Halophila Stipulacea Research Articles

Differences in flowering sex ratios between native and invasive populations of the seagrass Halophila stipulacea

Abstract Deviations from the 1:1 sex ratio are common in dioecious plants. The tropical seagrass Halophila stipulacea is among an extremely rare group of dioecious plants that are widely recognized as female-biased. Here we report on differences in sex ratios between native (Eilat, northern Red Sea) and invasive (Cyprus, Mediterranean Sea) populations. While H. stipulacea populations were female-biased in their native region, invasive populations were either male- or female-biased. The existence of both sexes simultaneously in the Mediterranean invasive populations might help its ongoing expansion in the Mediterranean, thereby threatening local seagrasses species.

The Tropical Invasive Seagrass, Halophila stipulacea, Has a Superior Ability to Tolerate Dynamic Changes in Salinity Levels Compared to Its Freshwater Relative, Vallisneria americana.

The tropical seagrass species, Halophila stipulacea, originated from the Indian Ocean and the Red Sea, subsequently invading the Mediterranean and has recently established itself in the Caribbean Sea. Due to its invasive nature, there is growing interest in understanding this species’ capacity to adapt to new conditions. One approach to understanding the natural tolerance of a plant is to compare the tolerant species with a closely related non-tolerant species. We compared the physiological responses of H. stipulacea exposed to different salinities, with that of its nearest freshwater relative, Vallisneria americana. To achieve this goal, H. stipulacea and V. americana plants were grown in dedicated microcosms, and exposed to the following salt regimes: (i) H. stipulacea: control (40 PSU, practical salinity units), hyposalinity (25 PSU) and hypersalinity (60 PSU) for 3 weeks followed by a 4-week recovery phase (back to 40 PSU); (ii) V. americana: control (1 PSU), and hypersalinity (12 PSU) for 3 weeks, followed by a 4-week recovery phase (back to 1 PSU). In H. stipulacea, leaf number and chlorophyll content showed no significant differences between control plants and plants under hypo and hypersalinities, but a significant decrease in leaf area under hypersalinity was observed. In addition, compared with control plants, H. stipulacea plants exposed to hypo and hypersalinity were found to have reduced below-ground biomass and C/N ratios, suggesting changes in the allocation of resources in response to both stresses. There was no significant effect of hypo/hypersalinity on dark-adapted quantum yield of photosystem II (Fv/Fm) suggesting that H. stipulacea photochemistry is resilient to hypo/hypersalinity stress. In contrast to the seagrass, V. americana exposed to hypersalinity displayed significant decreases in above-ground biomass, shoot number, leaf number, blade length and Fv/Fm, followed by significant recoveries of all these parameters upon return of the plants to non-saline control conditions. These data suggest that H. stipulacea shows remarkable tolerance to both hypo and hypersalinity. Resilience to a relatively wide range of salinities may be one of the traits explaining the invasive nature of this species in the Mediterranean and Caribbean Seas.

Comparative assessment of trace element accumulation and bioindication in seagrasses Posidonia oceanica, Cymodocea nodosa and Halophila stipulacea

Accumulation and bioindication of trace elements were compared in three seagrasses growing in the Mediterranean Sea: Posidonia oceanica, Cymodocea nodosa and Halophila stipulacea. The levels of the elements As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn were investigated in water, sediments, and roots, rhizomes and leaves of seagrasses. Results showed that seagrasses can accumulate comparable levels of trace elements, but P. oceanica and C. nodosa showed higher mean values of element accumulation. Moreover, P. oceanica and C. nodosa may accumulate high element concentrations in their leaves, whereas in H. stipulacea restricted with the bulk of trace elements in roots and rhizomes. Seagrasses reflected to a different degree the levels of several trace elements in sediments, especially P. oceanica and C. nodosa, whose use as bioindicators is recommended. The future step for an effective use of seagrasses as bioindicators of marine pollution is to set up biomonitoring networks on a large scale.

Karyomorphology and DNA quantification in the marine angiosperm Halophila stipulacea (Forsskål) Ascherson from Mediterranean and Red Seas

Cytogenetic studies for systematic and evolutionary purposes are lacking on marine phanerogams. Halophila stipulacea is a tropical seagrass that invaded the Mediterranean from the Red Sea through the Suez Canal. In this study, we report, for the first time, the karyotype features and genome size of H. stipulacea populations from different localities. Also, an attempt to compare our data with those reported in literature on other Halophila species is discussed. To determine the karyological relationships among taxa, we used basic karyotypic features such as chromosome number, size and symmetry, and position of chromosomal landmarks. To estimate karyotype asymmetry, the Coefficient of Variation of Chromosome Length (CVCL) and the Mean Centromeric Asymmetry (MCA) values were calculated. The estimations of DNA amounts were carried out by Image Cytometry (IC) using the interphase-peak method. All the taxa, including those reported in literature, present a uniform and slightly bimodal karyotype, but significant differences are found in nuclear DNA content among species. Each taxa had a karyotype formula 2n = 18 = 10m + 2sm + 6st. Aneuploidy and polyploidy seemed to not be involved in the speciation of this genus. The conserved karyotype in these taxa suggests the presence of mechanisms selecting for constancy, or against changes, in karyotype number and morphology.

Seagrass Halophila stipulacea: Capacity of accumulation and biomonitoring of trace elements

This study aimed to shed further light on the capacity of the seagrass Halophila stipulacea to accumulate and biomonitor the elements As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn, present in water and sediments. Results showed that the organs of H. stipulacea accumulate different levels of trace elements, whose concentrations decrease mainly in the order of roots>rhizomes>leaves. The seagrass H. stipulacea showed levels of trace elements similar to those found in other Mediterranean seagrasses, e.g. Posidonia oceanica and Cymodocea nodosa. This study showed that H. stipulacea could act as a promising bioindicator of several elements, present in sediments, including As, Cd, Cu, Mn, Ni and Zn.

Depth distribution of benthic dinoflagellates in the Caribbean Sea

Monitoring of benthic dinoflagellates is usually conducted between sub-surface and 5 m depth, where these organisms are supposed to be in highest abundances. However, only few studies have focused on the small-scale depth distribution of benthic dinoflagellates. In the present study, abundances of dinoflagellates were evaluated on an invasive macrophyte Halophila stipulacea in two coastal sites in Guadeloupe (Caribbean Sea) along a depth gradient from sub-surface to 3 m at Gosier and until 20 m at Rivière Sens during the tropical wet and dry seasons. Species of genus Ostreopsis and Prorocentrum were the most abundant. Depth did not influence total dinoflagellate abundance but several genera showed particular depth-distribution preferences. The highest abundances of Ostreopsis and Gambierdiscus species were estimated preferentially in surface waters, whereas Coolia spp. were found in the same proportions but in deeper waters. Halophila stipulacea biomass was positively correlated with Ostreopsis spp. abundance. Our study suggests that sampling of benthic dinoflagellates should be conducted at different water depths taking into account the presence of the macroalgal substrate as well. In the Caribbean area, special attention should be addressed to the presence of H. stipulacea which tends to homogenize the marine landscape and represents a substrate for hosting dinoflagellate growth.

A functional-structural model of ephemeral seagrass growth influenced by environment.

Ephemeral seagrasses that respond rapidly to environmental changes are important marine habitats. However, they are under threat due to human activity and are logistically difficult and expensive to study. This study aimed to develop a new functional-structural environmentally dependent model of ephemeral seagrass, able to integrate our understanding of ephemeral seagrass growth dynamics and assess options for potential management interventions, such as seagrass transplantation. A functional-structural plant model was developed in which growth and senescence rates are mechanistically linked to environmental variables. The model was parameterized and validated for a population of Halophila stipulacea in the Persian Gulf. There was a good match between empirical and simulated results for the number of apices, net rhizome length or net number of internodes using a 330 d simulation. Simulated data were more variable than empirical data. Simulated structural patterns of seagrass rhizome growth qualitatively matched empirical observations. This new model successfully simulates the environmentally dependent growth and senescence rates of our case-study ephemeral seagrass species. It produces numerical and visual outputs that help synthesize our understanding of how the influence of environmental variables on plant functional processes affects overall growth patterns. The model can also be used to assess the potential outcomes of management interventions like seagrass transplantation, thus providing a useful management tool. It is freely available and easily adapted for new species and locations, although validation with more species and environments is required.

Evaluation of Antioxidant and Antibacterial properties of Halophila stipulacea Leaves Extracts obtained from (Alwajh) North of Yanbu City

Evaluation of Antioxidant and Antibacterial properties of Halophila stipulacea Leaves Extracts obtained from (Alwajh) North of Yanbu City

Species-specific response to sulfide intrusion in native and exotic Mediterranean seagrasses under stress

We explored the sulfur dynamics and the relationships between sediment sulfur and nutrient pools, seagrass structural and physiological variables and sulfide intrusion in native (Posidonia oceanica, Cymodocea nodosa) and exotic (Halophila stipulacea) Mediterranean seagrasses at six sites affected by cumulative anthropogenic pressures to understand the factors controlling sulfide intrusion in seagrass. Sensitive indicators of seagrass stress (leaf TN, δ15N, TS, Fsulfide) were increased at several sites, implying that seagrasses are under pressure. Sulfide intrusion was not related to sediment TOC but it was negatively related to shoot size and below-ground biomass. Sulfide intrusion in seagrass tissue was high in P. oceanica (12–17%) and considerably higher in C. nodosa (27–35%). Intrusion was particularly high in H. stipulacea (30–50%), suggesting that its possible biogeographical expansion due to warming of the Mediterranean may result in accumulation of sulfides in the sediments and hypoxia/anoxia with further implications in ecosystem function.

Rare phytomyxid infection on the alien seagrass Halophila stipulacea in the southeast Aegean Sea

Phytomyxids (Phytomyxea) are obligate endosymbionts of many organisms such as algae, diatoms, oomycetes and higher plants including seagrasses. Despite their supposed significant roles in the marine ecosystem, our knowledge of their marine diversity and distribution as well as their life cycles is very limited. Here we describe anatomy and morphology of several developmental stages of a phytomyxid symbiosis recently discovered on the petioles of the alien seagrass Halophila stipulacea (Forssk.) Asch. at a locality in the southeast Aegean Sea. Its earliest whitish stages appeared already on the youngest leaves at the apex of the newly formed rhizomes. The infected host cells grew in volume being filled with plasmodia which resulted in the formation of characteristic macroscopic galls. The plasmodia eventually cleaved into spores and in the final stage recorded by us, the dark brown to black galls contained mature resting spores often occurring in duplexes and possessing thick verrucous outer walls. Based on its anatomo-morphological features the phytomyxid was assigned as Plasmodiophora cf. halophilae. Little is so far known about the origins and eco-physiological functioning of this rare symbiosis. However, seemingly similar infection patterns were reported in 1913 on Halophila ovalis (R. Br.) Hook. f. from Java and in 1995 on H. stipulacea from Sicily. Since H. stipulacea is of the Indo-Pacific origin and no phytomyxid infection was observed on the co-occurring autochthonous seagrass Cymodocea nodosa, we hypothesize that its phytomyxid might have co-migrated into the Mediterranean through the Suez Canal, potentially reaching as far as the southern Ionian Sea.

Altered juvenile fish communities associated with invasive Halophila stipulacea seagrass habitats in the U.S. Virgin Islands.

Caribbean seagrass habitats provide food and protection for reef-associated juvenile fish. The invasive seagrass Halophila stipulacea is rapidly altering these seascapes. Since its arrival in the Caribbean in 2002, H. stipulacea has colonized and displaced native seagrasses, but the function of this invasive seagrass as a juvenile fish habitat remains unknown. To compare diversity, community structure, and abundance of juvenile fish between H. stipulacea and native seagrass beds, fish traps were deployed in four nearshore bays around St. Thomas, U.S. Virgin Islands. Traps were deployed in Frenchman, Lindbergh, and Sprat Bays for 24 h intervals in patches of bare sand, patches of H. stipulacea and patches of the native Caribbean seagrasses Thalassia testudinum and Syringodium filiforme. Traps were then deployed in Brewers Bay for 12 h intervals in stands of H. stipulacea and S. filiforme. Relative and total abundances of juvenile fish, identified at least to family, were compared across treatment habitats for each trap deployment period. The catch from H. stipulacea, compared to native seagrasses, comprised a greater abundance of nocturnal carnivores Lutjanus synagris (family Lutjanidae) and Haemulon flavolineatum (family Haemulidae). Additionally, the herbivore species Sparisoma aurofrenatum (family Labridae) and Acanthurus bahianus (family Acanthuridae) and the diurnal carnivore species Pseudopeneus maculatus (family Mullidae) were relatively scarce in H. stipulacea. The catch from sand was much smaller, compared to vegetated habitats, and comprised only L. synagris, H. flavolineatum, and H. aurolineatum. These results provide evidence of reduced family diversity and altered juvenile fish assemblages in H. stipulacea, driven by an abundance of some nocturnal carnivores and scarcity of herbivores and diurnal carnivores. The findings from the present work underpin the need for further investigation and mitigation of this invasion, particularly where H. stipulacea is driving seascape-alterations of key juvenile fish habitats.

Distribution and abundance of the invasive seagrass Halophila stipulacea and associated benthic macrofauna in Carriacou, Grenadines, Eastern Caribbean

The invasive seagrass Halophila stipulacea has spread throughout the eastern Caribbean since it was first recorded in Grenada in 2002. We quantified the distribution and abundance of H. stipulacea, and its associated macroinvertebrate fauna, in sampling stations and transects around the island of Carriacou (a nearby dependency of Grenada) in early 2016. Halophila stipulacea occurred in extensive monospecific stands (average bottom cover, 62%), or smaller mixed stands with native seagrass (Thalassia testudinum, Syringodium filiforme, Halodule wrightii), at 1–5m depth in large bays along the leeward (west) coast. It was sparsely distributed on the more wave-exposed east and south coasts, usually in mixed patches with native seagrass. In leeward bays, H. stipulacea has largely replaced the native seagrass H. wrightii, providing a novel biogenic habitat for various filter-feeding invertebrates living within the turf-like leaf canopy (e.g., sponges, ascidians, bivalves, ophiuroids), and sea urchins (mainly Tripneustes ventricousus) and a microphagous sea star (Oreaster reticulatus) that graze upon it. Populations of the sea star consisted mainly of juveniles indicating the seagrass may serve as a nursery habitat for this endangered species. The spread of H. stipulacea along the leeward coast of Carriacou in recent years represents a community-level shift in the shallow subtidal zone, with attendant changes in habitat structure, species composition, and trophic interactions.

Ecological typologies of large areas. An application in the Mediterranean Sea

One approach to identifying and mapping the state of marine biophysical conditions is the identification of large-scale ecological units for which conditions are similar and the strategies of management may also be similar. Because biological processes are difficult to directly record over large areas, abiotic characteristics are used as surrogate parameters. In this work, the Mediterranean Sea was classified into homogeneous spatial areas based on abiotic variables. Eight parameters were selected based on salinity, sea surface temperature, photosynthetically active radiation, sea-wave heights and depth variables. The parameters were gathered in grid points of 0.5° spatial resolution in the open sea and 0.125° in coastal areas. The typologies were obtained by data mining the eight parameters throughout the Mediterranean and combining two clustering techniques: self-organizing maps and the k-means algorithm. The result is a division of the Mediterranean Sea into seven typologies. For these typologies, the classification recognizes differences in temperature, salinity and radiation. In addition, it separates coastal from deep areas. The influence of river discharges and the entrance of water from other seas are also reflected. These results are consistent with the ecological requirements of the five studied seagrasses (Posidonia oceanica, Zostera marina, Zostera noltei, Cymodocea nodosa, Halophila stipulacea), supporting the suitability of the resulting classification and the proposed methodology. The approach thus provides a tool for the sustainable management of large marine areas and the ability to address not only present threats but also future conditions, such as climate change.

N2 fixation and primary productivity in a red sea Halophila stipulacea meadow exposed to seasonality

AbstractThe tropical seagrass Halophila stipulacea exhibits a limited capacity to use nitrate, but has a high uptake capacity and efficiency for ammonium. Consequently, N2 fixation by associated diazotrophic epiphytes may be important in providing ammonium needed for seagrass photosynthesis and growth. When exposed to seasonality, this association could provide a competitive advantage for H. stipulacea in relation to other seagrass species, but related knowledge is scarce. Here, we thus report measurements of net photosynthesis (O2 fluxes) and N2 fixation (acetylene reduction) associated with H. stipulacea from the Northern Red Sea over all four seasons of 2013. In parallel, we characterized the seagrass meadow areal extent, shoot and leaves density, and the leaf area index. Using this data, we quantified meadow net primary production and N2 fixation and estimated the photo‐metabolic N demand met by N2 fixation at the community level. Results revealed a marked seasonality of meadow N2 fixation, with rates ranging from 0.06 in winter to 4.60 mmol N m−2 d−1 in summer, i.e., an increase by two orders of magnitude. In summer, when nutrient concentrations in the water column were lowest and light intensity and temperature highest, there was a significant positive linear relationship between meadow net primary production and N2 fixation, with the latter accounting for ca. 20% of the photo‐metabolic N demand. These findings suggest that N2 fixation by associated diazotrophic epiphytes can mitigate N limitation of H. stipulacea meadows under N scarcity. This trait may also favor the ongoing geographical expansion of H. stipulacea.

English

Flowers of the seagrass Halophila stipulacea (Forsskål) Ascherson in Tanzania are currently unreported. The present study was conducted along the coast of Tanzania, Indo-Pacific, Kunduchi intertidal mudflats. Transplanted cuttings from Kunduchi intertidal mudflats were successfully grown in sand-mud substrate in the growth chamber in a 12 h photoperiod (1,250 µmol photons m-2s-1) and an inductive temperature, salinity, and pH range of 24 to 28°C, 34 to 38‰, and 7 to 8, respectively. Plants began to flower after four months of culturing. No flowers were observed in the first three months; 0.229±0.50 staminate and 0.123±0.45 pistillate were recorded between April and June; 0.440±0.65 staminate and 0.221±0.03 pistillate between July and September, and 0.282±0.36 staminate and 0.105±0.78 pistillate between October and December. Although, further research is required to fully assess the pollination success and sexual reproduction including fruiting of the species, our study is the first to report the presence of flowers ex situ in Tanzania. Key words: Mudflats, laboratory culture, sexual reproduction.

Present environmental status of Al-Kharrar Lagoon, central of the eastern Red Sea coast, Saudi Arabia

Al-Kharrar Lagoon is a fossil back-reef basin with hypersaline waters, situated 10 km northwest of Rabigh city, central of the eastern Red Sea coast, Saudi Arabia. About 130 stations were selected for measurements of the lagoon’s water temperature, salinity, pH, dissolved oxygen, and water depths during March 2014. The common macro-algae, flora, and fauna were also sampled and identified. The present study aims to investigate the prevailing environmental parameters and their impact on the macro-fauna/flora of the lagoon. The average water depth of the lagoon was around 5 m and reached maximum values of 8 and 16 at the lagoon centre and inlet, respectively. The results showed that the lagoon’s surface water temperature and salinity have mean values of 25 °C and 40‰, but with extreme values of 30 °C and 45‰ that occurred only at the enclosed intertidal areas, respectively. Their dissolved oxygen (DO) and pH were 6.5 mg/l and 8.3, respectively and the latter showing the highest values up to 8.5 in the intertidal areas dominated by the green cyanobacteria. These physicochemical conditions make the lagoon as a favorite place for the mangrove Avicennia marina, macro-algae, seagrasses (Halophila stipulacea and Cymodocea rotundata), and algal mats (Cyanobacteria) which dominate the intertidal and supratidal areas of the lagoon, tolerating extremely high-salinity and high-temperature conditions. On the other hand, corals were observed alive at the southern part of the lagoon, immediately south of the Al-Ultah Islet. Vertical profiles of temperature, salinity, and density in the lagoon’s water indicated that the water column consists of two layers throughout the year.

Introduced marine macroflora of Lebanon and its distribution on the Levantine coast

The marine macroflora introduced into Lebanon was studied through an analysis of historical data and field studies carried out since 1991. A total of 29 introduced species have been listed: 3 Chromobionta, 13 Rhodobionta, 12 Chlorobionta and 1 Streptobionta. Among them, Caulerpa taxifolia var. distichophylla, Spatoglossum variabile and Womersleyella setacea are recorded for the first time from Lebanon. Among them, Asparagopsis taxiformis, C. taxifolia var. distichophylla, Cladophora patentiramea, Codium arabicum, Codium parvulum, Galaxaura rugosa, Halophila stipulacea, Hypnea cornuta, Laurencia cf. chondrioides, Lophocladia lallemandii, Stypopodium schimperi, Ulva lactuca and Womersleyella setacea are potentially invasive species, and several of them already occupy extensive stretches of the Lebanese coast. The distribution of species on the Levantine coast, their dynamics and the current status of their populations are discussed.

Biosynthesis of metal nanoparticles using three marine plant species: anti-algal efficiencies against "Oscillatoria simplicissima".

This study aims at controlling of the cyanobacteria Oscillatoria simplicissima, those that produce neurotoxins and have negative impacts on the aquatic organisms, using biosynthesized metal nanoparticles (NPs). Silver-NPs (Ag-NPs) have been successfully biosynthesized using Nannochloropsis oculata and Tetraselmis tetrathele cultures. Also, Ag-NPs and iron oxide-NPs (Fe3O4-NPs) were synthesized by Halophila stipulacea aqueous extract. The structural composition of the different biosynthesized NPs was studied. The algae cultures and the extract were used as reductants of AgNO3, and brown colors due to Ag-NP biosynthesis were observed. Silver signals were recorded in their corresponding EDX spectra. FTIR analyses showed that proteins in N. oculata and T. tetrathele cultures reduced AgNO3, and aromatic compounds stabilized the biogenic Ag-NPs. H. stipulacea extract contains proteins and polyphenols that could be in charge for the reduction of silver and iron ions into nanoparticles and polysaccharides which stabilized the biosynthesized Ag-NPs and Fe3O4-NPs. The Ag-NPs biosynthesized by T. tetrathele cultures and H. stipulacea aqueous extract exerted outstanding negative impacts on O. simplicissima (optical density and total chlorophyll) and the Ag-NPs biosynthesized using N. oculata culture exerted the moderate performance. The study results suggest that the bioactive compounds present in the FTIR profiles of the Ag-NPs and or ionic silver may be the main contributors in their anti-algal effects. A trial to use the biosynthesized Fe3O4-NPs using H. stipulacea aqueous extract to separate Ag-NPs was successfully carried out. Since the synthesis and applications of nanomaterials is a hot subject of research, the study outcomes not only provide a green approach for the synthesis of metal-NPs but also open the way for more nanoparticle applications.

Ecophysiological Plasticity and Bacteriome Shift in the Seagrass Halophila stipulacea along a Depth Gradient in the Northern Red Sea.

Halophila stipulacea is a small tropical seagrass species. It is the dominant seagrass species in the Gulf of Aqaba (GoA; northern Red Sea), where it grows in both shallow and deep environments (1–50 m depth). Native to the Red Sea, Persian Gulf, and Indian Ocean, this species has invaded the Mediterranean and has recently established itself in the Caribbean Sea. Due to its invasive nature, there is growing interest to understand this species’ capacity to adapt to new conditions, which might be attributed to its ability to thrive in a broad range of ecological niches. In this study, a multidisciplinary approach was used to depict variations in morphology, biochemistry (pigment and phenol content) and epiphytic bacterial communities along a depth gradient (4–28 m) in the GoA. Along this gradient, H. stipulacea increased leaf area and pigment contents (Chlorophyll a and b, total Carotenoids), while total phenol contents were mostly uniform. H. stipulacea displayed a well conserved core bacteriome, as assessed by 454-pyrosequencing of 16S rRNA gene reads amplified from metagenomic DNA. The core bacteriome aboveground (leaves) and belowground (roots and rhizomes), was composed of more than 100 Operational Taxonomic Units (OTUs) representing 63 and 52% of the total community in each plant compartment, respectively, with a high incidence of the classes Alphaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria across all depths. Above and belowground communities were different and showed higher within-depth variability at the intermediate depths (9 and 18 m) than at the edges. Plant parts showed a clear influence in shaping the communities while depth showed a greater influence on the belowground communities. Overall, results highlighted a different ecological status of H. stipulacea at the edges of the gradient (4–28 m), where plants showed not only marked differences in morphology and biochemistry, but also the most distinct associated bacterial consortium. We demonstrated the pivotal role of morphology, biochemistry (pigment and phenol content), and epiphytic bacterial communities in helping plants to cope with environmental and ecological variations. The plant/holobiont capability to persist and adapt to environmental changes probably has an important role in its ecological resilience and invasiveness.

Continued Spread of the seagrass Halophila stipulacea in the Caribbean: Documentation in Puerto Rico and the British Virgin Islands

Continued Spread of the seagrass Halophila stipulacea in the Caribbean: Documentation in Puerto Rico and the British Virgin Islands