Marine Macrophytes as Carbon Sinks: Comparison Between Seagrasses and the Non-native Alga Halimeda incrassata in the Western Mediterranean (Mallorca)

Seagrass species play a critical role in the mitigation of climate change by acting as valuable carbon sinks and storage sites. Another important ecosystem service of this coastal vegetation is nutrient removal. However, coastal ecosystems are under increasing pressure of global warming and associated establishment of invasive species. To elucidate the respective contributions of seagrass species Posidonia oceanica and Cymodocea nodosa and the non-native macroalga Halimeda incrassata as primary producers and nutrient sinks in coastal habitats we conducted in-situ incubations in the North-western Mediterranean Sea. Measured metabolic activity and nutrient removal as well as calcification rates in these habitats over a 24 h period in spring and summer confirmed that the endemic seagrass P. oceanica represents a valuable ecosystem with high O2 production and considerable carbon capture. The documented regression of P. oceanica meadows with higher temperatures and decline in autotrophy as measured here causes concern for the continuity of ecosystem services rendered by this habitat throughout the Mediterranean Sea with progressing climate warming. In contrast, the enhanced performance of C. nodosa and the calcifying alga H. incrassata with increasing temperatures, under expected rates of future warming is uncertain to mitigate loss of productivity in case of a potential shift in marine vegetation. This could ultimately lead to a decline in ecosystem services, decreased carbon storage and mitigation of climate change. Furthermore, this study provides a first estimate for the growth rate of H. incrassata in the Mediterranean Sea, supporting evidence for the mechanism of its rapid extension.

Local Victory: Assessing Interspecific Competition in Seagrass From a Trait-Based Perspective

Tropical seagrass meadows are formed by an array of seagrass species that share the same space. Species sharing the same plot are competing for resources, namely light and inorganic nutrients, which results in the capacity of some species to preempt space from others. However, the drivers behind seagrass species competition are not completely understood. In this work, we studied the competitive interactions among tropical seagrass species of Unguja Island (Zanzibar, Tanzania) using a trait-based approach. We quantified the abundance of eight seagrass species under different trophic states, and selected nine traits related to light and inorganic nutrient preemption to characterize the functional strategy of the species (leaf maximum length and width, leaves per shoot, leaf mass area, vertical rhizome length, shoots per meter of ramet, rhizome diameter, roots per meter of ramet, and root maximum length). From the seagrass abundance we calculated the probability of space preemption between pairs of seagrass species and for each individual seagrass species under the different trophic states. Species had different probabilities of space preemption, with the climax species Thalassodendron ciliatum, Enhalus acoroides, Thalassia hemprichii, and the opportunistic Cymodocea serrulata having the highest probability of preemption, while the pioneer and opportunistic species Halophila ovalis, Syringodium isoetifolium, Halodule uninervis, and Cymodocea rotundata had the lowest. Traits determining the functional strategy showed that there was a size gradient across species. For two co-occurring seagrass species, probability of preemption was the highest for the larger species, it increased as the size difference between species increased and was unaffected by the trophic state. Competitive interactions among seagrass species were asymmetrical, i.e., negative effects were not reciprocal, and the driver behind space preemption was determined by plant size. Seagrass space preemption is a consequence of resource competition, and the probability of a species to exert preemption can be calculated using a trait-based approach.

Phytochemical profiles and ethnomedicine preliminary studies on seagrass species in the Southern Coast of Lombok Island Indonesia

Seagrass is a coastal plant that is not only important in maintaining the stability of coastal ecosystems, but also provides many benefits in daily life. Seagrass has long been used as traditional medicine by coastal residents in South Lombok. The purpose of this study was to screen the main types of secondary metabolites contained in seagrass in the southern coast of Lombok Island and to obtain information about the species of seagrass used as traditional medicine for certain types of diseases in local residents. Seagrass samples were taken from the south coast and the extraction process was carried out by maceration method using 96% ethanol as solvent. The crude extract obtained was then subjected to qualitative and quantitative phytochemical tests. The phytochemical qualitative test showed that Syringodium isoetifolium, Enhalus acoroides, Halophila decipiens, Cymodocea rotundata, Thalassia hemprichii, and Cymodocea cerulata contain compounds such as flavonoids, tannins, and phenols. Quantitative phytochemical analysis showed that E. acoroides had the highest total flavonoid content (3.7 mg QE/g) compared to that of other species, while the highest total phenolic content was indicated by T. hemprichii (33 mg GAE/100 g). The results of interviews related to the ethnomedicinal aspects of seagrass indicate that four species commonly used by local residents in healing diseases are E. acoroides, S. isoetifolium, T. hemprichii, and C. cerulata. They are widely used both as an external medicine (itching-skin diseases and external wounds) and internal medicine, such as heart, cancer, and kidney disease. Based on the phytochemical profile and ethnomedicine studies, the four seagrass species can be an alternative source in obtaining bioactive compounds for the development of specific drugs in the future.

KOMUNITAS LAMUN DI PERAIRAN PANTAI DESA ORI, MALUKU TENGAH

Seagrass communities play an important role in marine environments and estuary area, supporting communities of fish, snails and shellfish and other invertebrates. The diversity of seagrass species in the world is very low (<60 species). The coastal waters of Ori Village have a seagrass community that has never been studied. The purpose of this study was to estimate the structure of the seagrass community in the coastal waters of Ori Village, Central Maluku which includes the composition of type, density, frequency of occurence and percent of coverage. Seagrass sampling uses the line transect method. Five species of seagrass were found during the study grouped into two families: Cymodoceaceae and Hydrocharitaceae. The seagrass species found were Cymodocea rotundata, Halodule pinifolia, Enhalus acoroides Halophila ovalis and Thalassia hemprichii. T. hemprichii and E. acoroides have the highest densities (157 shoots/m2 and 137 shoots/m2, respectively). E. acoroides and T. hemprichii also have the highest frequency of occurence and relative coverage percent compared to other seagrass species found in the waters of Ori Village. Seagrass community in the waters of Ori Village is classified in a tight condition until dense. ABSTRAK Komunitas lamun memegang peranan penting di lingkungan laut dan daerah estuari, menyokong komunitas ikan, siput dan kerang-kerangan serta invertebrata lainnya. Keragaman spesies lamun di dunia sangat rendah (<60 spesies). Perairan pantai Desa Ori memiliki komunitas lamun yang belum pernah diteliti. Tujuan dari penelitian ini adalah untuk mengestimasi struktur komunitas lamun di perairan pantai Desa Ori, Maluku Tengah yang meliputi komposisi jenis, kerapatan, frekuensi kehadiran dan persen penutupan. Pengambilan sampel lamun menggunakan metode transek garis. Lima spesies lamun ditemukan selama penelitian yang dikelompokan dalam dua famili yaitu famili Cymodoceaceae dan Hydrocharitaceae. Spesies-spesies lamun yang ditemukan adalah Cymodocea rotundata, Halodule pinifolia, Enhalus acoroides Halophila ovalis danThalassia hemprichii. T. hemprichii dan E. acoroides memiliki kerapatan tertinggi (masing-masing 157 tegakan/m2 dan 137 tegakan/m2). E. acoroides dan T. hemprichii juga memiliki frekuensi kehadiran serta persen penutupan relatif tertinggi dibanding spesies-spesies lamun lainnya yang ditemukan di perairan Desa Ori. Komunitas lamun di perairan Desa Ori tergolong dalam kondisi rapat sampai padat. Kata Kunci: Lamun, komunitas, kerapatan, penutupan, Maluku Tengah

Potensi Kandungan Karbon Keragaman Spesies Lamun di Perairan Pesisir Selatan Lombok Timur

through the development of carbon zinc as an organic material produced from photosynthesis and stored and transported in the form of seagrass vegetation biomass. Seagrass is one of the aquatic vegetation that is able to absorb and store carbon. Seagrasses have the ability to absorb carbon through the process of photosynthesis. The purpose of this study was to describe the potential carbon content of seagrass species in the South Coastal Waters of East Lombok. This type of research is an expolarative descriptive research. The research method is a quadratic transect method. The population of this study were all seagrass species contained in 3 research stations. The collected data was then analyzed using analysis of seagrass species composition, seagrass cover, seagrass density, diversity, uniformity, dominance and analysis of carbon content through seagrass stand biomass (leaves, rhizomes/stems and roots). The result of this research is the discovery of 9 species of seagrass on Lungkak Beach and 5 species of seagrass on Gili Kere and Poton Bakau. The species density in the three study sites ranged from 0.09 to 56.91 stands/m2. Seagrass biomass values ranged from 1.47-261.9 gbk/m2 and total carbon content ranged from 295.91±202.88 gC. The value of this biomass and carbon content was dominated by seagrass species with large morphology such as Enhalus acroides, Thalasia hemprici, Cymodocea rotundata, and Cymodocea cerillata and high density and cover values of seagrass. The relationship between seagrass cover and seagrass carbon has a significant relationship where the higher the seagrass cover, the higher the carbon content of the seagrass.

Comparative Chloroplast Genomes of Zosteraceae Species Provide Adaptive Evolution Insights Into Seagrass

Seagrasses are marine flowering plants found in tropical and sub-tropical areas that live in coastal regions between the sea and land. All seagrass species evolved from terrestrial monocotyledons, providing the opportunity to study plant adaptation to sea environments. Here, we sequenced the chloroplast genomes (cpGenomes) of three Zostera species, then analyzed and compared their cpGenome structures and sequence variations. We also performed a phylogenetic analysis using published seagrass chloroplasts and calculated the selection pressure of 17 species within seagrasses and nine terrestrial monocotyledons, as well as estimated the number of shared genes of eight seagrasses. The cpGenomes of Zosteraceae species ranged in size from 143,877 bp (Zostera marina) to 152,726 bp (Phyllospadix iwatensis), which were conserved and displayed similar structures and gene orders. Additionally, we found 17 variable hotspot regions as candidate DNA barcodes for Zosteraceae species, which will be helpful for studying the phylogenetic relationships and interspecies differences between seagrass species. Interestingly, nine genes had positive selection sites, including two ATP subunit genes (atpA and atpF), two ribosome subunit genes (rps4 and rpl20), two DNA-dependent RNA polymerase genes (rpoC1 and rpoC2), as well as accD, clpP, and ycf2. These gene regions may have played key roles in the seagrass adaptation to diverse environments. The Branch model analysis showed that seagrasses had a higher rate of evolution than terrestrial monocotyledons, suggesting that seagrasses experienced greater environmental pressure. Moreover, a branch-site model identified positively selected sites (PSSs) in ccsA, suggesting their involvement in the adaptation to sea environments. These findings are valuable for further investigations on Zosteraceae cpGenomes and will serve as an excellent resource for future studies on seagrass adaptation to sea environments.

Spatial and Species Variations of Bacterial Community Structure and Putative Function in Seagrass Rhizosphere Sediment

Seagrasses are an important part of the coral reef ecosystem, and their rhizosphere microbes are of great ecological importance. However, variations in diversity, composition, and potential functions of bacterial communities in the seagrass rhizosphere of coral reef ecosystems remain unclear. This study employed the high-throughput sequencing based on 16S rDNA gene sequences and functional annotation of prokaryotic taxa (FAPROTAX) analysis to investigate these variations based on seagrass species and sampling locations, respectively. Results demonstrated that the seagrass rhizosphere microbial community was mainly dominated by phylum Proteobacteria (33.47%), Bacteroidetes (23.33%), and Planctomycetes (12.47%), while functional groups were mainly composed of sulfate respiration (14.09%), respiration of sulfur compounds (14.24%), aerobic chemoheterotrophy (20.87%), and chemoheterotrophy (26.85%). Significant differences were evident in alpha diversity, taxonomical composition and putative functional groups based on seagrass species and sampling locations. Moreover, the core microbial community of all investigated samples was identified, accounting for 63.22% of all obtained sequences. Network analysis indicated that most microbes had a positive correlation (82.41%), and two module hubs (phylum Proteobacteria) were investigated. Furthermore, a significant positive correlation was found between the OTUs numbers obtained and the functional groups assigned for seagrass rhizosphere microbial communities (p < 0.01). Our result would facilitate future investigation of the function of seagrass rhizosphere microbes.

Opportunistic gut sampling indicates differential diet and plastic ingestion risk in Indian dugongs

Dugongs, exclusively seagrass foragers, are globally threatened marine mammals. Knowledge on their feeding biology has been derived from few direct observations and mostly by analysis of stomach contents. Given limitations in data from Indian populations, dugong strandings serve as an opportunity to understand their dietary composition through gut sampling. In this paper, we utilize the gut contents collected from stranded dugongs to detect differences in the seagrass foraging between two isolated pockets of dugong distribution (Tamil Nadu and Gujarat) and supplement existing knowledge on dugong feeding biology in Indian waters. We extracted, enumerated and identified seagrass species from dugong gut contents. The proportion of seagrass leaf fragments were found higher (>40%) than other fragments in all the gut samples analysed. We recorded two seagrass genera (Halophila spp. and Halodule spp.) from Gujarat and five seagrass genera (Halophila spp., Halodule spp., Cymodocea spp., Enhalus spp., Syringodium spp.) from Tamil Nadu dugong individuals. We also obtained anthropogenic debris such as plastic, fishing net and wood fragments from the gut samples. We suggest enhanced monitoring of seagrass habitats and fine spatial scale threat mapping in entire dugong distribution range in India.