Diatom Concentrations Research Articles

Glimpsing the 2020 spring bloom in the Strait of Georgia (Canada) with autonomous ferry-based sensors

Spatiotemporal observations are data rich and offer insights into links between ecological patterns and underlying processes. We present fine-scale autonomous observations from repeated ferry transects in the Strait of Georgia (British Columbia, Canada) during the 2020 spring bloom period using a FerryBox system (temperature, salinity, chlorophyll a fluorescence) and a digital inline holographic microscope. Despite instrument cleaning interruptions related to COVID-19 restrictions, 3 periods from late winter (February) to springtime (March and April) contained 14 days of high-quality holograms (>70000) capturing >10500 identifiable micro- to mesoplankton using automatic object detection. The ferry set-up provided automatic data storage through Ocean Networks Canada, which also automatized data flagging and guaranteed remote access. The highest-quality holograms repeatedly covered the central and eastern Strait and showed aspects of bloom succession. Fast-growing diatoms (Skeletonema sp.) emerged first, followed by a diverse assemblage including Chaetoceros spp., Ditylum spp., and Eucampia spp., and by April, larger centric cells prevailed. The combined approach captured local suppression of chlorophyll a fluorescence and diatom concentrations in Fraser River plume waters during the freshet, suggesting fine-scale spatial patterns in seasonal planktonic community composition. This work is among the first of its kind to autonomously generate in situ imaging and physicochemical data with spatiotemporal resolution.

Impacts of climate warming and atmospheric deposition on recent shifts in chironomid communities in two alpine lakes, eastern China

Climate warming and atmospheric deposition are altering alpine lake ecosystems at unprecedented rates, whereas their direct and indirect effects on primary consumer communities are unclear. This study presents sedimentary multi-proxy records including chironomids, diatoms, elements and stable isotopes of carbon and nitrogen in 210Pb-dated cores from two alpine lakes located above the timberline in the Taibai Mountain, eastern China. Before ∼2000 CE, chironomid communities were co-dominated by Heterotrissocladius marcidus-type and Micropsectra atrofasciata-type in the two lakes. Thereafter, Tanytarsus glabrescens-type increased rapidly to be a dominant species. Redundancy analyses (RDAs) revealed that chironomid fauna shifts were significantly correlated with rising diatom concentrations in both lakes, declining Ti content in the upstream lake and δ13C depletion in the downstream lake. Although temperature, precipitation and δ15N were not significant explanatory variables in RDAs, climate warming and atmospheric deposition likely promoted terrestrial and aquatic primary production, indicated by synchronous increases in organic matter contents and diatom concentrations in the two sediment cores. Since diatoms contain essential polyunsaturated fatty acids that are essential for chironomids, rising diatom concentrations can promote food quantity and quality. In addition, increased primary production would create organic substrates for chironomid larvae. Recent shifts in chironomid fauna driven by indirect effects of global warming and atmospheric deposition might be a widespread phenomenon in alpine lakes, probably triggering regime shifts in headwater lake ecosystems.

Tracking Nano- and Microplastics Accumulation and Egestion in a Marine Copepod by Novel Fluorescent AIEgens: Kinetic Modeling of the Rhythm Behavior.

Nano- and microplastics (NMPs) are now prevalent in the marine environment. This study quantified the uptake and depuration kinetics of spherical polystyrene NMPs of different particle sizes (200 nm/30 μm) and functional groups (-NH2/-COOH) in a temperate calanoid copepod Calanus sinicus (C. sinicus), which exhibited rhythmic feeding patterns in natural environments. Aggregated-induced emission (AIE) fluorescent probes were employed to track and quantify the kinetics of NMPs with excellent photostability and biocompatibility. The results showed that C. sinicus consumed all NMPs types, with preference of NMPs to small size and amino group. Increased diatom concentrations also inhibited the bioaccumulation of NMPs. Influenced by rhythmic behavior, the bioaccumulation of NMPs by C. sinicus was nonstationary during the 6 h uptake phase. After 1-3 h of rapid uptake, the body burden peaked and then slowly declined. During the 3 h depuration phase, C. sinicus rapidly and efficiently removed NMPs with a mean half-life of only 0.23 h. To further quantify the body burden of C. sinicus under the influence of rhythmic feeding behavior, a biokinetic model was established, and the Markov chain Monte Carlo method was used to estimate the parameter distribution. Our results highlighted that copepods exhibited unique rhythmic feeding behavior under environmentally relevant concentrations of NMPs exposure, which may influence the bioaccumulation, trophic transfer, and environmental fate of NMPs.

Marine diatoms record Late Holocene regime shifts in the Pikialasorsuaq ecosystem.

The Pikialasorsuaq (North Water polynya) is an area of local and global cultural and ecological significance. However, over the last decades, the region has been subject to rapid warming, and in some recent years, the seasonal ice arch that has historically defined the polynya's northern boundary has failed to form. Both factors are deemed to alter the polynya's ecosystem functioning. To understand how climate-induced changes to the Pikialasorsuaq impact the basis of the marine food web, we explored diatom community-level responses to changing conditions, from a sediment core spanning the last 3800 years. Four metrics were used: total diatom concentrations, taxonomic composition, mean size, and diversity. Generalized additive model statistics highlight significant changes at ca. 2400, 2050, 1550, 1200, and 130 cal years BP, all coeval with known transitions between colder and warmer intervals of the Late Holocene, and regime shifts in the Pikialasorsuaq. Notably, a weaker/contracted polynya during the Roman Warm Period and Medieval Climate Anomaly caused the diatom community to reorganize via shifts in species composition, with the presence of larger taxa but lower diversity, and significantly reduced export production. This study underlines the high sensitivity of primary producers to changes in the polynya dynamics and illustrates that the strong pulse of early spring cryopelagic diatoms that makes the Pikialasorsuaq exceptionally productive may be jeopardized by rapid warming and associated Nares Strait ice arch destabilization. Future alterations to the phenology of primary producers may disproportionately impact higher trophic levels and keystone species in this region, with implications for Indigenous Peoples and global diversity.

Diatom Assemblages from the Daginsky Mud Volcano Sediments (Eastern Sakhalin) and Their Implication

Diatom assemblages in mud volcanoes are quite rare and are poorly studied. The finding of a rich diatom flora in the sediments of the Daginsky Mud Volcano (DMV), located in the tidal zone of the Nyisky Bay of the Sea of Okhotsk, is of interest to study the conditions for the formation of host sediments in the zone of influence of various extreme factors, such as outflows of gases and water–mud mass, thermal springs, and tides. For this purpose, the taxonomical composition of diatom assemblages and concentration of diatoms in DMV sediments were studied. A comparison was made with the diatoms of geothermal springs of the Russian Far East associated with volcanic activity, and the stratigraphic occurrence of the found extinct diatoms was analyzed, which is important for determining their source and the age of the mud volcano roots. Diatom assemblages from DMV sediments are mainly characterized by the predominance of Metascolioneis tumida, Paralia sulcata, Odontella aurita, Pinnunavis yarrensis, Petroneis marina, Cocconeis scutellum, and Navicula digitoradiata. They consist of diatoms of different biotopes and extinct species. The diversity and abundance of brackish water and marine species indicates the predominant influence of sea waters on the formation of DMV sediments. The diverse freshwater species were mainly introduced into sediments with river runoff, but it is likely that some of these, such as the cosmopolitan alkaliphilic species, are inhabitants of geothermal springs. The presence of extinct species from the underlying Neogene sediments from where they were carried with gas–water–mud masses is the most typical for diatom assemblages of the DMV.

Flow Structures With High Lagrangian Coherence Rate Promote Diatom Blooms in Oligotrophic Waters

AbstractDiatoms are among the most efficient autotrophic organisms for oceanic primary production and carbon sequestration. Yet, the spatial distributions of these planktonic organisms remain puzzling and the underlying physical processes poorly known, especially in oligotrophic open waters. Here we investigate what dynamical conditions are conducive to episodic diatom blooms in oceanic deserts based on Lagrangian diagnosis and satellite‐derived phytoplankton functional types and currents. The coherence of the flow is diagnosed in space and time simultaneously through the Lagrangian coherence rate (LCR) to identify which dynamical structures favor diatom growth. Observations evidence that flow structures with high LCR (40 days or longer) in areas with elevated eddy kinetic energy and vorticity sustain high diatom concentrations in the sunlit layers. Our findings show that the integration of Eulerian kinematic variables into a Lagrangian frame reveals new dynamical aspects of geophysical turbulence and unveil their biological impacts.

Influence of the toxicological status on the diagnosis of fatal drowning.

Drowning is the leading cause of death by accident of everyday life in people under 25 years of age. Xenobiotics are frequently involved in drowning cases but their influence on the diagnosis of fatal drowning has not been studied so far. This preliminary study aimed to assess the influence of an alcohol and/or a drug intoxication on the autopsy signs of drowning, and on the results of diatom analyses in drowning deaths. Twenty-eight autopsy cases of drowning including 19 freshwater drownings, 6 seawater drownings, and 3 brackish water drownings were prospectively included. Toxicological and diatom tests were performed in each case. The influence of alcohol and other xenobiotics on drowning signs and diatom analyses was assessed separately then in combination through a global toxicological participation score (GTPS). Diatom analyses showed positive results in lung tissue in every case. No significant association was found between the degree of intoxication and the diatom concentration in the organs, even after considering freshwater drowning cases only. The vast majority of the traditional autopsy signs of drowning were not significantly affected by the individual toxicological status either, with the exception of lung weight which tended to raise in case of intoxication, probably due to the pulmonary edema and congestion increase. Further research on larger autopsy samples is needed to confirm the results of this exploratory study.

Late-Holocene hydrological variability from the NW Himalaya and southwestern Tibetan Plateau: Paleo-salinity records from Pangong Tso

Variations in lake-levels and hydrology are connected to climatic dynamics over the Trans-Himalaya and Tibetan Plateau (TP). Pangong Tso, a ~140 km long hypersaline lake, is sensitive to changes in air temperature, precipitation and snow-glacier melt over the southwestern TP. The incised tributaries entering the lake expose deltaic sequences constituting topset, foreset and bottomset. Sedimentology, chronology and diatom analysis of delta sediments; and stable isotopic and sclerochronological analysis of gastropods helped delineate the Late-Holocene variation in lake levels, surface temperature and salinity. The elevation of the topsets is considered as representing past lake high-stands from where molluscs were also recovered. Three phased lake level changes are observed during the past 3 ka. The first high-stand (+1.4–3.0 m) was at ~2.8–2.0 ka when lake surface salinity and temperature were 4.67–6.01 ppt (parts per thousand) and 5°C–7°C, respectively, against the modern average values of 7.7 ± 0.09 ppt and 16.1°C ± 2.0°C. Followed by a brief decline, another high-stand (+3.0–3.6 m) is observed at 1.1 ka when the salinity is reduced to 4.03–5.72 ppt and lake surface temperature to 5°C–8°C. A corresponding increase in freshwater diatom concentration is also observed here. The third phase over the past 1 ka witnessed a fall of ~3.6–6 m in lake level that is attributed to an abrupt rise in aridity over the TP. We demonstrate that lake level variation in the region is a function of the variability of the Indian Summer Monsoon (ISM) and the westerlies, however during the high-stand, the hydrology of the lake was dominated by ISM precipitation.

Validation and optimization of the diatom L/D ratio as a diagnostic marker for drowning

If a dead body is discovered in water, it nearly always raises the question about the cause of death, often associated with the persistent problem to differentiate between a drowning incident and post-mortem immersion. In numerous cases, a reliable confirmation of death by drowning is often only possible by a combination of diagnoses obtained from autopsy and additional investigations. As to the latter, the use of diatoms has been suggested (and debated) since decades. Based on the consideration that diatoms are present in almost every natural waterbody and are unavoidably incorporated when water is inhaled, their presence in the lung and other tissues can provide evidence of drowning. However, the traditional diatom test methods are still subject of controversial discussion and suspected of erroneous outcome, predominantly through contamination. A promising alternative to minimize the risk of erroneous outcome seems to be disclosed by the recently suggested MD-VF-Auto SEM technique. Especially the establishment of a new diagnostic marker (L/D ratio), which represents the factorial proportion between the diatom concentration in lung tissue and the drowning medium, allows for clearer distinction of drowning and post-mortal immersion and is largely robust to contamination. However, this highly elaborated technique requires specific devices which are frequently unavailable. We therefore developed a modified method of SEM-based diatom testing to enable the use on more routinely available equipment. Process steps such as digestion, filtration, and image acquisition were thoroughly broken down, optimized, and ultimately validated in five confirmed drowning cases. Taking certain limitations into consideration, L/D ratio analysis provided promising results, even in cases of advanced decomposition. We conclude that our modified protocol indeed opens a way for a broader use of the method in forensic drowning investigation.

A palaeoecological study investigating the impacts of multiple tephra depositions on a lacustrine ecosystem in Northeast China, using diatoms as environmental indicators

Tephra layers are common in lake sediments and although they have often been used as chronological controls, few studies have investigated the impacts of past tephra depositions on lake ecosystems (Tephropalaeoecology). For the first time we systematically assess how different types of tephra layers vary in their ecological impact on the same lacustrine system. We use a diatom-based tephropalaeoecological approach to infer the impacts of five tephra deposits on Lake Sihailongwan, a well-studied volcanic lake in Northeast China, over the past 30,000 years. The five tephra layers (including two micro-tephras) have varying thicknesses and were deposited in time periods with different climatic conditions. Changes in diatom communities and chrysophyte-cyst concentrations between pre- and post-tephra samples were used to infer changes in lake conditions and highlight the importance of lake background conditions in mediating the impact of tephra. While the two micro-tephra layers did not cause observable changes, the three thicker tephras induced pronounced changes in lake conditions and thus diatom communities. The two thick tephras deposited in more eutrophic and warmer lake conditions caused larger responses from diatoms. We argue that water-column phosphorus decreased due to reduced sediment–water-phosphorus loading as thick tephra layers formed an impermeable layer at the lake bottom. This is supported by a decrease in total diatom concentration and a decline in high phosphorus-requiring taxa such as Discostella stelligeroides and Stephanodiscus minutulus as well as modern limnological observations which showed that groundwater influxes from the lake bottom are the main source of nutrients to the lake. By contrast, the thick tephra deposited in more oligotrophic and colder lake conditions caused less conspicuous changes. When the lake was already low in phosphorus, diatoms did not respond to a further decline in phosphorus but rather responded to the minor increase in silica from the dissolution of tephra particles in the water column. This was inferred from the slight increases in overall diatom concentration and opportunistic taxa such as Pantocsekiella comensis f. minima. Diatom analysis of the post-tephra sediments above the three thick tephras showed that the aquatic ecosystem did not completely recover, indicating the long-lasting effects of these thick tephras and shifts to new lake-ecosystem equilibria.

Diatoms in Surface Sediments of the Academy Bay of the Sea of Okhotsk

The study of diatoms in the surface sediments of the Academy Bay (Sea of Okhotsk) revealed a rich diatom flora (187 species and intraspecific taxa), represented mostly by marine and brackish water species. The predominance of benthic-planktonic and benthic species indicates a significant role of microphytobenthos in the Academy Bay. The diatom assemblages distinguished with the use of cluster analysis are homogeneous in their taxonomic composition, but differ in ecological structure, which is mainly determined by water salinity. The concentration of diatoms in the sediments in the open part of the Academy Bay and in the apex of the Ulban Bay depends on a high productivity of waters and the lithological composition of sediments. A relatively low content of diatoms in the sediments is associated with the severe climatic conditions of the region that is close to the Arctic.

Diatom–salinity thresholds in experimental outdoor streams reinforce the need for stricter water quality guidelines in South Australia

Water quality guidelines are an important tool for managing environmental pressures on freshwater streams, but guidelines are frequently set using conditions from reference sites that are assumed to be unimpacted. Using biological thresholds potentially provides a better foundation for guidelines. However, guidelines based on field observations alone may be compromised by confounding influences. This study used an outdoor stream mesocosm, an artificial substrate (rope), and six salinity concentrations to assess the veracity of a diatom–salinity threshold determined previously in natural temperate South Australian streams. In addition, shaded treatments assessed the synergistic influences of salinity and reduced sunlight. Salinity had the strongest effect on diatoms, influencing both species and functional compositions. Species diversity and richness, and functional diversity had negative correlations with salinity. Shade strongly reduced diatom concentrations and altered species composition, with no observed interaction between salinity and light. Threshold Indicator Taxa ANalysis indicated a salinity threshold of 1610 μS cm−1 for both shade treatments, lower than the upper limit of the range used in current freshwater guidelines. This study recommends a new candidate guideline of 1600 μS cm−1 for regional freshwater streams and suggests that contemporary methods for deriving water quality guidelines may not adequately protect aquatic health.

Concentration Dependence of Optical Transmission and Extinction of Different Diatom Cultures

Diatoms are unicellular microalgae enclosed in a hierarchically structured silica cell wall that play a significant role in maintaining the health of the planet’s ecosystem. As one of the main photosynthesizers, they are responsible for 20–25% of the world’s oxygen release and carbon fixation. In order to develop technologies for the efficient extraction of carbon dioxide, for example, using bioreactors that provide optimal conditions for the growth of diatoms, it is also necessary to effectively track the diatom lifecycle, as well as control parameters that affect their growth. Here we offer a simple device consisting of LED illumination with a central wavelength of 505 nm that allows to monitor changes in diatom concentrations. We examined marine centric and freshwater pennate diatom strains with different morphologies, sizes, and volumes and obtained a linear dependence of the measured transmission on the concentration. The results were compared with the spectrophotometric approach, which showed a higher inaccuracy with respect to the linear fit. We believe that such an optical setup can be used to solve the problems of continuous flow monitoring of algae both in bioreactors as well as in their natural environment.

Riverine Particulate Matter Enhances the Growth and Viability of the Marine Diatom Thalassiosira weissflogii

Riverine particulates dominate the transport of vital nutrients such as Si, Fe or P to the ocean margins, where they may increase primary production by acting as slow-release fertilizer. Furthermore, the supply of particulate surface area to the ocean is considered to be a major control of organic carbon burial. Taken together, these observations suggest a close link between the supply of riverine particulate material and the organic carbon cycle. To explore this link, we conducted microcosm experiments to measure the growth of the marine diatom Thalassiosira weissflogii in the presence and absence of different types and concentrations of riverine particulate material. Results demonstrate a strong positive effect of riverine particulate material on diatom growth with increased total diatom concentrations and slowed post-exponential death rates with increasing particulate concentration. Moreover, SEM and optical microscope investigations confirm that riverine particulates facilitate organic carbon burial through their role in the aggregation and sedimentation of phytoplankton. The supply of riverine particulate material has been shown to be markedly climate sensitive with their fluxes increasing dramatically with increasing global temperature and runoff. This pronounced climate sensitivity implies that riverine particulates contribute substantially in regulating atmospheric CO2 concentrations through their role in the organic carbon cycle.

Peat sequence diatoms from Kedarnath, Central Himalaya, used to reconstruct mid-late Holocene hydroclimatic conditions

Diatoms preserved in peat can preserve valuable evidence of palaeoenvironmental changes due to their sensitivity to climatic changes and their crucial role in high productivity and nutrient cycling. We present total diatom concentrations and diatom community composition preserved in a high-altitude peat deposit located in the headwaters of the Mandakini River, Central Himalaya, India, to reconstruct the hydroclimatic conditions which prevailed during the mid-late Holocene. Since diatom productivity is associated with water table height/elevation, the high diatom concentrations during ∼5656–5307 cal yr BP, ∼4310–4264 cal yr BP, ∼3515–3024 cal yr BP and ∼ 1679–988 cal yr BP are inferred to have been periods of relatively high water table, denoting improved hydrological conditions. Conversely, low concentrations of diatoms occurred during ∼8077–5866 cal yr BP, ∼5263–4332 cal yr BP, ∼4241–3570 cal yr BP, ∼2970–1715 cal yr BP, and ∼ 697–370 cal yr BP. The temporal changes in the diatom suggest stressed hydrological conditions. The water table fluctuations inferred from diatom concentration variability show a positive correlation with the Indian summer monsoon (ISM) intensity and a negative correlation with the westerlies. The observed low concentrations of diatoms was associated with the relatively dry climatic conditions, which is detrimental to the peat environment and therefore suggests the need for in-situ data monitoring for the Indian peat deposits. As dry conditions can result in the deterioration of peat deposits, which may prove a significant source of atmospheric carbon dioxide in a changing climate, their conservation strategies will help limit carbon emissions.

Siliceous microalgae in the surface sediments of the Shantar region of Sea of Okhotsk

In the surface sediments of the Shantar Region of the Okhotsk Sea revealed a rich diatom flora (187 species and intraspecific taxa), represented mostly by marine and brackish water species. The sediments are dominated by the benthic-planktonic species Paralia sulcata (up to 88,6%), characteristic of sandy sediments, active hydrodynamic regime, desalinated coastal waters of the studied region. The maximum concentration of diatoms (5,8 mln valves/g) was noted in the silts of the Ulban Bay, which is due to the high content of nutrients in the surface and bottom waters of this area. Silicoflagellates are represented by single Octactis speculum and Stephanocha speculum var. minuta.

Inversion model of diatom concentrations in coastal water based on absorption coefficients

Inversion model of diatom concentrations in coastal water based on absorption coefficients

Coupled physical-biogeochemical simulations of upwelling, ecological response to fresh water

An eddy resolving 1/12⁰ coupled physical biogeochemical ocean model configured for the Indian Ocean is used to study the upwelling off the west coast of India, the dynamics of the south eastern Arabian Sea and the associated bio-physical-chemical mechanisms. The model reproduces well the climatological features and local and remotely forced dynamical processes of the upwelling system in physical variables as well as biogeochemical parameters. Modelling experiments show that fresh water from rainfall and river runoff alter the phytoplankton concentration as well as the distribution of the phytoplankton size classes. It is seen that rainfall influences the nanoplankton concentrations while river runoff influences larger diatom concentrations. Fresh water due to rainfall shoals the mixed layer (ML) and thermocline restricting upwelling due to enhanced stratification resulting in reduced nutrient and thereby reduced chlorophyll, essentially nanoplankton. Further a thinner and warmer ML modifies thermodynamics and can consequently influence zooplankton by altering mesozooplankton grazing. River runoff additionally influences by supplying nutrient causing a reduction in diatom and increase in nanoplankton concentrations thus increasing the preferred prey of zooplankton in the SEAS. Our simulations indicate phosphorous limitation in the region. The biophysical controls linking ecological responses to fresh water like zooplankton food preferences are detailed with discussions on implications to food-web dynamics of the region.

Diatom and dinoflagellate cyst distribution in surface sediments of the Chukchi Sea in relation to the upper water masses

Diatom and dinoflagellate cyst analyses were performed on 22 surface sediment samples from the Chukchi Sea to document their geographical distributions in one of the most understudied sections of the Arctic Ocean and to examine the influence of upper water masses on these two major groups of phytoplankton. Total concentrations vary from 0.9 to 5.9 × 106 valves g−1 for diatoms and from 0.8 to 12.5 × 103 cysts g−1 for organic-walled dinoflagellate cysts, with the highest values for both groups observed in the southern part of the Chukchi Sea and away from the Bering Strait. Well-preserved microfossils were recovered, with a total of 35 and 88 taxa of dinoflagellate cysts and diatoms, respectively. The most abundant diatoms are Paralia sulcata, Thalassiosira antarctica, Thalassiosira nordenskioeldii, and resting spores of Chaetoceros spp., whereas cysts of phototrophic Alexandrium spp., Operculodinium centrocarpum sensu Wall and Dale (1966), and heterotrophic Islandinium minutum and Brigantedinium spp. were most common in the dinoflagellate cyst assemblages. Cysts of HAB-causing Alexandrium spp. were found in most of the samples, with the highest abundances in Herald Canyon where they contribute ∼56.6% to the cyst assemblage. As expected, cysts produced by heterotrophic dinoflagellates were more abundant where sedimentary diatom concentrations were the highest.Statistical analysis identified three major diatom and dinoflagellate cyst clusters: 1. Sites influenced by the Alaska Coastal Current in the eastern part of the Chukchi Sea are characterized by high abundances of P. sulcata and O. centrocarpum sensu Wall and Dale (1966); 2. The western part and Herald Canyon in the northern part of the Chukchi Sea are distinguished by diatoms Chaetoceros spp., T. antarctica and dinoflagellate cysts of Alexandrium spp. and affected by the Siberian Coastal Current and Bering Shelf Water; and 3. Assemblages in the southern part of the Chukchi Sea are recognized by noticeable abundances of T. nordenskioeldii and cryophilic diatom taxa, and dinoflagellate cysts I. minutum, as well as by overall lower percentages of cysts of Pentapharsodinium dalei and Brigantedinium spp. This work revealed the potential applicability of the combined use of diatoms and dinoflagellate cysts for reconstructions of past dynamic water mass changes in the Chukchi Sea.

Thermogravimetric Analysis of Marine Macroalgae Waste Biomass as Bio-Renewable Fuel

Macroalgae are considered as the 3rd generation of biofuels and a future feedstock for biorefinery. This research aims to provide simple and dependable analytical techniques for measuring the thermal characteristics of dried seaweed. The main objective was to investigate the thermal characteristics of four seaweed species utilizing a thermogravimetric analyzer. The seaweeds Gracilaria fisheri, Caulerpa lentillifera, Ceramium rubrum, and Eucheuma cottonii were collected from the Pahang state of Peninsular Malaysia. The calorific value of the samples was revealed by using a calorimeter. Ceramium rubrum showed the highest calorific value, while Gracilaria fisheri had the most negligible calorific value among the selected samples. The thermogravimetric analysis (TGA) data revealed that the most significant weight loss for this biomass occurred between 160 and 300° for the selected species. Gracilaria fisheri has shown the highest decomposition with the minor residue at 30.26%, whereas Caulerpa lentillifera has a slow weight loss rate in the mentioned range. SEM analysis has been used to perform the morphology of samples, which shows differences in the concentration of epiphytic diatoms with different structural shapes. Based on the results, macroalgae is a promising sustainable biomass feedstock for biofuel application.