Genetic diversity and population structure of terapon jarbua (Forskål, 1775) (teleostei, terapontidae) in malaysian waters

A background study is important for the conservation and stock management of a species. Terapon jarbua is a coastal Indo-Pacific species, sourced for human consumption. This study examined 134 samples from the central west and east coasts of Peninsular (West) Malaysia and East Malaysia. A 1446-bp concatenated dataset of mtDNA COI and Cyt b sequences was used in this study and 83 haplotypes were identified, of which 79 are unique haplotypes and four are shared haplotypes. Populations of T. jarbua in Malaysia are genetically heterogenous as shown by the high level of haplotype diversity ranging from 0.9167–0.9952, low nucleotide diversity ranging from 0.0288–0.3434, and high FST values (within population genetic variation). Population genetic structuring is not distinct as shown by the shared haplotypes between geographic populations and mixtures of haplotypes from different populations within the same genetic cluster. The gene flow patterns and population structuring observed among these regions are likely attributed to geographical distance, past historical events, allopatric speciation, dispersal ability and water currents. For instance, the mixture of haplotypes revealed an extraordinary migration ability of T. jarbua (>1200 km) via ancient river connectivity. The negative overall value of the neutrality test and a non-significant mismatch distribution are consistent with demographic expansion(s) in the past. The median-joining network concurred with the maximum likelihood haplotype tree with three major clades resolved. The scarcity of information on this species is an obstacle for future management and conservation purposes. Hence, this study aims to contribute information on the population structure, genetic diversity, and historical demography of T. jarbua in Malaysia

Taxonomy and phylogeny of crustose brown algae (Phaeophyceae) from Malaysia and Lombok Island, Indonesia / Poong Sze Wan

Studies on crustose brown algae are relatively few despite a long history of studies conducted since the 1800s, with temperate species forming the bulk of these studies. There is a need for more focus on crustose brown algae particularly in the tropics as they are generally different from those in the temperate regions. These algae received little attention due to their simple appearance (brownish-black spots on rocks) and lack of apparent economic value despite some being the dominant flora of certain habitats. Taxonomic confusion arising from morphological simplicity largely dependent on the reproductive structures and overlap in morpho-anatomical features among species necessitates the use of molecular approach. This study aims to enhance our understanding of the taxonomy and phylogeny of these understudied algae in Malaysia and Lombok Island by combining morpho-anatomical observations and molecular sequence data [plastid rubisco large subunit (rbcL) and partial mitochondrial cytochrome c oxidase subunit 1 (cox1-5’) gene sequences]. Key diagnostic morphological characters for identification include relative thickness of the crust, assembly of erect filaments, number of chloroplast(s) and most importantly the organisation of reproductive structures. Results indicated that the common crustose brown algae in Malaysia and Lombok Island are species of Mesospora, Diplura and Neoralfsia expansa. Seven species of Mesospora were identified in the present study of which three were formally described (M. schmidtii, M. negrosensis and M. elongata) and four are putative new species to be described (Mesospora sp. C, Mesospora sp. D, Mesospora sp. 1 and Mesospora sp. 2). Partial output from this study leads to the recent description of Mesospora elongata Poong, Lim & Phang from Japan and Lombok Island and a new record of M. negrosensis for Malaysia. The presence of M. elongata in Malaysia is reported here for the first time since the initial publication of this taxon. iv Mesospora sp. C and M. schmidtii were reported earlier in Malaysia. This study also marks the first report of Mesospora sp. D (previously reported in Japan) and four putative species of Diplura for Malaysia and Indonesia. The taxon provisionally named “Mesospora” sp. 3 and the closely related Mesospora sp. G are likely members of a new genus. Other crustose brown algae examined in this study include a Ralfsia-like species and two yet-to-be identified taxa. The crustose brown algae are polyphyletic and occur in widely divergent clades among the brown algae with the majority placed in Ralfsiales while the rest are closely associated with other phaeophyceaen orders such as Sphacelariales and Ishigeales. Circumscription of Ralfsiales comprises the Ralfsiaceae, Neoralfsiaceae, Mesosporaceae and a possible new family to accommodate “Mesospora” sp. 3. Establishment of a new family for members of the genus Diplura is underway pending the collection of the generitype, Diplura simulans. Molecular analyses incorporating Hapalospongidion saxigenum indicate that Mesospora, currently synonymised with Hapalospongidion should be retained as a separate genus. The rbcL marker performed better in the elucidation of phylogeny at higher classification levels, whereas cox1-5’ is more suited as a barcoding marker for species level identification of the crustose brown algae

Seawater carbonate chemistry and photosynthetic pigments and photophysiology of polar microalga Chlorella sp.

Ocean acidification, due to increased levels of anthropogenic carbon dioxide, is known to affect the physiology and growth of marine phytoplankton, especially in polar regions. However, the effect of acidification or carbonation on cellular metabolism in polar marine phytoplankton still remains an open question. There is some evidence that small chlorophytes may benefit more than other taxa of phytoplankton. To understand further how green polar picoplankton could acclimate to high oceanic CO2, studies were conducted on an Antarctic Chlorella sp. Chlorella sp. maintained its growth rate (∼0.180 /day), photosynthetic quantum yield (Fv/Fm = ∼0.69) and chlorophyll a (0.145 fg/cell) and carotenoid (0.06 fg/cell) contents under high CO2, while maximum rates of electron transport decreased and non-photochemical quenching increased under elevated CO2. GCMS-based metabolomic analysis reveal that this polar Chlorella strain modulated the levels of metabolites associated with energy, amino acid, fatty acid and carbohydrate production, which could favour its survival in an increasingly acidified ocean

A metabolomic approach to investigate effects of ocean acidification on a polar microalga Chlorella sp.

Ocean acidification, due to increased levels of anthropogenic carbon dioxide, is known to affect the physiology and growth of marine phytoplankton, especially in polar regions. However, the effect of acidification or carbonation on cellular metabolism in polar marine phytoplankton still remains an open question. There is some evidence that small chlorophytes may benefit more than other taxa of phytoplankton. To understand further how green polar picoplankton could acclimate to high oceanic CO2, studies were conducted on an Antarctic Chlorella sp. Chlorella sp. maintained its growth rate (∼0.180 d-1), photosynthetic quantum yield (Fv/Fm = ∼0.69) and chlorophyll a (0.145 fg cell-1) and carotenoid (0.06 fg cell-1) contents under high CO2, while maximum rates of electron transport decreased and non-photochemical quenching increased under elevated CO2. GCMS-based metabolomic analysis reveal that this polar Chlorella strain modulated the levels of metabolites associated with energy, amino acid, fatty acid and carbohydrate production, which could favour its survival in an increasingly acidified ocean. © 2019 Elsevier B.V

Marine Autotroph-Herbivore Synergies: Unravelling the Roles of Macroalgae in Marine Ecosystem Dynamics

Species invasion is a leading threat to marine ecosystems worldwide, being deemed as one of the ultimate jeopardies for biodiversity along with climate change. Tackling the emerging biodiversity threat to maintain the ecological balance of the largest biome in the world has now become a pivotal part of the Sustainable Development Goals (SDGs). Marine herbivores are often considered as biological agents that control the spread of invasive species, and their effectiveness depends largely on factors that influence their feeding preferences, including the specific attributes of their food–the autotrophs. While the marine autotroph-herbivore interactions have been substantially discussed globally, many studies have reported contradictory findings on the effects of nutritional attributes and novelty of autotrophs on herbivore feeding behaviour. In view of the scattered literature on the mechanistic basis of autotroph-herbivore interactions, we generate a comprehensive review to furnish insights into critical knowledge gaps about the synergies based largely on the characteristics of macroalgae; an important group of photosynthetic organisms in the marine biome that interact strongly with generalist herbivores. We also discuss the key defence strategies of these macroalgae against the herbivores, highlighting their unique attributes and plausible roles in keeping the marine ecosystems intact. Overall, the feeding behaviour of herbivores can be affected by the nutritional attributes, morphology, and novelty of the autotrophs. We recommend that future research should carefully consider different factors that can potentially affect the dynamics of the marine autotroph-herbivore interactions to resolve the inconsistent results of specific attributes and novelty of the organisms involved

Gene expression profile of marine Chlorella strains from different latitudes: stress and recovery under elevated temperatures

Global warming, as a consequence of climate change, poses a critical threat to marine life, including algae. Studies on algal response at the molecular level to temperature stress have been significantly improved by advances in omics technologies. Algae are known to employ various strategies in response to heat stress. For example, algae regulate starch synthesis to provide energy for the cell or rebuild the damaged subunits of photosystems to regain photosynthetic activity. The aim of the present study is to examine the expression of selected photosynthesis-related genes of marine Chlorella originating from different latitudes, in response to heat stress and during the recovery period. In this study, marine Chlorella strains from the Antarctic, temperate region, and the tropics were grown at their ambient and stress-inducing temperatures. The maximum quantum efficiency (F v /F m ) photosynthetic parameter was used to assess their stress levels. When subjected to heat stress, the F v /F m began to decline and when it reached ~ 0.2, the cultures were transferred to their respective ambient temperature for recovery. Total RNA was isolated from these cultures at F v /F m ~ 0.4, 0.2, and when it regained 0.4 during recovery. The expression of four genes including psbA, psaB, psbC, and rbcL was analyzed using RT-PCR. The housekeeping gene, histone subunit three (H3) was used for data normalization. Studying the genes involved in the adaptation mechanisms would enhance our knowledge on algal adaptation pathways and pave the way for genetic engineers to develop more tolerant strains

Interactive effects of temperature and copper toxicity on photosynthetic efficiency and metabolic plasticity in Scenedesmus quadricauda (Chlorophyceae)

Warming and copper (Cu) toxicity are two key abiotic stressors that strongly affect cell growth, photosynthetic rate, and metabolism in microalgae. In this study, a freshwater chlorophyte, Scenedesmus quadricauda, was exposed to various concentrations of copper sulfate (300, 600, and 1000 μM nominal concentrations of CuSO4·5H2O) at 25 and 35 °C. The changes in cell density, photosynthetic parameters, in vivo absorption spectra, reactive oxygen species (ROS) levels, and metabolic profile were analyzed. The effects of copper toxicity on the physiology and biochemistry of microalgae were highly dependent on water temperature. The interactive effects of both stressors induced significant impact on the photosynthetic parameters such as maximum quantum yield (Fv/Fm), saturation irradiance (Ek), and non-photochemical quenching (NPQ). Temperature induced significant impact on cell density, Ek and NPQ, while the Cu toxicity significantly affected the Fv/Fm and NPQ. Changes in the in vivo absorption spectra and high levels of reactive oxygen species (ROS) were observed across different treatments. Overall, S. quadricauda adapted to the two abiotic stresses via NPQ and metabolic restructuring. Key metabolites including glycine, proline, hexadecanoic acid, propanoic acid, octadecanoic acid, galactose, lactose, and sucrose were involved in the microalgal response. The synergistic effects of temperature and Cu stresses on microalgae might affect community tolerance and species distribution in the long run

Physiological and metabolic responses of Scenedesmus quadricauda (Chlorophyceae) to nickel toxicity and warming

An ecologically important tropical freshwater microalga, Scenedesmus quadricauda, was exposed to Ni toxicity under two temperature regimes, 25 and 35 °C to investigate the interactive effects of warming and different Ni concentrations (0.1, 1.0 and 10.0 ppm). The stress responses were assessed from the growth, photosynthesis, reactive oxygen species (ROS) generation and metabolomics aspects to understand the effects at both the physiological and biochemical levels. The results showed that the cell densities of the cultures were higher at 35 °C compared to 25 °C, but decreased with increasing Ni concentrations at 35 °C. In terms of photosynthetic efficiency, the maximum quantum yield of photosystem II (Fv/Fm) of S. quadricauda remained consistent across different conditions. Nickel concentration at 10.0 ppm affected the maximum rate of relative electron transport (rETRm) and saturation irradiance for electron transport (Ek) in photosynthesis. At 25 °C, the increase of non-photochemical quenching (NPQ) values in cells exposed to 10.0 ppm Ni might indicate the onset of thermal dissipation process as a self-protection mechanism against Ni toxicity. The combination of warming and Ni toxicity induced a strong oxidative stress response in the cells. The ROS level increased significantly by 40% after exposure to 10.0 ppm of Ni at 35 °C. The amount of Ni accumulated in the biomass was higher at 25 °C compared to 35 °C. Based on the metabolic profile, temperature contributed the most significant differentiation among the samples compared to Ni treatment and the interaction between the two factors. Amino acids, sugars and organic acids were significantly regulated by the combined factors to restore homeostasis. The most affected pathways include sulphur, amino acids, and nitrogen metabolisms. Overall, the results suggest that the inhibitory effect of Ni was lower at 35 °C compared to 25 °C probably due to lower metal uptake and primary metabolism restructuring. The ability of S. quadricauda to accumulate substantial amount of Ni and thrive at 35 °C suggests the potential use of this strain for phycoremediation and outdoor wastewater treatment

Growth and photosynthesis of Chlorella strains from polar, temperate and tropical freshwater environments under temperature stress

Elevated temperatures as a consequence of global warming have significant impacts on the adaptation and survival of microalgae which are important primary producers in many ecosystems. The impact of temperature on the photosynthesis of microalgae is of great interest as the primary production of algal biomass is strongly dependent on the photosynthetic rates in a dynamic environment. Here, we examine the effects of elevated temperature on Chlorella strains originating from different latitudes, namely Antarctic, Arctic, temperate and tropical regions. Chlorophyll fluorescence was used to assess the photosynthetic responses of the microalgae. Rapid light curves (RLCs) and maximum quantum yield (F v / F m ) were recorded. The results showed that Chlorella originating from different latitudes portrayed different growth trends and photosynthetic performance. The Chlorella genus is eurythermal, with a broad temperature tolerance range, but with strain-specific characteristics. However, there was a large overlap between the tolerance range of the four strains due to their “eurythermal adaptivity”. Changes in the photosynthetic parameters indicated temperature stress. The ability of the four strains to reactivate photosynthesis after inhibition of photosynthesis under high temperatures was also studied. The Chlorella strains were shown to recover in terms of photosynthesis and growth (measured as Chl a) when they were returned to their ambient temperatures. Polar strains showed faster recovery in their optimal temperature compared to that under the ambient temperature from which they were isolated

Ice-Ice disease: An environmentally and microbiologically driven syndrome in tropical seaweed aquaculture

Seaweeds account for nearly 30% of global aquaculture production by volume, and their cultivation provides important opportunities for employment and wealth generation, particularly in rural coastal communities. Eucheumatoids (Kappaphycus and Eucheuma spp.) are tropical red algae commercially cultivated as raw material for production of carrageenans, particularly in South-East Asia and the Western Indian Ocean region. Diseases and pests are major limiting factors in eucheumatoid production, particularly a condition known as ‘ice-ice’ disease (IID). IID is characterized by bleaching of the thallus followed by the disintegration of affected tissues, leading to a loss of biomass and reduced carrageenan yield. IID has been associated with unfavourable changes in environmental conditions, particularly an increase in sea water temperature and a decrease in salinity, and infection by opportunistic or pathogenic bacteria. However, given that no single or combined causal agents have been definitely identified, IID may be considered a complex pathobiotic syndrome in which multiple factors contribute to the development of disease signs. Here, we review current knowledge of the abiotic and biotic factors associated with the development of IID, and the strategies employed to mitigate economic losses resulting from disease outbreaks. We discuss syndromic diseases in other marine holobionts, particularly other red algae and corals, in relation to their similarity to IID, and suggest the application of comprehensive and complementary methodologies, including high-throughput sequencing and high-quality microscopy, for enhancing our understanding of the pathological and microbiological processes associated with IID signs.All authors were supported by funding from UKRI for the GlobalSeaweedSTAR project (BB/P027806/1)