The palaeolimnology of Lough Murree, a brackish lake in the Burren, Ireland.

Peer-reviewed. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Biology & Environment: Proceedings of the Royal Irish Academy. To access the final edited and published work see doi: 10.3318/BIOE.2013.23Lough Murree, a rock/karst barrier lagoon, is superficially isolated from the sea and seasonal variations in lake water level reflect precipitation and groundwater variation. Lake salinity is influenced by subsurface saline intrusions, occasional barrier overwash together with precipitation and groundwater inflow, leading to poikilohaline conditions. Palaeolimnological reconstructions in Murree support the supposition that the lagoon was once superficially connected to the sea around the mid-nineteenth century. Physical, chemical and biological proxies suggest an evolution to more freshwater conditions. Uncertainties about the timing of the transition persist because of an unresolved sediment chronology. The isolation of Murree from the Atlantic Ocean has promoted the formation of dense charophyte beds composed of lagoonal specialist species, which are able to tolerate large variations in salinity

Determining the probability of cyanobacterial blooms: the application of Bayesian networks in multiple lake systems

A Bayesian network model was developed to assess the combined influence of nutrient conditions and climate on the occurrence of cyanobacterial blooms within lakes of diverse hydrology and nutrient supply. Physicochemical, biological, and meteorological observations were collated from 20 lakes located at different latitudes and characterized by a range of sizes and trophic states. Using these data, we built a Bayesian network to (1) analyze the sensitivity of cyanobacterial bloom development to different environmental factors and (2) determine the probability that cyanobacterial blooms would occur. Blooms were classified in three categories of hazard (low, moderate, and high) based on cell abundances. The most important factors determining cyanobacterial bloom occurrence were water temperature, nutrient availability, and the ratio of mixing depth to euphotic depth. The probability of cyanobacterial blooms was evaluated under different combinations of total phosphorus and water temperature. The Bayesian network was then applied to quantify the probability of blooms under a future climate warming scenario. The probability of the "high hazardous" category of cyanobacterial blooms increased 5% in response to either an increase in water temperature of 0.8°C (initial water temperature above 24°C) or an increase in total phosphorus from 0.01 mg/L to 0.02 mg/L. Mesotrophic lakes were particularly vulnerable to warming. Reducing nutrient concentrations counteracts the increased cyanobacterial risk associated with higher temperatures

A multi-proxy palaeolimnological study to reconstruct the evolution of a coastal brackish lake (Lough Furnace, Ireland) during the late Holocene

Peer-reviewed. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Palaeogeography, Palaeoclimatology, Palaeoecology, Vol 383-384, August 2013, Pages 1-15. To access the final edited and published work see doi: http://dx.doi.org/10.1016/j.palaeo.2013.04.016This study examines the evolution of Lough Furnace, a coastal brackish lake in the west of Ireland, using high-resolution sensors in the water column and palaeolimnological examination of the sediment archive. Palaeoenvironmental reconstructions suggest that meromixis formed as a result of sea level rise prior to ca. 4000 cal. yr BP. Increased seawater inflow has progressively led to permanent water stratification, which caused the onset of anoxia, making the monimolimnion a harsh environment for biological life. Diatom floristic interpretations suggest a progressive upcore increase in salinity, which is paralleled by a reduction in cladocera remains. Diagenetic processes have not altered the sediment organic matter signature. Organic matter mainly derives from freshwater DOC and appears to be linked to the presence of peat bogs in the catchment as confirmed by the C/N ratio. Upcore variations in the C/N ratio with a ca. 800-year periodicity have been interpreted as the result of alternating dry and wet climatic phases during the late Holocene, which appear synchronous with the NAO and long-term solar cycles. The current hydrology is largely controlled by freshwater inflow, which determines permanent meromictic conditions. Overturns are rare, requiring a specific combination of factors such as exceptionally dry and warm summers followed by cool autumns. According to the climate projections for the next century in Ireland, permanent meromictic conditions will probably continue

Contrasting pelagic plankton in temperate Irish lakes: the relative contribution of heterotrophic, mixotrophic, and autotrophic components, and the effects of extreme rainfall events

The mobilisation of energy from allocthonous carbon by heterotrophic bacterioplankton can be proportionally more important than autotrophic production in humic lakes. Moreover, increasing levels of dissolved organic carbon (DOC) in many aquatic systems linked to increases in precipitation, which in turn may be related to changing climate, mean that this heterotrophic component of the food web may play an increasing role in the overall transfer and production of energy, particularly within peatland catchments. While such catchments are common in the temperate northwest Atlantic regions of Europe, studies describing the seasonal dynamics of the heterotrophic, mixotrophic, and autotrophic components of their aquatic food webs are rare. In this study, the biomass of these pelagic components was enumerated over 1 year in 2 oligotrophic lakes, both situated in peatland catchments in the west of Ireland but with contrasting DOC concentrations. Bacterial biomass dominated the pelagic food web of the more humic lake, Lough Feeagh, while autotrophic phytoplankton biomass was greatest in the clearwater lake, Lough Guitane. The biomass of potentially mixotrophic flagellates was also slightly larger in the Lough Guitane, while phagotrophic ciliate biomass was comparable between the 2 lakes. An extreme precipitation event led to a significant increase in bacterial biomass while simultaneously depressing autotrophic production for several months in the humic lake. Extreme precipitation in the clearwater lake also depressed autotrophic production but did not give rise to significant increases in bacterial biomass. This quantification of autotrophic, mixotrophic, and heterotrophic components provides a vital first step in understanding how pelagic communities contribute to net ecosystem productivity, and thus how Irish peatland lakes may be affected by projected climate changes

The response of a humic lake ecosystem to an extreme precipitation event: physical, chemical and biological implications

Climate projections indicate that the frequency and severity of extreme precipitation events will increase over the next century. Although a large number of lakes across the globe are systematically monitored, it is rare to have a wide range of ecological indices measured at high enough frequency and over a sufficient time scale to allow characterisation of the response of a lake ecosystem to such events. We present data from Lough Feeagh, a relatively large oligotrophic lake in Ireland, which was at the epicentre of a once in 250-year precipitation event in July 2009 when 50 mm of rain fell in less than 2 hours. The effects of the resulting flood on the water column stability, chemistry, biology, and metabolism were examined, and data from multiple years before and after the event were used to ascertain the significance and longevity of any observed changes. The flood caused the water column to destabilise prematurely and depressed primary production. Bacterial biomass was high in the month after the flood, and zooplankton assemblages in late 2009 were significantly different from those of other years. Changes in all these variables combined to produce lower rates of gross primary production and higher rates of respiration than those measured between 2010 and 2014, resulting in more pronounced negative net ecosystem production than in the other years. Despite all these changes, the normal seasonal cycles resumed in 2010, and it appears that this rare but significant event did not have a long-term impact on the ecosystem functioning of the lake

Appendix A. Selecting Bayesian network structure: number of states and threshold values.

Selecting Bayesian network structure: number of states and threshold values

Familial hemophagocytic lymphohistiocytosis type 5 (FHL-5) is caused by mutations in Munc18-2 and impaired binding to syntaxin 11

Rapid intracellular transport and secretion of cytotoxic granules through the immunological synapse requires a balanced interaction of several proteins. Disturbance of this highly regulated process underlies familial hemophagocytic lymphohistiocytosis (FHL), a genetically heterogeneous autosomal-recessive disorder characterized by a severe hyperinflammatory phenotype. Here, we have assigned FHL-5 to a 1 Mb region on chromosome 19p by using high-resolution SNP genotyping in eight unrelated FHL patients from consanguineous families. Subsequently, we found nine different mutations, either truncating or missense, in STXBP2 in twelve patients from Turkey, Saudi Arabia, and Central Europe. STXBP2 encodes syntaxin binding protein 2 (Munc18-2), involved in the regulation of vesicle transport to the plasma membrane. We have identified syntaxin 11, a SNARE protein mutated in FHL-4, as an interaction partner of STXBP2. This interaction is eliminated by the missense mutations found in our FHL-5 patients, which leads to a decreased stability of both proteins, as shown in patient lymphocytes. Activity of natural killer and cytotoxic T cells was markedly reduced or absent, as determined by CD107 degranulation. Our findings thus identify a key role for STXBP2 in lytic granule exocytosis