Exploitable results First estimates of changes in macroalgal zonation due to enhanced UVBR The results of the various studies were combined in order to achieve a first insight into the changes of the investigated coastal ecosystems induced by global climate changes due to atmospheric ozone depletion and greenhouse effect. In particular, we aimed to predict changes in depth distribution of individual species. Overall, there are several negative, but also some stimulating effects of UVBR on the various physiological processes. Additionally, there are various repair and protecting mechanisms operating. We have to conclude that physiological parameters are not sufficient to explain long-term effects of enhanced UVBR. Rather, measurements of the integrative parameters growth and recruitment allow better insights into the effects of UVBR on the ecology of marine macrophytes. In this respect, we can clearly predict that macrothalli of several eulittoral species will not be affected by enhanced UVBR. On the other hand, various sublittoral species, especially their unicellular propagation units, their spores, are extremely susceptible to UVR. This is particularly important in sublittoral brown algae from the Straight of Gibraltar, whose upper distribution limit is determined by UVBR. Therefore, the upper distribution limit of the respective species will definitely change under conditions of enhanced UVBR. UVR susceptibility of nutrient uptake and metabolism The effect of UVR on C, N and P uptake and metabolism has been studied in species from Southern Spain and in the North Sea. UVR has both stimulating and inhibiting effects on C, N and P uptake and metabolism in the various species. UVBR can either inhibit or stimulate bicarbonate uptake by carbonic anhydrase (CA). Species from the upper eulittoral exhibit higher CA activity than those growing, in deeper waters and the exclusion of UV-B causes a decrease of enzyme activity. 111 the Mediterranean red alga Rissoella verraculosa CA activity decreases after exposure to PAR whereas after exposure to the full solar spectrum CA activity increases in the afternoon in parallel to an increase of NR activity. Nitrate reductase is stimulated by UVAR in several cases. The obtained results are diverging and more studies have to be undertaken before the susceptibility of nutrient uptake in the various species can finally be assessed. UVR susceptibility and UVBR tolerance of marine macrophytes Representative species from deep and shallow sites were transplanted to water depths with UVR different to that at the site of growth. Additionally UVR exclusion experiment and laboratory experiments were carried out under controlled conditions in order to assess the possible effect of UVR on primary production. The physiological state of the experimental individuals has been assessed by measuring photosynthetic and respiratory activity. Photosynthesis of species from the eulittoral and of upper and mid sublittoral canopy species recovers quickly and completely from photoinhibition after exposure to UVR. In some Mediterranean species UVR seven supports recovery of photosynthesis after photoinhibition. However, undergrowth and deep water species are highly susceptible to excessive radiation. Some species do not recover at all. IN some species RubisCo is degraded, in other species the formation of a high molecular weight polypeptide was found. There is a considerable acclimation potential of photosynthesis to UVR in upper and mid sublittoral canopy species, not in deep water and undergrowth species. Respiration is mostly not affected. Overall, the response of the various species to UVR is far more different than previously documented in the literature ranging from photodamage and photoinhibition to a stimulation of photosynthesis. First detection of UVBR induced DNA damage and its repair in macroal-ac Macroalgae were exposed in the laboratory to temperature/UV stress stronger than measured in the habitat in order to assess DNA damage and repair as well as the effects of temperature/UV interactions on growth/survival. DNA damage was determined in macroalgae for the first time by an immunofluorescent technique. After UVBR exposure, DNA damage was induced in Rhodymenia pseudopalmata and Palmaria palmata but not in any species from the field. The unicellular zoospores from Lamininaria digitata showed strong formation of thymine dimers indicative of DNA damage correlated with spore mortality'. DNA repair by photoreactivation was temperature dependent in P. palmata., but not in R. pseudopalmata. In P. palmata the repair rate of thymine dimers increased with temperature, whereas the repair rate of 6-4 photo products was optimal at 12 degrees C. Global temperature increases would enhance repair of thymine dimers during the main growth period of this species in spring under conditions of enhanced UVBR. In spite of efficient DNA repair strong, reduction in growth rates were found even tinder low UVB doses. In order to explain the actual impact of enhanced UVBR on the ecology of marine macrophytes measurements of growth or recruitment are an absolute prerequisite. Prevention of UVR damage by formation of sunscreen pigments Macrophytes were analysed for UVR absorbing, Mycosporine-like amino acids (MAAS) by, HPLC. The beneficial effect of the sunscreen substances on avoiding, UVR stress was studied by measuring, variable chlorophyll fluorescence of photosystem 11. Red algal species from the eulittoral contain several MAAS, which are assumed to function as UV sunscreens. In contrast, deep-water red algae, as well as green and brown algae, lack MAAs or exhibit only trace concentrations. The contents of all MAAs correlates with the biogeoraphic region indicating that the lower the natural solar irradiance the less MAAs are synthesised and accummulated, i. e. the red algal samples from Spain exhibited tip to 2-fold hicher MAA contents compared to species from cold-temperate and polar water. Additional experiments indicate that formation of MAA's is induced species specifically, by PAR, UVAR or UVBR and that MAA's seem to especially prevent photodamage of photosynthesis. The results show - beside the negative impact of UV radiation oil metabolism and growth - the strong, capacity of MAAs to protect algae against UV stress. However, this protective capacity is limited in species front deeper waters and in microscopic developmental stages. Provision of reliable data of abiotic factors, especially UVR, in coastal ecosystems Radiation and temperature regimes were documented in three coastal systems (Southern Spain, North Sea and Spitsbergen). To record radiation automatic devices - crosslinked to ELDONET and to the Network for the Detection of Stratosphelichanes NDSC) - were installed. Nutrient concentrations in the water were additional determined in the Mediterranean/Atlantic region. Especially on Spitsbergen and Helgoland stratospheric ozone depletion is well correlated with an increase in UVBR. Highest UVBR was measured in Malaga and Helgoland. Correspondingly, DNA damaging, wavelengths decrease towards the north. In all locations UVBR increases during, summer. The 1 % water depth for UVBR are at Cabo de Gata (Spain) approx. at 15 m, indicating, a high potential UV damage on the marine macrophytes. In the North Sea the 1 % depth for UVBR is only 1 m because of the more turbid water conditions and in Spitsbergen 9 iii. There are, however, strong, seasonal chances of water transparency in all locations especially on Spitsbergen due to the input of turbid meltwater in summer. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
