Monthly Chaetocerotales diversity and abundance, and its relationship with water physicochemical parameters and phytoplankton diversity in Carey Island mangrove ecosystem, Malaysia

Redzuan NS, Milow P. 2021. Monthly Chaetocerotales diversity and abundance, and its relationship with water physicochemical parameters and phytoplankton diversity in Carey Island mangrove ecosystem, Malaysia. Biodiversitas 22: 2919-2927. Globally, phytoplankton of order Chaetocerotales has been reported to cause monospecific bloom events. The blooms that normally lead to ecosystem instability, also physically responsible for histological and physical damages to fishes. Regarding that order Chaetocerotales often display significant temporal variability, this study aimed to investigate the monthly variability of species composition and cell density of phytoplankton of order Chaetocerotales during high tide period immersion were investigated over a year period. In addition, this present study also aimed to analyze the relationship between Chaetocerotales diversity and abundance with physical and chemical parameters that potentially controlling their temporal variability. Samplings were carried out from April 2009 until March 2010 in the mangrove ecosystem of Carey Island, Selangor, Malaysia. Of 84 phytoplankton taxa recorded, 18 species belonged to order Chaetocerotales, i.e. the genera Bacteriastrum and Chaetoceros. Although initially the sampling was designed to study the overall phytoplankton, the study also aimed at high temporal variability in Chaetocerotaceae cells density has called for this paper to be written. Interestingly, order Chaetocerotales showed to have negative correlation with the total phytoplankton species. Chaetocerotales blooms at the study site were represented by multispecies blooms, with Chaetoceros curvisetus as the highest species in the events. Dissolved oxygen, on the other hand, showed to have negative correlation Chaetocerotales' cells density. All of the species, except the Chaetoceros subtilis and Chaetoceros neglectus displayed significant temporal monthly variability across twelve months of sampling. Nitrate, phosphate and temperature are potentially the parameters that stimulate the growth of the order, consequently causing bloom events.

Resolving cryptic species complexes in marine protists: phylogenetic haplotype networks meet global DNA metabarcoding datasets

Marine protists have traditionally been assumed to be lowly diverse and cosmopolitan. Yet, several recent studies have shown that many protist species actually consist of cryptic complexes of species whose members are often restricted to particular biogeographic regions. Nonetheless, detection of cryptic species is usually hampered by sampling coverage and application of methods (e.g. phylogenetic trees) that are not well suited to identify relatively recent divergence and ongoing gene flow. In this paper, we show how these issues can be overcome by inferring phylogenetic haplotype networks from global metabarcoding datasets. We use the Chaetoceros curvisetus (Bacillariophyta) species complex as study case. Using two complementary metabarcoding datasets (Ocean Sampling Day and Tara Oceans), we equally resolve the cryptic complex in terms of number of inferred species. We detect new hypothetical species in both datasets. Gene flow between most of species is absent, but no barcoding gap exists. Some species have restricted distribution patterns whereas others are widely distributed. Closely related taxa occupy contrasting biogeographic regions, suggesting that geographic and ecological differentiation drive speciation. In conclusion, we show the potential of the analysis of metabarcoding data with evolutionary approaches for systematic and phylogeographic studies of marine protists.

Checklist and estimation of total number of phytoplankton species in Pari, Tidung, and Payung Islands, Indonesia

Rachman A. 2020. Checklist and estimation of total number of phytoplankton species in Pari, Tidung, and Payung Islands, Indonesia. Biodiversitas 21: 2446-2454. A checklist of phytoplankton species from an anthropogenically pressured ecosystem has become a necessity to study the marine ecosystem changes and to detect the presence of introduced species in the area. This study aimed to list and describe the phytoplankton community in the Tidung, Pari, and Payung Islands and to estimate the total number of phytoplankton species in those islands. Sampling was conducted in May 2019 in 10 sites, consisted of 5 sites around Pari Island, 1 site next to Payung Island, and 4 sites around Tidung Island. As many as 150 species of phytoplankton, consisted of 109 species of diatoms, 38 species of dinoflagellates, 3 species of cyanobacteria, were recorded in this study. However, up to 47 phytoplankton species were estimated to be missing from the current sampling effort. Three diatom species, Chaetoceros curvisetus, Chaetoceros distans, and Chaetoceros affinis were the most abundant and most common species in the studied areas. Dinoflagellates were found in low density and have limited distribution compared to diatoms. Tripos trichoceros, Tripos fusus, and Tripos macroceros were the three most common dinoflagellates in the studied islands. Several notable harmful species, such as Pseudo-nitzschia spp., Alexandrium sp., Tripos furca, Cochlodinium sp., Dinophysis miles, Prorocentrum lima, and Noctiluca scintillans, were present albeit with low cell density. However, concern on future blooms of those harmful species in the greater water regions (i.e. Seribu Island or Jakarta Bay) should be noted, as it might cause environmental damages, including a shift in species dominance and disappearance of some native phytoplankton species from the ecosystem in the future.

Species composition and distribution of some phytoplankton in Myeik Archipelago, Southern Myanmar

The species composition and distribution of some phytoplankton, the primary producer in the food chain of fish and shrimp, was studied from water samples that collected at surface layer of 20 stations in the Myeik Archipelago, Southern Myanmar from 2010 to 2018. A total of 144 species comprised of 123 species of diatoms and 21 species of dinoflagellate were recorded in the Myeik Archipelago. Among them, the most number 93 species of phytoplankton was recorded in Done Pale Aw Station however the lowest 26 species found in Le' Al' Thal Tan Station. The common representative species were ten diatoms species such as Chaetoceros curvisetus, Ditylum sol, Lauderia annulata, Nitzschia longissima, Odotella sinensis, Pleurosigma normanii, Pseudo Nitzschia seriata, Rhizosolenia setigera, Thalassionema nitzschioides and T. frauenfeldii and then one of dinoflagellate, Ceratium furca. Moreover, the percentage of diatom (87%) was higher than the dinoflagellate (13%) during the study period. The temperature 25-30°C and salinity 4-34‰ was found in the Myeik Archipelago during the study period.

Actividad antibacteriana de diatomeas marinas aisladas de Acapulco, Guerrero, México

Las diatomeas marinas sintetizan y secretan una gran variedad de metabolitos secundarios con aplicaciones potenciales en la industria farmacéutica, sin embargo su estudio aún es limitado. Por tal motivo, el objetivo de este trabajo fue aislar y cultivar las especies Chaetoceros curvisetus, Asterionella japonica, y Biddulphia mobiliensis de la Bahía Santa Lucía del Puerto de Acapulco, Guerrero, México, así como determinar la actividad antibacteriana frente a bacterias de importancia clínica y analizar el perfil fitoquímico cualitativo de sus extractos totales. La biomasa fue de 219,62 ± 0,99; 151,12 ± 1,41 y 109,04 ± 1,48 mg para C. curvisetus, A. japonica, y B. mobiliensis, respectivamente. Extractos con hexano, diclorometano, y acetona fueron obtenidos de cada especie, y el perfil fitoquímico cualitativo indicó que estas diatomeas marinas fueron ricas en aceites esenciales, alcaloides, y terpenos. Se observó que los extractos de C. curvisetus poseen alta actividad con Concentraciones Mínimas Inhibitorias (CMI) entre 0,5 y 2 mg mL-1 para bacterias tipo ATCC y de 8 y 16 mg mL-1 para cepas de E. coli productoras de BLEE.

Role of <i>Calanus sinicus</i> (Copepoda, Calanoida) on dimethylsulfide production in Jiaozhou Bay

The role of copepod Calanus sinicus on the production of dimethylsulfide (DMS)/dimethylsulfoniopropionate (DMSP) in Jiaozhou Bay was evaluated in field and laboratory experiments. Samples at 10 sites in the bay were collected monthly from June 2010 to May 2011 (except for March 2011), and zooplankton species composition was analyzed. The relationship between copepod abundance and DMS or DMSP concentration was investigated. Effects of C. sinicus grazing on DMS/DMSP production at different conditions (i.e., algal diets, food concentrations, and salinities) were assessed in the laboratory. Data from the field experiment showed that C. sinicus was the predominant copepod in Jiaozhou Bay (up to 123 individuals m−3 in May 2011) and has no apparent effect on DMS/DMSP production. In the laboratory experiment, compared with Gymnodinium sp. or Emiliania huxleyi, C. sinicus feeding on Isochrysis galbana and Chaetoceros curvisetus exhibited increased DMS concentration, whereas high salinity inhibited DMS production. This study indicated that DMSP was transferred from phytoplankton to copepod body, fecal pellet, and seawater through copepod grazing. Our results provided important information to understand the biogeochemical cycle of DMSP in Jiaozhou Bay.

Diatoms in an extreme euxinic environment (Rogoznica Lake, eastern Adriatic coast)

The Rogoznica Lake marine system is a small, karstic, naturally eutrophic and euxinic marine environment. Abundance and temporal distribution of phytoplankton was investigated in relation to environmental conditions in the period from 1998 to 2013. The 36 determined diatoms contributed 90% of the total phytoplankton abundance. The diatom composition is characterized by low species diversity and high single species abundance (up to 107 cells L-1). There were, on average, 2.6 diatom species per sample (maximum 14 diatom species per sample) reflecting extreme environmental conditions. Dominant diatoms Thalassionema nitzschioides, Cyclotella choctawhatcheeana, Dactyliosolen fragilissimus and Chaetoceros curvisetus occurred repeatedly and were alternately dominant in the lake during the whole research period. Some diatoms were dominant only in limited period, like Cyclotella choctawhatcheeana (evident since 2001), and Pseudo-nitzschia spp. (evident in the period 2002 to 2009). It appears that the interplay of environmental conditions such as variability in thermohaline and redox conditions, nutrient and reduced sulphur concentration influence the phytoplankton development and abundance in the lake.