial baseline survey was undertaken in May 2014, and thereafter monthly surveys at the same geo-referenced survey point(s) in each of Hoveton Great Broad and Hudson’s Bay were undertaken, using the same agreed methodologies to ensure consistency of data collection.
Water sampling At each geo-referenced biological sample point, and on each sampling visit, open-water samples were taken
Laboratory analyses Phytoplankton analyses and data enumeration follow the methods of the Environment Agency; zooplankton analysis follow an adaptation of standard techniques.
Light Extinction Co-efficient, pH and redox During field sampling Light Extinction Co-efficient readings were taken at the sample points using a Sky submersible light meter. Further, measurements were made of the pH and redox of the interstitial phase (top 2 cm of sediments). This provided was done to provide valuable information that would give a clearer picture of how zooplankton and sediment surface redox and temperature (a data logger is already in place for those measurements) associate with seasonal variations in Total P and water clarity. It will also allow the depth at which PAR is likely to be beneath that required to sustain or stimulate macrophyte growth to be extrapolated.
The project is still ongoing