Aquaculture induced erosion of tropical coastlines throws coastal communities back into poverty

Shallow tropical coastlines harbour unique mangrove ecosystems, which support livelihoods and provide a natural barrier against coastal flooding. Non-sustainable land-use practices, such as large-scale clear cutting of mangroves for aquaculture, ground water withdrawal and alteration of river flows, result in rapid subsidence. The collapse of aquaculture production, due to pollution and disease, is followed by coastal erosion, damage to infrastructure, intrusion of salt water and coastal flooding. Standard engineered interventions for protection often fail or are extremely expensive in these soft muddy environments. Subsidence and erosion render re-planting of mangroves in front of retreating coastlines impossible. Short-term solutions should focus on restoration of abiotic conditions, such as hydrology and sediment fluxes, to facilitate rapid establishment of protective mangrove belts. However, to ensure long-term sustainability, improved governance frameworks are required that put in place criteria for sustainable aquaculture, guide coastal infrastructure designs and limit ground water extraction

UvA-DARE (Digital Academic Repository) The influence of bioturbation on the vertical distribution of soil organic matter in volcanic ash soils: a case study in northern Ecuador

Summary Soil faunal bioturbation ('bioturbation') is often cited as a major process influencing the vertical distribution of soil organic matter (SOM). The influence of bioturbation on vertical SOM transport is complex because it is the result of interaction between different groups of soil faunal species that redistribute SOM through the soil profile in distinct ways. We performed a semi-quantitative micromorphological analysis of soil faunal pedofeatures and related their occurrence to the vertical distribution of SOM and highresolution radiocarbon dating in volcanic ash soils under montane forest and grassland (pa´ramo) vegetation in the northern Ecuadorian Andes. The pa´ramo soil data suggest that bioturbation was largely responsible for the vertical distribution of SOM, while illuviation and root input were of minor importance. Bioturbation was caused by endogeic species, which typically mix the soil only over short vertical distances. Short vertical distance mixing was apparently enhanced by the upward shifting of bioturbation as a result of soil thickening due to SOM accumulation. A change from pa´ramo to forest vegetation was accompanied by a change from endogeic to epigeic species. As these latter species do not redistribute material vertically, this eventually resulted in the formation of thick ectorganic horizons in the forest

How much does the presence of a competitor modify the within-canopy distribution of ozone-induced senescence and visible injury?

Many natural vegetation species have been shown to be negatively affected by ozone. This study has investigated how the presence of competing species in a community affects two common responses to ozone: visible injury and senescence. Monocultures and mixtures of Trifolium repens and Lolium perenne were grown in large containers and were exposed in solardomes to either a rural episodic ozone profile (AOT40 of 12.86 ppm h) or control conditions (AOT40 of 0.02 ppm h) for 12 weeks. The proportion of ozone-injured or senesced leaves was different in the different regions of the canopy. The highest proportions of injured/senesced leaves were in the plant material growing at the edge of the canopy and the upper canopy, with a significantly lower proportion of injured leaves in the inner canopy. The presence of L. perenne increased the proportion of ozone-injured leaves in T. repens at the final harvest, whilst the presence of T. repens decreased the proportion of senesced leaves in L. perenne. In L. perenne, the proportion of injured leaves at the edge and inner canopy decreased significantly when grown in competition, whilst for T. repens the reverse effect occurred in the inner canopy only. Different mechanisms appeared to influence the interaction between response to ozone and competitors in these two species. In L. perenne the response to ozone may have been related to nitrogen supply, whereas in T. repens canopy structure was more important