Enrique Reyes’s research while affiliated with East Carolina University and other places

Marsh restoration is an effective tool to remove water and soil metals via plant uptake and soil accumulation. However, few studies have attempted to quantify metal accumulation and removal in Mediterranean restored marshes. This study aimed to assess changes in water and soil metals in an oligohaline-restored marsh experiment that was set in an abandoned rice field for 3 years. Two freshwater-type treatments were tested: river irrigation water (IW) and rice field drainage water (DW), as well as three water level management schemes. Differences in water level schemes did not cause significant differences in metal removal and accumulation in soil marshes in either water type treatment. However, results showed that significantly higher Mn, Pb, and Zn input concentrations from DW allowed higher mean percentage of concentration reduction. Higher Cu concentration from IWalso allowed higher Cu reduction (85%). Mean values of Co, Cr, Cu, Ni, Pb, V, and Zn in soil were higher in the IWtreatment characterized by higher plant biomass, whereasmean accumulation rates of As, Ba, Cr, Cu, Ni, Pb, V, and Zn were higher in the DWtreatment with higher accretion rates. Results suggest that wetland plants likely favored soil metal adsorption through soil oxygenation and highlight the utility of restored marshes as pollution filters in coastal wetlands with significant soil accretion and subject to relative sea level rise. Key words: Ebro Delta, heavy metals, metal removal, Paspalum distichum L., restored marsh, soil accretion

The zebra mussel, Dreissena polymorpha, is among the most invasive organisms worldwide, with well-documented economic and ecological impacts. In Spain, it was first detected in the Riba-roja Reservoir (Ebro River) in the summer of 2001. Although it has been suggested that mussel density determines its invasiveness and impact, there are few studies on what factors are responsible for population dynamics (i.e.; variations over space and time). The model used here was able to reproduce all population dynamics previously described in the literature; therefore, it was used to predict future mussel population trends within the Riba-roja Reservoir and test the usefulness of water-level fluctuations as a mussel management tool. Carrying capacity was based on total phosphorus concentration and was found to control peak density. Consequently, if the decrease in phosphorus observed in the basin remains at its present level, an increase in mussel density is not expected. A decrease in the water level (simulated through an increment in mortality rates) had a significant effect on mussel dynamics. Population response was related to mussel density, age-class composition, and its reproductive cycle. Population response capability was reduced outside of the spawning season and effects were higher when two water releases were combined, one before the spawning season and a second after the next spawning season. Model predictions at a local scale may be helpful in developing adequate control plans by both predicting future species trends and forecasting management effects.

Eutrophication is now a serious environmental problem worldwide because it disrupts the metabolism of aquatic ecosystems. In the Ebro Delta, intensive rice farming during the 20th century has increased coastal eutrophication and caused ecological and economic impacts. Marsh restoration is as an effective economic and ecological tool to remove nutrients from agricultural runoff, thereby limiting coastal eutrophication impacts and also providing other ecosystem services. The objective of this experimental study was to assess overall N and P concentration reduction, C accumulation and Si buffering in an oligohaline restored marsh receiving nutrient and sediment inputs from river irrigation and rice field drainage waters under different water levels. We established the experimental restored marsh in abandoned deltaic rice fields from August 2009 to June 2012. The study of changes in nutrient concentration was performed in 2010 from June to November. The study of nutrient and carbon accumulation was performed from August 2009 to May 2011. We used two freshwater input type treatments (riverine irrigation and rice field drainage water) and three water level treatments (10, 20 and 30 cm). Our results showed that higher water nutrient concentrations from rice fields caused significantly higher N- NH4+ and P- PO43− concentration reduction (80.76 ± 1.8% and 17.99 ± 3.92% respectively). There was also an export in TP and P- PO43− (−45.08 ± 13.12 and −23.85 ± 8.15%, respectively) in experimental marsh units receiving river irrigation waters. Significantly lower soil redox conditions and higher total maximum aboveground biomass in the IW treatment were associated with lower N- NO3− concentration reduction and higher Si-SiO2 concentration reduction (94.14 ± 0.72% and 58.54 ± 1.08% respectively) than the DW treatment. Higher sediment concentrations from rice fields were associated with higher C accumulation rates (126.10 ± 6.25 g m−2 y−1) compared with experimental marsh units receiving river irrigation waters (99.44 ± 8.23 g m−2 y−1). Higher water levels also increased significantly P- PO43− and Si-SiO2 concentration reduction and C accumulation rates within both water type treatments. Our experimental study showed how multiple mechanisms control N and P concentration reduction, Si buffering and C accumulation. Plant growth may decrease the ability to reduce the input concentration of N- NO3− possibly due to denitrification inhibition via plant oxygenation of marsh soils. Plant uptake may favor Si buffering in the restored marsh, although high water levels may also control Si buffering through higher residence time for diatom uptake. This study indicates that Mediterranean oligohaline restored marshes removed N and P using both river irrigation and rice field drainage waters and also provide C accumulation and Si buffering services. The use of agriculture runoff as a primary source of nutrient and sediment is beneficial for marsh restoration projects focused on C accumulation. In general, higher water levels (20–30 cm) were better for nutrient concentration reduction and C accumulation, but higher water levels were also associated with lower plant biomass.

The Ebro Delta (Spain) is among the most important marsh areas in the Western Mediterranean Sea. Fluvial sediment reduction by dams in a relative sea-level rise (RSLR) scenario has increased the delta plain flooding risk. The objective of this study was to assess factors controlling of marsh elevation and C accumulation in a Mediterranean oligohaline restored marsh. We conducted a 3-year experimental field study in a newly established restored marsh using two different freshwater input types, riverine irrigation water (IW) and rice field drainage water (DW) and three water levels (10, 20 and 30 cm depth). This study indicates that Mediterranean restored marshes might deal with flooding risk due to high mean rates of vertical accretion (11.5±0.8 and 15.5±0.6 mm yr-1) and elevation change (9.1±1.4 and 8.8±2.8 mm yr-1) in both IW and DW treatments. Rice field drainage waters provided higher sediments to the restored marsh, which in turn promoted C accumulation showing in both water type treatments (99.44 and 126.10 g m-2 yr-1) similar values to global estimates for freshwater marshes. This research supports that the use of rice field drainage waters as a source of sediments as beneficial for marsh restoration focused on marsh elevation and C accumulation.

The Ebro Delta (Spain) is among the most important marsh areas in the Western Mediterranean Sea. Fluvial sediment reduction by dams in a relative sea-level rise (RSLR) scenario has increased the delta plain flooding risk. The objective of this study was to assess factors controlling of marsh elevation and C accumulation in a Mediterranean oligohaline restored marsh. We conducted a 3-year experimental field study in a newly established restored marsh using two different freshwater input types, riverine irrigation water (IW) and rice field drainage water (DW) and three water levels (10, 20 and 30 cm depth). This study indicates that Mediterranean restored marshes might deal with flooding risk due to high mean rates of vertical accretion (11.5±0.8 and 15.5±0.6 mm yr-1) and elevation change (9.1±1.4 and 8.8±2.8 mm yr-1) in both IW and DW treatments. Rice field drainage waters provided higher sediments to the restored marsh, which in turn promoted C accumulation showing in both water type treatments (99.44 and 126.10 g m-2 yr-1) similar values to global estimates for freshwater marshes. This research supports that the use of rice field drainage waters as a source of sediments as beneficial for marsh restoration focused on marsh elevation and C accumulation.

The response of deltas to sea level rise (SLR) has mostly been studied from a perspective of human impacts like global warming and impoundment, or from a perspective of natural changes associated with glacial cycles. Here we synthesize the response of deltas to SLR by integrating research looking at past and future evolution to improve the potential to manage deltas to adapt to high rates of SLR. We hypothesize that fluvial-dominated deltas can be managed to survive high rates of SLR (>1 cm year−1) that characterized the post-glacial period and will likely characterize coming centuries due to global warming. There are three known mechanisms for deltas to cope with SLR that are self-reinforcing as the rates increase, tending to enhance the efficiency of the deltaic sedimentary trap:

The Ebro Delta (Catalonia, Spain) is one of the most valuable coastal zones within the Mediterranean Sea, supporting a highly productive rice agricultural system, as well as a myriad of coastal marsh habitats. However, chronic reductions of fluvial sediments coupled with accelerated relative sea level rise (RSLR) have created an environment where approximately half of the Ebro Delta is now vulnerable to flooding. To assess RSLR mitigation using marsh restoration within abandoned deltaic rice fields, we established an experimental-field study over 3 years. We used two freshwater types (riverine irrigation and rice field drainage water) and three water levels (10, 20 and 30 cm deep). Our hypotheses were that vertical accretion (VA) and elevation change (EC) in oligohaline restored marshes would be primarily controlled by organic contribution, and both would have higher rates than predicted RSLR in Ebro Delta (5-8 mm yr-1) under current low sediment availability conditions. VA (but not EC) was significantly higher in drainage water treatments receiving significantly higher sediment input and had higher mean values in both water types (11.5 and 15.5 mm yr-1) than elevation change (9.1 and 8.8 mm yr-1). However, experimental units with significantly higher belowground biomass had higher EC (11.3 and 17.8 mm yr-1) than VA (8.3 and 15.1 mm yr-1) in both water types due to high weed colonization by Paspalum distichum. These results showed that mineral contribution was generally higher than organic contribution to VA and EC, although P. distichum highly promoted elevation gain by root growth. The results supported the hypothesis that oligohaline restored marshes often had elevation gains higher than predicted RSLR at least during the initial marsh development. This study indicates that the use of agricultural runoff as primary source of sediment, nutrient, and freshwater is beneficial for marsh restoration projects focused on mitigating RSLR and other climate change impacts.