The geology, glaciation, deglaciation and sea level history are summarised in relation to the evolution of the coastline. Deglaciation and sea level are established as particularly important factors responsible for the distribution of sand and shingle beach forelands. Forelands in the middle coastline of the southern shore of the firth are currently undergoing relatively severe coastal erosion. It is argued that this results from a diminution of nearshore sediment supplies combined with a unidirectional longshore movement of material along the beach face.

The nature conservation interest and value of many sites in the Moray Firth are described in their international, national and local contexts. Many man-induced pressures on the natural environment are identified as well as the current mechanisms for nature conservation. The roles of local and national agencies are considered in relation to future strategies for nature conservation within the Moray Firth.

Since the late 1940s coastal planning in the Moray Firth, as elsewhere in Britain, has been carried out by appropriate planning authorities within the framework of the statutory development planning and development control system. In the formulation of plans and policies for the coast, regional and district authorities have responded to national policy guidelines and to the advice received from statutory organisations and others. Controversy and differences have been dealt with by consultation and by local public inquiries.

In safeguarding the coastline, particularly in the inner Moray Firth, planning authorities have had environmental management responsibility for oil and gas-related activities, recreational and tourist facilities, pollution protection and beach erosion. Continuing pressures and uncertainties about future prospects for oil and gas developments have also generated an unusual amount of administrative, survey and research activity at national, regional and district levels. However, the expertise and knowledge gained provide a unique and valuable information base upon which to prepare an overall coastal strategy.

The Moray Firth forms part of the north British coastal area of the North Sea and is distinguished by its depth, hydrography and plankton from the offshore northern North Sea. The 35·0 or 35·1 × 103 isohaline can be taken as the boundary between the two areas.

Geographical and seasonal variations in temperature and salinity are described in terms of a belt of low salinity coastal water in the inner firth and along its southern shore and of “mixed” water to the north and east. During the winter the “mixed” water is warmer than the coastal water, during the summer it is colder. Tidal streams are dominantly semi-diurnal, relatively weak in the inner firth and relatively strong in the outer firth. Residual currents are largely wind driven, and some are caused by tidal effects.

Geographical variation in the seasonal changes in the phytoplankton standing stock is related to water column stratification. The early spring standing stocks are highest in the inner firth and off the southern shore. During the summer and early autumn, phytoplankton is most abundant below the pycnocline. Average zooplankton standing stocks increase from 0·2–0·6 g dry weight (100m3) 1 in winter to 1.0 g (100m3) 1 exceptionally 4·5 g (100m3) 1. in summer. Standing stocks in November–December range from 0·3 to 1·8 g (100m3) 1.

The Moray Firth has been intensively fished for many years and has been of great historic importance to the development of Scottish fisheries. The stocks of exploited species in the firth and their relations to other stocks in Scottish waters are described.

Exploited demersal species include haddock, cod, whiting, plaice and lemon sole. The firth is an important nursery area for plaice, and is the most important plaice spawning ground in the North Sea.

The Moray Firth is also an important nursery area for herring. Evidence suggests that these fish recruit to adult stocks in the Minch. In the early 1960s a pair trawl fishery for sprats started and the firth became the most important sprat fishing area in Scotland. However, recruitment of recent year classes has been too poor to sustain the fishery, which has now been closed in order to protect the juvenile heiring which were landed as by-catch.

The distributions of shellfish species are closely related to the bottom sediments. Landings have become increasingly important as the demersal and pelagic fisheries have declined or moved further offshore. The fishery on the Norway lobster is now of particular importance and the catch per unit effort data do not suggest any decline in stock size. Other exploited species include squid, scallops, crabs and lobster.

Available information on the sizes and locations of seabird breeding colonies in the Moray Firth is reviewed. Guillemot is the most abundant species with a population of about 149,000 individuals at thirteen main colonies. The bulk of the populations of each species occur in east Caithness. Comparison of counts made in 1969 with more recent censuses indicate substantial increases in population size in the 1970s for most species. The results of annual counts at detailed study plots in five Caithness colonies between 1980 and 1984 suggest that this trend of increase has ceased for guillemots, razorbills and kittiwakes.

In 1982 and 1983 monthly shipboard surveys of seabirds at sea were carried out in the Moray Firth. A sea area of about 8.000 knr was studied in a systematic manner using a survey grid of 5λ latitude by 10λ longitude. Guillemot was the most abundant single species for most of the year, but was replaced by herring gull in mid-winter. Numbers of guillemots, razorbills and kittiwakes were all relatively low during the winter period. Total sea bird numbers were greatest in autumn each year, with particularly large concentrations of flightless guillemots and razorbills. A very large influx of razorbills into the Moray Firth was noted in August, 1983. The main offshore concentrations of seabirds through most of the year were over Smith Bank, particularly the northeastern part of the bank. This area was particularly important in spring and autumn for guillemots, razorbills, kittiwakes. gannets and sooty shearwaters, but held relatively few in winter.

Five species of seaduck were counted in the Moray Firth in 1981/82 and 1982/83. Over 20,000 seaducks were recorded each winter, using at least four different main sites. With the exception of long-tailed duck the majority were found within 5 km of the shore. A review of available data showed that the relative importance of each site varied from year to year and it is argued that the whole firth should be considered as a single large site. This site is shown to hold the largest numbers of seaduck in Britain and to be of international importance for three different species. The vulnerability of seaduck flocks to oil pollution in this area may be greater than that of other seabirds.

Surveys of the intertidal macrofauna and sediment characters of Nigg Bay, Moray Firth, were carried out between 1981 and 1985. Permanent stations were located at the intersections of a half-kilometre grid covering the entire intertidal area and sampled for infauna, using replicate cores. Estimates were also made of mussel and lugworm densities from quadrats and cast counts respectively. The biomasses of selected species that constitute important resources for higher trophic levels were also estimated. The sediment for each station was analysed for median particle diameter and silt content.

The infaunal data were analysed by Detrended Correspondence Analysis. This indicated that tidal height was the most important factor governing the distribution and abundance of the intertidal communities. Sediment characters were only poorly related to distribution patterns.

The bay has a rich fauna and is biologically similar to other outer bays of the Moray Firth, which, like Nigg, are important areas for wildfowl and waders. Comparisons of survey data from different years indicate that there are natural cycles in some sediment and biological characters of Nigg Bay.

The shorebird populations of the Moray Firth mudflats were studied between 1981 and 1985. Peak numbers of waders were found in midwinter when the total population may exceed 36,000 birds. More than 1% of the total northwest European population of oystercatchers (Haematopus osiralegus), redshank (Tringa totanus), bar-tailed godwit (Limosa tapponica) and knot (Calidris canutus) were recorded. Wildfowl reach peak numbers in October and November (approximately 45,000); numbers decline gradually thereafter as some birds move on to wintering sites elsewhere in Britain. Ringing and colour-marking studies showed that turnstone (Arenaria interpres), curlew (Numenius arquata), ringed plover (Charadrius hialicula), oystercatcher and redshank remained loyal to selected feeding areas within the Moray Firth while bar-tailed godwit, knot and dunlin (Calidris alpina) ranged widely throughout the winter.

These observations are discussed in relation to the value of the Moray Firth to shorebirds and the problems posed by the reclamation of intertidal habitats and pollution of the intertidal areas.

An intertidal rocky shore monitoring programme was established in 1981 as part of the Beatrice Environmental Programme covering thirty-four different locations in the Moray Firth between Duncansby Head and Fraserburgh. This paper describes the survey methods, the species found and the rocky shore communities encountered on these shores. During the development of the Beatrice Oil Field a new shore line was created in the Cromarty Firth at the Nigg terminal and the successional changes in the communities on this shore between 1981 and 1984 are discussed.

The littoral macrobenthic fauna of soft shores at three sites in the Cromarty Firth, two sites in the Dornoch Firth and seven sites in the Inverness Firth (northeast Scotland) was studied in 1982 and 1983 respectively.

At each site ten replicate samples were taken from each of three stations at 0·65, 1·15 and 1·7 m above Chart Datum. Estimation of environmental disturbance caused by the Inverness sewage discharge and a comparison of the three firths was made using both diversity indices and multivariate techniques.

Fouling communities typical of shallow water inshore sites were found at three locations in the Moray Firth. At each, an initial background cover of solitary tubeworms and barnacles was overgrown by secondary fouling organisms. On the piles of Nigg jetty, overgrowth consisted of mussels in the depth range 0–6 m and hydroids, sponges, soft corals and anemones from 6–26 m. Buoys in the approaches to Cromarty Firth were completely covered by a mixture of algae and mussels. Sunlit areas of the float cleaned annually bore a diverse algal cover, whereas uncleaned shaded areas and the freely hanging chain had three-year-old mussels up to 7 cm long. Mussel fouling extended down the chain to within 1 m of the seabed at 26 m depth. Concrete anchor blocks on the seabed were covered with solitary tubeworms and hydroids. Steel piled platforms in the Beatrice Field were completely fouled after four years. Mussels and seaweeds were abundant from 0–5 m. In the depth range 8–35 m the background calcareous layer was overgrown by soft corals up to 10 cm long and hydroids. From 35 m to the seabed at 46 m, soft overgrowth was provided mainly by hydroids and ascidians, with only a few small corals.

The benthic ecology of the Beatrice Oilfield area is described from preproduction surveys carried out in 1977, 1980 and 1981. and from earlier published information. Variations in the water depth (from 33m to > 60 m) over the area were mirrored by sedimentary and faunal gradients. The sediments ranged from very fine, through fine to medium sands and were inhabited by faunal communities characterised by Thyasira flexuosa, Tellina fabula and Tellina pygmaea, respectively. Two fades of the fine sand community were noted, typified by the abundance of Thyasira flexuosa in muddier sediments and Crenella decussala in coarser deposits. Localised patches of shell gravel in which the fauna was characterised by reduced densities of Tellina fabula with elevated numbers of Scoloplos armiger and Lumbrineris gracilis occurred in medium depths. Examination of the faunal composition indicates that the Beatrice Oilfield lies at the interface between Glemarec's infralittoral and coastal étages.

Comparison with earlier reports of the benthic communities of the area suggests a degree of long term persistence of the fauna in qualitative and quantitative terms. A list of all taxa found during the recent surveys is given; this includes a number of new records from the North Sea.

The identity and abundance of animals passing through a 1·0 mm mesh but retained on a 0·5 mm mesh is detailed for a number of seabed samples of medium, fine and very fine sand taken in the Beatrice Oilfield in 1981. Comparisons are made with the corresponding 1·0mm-sieved fractions, and the effects on community parameters of combining the two data sets are considered.

In general fewer animals were found on the 0·5 mm mesh than on the 1·0 mm mesh above it. The 0·5 mm mesh samples added comparatively few taxa to the faunal list of the survey. The quantitatively-scored taxa from the 0·5 mm mesh were therefore essentially a sub-set of those already recorded on the 1·0 mm mesh. Several taxa of Foraminiferida were found only on the 0·5 mm mesh, and one of these appeared to be relatively abundant. However. Foraminiferida were not scored quantitatively in this study.

In all samples, when 0·5 mm and 1·0 mm data were combined an increase was noted in the number of taxa recorded compared with 1·0 mm data alone. This recruitment of taxa was largely a reflection of the greater number of individuals in the combined data, rather than the inclusion of taxa unique to the 0·5 mm material. Similarly, the improved precision of abundance estimates of dominant taxa in replicate samples in the combined data probably resulted from the greater number of individuals included in the analysis.

It is argued that the choice of a particular mesh size imposes an essentially arbitrary cut-off along the size spectrum of benthic organisms. A 1·0 mm mesh has been found to yield adequate data in a number of offshore surveys undertaken by the Oil Pollution Research Unit (OPRU). Although a greater number of animals per sample is collected by sieving on a 0·5 mm mesh, the time taken to extract and identify this material must be considered. The alternative of spending an equivalent time analysing extra 1·0 mm samples may in fact yield a greater increase in confidence in the results.

The sub-littoral fauna at eight stations in the Beauly and Inverness Firths, six stations in the Cromarty Firth and eight sites in the Dornoch Firth have been sampled and identified. The main components and trends in the fauna of the three firths are described. The three firths are compared in terms of their fauna and the reasons for differences suggested.

Oil pollution incidents in the inshore Moray Firth 1975–84 and Cromarty Firth 1970–84 are reviewed, describing the levels, geographical patterns, trends and some impacts.

Growth in oil-related activity in the inshore Moray and Cromarty Firths has not led to increased levels of oil pollution. In the Cromarty Firth the majority of incidents since 1970 have been from long-established shore-based sources, while the frequency of incidents and their impact have diminished over the last few years from levels in the early-raid 1970s which were very unsatisfactory. Incident levels in the inshore Moray Firth have also reduced since 1980.

While no major environmental damage has resulted from oil pollution in this area, important wildlife resources, and in particular bird populations, have been shown in individual incidents to be extremely vulnerable to relatively small quantities of oil. It is thus important that continued attention is given to the prevention and treatment of oil pollution in this area and the strict procedures pertaining to oil exploration and production and operation of marine traffic should be maintained.

The most pertinent sources of pollution in the Moray Firth are considered to be direct discharges of sewage and trade effluents and indirect discharges of trade effluent through public sewers; discharges to underground strata; the deposit of waste on land and at sea, and oil discharge from shore and offshore installations and vessels. The distribution of the main function and responsibilities for the administrative control of pollution and the concomitant statutory powers are explained under the relevant sources of pollution identified.

This paper describes environmental monitoring which has been carried out in the Moray Firth. Three areas of potential impact have been examined; the cryolite recovery sludge dumping ground in the inner Moray Firth, the Beatrice Oilfield, and the Nigg oil terminal. The monitoring objectives are described, some results are presented, and the scale of effects compared. In each case the effects are very localised and there was no evidence of any potential threat to fisheries.