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Impact of microplastic exposure on the health of tropical seagrass (Enhalus acoroides) seedlings
Abstract
The early stages of seagrass life are marked by the development of seagrass seedlings. Enhalus acoroides is a
persistent seagrass species with a high prevalence in tropical waters. The decline in water quality caused by
human activities, such as microplastic contamination, is suspected to affect the growth and development of
seagrass seedlings. This study examines the impact of microplastic exposure on the growth, chlorophyll content,
and anatomical structure of Enhalus acoroides seedlings. This experimental research included four treatments:
Treatment A (no microplastics), Treatment B (0.5 g/L microplastics), Treatment C (1.0 g/L microplastics), and
Treatment D (1.5 g/L microplastics). The results show that increasing microplastic concentrations disrupt
photosynthesis in seagrass seedlings, indicated by a decrease in chlorophyll content, which leads to reduced
growth and lower survival rates in seedlings (Treatment D). Based on this study, it is suggested that higher
microplastic exposure may prevent seedlings from developing into mature seagrass individuals.
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Since the emergence of microplastics, the scientific community has been extremely alarmed regarding their potential risks for and threats to both the environment and human lives. MPs are traced in freshwater and marine environments, day-to-day-life ecosystems, and the bodies of animals and humans. Due to their usage advancements, MPs have become directly or indirectly an integral part of personal care, cosmetics, and cleaning products and appeared as a domestic cause of environmental pollution. Over the years, researchers have ascertained the harmful effects of MPs on the environment. In this regard, the monitoring and assessment of MPs in PCCPs necessitates considerable attention. The worldwide ban legislation on plastic μBs used in cosmetic products has driven researchers to investigate sustainable and eco-friendly alternatives. This review paper summarizes the potential threats of MPs used in cosmetics and the utilization of potential alternatives.
he high level of public plastic consumption can trigger the increase of plastic and waste in marine areas. Plastic floats in the ocean will then be degraded into smaller sizes (<5 mm), namely microplastics. Microplastic can be dangerous to marine environments, especially to natural resources, including sediment and marine biotas., where microplastics are easily eaten by diverse marine biota. Bintan Island is a conservation area with abundant seagrass and associated biota resources, especially Strombus sp. This study examines microplastic contamination in sediment and Strombus sp. on Bintan Island, Indonesia. Samples (Strombus sp.) were collected from a 100 x 20 meter seagrass area, while sediment samples were taken in a 1 m x 1 m quadrant. The sediment was dried, and the biota was dissected to see the presence of microplastics. All microplastics collected from both samples were identified in shape and colour. The results showed that microplastics had been found in sediment and Strombus sp. Based on the characteristics of microplastics, the highest abundance of colour found was white, while the highest abundance of types found was a fragment
Increasing sea surface temperatures as an effect of global warming can affect the survival of marine organism, among these marine organisms is seagrass. Temperature is one factor that can determine seagrass's physiological response in maintaining its life, including in the early stages of life in seagrass seedlings. This research aims to study the effect of temperature on the physiological response of Enhalus acoroides seedlings such as growth rate, leaf tissue anatomy, and chlorophyll content. The method used was an experiment in the laboratory. The seagrass seedlings were grown in an aquarium with three sea water temperature treatments (28°C, 31°C and 35°C) for 8 weeks of maintenance. The choice of sea water temperature treatment of 28°C (A) as a control is the optimal temperature range for seagrass, the treatment temperature of 31°C (B) refers to previous study, i.e. the temperature in the area of origin of the seagrass meadow, and the treatment temperature of 35°C (C) is considered as an estimate of temperature under the scenario of. The growth rate and the average leaf length were more optimal with a high chlorophyll content found at a temperature treatment of 28°C. The highest anatomical size of leaf tissue in the upper and lower epidermis was observed at 31°C, while the most extensive mesophyll tissue was observed at 35°C. In this study, temperature significantly affected the growth rate, average leaf length, anatomical structure of mesophyll tissue, and chlorophyll content of the Enhalus acoroides seedlings.
Seagrasses provide crucial ecosystem services of relevance for the marine environment. However, anthropogenic activities are causing global seagrass decline. Increasing microplastic (MP) concentrations have been recognized as a novel threat to many marine organisms, but their effects on marine plants remain underexplored. Here, we investigate the effects of microplastic (polyethylene (PE) and polypropylene (PP)) exposure on the photosynthesis and respiration of the seagrass Zostera marina L. and its associated epiphytes. Measurements were conducted on seagrass leaves with and without epiphyte cover, as well as on epiphytes scraped off the leaf surface. Net gas exchange and pH drift measurements were used to determine rates of photosynthesis and respiration, as well as the ability of leaves and epiphytes to utilize bicarbonate. In addition, variable chlorophyll fluorescence imaging was employed to quantify the photosynthetic capacity of seagrass leaves. Our results show a limited effect of short-term (14 days) microplastic exposure on seagrass leaves and their associated epiphytes, although the photosynthetic activity and respiration rates were gradually reduced for bare seagrass leaves with increasing microplastic concentrations (25-1000 mg MP L⁻¹). A >50% reduction in dark respiration of bare leaves was found at the highest MP exposure, while respiration rates of leaves with epiphytes and separated epiphytes were reduced by maximally ~45 and 30% upon MP exposure, respectively. Short-term microplastic exposure did not alter i) the ability to utilize bicarbonate, ii) the maximum quantum yield of PSII ( F V / F M ), nor iii) the light utilization efficiency of Z. marina leaves and associated epiphytes. The compensation irradiance decreased for all investigated specimens, and seagrass leaves (with and without epiphytes) were able to retain a positive net oxygen balance throughout all treatments. We speculate that the observed decrease in photosynthetic activity and respiration was caused by leachates from microplastics. Our findings thus indicate that seagrass Z. marina largely possess resilience toward microplastic pollution at its current level.
In many terrestrial seeds, photosynthetic activity supplies O2 to the developing plant embryo to sustain aerobic metabolism and enhance biosynthetic activity. However, whether seagrass seeds possess similar photosynthetic capacity to alleviate intra‐seed hypoxic stress conditions is unknown.
We used a novel combination of microscale variable chlorophyll fluorescence imaging, a custom‐made O2 optode microrespirometry system and planar optode O2 imaging, to determine the O2 microenvironment and photosynthetic activity in developing seeds and seedlings of seagrass (Zostera marina).
Developing, sheath‐covered seeds exhibited high O2 concentrations in the photosynthetic active seed sheath and low O2 concentrations in the centre of the seed at the position of the embryo. In light, photosynthesis in the seed sheath increased O2 availability in central parts of the seed enabling enhanced respiratory energy generation for biosynthetic activity. Early‐stage seedlings also displayed photosynthetic capacity in hypocotyl and cotyledonary tissues, which may be beneficial for seedling establishment.
Sheath O2 production is important for alleviating intra‐seed hypoxic stress, which might increase endosperm storage activity, improving the conditions for successful seed maturation and germination.
Microplastics are small plastic particles that come from the degradation of plastics, ubiquitous in nature and therefore affect both wildlife and humans. They have been detected in many marine species, but also in drinking water and in numerous foods, such as salt, honey and marine organisms. Exposure to microplastics can also occur through inhaled air. Data from animal studies have shown that once absorbed, plastic micro-and nanoparticles can distribute to the liver, spleen, heart, lungs, thymus, reproductive organs, kidneys and even the brain (crosses the blood-brain barrier). In addition, microplastics are transport operators of persistent organic pollutants or heavy metals from invertebrate organisms to other higher trophic levels. After ingestion, the additives and monomers in their composition can interfere with important biological processes in the human body and can cause disruption of the endocrine, immune system; can have a negative impact on mobility, reproduction and development; and can cause carcinogenesis. The pandemic caused by COVID-19 has affected not only human health and national economies but also the environment, due to the large volume of waste in the form of discarded personal protective equipment. The remarkable increase in global use of face masks, which mainly contain polypropylene, and poor waste management have led to worsening microplastic pollution, and the long-term consequences can be extremely devastating if urgent action is not taken.
Seagrass transplantation in the large-scale requires a large number of seagrass individu from donor ecosystem. This may give negative impact as damage and reducing the number of seagrass in donor ecosystem. One of methods to overcome this case is by developing transplants using seagrass nut as source for seed. Substrate is one of factors that influence the growth of seagrass. The aim of this study was to compare the effect of differences in substrate composition on morphologi and growth of Enhalus acoroides seeds. Observations were carried out by treatment using mud, sand and mixed substrates sand with mud. The survival rate of Enhalus acoroides seeds was quite high of 100% but it had a lower value of 93.30% on sand substrate. The longest leaf is on the mud substrate with a length of 5.9 cm, the leaf width has the same size in each substrate with a value of 0.4 cm, the highest number of leaves were found in the sand and mixture substrate with 5 strands, the longest root size was in the mixed substrate with a length of 5 cm. The growth of Enhalus acoroides seagrass seeds did not show any significant difference. The highest growth was found in the mud substrate with a value of 0.10 cm/day. Keywords: Enhalus acoroides, seagrass,seed, substrate, transplantation
Nugraha AH, Tasabaramo IA, Hernawan UE, Rahmawati S, Putra RD, Darus RF. 2021. Diversity, coverage, distribution and ecosystem services of seagrass in three small islands of northern Papua, Indonesia: Liki Island, Meossu Island and Befondi Island. Biodiversitas 22: 5544-5549. Papua waters are one of the hot spot areas with high marine biodiversity in the world. Yet, the less accessible location and varying geographical conditions become the significant constraints of biodiversity study in this region, resulting in limited information about the diversity of marine resources, including the seagrass ecosystem. This research aims to investigate the diversity, coverage and distribution of seagrass in three small islands in the northern waters of Papua, namely Liki Island, Befondi Island, and Meossu Island, as well as to study the ecosystem services provided by the seagrass. This research is part of the Nusa Manggala Expedition, which was carried out in November 2018, consisted of seven observation stations. Data collection was conducted using the transect line method combined with plot quadrat. Information regarding seagrass ecosystem services was gathered through observation and direct interviews to the community. The results showed that there were seven species of seagrass in the studied sites, namely Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Halodule pinifolia, Halophila ovalis, Thalassia hemprichii, and Syringodium isoetifolium. Liki Island had the highest seagrass cover value of 82.24%, followed by Meossu Island and Befondi Island with seagrass cover of 63.23% and 31.25%, respectively. There were 13 seagrass ecosystem services identified in this research. The people of Liki Island and Meossu Island get the benefits of the existence of the seagrass ecosystem. The direct benefits are the presence of seagrass is associated with biota commonly used as food sources such as Siganus sp and sea cucumbers. There are efforts made by the community to maintain the sustainability of the seagrass ecosystem, which is known as sasi.
Plastic waste increasingly accumulates in the marine environment, but data on the distribution and quantification of riverine sources required for development of effective mitigation are limited. Our model approach includes geographically distributed data on plastic waste, land use, wind, precipitation, and rivers and calculates the probability for plastic waste to reach a river and subsequently the ocean. This probabilistic approach highlights regions that are likely to emit plastic into the ocean. We calibrated our model using recent field observations and show that emissions are distributed over more rivers than previously thought by up to two orders of magnitude. We estimate that more than 1000 rivers account for 80% of global annual emissions, which range between 0.8 million and 2.7 million metric tons per year, with small urban rivers among the most polluting. These high-resolution data allow for the focused development of mitigation strategies and technologies to reduce riverine plastic emissions.
The pollution due to marine debris is a serious environmental threat in many parts of the world. The abundance of marine debris, composition and its distribution over the seafloor along north-east coast of Arabian coast was studied through trawl based swept method. Experimental fishing was conducted fortnightly using shrimp bottom trawl and collected debris was categorized as per standard protocols. A total of 1077 pieces of debris (11.7 kg dry weight) were collected from 25 hauls. The average number and weight of debris were 943 items/ km2 and 10.2 kg/ km2 respectively. The estimated total marine debris along this coast was 379 tonnes (dry weight). Plastic-based debris contributed maximum (87.1%) to the total debris collected in numbers and among this, plastic bags and food wrappers were dominant. Debris produced by shoreline/recreational activities comprised the major source of debris (88.6%) along this coast. This study provides the evidence that the effective use of available fishing trawlers and co-management practices (“Make fishers friend”) can help to remove the seabed debris. The base data generated through this study would facilitate region-based effective control and management of plastic debris pollution.
Rosalina D, Herawati EY, Musa M, Sofarini D, Risjani Y. 2019. Short communication: Anatomical changes in the roots, rhizomes, and leaves of seagrass (Cymodocea serrulata) in response to lead. Biodiversitas 20: 2583-2588. Runoff of heavy metals as a result of urban and industrial development is a potential threat for seagrass populations in the coast. The objectives of this study were to study the anatomical changes in the tissues of roots, rhizomes, and leaves of seagrass Cymodocea serrulata in response to treatment with different concentrations of lead (Pb) for different time durations. This experiment used heavy metal Pb from a solution of Pb (NO3)2-with a concentration of 0 ppm, 5 ppm, 10 ppm, and 15 ppm and the treatment period extended up to 4 weeks with 3 replications. Analysis of changes in anatomical features showed that exodermis and endodermis cells in the roots thickened as lead concentration increased. The air spaces in the root cortex and rhizome also widened. Thickening of cell walls occurred in the epidermis and endodermis of rhizome. Likewise, in the leaves, thickening occurred in the upper and lower cuticle and also the upper and lower epidermis. In general, changes in anatomical features of root, rhizome, and leaves were observed in response to increasing lead concentrations. The results showed that C. serrulata developed some level of tolerance to heavy metals, especially lead.
Seagrasses are unique angiosperms that carry out growth and reproduction submerged in seawater. They occur in at least three families of the Alismatales. All have chloroplasts mainly in the cells of the epidermis. Living in seawater, the supply of inorganic carbon (Ci) to the chloroplasts is diffusion limited, especially under unstirred conditions. Therefore, the supply of CO2 and bicarbonate across the diffusive boundary layer on the outer side of the epidermis is often a limiting factor. Here we discuss the evidence for mechanisms that enhance the uptake of Ci into the epidermal cells. Since bicarbonate is plentiful in seawater, a bicarbonate pump might be expected; however, the evidence for such a pump is not strongly supported. There is evidence for a carbonic anhydrase outside the outer plasmalemma. This, together with evidence for an outward proton pump, suggests the possibility that local acidification leads to enhanced concentrations of CO2 adjacent to the outer tangential epidermal walls, which enhances the uptake of CO2, and this could be followed by a carbon-concentrating mechanism (CCM) in the cytoplasm and/or chloroplasts. The lines of evidence for such an epidermal CCM are discussed, including evidence for special ‘transfer cells’ in some but not all seagrass leaves in the tangential inner walls of the epidermal cells. It is concluded that seagrasses have a CCM but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven.
Incineration of plastic waste in an open field is a major source of air pollution. Most of the times, the Municipal Solid Waste containing about 12% of plastics is burnt, releasing toxic gases like Dioxins, Furans, Mercury and Polychlorinated Biphenyls into the atmosphere. Further, burning of Poly Vinyl Chloride liberates hazardous halogens and pollutes air, the impact of which is climate change. The toxic substances thus released are posing a threat to vegetation, human and animal health and environment as a whole. Polystyrene is harmful to Central Nervous System. The hazardous brominated compounds act as carcinogens and mutagens. Dioxins settle on the crops and in our waterways where they eventually enter into our food and hence the body system. These Dioxins are the lethal persistent organic pollutants (POPs) and its worst component, 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), commonly known as agentorange is a toxic compound which causes cancer and neurological damage, disrupts reproductive thyroid and respiratory systems. Thus, burning of plastic wastes increase the risk of heart disease, aggravates respiratory ailments such as asthma and emphysema and cause rashes, nausea or headaches, and damages the nervous system. Hence, a sustainable step towards tomorrow's cleaner and healthier environment needs immediate attention of the environmentalists and scientists. This review presents the hazards of incineration; open burning of plastics and effects of plastic in water and also a possibility of working out strategies to develop alternate procedures of plastic waste management.
Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world’s oceans from 24 expeditions (2007–2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N5680) and visual survey transects of large plastic debris (N5891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic ,4.75 mm and meso- and macroplastic .4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove ,4.75 mm plastic particles from the ocean surface.
This review of 68 studies compares the methodologies used for the identification and quantification of microplastics from the marine environment. Three main sampling strategies were identified: selective, volume-reduced, and bulk sampling. Most sediment samples came from sandy beaches at the high tide line, and most seawater samples were taken at the sea surface using neuston nets. Four steps were distinguished during sample processing: density separation, filtration, sieving, and visual sorting of microplastics. Visual sorting was one of the most commonly used methods for the identification of microplastics (using type, shape, degradation stage, and color as criteria). Chemical and physical characteristics (e.g., specific density) were also used. The most reliable method to identify the chemical composition of microplastics is by infrared spectroscopy. Most studies reported that plastic fragments were polyethylene and polypropylene polymers. Units commonly used for abundance estimates are "items per m(2)" for sediment and sea surface studies and "items per m(3)" for water column studies. Mesh size of sieves and filters used during sampling or sample processing influence abundance estimates. Most studies reported two main size ranges of microplastics: (i) 500 μm-5 mm, which are retained by a 500 μm sieve/net, and (ii) 1-500 μm, or fractions thereof that are retained on filters. We recommend that future programs of monitoring continue to distinguish these size fractions, but we suggest standardized sampling procedures which allow the spatiotemporal comparison of microplastic abundance across marine environments.
Since the mass production of plastics began in the 1940s, microplastic contamination of the marine environment has been a growing problem. Here, a review of the literature has been conducted with the following objectives: (1) to summarise the properties, nomenclature and sources of microplastics; (2) to discuss the routes by which microplastics enter the marine environment; (3) to evaluate the methods by which microplastics are detected in the marine environment; (4) to assess spatial and temporal trends of microplastic abundance; and (5) to discuss the environmental impact of microplastics. Microplastics are both abundant and widespread within the marine environment, found in their highest concentrations along coastlines and within mid-ocean gyres. Ingestion of microplastics has been demonstrated in a range of marine organisms, a process which may facilitate the transfer of chemical additives or hydrophobic waterborne pollutants to biota. We conclude by highlighting key future research areas for scientists and policymakers.
The management and conservation of the world's oceans require synthesis of spatial data on the distribution and intensity of human activities and the overlap of their impacts on marine ecosystems. We developed an ecosystem-specific, multiscale spatial model to synthesize 17 global data sets of anthropogenic drivers of ecological change for 20 marine ecosystems. Our analysis indicates that no area is unaffected by human influence and that a large fraction (41%) is strongly affected by multiple drivers. However, large areas of relatively little human impact remain, particularly near the poles. The analytical process and resulting maps provide flexible tools for regional and global efforts to allocate conservation resources; to implement ecosystem-based management; and to inform marine spatial planning, education, and basic research.
eagrass ecosystems have an essential function as a feeding, spawning and nursery areas for various marine biota, etc. There are threats to the sustainability of seagrass ecosystems' biodiversity, one of which is the dumping of garbage into the sea, which causes damage to coastal ecosystems. This study aimed to determine the species and cover of seagrass ecosystems and the type and density of marine debris in seagrass ecosystems in the waters of small islands of Tanjungpinang City. There are three stations: Dompak Island, Penyengat Island, and Los Island. This research was conducted in May-June 2023. Seagrass cover data was collected using the line transect method with a quadrat transect of 50 cm x 50 cm to observe the species and cover. Data collection on marine debris in the seagrass ecosystem was taken on transects with an area of 100 m x 100 m. Marine debris obtained is then grouped by type to calculate density and weight. The types of seagrasses found include Enhalus acoroides, Thalassia hemprichii, Cymodocea serrulata, Cymodocea rotundata, Halodule uninervis, Halodule pinifolia, Halophila ovalis, and Syringodium isoetifolium. The highest total seagrass cover is found on Los Island, with a value of 25.81% classified as poor with a sparse cover category. The types of marine debris found are plastic, glass, rubber, wood, and its derivatives. According to the number of pieces, the highest density of marine debris is plastic waste, resulting in 0.0079 items/m2, and the weight density is 0.0528 grams/m2 found at Los Island.
Despite being a leading pollutant in the ocean, there are limited studies about plastic litter in seagrasses, and none has been documented in the Philippines. This study determined the abundance and composition of macroplastics in seagrass beds of Iligan City, Philippines. Plastics were collected from transect lines laid in seagrass beds of four sites (Dalipuga, Hinaplanon, Tominobo and Buru-un), and three locations (landward, midward, seaward) in each site, periodically within 42 days. A total of 921 macroplastic items were collected in all sampling sites, of which 308 were from Buru-un, 271 from Tominobo, 240 from Dalipuga, and 102 from Hinaplanon. Landward areas have a significantly higher density than either midward or seaward. The first sampling was higher than the succeeding sampling period. Food packaging, plastic bags, and fragments predominated the litter in seagrass. This study is the first to document the presence of macroplastics in seagrass beds in the Philippines.
Understanding the environmental fate of microplastics is essential for their risk assessment. It is essential to differentiate size classes and degradation states. Still, insights into fragmentation and degradation mechanisms of primary and secondary microplastics into micro- and nanoplastic fragments and other degradation products are limited. Here, we present an adapted NanoRelease protocol for a UV-dose-dependent assessment and size-selective quantification of the release of micro- and nanoplastic fragments down to 10 nm and demonstrate its applicability for polyamide and thermoplastic polyurethanes. The tested cryo-milled polymers do not originate from actual consumer products but are handled in industry and are therefore representative of polydisperse microplastics occurring in the environment. The protocol is suitable for various types of microplastic polymers, and the measured rates can serve to parameterize mechanistic fragmentation models. We also found that primary microplastics matched the same ranking of weathering stability as their corresponding macroplastics and that dissolved organics constitute a major rate of microplastic mass loss. The results imply that previously formed micro- and nanoplastic fragments can further degrade into water-soluble organics with measurable rates that enable modeling approaches for all environmental compartments accessible to UV light.
Microplastics (MPs) and nanoplastics (NPs) are ubiquitous in natural habitats and the risks their presence poses to marine environments and organisms are of increasing concern. There is evidence that seagrass meadows are particularly prone to accumulate plastic debris, including polystyrene particles, but the impacts of this pollutant on seagrass performance are currently unknown. This is a relevant knowledge gap as seagrasses provide multiple ecosystem services and are declining globally due to anthropogenic impact and climate-change-related stressors.
Here, we explored the potential effects of a 12 day-exposure of seagrasses to one concentration (68 μg/L) of polystyrene MPs and NPs on the growth, oxidative status, and photosynthetic efficiency of plants using the foundation species Cymodocea nodosa as a model. Among plant organs, adventitious roots were particularly affected by MPs and NPs showing complete degeneration. The number of leaves per shoot was lower in MPs- and NPs-treated plants compared to control plants, and leaf loss exceeded new leaf production in MPs-treated plants. MPs also reduced photochemical efficiency and increased pigment content compared to control plants. Shoots of NPs-treated plants showed a greater oxidative damage and phenol content than those of control plants and MPs-treated plants. Biochemical data about oxidative stress markers were consistent with histochemical results. The effects of MPs on C. nodosa could be related to their adhesion to plant surface while those of NPs to entering tissues.
Our study provides the first experimental evidence of the potential harmful effects of MPs/NPs on seagrass development. It also suggests that the exposure of seagrasses to MPs/NPs in natural environments could have negative consequences on the functioning of seagrass ecosystems. This stresses the importance of implementing cleaning programs to remove all plastics already present in marine habitats as well as of undertaking specific actions to prevent the introduction of these pollutants within seagrass meadows.
This review aims to explore the effects of microplastics and their corresponding additives on the physiological performances of marine bivalves together with their related genes. We identified gaps based on studies that were conducted on other organisms, and we conducted a comparative study on similar and relevant aspects for exploring future potential areas of study and interest. Microplastics are widely dispersed in all forms of media (solid, liquid, and gas). Exposure to an organism (including humans) is inevitable. However, impacts depend on the concentration of exposure, location of a biomarker being observed, and treatment involved. Different shapes, colors, and polymer types are reported and the transfer of microplastics along the food chain are recorded. The impacts of microplastics intensify when coupled with other chemicals or additives (referred to as xenobiotics) in a treated group. Thus, the degree of inhibition or enhancement of a physiological response magnifies when a coexposure of microplastic and a xenobiotic occurs. Microplastics have been observed to reduce immune system functionality by reducing hemocytes count, distorting oxidative system, respiration, and increasing energy consumption in bivalves due to physiological modulations that result from ingestion of microplastics or their additives. We found knowledge gaps and suggested future research directions to fully understand the impact of microplastics and their additives on marine bivalves.
Microplastics have been discovered ubiquitously in marine environments. While their accumulation is noted in seagrass ecosystems, little attention has yet been given to microplastic impacts on seagrass plants and their associated epiphytic and sediment communities. We initiate this discussion by synthesizing the potential impacts microplastics have on relevant seagrass plant, epiphyte, and sediment processes and functions. We suggest that microplastics may harm epiphytes and seagrasses via impalement and light/gas blockage, and increase local concentrations of toxins, causing a disruption in metabolic processes. Further, microplastics may alter nutrient cycling by inhibiting dinitrogen fixation by diazotrophs, preventing microbial processes, and reducing root nutrient uptake. They may also harm seagrass sediment communities via sediment characteristic alteration and organism complications associated with ingestion. All impacts will be exacerbated by the high trapping efficiency of seagrasses. As microplastics become a permanent and increasing member of seagrass ecosystems it will be pertinent to direct future research towards understanding the extent microplastics impact seagrass ecosystems.
The accelerated discard and mismanagement of human-made products are resulting in the continued input of litter into the oceans. Models and field observations show how floating litter can accumulate in remote areas throughout the global ocean, but far less is known about the non-floating litter fraction. Seagrass meadows play an important role in the sediment and natural-debris dynamics, and likely also in the storage and processing of non-floating litter. In this work, non-floating litter was studied across six Posidonia oceanica meadows. Litter accumulated mainly around the landside edge of the meadow. The outer margin of the edge predominantly trapped macro-litter, whilst microplastics accumulated mainly along the inner margin. On average, macro-litter concentrations increased 3-fold after heavy rainfall. Retention of non-floating litter by coastal meadows facilitates the recurrent landward-seaward conveyance of the easily-transportable litter (mainly plastic items) and its fragmentation before it is buried or transferred to deeper areas.
Seagrasses have the ability to contribute towards climate change mitigation, through large organic carbon (Corg) sinks within their ecosystems. Although the importance of blue carbon within these ecosystems has been addressed in some countries of Southeast Asia, the regional and national inventories with the application of nature-based solutions are lacking. In this study, we aim to estimate national coastal blue carbon stocks in the seagrass ecosystems in the countries of Southeast Asia including the Andaman and Nicobar Islands of India. This study further assesses the potential of conservation and restoration practices and highlights the seagrass meadows as nature-based solution for climate change mitigation. The average value of the total carbon storage within seagrass meadows of this region is 121.95 ± 76.11 Mg ha−1 (average ± SD) and the total Corg stock of the seagrass meadows of this region was 429.11 ± 111.88 Tg, with the highest Corg stock in the Philippines (78%). The seagrass meadows of this region have the capacity to accumulate 5.85–6.80 Tg C year−1, which accounts for 21.42–24.96 million USD. The potential of the seagrass meadows to the offset current CO2 emissions varies across the region, with the highest contribution to offset is in the seagrass meadows of the Philippines (11.71%). Current national policies and commitments of nationally determined contributions do not include blue carbon ecosystems as climate mitigation measures, even though these ecosystems can contribute up to 7.03% of the countries' reduction goal of CO2 emissions by 2030. The results of this study highlight and promote the potential of the southeast Asian seagrass meadows to national and international agencies as a practical scheme for nature-based solutions for climate change mitigation.
Enhalus acoroides, the dominant species in tropical seagrass meadows, is experiencing declines worldwide for complicated reasons and the restoration of these meadows is extremely urgent. Nursery stock grown from the initial seedlings could be used to enhance success of E. acoroides meadow restoration. In this study, the effects of different cultivation methods on the seedling development and longer-term cultivation of E. acoroides were compared using various artificial culture substrates (culturing with sea mud substrate, agar substrate, without a matrix, and using a submerged foam substrate). Results suggested that none of the seedlings showed any sign of root gemination when cultured with sea mud substrate. Though the seedlings cultured with an agar substrate grew faster than those cultured with sea mud, those seedlings could not be cultured further as the agar substrate softened and became rotten after 3 weeks. The initial seedlings cultured in matrix-free seawater germinated with normal leaf growth but no roots developed. In contrast, the initial seedlings planted in holes of a submerged foam substrate grew successfully, developing into healthy seedlings with green leaves and long roots. These seedlings could be cultured for up to 23 weeks. Based on these results, a new, low-cost and labor-efficient method for E. acoroides seedling development was established, which might have a great application potential for efficient E. acoroides seagrass meadows restoration.
Plastic pollution is one of the major challenges in the Anthropocene. Upon reaching the marine environment, plastic debris is subject to anthropogenic and environmental conditions that result in novel items that vary in composition, physical and chemical characteristics. Here, we reviewed and discussed the potential fate and threat to the environment of four recently described plastic formations: Plastiglomerates, pyroplastics, plasticrusts, and anthropoquinas. The threats identified were mostly related to the release of toxic chemicals and plastic ingestion. Transportation of alien invasive species or microbial pathogens and fragmentation of larger plastics into microplastics (<5 mm), potentially reaching marine trophic webs, are suspected as potential impacts based on the characteristics of these plastic formations. Some plastic forms may persist in the environment and voyage across the ocean, while others are denser and less likely to enter the plastic cycle or interact with biota. In the latter case, plastics are expected to become buried in the sediment and incorporate into the geological record. It is necessary to establish sampling protocols or standards that are specific to each plastic formation and start reporting the occurrence of these new plastic categories as such to avoid underestimating plastic pollution in marine environments. It is suggested that monitoring plans include these categories and identify potential sources. Further research must focus on investigating whether the suspected impacts are a matter of concern. In this sense, we have suggested research questions to address the knowledge gaps and have a better understanding of the impacts and distribution of the new plastic forms.
The impact of low-density polyethylene (LDPE) microplastics (<100 μm; P100-A P100-B, P100-C, 100–200 μm; P200, 200–500 μm; P500) on Acropora formosa was investigated. This study investigated the bleaching and necrosis extent of A. formosa caused by LDPE contamination via laboratory assay. The staghorn coral ingested the microplastics, resulting in bleaching and necrosis that concomitantly occurred with the release of zooxanthellae. P100-A experimentation was the worst case, showing bleaching by day 2 (10.8 ± 2.2%) and continued bleaching to 93.6% ± 2.0 by day 14 followed by 5.9 ± 2.5% necrosis. The overall results confirmed that the LDPE concentration impacts coral health. We highlighted that microplastics have been ingested and partially egested. Their presence showed either a direct or indirect impact on coral polyps via direct interaction or through photosynthesis perturbation due to microplastics that cover the coral surface.
Indonesia's marine ecosystems form a fundamental part of the world's natural heritage, representing a global maxima of marine biodiversity and supporting the world's second largest production of seafood. Seagrasses are a key part of that support. In the absence of empirical data we present evidence from expert opinions as to the state of Indonesia's seagrass ecosystems, their support for ecosystem services, with a focus on fisheries, and the damaging activities that threaten their existence. We further draw on expert opinion to elicit potential solutions to prevent further loss. Seagrasses and the ecosystem services they support across the Indonesian archipelago are in a critical state of decline. Declining seagrass health is the result of shifting environmental conditions due largely to coastal development, land reclamation, and deforestation, as well as seaweed farming, overfishing and garbage dumping. In particular, we also describe the declining state of the fisheries resources that seagrass meadows support. The perilous state of Indonesia's seagrasses will compromise their resilience to climate change and result in a loss of their high ecosystem service value. Community supported management initiatives provide one mechanism for seagrass protection. Exemplars highlight the need for increased local level autonomy for the management of marine resources, opening up opportunities for incentive type conservation schemes.
Microplastics in seagrass ecosystems: A review of fate and impacts
- Tang