Diatom Valves Research Articles

Lake Teletskoye (Altai, Russia): reconstruction of the environment and prediction for its changes according to the composition and quantity of diatoms in the bottom sediments

We studied the upper 0-1000 mm of the bottom sediment core from the underwater Sofia Lepneva Ridge of Lake Teletskoye. The core sediments accumulated with a rate of 0.3 mm/year (with regard to their humidity, with a rate of 0.45 mm/year) and have an age of about 2000 years. A total of 194 species (212 varieties and forms) of diatoms have been revealed. Analysis of diatom composition in tanatocoenoses showed prevalence of species inhabiting the bottom and periphyton, widely distributed geographically, indifferent to salinity, and preferring a weakly alkaline environment, as well as beta-mesosaprobionts. The number of diatom valves ranged from 0.86 to 64.4 mln valves/g, with an average of 22.90 ± 0.78 mln valves/g. Over the last millennium, the peaks of the abundance of diatoms, especially representatives of the cold-water assemblage, including the main dominant Aulacoseira subarctica (O. Mull.) Haw., are referred to the periods with low water temperature. The pH value for the period from 172 BC to 2006 AD has been reconstructed from the proportion of the numbers of valves of pH-indicating diatom species, which varied from 7.51 to 7.69, with an average of 7.580 ± 0.003. The pH value predicted up to 2259 AD was estimated by spectral (Fourier) analysis at 7.53-7.63, with a similar average of 7.580 ± 0.001. Analysis of reconstructed and predicted pH values showed their insignificant changes and correspondence to a weakly alkaline environment (7.0-8.5). These pH values suggest stability of the lake environment both in the past periods and in the nearest future.

Medlinella amphoroidea gen. et sp. nov. (Bacillariophyta) from the neck skin of Loggerhead sea turtles (Caretta caretta)

Medlinella amphoroidea gen. et sp. nov. is described from the dorsal neck skin of loggerhead sea turtles (Caretta caretta). The presence of girdle septa, multiple copulae, and the marine epizoic habitat of Medlinella amphoroidea are characteristic features shared with many species in the similar Tripterion, Chelonicola, and Poulinea genera. The semi-lanceolate valve shape, the asymmetric valve face with distinct dorsal and ventral striae, and the volate pore occlusions distinguish Medlinella from these genera. Medlinella amphoroidea accounted for up to 50% of all diatom valves on the skin of examined loggerhead turtles. Examination of the type slides of Tripterion kalamensis and T. philoderma for comparative purposes revealed morphological features that were either insufficiently or incorrectly described in the original publications. Our observations confirm that T. philoderma lacks septa and therefore does not conform to the genus description of Tripterion. The description of cingulum structure in Tripterion kalamensis is amended to identify multiple porose copulae that are open at one end. While the description of Medlinella creates another monotypic genus within a group of similar marine epizoic genera, we feel the novel character state (volate occlusions) present in this taxon is significant. Clearly, however, further phylogenetic analysis of morphological, or the development of molecular characters in the group of similar genera is required.

The water quality parameters controlling diatoms assemblage in Rawapening Lake, Indonesia

Soeprobowati TR, Tandjung SD, Sutikno, Hadisusanto S, Gell P, Hadiyanto. 2016. The water quality parameters controlling diatoms assemblage in Rawapening Lake, Indonesia. Biodiversitas 17: 657-664. Diatoms are microalgae that have an important role in aquatic ecosystem. The silicious diatoms fossil had been used for paleolimnological analysis. However, data set diatoms of Indonesia does not develop yet. The aims of this research were to assess water quality parameters controlling diatoms assemblage of RawapeningLake, to assess transfer function, to develop diatoms data set of Rawapening, and to compare Rawapening diatoms data set with European diatoms data set for the reconstruction of total phosphorous and pH. Water samples were taken from 3 sites of Rawapening Lake for water quality analysis. Sediment samples had been taken from 3 sites in Rawapening Lake using hand auger, and were sliced every 0.5 cm for diatoms analysis. Diatoms slides were prepared from about 5 g of dry sediment using 10% of chloride acid followed by 10% of peroxide to remove organic matters and carbonates, respectively.300 diatom valves were calculated on the entire samples, calculation the number of valve’s diatom aims to identify the lowest level of taxonomy. Phosphate, temperature, and calcium were theenvironmental parameters that influence the diatoms assemblage of Rawapening Lake. Phosphate was contributed 50% on diatoms assemblage. Internal based transfer function of diatoms provides more suitable diatoms data set rather than European diatom data set. The Rawapening diatoms data set of total phosphorous is the initial Indonesian diatoms data set for past trophic status, therefore, research has to be continued spatially for other Indonesian lakes and temporary on specific Indonesian lake to develop Indonesia diatoms data set.

The fate of diatom valves in the Subantarctic and Polar Frontal Zones of the Southern Ocean: Sediment trap versus surface sediment assemblages

An array of deep ocean sediment traps was initiated in 1997 within the Australian sector of the Southern Ocean, and serviced annually for over a decade (the Subantarctic site is ongoing as part of the Southern Ocean Time Series). Here, we expand on previous findings obtained from the shallow traps (~1000m depth) in the Polar Frontal Zone (PFZ) and Subantarctic Zone (SAZ) by examining the chemical composition and diatom assemblages collected by sediment traps deployed at bathypelagic depths in the PFZ (1500m depth; years 1997–1998, 1999–2000 and 2003–2004) and SAZ (2000 and 3800m; year 1999–2000). Additionally, the diatom assemblages of the surface sediments below the traps were analyzed to document how the seasonal signal is recorded in the sedimentary record. Analysis of the changes of the BSi:POC ratios with depth at both sites confirms previous work suggesting that the decoupling between Si and C cycles in the Southern Ocean is not different from other biogeochemical provinces of the world's ocean. Comparison of the seasonal flux pattern registered by the traps indicates that the diatom assemblages in the sediments of the Antarctic Zone and PFZ mainly represent the summer period. In contrast, the assemblages found in the sediments of the SAZ are a reflection of the spring and summer months, a period characterized by a larger variability in chemical and physical parameters. The strong correlation between the POC fluxes and the relative abundance of a group of diatom species (mainly Pseudo-nitzschia and small Fragilariopsis) in the PFZ traps suggest that there is an intimate relationship between the development of these species and the POC pulses to the deepest layers of the water column in this region. Interestingly, analysis of the diatom assemblages in the surface sediments reveals that the strong dissolution in the sediment-water interface removed the signal of these “carbon sinkers” from the sedimentary record leaving the sediment assemblage enriched in heavily silicified species.

Assemblage diversity, cell density and within-slide variability: Implications for quality assurance/quality control and uncertainty assessment in diatom-based monitoring

This study was undertaken to evaluate the variability associated with the microscope analysis step in the application of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l’Est du Canada), with the general objective of developing a suitable quality assurance/quality control (QA/QC) program for this biological index. For this purpose, we estimated within-slide variability (replicability) and inter-analysts variability (reproducibility), as a function of diatom assemblage diversity and slide cell density. Overall, our results show that variability associated with diatom assemblage characterization is low, which ensures that IDEC scores reflect environmental changes rather than variability at the microscope analysis step. The main recommendations ensuing from this study are (for the IDEC in particular but also for diatom-based monitoring in general):(1)An error term of ±2 IDEC units corresponding to the within-slide variability (replicability) should accompany all reported IDEC scores.(2)A deviation of ±3 points from the audit's IDEC scores should be considered as an acceptable difference. Considering the above-mentioned estimated error term of ±2 associated with all IDEC scores, an overall deviation of 7 would still be satisfactory.(3)Samples showing low diversity (Hill's N2 ≤5) should automatically be submitted for QA/QC.(4)A Bray–Curtis (analyst vs audit) similarity of ≥60% should also be included as a QA/QC criterion, and should increase to ≥70% for poorly diversified assemblages (Hill's N2 ≤5).(5)A diatom valve density of ≤15 per field of view should be targeted in order to reduce variability at the enumeration step.The results of this study illustrate how a relatively simple and straightforward approach to QA/QC can greatly strengthen the reliability of ecological inferences from an index based on a group of organisms with a high taxonomical diversity. It also highlights the importance of regular communication between analysts in order to maintain a high degree of concordance within taxonomical identification.

Environmental Characteristics of the Diatom in the Trench Sediments Around Bangudae Petroglyphs, Ulsan

Diatoms were studied from the trench sediments around Bangudae petroglyphs in order to better understand the depositional environment before and after the construction of Sayeon dam in Ulsan. There were no diatoms produced from the sediments before the dam construction while the diatoms were produced from the sediments (depth of trench 228 cm) after the construction of the dam. Seventy-five species of diatoms of 27 genera were identified in the trench sediments. The number of diatom valves per gram of dry sediment ranged from . Four diatom assemblage zones were identified according to the frequency of critical taxa as follows: assemblage zone I, from 228 to 150 cm; assemblage zone II, from 150 to 122 cm; assemblage zone III, from 122 to 62 cm; and assemblage zone IV, from 62 to 0 cm. In addition, based on the environmental indicator species, an analysis was carried out to measure eutrophication, acidity and value. Results of the eutrophication and values were as follows. Based on the lower 74 cm horizons, the degree of eutrophication middle-high to values were lower, upper horizons appeared to eutrophication in the low, and values were high. Acidification from low horizons of 122 cm showed a neutral-alkaline degree whereas it exhibited acid in the upper part. In particular, regarding nutrients (TP and TN), the index taxa showed a higher TP value at 175 cm while higher TN value at 62 cm.

THE MINIMUM NUMBER OF VALVES FOR DIATOMS IDENTIFICATION IN RAWAPENING LAKE, CENTRAL JAVA

Technical challenges in using diatoms for paleolimnological work are the identification and enumeration of diatom valves. Variations exist in the minimum number of valves to identify, ranging from 100 to 700 valves of the dominant species. This task can be very time consuming, particularly when the diatom valves are not abundant. This research was conducted to determine the minimum number of valves to be identified in the diatom assemblages from Rawapening Lake, Central Java, Indonesia. Based on the 314 samples obtained from Rawapening Lake, the diatom efficiency rose above 0.85 upon the minimum count of 300 valves. The number of diatom species identified remained stable after the minimum of 300 valves. Therefore, the minimum number of diatom’s valves identified to represent the assemblage for paleolimnological analysis was 300.

Tursiocola denysii sp. nov. (Bacillariophyta) from the neck skin of Loggerhead sea turtles (Caretta caretta)

Tursiocola denysii sp. nov. is described from the dorsal neck skin of loggerhead sea turtles (Caretta caretta), bringing the total number of known species in the genus Tursiocola to eight. A gradient of striae density on the valve face, the low length:width ratio of the valves, radiate striae at mid-valve, and a second partial row of pores on the valvocopulae are characteristics that expand the range of morphological diversity within the genus. The different morphology of the pars interior and the pars exterior of the valvocopula is described for the first time in the genus. T. denysii accounted for up to ca. 40% of all diatom valves on the skin of loggerhead turtles. This is the first report of a new epizoic diatom species from the skin of loggerhead sea turtles.

Community- and population-level changes in diatom size structure in a subarctic lake over the last two centuries.

Climate change over the last two centuries has been associated with significant shifts in diatom community structure in lakes from the high arctic to temperate latitudes. To test the hypotheses that recent climate warming selects for species of smaller size within communities and a decrease in the average size of species within populations, we quantified the size of individual diatom valves from 10 depths in a sediment core covering the last ∼200 years from a pristine subarctic lake. Over the last ∼200 years, changes in the relative abundance of species of different average size and changes in the average valve size of populations of species contribute equally to the changes in community size structure, but are often opposite in sign, compensating for one another and moderating temporal changes in community size structure. In the surface sediments that correspond to the recent decades when air temperatures have warmed, the mean size of valves in the diatom community has significantly decreased due to an increase in the proportion of smaller-sized planktonic diatom species.

Diatom characteristics of the Far East siliceous organogenic deposits

Three Far East diatomites, Puzanov (Kunashir Island, Kuril Islands), Sergeevskii, and Terekhovka (Southern Primorye) are characterized in detail. Rock-forming taxa are identified (Puzanov—Aulacoseira subarctica (O. Mull.) Hawort and Stephanodiscus niagarae var. pusanovae Genkal et Cherepanova; Sergeevskii—Staurosira construens var. venter (Ehr.) Gran., Aulacoseira italica (Ehr.) Sim., and representatives of the genus Cymbella with large valves (up to 175 Jim in length); Terekhovka—Aulacoseira praegranulata var. praeislandica f. praeislandica (Sim.) Moiss.). Morphometric analysis of valves of the dominant taxa showed a low variability of valve parameters for the Puzanov diatomite and a high one for the Sergeevskii and Terekhovka diatomites. The lake environments of the diatoms forming the diatomites were reconstructed based on the elemental composition of diatom valves and the ecological structure of diatom paleocommunities. The high oxygen and low silicon concentrations in valves of the Puzanov diatomite, most likely, indicate that the diatoms were part of plankton communities formed in a large deep freshwater lake. Significant concentrations of silicon in valves of the Terekhovka diatomite, in contrast, suggest that the diatoms occurred in benthic ecotopes in a shallow lake. The age of the deposits was refined by detailed studies of Aulacoseira valves, using light and scanning electron microscopes. For example, the presence of Aulacoseira taxa of the “prae” group in the Terekhovka diatomite confirms its Pliocene age, and the presence of valves of the present species A. italica in the Sergeevskii diatomite points to its Late Pliocene age. The identified features of the diatomites permit their use in practice.

Diatoms at >5000 Meters in the Quelccaya Summit Dome Glacier, Peru

Diatoms were found in late Holocene age ice-core samples recovered from the Quelccaya Summit Dome in the tropical Andes of Peru and were imaged by environmental scanning electron microscopy and identified. Freshwater diatoms in the genera Hantzschia, Pinnularia, and Aulacoseira were the most common taxa in the samples and indicate a freshwater source for the material, which also is suggested by the presence of the freshwater alga Volvox. The overall species composition of the diatoms suggests that the majority of taxa originated from a high-elevation lake or wetland in the cordillera surrounding the ice cap. The abundant diatom valves, up to 70 µm in size, likely were transported to the ice via wind.

남극 엽층리 퇴적물로부터 규조 종을 이용한 고기후 변화 연구

This study investigated the paleoclimatic change using diatoms that were extracted from the high-resolution laminated layers of diatom ooze sediment cores GC08-EB01 in the eastern basin of the Bransfield Strait, Antarctica. The range of diatom valves per gram of dry sediment was from in quantitative diatom assemblage analysis. Laminations are classified using visually dominant diatom species and terrigenous content. Biogenic diatom ooze laminae characterised by bloom of Corethron crilophilum, Eucampia antarctica, Fragilariopsis curta, F. kerguelensis, Odontella weissflogii, Proboscia inermis, R. styliformis, Thalassiosira antarctica, and Chaetoceros resting spores. Terrigenous laminae characterised by mixed diatom assemblage. The ratio of (Fragilariopsis curta+F. cylindrus)/Thalassiosira antarctica increase in horizons, suggesting increased sea-ice cover in the study area during the late Holocene (cold events). As a result, five cold events are identified on the basis of frequency of the critical taxa throughout the section.

A record of Pleistocene diatom preservation from the Amundsen Sea, West Antarctica with possible implications on silica leakage

article i nfo Accumulation of fossil diatoms in marine sediments is variably affected by the production and dissolution of diatom frustules across space and time. No quantitative proxy exists for estimating the amount of silica lost to dissolution in Southern Ocean sediment cores. To address this gap, cultured valves of Fragilariopsis kerguelensis, the dominant planktonic diatom in the Pleistocene to recent Southern Ocean, were dissolved progressively under controlled laboratory conditions. Expansion, and eventual conjoining, of the areolae of F. kerguelensis advances through several phases, which are presented herein as a measure of diatom dissolution. In order to evaluate the validity of laboratory methods, this proxy is applied to sediments from piston core PS58/254 from the Amundsen Sea. Dissolution-induced degradation morphologies from laboratory experiments are seen to be identical to those preserved naturally in sediments, thus suggesting the laboratory conditions accurately reflect the natural process of dissolution. These resultsrepresentthe firstapplication of afullyquantitativeproxyfordiatomdissolution toSouthernOcean sediments, revealing that meaningful paleoceanographic data can be generated via taphonomic analysis of diatom valves. Intensity of diatom dissolution in core PS58/254 does not correspond to the relative abundance of any diatom species, clay mineralogy, or linear sedimentation rates. However, a correlation does exist between glacial cyclicity and diatom dissolution, indicating that variation in average wall thickness and susceptibility to dissolution reflects primary conditions during formation of the silica wall, transit through the water column, and eventual deposition. Higher overall silica dissolution is observed during each glacial period and enhanced silica preservation during interglacials. This result is consistent with the predictions of the silicic acid leakage hypothesis (SALH), whereby reduced rates of Si usage in the Southern Ocean lead to shifts in marine primary productivity in the tropics from coccolithophoriddominance duringinterglacialstodiatomdominanceduringglacials.Thiswouldfuela decrease in atmospheric pCO2duringglacials. Silica acidleakage isdrivenbya decreaseinthe Si:Nratioofdiatoms,caused by increased iron input to glacial-aged Southern Ocean waters. This resulted in more lightly silicified diatom valves in the Southern Ocean, which dissolved more quickly in the upper water column, thereby maintaining the high silica content of glacial-aged SO waters, and allowing for export of Si to upwelling zones in the lower latitudes.

Interference patterns and extinction ratio of the diatom Coscinodiscus granii.

We report experimental and theoretical verification of the nature and position of multiple interference points of visible light transmitted through the valve of the centric diatom species Coscinodiscus granii. Furthermore, by coupling the transmitted light into an optical fiber and moving the diatom valve between constructive and destructive interference points, an extinction ratio of 20 dB is shown.

Three New Species of Tursiocola (Bacillariophyta) from the Skin of the West Indian Manatee (Trichechus manatus)

Three new species of Tursiocola are described from the skin of the West Indian manatee bringing the total number of known species in the genus to seven. The range of morphological diversity within the genus is greatly expanded. The number of poroid rows on the copulae is no longer a valid characteristic for the separation of Tursiocola from the ceticolous genus Epiphalaina. The presence of a butterfly-like structure in the central area of the former is at present the best criterion for separating the 2 genera. The 3 new Tursiocola species accounted for nearly 90% of all diatom valves on the manatee skin. No other diatom taxa previously described as new from the skin of cetaceans were present on the manatee.

Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean

Abstract. We studied time-series fluxes of diatom particles from 4 October 2010 to 18 September 2012 using bottom-tethered moorings with two sediment traps deployed at 180 and 1300 m depths at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. This paper discusses on the relationship of time-series diatom fluxes to satellite-based sea-ice motion and simulated hydrographic variations. We observed clear maxima of the diatom valve flux in November–December of both 2010 and 2011, and in August 2011. Diatoms in samples were categorized into 98 taxa. The diatom flux maxima were characterized by many resting spores in November–December and by the sea-ice-associated diatom Fossula arctica in August 2011. These assemblages along with abundant clay minerals in the samples suggest a significant influence of shelf-origin materials transported by mesoscale eddies, which developed along the Chukchi Sea shelf break. In contrast, the fluxes of total mass and diatoms were reduced in summer 2012. We hypothesize that this suppression reflects the influx of oligotrophic water originating from the central Canada Basin. A physical oceanographic model demonstrated that oligotrophic surface water from the Beaufort Gyre was supplied to Station NAP from December 2011 to the early half of 2012.

VÝSLEDKY MIKROPALEONTOLOGICKÉ REVIZE ŠARATICKÝCH CF VRTŮ

Restudy of archive foraminifer slides from Šaratice boreholes and new field observations allowed revision of the geology in the margin of the Carpathian Flysch Belt southeast of Brno. In the marginal zone originally assigned to the Němčice Formation newly three different formations were distinguished: Pouzdřany Formation of the Pouzdřany Nappe, and Němčice and Menilite formations of the Ždánice Nappe. Planktonic foraminifers were applied in biostratigraphical assignment of samples. Benthic communities were statistically evaluated using cluster analysis. Each formation has distinct microfossil taphocoenosis and characteristic benthic foraminifer community. Microfossil communities with abundant sponge spicules and diatom valves preserved in opal and also presence of small mollusc fauna and fish otoliths indicate that marginal zone of Ždánice Nappe was deposited little bit shallower than the more internal zones. Also lithology reflects different palaeoenvironment. Clays of the Menilite Formation are macroscopically undistinguishable from Hustopeče-type clays of the overlying Ždánice-Hustopeče Formation. The Ždánice-type sandstones are practically missing. Grey pelocarbonate concretions are frequent in both Menilite and Ždánice-Hustopeče formations. The marker lithologies of the Menilite Formation – the menilite chert and Dynów-type marlstone (or their analogues) – were not observed yet. Results of the revision show that the marginal zone of the Carpathian Flysch Belt in Šaratice area comprises tectonic slices of mentioned formations, the number and order of whose change from borehole to borehole.

Coastal evidence for Holocene subduction-zone earthquakes and tsunamis in central Chile

The ∼500-year historical record of seismicity along the central Chile coast (30–34°S) is characterized by a series of ∼M 8.0–8.5 earthquakes followed by low tsunamis (<4 m) occurring on the megathrust about every 80 years. One exception is the AD 1730 great earthquake (M 9.0–9.5) and high tsunami (>10 m), but the frequency of such large events is unknown. We extend the seismic history of central Chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of Valparaíso (33°S). At this site, higher relative sea level during the mid Holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence. Within this 2600-yr-long sequence, we traced six laterally continuous sand beds probably deposited by high tsunamis. Plant remains that underlie the sand beds were radiocarbon dated to 6200, 5600, 5000, 4400, 3800, and 3700 cal yr BP. Sediment properties and diatom assemblages of the sand beds—for example, anomalous marine planktonic diatoms and upward fining of silt-sized diatom valves—point to a marine sediment source and high-energy deposition. Grain-size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment. Upward fining sequences characteristic of suspension deposition are present in five of the six sand beds. Despite the lack of significant lithologic changes between the sedimentary units under- and overlying tsunami deposits, we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds. During our mid-Holocene window of evidence preservation, the mean recurrence interval of earthquakes and tsunamis is ∼500 years. Our findings imply that the frequency of historical earthquakes in central Chile is not representative of the greatest earthquakes and tsunamis that the central Chilean subduction zone has produced.

Jelly-like Microbial Mats over Subsurface Fields of Gas Hydrates at the St. Petersburg Methane Seep (Central Baikal)

Jelly-like microbial mat samples were collected from benthic surfaces at the St. Petersburg methane seep located in Central Baikal. The concentrations of certain ions, specifically chloride, bromide, sulphate, acetate, iron, calcium, and magnesium, were 2–40 times higher in the microbial mats than those in the pore and bottom water. A large number of diatom valves, cyanobacteria, and filamentous, rod-shaped and coccal microorganisms were found in the samples of bacterial mats using light, epifluorescence and scanning microscopy.Comparative analysis of a 16S rRNA gene fragment demonstrated the presence of bacteria and archaea belonging to the following classes and phyla: Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Verrucomicrobia, Cytophaga-Flavobacteria-Bacteroidetes, Cyanobacteria, and Euryarchaeota. The chemical composition and phylogenetic structure of the microbial community showed that the life activity of the mat occurs due to methane and its derivatives involved. Values of δ13C for the microbial mats varied from −73.6‰ to −65.8‰ and for animals from −68.9‰ to −36.6‰. Functional genes of the sequential methane oxidation (pmoA and mxaF) and different species of methanotrophic bacteria inhabiting cold ecosystems were recorded in the total DNA. Like in other psychroactive communities, the destruction of organic substances forming formed as a result of methanotrophy, terminates at the stage of acetate formation in the microbial mats of Lake Baikal (1,400 m depth). Its further transformation is limited by hydrogen content and carried out in the subsurface layers of sediments.

Biologically enabled sub-diffractive focusing

Evolution shows that photonic structures are a constituent part of many animals and flora. These elements produce structural color and are useful in predator-prey interactions between animals and in the exploitation of light for photosynthetic organisms. In particular, diatoms have evolved patterned hydrated silica external valves able to confine light with extraordinary efficiency. Their evolution was probably guided by the necessity to survive in harsh conditions of sunlight deprivation. Here, we exploit such diatom valves, in conjunction with structured illumination, to realize a biological super-resolving lens to achieve sub-diffractive focusing in the far field. More precisely, we consider a single diatom valve of Arachnoidiscus genus which shows symmetries and fine features. By characterizing and using the transmission properties of this valve using the optical eigenmode technique, we are able to confine light to a tiny spot with unprecedented precision in terms of resolution limit ratio, corresponding in this case to 0.21λ/NA.