Seagrass Species Research Articles

Thermo-priming triggers species-specific physiological and transcriptome responses in Mediterranean seagrasses

Heat-priming improves plants' tolerance to a recurring heat stress event. The underlying molecular mechanisms of heat-priming are largely unknown in seagrasses. Here, ad hoc mesocosm experiments were conducted with two Mediterranean seagrass species, Posidonia oceanica and Cymodocea nodosa. Plants were first exposed to heat-priming, followed by a heat-triggering event. A comprehensive assessment of plant stress response across different levels of biological organization was performed at the end of the triggering event. Morphological and physiological results showed an improved response of heat-primed P. oceanica plants while in C. nodosa both heat- and non-primed plants enhanced their growth rates at the end of the triggering event. As resulting from whole transcriptome sequencing, molecular functions related to several cellular compartments and processes were involved in the response to warming of non-primed plants, while the response of heat-primed plants involved a limited group of processes. Our results suggest that seagrasses acquire a primed state during the priming event, that eventually gives plants the ability to induce a more energy-effective response when the thermal stress event recurs. Different species may differ in their ability to perform an improved heat stress response after priming. This study provides pioneer molecular insights into the emerging topic of seagrass stress priming and may benefit future studies in the field.

Seagrass Community Structure and Ecosystem Carbon Stocks Along the Shoreline of Semujur Island, Bangka Belitung Province, Indonesia

Seagrass meadows serve as vital blue carbon ecosystems, sequestering significant amounts of CO2 and playing a crucial role in climate change mitigation. Semujur Island, located in the Bangka Belitung Province, exemplifies numerous small Indonesian islands boasting extensive seagrass meadows lining their shores. This research seeks to (1) describe the community structure of seagrass on Semujur Island, (2) assess the carbon storage within the seagrass ecosystem, and (3) analyze the relationship between seagrass community structure and carbon reserves across three distinct sites. According to the results of this study, there are eight species of seagrass on Semujur Island, i.e., Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Halophila ovalis, Oceana serrulata, Syringodium isoetifolium, Thalassia hemprichii, and Thalassodendron ciliatum. Diversity indices varied among sites, ranging from 1.48 to 1.72. Species evenness indices varied between 0.83 and 0.92, while dominance indices varied between 0.20 and 0.28. The highest estimated carbon stock was obtained at the site dominated by the species H. uninervis (75.11 MgC/ha); followed by the site dominated by T. hemprichii (50.55 MgC/ha). The correlation between seagrass community structure, including density and coverage, and carbon stocks demonstrated a moderate positive correlation, with coefficients of 0.430 and 0.528, respectively (p<0.05). This research highlights the significance of integrating ecological dynamics into the management of seagrass ecosystems to enhance climate change mitigation efforts. Additionally, it offers valuable data as a reference for the restoration and conservation of seagrass ecosystems.

Trade‐Off Between Light Deprivation and Desiccation in Intertidal Seagrasses Due To Periodic Tidal Inundation and Exposure: Insights From a Data‐Calibrated Model

AbstractSome seagrass species thrive in shallow intertidal zones globally, adapting to periodic tidal inundation and exposure with distinctive physiological traits and offering crucial ecosystem services. However, predicting the responses of intertidal seagrasses to external stressors is hampered by the complexity of the dynamic and harsh environments they occupy. Intertidal seagrass growth models, especially those incorporating dynamic physiological responses, are scarce in the literature. Our study comprehensively collated relevant data from the literature to parameterize the relationship between air exposure, seagrass leaf water content and photosynthetic efficiency to inform new growth rate functions for generalizable intertidal seagrass growth models. We tested the applicability of these model formulations for scenarios with varying physiological process assumptions, seagrass species, tidal conditions, meadow elevations and water turbidity. We found that neglecting air‐exposed physiological responses (i.e., leaf water content loss and reduced photosynthetic efficiency) can substantially overestimate seagrass growth rates. We also observed a trade‐off between light deprivation and desiccation on intertidal seagrass growth under specific tidal ranges and turbidity conditions. This can yield an “optimal” elevation where overall stress of desiccation (increasing with meadow elevation) and light deprivation (decreasing with meadow elevation) are minimized. The predicted optimal elevation, that is, the most suitable habitat for intertidal seagrass, moves upward as water turbidity increases. Our study provides conceptual and quantitative guidance for ecological modelers to include air exposure responses of intertidal seagrasses in coastal ecosystem models. The model also helps to evaluate the viability of intertidal seagrass habitats and inform decisions on coastal ecosystem management under changing environmental conditions.

Potential Carbon Stock of Seagrass Biomass in Malang Regency

Research on blue carbon content in seagrass beds also has important implications for coastal ecosystem management. The goals of this research are: (1) To determine the composition of seagrass species; (2) to analyze the health of the seagrass ecosystem; and (3) and to analyze the carbon content stored in seagrass biomass on the coast of Malang Regency. This research was conducted in 2018 at five stations, namely: Kondang Merak Beach (St 1), Balekambang Beach (St 2), Gatra Beach (St 3), Sendangbiru Beach (St 4), and Waru-Waru Beach (St 5) of Malang Regency. The method used to collect data refers to Seagrass Watch. The biomass value of seagrass species can be estimated by measuring the wet weight and dry weight of seagrass. Analysis of carbon content in seagrass biomass can be calculated using a method that refers to The First Nation-Wide Assessment Identifies Valuable Blue-carbon. There are five types of seagrasses found on five beaches in Malang Regency, namely: Halodule pinifolia, Halodule uninervis, Halophila ovalis, Syringodium isotifolium, and Thalassia hemprichii. This seagrass meadow ecosystem is in an unhealthy condition, with a small biomass value. Seagrass beds that are formed only in the form of small spots (1.19 Ha) are known to be able to store carbon of 0.0544 Mg C.

Dugong dugon (Muller 1776) and Its Habitat in Coastal Areas and Small Islands of East Java Province, Indonesia

Dugong dugon, an endangered marine mammal is listed the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Dugongs are classified as herbivorous mammals that live in the shallows associated with seagrass beds. The objectives of this study are (1) to collect data on dugong encounters in East Java, both direct encounters and literature studies; and (2) to analyze seagrass meadows that are potentially dugong grazing habitats in East Java. This study was conducted from January to July 2023 in the coastal area of East Java. Dugong and seagrass data, which were descriptively analyzed, were obtained from the literature, questionnaire interview, and by direct observation. Distribution of dugongs in East Java is known to be in the southeastern side of Banyuwangi, Situbondo, Sumenep, Lamongan, and Bawean Island. Direct encounters with live and dead dugongs in East Java have been recorded in several locations, including Bawean Island. Seagrass beds in East Java can be found on the coastal area of Lamongan, Bawean Island - Gresik, Sumenep, Bangkalan, Situbondo, Banyuwangi, Malang, and Pacitan. The seagrass species found in these eight areas are: E. acoroides, T. hemprichii, C. modocea rotundata, C. serrulata, H. pinifolia, H. uninervis, H. decipiens, H. ovalis, H. minor, S. iseotifolium, and T. ciliatum. Although, dugong status is fully protected in Indonesia, and its distribution is limited, further steps are needed to protect dugongs and their food habitats. Marine Protected Area is one of the policies that could be recommended to protect dugongs and their habitat.

Variation in genomic vulnerability to climate change across temperate populations of eelgrass (Zostera marina)

AbstractA global decline in seagrass populations has led to renewed calls for their conservation as important providers of biogenic and foraging habitat, shoreline stabilization and carbon storage. Eelgrass (Zostera marina) occupies the largest geographic range among seagrass species spanning a commensurately broad spectrum of environmental conditions. In Canada, eelgrass is managed as a single phylogroup despite occurring across three oceans and a range of ocean temperatures and salinity gradients. Previous research has focused on applying relatively few markers to reveal population structure of eelgrass, whereas a whole‐genome approach is warranted to investigate cryptic structure among populations inhabiting different ocean basins and localized environmental conditions. We used a pooled whole‐genome re‐sequencing approach to characterize population structure, gene flow and environmental associations of 23 eelgrass populations ranging from the Northeast United States to Atlantic, subarctic and Pacific Canada. We identified over 500,000 SNPs, which when mapped to a chromosome‐level genome assembly revealed six broad clades of eelgrass across the study area, with pairwise FST ranging from 0 among neighbouring populations to 0.54 between Pacific and Atlantic coasts. Genetic diversity was highest in the Pacific and lowest in the subarctic, consistent with colonization of the Arctic and Atlantic oceans from the Pacific less than 300 kya. Using redundancy analyses and two climate change projection scenarios, we found that subarctic populations are predicted to be potentially more vulnerable to climate change through genomic offset predictions. Conservation planning in Canada should thus ensure that representative populations from each identified clade are included within a national network so that latent genetic diversity is protected, and gene flow is maintained. Northern populations, in particular, may require additional mitigation measures given their potential susceptibility to a rapidly changing climate.

The potential of seagrass ecosystems in Waai and Liang coastal waters on Ambon Island as carbon storage sites

Seagrass ecosystem is one of the coastal ecosystems that can absorb carbon and subsequently store it at a high capacity. This research aimed to study carbon stocks in biomass based on seagrass type and density, differences in carbon stocks between below-ground and above-ground, and the potential for carbon storage of the seagrass ecosystem on the coast of Waai and Liang, Ambon Island. Five seagrass species species were found, including Enhalus acoroides, Halophila ovalis, Halodule pinifolia, Thalassia hemprichii and Cymodocea rotundata,. Based on the results, halassia hemprichii was predominant in Liang waters and Halodule pinifolia was predominant in Waai waters. The highest seagrass biomass in both the below ground and above ground was found for Cymodocea rotundata in Waai waters and Thalassia hemprichii in Liang waters. The total carbon stock in Liang waters was 39.75 gC/m2, whereas that in Waai waters was 56.46 gC/m2. The results showed that the total carbon stock below ground was much greater than above ground, suggesting that more carbon is stored below seagrass substrate than above it in both Waai and Liang coastal waters.

The resilience of transplanted seagrass traits encourages detection of restoration success

Restoration of coastal ecosystems, particularly those dominated by seagrasses, has become a priority to recover the important ecosystem services they provide. However, assessing restoration outcomes as a success or failure remains still difficult, probably due to the unique features of seagrass species and the wide portfolio of practices used on transplanting actions. Here, several traits (maximum leaf length, number of leaves, leaf growth rate per shoot, and leaf elemental carbon and nitrogen contents) of transplanted seagrass Posidonia oceanica were compared to reference meadows in five sites of Western Mediterranean Sea in which restoration were completed in different times. Results have evidenced the resilience of transplanted P. oceanica shoots within a few years since restoration, as traits between treatments changed depending on the elapsed time since settlement. The highlighted stability of the restoration time effect suggests that the recovery of the plants is expected in four years after transplanting.

The viability of seagrass ecosystems for supporting dugong recovery in Kenya

Seagrasses are the primary source of food for dugongs and a good indicator of marine ecosys- tem health. The East African dugong (Dugong dugon) population is listed as critically endan- gered under the IUCN Red List. This study aimed to document the status of seagrass beds and evaluate their potential for supporting dugong recovery in Kenya. A cross-sectional survey was conducted in December 2016 to March 2017, with data gathered through desktop reviews, inter- views, beach surveys and aerial surveys. Seven seagrass species were found at sampled sites, namely Syringodium isoetifolium, Thalassodendron ciliatum, Halophila ovalis, Zostera capensis, Thal- assia hemprichii, Cymodocea serrulata, and Halodule uninervis. Halodule and Halophila seagrass spe- cies are important in the diet of dugongs. Two dugongs were sighted during the aerial survey. The spread of sea urchins, unplanned infrastructure development, Illegal, Unreported and Unregulated fishing, and boat anchors negatively affected seagrass ecosystems and hence dugong distribution in Kenya.

Nontargeted lipidomics of Florida seagrasses

Seagrasses are one of the most productive foundation species in the world and are important for maintaining ecosystem homeostasis. However, seagrasses have experienced a global decline in areal extent, due in part to environmental stressors. Despite ongoing decline, little is known about the lipidome of most seagrass species. Generally, lipidome profiles closely align with phenotypic changes and can be used to evaluate the condition of an individual. In this study, a nontargeted lipidomics approach, utilizing high-performance liquid chromatography tandem mass spectrometry, was used to assess the lipidome of wild seagrasses in Florida. Overall, 399 individual lipid species, comprised of 33 lipid subclasses, were identified across all specimens. The lipid classes with the highest total concentration, accounting for 75% of total identified lipids in all seagrasses were: monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG), and sulfoquinovosyl diacylglycerols (SQDG). Here, the lipidomic profiles of wild seagrasses were identified for the first time, a necessary step toward using lipodomics as a tool for prospective assessments of condition. Once regional and species-specific baselines have been mapped, lipodomic surveys could provide new insight into the effects of environmental stressors on seagrass condition and help to augment ongoing efforts to document and understand seagrass ecosystem status and trends.

A matter of choice: Understanding the interactions between epiphytic foraminifera and their seagrass host Halophila stipulacea

In sub/tropical waters, benthic foraminifera are among the most abundant epiphytic organisms inhabiting seagrass meadows. This study explored the nature of the association between foraminifera and the tropical seagrass species H. stipulacea, aiming to determine whether these interactions are facilitative or random. For this, we performed a "choice" experiment, where foraminifera could colonize H. stipulacea plants or plastic "seagrasses" plants. At the end of the experiment, a microbiome analysis was performed to identify possible variances in the microbial community and diversity of the substrates. Results show that foraminifera prefer to colonize H. stipulacea, which had a higher abundance and diversity of foraminifera than plastic seagrass plants, which increased over time and with shoot age. Moreover, H. stipulacea leaves have higher epiphytic microbial community abundance and diversity. These results demonstrate that seagrass meadows are important hosts of the foraminifera community and suggest the potential facilitative effect of H. stipulacea on epiphytic foraminifera, which might be attributed to a greater diversity of the microbial community inhabiting H. stipulacea.

Rapid sea level rise causes loss of seagrass meadows

As global declines in seagrass populations continue to cause great concern, long-term assessment of seagrass meadows show promise in furnishing valuable clues into fundamental causes of seagrass loss and drivers of environmental change. Here we report two long-term records of seagrass presence in western Gulf of Mexico coastal waters (Laguna Madre) that provided insight into their rapid decline in a relatively pristine ecosystem. Coincident with unprecedented increases in water depth starting in 2014 (14–25 mm y−1), monthly measurements at a deep edge fixed station revealed that two ubiquitous seagrass species (Halodule wrightii and Syringodium filiforme) vanished altogether in just five years; a subsequent basin-wide assessment revealed that seagrasses disappeared at 23% of 144 sentinel stations. Models that incorporate differing sea level rise scenarios and water depth thresholds reveal potential global losses of seagrass habitat (14,000 km2), with expansion into newly created shallow habitats constrained by altered natural shorelines.

Large-scale environmental signals in seagrass blue carbon stocks are hidden by high variability at local scales

Increasing focus on nature-based climate change mitigation and adaptation strategies has led to the recognition of seagrasses as globally significant organic carbon (Corg) stocks. However, estimates of carbon stocks have been generally confined to a few regions, with few African studies represented in global datasets. In addition, the extent to which biogeographical and environmental variation shape carbon stocks in marine vegetated environments remains uncertain. For South Africa, Zostera capensis is the dominant seagrass species with limited mapping and quantification of its Corg stocks. Here, we measured Z. capensis Corg stocks at six South African estuaries spanning ∼1800 km of the cool-temperate to subtropical marine environmental gradient. Targeting the intertidal zone of the upper and lower estuary reaches, we collected Z. capensis sediments to a depth of 50 cm and measured the Corg, with the median Corg stock estimated at 24.11 Mg C ha−1 (40.4 ± 53.02; mean ± SD). While this is lower than the global average, these data demonstrate that Z. capensis ecosystems are important contributors to blue carbon stocks in the region. Measured Corg stocks showed significant differences between sampling sites for estuaries; however, we did not detect significant differences between estuaries due to high intra-estuarine Corg variability. Examination of biogeographical regions, terrestrial and marine environmental variables as drivers of Corg variability revealed that annual mean sea surface temperature may explain variation in Corg stocks. Furthermore, we found evidence of signals of biogeographical regions and precipitation driving some of the variability in Corg stocks; however, this requires further investigation. Overall, our estimates for Z. capensis add to ongoing national and global efforts to quantify seagrass Corg stocks across environmental and biogeographic gradients to better determine their contributions as nature-based solutions to climate change.

Warming-induced flowering and fruiting in the seagrass Posidonia oceanica and uncertainties due to context-dependent features

This study explores the impacts of global warming on the reproductive efforts of Posidonia oceanica, a key seagrass species endemic to the Mediterranean Sea. By analyzing data from five areas in Sardinia in February 2023, we have investigated the relationship between thermal descriptors and P. oceanica flowering and fruiting variables. In fact, whether climate change has been affected the distribution of seagrasses by changing their reproductive efforts is still controversial and our findings contribute to this ongoing debate, highlighting a noticeable increase in reproductive events potentially affected by rising temperature. Overall, mean summer sea surface temperature (SST) was positively associated to inflorescence density, presence of living fruits and fruit size; living fruits and fruit size were also influenced positively by the maximum SST within 3 months before sampling (November–February). Both flowering and fruiting were negatively affected by the maximum SST within 1 month before inflorescence observation and mean winter SST, respectively, suggesting that P. oceanica reproductive effort depends on the duration and the temporal context in which the anomaly occurs. However, the high variability between meadows of the same area highlights the need of future studies to focus on the uncertainties related to local factors.

Seagrass genomes reveal ancient polyploidy and adaptations to the marine environment.

We present chromosome-level genome assemblies from representative species of three independently evolved seagrass lineages: Posidonia oceanica, Cymodocea nodosa, Thalassia testudinum and Zostera marina. We also include a draft genome of Potamogeton acutifolius, belonging to a freshwater sister lineage to Zosteraceae. All seagrass species share an ancient whole-genome triplication, while additional whole-genome duplications were uncovered for C. nodosa, Z. marina and P. acutifolius. Comparative analysis of selected gene families suggests that the transition from submerged-freshwater to submerged-marine environments mainly involved fine-tuning of multiple processes (such as osmoregulation, salinity, light capture, carbon acquisition and temperature) that all had to happen in parallel, probably explaining why adaptation to a marine lifestyle has been exceedingly rare. Major gene losses related to stomata, volatiles, defence and lignification are probably a consequence of the return to the sea rather than the cause of it. These new genomes will accelerate functional studies and solutions, as continuing losses of the 'savannahs of the sea' are of major concern in times of climate change and loss of biodiversity.

Health Status of Seagrass Meadows Around the Special Economic Zone (SEZ), West Likupang, North Sulawesi

Seagrass ecosystems offer valuable ecosystem services but are highly vulnerable to physical damage caused by human activities and rapid environmental change. Currently, there is very limited information available on monitoring and reporting the health of seagrass beds in Indonesian waters. This study aims to assess the species composition, density, diversity index, percentage of seagrass cover, health condition, and identification of threats to seagrass ecosystems around the West Likupang Special Economic Zone (SEZ), North Sulawesi. The method used was a seagrass watch with line transects and quadrant-shaped frames measuring 50x50 cm2. Transect lines were established through the seagrass ecosystem area at 50 m. There were three line transects at each station 25 m apart. Quadrant frame measuring 50x50 cm2. West Likupang has eight seagrass species including C. rotundata, E. acoroides, H. pinifolia, H. uninervis, H. ovalis, O. serrulata, S. isoetifolium, dan T. hemprichii. The health status of the seagrass is currently healthy, with a dense percentage of coverage. The identification of potential risks from anthropogenic activities such as the household disposal of waste at sea, gleaning, the use of boat anchors and propellers, and the construction of infrastructure in coastal areas, such as hotels and harbonurs, pose significant threats.

Seagrass diversity in Pulau Banyak, Aceh Singkil District, Indonesia

Abstract. Erniati, Andika Y, Imanullah, Imamshadiqin, Erlangga, Rahmad, Tauladan TA, Siregar FR, Fitri A, Ritonga GH. 2023. Seagrass diversity in Pulau Banyak, Aceh Singkil District, Indonesia. Biodiversitas 24: 6621-6628. Seagrass is a high-level plant where life activities are submerged in seawater. Currently, the seagrass ecosystem is threatened with destruction and disappearance. The extent of seagrass ecosystems globally was estimated to have declined by about 58%. The solution to this problem is to balance local communities' utilization of biological resources and biodiversity maintenance. The biodiversity aspect of seagrass is key to the sustainability of seagrass ecosystems. Banyak Island is one of the sub-districts in Aceh Singkil Regency, which consists of a cluster of small islands and has rich fisheries and marine potential, one of them is seagrass, where station 1 is Balong Island, Stasion 2 is Balong Island, Stasion 3 is Lamun Island and Stasion 4 is Rago-Rago Island. This study aimed to assess the diversity of seagrass beds, including seagrass species composition, density, percentage cover, and water quality that affect the existence of seagrass ecosystems. This study used a purposive sampling method with 3 transect lines spaced 50 m perpendicular from the shoreline to the sea. Each transect line has 5 plots with a distance of 10 meters measuring 50 x 50 cm2, and the water quality parameters were measured in situ. This research found 5 seagrass species, namely T. hemprichii, C. rotundata, E. acroides, S. isoetifolium, and H. ovalis. C. rotundata is the species with the highest density on Matahari Island, but seagrass diversity is low, and no species were dominant in the groups. The results of PCA analysis showed that the environmental factors that most influenced the pattern of seagrass distribution and density were nitrate, phosphate, and substrate. The conclusion revealed that seagrass diversity on Banyak Islands is relatively low.

Impact of ship-way channel dredging on a seagrass community in the Gulf of Carpentaria, Australia

Port construction at McArthur River Mine in the western Gulf of Carpentaria, Australia, required the dredging of an access channel through a prolific seagrass community. A 4 km by 60 m channel dredged to 5 m depth removed 18.95ha of intertidal and shallow subtidal seagrass. Dredge spoil was pumped onshore to settle in multiple ponds before the decant water returned to the gulf. Quantitative surveys of the seagrass community surrounding the channel using a Before After Control Impact Repeated measures (BACIR) experiment were conducted to investigate the effect of the channel construction on the seagrass community.Nine seagrass species were found during the surveys, but not all species were found in each of the impact or control sectors at all times. Syringodium isoetifolium (Ascherson) Dandy and Cymodocea serrulata (R.Brown) Ascherson and Magnus were the most common and extensive seagrasses (occurring mid- and offshore), while Halophila ovalis (R.Brown) Hook and Halodule uninervis (Forsskal) Ascherson were also abundant (occurring inshore). Twenty-five months after the completion of dredging no significant impact of channel dredging was identified: neither a retreat of seagrasses from the channel, a decline in seagrass cover, nor a reduction in biomass or shoot density. The sediment particle size distribution in the impact sector did not change. Changes in seagrass abundance were detected, but they were consistent in both the impact and control sectors (5–24 km distant from the dredged channel). During both pre- and all post-dredging surveys, seagrasses were found at about 80% of sites (range 79%–84%) in the impact sector (>300 sites). Dredge spoil was pumped onshore, then contained and settled in bunded ponds. Decant water was free of sediment. Sedimentation, elevated turbidity and light attenuation in the vicinity of the operating dredge was minimal and had no deleterious effect on the seagrass community.

Variasi Spasial Kepadatan Cacing Kacang di Pantai Toronipa Sulawesi Tenggara

The density of peanut worms is concentrated in the subtidal zone and is closely related to the substrate where they live. This research aims to determine spatial variations in peanut worm density. This research was carried out at Toronipa Beach, Southeast Sulawesi from June 2020 to February 2021. Peanut worms were collected using a hand scoop to a depth of ±10 cm in a 10x10 m2 quadrat transect at each station. Data were analyzed using standard formulas and tested using Mann-Whitney and linear regression. The results showed that the highest density of peanut worms was found at station II with a mean value of 12±104 ind/10m2 which was significantly different from stations I and III with densities of 9±52 ind/10m2 and 7±124 ind/10m2 respectively. Five types of seagrass were identified, namely Cymodocea rotundata, Enhalus acoroides, Halodule uninervis, Halophila minor, and Thalassia hemprichii. The number of seagrass species found at stations I, II, and III were 1, 2, and 5, respectively. Peanut worm density was positively correlated with seagrass density with a coefficient of determination of 86.45%. Water quality tends to be the same at all stations, except that organic matter is higher than at stations I and II. The dominant fine sand fraction was found at stations I and III, while very coarse sand was dominantly found at station II. The density of peanut worms on Toronipa Beach is determined by a combination of seagrass density, high levels of organic matter, and the dominant texture of the coarse sand substrate.
 
 Keywords: peanut worm, spatial density, Sulawesi, water quality

The under-investigated plastic threat on seagrasses worldwide: a comprehensive review.

Marine plastic pollution is a well-recognised and debated issue affecting most marine ecosystems. Despite this, the threat of plastic pollution on seagrasses has not received significant scientific attention compared to other marine species and habitats. The present review aims to summarise the scientific data published in the last decade (January 2012-2023), concerning the evaluation of plastic pollution, of all sizes and types, including bio-based polymers, on several seagrass species worldwide. To achieve this goal, a comprehensive and critical review of 26 scientific papers has been carried out, taking into consideration the investigated areas, the seagrass species and the plant parts considered, the experimental design and the type of polymers analysed, both in field monitoring and in laboratory-controlled experiments. The outcomes of the present review clearly showed that the dynamics and effects of plastic pollution in seagrass are still under-explored. Most data emerged from Europe, with little or no data on plastic pollution in North and South America, Australia, Africa and Antarctica. Most of the studies were devoted to microplastics, with limited studies dedicated to macroplastics and only one to nanoplastics. The methodological approach (in terms of experimental design and polymer physico-chemical characterisation) should be carefully standardised, beside the use of a model species, such as Zostera marina, and further laboratory experiments. All these knowledge gaps must be urgently fulfilled, since valuable and reliable scientific knowledge is necessary to improve seagrass habitat protection measures against the current plastic pollution crisis.