Assessing the status of shallow lakes using an additive model of biomass size spectra

peer-reviewed1. Planktonic biomass size spectra were used to summarise the ecological quality of six shallow lakes sampled in spring, early summer and late summer. 2. A simple additive model fitted to the data was used to assess the applicability of the size spectrum theory to shallow lake ecosystems. 3. The additive model replicated the hierarchical pattern of biomass predicted by the predator-prey theory of aquatic production, and was a more appropriate model for predicting biomass size spectra than the frequently used linear regression. 4. Lakes with varying ecological quality were a significant source of variation in the additive model, and further research into using size spectra to monitor ecological quality in shallow lakes is warranted. Specifically, the production of size spectra from a wider range of sites is needed to provide greater statistical validation. 5. The use of size spectra can provide an attractive and cost-effective way for classifying lake ecosystems because it circumvents the need for difficult taxonomic description

Population specific smolt development, migration and maturity schedules in Atlantic salmon in a natural river environment

NOTICE: this is the author’s version of a work that was accepted for publication in Aquaculture. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Aquaculture, [Volume 273, Issues 2-3, (December 2007)] doi:10.1016/j.aquaculture.2007.10.008 http://www.sciencedirect.com/science/article/pii/S0044848607009428peer-reviewedIdentifying differences in quantitative life history traits between cultured and native or non-native wild populations is important in assessing the impact of accidental and deliberate introductions of hatchery-reared fish into the wild. As the ability to exploit the marine environment is the defining life history characteristic of anadromous salmonids, knowledge of variation in smoltification characteristics among populations is crucial in determining how these introductions affect fitness in recipient populations. Data are presented here describing the timing and extent of the autumn migration; the propensity for male parr maturation; the timing of the spring migration; and the size of autumn and spring migrants from Atlantic salmon (Salmo salar) populations from various genetic backgrounds. These experiments were carried out under common garden conditions over a decade in the Srahrevagh River in the west of Ireland. Population specific genetically determined differences in quantitative life history traits associated with smoltification were apparent. These differences may reflect smolt quality and therefore impact on marine survival and ultimately lifetime fitness. Both hatchery domestication and geography (different selective environments) were found to be important factors determining smolt phenotypes, although it was difficult to measure the relative contribution of each. These results indicate that farm, native hatchery, non-native wild salmon (even from a neighbouring catchment) and their hybrids with native wild fish, are likely to produce less well adapted and thus poorer quality smolts than native wild populations and, where wild populations are extant, such stocks should not be used for enhancement purposes

Anthropocene environmental change in an internationally important oligotrophic catchment on the Atlantic seaboard of western Europe

Oligotrophic catchments with short spatey streams, upland lakes and peaty soils characterise northwest European Atlantic coastal regions. These catchments are important biodiversity refuges, particularly for sensitive diadromous fish populations but are subject to changes in land use and land management practices associated with afforestation, agriculture and rural development. Quantification of the degree of catchment degradation resulting from such anthropogenic impacts is often limited by a lack of long-term baseline data in what are generally relatively isolated, poorly studied catchments. This research uses a combination of palaeolimnological (radiometrically-dated variations in sedimentary geochemical elements, pollen, diatoms and remains of cladocera), census, and instrumental data, along with hindcast estimates to quantify environmental changes and their aquatic impacts since the late 19th century. The most likely drivers of any change are also identified. Results confirm an aquatic biotic response (phyto- and zooplankton) to soil erosion and nutrient enrichment associated with the onset of commercial conifer afforestation, effects that were subsequently enhanced as a result of increased overgrazing in the catchment and, possibly, climate warming. The implications for the health of aquatic resources in the catchment are discussedEnvironmental Protection Agency in Ireland (ILLUMINATE 2005-W-MS-40, P.McGinnity was supported by the Beaufort Marine Research Award in Fish Population Genetics funded by the Irish Government under the Sea Change Programme

RESCALE: Review and Simulate Climate and Catchment Responses at Burrishoole

The climate of the Burrishoole catchment is projected to change significantly over the present century. Previous research of the catchment identified a scientific gap in knowledge in terms of understanding the implications of present and projected future changes in stream flow, water temperature, pH levels and DO concentrations on fish productivity in the catchment. To address this, a multidisciplinary team of scientists undertook an analysis of both present and likely future climate impacts on the catchment with a view to furthering the understanding of the inter-linkages between climate, climate change, and the freshwater ecosystem. The research findings outlined in the report provide climate change information at the catchment scale to assist catchment stakeholders in integrating climate change considerations into their decision-making processes. The report presents an in-depth assessment of the climate and environmental datasets from the catchment to establish if changes have occurred over the period of record. In order to assess the likely impacts of future changes in climate on the catchment, regional climate projections were developed and subsequently employed to simulate likely responses in stream flow and temperature, DOC and DO for the present century. The projected changes in both the climate and water-quality were then used to provide a basis for assessing impacts on fish growth and survival rates of salmonid and eel species in the catchment. The report provides a useful template for future studies, not just in the Burrishoole catchment but for other ecologically important catchments. The findings from the report are relevant to policy makers at the national scale; catchment managers at the regional scale; and, specifically, to stakeholders in the Burrishoole catchment, in developing adaptive responses to climate change.Funded under the Marine Research Sub-programme of the National Development Plan (2007-’13), as part of the Sea Change Strategy.Funder: Marine Institut

Abundance and biogeography of methanogenic and methanotrophic microorganisms across European streams

Aim Although running waters are getting recognized as important methane sources, large-scale geographical patterns of microorganisms controlling the net methane balance of streams are still unknown. Here we aim at describing community compositions of methanogenic and methanotrophic microorganisms at large spatial scales and at linking their abundances to potential sediment methane production (PMP) and oxidation rates (PMO). Location The study spans across 16 European streams from northern Spain to northern Sweden and from western Ireland to western Bulgaria. Taxon Methanogenic archaea and methane-oxidizing microorganisms. Methods To provide a geographical overview of both groups in a single approach, microbial communities and abundances were investigated via 16S rRNA gene sequencing, extracting relevant OTUs based on literature; both groups were quantified via quantitative PCR targeting mcrA and pmoA genes and studied in relation to environmental parameters, sediment PMP and PMO, and land-use. Results Diversity of methanogenic archaea was higher in warmer streams and of methanotrophic communities in southern sampling sites and in larger streams. Anthropogenically-altered, warm and oxygen-poor streams were dominated by the highly efficient methanogenic families Methanospirillaceae, Methanosarcinaceae, and Methanobacteriaceae, but did not harbor any specific methanotrophic organisms. Contrastingly, sediment communities in colder, oxygen-rich waters with little anthropogenic impact were characterised by methanogenic Methanosaetaceae, Methanocellaceae and Methanoflorentaceae and methanotrophic Methylococcaceae and Cd. Methanoperedens. Representatives of the methanotrophic Crenotrichaceae and Methylococcaceae as well as the methanogenic Methanoregulaceae were characteristic for environments with larger catchment area and higher discharge. PMP increased with increasing abundance of methanogenic archaea, while PMO rates did not show correlations with abundances of methane oxidizing bacteria. Main conclusions Methanogenic and methanotrophic communities grouping into three habitat types suggest that future climate- and land-use changes may influence the prevailing microbes involved in the large-scale stream-related methane cycle, favoring the growth of highly efficient hydrogenotrophic methane-producers. Based on these results, we expect global change effect on PMP rates to especially impact rivers adjacent to anthropogenically disturbed land-uses