A Bayesian approach to modeling phytoplankton population dynamics from size distribution time series

The rates of cell growth, division, and carbon loss of microbial populations are key parameters for understanding how organisms interact with their environment and how they contribute to the carbon cycle. However, the invasive nature of current analytical methods has hindered efforts to reliably quantify these parameters. In recent years, size-structured matrix population models (MPMs) have gained popularity for estimating division rates of microbial populations by mechanistically describing changes in microbial cell size distributions over time. Motivated by the mechanistic structure of these models, we employ a Bayesian approach to extend size-structured MPMs to capture additional biological processes describing the dynamics of a marine phytoplankton population over the day-night cycle. Our Bayesian framework is able to take prior scientific knowledge into account and generate biologically interpretable results. Using data from an exponentially growing laboratory culture of the cyanobacterium Prochlorococcus, we isolate respiratory and exudative carbon losses as critical parameters for the modeling of their population dynamics. The results suggest that this modeling framework can provide deeper insights into microbial population dynamics provided by size distribution time-series data.

Response of Marine Plankton Communities in Ponds to the Presence of Vertical Structures

The effects of bottom vertical structures like AquaMats® in enhancing plankton productivity was evaluated. One experimental earthen pond of 500 m2 was provided with AquaMats® increasing the surface substrate area 12 times and water quality, phytoplankton and zooplankton populations developed during almost 100 days was compared with a pond without AquaMats®. Their presence favored the development of Dinoflagellates (Miozoa, Dinophyceae), mostly Gymnodiniales, which may be of some concern since some species of this group have been associated with toxic algal blooms while in the ponds without AquaMats® Diatoms (Bacillariophyta) predominate. In both ponds plankton production was very much sculptured by external nutrients added to the systems. The balance between different nutrients is extremely important to regulate the phytoplankton populations with Diatoms blooming at silicate concentrations higher than 2 μM and below this level and at low nitrate and high ammonium being more appropriate for Dinoflagellates. The linkage between phytoplankton and zooplankton population in ponds is strong with zooplankton exerting control over the phytoplankton population and vice-versa. The use of vertical substrates enhances plankton productivity by increasing the substrate area for periphyton fixation. The main zooplankton taxonomic groups associated with the presence of AquaMats® were Calanoid and Harpacticoid copepodites and nauplii, veligers of gastropods and trochophore of polychaets, larval stages of organisms that except for calanoid copepods are benthic and correspond to the meroplanktonic phase in the life cycle of those organisms.

Algorithm for monitoring the plankton population dynamics based on satellite sensing data

The scientific work describes the algorithms for processing the multispectral water coastal imagery from satellite sensing data with the aim of identifying the phytoplankton population of a spotted structure: determining the contour, distributing color gradation and as a result - determining the concentration of phytoplankton distribution inside the zones and mass centers. Such characteristics let determine the speed of changing contours spots and their concentration, the mass center shift as a consequence of the water masses movement and the processes of phytoplankton growing and dying. All these may be done on the base of the processed image series of the same water area over different time (different dates). The combination of LBP and neural network methods are observed as algorithms for image processing and the results of computer experiments are presented.

Analisis Nitrat dan Fosfat Terhadap Sebaran Fitoplankton Sebagai Bioindikator Kesuburan Perairan Muara Sungai Bodri

Nitrat dan fosfat adalah unsur nutrien yang menjadi pembatas kelimpahan fitoplankton. Kandungan nitrat dan fosfat di perairan muara akan dipengaruhi oleh faktor biologi, fisika dan kimia perairan, yang menyebabkan timbulnya suatu persebaran. Hal tersebut menjadi permasalahan di Muara Sungai Bodri, Kendal. Tujuan dari penelitian ini adalah untuk mengkaji kandungan nitrat dan fosfat beserta pola persebarannya, serta keterkaitannya dengan struktur populasi fitoplankton sebagai bioindikator kesuburan perairan di Perairan Muara Sungai Bodri, Kabupaten Kendal. Penelitian dilaksanakan berdasarkan metoda observasi dengan pendekatan spatio-temporal. Sejumlah 9 stasiun penelitian dan 3 kali waktu sampling yaitu 30 Juni, 1 September dan 27 Oktober 2018. Kandungan nitrat dan fosfat serta kelimpahan fitoplankton ditetapkan sebagai variabel terikat. Sedangkan parameter fisika dan kimia perairan seperti suhu, salinitas, derajat keasaman (pH), oksigen terlarut, kecerahan dan arus ditetapkan sebagai variabel kontrol. Hasil penelitian menunjukan bahwa kandungan nitrat berkisar 0,49-0,9 mg/l serta kandungan fosfat berkisar 0,01-0,29 mg/l yang menunjukkan bahwa perairan Muara Sungai Bodri, Kabupaten Kendal dalam kondisi subur/eutrofik. Kelimpahan fitoplankton menunjukkan nilai kisaran diantara 2.356 sampai dengan 162.626 sel/l, yang tersusun oleh 5 kelas dan 45 jenis/species dengan pola persebaran berbentuk konvergen yang bertumpu pada stasiun 3 dan 5. Perairan Muara Sungai Bodri, Kabupaten Kendal menunjukkan tingkat kesuburan yang tinggi atau eutrofik. Nitrate and Phosphate are the nutrient element which influence as limiting factor to the phytoplankton population. Nitrate and Phosphate in the water were influence by physical and chemical factors, and will affect to the distribution. The distribution of nitrate and phosphate will affect the distribution of phytoplankton population. The purpose of the research is to analyze the distribution of phytoplankton population due to the influence of nitrate and phosphate contents at Bodri Estuary, Kendal. The research was apllied based on the spatio-temporel approach. There are 9 stations and triple sampling of 30 June, 1st Septembre and 27 Octobre, 2018. The nitrate and phosphate contents and phytoplankton abundance was set as dependent variables. The parameters temperature, salinity, pH, Dissolved Oxygen, transparency and current were used as variable control. The research result show the nitrate content range between 0,49-0,9 mgr./l and the phosphate content range between 0,01-0,29 mgr./l, which indicate that the Bodri Estuary, Kendal is eutrophic. The distribution of nitrate and phosphate contens show a model of convergen on west area of sampling and tend to along the coastline in the east part. The phytoplankton abundance show a range of 2.356 - 162.626 cell /l, which composed of 5 Class and 45 species.

Hydrocarbon-Degrading Bacteria Found Tightly Associated with the 50–70 μm Cell-Size Population of Eukaryotic Phytoplankton in Surface Waters of a Northeast Atlantic Region

The surface of marine eukaryotic phytoplankton can harbour communities of hydrocarbon-degrading bacteria; however, this algal–bacterial association has, hitherto, been only examined with non-axenic laboratory cultures of micro-algae. In this study, we isolated an operationally-defined community of phytoplankton, of cell size 50–70 μm, from a natural community in sea surface waters of a subarctic region in the northeast Atlantic. Using MiSeq 16S rRNA sequencing, we identified several recognized (Alcanivorax, Marinobacter, Oleispira, Porticoccus, Thalassospira) and putative hydrocarbon degraders (Colwelliaceae, Vibrionaceae) tightly associated with the phytoplankton population. We combined fluorescence in situ hybridisation with flow-cytometry (FISH-Flow) to examine the association of Marinobacter with this natural eukaryotic phytoplankton population. About 1.5% of the phytoplankton population contained tightly associated Marinobacter. The remaining Marinobacter population were loosely associated with either eukaryotic phytoplankton cells or non-chlorophyll particulate material. This work is the first to show the presence of obligate, generalist and putative hydrocarbonoclastic bacteria associated with natural populations of eukaryotic phytoplankton directly from sea surface water samples. It also highlights the suitability of FISH-Flow for future studies to examine the spatial and temporal structure and dynamics of these and other algal–bacterial associations in natural seawater samples.