Shellfish reefs increase water storage capacity on intertidal flats over extensive spatial scales

Ecosystem engineering species can affect their environment at multiple spatial scales, from the local scale up to a significant distance, by indirectly affecting the surrounding habitats. Structural changes in the landscape can have important consequences for ecosystem functioning, for example, by increasing retention of limiting resources in the system. Yet, it remains poorly understood how extensive the footprint of ecosystem engineers on the landscape is. Using remote sensing techniques, we reveal that depression storage capacity on intertidal flats is greatly enhanced by engineering by shellfish resulting in intertidal pools. Many organisms use such pools to bridge low water events. This storage capacity was significantly higher both locally within the shellfish reef, but also at extensive spatial scales up to 115 m beyond the physical reef borders. Therefore, the footprint of these ecosystem engineers on the landscape was more than 5 times larger than their actual coverage; the shellfish cover approximately 2% of the total intertidal zone, whereas they influence up to approximately 11% of the area by enhancing water storage capacity. We postulate that increased residence time of water due to higher water storage capacity within engineered landscapes is an important determinant of ecosystem functioning that may extend well beyond the case of shellfish reefs provided here

Indicators of Expansion and Retreat of Phragmites Based on Optical and Radar Satellite Remote Sensing: a Case Study on the Danube Delta

Reed is an important wetland species. In some places it provides valuable ecosystem services, while in other places it poses a threat as an invasive species. Thus, monitoring and predicting reed dynamics is crucial. We not only detected changes in reed area using remote sensing, but also developed indicators for the stability of reed wetlands based on remote sensing that would allow to predict its future development. We used satellite imagery to study reed development in the Danube Delta in Romania over a period of 22-years and identified expanding, stable and retreating reedlands. We then compared optical vegetation indices and radar backscatter among those three different reed development categories. We found clear spatial differences in long-term reed dynamics. We also revealed a clear difference in radar backscatter, but no difference in the optical signal of expanding, stable and decreasing reed areas. The radar data showed the largest seasonal variation in locations where reed was expanding and smallest seasonal variation where reed was decreasing. Overall, our study shows that the stability of reed ecosystems, and their services, can be monitored by quantifying seasonal changes in backscatter of reed-lands using radar satellites. This principle looks promising for monitoring other ecosystems as well

Using remote sensing to identify drivers behind spatial patterns in the bio-physical properties of a saltmarsh pioneer

Recently, spatial organization in salt marshes was shown to contain vital information on system resilience. However, in salt marshes, it remains poorly understood what shaping processes regulate spatial patterns in soil or vegetation properties that can be detected in the surface reflectance signal. In this case study we compared the effect on surface reflectance of four major shaping processes: Flooding duration, wave forcing, competition, and creek formation. We applied the ProSail model to a pioneering salt marsh species (Spartina anglica) to identify through which vegetation and soil properties these processes affected reflectance, and used in situ reflectance data at the leaf and canopy scale and satellite data on the canopy scale to identify the spatial patterns in the biophysical characteristics of this salt marsh pioneer in spring. Our results suggest that the spatial patterns in the pioneer zone of the studied salt marsh are mainly caused by the effect of flood duration. Flood duration explained over three times as much of the variation in canopy properties as wave forcing, competition, or creek influence. It particularly affects spatial patterns through canopy properties, especially the leaf area index, while leaf characteristics appear to have a relatively minor effect on reflectance

Indicators of Expansion and Retreat of Phragmites Based on Optical and Radar Satellite Remote Sensing: a Case Study on the Danube Delta

Reed is an important wetland species. In some places it provides valuable ecosystem services, while in other places it poses a threat as an invasive species. Thus, monitoring and predicting reed dynamics is crucial. We not only detected changes in reed area using remote sensing, but also developed indicators for the stability of reed wetlands based on remote sensing that would allow to predict its future development. We used satellite imagery to study reed development in the Danube Delta in Romania over a period of 22-years and identified expanding, stable and retreating reedlands. We then compared optical vegetation indices and radar backscatter among those three different reed development categories. We found clear spatial differences in long-term reed dynamics. We also revealed a clear difference in radar backscatter, but no difference in the optical signal of expanding, stable and decreasing reed areas. The radar data showed the largest seasonal variation in locations where reed was expanding and smallest seasonal variation where reed was decreasing. Overall, our study shows that the stability of reed ecosystems, and their services, can be monitored by quantifying seasonal changes in backscatter of reed-lands using radar satellites. This principle looks promising for monitoring other ecosystems as well

Interactive and independent effects of light and noise pollution on sexual signaling in frogs

Urbanization drastically changes environmental conditions, including the introduction of sensory pollutants, such as artificial light at night (ALAN) and anthropogenic noise. To settle in urban habitats, animals need to cope with this new sensory environment. On a short timescale, animals might cope with sensory pollutants via behavioral adjustments, such as changes in sexual signaling, which can have important fitness consequences. While ALAN and anthropogenic noise generally co-occur in urban habitats and are known to be able to interact to modify behavioral responses, few studies have addressed their combined impact. Our aim was, therefore, to assess the effects of ALAN, anthropogenic noise, and their interaction on sexual signaling in túngara frogs (Engystomops pustulosus). We observed the calling behavior of frogs in urban and forest areas, and subsequently recorded these frogs in a laboratory set-up while independently manipulating light and noise levels. Frogs in urban areas called with a higher call rate and complexity, which was correlated with local sensory conditions. Furthermore, our lab experiment revealed that ALAN can directly alter sexual signaling independently as well as in combination with anthropogenic noise. Exposure to ALAN alone increased call amplitude, whereas a combination of ALAN and anthropogenic noise interacted to lead to a higher call complexity and amplitude. Overall, the response patterns consistently showed that exposure to ALAN and anthropogenic noise led to more conspicuous sexual signals than expected based on the additive effects of single pollutants. Our results support the notion that urban and forest population differences in sexual signaling can be partially explained by exposure to ALAN and anthropogenic noise. Furthermore, by demonstrating interactive effects between light and noise pollution, our study highlights the importance of examining the effects of multisensory pollution, instead of single pollutants, when trying to understand phenotypic divergence in urbanized vs. natural areas

Using Remote Sensing to Identify Drivers behind Spatial Patterns in the Bio-physical Properties of a Saltmarsh Pioneer

Datasets underlying the publication: Using remote sensing to identify drivers behind spatial patterns in the bio-physical properties of a saltmarsh pionee

Indicators of Expansion and Retreat of Phragmites Based on Optical and Radar Satellite Remote Sensing: a Case Study on the Danube Delta

Reed is an important wetland species. In some places it provides valuable ecosystem services, while in other places it poses a threat as an invasive species. Thus, monitoring and predicting reed dynamics is crucial. We not only detected changes in reed area using remote sensing, but also developed indicators for the stability of reed wetlands based on remote sensing that would allow to predict its future development. We used satellite imagery to study reed development in the Danube Delta in Romania over a period of 22-years and identified expanding, stable and retreating reedlands. We then compared optical vegetation indices and radar backscatter among those three different reed development categories. We found clear spatial differences in long-term reed dynamics. We also revealed a clear difference in radar backscatter, but no difference in the optical signal of expanding, stable and decreasing reed areas. The radar data showed the largest seasonal variation in locations where reed was expanding and smallest seasonal variation where reed was decreasing. Overall, our study shows that the stability of reed ecosystems, and their services, can be monitored by quantifying seasonal changes in backscatter of reed-lands using radar satellites. This principle looks promising for monitoring other ecosystems as well

Using remote sensing to identify drivers behind spatial patterns in the bio-physical properties of a saltmarsh pioneer

Recently, spatial organization in salt marshes was shown to contain vital information on system resilience. However, in salt marshes, it remains poorly understood what shaping processes regulate spatial patterns in soil or vegetation properties that can be detected in the surface reflectance signal. In this case study we compared the effect on surface reflectance of four major shaping processes: Flooding duration, wave forcing, competition, and creek formation. We applied the ProSail model to a pioneering salt marsh species (Spartina anglica) to identify through which vegetation and soil properties these processes affected reflectance, and used in situ reflectance data at the leaf and canopy scale and satellite data on the canopy scale to identify the spatial patterns in the biophysical characteristics of this salt marsh pioneer in spring. Our results suggest that the spatial patterns in the pioneer zone of the studied salt marsh are mainly caused by the effect of flood duration. Flood duration explained over three times as much of the variation in canopy properties as wave forcing, competition, or creek influence. It particularly affects spatial patterns through canopy properties, especially the leaf area index, while leaf characteristics appear to have a relatively minor effect on reflectance

Data presented in the paper "Quantifying bed level change at the transition of tidal flat and salt marsh: can we understand the lateral location of the marsh edge?"

Bed level dynamics at the interface of the salt marsh and tidal flat have been highlighted as a key factor connecting the long-term bio-geomorphological development of the marsh to large-scale physical forcing. Hence, we aim to obtain insight into the factors confining the location of the marsh edge (i.e., boundary between tidal flat and salt marsh). A unique dataset was collected, containing measurements of daily bed level changes (i.e., integrative result of physical forcing and sediment properties) at six intertidal transects in the North Sea area. Moreover, various biophysical parameters were measured, such as sediment characteristics, waves, inundation time and chlorophyll-a levels

Synchronized high-resolution bed-level change and biophysical data from 10 marsh-mudflat sites in northwestern Europe

Tidal flats provide valuable ecosystem services such as flood protection and carbon sequestration. Erosion and accretion processes govern the ecogeomorphic evolution of intertidal ecosystems (marshes and bare flats) and, hence, substantially affect their valuable ecosystem services. To understand the intertidal ecosystem development, high-frequency bed-level change data are thus needed. However, such datasets are scarce due to the lack of suitable methods that do not involve excessive labour and/or costly instruments. By applying newly developed surface elevation dynamics (SED) sensors, we obtained unique high-resolution daily bed-level change datasets in the period 2013-2017 from 10 marsh-mudflat sites situated in the Netherlands, Belgium, and the United Kingdom in contrasting physical and biological settings. At each site, multiple sensors were deployed for 9-20 months to ensure sufficient spatial and temporal coverage of highly variable bed-level change processes. The bed-level change data are provided with synchronized hydrodynamic data, i.e. water level, wave height, tidal current velocity, medium sediment grain size (D50), and chlorophyll a level at four sites. This dataset has revealed diverse spatial morphodynamics patterns over daily to seasonal scales, which are valuable to theoretical and model development. On the daily scale, this dataset is particularly instructive, as it includes a number of storm events, the response to which can be detected in the bed-level change observations. Such data are rare but useful to study tidal flat response to highly energetic conditions. The dataset is available from 4TU.ResearchData (https://doi.org/10.4121/12693254.v4; Hu et al., 2020), which is expected to expand with additional SED sensor data from ongoing and planned surveys