Browsing by Author "Taranu, Zofia E."

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Open Access
Regional versus local drivers of water quality in the Windermere catchment, Lake District, United Kingdom: The dominant influence of wastewater pollution over the past 200 years
(Wiley, 2018-05-10) Moorhouse, Heather L.; McGowan, Suzanne; Taranu, Zofia E.; Gregory-Eaves, Irene; Leavitt, Peter R; Jones, Matthew D.; Barker, Philip; Brayshaw, Susan A.
Freshwater ecosystems are threatened by multiple anthropogenic stressors acting over different spatial and temporal scales, resulting in toxic algal blooms, reduced water quality and hypoxia. However, while catchment characteristics act as a ‘filter’ modifying lake response to disturbance, little is known of the relative importance of different drivers and possible differentiation in the response of upland remote lakes in comparison to lowland, impacted lakes. Moreover, many studies have focussed on single lakes rather than looking at responses across a set of individual, yet connected lake basins. Here we used sedimentary algal pigments as an index of changes in primary producer assemblages over the last ~200 years in a northern temperate watershed consisting of 11 upland and lowland lakes within the Lake District, United Kingdom, to test our hypotheses about landscape drivers. Specifically, we expected that the magnitude of change in phototrophic assemblages would be greatest in lowland rather than upland lakes due to more intensive human activities in the watersheds of the former (agriculture, urbanization). Regional parameters, such as climate dynamics, would be the predominant factors regulating lake primary producers in remote upland lakes and thus, synchronize the dynamic of primary producer assemblages in these basins. We found broad support for the hypotheses pertaining to lowland sites as wastewater treatment was the main predictor of changes to primary producer assemblages in lowland lakes. In contrast, upland headwaters responded weakly to variation in atmospheric temperature, and dynamics in primary producers across upland lakes were asynchronous. Collectively, these findings show that nutrient inputs from point sources overwhelm climatic controls of algae and nuisance cyanobacteria, but highlights that large-scale stressors do not always initiate coherent regional lake response. Furthermore, a lake's position in its landscape, its connectivity and proximity to point nutrients are important determinants of changes in production and composition of phototrophic assemblages.
Open Access
Sedimentary DNA and pigments show increasing abundance and toxicity of cyanoHABs during the Anthropocene
(Wiley, 2023-02-17) Heathcote, Adam J.; Taranu, Zofia E.; Tromas, Nicolas; MacIntyre-Newell, Meaghan; Leavitt, Peter R; Pick, Frances R.
1. Cyanobacterial harmful algal blooms (cyanoHABs) are assumed to be increasing in abundance and toxicity, but comprehensive analysis of change through time is limited, in part, because some key taxa (e.g., Microcystis) leave ambiguous evi- dence of historical abundance and toxicity. Sedimentary DNA (sedDNA) can allow the reconstruction of the cyanobacteria community as well as the frequency of genes specific to cyanotoxin production, enabling us to determine which taxa are present and their potential for toxin-production. 2. Using a combination of droplet digital polymerase chain reaction (ddPCR) and high-throughput sequencing (HTS), we quantified the abundance of cyanobacte- rial genes of known function and changes in cyanobacteria taxa from sedDNA over the last century in nine lakes along a gradient of lake size, depth and trophic state in Minnesota, U.S.A. Using ddPCR, we quantified genes associated with mi- crocystin toxin-producing potential (mcyE), total cyanobacteria (CYA, 16S rRNA) and the genus Microcystis (MICR, 16S rRNA). Using HTS on a subset of lakes, we investigated how the abundance of this toxin-producing gene covaried with the cyanobacteria community composition. We also compared ddPCR and HTS data to fossil pigments, a well-established palaeolimnological method used to track changes in primary producers over time. 3. Our results showed a significant correlation between MICR and the quantity of mcyE gene and cyanobacterial taxa with known toxin- production potential. The abundance of both genes likewise increased concomitantly through time. 4. Community analyses of HTS data showed significant change in cyanobacte- rial communities commencing c. 1950 when major land-use change in this re- gion led to increased lake productivity, and c. 1990 when Dolichospermum and Microcystis genera increased in abundance, and the subtropical exotic cyanobac- teria Raphidiopsis raciborskii and Sphaerospermopsis aphanizomenoides became abundant. Cyanobacteria pigment data reflected these changes only in deeper lakes, suggesting issues related to benthic production or biomarker preservation in shallower systems.