Functional classification of phytoplankton could be a valuable tool in water quality monitoring in the eutrophic riverine ecosystems. This study is novel from the Bangladeshi perspective. In this study, phytoplankton cell density and diversity were studied with particular reference to the functional groups (FGs) approach during pre-monsoon, monsoon, and post-monsoon at four sampling stations in Karatoya River, Bangladesh. A total of 54 phytoplankton species were recorded under four classes, viz. Chlorophyceae (21 species) Cyanophyceae (16 species), Bacillariophyceae (15 species), and Euglenophyceae (2 species). A significantly higher total cell density of phytoplankton was detected during the pre-monsoon season (24.20 × 103 cells/l), while the lowest in monsoon (9.43 × 103 cells/l). The Shannon-Wiener diversity index varied significantly (F = 16.109, P = 000), with the highest value recorded during the post-monsoon season. Analysis of similarity (ANOSIM) identified significant variations among the three seasons (P phytoplankton species recorded during the study period were classified into 20 functional groups, whereas D/J/M/MP/X1 was considered the most abundant FG in the Karatoya River. FGs of the Karatoya River were influenced mainly by the nutrients (PO4-P and NO3-N) enrichments. As a novel investigation on FGs of phytoplankton in Bangladesh, this study recommends additional surveys in other rivers and floodplains to improve our understanding of phytoplankton diversity and functional groups.
Metabarcoding analysis is an effective technique for monitoring the domoic acid-producing Pseudo-nitzschia species in marine environments, uncovering high-levels of molecular diversity. However, such efforts may result in the overinterpretation of Pseudo-nitzschia species diversity, as molecular diversity not only encompasses interspecies and intraspecies diversities but also exhibits extensive intragenomic variations (IGVs). In this study, we analyzed the V4 region of the 18S rDNA of 30 strains of Pseudo-nitzschia multistriata collected from the coasts of China. The results showed that each P. multistriata strain harbored about a hundred of unique 18S rDNA V4 sequence varieties, of which each represented by a unique amplicon sequence variant (ASV). This study demonstrated the extensive degree of IGVs in P. multistriata strains, suggesting that IGVs may also present in other Pseudo-nitzschia species and other phytoplankton species. Understanding the scope and levels of IGVs is crucial for accurately interpreting the results of metabarcoding analysis.
In this article, the abundance of phytoplankton community structure in Malacca Straits (MS); from Port Klang to Langkawi Island are reported. The datasets include data from 25 selected sampling sites that were acquired in August 2019 on board the RV Discovery's cruise expedition. These data contain details on the density of phytoplankton (cell L-1), total number of species, volume seawater filtered (in L) and the concentration factors (ml) in MS. Data presented in this article consists of 163 species, including unidentified species from 6 phyla of phytoplankton, along with the percentage of a major community group in MS.
Pseudo-nitzschia is a cosmopolitan phytoplankton genus of which some species can form blooms and produce the neurotoxin domoic acid (DA). Identification of Pseudo-nitzschia is generally based on field material or strains followed by morphological and/or molecular characterization. However, this process is time-consuming and laborious, and can not obtain a relatively complete and reliable profile of the Pseudo-nitzschia community, because species with low abundance in the field or potentially unavailable for culturing may easily be overlooked. In the present study, specific ITS primer sets were designed and evaluated using in silico matching. The primer set ITS-84F/456R involving the complete ITS1 region was found optimal. Based on matching with a Pseudo-nitzschia ITS1 reference sequence database carefully-calibrated in this study, a metabarcoding approach using annotated amplicon sequence variants (ASV) was applied in the Taiwan Strait of the East China Sea during two cruises in the spring and summer of 2019. In total, 48 Pseudo-nitzschia species/phylotypes including 36 known and 12 novel were uncovered, and verified by haplotype networks, ITS2 secondary structure comparisons and divergence analyses. Correlation analyses revealed that temperature was a key factor affecting the seasonal variation of the Pseudo-nitzschia community. This study provides an overview of the Pseudo-nitzschia community in the Taiwan Strait, with new insights into the diversity. The developed metabarcoding approach may be used elsewhere as a standard reference for accurate annotation of Pseudo-nitzschia.
Zooplankton are major consumers of phytoplankton primary production in marine ecosystems. As such, they represent a critical link for energy and matter transfer between phytoplankton and bacterioplankton to higher trophic levels and play an important role in global biogeochemical cycles. In this Review, we discuss key responses of zooplankton to ocean warming, including shifts in phenology, range, and body size, and assess the implications to the biological carbon pump and interactions with higher trophic levels. Our synthesis highlights key knowledge gaps and geographic gaps in monitoring coverage that need to be urgently addressed. We also discuss an integrated sampling approach that combines traditional and novel techniques to improve zooplankton observation for the benefit of monitoring zooplankton populations and modelling future scenarios under global changes.
Life cycle assessment was used to evaluate the environmental impacts of phytoplanktonic biofuels as possible sustainable alternatives to fossil fuels. Three scenarios were examined for converting planktonic biomass into higher-value commodities and energy streams using the alga Scenedesmus sp. and the cyanobacterium Arthrospira sp. as the species of interest. The first scenario (Sc-1) involved the production of biodiesel and glycerol from the planktonic biomass. In the second scenario (Sc-2), biodiesel and glycerol were generated from the planktonic biomass, and biogas was produced from the residual biomass. The process also involved using a catalyst derived from snail shells for biodiesel production. The third scenario (Sc-3) was similar to Sc-2 but converted CO2 from the biogas upgrading to methanol, which was then used in synthesizing biodiesel. The results indicated that Sc-2 and Sc-3 had a reduced potential (up to 60 % less) for damaging human health compared to Sc-1. Sc-2 and Sc-3 had up to 61 % less environmental impact than Sc-1. Sc-2 and Sc-3 reduced the total cumulative exergy demand by up to 44 % compared to Sc-1. In conclusion, producing chemicals and utilities within the biorefinery could significantly improve environmental sustainability, reduce waste, and diversify revenue streams.
Temporal variations and regional distributions of dissolved nutrients and their elemental ratios in the Iranian coastal waters of the Southern Caspian Sea were investigated. The data were collected in 1996-97 (Phase I, as a background data and undisturbed ecosystem) and in 2005 (Phase II, as a disturbed ecosystem) at sampling points (from 10 to 100 m depths). In addition to the two main sampling exercises, additional sample collections were carried out during the period of 1994 to 2004 as a long-term study. This study showed that the dissolved inorganic nitrogen/dissolved inorganic phosphorus (DIN/DIP) ratios in the southern Caspian Sea vary within a very narrow range (4.47 to 5.78) within the euphotic and aphotic layers and is by one order of magnitude lower than what have been reported for several other marine ecosystems. Phytoplankton growth seems to be nitrogen limited while the levels of P and Si always remain high. Factor Analysis/Principal Component Analysis (FA/PCA) of the correlation matrix showed that the nitrogen compounds are associated with the main factor accounting for 25.7-26.2% of the total variance for both the sampling periods. During Phase I, the Chrysophyta were the major group, whereas during Phase II the proportion of Chrysophyta in the total community progressively decreased, while the other groups increased.
In photosynthesis, a very small amount of the solar energy absorbed is transformed into chemical energy, while the rest is wasted as heat and fluorescence. This excess energy can be harvested through biophotovoltaic platforms to generate electrical energy. In this study, algal biofilms formed on ITO anodes were investigated for use in the algal biophotovoltaic platforms. Sixteen algal strains, comprising local isolates and two diatoms obtained from the Culture Collection of Marine Phytoplankton (CCMP), USA, were screened and eight were selected based on the growth rate, biochemical composition and photosynthesis performance using suspension cultures. Differences in biofilm formation between the eight algal strains as well as their rapid light curve (RLC) generated using a pulse amplitude modulation (PAM) fluorometer, were examined. The RLC provides detailed information on the saturation characteristics of electron transport and overall photosynthetic performance of the algae. Four algal strains, belonging to the Cyanophyta (Cyanobacteria) Synechococcus elongatus (UMACC 105), Spirulina platensis. (UMACC 159) and the Chlorophyta Chlorella vulgaris (UMACC 051), and Chlorella sp. (UMACC 313) were finally selected for investigation using biophotovoltaic platforms. Based on power output per Chl-a content, the algae can be ranked as follows: Synechococcus elongatus (UMACC 105) (6.38×10(-5) Wm(-2)/µgChl-a)>Chlorella vulgaris UMACC 051 (2.24×10(-5) Wm(-2)/µgChl-a)>Chlorella sp.(UMACC 313) (1.43×10(-5) Wm(-2)/µgChl-a)>Spirulina platensis (UMACC 159) (4.90×10(-6) Wm(-2)/µgChl-a). Our study showed that local algal strains have potential for use in biophotovoltaic platforms due to their high photosynthetic performance, ability to produce biofilm and generation of electrical power.
Climate change has been predicted to influence the marine phytoplankton community and its carbon acquisition strategy. Extracellular carbonic anhydrase (eCA) is a zinc metalloenzyme that catalyses the relatively slow interconversion between HCO3- and CO2. Early results indicated that sub-nanomolar levels of eCA at the sea surface were sufficient to enhance the oceanic uptake rate of CO2 on a global scale by 15%, an addition of 0.37 Pg C year-1. Despite its central role in the marine carbon cycle, only in recent years have new analytical techniques allowed the first quantifications of eCA and its activity in the oceans. This opens up new research areas in the field of marine biogeochemistry and climate change. Light and suitable pH conditions, as well as growth stage, are crucial factors in eCA expression. Previous studies showed that phytoplankton eCA activity and concentrations are affected by environmental stressors such as ocean acidification and UV radiation as well as changing light conditions. For this reason, eCA is suggested as a biochemical indicator in biomonitoring programmes and could be used for future response prediction studies in changing oceans. This review aims to identify the current knowledge and gaps where new research efforts should be focused to better determine the potential feedback of phytoplankton via eCA in the marine carbon cycle in changing oceans.
Studies that associate environmental parameters with aquatic organisms in man-made lakes remain limited by accessibility and interest particularly in many Asian countries. With missed opportunities to monitor environmental transitions at Lake Kenyir, our knowledge of lake transition is restricted to the non-mixing shallow waters only. Triplicate monthly benthic invertebrate samples were collected concurrently with various environmental parameters at three locations (zones A-C) of Kenyir Lake, Malaysia. Our results affirmed that the northeast part of Lake Kenyir is oligotrophic. Abundance of phytoplankton, total suspended solids, phosphate, nitrite and nitrate drive the abundance of various groups of benthic invertebrates. All of these extrinsic variables (except phosphate) negatively influenced the density of Trichoptera and positively influenced (P<0.05) the densities of Polychaeta, Oligochaeta, Bivalvia, Gastropod, Isopoda and Copepod in all zones. Phosphate negatively influenced the density of Trichoptera and positively influenced (P<0.05) the densities of Oligochaeta, Bivalvia and Copepod. Its influences on the Polychaeta, Gastropod and Isopoda densities were zone-specific. Overall, seasons equally influenced the relationships between extrinsic and response variables in all zones. The results of this study are useful to evaluate the lake's environmental quality, in conservation and in similar projects involving environmental handling, monitoring and recovery.
Human emissions of carbon dioxide are causing irreversible changes in our oceans and impacting marine phytoplankton, including a group of small green algae known as picochlorophytes. Picochlorophytes grown in natural phytoplankton communities under future predicted levels of carbon dioxide have been demonstrated to thrive, along with redistribution of the cellular metabolome that enhances growth rate and photosynthesis. Here, using next-generation sequencing technology, we measured levels of transcripts in a picochlorophyte Chlorella, isolated from the sub-Antarctic and acclimated under high and current ambient CO2 levels, to better understand the molecular mechanisms involved with its ability to acclimate to elevated CO2. Compared to other phytoplankton taxa that induce broad transcriptomic responses involving multiple parts of their cellular metabolism, the changes observed in Chlorella focused on activating gene regulation involved in different sets of pathways such as light harvesting complex binding proteins, amino acid synthesis and RNA modification, while carbon metabolism was largely unaffected. Triggering a specific set of genes could be a unique strategy of small green phytoplankton under high CO2 in polar oceans.
Coastal ecosystems are often subjected to anthropogenic disturbances that lead to water quality deterioration and an increase in harmful algal bloom (HAB) events. Using the next-generation molecular tool of 18S rDNA metabarcoding, we examined the community assemblages of HAB species in the Johor Strait, Malaysia between May 2018 and September 2019, covering 19 stations across the strait. The molecular operational taxonomic units (OTUs) of HAB taxa retrieved from the dataset (n = 194) revealed a much higher number of HAB taxa (26 OTUs) than before, with 12 taxa belong to new records in the strait. As revealed in the findings of this study, the diversity and community structure of HAB taxa varied significantly over time and space. The most common and abundant HAB taxa in the strait (frequency of occurrence >70%) comprised Heterosigma akashiwo, Fibrocapsa japonica, Pseudo-nitzschia pungens, Dinophysis spp., Gymnodinium catenatum, Alexandrium leei, and A. tamiyavanichii. Also, our results demonstrated that the HAB community assemblages in the strait were dependent on the interplay of environmental variables that influence by the monsoonal effects. Different HAB taxa, constitute various functional types, occupied and prevailed in different environmental niches across space and time, leading to diverse community assemblages and population density. This study adds to the current understandings of HAB dynamics and provides a robust overview of temporal-spatial changes in HAB community assemblages along the environmental gradients in a tropical eutrophic coastal ecosystem.
Phytoplankton growth (μ) and grazing loss (g) rates were measured monthly by the Landry-Hassett dilution method over a 2-year period at both estuarine (Klang) and coastal water (Port Dickson) systems along the Straits of Malacca. Chlorophyll a (Chl a) concentration ranged from 0.20 to 4.47 μg L(-1) at Klang except on two occasions when Chl a spiked above 10 μg L(-1). In contrast, Chl a concentrations were relatively stable at Port Dickson (0.14 to 2.76 μg L(-1)). From the rate measurements, μ was higher (t = 2.01, df = 43, p 0.80). g ranged from 0.30 to 1.50 and 0.21 to 1.51 day(-1) at Klang and Port Dickson, respectively. In this study, grazing loss was coupled to phytoplankton growth, and the ratio of g/μ or grazing pressure which estimates the proportion of primary production grazed was 50% at Klang and lower than at Port Dickson (68%; t = 2.213, df = 36, p
Hydrocarbon-degrading bacteria, which can be found living with eukaryotic phytoplankton, play a pivotal role in the fate of oil spillage to the marine environment. Considering the susceptibility of calcium carbonate-bearing phytoplankton under future ocean acidification conditions and their oil-degrading communities to oil exposure under such conditions, we investigated the response of non-axenic E. huxleyi to crude oil under ambient versus elevated CO2 concentrations. Under elevated CO2 conditions, exposure to crude oil resulted in the immediate decline of E. huxleyi, with concomitant shifts in the relative abundance of Alphaproteobacteria and Gammaproteobacteria. Survival of E. huxleyi under ambient conditions following oil enrichment was likely facilitated by enrichment of oil-degraders Methylobacterium and Sphingomonas, while the increase in relative abundance of Marinobacter and unclassified Gammaproteobacteria may have increased competitive pressure with E. huxleyi for micronutrient acquisition. Biodegradation of the oil was not affected by elevated CO2 despite a shift in relative abundance of known and putative hydrocarbon degraders. While ocean acidification does not appear to affect microbial degradation of crude oil, elevated mortality responses of E. huxleyi and shifts in the bacterial community illustrates the complexity of microalgal-bacterial interactions and highlights the need to factor these into future ecosystem recovery projections.
In summer 2010, a massive bloom appeared in the middle (16-25°N, 160-200°E) of the North Pacific Subtropical Gyre (NPSG) creating a spectacular oasis in the middle of the largest oceanic desert on Earth. Peaked in June 2010 covering over two million km2 in space, this phytoplankton bloom is the largest ever recorded by ocean color satellites in the NPSG over the period from 1997 to 2013. The initiation and mechanisms sustaining the massive bloom were due to atmospheric and oceanic anomalies. Over the north (25-30°N) of the bloom, strong anticyclonic winds warmed sea surface temperature (SST) via Ekman convergence. Subsequently, anomalous westward ocean currents were generated by SST meridional gradients between 19°N and 25°N, producing strong velocity shear that caused large number of mesoscale (100-km in order) cyclonic eddies in the bloom region. The ratio of cyclonic to anticyclonic eddies of 2.7 in summer 2010 is the highest over the 16-year study period. As a result of the large eddy-number differences, eddy-eddy interactions were strong and induced submesoscale (smaller than 100 km) vertical pumping as observed in the in-situ ocean profiles. The signature of vertical pumping was also presented in the in-situ measurements of chlorophyll and nutrients, which show higher concentrations in 2010 than other years.
Very little work has determined the relative importance of uncontrolled environmental factors for affecting fish biology, and how these might influence gillnet catches. This study addresses this deficit for an important Southeast Asian cyprinid (Barbonymus schwanenfeldii). Fish were caught monthly for 12 months using gillnets of three different mesh sizes, each of which was deployed in duplicate at the surface of one of three randomly selected sites in Lake Kenyir, Malaysia, concurrent with determining various environmental parameters and the abundance of phytoplankton (chlorophyll-a). Results indicated that growth co-efficient of B. schwanenfeldii was positively influenced by dissolved oxygen and negatively influenced by total inorganic nitrogen, whereas an opposite result was observed in case of the hepatosomatic index of fish. Water turbidity was a limiting factor only for small fish (mean total length: 15.74±1.10 cm). B. schwanenfeldii could best be caught during the period of high phytoplankton abundance or at the location of high phytoplankton density in the water. Water temperature negatively influenced the gillnet catches of the fish. The remaining environmental factors such as water depth, pH, and phosphate had a weak and insignificant influence (P >0.05) on the biology and gillnet catches of fish. The observed results can be very useful for the ecological monitoring and conservation plans for this species in relation to climate change. Furthermore, the utility of the similar data for other species would be useful not only for regional but also for international fishery by optimizing catches considering environmental conditions.
In addition to monsoon-driven rainfall, the Maritime Continent (MC) is subject to heavy precipitation caused by the Madden-Julian Oscillation (MJO), a tropical convection-coupled circulation that propagates eastward from the Indian to the Pacific Ocean. This study shows that riverine runoff from MJO-driven rainfall in the western MC significantly enhances phytoplankton biomass not only in the coastal regions but as far as the nutrient-poor Banda Sea, located 1,000 km downstream of the riverine source. We present observational estimates of the chlorophyll-a concentration in the Banda Sea increasing by 20% over the winter average within an MJO life cycle. The enhancement of phytoplankton in the central Banda Sea is attributed to two coinciding MJO-triggered mechanisms: enhanced sediment loading and eastward advection of waters with high sediment and chlorophyll concentrations. Our results highlight an unexpected effect of MJO-driven rainfall on the downstream oceanic region. This finding has significant implications for the marine food chain and biogeochemical processes in the MC, given the increasing deforestation rate and projections that global warming will intensify both the frequency and strength of MJO-driven rainfall in the MC.
The dinoflagellate genus Alexandrium has been well known for causing paralytic shellfish poisoning (PSP) worldwide. Several non-PSP toxin-producing species, however, have shown to exhibit fish-killing toxicity. Here, we report the allelopathic activity of Alexandrium leei from Malaysia to other algal species, and its toxicity to finfish and zooplankton, via laboratory bioassays. Thirteen microalgal species that co-cultured with Al. leei revealed large variability in the allelopathic effects of Al. leei on the test algae, with the growth inhibition rates ranging from 0 to 100%. The negative allelopathic effects of Al. leei on microalgae included loss of flagella and thus the motility, damages of chain structure, deformation in cell morphology, and eventually cell lysis. The finfish experienced 100% mortality within 24 h exposed to the live culture (2000-6710 cells·mL-1), while the rotifer and brine shrimp exhibited 96-100% and 90-100% mortalities within 48 h when exposed to 500-6000 cells·mL-1 of Al. leei. The mortality of the test animals depended on the Al. leei cell density exposed, leading to a linear relationship between mortality and cell density for the finfish, and a logarithmic relationship for the two zooplankters. When exposed to the treatments using Al. leei whole live culture, cell-free culture medium, extract of algal cells in the f/2-Si medium, extract of methanol, and the re-suspended freeze-and-thaw algal cells, the test organisms (Ak. sanguinea and rotifers) all died at the cell density of 8100 cells·mL-1 within 24 h. Toxin analyses by HILIC-ESI-TOF/MS and LC-ESI-MS/MS demonstrated that Al. leei did not produce PSP-toxins and 13-desmethyl spirolide C. Overall, our findings demonstrated potent allelopathy and toxicity of Al. leei, which do not only pose threats to the aquaculture industry, fisheries, and marine ecosystems but may also play a part role in the population dynamics and bloom formation of this species.
Coastal eutrophication is one of the pivotal factors driving occurrence of harmful algal blooms (HABs), whose underlying mechanism remained unclear. To better understand the nutrient regime triggering HABs and their formation process, the phytoplankton composition and its response to varying nitrogen (N) and phosphorus (P), physio-chemical parameters in water and sediment in Johor Strait in March 2019 were analyzed. Surface and sub-surface HABs were observed with the main causative species of Skeletonema, Chaetoceros and Karlodinium. The ecophysiological responses of Skeletonema to the low ambient N/P ratio such as secreting alkaline phosphatase, regulating cell morphology (volume; surface area/volume ratio) might play an important role in dominating the community. Anaerobic sediment iron-bound P release and simultaneous N removal by denitrification and anammox, shaped the stoichiometry of N and P in water column. The decrease of N/P ratio might shift the phytoplankton community into the dominance of HABs causative diatoms and dinoflagellates.
Determination of chlorophyll-a (Chl-a) distribution in the coastal waters is important to understand the coastal environmental conditions. This study was conducted to understand the spatial and temporal distribution of Chl-a along coastal waters of east Peninsular Malaysia and factors influencing its variability using Chl-a data derived from Aqua MODIS satellite (1 km spatial resolution) from January 2006 to December 2012. Chl-a variability was described using empirical orthogonal function (EOF) analysis. In-situ data (temperature, salinity, density and nitrate) and rainfall data from the Department of Meteorology were analyzed using spatial interpolation to determine factors influencing the distribution of Chl-a. The seasonal progressions of Chl-a showed high value during northeast monsoon along the coast. This variability was described by four modes of the EOF analysis. The first mode (72.08% of total variance) indicated seasonal cycle with high variability along the coast. Second mode (17.03% of variance) explained the northeast monsoon with high variability from river mouth to the south. Third mode (2.39% of variance) indicated variability during southwest monsoon along the coast and much higher to the south. Mode 4 (1.93% of variance) explained the inter-monsoon period observed along the northern and southern coastline. Concentration and distribution of Chl-a were related to availability of nutrient influenced by rainfall. The thermohaline front was also observed to play an important role in accumulation of phytoplankton biomass during northeast and southwest monsoon.