How do newly-described diatom species affect biomonitoring? – An example of Gomphonema paratergestinum vs. G. tergestinum

Over the past decade a great number of new diatom taxa was described, as well as re-definitions and delimitations of taxa from different species complexes have been performed. The reasons for the constant increase in the number of described diatom taxa are numerous: unexplored habitats, improved light microscope resolution and digital cameras with accompanying softwares, scanning electron microscopy, molecular studies. For most of the newly-described species only morphological characteristics are known. What about their ecological preferences? OMNIDIA is a widely used software for evaluation of ecological status of water bodies based on diatoms. The database from the first version of the software up to today has grown from 2035 to more than 23.000 diatom taxa. However, for the most newly-described taxa there are no indicator values. In our study we evaluated the ecological status at six sites in lakes Ohrid and Prespa, respectively, based on different biological quality elements (diatoms, macrozoobenthos and macrophytes) as well as water chemistry. In two out of six sites in lake Ohrid, and five out of six sites in lake Prespa, Gomphonema paratergestinum was a dominant or subdominant species (33.5-69.66 % in Ohrid Lake and 9.95-65.34 % in Prespa Lake). In the OMNIDIA software, there currently are no indicator values for G. paratergestinum. However, the very similar species G. tergestinum has well known indictor values. G. paratergestinum resembles G. tergestinum with respect to some morphological characteristics (e.g. valve outline), but can be differentiated by the stria density. Both species were present in lakes Ohrid and Prespa, however, with dominance of G. paratergestinum. Based on the diatoms recorded at a site, OMNIDIA calculates diatom index values. How could G. paratergestinum with abundances up to 69.66 % influence diatom indices? If we “experiment” and substitute G. paratergestinum with G. tergestinum, the obtained diatom index values indicated a completely different ecological quality class. Every newly-described species is important since it increases our knowledge about diversity, biogeography and distribution of diatoms. However, there still is a gap between taxonomy and biomonitoring. How can we overcome this problem? According to the Botanical Nomenclature Code for algae, fungi, and plants no note or suggestion regarding ecology or ecological preferences of a species is required for description. Maybe, a possible solution could be that in the description of the species ecological data, such as pH, conductivity, total phosphorus, concentrations of different anions etc. should be included. Scientists today join forces to review material and species collected by Kützing, Ehrenberg, Grunow, Van Heurck, Cleve etc... In the same way ecological data of newly-described species could be assembled and their indicator values calculated

Who is the better candidate? Macroinvertebrates and diatoms for ecological status assessment of Sava Lake (Serbia)

Sava Lake was created from the right arm of the Sava River, and the inhabitants of Belgrade use the lake intensively for swimming and bathing. We analysed macrozoobenthos and epilithic diatom communities at six sites from April to October 2017, to assess the ecological status of Sava Lake according to the National legislation of Serbia. Considering macrozoobenthos communities, the mean values of Zelinka and Marvan saprobity index indicated high ecological status. In contrast, results obtained from the mean values of BMWP (Biological Monitoring Working Party) scores suggested moderate to poor ecological status. The mean values of the IPS diatom index (Indice de Polluo-sensibilité) indicated high ecological status, while the TDIL index (Trophic Diatom Index for lakes) was slightly more sensitive and indicated good ecological status. Water chemical parameters indicated that Sava Lake was mainly oligotrophic during the study period (average total phosphorus concentrations were 10.7 μgL-1 and average total nitrogen concentrations 410 μgL-1). Before being able to adopt an integrative approach for ecological status assessment (combining two or more biological quality elements), more studies must be performed on how to choose the most sensitive and adequate indices. This is especially true for lakes experiencing intensive anthropogenic pressure during the summer season. Also, the boundary values in the National legislation of Serbia must be adapted for lakes, such as Sava Lake.11th Symposium for European Freshwater Sciences, June 30–July 5, 2019, Zagreb, Croatia, [http://www.sefs11.biol.pmf.hr/

Relating environmental pressures to littoral biological water quality indicators in Western Balkan lakes: Can we fill the largest gaps?

Along six transects in each of six lakes across the Western Balkans, we collected data for three groups of littoral biological water quality indicators: epilithic diatoms, macrophytes, and benthic invertebrates. We assessed the relationships between them and three environmental pressures: nutrient load (eutrophication), hydro-morphological alteration of the shoreline, and water level variation, separating the effect of individual lakes and continuous explanatory variables. Lake water total phosphorus concentration (TP) showed substantial variation but was not related to any of the tested biological indicators, nor to any of the tested pressures. We suggest that this may be due to feedback processes such as P removal in the lake littoral zone. Instead, we found that a gradient in surrounding land-use towards increasing urbanization, and a land-use-based estimate of P run-off, served as a better descriptor of eutrophication. Overall, eutrophication and water level fluctuation were most important for explaining variation in the assessed indicators, whereas shoreline hydro-morphological alteration was less important. Diatom indicators were most responsive to all three pressures, whereas macrophyte biomass and species number responded only to water level fluctuation. The Trophic Diatom Index for Lakes (TDIL) was negatively related to urbanization and wave exposure. This indicates that it is a suitable indicator for pressures related to urbanization, although a confounding effect of wave exposure is possible. Invertebrate abundance responded strongly to eutrophication, but the indicator based on taxonomic composition (Average Score Per Taxon) did not. Our results suggest that our metrics can be applied in Western Balkan lakes, despite the high number of endemic species present in some of these lakes. We argue that local water management should focus on abating the causes of eutrophication and water level fluctuation, whilst preserving sufficient lengths of undeveloped shoreline to ensure good water quality in the long run

Eutrophication impacts littoral biota in Lake Ohrid while water phosphorus concentrations are low

Eutrophication has traditionally been measured as increased phosphorus concentrations. In some lakes, however, such as transboundary Lake Ohrid situated between Macedonia and Albania, pelagic phosphorus concentrations are low, in spite of known sources of nutrient input. We assumed that littoral biota may be more responsive to phosphorus load than water chemistry, and studied nearshore water chemistry, macrophytes, diatoms and macroinvertebrates at 30 sites around the lake, analyzing functional groups as well as standard eutrophication metrics. We hypothesized that the incorporation of nutrients into benthic biomass will conceal correlations between water phosphorus concentrations and biological eutrophication metrics, but that analysis of functional groups in addition to eutrophication metrics may help draw a plausible picture of how phosphorus is transferred through the food web. Water total phosphorus concentrations in the Lake Ohrid littoral were generally low, while all three analyzed organism groups indicated at least some degree of eutrophication. This shows that littoral biota are more sensitive indicators of nutrient input than hydrochemistry. The abundance of the benthic alga Cladophora sp. correlated positively with water total phosphorus concentrations, indicating that P-loading at local scales may be an important driver of Cladophora biomass. In contrast, none of the biotic metrics (macrophyte index, diatom index, and macroinvertebrate ICM) correlated with ambient water P-concentrations. We argue that this is not a sign of poorly working biological metrics, but a consequence of ecosystem processes in the lake littoral. Analysis of macrophyte and benthic algae abundance, and macroinvertebrate feeding types together with the biotic metrics suggests a meso- to slightly eutrophic littoral ecosystem where nutrient supply is incorporated into macrophyte and benthic algae biomass, and transferred through the food web from benthic algae to grazers, and from macrophytes to shredders and gatherers. Macroinvertebrate filter feeders correlate negatively with water total phosphorus concentrations, suggesting they remove phosphorus from the water. Our results indicate that the combined use of classical biological eutrophication metrics and functional groups may be a way to not only distinguish between oligotrophic and eutrophic ecosystems, but in addition give information as to whether or not nutrient input and nutrient removal in an ecosystem are balanced. This may eventually also give information about ecosystem functioning and ecosystem stability, and thus provide a basis for the development of “second generation” metrics for ecosystem assessment.acceptedVersio

Testing the applicability of diatom indices for ecological assessment of Balkan lakes

During 2016-2017 six Balkan lakes were investigated: Sava Lake in Serbia, Ohrid Lake and Prespa Lake in North Macedonia and Albania, Great Lake in Albania, Biogradsko Lake and Crno Lake in Montenegro. Epilithic diatom samples were collected from 6 localities around each lake with the aim to test the applicability of diatom indices for ecological assessment of Balkan lakes. Also, water samples for chemical analysis were taken. Based on the concentrations of total phosphorus and BOD (biochemical oxygen demand) two lakes (Ohrid and Crno) were oligotrophic and oligosaprobic, while the other four lakes were mesotrophic and β-mesosaprobic, respectively. The highest diversity of dominant taxa was recorded in Ohrid and Prespa, and one of the dominant taxa was the endemic species Gomphonema paratergestinum. Diatom communities in lakes Sava and Crno were dominated by Achnanthidim minutissimum and Encyonopsis microcephala. According to Serbian legislation, the IPS index is used for the assessment of the ecological status of lakes, while in North Macedonia, Albania and Montenegro National Monitoring Systems do not yet include officially accepted diatom indices. In our results, the diatom indices IPS and IBD had the highest inclusion of diatom taxa, in some lakes almost 100%. The lowest inclusion of diatom taxa had the TDIL index. Values of IPS and IBD indices indicated very good water quality for Great Lake, Crno and Biogradsko, and good for Prespa. The water quality of Ohrid and Sava was between very good and good. Values of trophic indices (Rott TI and TDIL) indicated a very low concentration of nutrients in the Sava, Great Lake and Biogradsko, low in Ohrid and Prespa and low to the very low concentration of nutrients in Crno. The development and establishment of monitoring systems in lakes according to the requirements of the Water Framework Directive (WFD) is essential for all European countries and more comprehensive ecological investigations of Balkan lakes are necessary to be able to fulfill these demands.7th European Phycological Congress, Zagreb, Croatia, 25-30.08.201

Littoral eutrophication indicators are more closely related to nearshore land use than to water nutrient concentrations: A critical evaluation of stressor-response relationships

Biological assessment metrics and water chemistry measurements are used to quantify the link between stressors and their effects on lake ecosystems, for the Water Framework Directive. However, correlations between metrics and water chemistry are often poor. This is seen as major weaknesses of Water Framework Directive-related monitoring and assessment. We analyzed macrophytes, benthic algae, benthic macroinvertebrates, water chemistry and sediment total phosphorus content in the littoral of six lakes in the Western Balkans and used CORINE land use data to estimate nutrient enrichment via runoff from the adjacent land. Lakes with a higher estimated phosphorus runoff from the adjacent land did not have higher littoral water nutrient concentrations, but littoral diatom assemblages indicated more eutrophic conditions. These lakes also had higher abundances of littoral benthic primary producers, which in turn were associated with low concentrations of dissolved nutrients, but only in autumn, not in spring. This is consistent with primary producers taking up nutrients during the summer growth season. In lakes with high abundances of benthic primary producers, it is likely that the littoral vegetation plays a large role in the transfer of nutrients from the water to the benthos. This process impairs correlations between biological metrics and water nutrient concentrations. Our results suggest that CORINE land cover may be more useful to characterize littoral nutrient enrichment than lake water chemistry. Increased benthic primary producer biomasses and “eutrophic” diatom indices may indicate littoral nutrient enrichment even if water nutrient concentrations are low

Littoral eutrophication indicators are more closely related to nearshore land use than to water nutrient concentrations: A critical evaluation of stressor-response relationships

Biological assessment metrics and water chemistry measurements are used to quantify the link between stressors and their effects on lake ecosystems, for the Water Framework Directive. However, correlations between metrics and water chemistry are often poor. This is seen as major weaknesses of Water Framework Directive-related monitoring and assessment. We analyzed macrophytes, benthic algae, benthic macroinvertebrates, water chemistry and sediment total phosphorus content in the littoral of six lakes in the Western Balkans and used CORINE land use data to estimate nutrient enrichment via runoff from the adjacent land. Lakes with a higher estimated phosphorus runoff from the adjacent land did not have higher littoral water nutrient concentrations, but littoral diatom assemblages indicated more eutrophic conditions. These lakes also had higher abundances of littoral benthic primary producers, which in turn were associated with low concentrations of dissolved nutrients, but only in autumn, not in spring. This is consistent with primary producers taking up nutrients during the summer growth season. In lakes with high abundances of benthic primary producers, it is likely that the littoral vegetation plays a large role in the transfer of nutrients from the water to the benthos. This process impairs correlations between biological metrics and water nutrient concentrations. Our results suggest that CORINE land cover may be more useful to characterize littoral nutrient enrichment than lake water chemistry. Increased benthic primary producer biomasses and “eutrophic” diatom indices may indicate littoral nutrient enrichment even if water nutrient concentrations are low

Littoral eutrophication indicators are more closely related to nearshore land use than to water nutrient concentrations: A critical evaluation of stressor-response relationships

Biological assessmentmetrics and water chemistry measurements are used to quantify the link between stressors and their effects on lake ecosystems, for the Water Framework Directive. However, correlations between metrics andwater chemistry are often poor. This is seen as majorweaknesses ofWater Framework Directive-relatedmonitoring and assessment.We analyzed macrophytes, benthic algae, benthic macroinvertebrates, water chemistry and sediment total phosphorus content in the littoral of six lakes in the Western Balkans and used CORINE land use data to estimate nutrient enrichment via runoff from the adjacent land. Lakes with a higher estimated phosphorus runoff fromthe adjacent land did not have higher littoralwater nutrient concentrations, but littoral diatom assemblages indicated more eutrophic conditions. These lakes also had higher abundances of littoral benthic primaryproducers, which in turnwere associatedwithlowconcentrations of dissolved nutrients, but only in autumn, not in spring. This is consistent with primary producers taking up nutrients during the summer growth season. In lakeswith high abundances of benthic primary producers, it is likely that the littoral vegetation plays a large role in the transfer of nutrients from the water to the benthos. This process impairs correlations between biological metrics and water nutrient concentrations. Our results suggest that CORINE land cover may be more useful to characterize littoral nutrient enrichment than lake water chemistry. Increased benthic primary producer biomasses and “eutrophic” diatom indicesmay indicate littoral nutrient enrichment even ifwater nutrient concentrations are lo