Martin Wilkinson

Distribution of attached algae in estuaries

Abstract Preliminary studies on distributions of attached algae in British estuaries suggest that the estuaries might be classified on the basis of the flora in the upper reaches. This could contribute to biological assessment of water quality in estuaries.

Geographical variation in the distributions of macroalgae in estuaries

Assemblages of macroalgal species present in the upper reaches of estuaries were compared using published species lists for the North Atlantic, covering a north-south gradient in Europe from Iceland to northern Spain, and in North America between the St. Lawrence and Virginia. Patterns were sought using cluster analysis and ordination. Three groupings of estuaries were noted: Icelandic, mainland European and American. There was a slight trend of increase in the ratio of red to brown algae with decreasing latitude in Europe, though not as marked as for open coastal algae. This might be associated with the effect of temperature on salinity tolerance. Despite this biogeographic trend, some of the commonest species appear to be widely spread through estuaries, possibly including southern Atlantic and Pacific locations. Confirmation of the trends suggested requires further data from southern European estuaries.

Intertidal organisms of an industrialized estuary

Abstract A study of the intertidal organisms of the Clyde Estuary is being undertaken to assess the effects of changing levels of pollution and to relate to these and other changes the distribution of important winter flocks of waders and ducks.

Survival Strategies of Attached Algae in Estuaries

There is little published evidence concerning the mechanisms of survival of attached algae in estuaries. At the cellular level, studies on osmotic and ionic regulation in algae have largely been directed at using the algae as convenient tools for the investigation of physiological processes rather than at using physiological differences between algae to explain differences in their distributions. At the whole plant level, while many workers have investigated environmental tolerances of algae in batch culture, results have sometimes been contradictory and difficult to relate to observed field distributions. This has resulted in some cases from inadequacies in the design of such experiments. A comprehensive review of the literature concerning the distribution of estuarine algae in relation to environmental factors has been given by Wilkinson (1980). It is not proposed to repeat this review but instead to highlight several promising approaches, worthy of further investigation, to explain the survival of estuarine algae. These include the simultaneous adoption of more than one strategy, the existence of subspecific variants in widely distributed species and the growth patterns of the algae themselves.

Environmental tolerance of the estuarine diatom Melosiranummuloides (Dillw.) Ag

Abstract Growth rate in culture of three isolates of Melosira nummuloides (Dillw.) Ag. from the Clyde Estuary was uniform over the salinity range 5–34%. although there was no growth in freshwater medium (0.5%.). Plants maintained at 0.5%. for up to 8 days suspended growth and it was resumed on transfer back to a higher salinity. The low light saturation point for growth (37 μE·m−2·s−1) would enable growth to occur at the low light intensity found in a turbid estuary. Large salinity fluctuations (5–23%.) had little effect on the net rate of photosynthesis. These features are adaptive to the estuarine environment but cannot alone explain the unusual abundance of this species in the Clyde Estuary. For this, previous reports concerning heterotrophic growth and effects of grazing must also be considered.

The Role of Benthic Algae in Estuarine Pollution Assessment

Benthic algae might be considered suitable for estuarine pollution assessment for two reasons. Firstly they can be more abundant in the upper reaches of some estuaries than are the more commonly used macrofauna (but not necessarily the meiofauna). Secondly they present a more economic approach being quickly and cheaply sampled compared wth meiofauna and macrofauna. Although they are believed by some to be a notorious example of taxonomic confusion this is largely a reflection of their lack of study. Relatively few species are involved and their identification can be learnt without too much difficulty.

The occurrence of shell-boring Phaeophila species in Britain

Phaeophila tenuis (Kylin) R. Nielsen (= Entocladia tenuis Kylin) is reported for the first time from British shores. The existence in Britain of a form intermediate in morphology between P. tenuis and Phaeophila engleri Reinke is also noted. The relationships of this form and P. tenuis to each other and to Phaeophila dendroides (Crouan frat.) Batt. are discussed with reference to the effect of host-shell species and habitat on morphology.

Intertidal rocky shore seaweed communities subject to the influence of shallow water hydrothermal activity in São Miguel (Azores, Portugal)

The volcanic origin of the Azores archipelago (Portugal) gives rise to active deep sea and shallow water hydrothermal activity that affects benthic communities. Intertidal seaweed surveys were conducted at two shores affected by intense shallow water hydrothermal vents. Water temperature, acidity and salinity were monitored. Seaweed communities were found to be species poor and have a disproportionally larger number of filamentous early successional species on shores that are subject to the effect of hot and acidic freshwater of volcanic origin. There is an ecological resemblance between hydrothermally affected seaweed communities in the Azores and those affected by acid mine drainage in the UK, thus indicating that hydrothermalism can be a useful scenario for pollution studies under conditions of ocean warming and acidification.

Localized field effects of drainage water from abandoned coal mines on intertidal rocky shore seaweeds at St Monans, Scotland

This is the first account of the effects of drainage water from an abandoned coal mine on the seaweed community of the intertidal rocky shore in the British Isles. At St Monans, Scotland, along a 250 m transect, the brown climax species Fucus spiralis showed a low abundance in sampling quadrats (17.5%) and small plant size (3.5 cm), close to the outfall, compared to stations at increasing distance from the drainage source. Immediately below the outfall the fucoid community was replaced by a mixture of 12 species of freshwater, brackish and marine Chlorophyta, which did not occur, or only scarcely occurred, at any other transect station. At high tide, ferrous iron concentrations in the water were highest near the source (15.5 mg/l), while salinity was at its lowest (1.1 psu). Accordingly, iron tissue concentrations of apical segments of F. spiralis were also at their highest (12 mg Fe/g dry weight). Reproductive development of F. spiralis may have been inhibited close to the source.

Estuarine algal communities in two subestuaries of the Forth with different water quality

Summary A new method is described for quantifying the abundance of microscopic filamentous algae in estuarine mats of mixed species. Only small differences in species composition were found in such mats between two small estuaries markedly different in water quality, one affected by mine drainage, emphasizing the idea that the upper reaches of estuaries are colonized by relatively few, widely-tolerant species.