Long-term chemical and biological trends in Scottish streams and lochs

Between 1975 and 1985 several catchments in Scotland were established as reference sites to determine short-term (hours, days, weeks) and long-term (years, decades) changes in major physical, chemical and biological variables. The initial selection criteria included catchment size, land-use and deposition loading. Changes in fish status of lochs were determined by systematic netting while quantitative estimates of fish populations were made at stream sites. Egg survival and year class distribution assisted interpretation. Historical changes in pH based on stratigraphical changes in diatom assemblages are compared with recent measured changes which have occurred during the past 20 years when SO₂ emissions declined. Significant chemical and biological trends due to changes in pollutant loading are best detected in sensitive lochs which are unmanaged and with low organic content and acid neutralising capacity (ANC) close to zero. Significant trends are less apparent in lochs with managed (forested) catchments. Many stream sites also reveal long-term improvements in pH, sulphate (SO₄) Alkalinity (Alk) etc, but the significance of these trends is much less because of the greater inherent chemical variability. Stream sites close to ANC=0 provide the most wide-ranging evidence of ecological change, ie, increase in Alk, decrease in SO₄ and increase in numbers of juvenile salmonids. Measured chemical changes are compared with predicted estimates, based on critical load calculations and problems in interpretation are discussed.     

Long-term changes in the acidity of forest soils in North-East Scotland

Abstract. Fifteen soil profiles in the Alltcailleach Forest in NE Scotland have been resampled after almost 40 years. The pH, in 0.01 M CaCl₂, of the soil has decreased by 0.07 to 1.28 units in 80% of the surface organic horizons and by 0.16 to 0.54 units in 73% of the mineral horizons below 40 cm. The key factors governing increases and decreases in soil pH are changes in ground vegetation and tree canopy, although some effects of acid deposition cannot be ruled out.     

Pelagic fish and seabird interrelationships off the coasts of South West and South Africa

Breeding of the Cape cormorant on the South West African platforms and of the jackass penguin on islands off South Africa is coincidental with the seasonal availability of pelagic fish shoals. The largest numbers of Cape gannets and Cape cormorants occur off South West Africa where the biomass of fish is highest, though dominated by one species, the pilchard. By contrast, jackass penguins, limited in their range through flightlessness, are concentrated at the centre of the smaller but more stable South African multispecies fishery. In both South West and South Africa, densities of Cape cormorants are heaviest near the recruitment grounds for juvenile pilchard and anchovy. Island yields of guano are shown to provide reliable estimates of bird population sizes and fluctuations in these are closely related to temporal changes in fish abundance. They consequently have value in providing an understanding of fish stocks prior to exploitation and as indicators of the current state of the resources. Since the turn of the century large oscillations in the South West and South African pilchard populations were apparent but overfishing in the 1960s depressed both below their normal levels and reduced the numbers of birds.     

Liming acid streams: Aluminium toxicity to fish in mixing zones

Liming to neutralize acidic surface waters involves a possible risk of toxicity to fish due to precipitation or changes in speciation of Al. We report the response of captive brown trout to the experimental liming of an acid stream rich in Al. Within 15 m of lime dosing 0.22 µm filterable Al fell from 580 to 230 µg L^?1, and to 120 jig L^?1, within 30 m, though total Al was unchanged. After 24 hr, fish mortality was 100% at untreated acidic sites, 80% up to 30 m downstream of liming, declining to zero within 100 m. Mortality was 70% at 15 m below the confluence of an acidic tributary with the limed stream, despite little change in pH or total Al concentration. Mortalities were significantly correlated with concentrations of Al and Fe in gill tissues, and with 0.22 µm filterable Al and Fe in the water, but not with particulate Al or Fe. AI(OH)₄ ^?, precipitating A1 or polymeric hydrolysis products are all possible causes of the observed toxicity. Iron may have also have contributed, but the stream concentrations of this metal were relatively low. The practical conclusion is that changes in Al chemistry, where waters of differing acidity mix, may be important in some circumstances where river systems are limed selectively.     

Long-term changes in topsoil nematode populations in grazed pasture under elevated atmospheric carbon dioxide

Increasing atmospheric CO₂ concentrations are expected to affect ecosystems processes, and while a New Zealand study reported a response in soil biological activity after 4 years of CO₂ enrichment, apparently reflecting increased populations of Longidorus elongatus, similar findings have not been reported from other sites. Soil microfauna in 0–10 cm soil under a sheep-grazed pasture on a sand was assessed quarterly in FACE rings that were either at ambient CO₂ or had been exposed to 475 μl l⁻¹ CO₂ for some 9 years. Although the area had been subject to a severe drought and microfaunal populations were lower than previously found, the effects of elevated CO₂ on microfaunal populations were broadly similar to those at 4 years. Average populations of the root-feeding L. elongatus increased from 67,000 to 233,000 m⁻² (3.48×) compared with a 4.26× increase after 4 years; microbial-feeding nematodes increased slightly, while predacious nematodes showed a 2.0× increase. A pot experiment showed an additive effect of elevated CO₂ and L. elongatus abundance in reducing specific root length. That similar effects have been found 4 and 9 years after CO₂ enrichment commenced suggests they are real, and emphasises the difference to other sites around the world where much lower responses to elevated CO₂ have been found. This, in part, reflects the unique combination of soil, plant and soil biological conditions at each site and confirms the strong effect of soil type and vegetation on soil biological processes. Just as the effects of global climate change on a given region are idiosyncratic, so it seems are the effects of elevated CO₂ on soil and ecosystem processes. In part, this reflects our limited understanding of below-ground processes.     

Long-term changes in the Cu,Pb, and Zn content of forest soil organic horizons from North-East Scotland

Forest soil organic horizons from old and young plantations in the Alltcailleach Forest, N.E. Scotland were first sampled in 1949/50 and resampled in 1987. Copper, Pb and Zn in the soils were determined simultaneously on the original (stored) and the resampled soils. Overall mean Cu and Pb concentrations increased from 12.7 to 15.3 and 49.5 to 60.8 mg kg^?1 between 1949/50 and 1987. Zinc concentrations decreased from 76.4 to 60.7 mg kg^?1. Amounts of all 3 heavy metals increased because of increases in the thickness of organic horizons. Mean accumulation rates for Cu, Pb and Zn were 39.1, 186 and 114 g ha^?1 yr^?1, respectively. The rate of accumulation of Pb was significantly related to the rate of accumulation of organic matter. Copper and Zn concentrations were directly correlated with pH and inversely correlated with C/N ratio, whereas Pb was inversely correlated with pH and directly correlated with % C and C/N ratio. The more acidic soil organic horizons therefore contained higher concentrations of Pb and lower concentrations of Cu and Zn.     

Soil and land use effects on phosphorus in six streams draining small agricultural catchments in Scotland

Abstract. Phosphorus concentrations and outputs have been compared and contrasted in six small agricultural catchments in the west and northeast of Scotland. The loss of P from soils to stream waters was more from catchments with intensive dairy cattle farming in the west than from the less intensively stocked/arable catchments in the northeast, with striking differences being seen between the two regions. In the northeast, intensive animal farming caused less P loss in drainage water than arable management.
Larger mean annual concentrations were seen in the west (0.076-0.142 mg PO₄-P/l as molybdate-reactive phosphate–MRP) compared with the northeast (0.012-0.025 mg PO₄-P/l), a feature caused by the combination of limited P-retention in the western Gleysols and smaller inputs to the largely-podzolic northeastern catchments. Stream concentrations were decreased by dilution during winter storm flows and increased during summer baseflow and at the beginning of soil rewetting in autumn.     

Does natural acidity mediate interactions between introduced brown trout, native fish, crayfish and other invertebrates in West Coast New Zealand streams?

The presence of introduced brown trout (Salmo trutta) on the distribution of native crayfish (Paranephrops planifrons), native galaxiid fishes (Galaxias spp.) and invertebrate fauna was investigated in 18 West Coast New Zealand streams (8 with trout and 10 without trout) differing in chemical characteristics. Gut contents of trout, crayfish and eels were also examined to evaluate whether competition or predation could be linked to the patterns found. Abundances of crayfish and galaxiids were significantly lower in streams with trout, but in streams without trout, substrate size was one of the most important factors determining crayfish abundance. In contrast to crayfish, other macroinvertebrates were more abundant in trout streams than streams without trout and significantly more taxa were found in streams with trout. Macroinvertebrate abundance was related to environmental factors, such as pH, substrate, depth and total nitrogen. Gut content analysis showed an overlap in diet (mostly invertebrates) between trout and eels. Crayfish, however, had a more omnivorous diet where detritus was the most frequently occurring food material. Differences in chemical characteristics marked the streams with and without trout. Thus, trout were not present in streams with pH < 6.0. Crayfish and galaxiids were present in streams with pH ranging from 4.1 to 7.9, and those with pH < 6.0 may function as trout-free refuges where larger populations of these species may persist. However, other macroinvertebrate taxa may be more negatively affected by acidification than by trout. By protecting naturally acidic, brown water streams, New Zealand crayfish and galaxiid fish populations can be conserved within geographic areas where trout are present.     

Regional modeling of wind erosion in the North West and South West of Iran

About two-thirds of the Iran’s area is located in the arid and semiarid region. Lack of soil moisture and vegetation is poor in most areas can lead to soil erosion caused by wind. So that the annual suffered severe damage to large areas of rich soils. Modeling studies of wind erosion in Iran is very low and incomplete. Therefore, this study aimed to wind erosion modeling, taking into three factors: wind speed, vegetation and soil types have been done. Wind erosion sensitivity was modeled using the key factors of soil sensitivity, vegetation cover and wind erodibility as proxies. These factors were first estimated separately by factor sensitivity maps and later combined by fuzzy logic into a regional-scale wind erosion sensitivity map. Large areas were evaluated by using publicly available datasets of remotely sensed vegetation information, soil maps and meteorological data on wind speed. The resulting estimates were verified by field studies and examining the economic losses from wind erosion as compensated by the state insurance company. The spatial resolution of the resulting sensitivity map is suitable for regional applications, as identifying sensitive areas is the foundation for diverse land development control measures and implementing management activities.     

Long-term trends in stream chemistry and biology in North-East Scotland: Evidence for recovery

Since 1983 stream chemistry and macroinvertebrate ecology were monitored in ten streams draining the eastern Cairngorms. All streams have exhibited a decline in sulphate concentrations in response to reduced acid deposition; in the more acidic systems this has been reflected by a parallel increase in acid neutralizing capacity (ANC). In some streams this coincides with an increase in the abundance of acid-sensitive mayflies which may provide evidence for biological recovery. In the most chronically acidified systems no increased abundance has been observed despite significant increases in ANC. This suggests that further reductions in deposition and sufficient time for a reversal of soil acidification is required before any biotic recovery occurs.     

Freshwater fish in Scotland in the 18th, 19th and 20th centuries

Information on the distribution of freshwater fish in Scotland, published in old accounts (particularly around 1790 and 1880), is compared with that of a recent survey (around1970). Several changes are evident over the 180 years concerned, the main one being a northward extension of the distribution of a number of species, several apparently new to Scotland. Some of this dispersal is probably natural, but the main factor appears to be introduction by man — both from further south in Great Britain and from abroad. A number of unsuccessfull introductions of other species have been made. The future fish fauna of Scotland is discussed in the light of past and present events.     

Long-term population changes among breeding shorebirds in the Outer Hebrides, Scotland, in relation to introduced hedgehogs (Erinaceus europaeus)

In 1974, hedgehogs (Erinaceus europaeus) were introduced to the island of South Uist, which forms part of an area holding one of the largest concentrations of breeding shorebirds in Western Europe. By the 1990s these mammals had spread widely and become major predators of shorebird eggs. Breeding shorebirds were surveyed in 1983, when hedgehogs were confined to a small part of South Uist. They were surveyed again in 2000 by when hedgehogs had occupied all of the southern part (South Uist and Benbecula) of the 250 km² of lowland shorebird nesting habitat for at least 10 years but had not yet colonised large parts of North Uist and adjacent small islands. Between surveys the overall numbers of shorebirds in the hedgehog-free northern zone increased by 9% but in the southern zone, where hedgehogs were present, numbers decreased by 39%. Population changes differed among species, but for all species the population in the hedgehog-free northern zone outperformed that in the southern zone. The most marked differences occurred in northern lapwing (Vanellus vanellus) and common redshank (Tringa totanus), which both showed large declines in the southern zone and moderate to large increases in the northern zone. The north-south differences in population change could not be explained in terms of habitat change and were probably largely driven by hedgehog predation.     

Long-term trends of shorebird populations in eastern Australia and impacts of freshwater extraction

Shorebirds (Charadriiformes) and their wetland habitats are under threat worldwide. While data exist for shorebird population trends for many parts of the world, two thirds of Australia’s populations have not been assessed. We report the results of a large-scale aerial shorebird survey, sampling about a third of the Australian continent over a period of 24 years (1983–2006). Migratory shorebirds have declined by 73%, Australian resident shorebirds by 81%. Of the 10 wetlands supporting the highest number of shorebirds within the survey bands, eight were inland wetlands and only two coastal, emphasising the importance of inland wetlands for shorebirds. Wetland area decreased significantly at four of the 10 main sites. Annual rainfall showed no trends (1983–2005) but water extraction was substantial for four of the 10 wetlands, contributing to reduced flooding extent and frequency. Loss of wetlands due to river regulation is a significant contributor to the drastic decline in shorebird numbers in Australia, largely unrecognized in international conservation agreements in Australia.     

Crofting and bumblebee conservation: The impact of land management practices on bumblebee populations in northwest Scotland

The northwest of Scotland is a stronghold for two of the UK’s rarest bumblebee species, Bombus distinguendus and Bombus muscorum. The predominant form of agricultural land management in this region is crofting, a system specific to Scotland in which small agricultural units (crofts) operate rotational cropping and grazing regimes. Crofting is considered to be beneficial to a wide range of flora and fauna. However, currently there is a lack of quantitative evidence to support this view with regard to bumblebee populations. In this study we assessed the effect of land management on the abundance of foraging bumblebees and the availability of bumblebee forage plants across crofts in northwest Scotland. The results of our study show that current crofting practices do not support high densities of foraging bumblebees. Traditional crofting practice was to move livestock to uplands in the summer, but this has been largely abandoned. Summer sheep grazing of lowland pasture had a strong negative impact on bumblebee abundance and forage plant availability throughout the survey period. The use of specific ‘bird and bee’ conservation seed mixes appears to improve forage availability within the crofted landscape, although the number of bees observed remained low. Of the forage plants available, the three most frequently visited species were from the Fabaceae. We therefore conclude that the creation of agri-environment schemes which promote the use of Fabaceae-rich seed mixes and encourage the removal of sheep grazing on lowland areas throughout the summer are essential in order to conserve bumblebee populations within crofted areas.     

Increased mortality of fish due to changing Al-chemistry of mixing zones between limed streams and acidic tributaries

The present study is mainly focusing on mortality variations of fish due to changing Alchemistry of mixing zones. An artificial mixing zone was made by pumping water from a limed stream and an acidic tributary into a mixing channel. Atlantic salmon (Salmo salar L.) parr were exposed to the mixed water, limed stream water, and acidic tributary water. Mortality, blood haematocrit and plasma Cl^?-concentration were recorded. Neither mortality, nor changes in haematocrit and plasma Cl^? were observed when fish were exposed to limed water, while in both acidic and mixed water, mortalities and loss of plasma Cl^? were observed. The highest mortality rates were found within the initial part (0 to 20 s) of the mixing zone. Blood haematocrit increased only in fish exposed to acidic tributary water. Our results shows that changes in Al-chemistry and subsequent Al-polymerization occur when acidic tributary water is mixed with limed stream water. We have also demonstrated that the toxicity which can arise in mixing zones are greater than in the original acidic water before mixing. The variations in mortality observed are associated with the quality and quantity of Al-polymerization as well as ageing of the polymers.     

Recruitment and regeneration in populations of an endangered South Iberian Tertiary relict tree

The southern Iberian Peninsula is one of the most important refugia of Tertiary relict plant taxa in Europe. Under the present summer-dry climate, relict populations may experience a severely reduced regeneration. We studied the demographic structure, seed set and initial recruitment in relict populations of the endangered tree Frangula alnus subsp. baetica (Rhamnaceae) to evaluate its regeneration potential under the present environmental conditions. Populations are restricted to small riparian forests of Southwest Spanish and North Moroccan mountain ranges. The distribution of fruit crop sizes was highly left-skewed, and a few old trees produced the large bulk of the population seed pool. Bird-mediated seed dispersal appeared inefficient and post-dispersal seed predation by mice was high. Secondary seed transport by elevated creek water flow after winter rains modified the primary seed dispersal, but in consequence most seeds germinated on recently formed sandbanks where seedlings experienced reduced initial growth and survival. The most important mortality factor was desiccation, followed by herbivory. None of 1144 monitored seedlings survived for 2 years. The demographic survey through five populations indicates that drought periods may cause temporal regeneration bottlenecks. Moreover, over the last two decades populations have experienced increasing regeneration problems. Two causes are suggested: (1) browsing pressure from introduced game animals, and (2) the impact of torrential water flow peaks after heavy winter rains, exacerbated by large-scale vegetation slashing in surrounding cork oak forests. We discuss conservation strategies for this and other relict tree species that account for the pecularities of their habitat within the Mediterranean.     

Losses and recoveries of fish populations in acidified lakes of southern Finland in the last decade

Acid-induced fish damage in small lakes in southern Finland was studied in a fish status survey of eighty lakes from 1985–1987. Later, twenty of these lakes were selected for further monitoring. A sampling of these lakes from 1988–1989 showed that the decrease in some perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.) populations still continued. The results from the same lakes in 1992 showed that successful reproduction had taken place with many of the perch populations that had been close to extinction in 1985. In contrast, no signs of recovery in the roach populations were detected. The explanation for the appearance of new cohorts of perch could have been the decrease in acid deposition but the exceptional hydrological conditions of winters in the early 1990s may also have affected them. The different responses of the perch and roach populations were interpreted as a consequence of the different sensitivity of these two species to acidification. Even a slight improvement in the water quality has resulted in the appearance of strong new year-classes of perch, but not of roach. Therefore, more improvement in water quality is needed until a sensitive species like roach can reproduce again.     

Effects of fishing protection on the genetic structure of fish populations

Marine reserves have been identified as an important tool in the management of fishery resources and their number is increasing rapidly, most of them being on islands. However, knowledge on the real effect of protection from fishing on the genetic structure of populations, the spatial scales involved, or the suitability of islands as reserves in terms of connectivity, is scarce. This paper analyses the effects of fishery protection on the genetic structure of populations of Diplodus sargus, a target species, in protected and non-protected areas of the western Mediterranean. Populations studied showed high genetic variability at spatial scales from 10¹ to 10³ km. Protected areas have significantly higher allelic richness. The lower levels of heterozygosis and higher heterozygote deficit showed by islands compared with coastal areas makes clear the importance of considering the connectivity processes when designing a MPA.     

Raman spectroscopic study of changes in fish actomyosin during setting.

Actomyosins (AMs) isolated from tilapia, lemon sole, ling cod, and rock fish were heated at 40 degrees C, and structural changes in AMs were investigated using Raman spectroscopy to elucidate low-temperature gelling phenomenon, that is, "setting", of surimi. The following conformational transitions were observed in lemon sole, ling cod, and rock fish gels during setting: a slow unfolding of alpha-helix and exposure of hydrophobic amino acid residues occurring in long-time incubation at 40 degrees C, thereby forming hydrophobic interactions among AM molecules. In addition, the most frequent conformation in disulfide bonds was gauche-gauche-trans (g-g-t) form in the set gel. On the other hand, tilapia AM did not form a gel with heating at 40 degrees C, its alpha-helical structure in the myosin being far more stable than that of the other species. The heat resistance of the tight alpha-helix may prevent the gelation of tilapia AM. It is, therefore, likely that the unfolding of the alpha-helix of myosin is a prerequisite for gelation of AM during setting.