The silicate concentrations in the Tamar Estuary show a non-
This reduction of silicate with increased salinity is due to the river acting as
the source of silicate into the ocean. Removal is occurring throughout the estuary
which coincides with the chlorophyll data; showing increased chlorophyll at high
salinities indicating the presence of more phytoplankton. The removal could also
indicate non-
The two graphs are a result of two different methods at collecting data. The auto analysed silicate concentrations were collected using a Quaatro 39 analyser, whereas the blue silicate concentration graph was collected manually.
The anomaly of the 5th sample at a salinity of 8.8 shows an AA silicate sample of
75.30 compared to the manually analysed silicate concentration at the same salinity
of 42.55, this could be due to a sharp increase in silicate being added into the
estuary, for example by an increase in agricultural run-
Silicate
Phosphate
.The phosphate concentrations show non-
The addition seen compared to the TDL is likely caused by phosphate run off in fertilizers found to be in high use in the rural, agriculturally dominated catchment region (Uncles et al., 2002).
A peak in phosphate at around a salinity of 30 is likely to be where the river Lynher
joins the estuary bringing in phosphate rich freshwater with it, again from high
agricultural run-
Similar to the silicon TDLs there is an anomaly at salinity 8.8, station A3 in the upper estuary, which is likely to have been caused by an error when using the Quaatro 39 auto analyser.
Nitrogen
The TDL for nitrate in the Tamar estuary shows mostly conservative behavior throughout the estuary apart from two anomalies at around 23 and 34 salinity. There is very slight negative deviation from the TDL at low salinities but nitrate as a whole is essentially conservative in the estuary, showing simple dilution by sweater at higher salinities (Uncles et al, 2002).
Nitrite displays very strong non-
There is also evidence of a small addition at salinities around 28-
References
A. Morris, A. Bale, R. Howland, 1981. Nutrient distributions in the estuary: Evidence
of chemical precipitation of dissolved silicate and phosphate. Estuarine, Coastal
and Shelf Science. Volume 12, Issue 2, pp 205-
A. Morris, R. Howland, E. Woodward, A. Bale, R. Mantoura, 1985. Nitrite and ammonium
in the Tamar estuary. Netherlands Journal of Sea Research, Volume 19, Issue 3, pp
217-
R. Uncles, A. Fraser, D. Butterfield, P. Johnes, T.Harrod, 2002. The predictions
of nutrients into estuaries and their subsequent behavior: Application to the Tamar
and comparison to the Tweed, U.K. Hydrobiologia, Volume 475, Issue 1, pp239-
The silicate,
nitrogen and phosphate
samples were measured in the
lab manually and using a Quaatro
39 auto analyser and compared to a TDL
in order to show the behaviour of the nutrients throughout the estuary.
All opinions expressed are of our own, and not of the University of Southampton
Figure 1. Silicate change with increasing salinity from water samples in the Tamar
estuary to the Plymouth Sound breakwater. Samples analysed using auto-
Figure 2. Phosphate change with increasing salinity from water samples in the Tamar
estuary to the Plymouth Sound breakwater. Samples analysed with an auto-
Figure 3. Nitrite (top) and Nitrate (bottom) change with increasing salinity from
water samples in the Tamar estuary to the Plymouth Sound breakwater. Samples analysed
with an auto-