Monitoring and conservation of Mediterranean temporary ponds,,

Temporary ponds are unique freshwater wetlands, characterized by alternating dry and wet phases. They are variable in size, shape, depth and hydroperiod and consequently house diverse plant and animal communities. Temporary ponds are very abundant in Mediterranean regions where they provide several ecosystem services, in particular provisioning services (water supply for livestock, grazing, medicinal plant harvesting, sediment extraction), regulating services (flood control, ground water retention), cultural services (educational, aesthetical and recreational values) and supporting services (soil formation, nutrient cycling and biodiversity). However, Mediterranean temporary ponds (MTP) also entail so-called ecosystem disservices, such as loss of agricultural land or the emergence of mosquitoes. Because of growing anthropogenic pressure due to human activities (such as agriculture, urbanization and recreation), but also climate change, the quality and quantity of MTP is declining at a high rate. In several parts of the world, MTP also generally lack political recognition, mainly caused by a gap of scientific knowledge. In this PhD, we contribute to bridge this knowledge gap by means of an integrated approach. We investigate various natural and anthropogenic factors and their impact on a wide range of faunal and floral groups, by combining several methodological approaches (literature review, field surveys and experimental studies). Firstly, we evaluated the lack of indicators to assess the ecological quality of MTP (Chapter 1). We reviewed a wide range of existing indicators developed for large waterbodies and evaluated whether they could be applied to MTP. We also formulated general recommendations for standardized monitoring based on an extensive literature review. Secondly, we focused on the decline in quantity of MTP in a particular part of the Mediterranean region, northwestern Morocco, where this habitat remains largely unprotected and understudied. An extensive field survey was conducted (spanning 600 km, several climatic regions and altitudes) to update the knowledge on the diversity and distribution of large branchiopods, as flagship species of temporary ponds (Chapter 2). Historical data were available from the 1980’s to allow comparison with our current survey. Fifteen (of the known 17) Moroccan large branchiopod species were recovered during our survey, including two endemic species. Although northwestern Morocco can still be considered as a hotspot for large branchiopods, we found a strong decline in habitat numbers and species richness per habitat over the past 30 years. In a second field survey, we focused on the region of Ben Slimane to determine the ecological quality of MTP along a gradient of anthropogenic pressure (Chapter 3). Over the span of an entire year, we monitored the faunal and floral communities (amphibians, large branchiopods, zooplankton, macroinvertebrate and macrophytes) of 40 MTP, scattered throughout a matrix of different land uses. We found that pond hydroperiod was the key factor shaping communities, with shorter hydroperiods resulting in lower overall biodiversity. Agricultural activities (livestock grazing and crop culturing) can influence the inhabiting communities, mainly by changing local pond factors. Based on our dataset we also identified several indicators to assess the ecological status of the ponds using several classification criteria. We discussed that, mostly due to the buffering effect of forests, the majority of MTP in the region were still in good ecological condition. Ponds with a higher conservational value were characterized by the presence of indicator species such as the near-threatened Spanish ribbed newt and Mediterranean tree frog. We also found that agricultural activities within 30 m around the pond and low amounts (< 60%) of submerged vegetation in the ponds generally indicate a poor ecological quality. In Chapter 4, we examined the effects of the intensive use of an ecosystem service (livestock grazing) on water quality and on faunal and floral communities in outdoor mesocosms. Simulated trampling and feces input strongly affected hatching and germinating communities, while effects on water quality and colonizing macroinvertebrate communities remained limited. However, since livestock also play a role as dispersal vector for passive dispersers, they may still be important for maintaining metacommunity dynamics at the regional scale. In a second mesocosm experiment, we tested the possibility to biologically control mosquitoes in MTP (Chapter 5), as they can act as vectors for arboviruses and spread diseases such as West Nile and Dengue fever. Tadpole shrimp have been suggested to be convenient biological mosquito control agents in temporary ponds, because of their ability to develop simultaneously with mosquitoes. We showed that tadpole shrimp can effectively reduce (up to 95%) mosquito larvae populations. However, they also caused significant side effects on water quality and many non-target species, especially hatching communities, which can eventually trigger a shift in ecosystem functioning. Therefore, we discourage introducing tadpole shrimp in MTP as mosquito control agent. By combining existing literature and new insights, we provided practical monitoring and conservation measures for a continued sustainable management of MTP in the near and long-term future. We suggested monitoring guidelines to reduce sampling efforts and costs, and started developing a tool to determine the ecological quality of northwestern MTP based on indicator species and environmental variables. Lastly, we recommend preserving the natural hydroperiods of MTP, maintaining a 30 m buffer zone around the ponds and partially fencing the pond basins, promoting both biodiversity and ecosystem services of these unique but fragile habitats.status: publishe