Final report on project SP1210: Lowland peatland systems in England and Wales – evaluating greenhouse gas fluxes and carbon balances

Lowland peatlands represent one of the most carbon-rich ecosystems in the UK. As a result of widespread habitat modification and drainage to support agriculture and peat extraction, they have been converted from natural carbon sinks into major carbon sources, and are now amongst the largest sources of greenhouse gas (GHG) emissions from the UK land-use sector. Despite this, they have previously received relatively little policy attention, and measures to reduce GHG emissions either through re-wetting and restoration or improved management of agricultural land remain at a relatively early stage. In part, this has stemmed from a lack of reliable measurements on the carbon and GHG balance of UK lowland peatlands. This project aimed to address this evidence gap via an unprecedented programme of consistent, multi year field measurements at a total of 15 lowland peatland sites in England and Wales, ranging from conservation managed ‘near-natural’ ecosystems to intensively managed agricultural and extraction sites. The use of standardised measurement and data analysis protocols allowed the magnitude of GHG emissions and removals by peatlands to be quantified across this heterogeneous data set, and for controlling factors to be identified. The network of seven flux towers established during the project is believed to be unique on peatlands globally, and has provided new insights into the processes the control GHG fluxes in lowland peatlands. The work undertaken is intended to support the future development and implementation of agricultural management and restoration measures aimed at reducing the contribution of these important ecosystems to UK GHG emissions

Developing observational methods to drive future hydrological science: can we make a start as a community?

Hydrology is still, and for good reasons, an inexact science, even if evolving hydrological understanding has provided a basis for improved water management for at least the last three millennia. The limitations of that understanding have, however, become much more apparent and important in the last century as the pressures of increasing populations, and the anthropogenic impacts on catchment forcing and responses, have intensified. At the same time, the sophistication of hydrological analyses and models has been developing rapidly, often driven more by the availability of computational power and geographical data sets than any real increases in understanding of hydrological processes. This sophistication has created an illusion of real progress but a case can be made that we are still rather muddling along, limited by the significant uncertainties in hydrological observations, knowledge of catchment characteristics and related gaps in conceptual understanding, particularly of the sub-surface. These knowledge gaps are illustrated by the fact that for many catchments we cannot close the water balance without significant uncertainty, uncertainty that is often neglected in evaluating models for practical applications

Evaluating Temporal Consistency in Marine Biodiversity Hotspots

With the ongoing crisis of biodiversity loss and limited resources for conservation, the concept of biodiversity hotspots has been useful in determining conservation priority areas. However, there has been limited research into how temporal variability in biodiversity may influence conservation area prioritization. To address this information gap, we present an approach to evaluate the temporal consistency of biodiversity hotspots in large marine ecosystems. Using a large scale, public monitoring dataset collected over an eight year period off the US Pacific Coast, we developed a methodological approach for avoiding biases associated with hotspot delineation. We aggregated benthic fish species data from research trawls and calculated mean hotspot thresholds for fish species richness and Shannon’s diversity indices over the eight year dataset. We used a spatial frequency distribution method to assign hotspot designations to the grid cells annually. We found no areas containing consistently high biodiversity through the entire study period based on the mean thresholds, and no grid cell was designated as a hotspot for greater than 50% of the time-series. To test if our approach was sensitive to sampling effort and the geographic extent of the survey, we followed a similar routine for the northern region of the survey area. Our finding of low consistency in benthic fish biodiversity hotspots over time was upheld, regardless of biodiversity metric used, whether thresholds were calculated per year or across all years, or the spatial extent for which we calculated thresholds and identified hotspots. Our results suggest that static measures of benthic fish biodiversity off the US West Coast are insufficient for identification of hotspots and that long-term data are required to appropriately identify patterns of high temporal variability in biodiversity for these highly mobile taxa. Given that ecological communities are responding to a changing climate and other environmental perturbations, our work highlights the need for scientists and conservation managers to consider both spatial and temporal dynamics when designating biodiversity hotspots

Patterns and Variation in Benthic Biodiversity in a Large Marine Ecosystem

While there is a persistent inverse relationship between latitude and species diversity across many taxa and ecosystems, deviations from this norm offer an opportunity to understand the conditions that contribute to large-scale diversity patterns. Marine systems, in particular, provide such an opportunity, as marine diversity does not always follow a strict latitudinal gradient, perhaps because several hypothesized drivers of the latitudinal diversity gradient are uncorrelated in marine systems. We used a large scale public monitoring dataset collected over an eight year period to examine benthic marine faunal biodiversity patterns for the continental shelf (55–183 m depth) and slope habitats (184–1280 m depth) off the US West Coast (47°20′N—32°40′N). We specifically asked whether marine biodiversity followed a strict latitudinal gradient, and if these latitudinal patterns varied across depth, in different benthic substrates, and over ecological time scales. Further, we subdivided our study area into three smaller regions to test whether coast-wide patterns of biodiversity held at regional scales, where local oceanographic processes tend to influence community structure and function. Overall, we found complex patterns of biodiversity on both the coast-wide and regional scales that differed by taxonomic group. Importantly, marine biodiversity was not always highest at low latitudes. We found that latitude, depth, substrate, and year were all important descriptors of fish and invertebrate diversity. Invertebrate richness and taxonomic diversity were highest at high latitudes and in deeper waters. Fish richness also increased with latitude, but exhibited a hump-shaped relationship with depth, increasing with depth up to the continental shelf break, ~200 m depth, and then decreasing in deeper waters. We found relationships between fish taxonomic and functional diversity and latitude, depth, substrate, and time at the regional scale, but not at the coast-wide scale, suggesting that coast-wide patterns can obscure important correlates at smaller scales. Our study provides insight into complex diversity patterns of the deep water soft substrate benthic ecosystems off the US West Coast

Potential contaminant release from agricultural soil and dredged sediment following managed realignment

Purpose Laboratory experiments were conducted to examine the potential for metal (Cu, Ni and Zn) and herbicide (simazine, atrazine and diuron) release from agricultural soil and dredged sediment in managed realignment sites following tidal inundation. Materials and methods Column microcosm and batch sorption experiments were carried out at low (5 practical salinity units, psu) and high (20 psu) salinity to evaluate the changes in the partitioning of metals and herbicides between the soil/sediment and the aqueous phase, and the release of metals and herbicides from soil/sediment to the overlying water column. Results and discussion For both the metals and herbicides, the highest contaminant loads were released from the sediment within the first 24 h of inundation suggesting that any negative impacts to overlying water quality in a managed realignment scheme will be relatively short term following tidal inundation of soil and sediment. The release of metals was found to be dependent on a combination of salinity effects and the strength of binding of the metals to the soil and sediment. In the case of the herbicides, salinity impacted on their release. Particulate organic carbon was found to control the binding and release of the herbicides, highlighting the importance of assessing soil and sediment organic matter content when planning managed realignment sites. Conclusions Our research demonstrates that metals and herbicides may be released from contaminated sediments and agricultural soils during initial periods of flooding by seawater in managed realignment sites

Sediment characteristics of a restored saltmarsh and mudflat in a managed realignment scheme in Southeast England

Sediment characteristics and vegetation composition were measured in a restored and natural saltmarsh and mudflat at Wallasea Island managed realignment scheme (Essex, UK) from January to December 2007. The similar sediment characteristics in the restored and natural mudflat indicated that the sediment in the restored mudflat was approaching natural conditions. However, the sediment characteristics in the restored saltmarsh were not becoming similar to those in the natural saltmarsh. The sediment moisture content, organic matter content and porosity were lower while the sediment bulk density, salinity and pH were higher in the restored compared to the natural saltmarsh. The dissimilarities were mainly due to differences in the vegetation abundance and organic matter content. Although, 18 months after restoration the restored saltmarsh was only sparsely vegetated and there was no net change in the sediment characteristics, the occurrence of Salicornia europaea L. demonstrated that pioneer saltmarsh vegetation establishment preceded the development of sediment characteristics

Methane ebullition from two lowland floodplain fens

This dataset includes measurements of methane fluxes from two lowland floodplain fen sites in East Anglia, UK under conservation management (Sutton and Strumpshaw Fens). The data were collected on seven monthly to bimonthly visits during 2013 and comprise methane ebullition fluxes measured using inverted funnels, and methane fluxes measured using static chambers. The tall, static chambers captured methane transported by diffusion, plant-mediated transport and steady ebullition, whereas the inverted funnels captured methane transported by steady and episodic ebullition. The dataset also includes measurements of water level and meteorological variables (net radiation, soil temperature, air pressure) along with an allometric measure of plant biomass (Vascular Green Area)

In situ measurement of redox sensitive solutes at high spatial resolution in a riverbed using Diffusive Equilibrium in Thin Films (DET)

Here we evaluate a new field methodology for the deployment of Diffusive Equilibrium in Thin Films (DET, protected in stainless steel holders) in coarse riverbed sediments based on that originally developed for fine-grained sediments and soils. Concentration gradients of NO 3 -, NH 4 + and dissolved Mn were measured at cm resolution. We observed fine scale changes in NO 3 -, NH 4 +, and Mn concentrations in the river bed (0-30cm) that were only evident at high resolution and compared them to profiles of NO 3 - and NH 4 + obtained with low resolution multilevel piezometers. The range in concentrations of NO 3 - and NH 4 + measured through DET was larger than those measured at coarse resolution through pore water sampling from multilevel piezometer in the riverbed over the 30cm depth. According to the results, high resolution profiles of redox sensitive chemical species in riverbeds could help in identifying and resolving hotspots of biogeochemical activity. Measurements of NH 4 + using DET were higher than measurements in pore water collected from the multilevel samplers. Further studies are needed to establish whether there is a systematic bias associated with either procedure for the measurement of NH 4 +.</p

In situ measurement of redox sensitive solutes at high spatial resolution in a riverbed using Diffusive Equilibrium in Thin Films (DET)

Here we evaluate a new field methodology for the deployment of Diffusive Equilibrium in Thin Films (DET, protected in stainless steel holders) in coarse riverbed sediments based on that originally developed for fine-grained sediments and soils. Concentration gradients of NO 3 -, NH 4 + and dissolved Mn were measured at cm resolution. We observed fine scale changes in NO 3 -, NH 4 +, and Mn concentrations in the river bed (0-30cm) that were only evident at high resolution and compared them to profiles of NO 3 - and NH 4 + obtained with low resolution multilevel piezometers. The range in concentrations of NO 3 - and NH 4 + measured through DET was larger than those measured at coarse resolution through pore water sampling from multilevel piezometer in the riverbed over the 30cm depth. According to the results, high resolution profiles of redox sensitive chemical species in riverbeds could help in identifying and resolving hotspots of biogeochemical activity. Measurements of NH 4 + using DET were higher than measurements in pore water collected from the multilevel samplers. Further studies are needed to establish whether there is a systematic bias associated with either procedure for the measurement of NH 4 +.</p

The Hyporheic Handbook: a handbook on the groundwater-surface water interface and hyporheic zone for environment managers

Buss, S., Cai, Z., Cardenas, B., Fleckenstein, J., Hannah, D., Heppell, K., …Wood, P. (2009). The Hyporheic Handbook: a handbook on the groundwater-surface water interface and hyporheic zone for environment managers. Bristol: Environment Agency