The Norfolk broads include scientific interest sites such as the R. Thurne and Hickling Broad, knowledge of ion chemistry helps management of these sites, for example some macrophytes can use bicarbonate for photosynthesis (Maberly, 2002). Hickling broad, which receives aerial fertilization from black headed gulls (larus ridibundus. L), this increase in phosphorus and the high salinity results in an increase in toxic alga (prymnesium partum) (Moss et al., 1993). Although Hickling broad is far from the main estuary, we found it to have the third highest chlorine levels, this is mainly from percolation from the coast of which it is close to (Moss, 1980).
The sea transfers high levels of sodium chloride into the rivers through tidal currents, as the rivers flow into the sea eastwards there is also a horizontal flow of salt water westwards (Reid, 1961). There is a negative correlation, showing the further from to the sea the lower chlorine concentration, and since the sea contains sodium in equal parts to chloride as NaCL, the levels of sodium ions compared to distance from the sea is also a negative correlation. Moss (1980) shows that rain water contains the same common ions as sea water, captured from sea spray, and in Norfolk due to high evaporation levels on the flat catchment area, rain water can reach the rivers highly concentrated in sodium chloride (Strumm, 2004).
Although the sea provides sodium chloride, it is not a source for all the major ions in the system, carbonate unlike chlorine shows no significantly distinct correlation with distance from the estuary, and this is the same for bicarbonate. Norfolk’s sedimentary rocks give rise to high levels of carbonate in the rivers as acid rain erodes them, through drainage from catchment area, and from run off water (Moss, 1980). A source of limestone (CaMgCo3), increases concentrations of major ions such as calcium and magnesium, which should correlate with carbonate concentrations (Strumm,2004). Carbonate neutralizes the H+ ions (from acidic rain) in the rivers, forming bicarbonate and causing the pH to become more alkaline (Reid, 1961), we measured the pH from several lakes and rivers in the area and found a mean pH of 7.6 + 0.3, this process maintains a neutral pH which is important for reproductive maturation of fish (Vuorien, 2004).
The sea affects the concentration of sodium chloride ions in Norfolk’s open waters, however its contribution of major ions to the overall system is limited by distance from the coast and the estuary, and the ion composition of rain (14+ 3mgl of chloride) also has a major influence. Other major ions such as carbonate, magnesium, and calcium come from the surrounding catchment geology, which provides ions that need constant replenishment due to sediment retention and the flushing of the freshwater system.
Maberly, S.C. (1998) Affinity for Co2 in relation to the ability of freshwater macrophytes to use HCO-3. Functional Ecology.
Moss, B. (1980) Ecology of Fresh Waters. Blackwell Scientific Publications, Oxford, pg 284-289.
Moss, B (1980) Ecology of Fresh Waters Man and Medium, Past to Future. Blackwell Science Ltd, Oxford. 3rd edition, pg 51.
Moss, B., Irvine, K., Bales, M. and Snook, D. (1993) Changing ecosystems of a shallow, Brackish lake, Hickling Broad, Norfolk, U.K.I trophic relationship with special reference to the role of Neomysis Interger. Freshwater Biology, vol. 29. No.1, pg119-139
Reid, K. (1961) Ecology of Inland Waters and Estuaries. Reinhold Publishing Corporation, U.S.A, pg 15, 69-74.
Strumm, W. (2004) The Lakes Handbook Limnology and Limnetic Ecology. Blackwell Science Ltd, Oxford. Chapter 4, pg 82-7.
Vuorien, P.J. (2004) Physiological status of whitefish (coregonus lavaretus pallasi) prior to spawning in lakes of differing acidity. Aquatic sciences, 305-314.
