Mercury accumulation by the eelpout (Zoarces vivparus L.) in the Forth Estuary, Scotland

The Forth Estuary, in eastern Scotland, has received inputs of the toxic metal, mercury, from an industrial discharge for many decades. This has led previously to accumulation of relatively high levels of mercury in the environment and biota of the estuary, although both inputs and levels in biota have fallen sharply since the early 1980s. The general literature on mercury in the marine environment is reviewed, including the human health implications of mercury in aquatic food chains. A review is also presented of current knowledge of mercury in the Forth Estuary environment and biota, as carried out by the statutory water quality authority, the Forth River Purification Board (FRPB) and others. Studies by the FRPB have indicated that a resident teleost fish species, the eelpout (Zoarces viviparus L.) may be a suitable candidate for use as a bioaccumulation monitoring species for mercury in the Forth. Its potential and demonstrated use in other pollution studies in North Sea and Baltic waters are reviewed. In order to investigate the use of this species for bioaccumulation monitoring of mercury, the variability of mercury concentrations in a number of tissues was investigated, in relation to biological, temporal (both seasonal and annual) and spatial factors, during the period November 1989 to March 1992. Although skeletal muscle and liver were investigated in most detail, kidney, testes, ovary, and tissues of the viviparous brood were also studied. Mean mercury concentrations in all tissues were relatively low, although skeletal muscle, liver and kidney tended to have higher values than the reproductive tissues. The log of mercury concentration in skeletal muscle increased in a statistically significant linear fashion with length, weight and age of the fish, in almost all samples. There was no statistically significant difference in the rate of increase (i.e. the slope of the linear regression of log concentration on length) between the sexes. There was a clear seasonal pattern in the rate of increase of mercury concentration with length in both years, with highest values in the Spring period, March to May, followed by a sharp decrease in the rate in Summer, June to August. Differences between seasons were not, however, statistically significant in either year. The rate was negatively correlated with the allometric condition factor. The total mass of mercury in the skeletal muscle of a standard fish showed little significant variation between seasons although there was considerable seasonal difference in total muscle mass. It is suggested that seasonal variability of mercury levels in eelpout skeletal muscle in the Forth Estuary is related principally to seasonal changes in skeletal muscle mass, rather than to changes in mercury burden. Both liver and testes showed a seasonal peak in relative weight (somatic index) in Summer months, with a seasonal minimum mercury concentration in the same period. There was little difference between seasons in the total mercury burdens of these organs, with respect to fish size. Thus, the seasonal variability of mercury concentrations in the liver and testes appears to be due to seasonal growth and regression patterns. Mercury concentrations and burdens of the female reproductive tissues were studied in relation to the viviparous reproduction of the eelpout. The mercury concentration of the intra-ovarian brood is significantly correlated with that of the maternal skeletal muscle. The increase of brood mercury burden through the brood development period was slow initially, followed by a rapid increase which was closely related to a period of rapid increase in brood weight. The distribution of mercury in the ovary was described, and a high concentration of mercury was found in a cellular fraction of the ovarian fluid, relative to the supernatant fluid. Larval eelpout are known to consume this cellular fraction, including red blood cells, which is released from the inner wall of the ovary. It is possible that this matrotrophic form of nutrition may provide the main route for accumulation of mercury, at least in older larvae. Uptake, internal dynamics and elimination of methylmercury by eelpout was investigated under laboratory conditions by the administration of »'Hg-labelled methylmercuric chloride, by oral dosing or intra-peritoneal (i.p.) injection. Patterns of tissue redistribution of mercury with time suggest that the dynamics of i.p. administered methylmercury are related closely to the structure and biological functions of the tissues. The transfer of a portion of an i.p. administrated dose of methylmercury, from the peritoneum to the intra-ovarian tissues of the eelpout (including brood and ovarian fluid), was demonstrated for the first time in a limited investigation of mercury transfer between generations. Elimination of orally administered methylmercury, measured by whole body counting of live fish was, initially rapid, with 20% of the dose lost over two days, with a slower loss of a further 20% over the following two weeks. The initial period of rapid loss coincides with the loss of mercury from the intestine of i.p. dosed fish suggesting a two compartment loss. More detailed analysis of biological half-times of elimination was not permitted by the restricted duration of the experiment. The literature and concepts of trend monitoring and Environmental Capacity for mercury in the marine environment were reviewed. Linking of archive data, collected by the FRPB between 1978 and 1988, with results from the present study, allowed an analysis of temporal trends of mercury in Forth Estuary eelpout. There has been a clear trend of decreasing mercury concentrations in eelpout from the Forth Estuary since the early I980’s although levels in fish from the Firth of Forth, where environmental mercury levels are lower, have remained relatively unchanged. In the early I980's, mean concentrations in fish from the site closest to the main mercury discharge were in excess of 0.3 mg.kg the acceptable limit established by the European Community Environmental Quality Standard (EQS) for mercury in fish muscle Mercury concentrations in eelpout from the Firth were lower in than those from the Estuary in all years. Using this data, an aposteriori estimation was made of the Environmental Capacity of two Forth Estuary sites to receive mercury inputs. The meeting of the EQS was taken as the acceptable endpoint of the calculation. The estimated values of Environmental Capacity, of I8.58 kg per year at the site closest to the discharge would now be in excess of the currently permitted inputs of mercury to the Forth Estuary

What the council of economic advisors need to know about sustainable development

The decision by Alex Salmond to appoint a Council of Economic Advisors to move economic decision making away from purely political rationale is particularly welcome given the new administration’s commitment to sustainable economic growth as the overarching priority. From the first Minister’s statement to parliament4 is clear that as an economist he recognises that sustainable economic growth is not (just) economic growth that continues but economic growth that is environmentally and socially sustainable. In the Scottish Environment Protection Agency we have wrestled with just what sustainable economic growth might mean and here we offer some of our own thoughts to help the new council of economic advisors in their work

Biocapacity and cost-effectiveness benefits of increased peatland restoration in Scotland

Ecological Footprint and biocapacity accounting is a widely-used ecological accounting framework which tracks human demand against the biosphere’s rate of regeneration. However, current national assessments do not yet include carbon-dense peatlands, hindering the evaluation of peatland biocapacity contributions. Also, the economic efficiency of peatland restoration is understudied and needed to inform land use decisions. We provide the first assessment of Scotland’s biocapacity and add peatlands as a novel land type. We then project the biocapacity impacts in 2050 of current peatland restoration targets and various alternative management scenarios. Finally, we estimate the cost per tonne of greenhouse gas abated of various peatland restoration scenarios, and compare this with estimates of afforestation mitigation costs from the literature. Our results show that Scotland’s per-person biocapacity exceeds the UK average by a factor of three. However, despite covering 25% of land area, peatland biocapacity increases Scotland’s biocapacity total by only 2%, while the Carbon Footprint of degraded peatlands increases Scotland’s ecological deficit by 40%. Current peatland restoration targets of the Scottish Government are estimated to reduce the national ecological deficit by only 9% in 2050. The cost-effectiveness of peatland restoration is context-dependent, and extremely cost-effective methods are applicable to peatland areas far exceeding current government restoration targets. Our findings provide land managers with evidence in favour of increased peatland restoration, both in terms of boosting biocapacity, and economic cost- effectiveness

Knowledge sharing, problem solving and professional development in a Scottish Ecosystem Services Community of Practice

The ecosystem services framework has now been embodied in policy and practice, creating the need for governance structures that allow science, policy and practice to come together and facilitate shared learning. We describe five years of progress in developing an Ecosystem Services Community of Practice in Scotland, which brings together over 600 individuals from diverse constituencies to share experiences and learn from each other. We consider the ‘community’ and ‘practice’ aspects to demonstrate the benefits of establishing an Ecosystem Services Community (ESCom). We also demonstrate how the journey involved in the creation and continuing evolution of ESCom has proved valuable to researchers, policy-makers, practitioners and students and as such has contributed to social learning. We reflect on challenges, given the voluntary nature, absence of formal institutional support and emergence of initiatives focusing on overlapping topics. Based on our experience, we provide ten recommendations to help future ecosystem services communities of practice

The critical loads and levels approach for nitrogen

This chapter reports the findings of a Working Group to review the critical loads (CLs) and levels approach for nitrogen (N). The three main approaches to estimating CLs are empirical, mass balance and dynamic modelling. Examples are given of recent developments in Europe, North America and Asia and it is concluded that other countries should be encouraged to develop basic assessments using soil, land cover, and deposition map overlays in order to determine what regions might exceed nitrogen CLs. There is a need for increasing the certainty of critical load (CL) estimates by focusing on empirical data needs, especially for understudied ecosystems such as tropical or Mediterranean, high elevation environments, and aquatic systems. There is also a need to improve steady-state mass balance parameters, especially soil solution terms, such as nitrate leaching, used to determine the CL, and denitrification, which is an equation parameter. Improved dynamic models are needed for predicting plant community changes, and work should continue on existing models to determine CL values. Dynamic models require more data and are more complex than simple calculated CLs but offer more information and allow the development of ‘what if?’ scenarios. Optimal use of CLs requires expert knowledge of ecosystem values to provide reference states so that safe deposition amounts can be determined. Increased interaction between CL and biodiversity specialists to identify critical biodiversity limits would help provide better CL assessments