SECTIONAL TRANSACTIONS.— B. 323 



being most abundant just below Croft. In the Skerne, sewage fungus is 

 abundant but Cladophora is absent. Tubificid worms and red chironomid 

 larvae occur in quantity in the Skerne, but are found only over a short 

 distance in the Tees. 



Dr. B. A. SouTHGATE. — The effects of sewage and industrial pollution 

 in the Tees estuary. 



The estuary of the Tees receives large quantities of crude sewage and of 

 industrial effluents, mainly in the section from Stockton to Cargo Fleet. 

 The principal industrial effluents are coke-oven effluents containing tar 

 acids, cyanides, etc., and spent pickle liquor, which is an acid solution of 

 iron produced in the cleaning of iron and steel. Oxidation of the sewage 

 and effluents occurs in the estuary at the expense of dissolved oxygen. 

 Large numbers of fish are killed in the estuary, especially salmon and sea- 

 trout smolts during their spring migration to the sea. In 1930 and 1931, 

 the death of migrating smolts was not due to the deficiency of dissolved 

 oxygen, but to cyanides frequently found in lethal concentrations. Other 

 poisonous substances, including tar acids, were not found in toxic concentra- 

 tions, and it has been concluded from numerous chemical and physiological 

 experiments and observations that, in the absence of cyanides, migrating 

 smolts would not have been killed in 1930 and 1931. Laboratory and semi- 

 technical scale experiments have demonstrated that cyanides in coke-oven 

 effluents can be converted into relatively non-toxic ferrocyanide by treat- 

 ment of the effluents with spent pickle liquor and lime. 



Mr. W. B, Alexander. — The effects of pollution on the biology of the 

 Tees estuary. 



There is a scarcity of living organisms in the middle portion of the estuary 

 of the Tees between Stockton and Middlesbrough. This section is subject 

 to the greatest variations in salinity resulting from tidal flow and to the 

 greatest amount of pollution. In addition, organisms living on the banks 

 must be able to withstand exposure to the air for certain periods at low tide, 

 and those living on the bed of the estuary have to withstand the effects of 

 movement of bottom deposits and of sedimentation. It was impossible to 

 determine, therefore, from a biological survey of the estuary of the Tees 

 only, to what extent the flora and fauna are affected by pollution. A survey 

 of the relatively unpolluted estuary of the Tay has shown a distribution of 

 organisms in the section subject to variations in salinity similar, in general, 

 to the distribution in the corresponding section of the Tees, although there 

 are some differences. It thus appears that the scarcity of plant and animal 

 life in the middle portion of the estuary of the Tees is not primarily due to 

 the effects of pollution. 



Mr. R. Bassindale. — The susceptibility of invertebrate animals to 

 poisons. 



Certain animals have a restricted range of distribution in the estuary 

 of the Tees as compared with their range in the relatively unpolluted estuary 

 of the Tay. The effects on these animals of changes in salinity and of the 

 presence of cyanides and tar acids, in concentrations similar to those found 

 in the estuary of the Tees, have been determined. In water of suitable 

 salinities, tar acids at the maximum concentration found in the Tees are 

 not toxic to Neomysis vulgaris, Crangon vulgaris, Gamtnarus marinus, and 

 Corophium volutator. Cyanide at the maximum concentration found in 



