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The Encyonopsis microcephala-complex occurs in oligo-mesotrophic freshwaters and is often abundant in the periphyton of low nutrient lakes of high conservation value. It is globally distributed and increasing in apparent diversity with the discovery of additional species. To better differentiate this taxonomic aggregate, we re-examined the original type material of E. alpina, E. angusta and E. tavirana with light (LM) and scanning electron (SEM) microscopy. We investigated the morphology, ultrastructure and ecology of Encyonopsis populations from Ireland, which included previously unreported taxa and morphodemes of E. krammeri, E. neerlandica and E. subminuta. The apparently cosmopolitan E. microcephala was not found in collections from Ireland but two new species were described and compared to others in the complex. Encyonopsis carraensis sp. nov. was associated with a marl-precipitating community in low nutrient lakes, while Encyonopsis hibernica sp. nov. occurred in more productive waterbodies. Several Encyonopsis species had environmental optima near the oligo-mesotrophic boundary characteristic of the microcephala-complex. However, the niches of others were distributed along a wider gradient of water quality. Therefore, when Encyonopsis populations are prevalent in epilithic communities, the use of a more refined taxonomy is recommended for lake ecological assessment.

HELDERCUNHA PEREIRA 1*, NORMAN ALLOTT 2, CATHERINE COXON 3, OWEN NAUGHTON 4, PAUL JOHNSTON 4 AND LAURENCE GILL 4 1 CENTRE FOR THE ENVIRONMENT, TRINITY COLLEGE DUBLIN, DUBLIN 2, IRELAND, DEPARTMENT OF ZOOLOGY, TRINITY COLLEGE DUBLIN, DUBLIN 2, IRELAND, 3 DEPARTMENT OF GEOLOGY, TRINITY COLLEGE DUBLIN, DUBLIN 2, IRELAND AND DEPARTMENT OF CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING, TRINITY COLLEGE DUBLIN, DUBLIN 2, IRELAND

This paper compares, for the first time, nutrient levels and chlorophyll a measured in a set of seasonal lakes with those reported for permanent lakes in the literature. Twenty-two turloughs (karstic seasonal lakes) in western Ireland were sampled monthly from the onset of flooding (October) until they dried out (6 to 9 months). The turloughs showed similar levels of nutrients and chlorophyll a to those reported for Irish and international lakes. Chlorophyll a peaked between November and February in the majority of turloughs, sometimes with values higher than those measured in mesotrophic lakes in summer. A significant log-linear regression was found between total phosphorus and chlorophyll a, which suggests P limitation of algal biomass in the majority of the turloughs. The regression characteristics were not significantly different than those described in similar studies of permanent lakes. Patterns in seasonal variation of nutrients are also presented, their underlying causes being discussed in relation to their transport within catchments. Our results show that despite being predominantly winter phenomena, turloughs can be as productive as permanent lakes.

Dynamic modelling was used to quantify the impact of projected climate change, and potential changes in population and land use, on phosphorus (P) export from a sub-catchment in SW Ireland using the Generalised Watershed Loading Functions (GWLF) model. Overall the results indicated that the increase in annual total phosphorus loads attributable to climate change was greater than that from either population or land use change, and therefore that future climate variability will pose an increasingly significant threat to the successful long-term implementation of catchment management initiatives. The seasonal pattern in projected P export mirrored changes in streamflow, with higher rates between January and April and lower rates in summer. The potential reduction in export in summer was, however, negated when increases in population were included in simulations. A change in the slurry spreading period from that stipulated in national regulations to the months between April and September could potentially mitigate against future increases in dissolved P export in spring. The results indicate that projected changes in climate should be included when undertaking modelling exercises in support of decision making for catchment management plans.

A positive relationship was observed between winter nitrate concentrations in two lakes in SW Ireland and the latitudinal position of the Gulf Stream in the previous spring. Weaker but statistically significant relationships were apparent between the Gulf Stream position and weather variables, as well as soil moisture levels, in the same year. Wind speed, cloud cover and precipitation in May and June were negatively related to the Gulf Stream position in April. In contrast, air temperature and sunshine hours in May and June and the magnitude of the soil moisture deficit in June were positively related. There was also a positive correlation between the magnitude of the early summer soil moisture deficit and lake nitrate concentrations in the following winter. This three way linkage implies that the concentration of winter nitrate in these lakes is influenced by a sequence of related factors that are initiated by the latitudinal position of the Gulf Stream. In this sequence the position of the Gulf Stream appears to influence early summer weather in SW Ireland which in turn dictates the extent of moisture deficit in catchment soils and, consequently, the degree of nitrate loss to surface waters in the autumn. This connection, between events in the Atlantic Ocean, weather systems in the North West Atlantic and processes in catchment soils in SW Ireland has implications for both the quality and quantity of biota in lakes and catchments in the region.

(2005). The identification of lake types using macrophyte community composition in Ireland. SIL Proceedings, 1922-2010: Vol. 29, No. 1, pp. 296-299.

The genus Brachysira is frequently encountered in the algal flora of oligotrophic freshwaters. In order to re-evaluate its diversity in Irish waters, light and scanning electron microscopy was used to examine populations at 209 river sites and in 85 lakes. The full range of morphological variation of all common and sometimes challenging Brachysira populations was investigated. The study revealed two new species, Brachysira praegeri sp. nov. and Brachysira conamarae sp. nov. and compared them to all closely related taxa. The study also recorded B. intermedia and B. neglectissima which are new records for Ireland. Further taxonomic clarification is required for a diatom resembling B. intermedia and the complex of taxa around the polymorphic B. microcephala. Individual Brachysira taxa differed with respect to their optima along an alkalinity-pH gradient, but the trophic requirements of all forms were comparable, suggesting that species may be merged for routine water quality assessment. Nevertheless, it is recommended that Brachysira morphotypes be enumerated separately until their taxonomy is more fully resolved and their significance for the biodiversity of epilithic communities has been clearly established.

(2008). Reconstruction of the recent past in a west of Ireland catchment. SIL Proceedings, 1922-2010: Vol. 30, No. 4, pp. 512-514.

In moorland catchments on granite or quartzite in western Ireland, some planted with conifers, water was more acid and macroinvertebrate diversity lower in afforested streams than at non-afforested...

Dissolved organic carbon (DOC) from peat soils has implications both for the ecology of receiving waters and for the quality and treatment costs of water used for human consumption. Fluxes of DOC from peat soils are also relevant in the context of the global carbon cycle. Chapter 12 in this volume has reviewed the evidence for the effects of different environmental factors on the decomposition of peat soils and the export of DOC, drawing on literature and long-term data acquired from a number of European sites. The conclusion from this and many other studies is that, although there may be other influences such as land management and recovery from acid deposition, climate factors are a major player in both the short-term variability and longer-term trends seen in measured DOC concentrations and fluxes. Given the importance of DOC and likely future changes in climate, it is timely and opportune to make use of our current understanding to project possible future DOC.

The transfer of phosphorus from terrestrial to aquatic ecosystems is a key route through which climate can influence aquatic ecosystems. A number of climatic factors interact in complex ways to regulate the transfer of phosphorus and modulate its ecological effects on downstream lakes and reservoirs. Processes influencing both the amount and timing of phosphorus export from terrestrial watersheds must be quantified before we can assess the direct and indirect effects of the weather on the supply and recycling of phosphorus. Simulation of the export of phosphorus from the terrestrial environment is complicated by the fact that it is difficult to describe seasonal and inter-annual variations by existing process-based and empirical models. These variations are also strongly influenced by the history of the weather and by the frequency of extreme weather events. For example, the effects of storm runoff on the export of phosphorus can be very sensitive to levels of soil saturation and soil moisture, which are in turn influenced by the past history of precipitation and evapotranspiration. Inclusion of effects such as these is impossible using simple empirical models and difficult using process based models when model parameterization changes in response to antecedent conditions.

Human-induced changes in the nitrogen cycle due to the increased use of artificial fertilisers, the cultivation of nitrogen-fixing crops and atmospheric deposition have made nitrogen pollution to surface waters a long-standing cause for concern. In Europe, legislation has been introduced to minimise the risk of water quality degradation from excessive nitrogen inputs e.g., the European Union Nitrates Directive (EU, 1991), Drinking Water Directive (EU, 1998) and Water Framework Directive (EU, 2000). Coastal regions in particular have been an important focus, since coastal eutrophication has been attributed to increased fluxes of nitrogen from the landscape (Howarth et al., 1996; Boesch et al., 2006). While nitrogen is typically not the limiting nutrient in inland waters, increases in the nitrogen supply to rivers and lakes can impact the N:P ratio, influence the structure of aquatic food webs (Elser and Urabe, 1999; Arbuckle and Downing, 2001), regulate the seasonal development of phytoplankton (Van den Brink et al., 1993) and promote the growth of aquatic macrophytes (Kirchmann et al., 2004).

The CLIME studies in Western Europe were confined to a relatively small number of lakes situated in Britain and Ireland. In this chapter, we use the terms ‘Britain’ and ‘Ireland’ when describing the location of the lakes and the term ‘British Isles’ to define the area covered by the weather typing system devised by Lamb (1950). The climate of Britain and Ireland is notoriously variable and is strongly influenced by the movement of weather systems across the Atlantic (Barrow and Hulme, 1997). Winters are typically mild and wet but there are large year-to-year variations in the seasonal distribution of the rainfall. The variable nature of the climate has a pronounced effect on the physical characteristics of the lakes and the flux of nutrients (Allott, 1986; George et al., 2004). In this chapter, we review the climatic changes projected for the region and assess their potential impact on the dynamics of the lakes.

Recent increases in dissolved organic carbon (DOC) concentrations in surface waters across both Europe and North America have focused attention on the factors controlling the export of DOC compounds from catchments. Waters containing high concentrations of DOC generally have a characteristic brown colour and are associated with the presence of highly organic soils. Catchments dominated by these soils typically export between 10 and 300 kg DOC ha−1 year−1 (Billett et al., 2004; Laudon et al., 2004; Jonsson et al., 2006). A portion of this DOC is mineralised in streams and lakes to CO2, while the remainder is transported to the sea (Jonsson et al., 2006). Organic matter accumulates in soils when decomposition rates are restricted either by low temperatures or water-logged conditions. In Europe organic soils are found mainly in colder, wetter

Excess phosphorus (P) loading is a major cause of deterioration in surface water quality. In Ireland, regulation has focussed on control of P losses from agriculture and wastewater treatment plants (WWTPs): the two main sources of excess P. Hindcast modelling for Lough Leane, south-west Ireland, indicated that, while the only municipal (point) source contributed up to 41% of the annual TP loading until the mid 1980s, over 90% of the TP load was from diffuse sources following upgrading of the WWTP. Field data from 2000–2006 confirmed that most of the TP load came from agriculture, with 73% being exported between September and February, generally the wettest months in the region. However, the WWTP contributed up to 60% of daily loads during summer. Short lake residence times (two to four months) between October and February indicated that external loadings during these months were unlikely to make a significant contribution to summer phytoplankton growth in the lake. In contrast, the potential effects of point sources during low flows were maximised by longer residence times between April and September. The results highlight the importance to aquatic pollution impacts of, and therefore the need for regulatory responses to respect, seasonal variations in loading and residence time.

SUMMARY. 1. Temperature and oxygen were examined in six small western Irish lakes (areas 2–110 ha) in 1981, 1982 and 1984. 2. The four deeper lakes (z= 6–11m) stratify stably in the same manner as some well-known stratifying lakes in Britain. Windiness (due to proximity to the ocean) seems generally to be reflected in the lakes by the presence of a sharp thermo clinic. Considerable variation in the pattern of stratification occurs from year to year. 3. Two shallow lakes (z= 4.1 and 2.7m) stratify only in periods of warm, calm weather. 4. Annual heat-budgets range from 4.1 kcal cm−2 to 13.7 kcal cm−2. There is a strong linear relationship between mean-depth and annual heat-budget. 5. Oxygen depletion is severe in the more productive lakes.