Biomass and nutrient dynamics of major green tides in Ireland: Implications for biomonitoring

The control of macroalgal bloom development is central for protecting estuarine ecosystems. The identification of the nutrients limiting the development of macroalgal blooms, and their most likely sources is crucial for management strategies. Three Irish estuaries (Argideen, Clonakilty and Tolka) affected by green tides were monitored from June 2016 to August 2017. During each sampling occasion, biomass abundances, tissue N and P contents, and δ15N were determined for tubular and laminar morphologies of Ulva. All estuaries showed maximum biomass during summer and minimum during winter. Tissue nutrient contents revealed P rather than N limitation. The δ15N during the peak bloom indicated agriculture as the most likely source of nitrogen in the Argideen and Clonakilty, and urban wastewaters in the Tolka. No differences in the δ15N, and the tissue nutrients content were observed between morphologies. The period between May and July is most suitable for bioassessment of green tides.info:eu-repo/semantics/publishedVersio

Two bloom-forming species of Ulva (chlorophyta) show different responses to seawater temperature and no antagonistic interaction.

The generalized use of molecular identification tools indicated that multispecific green tides are more common than previously thought. Temporal successions between bloom-forming species on a seasonal basis were also revealed in different cold temperate estuaries, suggesting a key role of photoperiod and temperature controlling bloom development and composition. According to the Intergovernmental Panel on Climate Change, water temperatures are predicted to increase around 4°C by 2100 in Ireland, especially during late spring coinciding with early green tide development. Considering current and predicted temperatures, and photoperiods during bloom development, different eco-physiological experiments were developed. These experiments indicated that the growth of Ulva lacinulata was controlled by temperature, while U. compressa was unresponsive to the photoperiod and temperatures assayed. Considering a scenario of global warming for Irish waters, an earlier development of bloom is expected in the case of U. lacinulata. This could have significant consequences for biomass balance in Irish estuaries and the maximum accumulated biomass during peak bloom. The observed seasonal patterns and experiments also indicated that U. compressa may facilitate U. lacinulata development. When both species were co-cultivated, the culture performance showed intermediate responses to experimental treatments in comparison with monospecific cultures of both species.This work has been co-financed under the 2014-2020 EPA Research Strategy (Environmental Protection Agency, Ireland), project no: 2015-W-MS-20 (the Sea-MAT Project) and project no: 2018-W-MS-32 (the MACRO-MAN Project), the 2014-2020 ERDF Operational Programme and by the Department of Economy, Knowledge, Business and University of the Regional Government of Andalusia (Project reference: FEDER-UCA18-106875), the INNOVALGA Project of the Spanish Ministry of Agriculture, Fisheries and Food, and the University of Cadiz throughout the mobility program “Atracción talento: Jóvenes Investigadores” (Ref: UCA/R22REC/2017). // Funding for open access provided by University of Malaga / CBUA

Biomass and nutrient dynamics of major green tides in Ireland: Implications for biomonitoring

peer-reviewedThe control of macroalgal bloom development is central for protecting estuarine ecosystems. The identification of the nutrients limiting the development of macroalgal blooms, and their most likely sources is crucial for management strategies. Three Irish estuaries (Argideen, Clonakilty and Tolka) affected by green tides were monitored from June 2016 to August 2017. During each sampling occasion, biomass abundances, tissue N and P contents, and δ15N were determined for tubular and laminar morphologies of Ulva. All estuaries showed maximum biomass during summer and minimum during winter. Tissue nutrient contents revealed P rather than N limitation. The δ15N during the peak bloom indicated agriculture as the most likely source of nitrogen in the Argideen and Clonakilty, and urban wastewaters in the Tolka. No differences in the δ15N, and the tissue nutrients content were observed between morphologies. The period between May and July is most suitable for bioassessment of green tides

Magnetic and interpolation techniques in the identification and analysis of metal contaminants In urban soils

Soil pollution has been identified as the third most important threat to soil quality in Europe. There are an estimated ~2,000 potentially contaminated sites in Ireland alone. Metal contamination has been identified as one of the most common types of soil contamination. Urban soils are particularly susceptible to metal contamination as they are subjected to constant inputs of anthropogenic origin. This thesis describes cost and time saving methodological approaches involving the use of magnetic susceptibility (MS) measurements and spatial analysis techniques which can be applied in the preliminary and exploratory phases of site assessment of suspected metal contamination in urban topsoils. The first study describes a methodological approach to the investigation of metal contamination of bonfire affected soils in a residential green space. Measurements of low frequency mass specific magnetic susceptibility (χlf) were recorded from the soil samples collected from a high density 1 x 1 m2 grid. Local Moran’s I hotspot analysis maps were produced for χlf and elemental concentrations of the soil samples. At this density, localized variations in susceptibility signals were distinguishable using the hotspot analysis technique to reveal statistically significant high value clusters where the most recent bonfire presided. Potential locations of historic bonfires were also identified. This application was shown to be effective, even when physical evidence on site was not obvious. At a second site, two methodological-based studies were conducted on the use of volume magnetic susceptibility measurements in the identification of metal contamination in topsoil. The study area was a former unregulated landfill site and is currently used as a local amenity park. The geostatistical analysis technique of ordinary cokriging (CK) was applied to the lead and volume magnetic susceptibility (κ) data collected to explore the use of this method in efficiently estimating the spatial distribution of lead present at the site. The objective was to improve spatial interpolation for lead using the auxiliary information of κ which could be more easily collected. The results were compared to ordinary kriging (OK) estimates of Pb concentrations. Root mean square errors (RMSE) and coefficients of determination (R2) signified a marked improvement in estimation capability of the CK procedure, demonstrating the efficiency of this method in an exploratory site investigation of this nature. In addition to site assessments, practical experiments were conducted to aid others in investigations of this kind. The effects of grass cover on in-situ volume MS (κ) measurements of urban soils was also investigated at the former unregulated landfill site. The results suggested that the removal of grass coverage prior to obtaining in-situ κ measurements of urban soil is unnecessary. This layer does not impede the MS sensor from accurately measuring elevated κ in soils (in typical urban green spaces with low vegetation cover <10 cm), and therefore κ measurements recorded with grass coverage present can be reliably used to identify areas of urban soil metal contamination. During the examination of bonfire soils a small experiment was carried out to isolate what temperature the soils directly below the base of the bonfire ash likely reached and it was determined they likely reached a maximum of 300°C and at this temperature had minimal impact on the MS signal of the soils. The methods of investigation detailed in this thesis can easily be adapted and applied in the inspection of suspected illegal burning or municipal waste disposal sites by local governing bodies charged with containing this issue

Magnetic and interpolation techniques in the identification and analysis of metal contaminants In urban soils

Soil pollution has been identified as the third most important threat to soil quality in Europe. There are an estimated ~2,000 potentially contaminated sites in Ireland alone. Metal contamination has been identified as one of the most common types of soil contamination. Urban soils are particularly susceptible to metal contamination as they are subjected to constant inputs of anthropogenic origin. This thesis describes cost and time saving methodological approaches involving the use of magnetic susceptibility (MS) measurements and spatial analysis techniques which can be applied in the preliminary and exploratory phases of site assessment of suspected metal contamination in urban topsoils. The first study describes a methodological approach to the investigation of metal contamination of bonfire affected soils in a residential green space. Measurements of low frequency mass specific magnetic susceptibility (χlf) were recorded from the soil samples collected from a high density 1 x 1 m2 grid. Local Moran’s I hotspot analysis maps were produced for χlf and elemental concentrations of the soil samples. At this density, localized variations in susceptibility signals were distinguishable using the hotspot analysis technique to reveal statistically significant high value clusters where the most recent bonfire presided. Potential locations of historic bonfires were also identified. This application was shown to be effective, even when physical evidence on site was not obvious. At a second site, two methodological-based studies were conducted on the use of volume magnetic susceptibility measurements in the identification of metal contamination in topsoil. The study area was a former unregulated landfill site and is currently used as a local amenity park. The geostatistical analysis technique of ordinary cokriging (CK) was applied to the lead and volume magnetic susceptibility (κ) data collected to explore the use of this method in efficiently estimating the spatial distribution of lead present at the site. The objective was to improve spatial interpolation for lead using the auxiliary information of κ which could be more easily collected. The results were compared to ordinary kriging (OK) estimates of Pb concentrations. Root mean square errors (RMSE) and coefficients of determination (R2) signified a marked improvement in estimation capability of the CK procedure, demonstrating the efficiency of this method in an exploratory site investigation of this nature. In addition to site assessments, practical experiments were conducted to aid others in investigations of this kind. The effects of grass cover on in-situ volume MS (κ) measurements of urban soils was also investigated at the former unregulated landfill site. The results suggested that the removal of grass coverage prior to obtaining in-situ κ measurements of urban soil is unnecessary. This layer does not impede the MS sensor from accurately measuring elevated κ in soils (in typical urban green spaces with low vegetation cover <10 cm), and therefore κ measurements recorded with grass coverage present can be reliably used to identify areas of urban soil metal contamination. During the examination of bonfire soils a small experiment was carried out to isolate what temperature the soils directly below the base of the bonfire ash likely reached and it was determined they likely reached a maximum of 300°C and at this temperature had minimal impact on the MS signal of the soils. The methods of investigation detailed in this thesis can easily be adapted and applied in the inspection of suspected illegal burning or municipal waste disposal sites by local governing bodies charged with containing this issue

Impact of grass cover on the magnetic susceptibility measurements for assessing metal contamination in urban topsoil

In recent decades, magnetic susceptibility monitoring has developed as a useful technique in environmental pollution studies, particularly metal contamination of soil. This study provides the first ever examination of the effects of grass cover on magnetic susceptibility (MS) measurements of underlying urban soils. Magnetic measurements were taken in situ to determine the effects on κ (volume magnetic susceptibility) when the grass layer was present (κgrass) and after the grass layer was trimmed down to the root (κno grass). Height of grass was recorded in situ at each grid point. Soil samples (n=185) were collected and measurements of mass specific magnetic susceptibility (χ) were performed in the laboratory and frequency dependence (χfd%) calculated. Metal concentrations (Pb, Cu, Zn and Fe) in the soil samples were determined and a gradiometry survey carried out in situ on a section of the study area. Significant correlations were found between each of the MS measurements and the metal content of the soil at the p<0.01 level. Spatial distribution maps were created using Inverse Distance Weighting (IDW) and Local Indicators of Spatial Association (LISA) to identify common patterns. κgrass (ranged from 1.67 to 301.00×10−5 SI) and κno grass (ranged from 2.08 to 530.67×10−5 SI) measured in situ are highly correlated [r=0.966, n=194, p<0.01]. The volume susceptibility datasets in the presence and absence of grass coverage share a similar spatial distribution pattern. This study re-evaluates in situ κ monitoring techniques and the results suggest that the removal of grass coverage prior to obtaining in situ κ measurements of urban soil is unnecessary. This layer does not impede the MS sensor from accurately measuring elevated κ in soils, and therefore κ measurements recorded with grass coverage present can be reliably used to identify areas of urban soil metal contamination