The articles listed below are the current work of young diatomists.
Young diatomists' publications
- BENITO, X., TROBAJO, R. & IBÁÑEZ, C. 2015.
The contemporary distribution of benthic diatoms and their use as ecological indicators were examined in a coastal wetland, the Ebro Delta, as a representative of environmental conditions in Mediterranean coastal wetlands. A total of 424 diatom taxa were identified across 24 sites encompassing a wide range of wetland habitat types (coastal lagoons, salt and brackish marshes, shallow bays, microbial mats and nearshore marine waters) and conductivities. Canonical correspondence analysis showed that water conductivity and water depth were the main factors structuring the diatom assemblages. Cluster analysis identified five habitat types according to the similarity in diatom species composition: salt marshes, brackish marshes, brackish coastal lagoons and bays, coastal lagoons with fresher conditions, and nearshore open sea. For each wetland habitat, diatom indicator species were identified. Partial canonical correspondence analysis showed that water conductivity, a proxy for salinity, was the most statistically significant and independent variable for explaining the distribution of benthic diatoms in the study area. A transfer function, using a weighted average regression model, was developed for conductivity and displayed reasonable performance (r 2 = 0.64; RMSEP = 0.302 log10 mS/cm). Our study in the Ebro Delta provides a basis for using diatom assemblages to make quantitative conductivity inferences, and for using diatom indicator species to identify wetland habitats. These approaches are complementary and may be valuable for paleoenvironmental studies of (1) effects of large-scale, natural changes in the Delta (e.g. sea-level fluctuations), and (2) impacts of short-term anthropogenic changes, such as the introduction and development of rice agriculture.
- TAMMELIN, M. & KAUPPILA, T. 2018.
Both natural and anthropogenic changes in boreal lakes have been studied utilizing paleolimnological methods, but the spatial variation in the natural conditions of lakes and its connection to geological factors has drawn less attention. Our aims were to examine the spatial distribution of naturally eutrophic lakes on the previously glaciated terrain of central-eastern Finland and the relationship between pre-human disturbance water quality and geological factors related to the basins and their catchments. Furthermore, we studied the pre- to post-human disturbance changes in the diatom assemblages and water quality of 48 lakes (51 sampling sites) across the pre-disturbance phosphorus gradient by using the top-bottom sampling approach and multivariate statistics. According to our results, naturally eutrophic boreal lakes are more common than previously thought, occurring on fine-grained and organic Quaternary landforms, including fine-grained till. Our study emphasizes the importance of the previously overlooked matter of till grain-size variation as a driver behind the spatial variation in the natural trophic states of boreal lakes. The location of a lake in the hydrologic landscape and basin morphology appear to be important factors as well. Shallow, naturally eutrophic lakes with short water residence times and high catchment area to lake area and volume ratios have been particularly sensitive to anthropogenic forcing. Our results indicate that cultural eutrophication is not the only water protection challenge for the relatively remote and dilute boreal lakes, but salinization and alkalinization are also serious threats that should be taken into account. Therefore, it is crucial to consider the notable variation in the natural conditions of boreal lakes in addition to mitigating the effects of anthropogenic forcing, such as nutrient loading, catchment erosion, salt pollution, and climate change, in order to achieve efficient water protection.
- VELEZ, M.I., JARAMILLO, C., SALAZAR, F., BENITO, X., FRITZ, S., TAPIA, P., LUBINIECKI, D., KAR., N. & ESCOBAR, J. 2017.
Uplift of the Altiplano in the Central Andes of South America had profound effects on land, oceans and atmosphere. Very little, however, is known about the ecosystems that developed on the ecospaces first formed once the Altiplano reached its present high altitude. We present a micropaleontological (diatoms and ostracods) and stratigraphic analysis of Pliocene Member C of the El Descanso Formation that outcrops near the town of Yaurí, Perú. Lithofacies analysis indicates that fluvial conditions were eventually replaced by several lacustrine and marsh environments. Diatom and ostracod assemblages indicate that these bodies of water were alkaline, slightly saline and shallow. Lacustrine conditions were favoured by a change in the tectonic regime from compressional to tensional, which led to formation of small isolated basins, and by wet conditions. We hypothesize that a stronger and/or longer rainy season prevailed during that time in the Altiplano, possibly as a consequence of an intensified South American Summer Monsoon, driven by a warmer atmosphere, imposed by high concentrations of atmospheric CO2.
- ALMEDIA, P., WETZEL, C., MORALES, E.A, ECTOR, L., BICUDO, D.E. 2017.
Several species currently belonging to the genus Fragilariforma D.M. Williams et Round are known worldwide. This genus is mainly characterized by regular spacing of the uniseriate striae composed of round areolae bearing simple vela, and simple apical pore fields. A large number of species has been recognised for some regions of South America and tropical Africa, but few studies encompass type material and/or the morphological variation existing within populations of the different species. The aim of this study is to identify and describe the morphology of these species from tropical environments under light and scanning electron microscopy and using available type material. Nomenclatural issues are examined and clarified for five taxa: Fragilarianitzschioides var. brasiliensis Grunow, F. undata var. brasiliensis C. Zimmermann, F. strangulata (Zanon) D.M. Williams et Round, F. telum J.R. Carter et Denny and F. rolandschmidtii Metzeltin et Lange-Bertalot. The type material of F. nitzschioides var. brasiliensis, housed in the Grunow Collection at the Naturhistorisches Museum Wien (W) was examined and its epitypification is proposed. One new species from the Amazon region Fragilariformaamazonica sp. nov. is presented and described here, while Fragilaria telum is formally transferred to the genus Fragilariforma.
with molecular backround
- CARBALLEIRA, R., TROBAJO, R., LEIRA, M., BENITO, X., SATO, S. & MANN D.G. 2017.
A previously unknown member of the Bacillariaceae was discovered almost simultaneously in four different brackish coastal wetlands on the Atlantic and Mediterranean coasts of the Iberian Peninsula. It appears to tolerate a wide range of salinities but was never common in samples where it occurred. The frustules were consistently hantzschioid (i.e. with the raphe systems always on the same side of the frustule) and the valve outline was asymmetrical about the apical plane, two features that have until recently been considered characteristic of Hantzschia. Molecular phylogenies based on rbcL and LSU rDNA indicated, however, that the new species does not belong in Hantzschia but among the several disparate lineages that comprise the paraphyletic genus Nitzschia. This finding, coupled with the recent discovery of other diatoms with constant hantzschioid symmetry but with a morphology very similar to the type species of Nitzschia, is discussed in relation to the status and characterization of Hantzschia as an independent genus. It is concluded that, while a core of hantzschioid species may exist that can be classified together, corresponding to the traditional understanding of the genus Hantzschia, there is no single morphological feature common to all of them that can be used to diagnose the group and differentiate it from the various hantzschioid lineages that are separate from true Hantzschia and currently placed in e.g. Nitzschia or Cymbellonitzschia. Testing whether a hantzschioid species does or does not belong to Hantzschia will in many cases require molecular evidence. Although the new coastal species does not belong to the same lineage as the type species of Nitzschia, N. sigmoidea, it is described for the moment as N. varelae Carballeira, D.G. Mann & Trobajo, sp. nov., until there is a better understanding of generic limits in the Bacillariaceae following a wider molecular and morphological survey of that family.
- PINSEEL, E., VANORMELINGEN, P., HAMILTON, P.B., VYVERMAN, W., VAN DE VIJVER, B. & KOPALOVÁ K. 2017.
Recent morphology-based investigations of freshwater Arctic diatoms suggest that many species remain to be discovered, reflecting a unique polar flora. During a survey of the freshwater diatom flora of northern Billefjorden, including the Petuniabukta fjord region (Spitsbergen), several morphodemes belonging to the Achnanthidium minutissimum species complex were recorded. Molecular phylogenies based on rbcL, 28S and 18S sequences, including single cells from Canada and strains from Marion Island (sub-Antarctica) and GenBank revealed the presence of 12 distinct A. minutissimum complex lineages, of which three contained strains from Spitsbergen. One Arctic lineage is described as a new species. Achnanthidium digitatum sp. nov. is morphologically characterized by narrow, linear to only slightly lanceolate valves and usually two areolae per stria. The two remaining Arctic lineages are in need of a more complete morphological and molecular comparison with other representatives of the A. minutissimum complex to clarify their taxonomic identity. It is argued that implementation of molecular data in the taxonomy of Achnanthidium will be essential to solve the taxonomic problems associated with this group, eventually resulting in a better understanding of the biogeography and niche differentiation of different species belonging to the A. minutissimum complex. Ideally, this should be based on more variable genes than the currently widely used 18S, which does not have a species level resolution in the A. minutissimum complex.
of the Arctic region
- PINSEEL, E., KOPALOVÁ, K. & VAN DE VIJVER, B. 2014.
During a survey of freshwater diatoms from lakes in the region of Petuniabukta on Spitsbergen (Svalbard Archipelago) a new Gomphonema species, G. svalbardense sp. nov., has been recorded. The new taxon was previously cited in the literature as G. angustatum var. undulatum but this identification proved to be erroneous. Detailed morphology description of G. svalbardense based on light and scanning electron microscopy is presented in this paper and the morphological features of the taxon have been compared with similar species. Gomphonema svalbardense is characterized by its typical linear, almost naviculoid outline with undulating margins, with clearly inflated central part, asymmetric central area, lateral raphe with simple straight proximal endings and the weakly radiate striae. History, ecology and biogeography of the species, mainly based on literature data, have been included.
- PINSEEL, E., VAN DE VIJVER, B. & KOPALOVÁ, K. 2015.
During a survey of the freshwater littoral diatom flora from lakes and ponds in the region of Petuniabukta on Spitsbergen (Svalbard Archipelago, High Arctic region), a new Achnanthidium species, A. petuniabuktianum sp. nov., has been recorded. Achnanthidium petuniabuktianum is a new representative of the A. pyrenaicum group as evidenced by its curved distal raphe fissures. The present paper describes in detail the morphology of A. petuniabuktianum based on light and scanning electron microscopy. The new taxon is characterized in having linear valves with parallel margins and broadly rounded, never protracted apices and a characteristic—in light microscopy hardly discernible—striation pattern consisting of very short striae composed of one or two small, always slit-like areolae. Based on current results, Achnanthidium petuniabuktianum is a benthic taxon occurring in epilithic and epiphytic habitats in the littoral zones of freshwater lakes and ponds.
of the Antarctic region
- PINSEEL, E., HEJDUKOVÁ, E., VANORMELINGEN, P., KOPALOVÁ, K., VYVERMAN, W. & VAN DE VIJVER, B. 2017.
A recent detailed survey of the Maritime Antarctic diatom flora using a fine-grained taxonomy resulted in the description of many new species of Pinnularia in general and the section Distantes, including the P. borealis species complex, in particular. Moreover, DNA-based studies of P. borealis revealed that many more species need to be described within this complex. During a survey of the freshwater littoral diatom flora of James Ross Island (Ulu Peninsula) and Vega Island in Maritime Antarctica, a previously unknown chain-forming species in the P. borealis species complex of section Distantes was cultured from three different localities. Molecular phylogenies based on the nuclear-encoded D1–D3 large-subunit ribosomal DNA and plastid rbcL genes revealed that all cultures belong to a distinct highly supported lineage within the P. borealis species complex. Pinnularia catenaborealis sp. nov. is characterised by the presence of small spines located on a raised, thin silica ridge that almost entirely surrounds the valve face near the valve face/mantle junction, and the presence of small silica plates near the apices. In culture, P. catenaborealis formed chains of several tens of cells and in oxidised natural material, chains up to seven frustules were observed. Pinnularia catenaborealis is described from the littoral zone of freshwater Black Lake (Ulu Peninsula, James Ross Island) and has also been observed on nearby Vega Island. Although P. borealis is generally regarded as a (semi-)terrestrial diatom complex mainly occurring in (moist) soils and mosses, P. catenaborealis was found in freshwater habitats with an alkaline pH and low conductivity.
of the Mediterranean region
- VOSSEL, H.; REED, J. M.; HOUK, V.; CVETKOSKA, A. & VAN DE VIJVER, B. (2015).
Large, subfossil populations of an unknown centric, planktonic diatom were observed in a lake sediment core from Lake Kinneret (Israel), which is here described as Cyclotella paleo–ocellata sp. nov. The new taxon, which belongs to the Cyclotella ocellata species complex, is described and separated from other similar taxa (e.g., Cyclotella ocellata, Cyclotella kuetzingiana, Cyclotella polymorpha, Cyclotella paraocellata) based on a combination of the following morphological characters: valve diameter, number of orbiculi depressi (circular depressions), number of striae/10 μm, stria length, number and position of rimoportulae and the number of central and marginal fultoportulae. Cyclotella paleo–ocellata can be distinguished mainly by two prominent characteristics: (1) the number and the arrangement of the orbiculi depressi (4–8) which increase with the valve diameter and (2) the marginal fultoportulae, situated on each, every second or third costa. Since Cyclotella paleo–ocellata is at present only known from the subfossil bottom sediments of Lake Kinneret, its ecological preferences are inferred simply from the associated diatom flora.
Arctic diatom studies
- VINSOVÁ, P., PINSEEL, E., KOHLER, T.J., VAN DE VIJVER, B., ZARSKY, J., KAVAN, J. & KOPALOVÁ, K. (2015).
Cryoconite holes are small, extreme habitats, widespread in the ablation zones of glaciers worldwide. They can provide a suitable environment for microorganisms including bacteria, cyanobacteria, algae, fungi, and invertebrates. Diatoms have been previously recovered from cryoconite holes of Greenland and of Svalbard, and recent findings from Antarctica suggest that cryoconite holes may harbor a unique diatom flora distinct from other aquatic habitats nearby. In the present study, we characterize the diatom communities of Nordenskiöld glacier cryoconite holes in Billefjorden (Svalbard, Spitsbergen), and multivariate approaches were used to compare them with three freshwater localities in the immediate vicinity to investigate possible sources of the species pool. We found cryoconite holes to have similar or greater average genus-richness than adjacent lake/ponds habitats, even though lower numbers of valves were recovered. Overall, cryo-conite hole diatom communities differed significantly from those observed in lakes, suggesting that other sources actively contribute to these communities than nearby lakes alone. This further suggests that (i) diatoms present in cryoconite might not exclusively originate from aquatic habitats, but also from (semi-)terrestrial ones; and (ii) that a much wider area than the immediate surroundings should be considered as a possible source for cryoconite diatom flora.
- PINSEEL, E., VAN DE VIJVER, B., KAVAN, J., VERLEYEN, E. & KOPALOVÁ, K. (2017).
Despite the frequent application of diatoms in palaeoecological research in the High Arctic, our knowledge concerning the diversity, ecology, community associations, community dynamics and survival strategies of High Arctic freshwater littoral diatom floras is still rather limited. In the present study, the diversity, ecological characteristics and community structures of the freshwater littoral diatom flora from ponds and lakes of Petuniabukta (Spitsbergen, Svalbard Archipelago) were studied. In total, 87 samples from the littoral zone of 53 freshwater ponds and lakes were examined using light and scanning electron microscopy. A highly diverse diatom flora dominated by Achnanthidium and Nitzschia was observed. In total, 310 diatom taxa belonging to 59 genera were found, of which about one-third could not be identified beyond the genus level. Based on species composition, four main diatom communities were distinguished. Differences in environmental characteristics, such as habitat type, habitat diversity, habitat stability, streams, water pH and influence of the fjord, biota and human activities, appeared to be important factors in determining the observed diatom communities. The high number of unidentified taxa in this study indicates that a profound revision of the Arctic diatom flora is highly desired, not only to improve our fundamental knowledge concerning the diversity, ecology, community associations and biogeography of Arctic diatoms but also to aid applied (palaeo)environmental sciences.
- TAMMELIN, M., KAUPPILA, T. & VIITASALO, M. 2017.
The Iisalmi Route, a chain of lakes in central-eastern Finland, is more eutrophic than its surroundings. We used multivariate analyses to study the influence of selected environmental factors (water quality, basin characteristics, and subcatchment surficial geology) on the recent diatom assemblages across this steep local nutrient gradient. In addition to the spatial analysis of surface sediment diatom assemblages from 51 sampling sites (48 lakes), temporal changes in the total phosphorus (TP) concentrations of one Iisalmi Route lake (Lake Kirmanjärvi) were analyzed using weighted averaging partial least squares regression and 27 fossil diatom samples. Both TP and electrical conductivity (EC) showed statistically significant independent signals in the modern diatom data. The TP gradient was related to till grain size variation suggesting that geological factors affect the spatial TP variation directly or indirectly through differences in land use. Based on the temporal study, the direct effect of geology is most likely behind the steep nutrient gradient in the area because Lake Kirmanjärvi was found to be naturally eutrophic. EC, on the other hand, seems related to anthropogenic disturbance. Our study highlights the importance of taking the local geology into account when assessing past or present water quality or planning for lake management.
- KAUPPILA, T., AHOKAS, T., NIKOLAJEV-WIKSTRÖM, L., MÄKINEN, J., TAMMELIN, M.H. & MERILÄINEN, J.J. 2016.
The aquatic effects of forestry practices and peat extraction continue to cause serious concerns. The effect mechanisms of peat extraction on water quality and aquatic ecology of the receiving surface waters are well known, but the impacts are often difficult to differentiate from those of forest management. A pairwise temporal sediment study was conducted on two adjacent lakes in Central Finland to study whether the unique effects of peat extraction can be detected in an area of intensive forest drainage. Both lakes are affected by forestry, but the reference lake has no history of peat extraction in its watershed. The deepest parts of the lakes were cored through the lacustrine sediments, and the recent carbon and dry matter sedimentation rates were compared to their site-specific reference values. Recent changes in benthic macroinvertebrates (chironomids) and diatom algae were studied to assess the ecological effects of these practices in the lakes. No significant differences in recent increases in carbon accumulation were found between the peat extraction-impacted lake and the reference lake. The pairwise comparison allowed identification of a regional pattern of impacts that is closely related to the history of land use, particularly forestry, in the region. The approach also allowed identification of the transient signs of peat extraction in the chemical and chironomid records of the impacted lake. The recent changes in chironomids and diatoms suggest eutrophication and deterioration in benthic conditions likely caused by drainage ditch network maintenance activities in the catchments.