Estuarine development was contemporaneous with the onset of glaciation. In the Tay estuary fluvial erosion dominated the downcutting, with minor glacial modification; in the Forth estuary glacial scouring dominated the erosion of rockhead.

Extensive subsurface exploration in connection with road improvement and foundations for bridge building and electricity pylon construction have yielded information on the fill of the Tay and Earn valleys. In addition to geophysical investigations the surveys include boreholes along a 20 km long section from Kinfauns to Longforgan, revealing deposition of lodgement tills followed by Arctic Clays, believed to have been deposited partly from floating ice. Above it are coarse sands and gravels, perhaps outwash deposits. Both were deeply dissected during a fall of sea level associated with a channel cut to − 37 m O.D. at Dundee.

Erosion and marine planation during lowered sea levels produced laterally extensive buried gravels.

A rise of sea level led to burial of the eroded surface by early estuarine sediments which become finer upwards and terminate in peats, dated at 8500 b.p. Further erosion was followed by a second phase of estuarine sedimentation. This produced the carse deposuts whose terminal peats accumulated at 5500 b.p.

The modern estuarial deposits partly bury those of the two preceding estuaries, which exert a major control on the migrations and depth of the modern channels.

The present poor understanding of the fundamental mechanisms of estuarine water movement necessitates an empirical or semi-empirical approach to the circulation problem.

The Tay estuary may be considered as a system for which the inputs consist of phenomena of marine and fluvial origin, and the output is the resultant fluid motion. The definition of the boundaries of the system and of the inputs is explained. The functional dependence of fluid motion is examined with respect to the existing knowledge of estuarine circulation and the economic and technological difficulties associated with prototype estuarine investigations. The results of these studies formed the basis for planning a field study of the Tay estuary.

Data collected during the year 1969-70 has permitted the formulation of empirical relationships between parametric forms of the input and output variables. Thus, to a first approximation, the parameters of estuarine water motion can be predicted for particular antecedent input conditions.

Even a superficial attempt to record the earlier studies on the Firth of Forth brings out the importance of the Royal Society of Edinburgh in supporting research on the underlying principles of estuarine water conditions.

My bibliography starts with the Transactions of that society for 1816, though it is not until 1884, with the studies of H. R. Mill, that we come to work which is really useful to our present purpose. Mill worked from a floating laboratory at Granton Sea Quarry. He carried out twice-daily observations at the Quarry, and systematic observations over a long period at 12 stations in mid-Firth, from Alloa to the Isle of May, and also at several points on the south coast. He reports on variations (largely seasonal) in temperature and on density as an index of salinity, and on the alkalinity of the water. These latter, of course, vary largely with the river inflow, which has a rather imprecise correlation with season.

The Forth Estuary is divided into two parts, the narrow part to the west of Queensferry which is wholly within the area of the Forth River Purification Board and in which there is a substantial tidal variation in salinity, and the broader part to the east of Queensferry which is divided between the Forth and Lothians Boards and is virtually open sea.

There is no record of extensive biological appraisal of the narrow part of the Forth and the quality is assessed largely by general physical and chemical observations. The quality is largely determined by discharge of degradable organic matter in the form of sewage, sewage effluents and trade effluents, the bacterial oxidation of which deoxygenates the water, more or less, according to the combination of fresh water flow, meteorological conditions and the monthly tide cycle. The condition may be aggravated by thermal waste discharge.

In the broader part of the estuary on the north shore, pollution problems are limited to the littoral zone. In a number of places there is local beach pollution from sewage solids but mining pollution in the form of washery slurry pit redd and ferruginous pit waters has extensively affected conditions over a six mile stretch of shore.

The introduction indicates the legal position relative to the control of discharges to the Forth estuary. Details are given of the volumes of the known sources of pollution, in 1958; chemical, bacteriological and biological data then follow relative to a survey carried out in August and September of that year. The conclusions, drawn from the 1958 Survey, emphasised the gross pollution existing at that time, and suggested methods whereby the pollution might be reduced. Section 4 of the paper discusses the results of chemical, biological, bacteriological and hydrographical surveys carried out since 1962. The results stress the deterioration in conditions in the estuary compared with the earlier survey, and in particular, the lower dissolved oxygen concentration in inshore waters and the increase in the Coliform and Escherichia coli counts in certain areas. Isolation of Salmonella species implies the possible health hazards existing at the present time. Work so far carried out in respect of the determination of heavy metal concentrations in core samples taken in the intertidal zone along the shore has indicated relatively high concentrations of certain metals and their effect on the ecology of the estuary has yet to be fully assessed. Float tests made over a period emphasise the tendency for the sewage discharges to be confined to inshore waters, resulting in the gross pollution of certain beaches. Present information stresses the need for the continuance of the monitoring programme.

The most valuable species are Nephrops, salmon, haddock, lobster and sprat. Demersal fish, haddock, whiting, cod, plaice and lemon sole, are mainly taken by seine-netters and light trawlers from 40 to 70 ft overall length. Landings of cod and lemon sole have declined, as has fishing effort. The estuarine environment is especially important for plaice and cod, which spend their early life in coastal waters. Pelagic fish, herring, sprat and mackerel, are unimportant but occasionally pair-trawling for sprats occupies up to 75 boats. Nephrops trawlers, from 40 to 55 ft, fish mainly west of May Island. The Nephrops stocks are heavily exploited. Creel fishing for lobster and crab supports 85 boats. The lobster stocks are intensively fished and landings have decreased. Periwinkles and mussels are gathered but shrimps, though present, are not exploited. Landings of salmon and sea trout, mainly by net and coble from the estuaries, are important chiefly in the Tay. The fisheries have changed dramatically in the past century. Those for herring, oysters and queens have ceased whilst new fisheries have developed for Nephrops and sprat.

Although no particular studies have been made of pollutants in fish of the Forth and Tay estuaries, samples from these areas have been examined together with similar samples from other Scottish coastal waters, as part of a national survey of marine pollution. The contaminants investigated so far have been organochlorine compounds, including pesticide residues and polychlorinated biphenyls, mercury (including organic mercury), lead, cadmium, copper and zinc. Pelagic and demersal fish, molluscs and Crustacea have been sampled, although not all contaminants have been determined in all species.

Few samples have been obtained from the upper sections of the two estuaries, but in comparison with residue levels found in other Scottish waters the species in the two areas contained concentrations little different from those considered to be normal. The selection of species and tissues for analysis, and the problems of interpretation of the analytical data, in terms of locating the sources of pollution and assessing the effects of the pollutants on fish, are discussed. More detailed surveys would be required to identify any localised areas of high contamination.

Two aspects of the relationship between macroalgae and their environment are considered.

Firstly, the serious deterioration of algal populations in the Joppa area is examined, comparing recent studies with those of G. W. Traill, an active phycologist working on the marine algae of the Firth of Forth in the nineteenth century.

The second aspect of the paper is an assessment of the contribution by macroalgae to estuarine ecosystems. The path of photosynthetically fixed carbon through the growing macroalga, and the various ways it enters the water receive particular attention.

The river Tay receives water from an area covering over 2500 square miles of Scotland and has a discharge which is greater than that of the Severn and the Thames combined. It is, in addition, the least polluted of our major British rivers today. It thus provides a composite sample of the waters draining through much of east central Scotland, it provides a baseline for studies on other major British rivers, and with the impending upsurge in industrial activity along the Scottish east coast with the discovery of oil and gas in the North Sea, the importance of having a baseline against which future environmental changes can be measured is now a matter of urgency.