Diatoms In Waters Research Articles

Diversity, toxicity, and distribution of potentially toxic diatoms in Antarctic waters––With description of Pseudo-nitzschia meridionalis sp. nov. and P. glacialis sp. nov.

Diatoms of the genus Pseudo-nitzschia, known for their potential toxicity, are integral to the phytoplankton community of the Southern Ocean, which surrounds Antarctica. Despite their ecological importance, the diversity and toxicity of Pseudo-nitzschia in this region remain underexplored. Globally, these diatoms are notorious for forming harmful algal blooms in temperate and tropical waters, causing significant impacts on marine life, ecosystems, and coastal economies. However, detailed information on the diversity, morphology, and toxicity of Pseudo-nitzschia species in Antarctic waters is limited, with molecular characterizations of these species being particularly scarce.During three research expeditions to the Southern Ocean, monoclonal strains of Pseudo-nitzschia were isolated and cultivated. Stored samples from a fourth expedition, the Brategg expedition, were used to complete the description of particularly P. turgidula. Through electron microscopy and molecular analysis, two novel species were identified—Pseudo-nitzschia meridionalis sp. nov. and Pseudo-nitzschia glacialis sp. nov.—alongside the previously described species P. subcurvata, P. turgiduloides, and P. turgidula. Toxin assays revealed no detectable levels of domoic acid in P. turgiduloides, P. turgidula, P. meridionalis sp. nov. and P. glacialis sp. nov. Conversely, P. subcurvata was reported in a related study to produce domoic acid and its isomer, isodomoic acid C.These findings emphasize the need for comprehensive research on the phytoplankton of Antarctic waters, which is currently a largely uncharted domain. With the looming threat of climate change, understanding the dynamics of potentially harmful algal populations in this region is becoming increasingly critical.

The impact of flooding from the Minjiang River on the succession of harmful algal blooms (HABs) caused by diatoms in China's offshore waters

This study examines diatom assemblages in the Matsu Archipelago, an area influenced by Minjiang River runoff. It focuses on harmful algal blooms (HABs) that occurred between August 2021 and July 2022. Utilizing 18S rRNA metabarcoding and microscopic analysis, we observed a significant diatom bloom during early summer runoff, peaking at 5 × 105 cells L−1. The research reveals dynamic community changes during the runoff season, with dominant genera including Pseudo-nitzschia, Chaetoceros, and Skeletonema. Skeletonema cell density correlated with NO3 levels, Chaetoceros had a slight PO4 affinity, and Pseudo-nitzschia showed a negative correlation with Skeletonema. Pseudo-nitzschia, which prefers high light and pH conditions, had notably high concentrations in the flood season and in the autumn. In both, it was dominated by potential toxin-producing species - P. multistriata and P. pungens during the flooding, and P. cuspidate in the autumn. These findings highlight the intricate relationship between diatom dynamics and environmental factors, providing essential insights for managing HABs, especially Pseudo-nitzschia species, amidst environmental changes.

Phytoplankton growth and grazing dynamics during anomalous heat wave and suppressed upwelling conditions in the southern California Current

We investigated phytoplankton dynamics in the southern California Current System (SCCS) in August 2014 during the early phase of the 2014-15 marine heat wave (MHW). Multi-day experiments were conducted at three inshore and two offshore sites, with daily depth profiles of dilution incubations on a drifting array to determine growth and grazing rates and shipboard assessments of nutrient effects. Picophytoplankton populations were analyzed by flow cytometry and eukaryotic phytoplankton by 18 S sequencing. Mixed-layer nutrients were low across the region, but inshore sites had substantial nitrate concentrations and prominent Chla maxima in the lower euphotic zone. Shoreward transport of warm-stratified waters from the offshore suppressed coastal upwelling and shifted picophytoplankton distributions toward increased onshore abundance of Prochlorococcus and decreased Synechococcus and picoeukaryotes. These trends were reinforced by higher-than-average growth of Prochlorococcus at inshore sites and higher grazing of Synechococcus and picoeukaryotes. Prasinophytes (Chlorophyceae) were notably important among eukaryotic taxa, and pennates replaced centric taxa as the dominant diatoms in inshore waters compared to normal upwelling. Despite substantial spatial variability in community composition, offshore and inshore experimental locations both showed growth-grazing balances, with microzooplankton consuming similar percentages (80%) of primary production. We thus confirm expectations that the 2014-15 MHW resulted in greater trophic flow through the microbial food web at the expense of reduced direct phytoplankton (Chla) consumption by mesozooplankton. However, impacts on mesozooplankton energy budgets were partially offset by increased trophic flow through protistan microzooplankton and higher phytoplankton C:Chla.

The Antarctic Silicon Trap

The Southern Ocean, the ocean encircling Antarctica, has been described by explorers as cold, empty, and dangerous. Despite this, it is a paradise for tiny algae called diatoms that are crucial players in the regulation of our climate. Why are these tiny organisms so happy in this cold and far away ocean? Diatoms have a solid shell made of a glass-like material called silica, so they need to find silicon in surface waters to build it. The Southern Ocean is the perfect place for diatoms because it is full of silicon compared to the other oceans. This is due to a special phenomenon called the silicon pump, which makes the Southern Ocean a giant trap for silicon. In this article, we point out the central role of the Southern Ocean in the regulation of Earth’s climate and how it controls the distribution of silicon and the wellbeing of diatoms in Antarctic waters.

Evaluation of heterocyte glycolipids with a hexose sugar moiety for tracing terrestrial organic matter in the South China Sea

Heterocyte glycolipids (HGs) are biomarkers for N2-fixing heterocytous cyanobacteria (HCB). The hexose (hereafter C6) sugar moiety of HGs is produced by free-living HCB dominant in fresh and brackish waters, while the pentose moiety (hereafter C5) of HGs is found in endosymbiotic HCB associated with diatoms in tropical-subtropical marine waters. Therefore, C6 HGs detected in marine environments may indicate terrestrial organic matter (TOM) input, but this may be complicated by the fact that free-living HCB may be active over a wide salinity range. In this study, we evaluate C6 HGs and their fraction in total HGs, referred to as FHG, to trace TOM in the South China Sea (SCS) by analyzing a series of surface sediments from the Pearl River Estuary (PRE) to the open SCS, as well as suspended particular matters (SPM) in the euphotic zone of central SCS and a sediment core 17950-2 in the deep SCS. Our results showed that C6 HGs were abundant in the PRE sediments but almost absent in sediments or SPM from the northern shelf to the central SCS, leading us to conclude that free-living HCB producing C6 HGs are inactive in the modern ocean where salinity is >30. In the sediment core, C6 HGs and FHG showed a variation pattern similar to sea level changes during glacial-interglacial cycles, and the reconstructed sea surface salinity was above 32 throughout the cycles. Such a pattern was also evident in the records of branched to isoprenoid tetraether (BIT) index and detrital content from the same core. Thus, the modern distribution of C6 HGs and FHG, together with their downcore records in this study, demonstrates that C6 HGs and FHG are excellent for tracking TOM in tropical-subtropical marine environments.

Changes in the Composition of Bloom-Forming Toxic Pseudo-nitzschia Diatoms in Surface Waters in Ussuri Bay, Northwestern Sea of Japan, during the Autumn Seasons of 2017–2022

Diatoms of the genus Pseudo-nitzschia are producers of the neurotoxin domoic acid that causes serious damage to marine fauna and aquaculture farms. These microalgae are known as the most abundant group of toxic phytoplankton in Peter the Great Bay, Northwestern Sea of Japan, during the bloom season, which, as was previously reported for members of this group in the study region, lasts in the autumn months. Autumnal blooms of toxic diatoms Pseudo-nitzschia spp. were studied in the period from 2017 to 2022 in Ussuri Bay, the largest body of water in Peter the Great Bay, which harbors numerous recreational area and aquaculture farms. As a result, the following changes in the composition of bloom-forming species were recorded: blooms were caused by the Pseudo-nitzschia delicatissima group in the period from 2017 to 2020 and by P. multistriata in 2021–2022. An assumption has been made that one of the factors responsible for blooms of P. multistriata, known as one of the most widespread species in Asian warm-water areas, is an abnormally high water temperature in the autumn of 2021 in the study area.

Effects of Algal Blooms on Phytoplankton Composition and Hypoxia in Coastal Waters of the Northern Yellow Sea, China

Summer hypoxia and harmful algal bloom occurred sometimes in the nearshore of the northern Yellow Sea in recent years. Based on seven multidisciplinary investigations conducted from March to November 2016, except for April and October, the phytoplankton community and its association with ambient seawater physicochemical parameters in coastal waters of the northern Yellow Sea were comprehensively examined. In total, 39 taxa belonging to 4 phyla and 24 genera were identified. Diatoms and dinoflagellates were the dominant groups, which accounted for 64.1% and 30.8% of total species, respectively. An algal blooming event dominated by the diatom (Thalassiosira pacifica) occurred in March, which affects the shifting of diatom–dinoflagellate dominance. A notable dinoflagellate dominance occurred especially in surface water throughout the whole summer but changed to diatom dominance again from September. Hypoxic zones (<2 mg l-1)were observed in the bottom water in August, with minimum dissolved oxygen (DO) of 1.30 mg l-1. This low DO zone in August was clearly associated with the diatom blooming event (Thalassiosira pacifica) in March, as diatoms in surface waters sank into bottom waters and decomposed by the microbial community resulting in oxygen consumption. After the early-spring diatom bloom, thermohaline stratification occurred and prevented exchanges of dissolved oxygen, which eventually led to hypoxia in bottom waters. The effects of algal blooms on phytoplankton composition and hypoxia could have a cascaded effect on the fishery sustainability and aquaculture in nearshore waters of the northern Yellow Sea.

The Relationship of Nitrate, Phosphate, and Silicate Concentrations to The Abundance of Planctonic Diatoms in Carocok Tarusan Waters, Pesisir Selatan District

This research was carried out from December 2020 to January 2021 in Carocok Tarusan Waters, Pesisir Selatan Regency, West Sumatra, which aims to analyze the concentration of nitrate, phosphate and silicate, calculate the abundance of planktonic diatoms and analyze the relationship between the content of nitrate, phosphate and silicate to the abundance of planktonic diatoms present. in the waters of Carocok Tarusan, Pesisir Selatan Regency. The research method used in this study is a survey method while the determination of research stations is carried out by purposive sampling. The results showed that the average nitrate concentration was 0.7792– 0.8757 mg/L, the average phosphate concentration was 1.7220– 2.0833 mg/L and the silicate concentration was 0.6287 - 0.6835 mg/L. Planktonic diatoms found in Carocok Tarusan waters contained 13 species from 3 classes, namely Bacillariophyceae, Chaetoceraceae, and Coscinodiscophyceae. The results of the calculation of the abundance of planktonic diatoms are 17.82 – 20.72 Ind/L. The test conducted to determine the relationship of nitrate, phosphate, and silicate to the abundance of planktonic diatoms was a simple linear regression test. Based on the results of the linear regression test, it is known that the effect of nitrate concentration on the abundance of planktonic diatoms in Carocok Tarusan waters is 00.81%, while the remaining 99.19% is influenced by other factors, for the effect of phosphate concentration on the abundance of planktonic diatoms in Carocok waters. Tarusan is 8.81%, while the remaining 91.19% is influenced by other factors and for the effect of silicate concentration on the abundance of planktonic diatoms in Carocok Tarusan waters as much as 2.97%, while the remaining 97.03% is influenced by other factors

Shunt or shuttle

Nutrient availability influences the susceptibility of marine primary producers to viral infection. For diatoms in iron-limited waters, reduced infection rates impact marine biogeochemical cycles by enhancing the flux of material to depth.

Infection of marine diatom Coscinodiscus wailesii (Bacillariophyceae) by the parasitic nanoflagellate <i>Pirsonia diadema</i> (Stramenopiles) from Yongho Bay in Korea

The infection of marine diatom Coscinodiscus wailesii by a parasitic protist from the Yongho Bay of Busan, Korea was observed during the diatom bloom events in 2017 through 2018. The morphological and molecular features suggested that the parasitic nanoflagellate Pirsonia diadema was responsible for the infection. During the study period, the parasite prevalence ranged from 0.3% to 3.3%, and infected C. wailesii cells were observed only at surface seawater temperatures ranging between 10.9 and 19.9°C, although the host population appeared at temperatures above 25°C. The parasite and host system was successfully established as cultures. Using the cultures, we determined the morphological features over the infection cycle, parasite generation time, parasite prevalence as a function of inoculum size, and zoospore infectivity and survival time. The diatom C. wailesii was readily infected by the parasite P. diadema, with a parasite prevalence reaching up to 100% and a zoospore to host inoculum ratio above 20 : 1. The survival and infectivity of the parasite zoospores decreased with age. While the zoospores could survive up to 88 hours, they quickly lost their ability to infect after 48 hours. These results could lead to a better understanding of the biology and ecology of the parasitoid infecting the giant-sized diatoms in coastal waters.

Phytoplankton community structure in a contrasting physico-chemical regime along the eastern Arabian Sea during the winter monsoon

Abstract The paper describes the community composition of phytoplankton in the eastern Arabian Sea (EAS) during winter monsoon (WM, January–February 2018), encompassing the entire eastern part of the Arabian Sea basin (~6–22°N and 77–67°E) with high-resolution sampling (7 transects, 56 sites), from coastal to offshore regions. The phytoplankton pigment concentrations estimated by high-performance liquid chromatography were interpreted using ‘CHEMTAX’ (Mackey et al., 1996) to determine relative abundance and contribution of phytoplankton functional groups at the class level. A distinct spatial heterogeneity was observed in the distribution of phytoplankton groups in the coastal and offshore regions of the northern as well as southern part of the EAS. The basin-scale column integrated chlorophyll a (Chl a) concentration in the upper 100 m was higher (16–118 mg m−2) in the northeastern Arabian Sea (NEAS) as against 9–79 mg m−2 in the southeastern Arabian Sea (SEAS). The chromatographic analysis revealed the dominance of diatoms in the coastal waters of the EAS basin. A closer evaluation of the hydrodynamics and nutrient chemistry of the offshore regions revealed that entrainment of sub-halocline nutrients into the sunlit water column through convective mixing supported the dominant cyanobacterial population in the NEAS. In the warm oligotrophic waters of the SEAS, the substantially high NH4+ concentration indicates that the dominant prochlorophytes were sustained by the regenerated production. The dominance of large phytoplankton like diatoms indicates a herbivorous control in the food chain in coastal waters of the EAS. Offshore waters are characterised by large proportions of pico-nano plankton along with considerable micro phytoplankton, which suggests a mixotrophic ecosystem. The statistical analysis showed that the silicate (Si/N ratio) concentration played a major role in controlling the diatom abundance in the coastal areas of the north (south) EAS while temperature and salinity together with nutrients structured the phytoplankton assemblage in the offshore waters during WM.

Temporal variations in abundance and species richness of phytoplankton with emphasis on diatoms in the subtidal waters of Umm Al-Namil Island, north-western Arabian Gulf of the ROPME Sea Area

Aim: The present study aimed to understand the physico-chemical factors affecting the abundance and species richness of phytoplankton communities, with emphasis on diatoms at the end of the intertidal zone and start of subtidal zone. Methodology: Water quality and phytoplankton community species richness and abundance were measured in the subtidal waters of Umm Al-Namil Island, Kuwait Bay. Kruskal-Wallis statistical approach was used to measure the effect of various environmental parameters on abundance and species richness as well as abundance-species richness relationships using R statistical software. Results: The physico-chemical parameters showed variations at each sampling event as well as within the same season. Total phytoplankton mean abundance values in summer (22.26 ± 0.66 ind. 5l-1) and winter (21.63 ± 0.52 ind. 5l-1) did not significantly vary and the lowest mean abundance was observed during spring (26.36 ± 0.33 ind. 5l-1). Species abundance showed clear pattern with the events, resulting in somehow a negative relationship. Mean species richness was highest during autumn (24.59 ± 1.51), while no significant difference was observed between spring (11.09 ± 0.33), winter (10.47 ± 0.51) and summer (10.11 ± 0.66). The results indicate that phytoplankton species richness and species abundance in Umm Al-Namil Island varied temporally in response to fluctuations in environmental conditions. Interpretation: The end of intertidal zone and beginning of subtidal zone is affluent in diverse forms of phytoplankton species, specifically diatoms since Kuwait Bay is a eutrophic area mainly due to sewage and urbanization. Therefore, a temporal monitoring is required in order to observe any changes in either physico-chemical or biological factors with time and that will help in future conservation and restoration programs. Conservation approaches should be considered seriously since some diatoms like Melosira moniliformis, Gyrosigma diminutum, Fragilaria martyi, Hemidiscus cuneiformis, Planktoniella sol and Amphiprora plicata have been observed only at one event despite abundance and season.

Benthic Diatoms of the Russian Waters of the Sea of Japan and Adjacent Sea Areas

This review analyzes the current state of knowledge of the microphytobenthos in the Russian waters of the Sea of Japan and adjacent sea areas. A retrospective analysis of the literature shows that microphytobenthos, with its primary production that often exceeds the production of phytoplankton, plays an important role in coastal marine ecosystems. Benthic diatoms in the coastal waters of Peter the Great Bay (Sea of Japan), which are the primary food object for many marine invertebrates and mammals, are also used as important indicators of the state of the aquatic environment. Despite the great number of publications on the region, knowledge of the microphytobenthos in taxonomic and ecological-floristic aspects is still insufficient.

ANALYSIS OF NITRATE CONCENTRATION, PHOSPHATE AND SILICATE RELATIONSHIP WITH THE ABUNDANCE OF PLANKTONIC DIATOMS IN MERAL WATERS, KARIMUN DISTRICT

Input of nutrients into the waters from various human activities (residential and industry) has the potential to cause changes in the physical, chemical and biological conditions of the waters. The study aims to determine the relationship of concentrations of nitrate, phosphate and silicate with the abundance of diatoms in the Meral waters. The method used is the survey method, the determination of the location of sampling is done by purposive sampling, data analysis (multiple regression). Based in the results of laboratory analysis nitrate concentrations ranged from 0,033 – 0,051mg/l, the phosphate concentration ranged from 0,076 – 0,086 mg/l, and silicate concentration ranged from 0,043 – 0,052 mg/l. The abundance of diatoms in Tanjung Tiram waters ranged from 90,3 – 208,3 ind/l. The results of statistical analysis of the relationship of nitrate, phosphate and silicate with the abundance of diatoms are expressed in terms of equation y = 58,460 + 904,562Nitrate – 251,562phosphate + 1573,489Silicate. This statement explains the concentration of nitrate, silicate positive (+) to the abundance of diatoms and phosphate related negative (-) to the abundance of diatoms. This condition shows that the nutrient concentration in these waters is relatively high so that it affects the abundance of diatoms.

Community composition and photosynthetic physiology of phytoplankton in the western subarctic Pacific near the Kuril Islands with special reference to iron availability.

The western subarctic Pacific (WSP) is known as one of the most productive regions among the world's oceans in spring. However, its oceanic waters are also known as a High Nutrient, Low Chlorophyll (HNLC) region during summer due to low iron (Fe) availability in seawater. Indeed, recent studies have demonstrated that the distribution of Fe in the WSP is complex and heterogeneous. This study thus investigated the effects of Fe availability on the community composition and photophysiology of surface phytoplankton from coastal to offshore waters in the WSP in the summer of 2014. Although relatively high concentrations (>2 mg m-3) of chlorophyll (chl) a were found in the Sea of Okhotsk and some coastal waters, low chl a concentrations (<1 mg m-3) were commonly observed in offshore waters. Based on dissolved Fe and macronutrient concentrations, we deduced that low Fe availability limited phytoplankton growth in offshore waters, whereas low silicate and/or nitrate levels limited growth in the shelf areas. Scanning electron microscopy also revealed that the centric diatom Chaetoceros exclusively dominated the diatom assemblages in the shelf and coexisted with pennate diatoms in offshore waters, respectively. Primary productivity in surface waters was negatively correlated with the bottom of the euphotic layer or the light saturation index of the photosynthesis-irradiance curve, which indicates that the phytoplankton assemblages were well acclimated to in situ light conditions regardless of the water masses.

Factors regulating primary producers' assemblages in Posidonia oceanica (L.) Delile ecosystems over the past 1800 years

Posidonia oceanica (L.) Delile meadows are highly productive coastal marine ecosystems that provide multiple ecosystem services. The seagrass is not always the major contributor to total primary production, however, little is known about long-term changes in the composition of primary producers within seagrass meadows. Understanding compositional shifts within the community of primary producers is crucial to evaluate how climate and anthropogenic change affect the functioning of seagrass ecosystems. Here we analysed marker pigment composition in seagrass cores from two bays of the Cabrera Island (Balearic Islands, Spain) to asses long-term changes in phototrophic community composition and production in seagrass meadows, and identify the environmental factors triggering those changes. The proxy dataset was explored using principal component analyses (PCA): one including the pigment dataset to look for associations between producers' groups, and another one combining the pigment dataset with plausible local and global regulatory factors to assess the environmental drivers of change. Analyses of characteristic pigments and morphological fossils (cysts) showed that the abundance of dinoflagellates increased over the last 150–300 years, coeval with a rise in solar irradiance and air temperature. When compared among embayments, pigments from cyanobacteria predominated in seagrass meadows located at Es Port, a sheltered bay receiving higher terrestrial runoff; whereas pigments from diatoms, seagrasses and rodophytes were more common at Santa Maria, an exposed bay with clearer waters. Water depth also played a role in controlling the phototrophic community composition, with greater abundance of diatoms in the shallowest waters (<5 m). Overall, our results suggested that historical and spatial variation in seagrass meadows' phototrophic community composition was influenced by the interaction between local factors (catchment-bay characteristics) and global climate processes (energy influx). Together these patterns forecast how marine primary producers and seagrass ecosystem structure may respond to future global warming.

Interactive effects of warming and eutrophication on population dynamics and stalk production of epiphytic diatoms in transitional waters

The interactive effects of temperature and nitrogen:phosphorus stoichiometry were assessed by an experiment that involves cultures of the stalked epiphytic diatom Licmophora colosalis at different N:P ratios (5, 10, 16, 21 and 42) and temperatures (26, 31 and 36 °C) to simulate predictions of global warming effects on a Mediterranean coastal lagoon. At 26 °C, which seemed optimal for L. colosalis, it grew well at the N:P ratios within the 16–21 range, but a different stoichiometry reduced cell growth. The 5 °C increase had deleterious effects on diatom fitness as growth reduced, mortality increased and carbohydrates accumulation amplified under N or P deficiency. In contrast, this temperature stress was better overcome at N:P = 16. The 36 °C temperature proved lethal. Stalk production was specifically stimulated when growth was P-limited at both 26 °C and 31 °C, which suggests that a high proportion of stalks, which would form macroscopic colonies, may serve as an indicator of warming and high N:P ratios in transitional waters.

Diatoms (Bacillariophyta) as bio-indicators

Bio-indicators such as diatoms from algae considered to be key factors in ecological studies as an assessment of freshwater ecology. Algae are very sensitive to environmental changes and reflect the spatiotemporal changes on exists or biomass of diatoms in waters. Diatoms have been used not just for the assessment of water quality, but also can be used as an organic pollution indicator in the freshwater ecosystems, such as algal water bloom. The reason for using diatoms as bio-indicators was for several characteristics such as rapid growth, and represent high biomass in the freshwater ecosystem. Also, diatoms have high biodiversity among the other aquatic biota and energy flow and cycling. Compared with the other aquatic biota, diatoms reflect ecological disturbance due to high sensitivity to light, temperature, water flow, pH, and oxygen content. Additionally, diatoms are used as an assessment of eutrophication, organic pollution and climate change.

Determination of trophic weight and indicator values of diatoms in Turkish running waters for water quality assessment

This study, the first such attempt in Turkey, aimed to investigate the distribution of diatom species related to the variation of total phosphorus (TP) in eight basins to determine trophic weight and indicator values of diatom species and to develop the Trophic Index-Turkey (TIT) for assessing the ecological status of freshwaters. The distribution of the diatom species in 225 running water bodies from 8 basins of Turkey was determined in 2014 (summer and fall) and 2015 (spring and summer) in association with TP variation. Trophic values for 219 species were determined during this study and many of these are presented for the first time. Optima and tolerance TP values were calculated for each species in the different aquatic ecosystems using weighted average regression. Diatom species such as Clevamphora ovalis , Caloneis amphisbaena , Gyrosigma acuminatum , Navicula tripunctata , and Nitzschia umbonata showed high trophic weight values, while Achnanthidium minutissimum , Cymbella excisa , Didymosphenia geminata , Hannaea arcus , and Meridion circulare had low trophic weight values. These findings provide supplementary information about the biotic integrity of the water bodies and could be used to develop the TIT for the bioassessment of freshwater ecosystems, especially running water bodies.

Composición, abundancia y distribución de Diatomeas en dos localidades de la provincia del Guayas entre octubre 2013 y febrero 2014.

El presente trabajo se desarrolló en dos localidades de la Provincia del Guayas entre octubre y febrero 2014. El objetivo de esta investigación fue comparar la composición, abundancia y distribución de diatomeas centrales en las aguas estuarinas de la parroquia Posorja y en el Cantón General Villamil Playas de influencia oceánica. Los arrastres superficiales se realizaron quincenalmente a bordo de una embarcación un motor de 75 HP a una velocidad de 2 nudos, en un tiempo de 5 minutos de recorrido por cada estación a 1 milla de la orilla del mar. En total se identificaron 71 especies en las que predominan las Diatomeas Centrales con 60 especies y se registraron 11 especie de Diatomeas Pennales, la especie con mayor densidad. Chaetoceros coarctatus, mayor densidad poblacional con 15576 cel. 100m3, correspondiendo al 12,80% en las dos áreas muestreadas de un total de 36 muestras colectadas. Mediante el índice de Shannon – Wiener se muestra una similitud entre estaciones. En Posorja hubo irregularidad en todas las estaciones, coincidente con el índice de Simpson que registró que no hay similitud entre estaciones. La abundancia y distribución corresponde al 51% de las Diatomeas del orden Centrales en Posorja en tanto el 49% concierne a General Villamil.&#x0D;