Title: Exploratory analysis of seasonal variation of total
phosphorus and lake water temperature in Bosherston Lakes.
No other element
in fresh waters has been studied as intensively as phosphorus (Wetzel,
2001). A very large proportion of
phosphorus, greater than 90% occurs as organic phosphates and cellular
constituents in the biota. (Wetzel, 2001).
phosphorus content of water consists of phosphorus in the particulate and in
dissolved components (Juday,1927; Ohle,1938; Wetzel, 2001).
The Bosherston lakes are artificially
created lake systems located in the Stackpole estate, south-west Wales,
National grid reference 9794. The lakes were formed by progressive flooding of
the three limestone valleys eventually comprising a central body of water
having eastern, central and western arm. The lakes form a part of the Stackpole
Nature Reserve and are owned by the National Trust. The lake system is designated
as a special area of conservation (SAC) under the Habitats Directive as the
Annex I habitat “Hard oligo-mesotrophic waters with benthic vegetation of Chara spp” (CCW report no.858). The lake
water quality depends on the water quality constituents within groundwater and
surface water inflows, internal release from, and deposition of constituents
into lake sediments and the biological uptake of the lakes.
Most of the phosphorus, which arrives in
the lakes, is attached to sediments. A lot of sediment arrives from the
catchment due to the arable and poached grassland. Small amount of sediment is trapped
by the sediment ponds, upstream of the One arch bridge and partly by the
reedbeds (CCW no.858). Majority of it enters the Upper east arm due to the
stormflow. Although, uncertain amounts enter via groundwater from slurry
applications to land. Phosphorus also enters due to internal P cycling within
the internal sediments of the lake and the pond (CCW Contract science report
no.858). This report aims to assess the seasonal variation of 10 year-long
datasets from 2000-2009 of total phosphorus levels in the Stackpole stream
(input stream), Upper east arm, Central arm, Western arm and Central lake and
the effect of climate change by correlating the water temperature with total
phosphorus levels in the lake system.
The dataset available for total phosphorus levels was
sampled across five main sites around the lakes. The Stackpole stream, the
Upper East arm, Central arm, Western arm and the Central lake (Figure2.1).
availability of continuous majority of data and analysing the water quality of
recent past years was the prime reason for choosing the dataset from 2000-2009.
Data representing a value 50ug/l.
of long-term datasets of total phosphorus and the water temperature of the
Bosherston lakes displayed that variations showed clear seasonal trends in the
concentrations. The correlation of water temperature with the total phosphorus
concentrations exhibited majority increase in the phosphorus levels as the lake
temperature increases resulting in higher concentrations during summer. The
Eastern arm is affected the most compared to the other five sites. The results
also demonstrated that future climate change effects would cause major changes
in the water quality of the lakes due to algal bloom. Hence, environmental
bodies should continue their efforts to remove total phosphorus pollution from
the lakes to maintain the necessary ecological standards.
Becks Pond Action Plan DELAWARE DIVISION
OF FISH & WILDLIFE, DNREC
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