The persistence of plastics and its effects in different environments where they accumulate, particularly in coastal areas, is of serious concern. These plastics exhibit signs of degradation, ...possibly mediated by microorganisms. In this study, we investigated the potential of sediment microbial communities from Manila Bay, Philippines, which has a severe plastics problem, to degrade low-density polyethylene (LDPE). Plastics in selected sites were quantified and sediment samples from sites with the lowest and highest plastic accumulation were collected. These sediments were then introduced and incubated with LDPE in vitro for a period of 91 days. Fourier transform infrared spectroscopy detected the appearance of carbonyl and vinyl products on the plastic surface, indicating structural surface modifications attributed to polymer degradation. Communities attached to the plastics were profiled using high-throughput sequencing of the V4-V5 region of the 16S rRNA gene. Members of the phylum Proteobacteria dominated the plastic surface throughout the experiment. Several bacterial taxa associated with hydrocarbon degradation were also enriched, with some taxa positively correlating with the biodegradation indices, suggesting potential active roles in the partial biodegradation of plastics. Other taxa were also present, which might be consuming by-products or providing nourishment for other groups, indicating synergy in utilizing the plastic as the main carbon source and creation of a microenvironment within the plastics biofilm. This study showed that sediment microbes from Manila Bay may have naturally occurring microbial groups potentially capable of partially degrading plastics, supporting previous studies that the biodegradation potential for plastics is ubiquitously present in marine microbial assemblages.
Plastics released in the environment become suitable matrices for microbial attachment and colonization. Plastics-associated microbial communities interact with each other and are metabolically ...distinct from the surrounding environment. However, pioneer colonizing species and their interaction with the plastic during initial colonization are less described. Marine sediment bacteria from sites in Manila Bay were isolated via a double selective enrichment method using sterilized low-density polyethylene (LDPE) sheets as the sole carbon source. Ten isolates were identified to belong to the genera Halomonas, Bacillus, Alteromonas, Photobacterium, and Aliishimia based on 16S rRNA gene phylogeny, and majority of the taxa found exhibit a surface-associated lifestyle. Isolates were then tested for their ability to colonize polyethylene (PE) through co-incubation with LDPE sheets for 60 days. Growth of colonies in crevices, formation of cell-shaped pits, and increased roughness of the surface indicate physical deterioration. Fourier-transform infrared (FT-IR) spectroscopy revealed significant changes in the functional groups and bond indices on LDPE sheets separately co-incubated with the isolates, demonstrating that different species potentially target different substrates of the photo-oxidized polymer backbone. Understanding the activity of primo-colonizing bacteria on the plastic surface can provide insights on the possible mechanisms used to make plastic more bioavailable for other species, and their implications on the fate of plastics in the marine environment.
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•Sediment bacteria isolated from Manila Bay were able to utilize LDPE as the sole carbon source.•Bacterial clusters modified different moieties in the polymer backbone.•Attachment and proliferation of bacterial cells on the plastic surface were observed.•Surface deterioration of the LDPE film was observed as shown by roughness, pits, and crevices.
Studies consistently ranked the Philippines as one of the top contributors of plastic wastes leaking into the ocean. However, most of these were based on probabilities and estimates due to lack of ...comprehensive ground-truth data, resulting also in the limited understanding of the contributing factors and drivers of local pollution. This makes it challenging to develop science-driven and locally-contextualized policies and interventions to mitigate the problem. Here, 56 sites from different coastal habitats in the western Philippine archipelago were surveyed for macroplastics standing stock, representing geographic regions with varying demography and economic activities. Clustering of sites revealed three potential influencing factors to plastic accumulation: population density, wind and oceanic transport, and habitat type. Notably, the amount and types of dominant plastics per geographic region varied significantly. Single-use plastics (food packaging and sachets) were the most abundant in sites adjacent to densely populated and highly urbanized areas (Manila Bay and eastern Palawan), while fishing-related materials dominated in less populated and fishing-dominated communities (western Palawan and Bolinao), suggesting the local industries significantly contributing to the mismanaged plastics in the surveyed sites. Meanwhile, isolated areas such as islands were characterized by the abundance of buoyant materials (drinking bottles and hygiene product containers), emphasizing the role of oceanic transport and strong connectivity in the oceans. Exposure assessment also identified single-use and fishing-related plastics to be of “high exposure (Type 4)” due to their high abundance and high occurrence. These increase their chances of encountering and interacting with organisms and habitats, thus, resulting into more potential harm. This study is the first comprehensive work done in western Philippines, and results will help contextualize local pollution, facilitating more effective management and policymaking.
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•Plastics pollution was evident in all sites surveyed in western Philippines.•Population, ocean current, and habitat type influence plastic accumulation.•Food and beverage packaging, fishing gears contributed the most to plastic wastes.•Single-use plastics have "high exposure" risks based on abundance and occurrence.•Mangroves can effectively trap plastics, making them the most exposed to its risks.
Introduction
Microplastic pollution has become a global issue, eliciting attention not just from the scientific community but also both from the public and governmental bodies. Drawing data-driven ...policies and interventions, however, remain difficult due to the severely lacking baseline information from different environments such as beaches. One of the challenges in doing baseline studies is the lack of harmonized methodologies that will allow for comparison of results, integration of data, and its effective translation to evidence-based policies. Emphasis on quality control measures among baselining efforts through the proper implementation of experimental controls is also lacking.
Methodology
To address these gaps, we compared methodologies for preparing the sediment matrix for experimental controls, as well as evaluated protocols for extracting microplastics from tropical beach sediments. Beach sediments were collected, dried, sieved, and spiked with known amounts of microplastics of different polymer types. The removal and extraction efficiencies of the protocols being compared were evaluated.
Results and discussion
Our results showed that subjecting beach sediments to a furnace at 550° C for 4 hours is the most efficient way to remove plastic contamination, implying its applicability for preparing experimental controls. Meanwhile, a modified version of Masura et al. (2015), one of the widely cited methodologies for microplastics extraction, exhibited the highest mean extraction efficiency (99.05 ± 0.82%) among the protocols being compared. Results of this work will be useful in identifying methods that can be adopted and utilized for research and baselining efforts not just in the Philippines but also in Southeast Asia. This will also be helpful in the harmonization of methods, data reporting, and even skills as implemented through the regional and national action plans to address marine plastic pollution.
Many aspects of the biology and ecology of the toxic dinoflagellate Pyrodinium bahamense var. compressum are still poorly understood. In this brief note, we present identification of its associated ...intracellular bacteria or endosymbionts via PCR cloning and 16s rRNA gene sequencing and their localization by confocal microscopy, a first for Pyrodinium. The most frequently observed species in the endosymbiotic microflora were from Roseobacter clade (Alphaproteobacteria, 68 %) and Gilvibacter sediminis (Flavobacteriaceae, 20 %). Roseobacter lineage, the most abundant taxa in this study, is known to be involved in dimethylsulfoniopropionate metabolism which is highly produced in dinoflagellates—a possible strong factor shaping the structure of the associated bacterial community.
Associated and algicidal bacteria play roles in the succession and decline of phytoplankton blooms, including those of harmful algal bloom (HAB)-forming species. Limited studies on HAB-associated ...bacterial ecology have resulted in our incomplete understanding of HABs dynamics. Diverse phytoplankton-bacterial interactions have also led to studies on their potential as biocontrol tools for HABs mitigation. Here, we tested 48 cultivable pelagic bacteria from three HAB-affected areas in the Philippines (Bolinao, Sorsogon, and Matarinao) against non-axenic cultures of the toxic, thecate dinoflagellate
Pyrodinium bahamense
. Co-incubation with live cultures of these isolates exhibited varying levels of algicidal activities suggesting that it may not be a phylogenetically conserved property. Furthermore, majority of the isolates elicited activity against the thecate test species
P. bahamense
, which was not present in the area where the bacteria were isolated, implying non-specificity of action. Exposure to bacterial cells resulted in
Pyrodinium
pellicle cyst formation. Despite this, however, cell lysis and decline in total cell abundance were still observed, indicating strong algicidal potency of the isolates. In depth understanding of the interplay between environmental factors and algicidal bacteria-microalgal interactions may provide significant insights on the management of HABs.
Tracks, trails, burrows, faecal castings and other sedimentary structures made by organisms on the deep-seafloor, known as “Lebensspuren”, form a natural and significant component of the ...microtopography at the sediment-water interface. These structures are often more conspicuous than the errant organisms responsible for them, particularly at hadal depths (>6000 m). Recent explorations of the deepest places in the oceans have revealed the occurrence of long, often parallel tracks running in unnaturally straight lines along the trench floors, erasing lebensspuren. During a crewed submersible dive to 10,000 m deep in the Philippine Trench (west Pacific Ocean), the source of these features was confirmed to be the result of plastic bags drifting in the near-bottom currents. During the 90 min transect of the trench floor, nine individual bags were observed compared to only one benthic holothurian. Assuming the bags are drifting at similar speeds to the current, these tracks, documented here for the first time, that we have coined “müllspuren” are forming up to 12 times faster than hadal holothurians create lebensspuren. The area affected is also much larger as the tracks laid down by plastic bags often consist of multiple, parallel gouges with smoothed intermediate sediment. The ecological effects of particle perturbation and the erasing of lebensspuren is unknown but is becoming ubiquitous at the deepest points in our oceans.
•Long parallel tracks were observed on hadal trench seafloors.•These tracks erased lebensspuren.•The cause of tracks was observed to be from drifting plastic bags.•We coined the term “müllspuren” (bag traces).•Müllspuren may be modifying sediment faster than benthic fauna.
Epiphytic microalgae can significantly affect the host seaweed either by complementing, or competing for, resources. Here, epiphytic diatom and dinoflagellate species assemblages on the macroalgae ...Acanthophora spicifera, Hypnea pannosa and Gracilaria salicornia collected during the north-east (February), inter- (April) and south-west (June) monsoons in 2015 along the coast of Lucero, Pangasinan, North-western Philippines were examined and characterized. Results showed that diatom-dinoflagellate assemblages strongly clustered by season rather than by geographic location. Within season, a minor clustering by macroalgal forms, rather than host species identity, was also observed, which could be associated with the differences in the complexity and texture of the upright and prostrate seaweeds. Examination of the 'thallisphere' using confocal laser scanning microscopy further revealed the close proximity of some of the 'resident' epiphytic species to the cortical cells of the host, causing deformities and implying more complex interactions. Our results suggest that epiphytic community assemblages were influenced by both the environmental conditions associated with seasonal variation and the microhabitats in the surface of the different algal forms.
Pellicle or temporary cysts of Pyrodinium bahamense var. compressum (Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and ...understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl) a and no detectable chl c. The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observed in vitro , such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts of P. bahamense var . compressum.
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