Browsing by Author "McElarney, Yvonne"
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Item Blooms also like it cold(Wiley, 2023-02-17) Reinl, Kaitlin L.; Harris, Ted D.; North, Rebecca L.; Almela, Pablo; Berger, Stella A.; Bizic, Mina; Burnet, Sarah H.; Grossart, Hans-Peter; Ibelings, Bastiaan W.; Jakobsson, Ellinor; Knoll, Lesley B.; Lafrancois, Brenda M.; McElarney, Yvonne; Morales-Williams, Ana M.; Obertegger, Ulrike; Ogashawara, Igor; Paule-Mercado, Ma. Cristina; Peierls, Benjamin L.; Rusak, James A.; Sarkar, Siddhartha; Sharma, Sapna; Trout-Haney, Jessica V.; Urrutia-Cordero, Pablo; Venkiteswaran, Jason J.; Wain, Danielle J.; Warner, Katelynn; Weyhenmeyer, Gesa A.; Yokota, KiyokoCyanobacterial blooms have substantial direct and indirect negative impacts on freshwater ecosystems including releasing toxins, blocking light needed by other organisms, and depleting oxygen. There is growing concern over the potential for climate change to promote cyanobacterial blooms, as the positive effects of increasing lake surface temperature on cyanobacterial growth are well documented in the literature; however, there is increasing evidence that cyanobacterial blooms are also being initiated and persisting in relatively cold-water temperatures (< 15°C), including ice-covered conditions. In this work, we provide evidence of freshwater cold-water cyanobacterial blooms, review abiotic drivers and physiological adaptations leading to these blooms, offer a typology of these lesser-studied cold-water cyanobacterial blooms, and discuss their occurrence under changing climate conditions.Item The changing times of Europe's largest remaining commercially harvested population of eel Anguilla anguilla L(Wiley, 2021-06-04) Aprahamian, Miran W.; Evans, Derek W.; Briand, Cedric; Walker, Alan M.; McElarney, Yvonne; Allen, Michelle M.This study quantifies the processes involved in regulating the European eel population of Lough Neagh, a lake in Northern Ireland. The relationship between glass eel input and silver eel output for the 1923–1997 cohorts was best described by a Beverton–Holt stock recruitment model. Glass eel input time series was not complete and was thus derived from the relationship between catches elsewhere in Europe and Lough Neagh, together with the addition of stocked glass eel. Silver eel output was the sum of silver eel escapement, catch and yellow eel catch converted to silver eel equivalents. Natural mortality increased with glass eel density, ranging from 0.017 to 0.142 year−1. The mean carrying capacity increased from ≈3.25 M silver eels (≈26 kg ha−1) for the 1923–1943 cohorts to ≈5.0 M (≈40 kg ha−1) for the 1948–1971 cohorts before regressing back to ≈3.25 M. The total silver eel output was highest during the late 1970s/early 1980s at 35–45 kg ha−1 year−1 and lowest during the early years of the 20th century and is currently at 10–15 kg ha−1 year−1. The findings are discussed in relation to (a) the ecological changes that have occurred within the lough, associated with eutrophication and the introduction of roach (Rutilus rutilus L.), and (b) the decline of the wider European eel stock across its distribution range. The findings from this study have relevance for the wider management of the European eel stock.Item Evaluating macrophytes as indicators of anthropogenic pressures in rivers in Ireland(Springer, 2021-02-10) Bucior, Adam; Rippey, Brian; McElarney, Yvonne; Douglas, RichardThe ability of macrophytes to indicate pressures in rivers was assessed by comparing metrics for nitrate (NO3), ammonia (NH4), soluble reactive phosphorus (SRP), dissolved oxygen saturation (DO), pH (PH) and siltation (SUBS) with direct estimates of the pressures at 810 sites in the Republic of Ireland, supplemented with General Linear Models (GLMs). The bivariate and rank correlation coefficients using the full data range and the first and fourth quartiles of the river pressures varied between 0.22 and - 0.39 for NO3 and DO; they were smaller or not significant for the other four metrics. The GLMs provided evidence for an independent association between NO3 and the nitrate concentration and SUBS and ammonia, indicating some specificity for these metrics. Discriminating sites in the first and fourth quartiles produced Type II errors between 37 (PH) and 69% (NH4), with a mean of 50. As the pressure-impact relationships are not precise enough (low correlation coefficients) that evidence from a single macrophyte metric is reliable, combining the metric with evidence from other biological groups at one site or from three or more sites may be the most useful approach.Item Long term abundance patterns of potamodromous brown trout in a large lacustrine catchment in County Fermanagh(Royal Irish Academy, 2021-09-29) Kennedy, Richard; Rosell, Robert S.; McElarney, Yvonne; Gallagher, Kevin; Allen, Michelle M.Long-term survey data detailing brown trout abundance in the Lough Erne catchment in Co. Fermanagh were tabulated from 1968–2016. These data included redd counts and electric fishing surveys across three key spawning tributaries in addition to gill-net surveys of the lake. The abundance of spawning adults fluctuated widely across the time-series and were examined in relation to various pressures, including a major disease epidemic and the invasion of the catchment by zebra mussels. A functional stock-recruitment relationship between adult spawners and young-of-year juveniles in the spawning tributaries was identified and described. Redd counts were significantly lower for the post-zebra mussel time-series (2000–16) than the pre-zebra mussel time-series (1968–99). The post-zebra mussel invasion period was associated with increased water clarity, reduced plankton productivity and changes to the balance of coarse fish species in the lake. The significance of these changes is discussed in relation to the trout stock.Item The long-term response of lake nutrient and chlorophyll concentrations to changes in nutrient loading in Ireland's largest lake, Lough Neagh(Royal Irish Academy, 2021-04-29) McElarney, Yvonne; Rippey, Brian; Miller, Claire; Allen, Michelle; Unwin, AntonyThe long-term response of chlorophyll-a (chl-a) to changing lake water nutrient concentrations and increasing water temperature was investigated in Lough Neagh, a large, hypereutrophic lake in Northern Ireland. Trends in external and internal nutrient loading and their relation to lake nutrient concentrations were also established. Lake water concentrations of total P (TP) have increased since the 1990s but were not correlated with catchment inputs, which showed no trend. The characteristics of internal loading of P have changed since the mid-1990s, with an earlier and larger mass of P released from the sediments each summer. Catchment inputs of total oxidised N (NOx) decreased from the peak value of 10,186T/yr in 1995 to 5,396T/yr in 2011, coinciding with a reduction in lake water concentrations. External inputs and lake concentrations of NOx were highly correlated (R=0.88). Water temperature increased approximately 1C and was a predictor of variation in chl-a from 1974 to 2012. After the peak chl-a concentration in 1993, dissolved inorganic N (DIN) also became an important predictor, accounting for almost half of the 44% variance explained by a hierarchical partition model. Decreasing log (DIN:TP) ratios suggest that N limitation of chl-a has become more important in the lake recently.Item A method to choose water depths for zooplankton samples in lakes(Wiley on behalf of Association for the Sciences of Limnology and Oceanography., 2021-11-23) Rippey, Brian; Macintosh, Katrina A.; McElarney, Yvonne; Douglas, RichardAs methods in the literature to sample zooplankton in lakes mostly offered general guidance on the sample depths, a new one was developed. Using the principle of volume-weighted sampling of the lake volume and an empirical function for the hypsometric curve, formulae for the volumes and areas of five equal sections of the lake were derived, which were then used to calculate section mean depths. Vertical net hauls taken at the mean depths are combined using a relation between their mean depths to produce one unbiased composite sample of the zooplankton. While generic formulae were derived, starting values for the depths that divide the lake volume into five equal sections are needed in order to apply the method, which then optimizes the depths; the method is implemented in a spreadsheet. The method was applied to four hypothetical lakes of maximum depth 12 m that cover a wide variation of lake form and how the sample depths vary with form was described; as lake form becomes more convex, the sample depths decrease, reflecting that more of the lake volume is at shallower depth. The method was used to estimate the whole-lake abundance of zooplankton in 51 lakes and no practical difficulties were encountered. It can be used in lakes up to a few tens of km2 in area.Item Recovery targets and timescales for Lough Neagh and other lakes(Elsevier, 2022-06-12) Rippey, Brian; McElarney, Yvonne; Thompson, James; Allen, Michelle; Gallagher, Mary; Douglas, Richard; Fisheries and Aquatic EcosystemsThe framework, model and methods of Nürnberg were applied and evaluated in Lough Neagh and 19 other lakes in order to establish inflow phosphorus concentrations that support target lake values. Supporting concentrations, in the absence of an internal load, were derived and the effect of uncertainty in the model retention coefficient was relatively small, ±11-20 % in Lough Neagh and an average (n = 17) of ±9.7 % in the other lakes. There was further support for the model and methods from an independent estimate of the net internal load in Lough Neagh (13 % difference) and from another model in the other lakes (Supporting concentrations, which should be lower, were by an average of 11 mg P m−3). In the framework, steady state with the phosphorus load is assumed, but, based on a generic lake model, is not likely if the hydraulic residence time>0.5-0.8 yr and should lead to a decrease in phosphorus retention, which was found during three periods in Lough Neagh. Based on a compilation of internal load recovery times from 23 lakes in the literature, it could take between 8 and 20 years for lakes with an internal load to approach their targets.Item Timescale of reduction of long-term phosphorus release from sediment in lakes(Elsevier, 2021-05-25) Rippey, Brian; Campbell, Julie; McElarney, Yvonne; Thompson, James; Gallagher, MaryIt is important for lake management and policy to estimate the timescale of recovery from long-term P release from sediment after a reduction in the external load. To provide a scientific basis for this, a condensed model was elaborated, applied and evaluated in four lakes. The model is based on first order kinetics, with an overall rate constant composed of the rate of diagenesis of labile P (kd,2) and rate of burial of P (kb) below an active sediment layer. Using the variation of P fractions in dated sediment cores, kd,2 varied from 0.0155 to 0.383 yr−1, kb from 0.0184 to 0.073 yr−1 and the overall rate constant from 0.0230 to 0.446 yr−1. The active layer depths, 8 to 29 cm, and kd,2 values are within the ranges found by others. The time for a 75% reduction (t75) of labile P in the active layer is 60 years in Lough Melvin, 3 in Ramor, 33 in Sheelin and 41 in Neagh, although P release is only important in Ramor and Neagh. Combining the kd,2 values with other estimates (mean 0.0981 yr−1, median 0.0426; n=14) produces a t75 value of less than 14 and 33 years. A review of other models indicates a timescale of one to two decades and from lake monitoring also of one to two decades. It is desirable to estimate the timescale directly in all lakes if sediment P release is important, but, generally, it should take between one and three decades.Item What makes a cyanobacterial bloom disappear? A review of the abiotic and biotic cyanobacterial bloom loss factors(Elsevier, 2024-02-09) Harris, Ted D.; Reinl, Kaitlin L.; Azarderakhsh, Marzi; Berger, Stella A.; Berman, Manuel Castro; Bizic, Mina; Bhattacharya, Ruchi; Burnet, Sarah H.; Cianci-Gaskill, Jacob A.; de Senerpont Domis, Lisette N.; Elfferich, Inge; Ger, K. Ali; Grossart, Hans-Peter F.; Ibelings, Bas W.; Ionescu, Danny; Kouhanestani, Zohreh Mazaheri; Mauch, Jonas; McElarney, Yvonne; Nava, Veronica; North, Rebecca L.; Ogashawara, Igor; Paule-Mercado, Ma. Cristina A.; Soria-Píriz, Sara; Sun, Xinyu; Trout-Haney, Jessica V.; Weyhenmeyer, Gesa A.; Yokota, Kiyoko; Zhan, Qing; Fisheries and Aquatic EcosystemsCyanobacterial blooms present substantial challenges to managers and threaten ecological and public health. Although the majority of cyanobacterial bloom research and management focuses on factors that control bloom initiation, duration, toxicity, and geographical extent, relatively little research focuses on the role of loss processes in blooms and how these processes are regulated. Here, we define a loss process in terms of population dynamics as any process that removes cells from a population, thereby decelerating or reducing the development and extent of blooms. We review abiotic (e.g., hydraulic flushing and oxidative stress/UV light) and biotic factors (e.g., allelopathic compounds, infections, grazing, and resting cells/programmed cell death) known to govern bloom loss. We found that the dominant loss processes depend on several system specific factors including cyanobacterial genera-specific traits, in situ physicochemical conditions, and the microbial, phytoplankton, and consumer community composition. We also address loss processes in the context of bloom management and discuss perspectives and challenges in predicting how a changing climate may directly and indirectly affect loss processes on blooms. A deeper understanding of bloom loss processes and their underlying mechanisms may help to mitigate the negative consequences of cyanobacterial blooms and improve current management strategies.