Ecosystem services and biodiversity crisis across mountain lakes
Lead Author: CNR
Contributors: A. Provenzale (CNR), S. Giamberini (CNR), I. Baneschi (CNR), S. Imperio (CNR), D. Markovic (UP), U. Scharfenberger (UP), Orhideja Tasevska (HIO), Ruth Sonnenschein (EURAC)
Mountain lakes are usually oligotrophic and host specialized ecosystems, which are rich in endemic species. The limited species range, paired with increasing pressures on ecosystems, makes the biodiversity of mountain lakes particularly sensitive to environmental and climate changes. Given that one of the primary species response to changing conditions is a shift in geographic distribution, the lake watershed isolation may force species adaptation or, ultimately, extinction.
The major threats to the biodiversity of mountain lakes are growth in tourism, rapid urbanization, pollution, land use intensification, water uptake, progressing eutrophication, introduction of alien species and climate change, with different importance in different Protected Areas. Typical phenological responses to changing conditions include shifts in timing, magnitude and duration of phytoplankton blooms, as well as altered community composition (cf. Palmer et al., 2015). The latter can lead to changes in the water quality and a decrease in the overall biodiversity, thus threatening established links across trophic levels and, potentially, implying a loss in ecosystem services. Similarly, the introduction of allochthonous fish (often done for recreation purposes) can lead to the disappearance of larger zooplankton species (such as Daphnia spp.) with a change in the overall ecosystem structure and loss of invertebrates and amphibians, as documented in some high-altitude oligotrophic lakes in the Gran Paradiso National Park (GPNP), Italy (Tiberti et al., 2013). For transboundary mountain lakes, such as Prespa and Ohrid lakes (shared between FYR of Macedonia, Greece and Albania), the situation is even more complex. The two lakes are subjected to a broad range of management concerns including transnational management, recreation/tourism, water supply and biodiversity protection. Though considerable efforts have been undertaken to reduce pollution and to protect flagship species, Lake Ohrid is facing a “biodiversity crisis” (Albrecht and Wilke, 2008). Given that Lake Ohrid has a surface area of 358 km2 and 212 known endemic species (e.g. the Ohrid Trout, Salmo letnica), probably it is the most diverse lake in the world (Albrecht and Wilke, 2008), and it is clear that efforts must be made to reverse this ongoing "biodiversity crisis".
Preserving and improving the benefits provided by mountain ecosystems requires information regarding the level of ongoing changes as well as scenario to estimate possible future developments. In particular, management of freshwater ecosystems generally relies on the availability of accurate in situ measurements and analyses of water samples. For most lakes at GPNP as well as for Ohrid and Prespa, many data on the physical, chemical and biological properties of the lake waters are available. In-situ data, however, give information only for a point in time and space, thus providing limited information on spatial and temporal changes of environmental parameters across surface waters. Both, endemism and phenology features commonly occur at different spatial scales, ranging from features occurring only in certain watershed parts to features occurring across the whole watershed. The high spatial resolution of satellite images allows for the estimation of water quality and hydrological parameters, such as chlorophyll concentration, Secchi-depth, phenology metrics, surface currents and surface area. Information at catchment scale on land cover, land use, vegetation status and forest fires facilitate the establishment of linkages between catchment scale alterations and lake ecosystem processes. As such, remote sensing data complement and extend traditional lake sampling methods, facilitating understanding of the current state of lake ecosystems and supporting the application of appropriate management strategies.
References
C. Albrecht and T. Wilke (2008). Ancient Lake Ohrid: biodiversity and evolution. Hydrobiologia 615:103–140
S.C.J. Palmer, D. Odermatt, P.D.Hunter, C. Brockmann, M. Présing, H. Balzter, V.R. Tóth (2015). Satellite remote sensing of phytoplankton phenology in Lake Balaton using 10 years of MERIS observations. Remote Sensing of Environment 158: 441–452
R. Tiberti, S. Metta, M. Austoni, C. Callieri, G. Morabito, A. Marchetto, M. Rogora, G. Tartari, J. von Hardenberg, A. Provenzale (2013). Ecological dynamics of two remote Alpine lakes during ice-free season. J. Limnology, 72: 401-416