Seagrass

By:Christian Jay Rayon Nob

BS-Marine BiologyMindanao Sate University-Naawan Campus

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What is seagrass? An angiosperm, also known as a flowering plant (most widespread group of land plants)Lives in an estuarine or marine environment (saline, not freshwater!) Anchors with roots and rhizomes Pollinates and produces seeds underwater From 1 of 12 genera: Zostera, Phyllospadix, Heterozostera, Posidonia, Halodule, Cymodocea,Syringodium, Thalassodendron, Amphibolis, Enhalus, Thalassia, and Halophila. Seagrasses live in the coastal waters of most of the worlds’ continents. They are the main diet of dugongs and green turtles and provide a habitat for many, smaller marine animals, some of which, like prawns and fish, are commercially important. They also absorb nutrients from coastal run-off and stabilise sediment, helping to keep the water clear. Seagrasses are unique amongst flowering plants, in that all but one genus can live entirely immersed in seawater. Enhalus plants are the exception, as they must emerge to the surface to reproduce; all others can flower and be pollinated under water. Adaptation to a marine environment imposes major constraints on morphology and structure. The restriction of seagrasses to seawater has obviously influenced their geographic distribution and speciation. Seagrass can reproduce through sexual or asexual methods. In sexual reproduction, the plants produce flowers and transfer pollen from the male flower to the ovary of the female flower. Most seagrass species produce flowers of a single sex on each individual, so there are separate male and female plants.

PHILIPPINES SEAGRASS ECOSYSTEM 

Seagrass beds - are found in waters and at depths where light can easily penetrate because they require sunlight to photosynthesize. They can be found deeper waters where it is clear but are generally in shallow waters up to three meters in depth. Seagrasses can often be found as an intermediary ecosystem between coral reefs ecosystem and mangrove ecosystem where they play an important role.

SEAGRASS SPECIES: DETRITUS

There are 16 known species of seagrasses in the Philippines, second only to Australia with 17 species out of the 50 total seagrasses found throughout the world. Seagrass beds are highly productive and most of the organisms that are found in this ecosystem make use of the massive amount of detritus (decomposing materials) for their sustenance. In the Philippines seagrasses are known to support 172 species of fish, 46 species of invertebrates, 51 species of seaweeds, one (1) species of turtle and one (1) species of dugong. Some of the well known and commercially important organisms found here include sea urchins (tuyom), sea cucumbers (bat), and rabbitfish (danggit) to name a few. 

NEED PROTECTIONS 

Since seagrasses are so important they should certainly be protected like other coastal ecosystems. It is important to identify and map important seagrass areas so that they can be properly managed. Once this delineation is completed managers can make policies to protect these areas such as establishing sanctuaries and regulations on activities such as fishing, dredging and land reclamation in certain areas.BENEFITS&THREATS

Seagrasses are an important refuge and nursery for many economically important fish and other marine organisms as well. Another very important benefit of seagrasses is the fact that they serve as sediment traps and prevent excessive land-based siltation from reaching and smothering coral reefs.

Why conserve seagrass?

The habitat complexity within seagrass meadows enhances the diversity and abundance of animals. Seagrasses on reef flats and near estuaries are also nutrient sinks, buffering or filtering nutrient and chemical inputs to the marine environment. They also stabilise coastal sediments.

They also provide food and shelter for many organisms, and are a nursery ground for commercially important prawn and fish species. The high primary production rates of seagrasses are closely linked to the high production rates of associated fisheries. These plants support numerous herbivore- and detritivore-based food chains, and are considered very productive pastures of the sea. The associated economic values of seagrass meadows are very large, although not always easy to quantify.

Seagrass/algae beds are rated the 3rd most valuable ecosystem globally (on a per hectare basis), only preceded by estuaries and wetlands. The average global value of seagrasses for their nutrient cycling services and the raw product they provide has been estimated at 1994US$ 19,004 ha-1 yr-1 (Costanza et al. 1997). This value would be significantly greater if the habitat/refugia and food production services of seagrasses were included.

1.)History in Systematics of Seagrass

Since the time of the dinosaurs, three groups of flowering plants (angiosperms) colonised the oceans. Known as ‘seagrasses’, they are the only flowering plants that can live underwater. More closely related to terrestrial lilies and gingers than to true grasses, they grow in sediment on the sea floor with erect, elongate leaves and a buried root-like structure (rhizome). The family Scaridae comprises about 90 species of herbivorous coral reef, rock reef, and seagrass fishes. Parrotfishes are important agents of marine bioerosion who rework the substrate with their beaklike oral jaws. Many scarid populations are characterized by complex social systems including highly differentiated sexual stages, terri-toriality, and the defense of harems. Here, we test a hypothesis of relationships among parrotfish genera derived from nearly 2 kb of nuclear and mitochondrial DNA sequence. The DNA tree is different than a phylogeny based on comparative morphology and leads to important reinterpretations of scarid evolution. The molecular data suggest a split among seagrass and coral reef associated genera with nearly 80% of all species in the coral reef clade. Our phylogenetic results imply an East Tethyan origin of the family and the recurrent evolution of excavating and scraping feeding modes. It is likely that ecomorphological differences played a significant role in the initial divergence of major scarid lineages, but that variation in color and breeding behavior has triggered subsequent diversification. We present a two-phase model of parrotfish . evolution to explain patterns of comparative diversity. Finally, we discuss the application of this model to other adaptively radiating clades.:

Seagrasses are the structural species of one of the most important coastal

ecosystems worldwide and support high levels of biodiversity and biomass

production. Posidonia is one of the most ancient seagrass genera and displays a

contrasting disjunct biogeographic pattern. It contains one single species in the

Northern Hemisphere, P. oceanica, which is endemic to the Mediterranean Sea, and

has up to 8 recognized taxa in the Southern Hemisphere, which in Australia are

divided into 2 complexes, P. ostenfeldii and P. australis. A phylogeny based on a

nuclear marker (rRNA-ITS) revealed an ancient split between the northern (i.e.

Mediterranean) and southern (i.e. Australian) taxa, followed by a separation of the 2

recognized Australian complexes. However, the species belonging to the P.

ostenfeldiicomplex were indistinguishable, suggesting an ecotypic origin or a recent

speciation. Therefore, among the 7 morphologically described Australian species only

4 species lineages can be discriminated. The organelle markersnad7 intron, trnL–F

and matK/trnK intron were not informative for reconstructing the phylogeny of this

genus, and the mitochondrial markers exhibited a strikingly slow evolutionary rate

relative to other genome regions.

1.1 Biodiversity of Sea grass Biodiversity at multiple levels -genotypes within species, species within

functional groups, habitats within a landscape- enhances productivity, resource use, and stability of seagrass ecosystems. Several themes emerge from a review of the mostly indirect evidence and the few experiments that explicitly manipulated diversity in seagrass systems. First, because many seagrass communities are dominated by 1 or a few plant species, genetic and phenotypic diversity within such foundation species has important influences on ecosystem productivity and stability. Second, in seagrass beds and many other aquatic systems, consumer control is strong, extinction is biased toward large body size and high trophic levels, and thus human impacts are often mediated by interactions of changing 'vertical diversity' (food chain length) with changing 'horizontal diversity' (heterogeneity within trophic levels). Third, the openness of marine systems means that ecosystem structure and processes often depend on interactions among habitats within a landscape (landscape diversity). There is clear evidence from seagrass systems that advection of resources and active movement of consumers among adjacent habitats influence nutrient fluxes, trophic transfer, fishery production, and species diversity. Future investigations of biodiversity effects on processes within seagrass and other aquatic ecosystems would benefit from broadening the concept of biodiversity to encompass the hierarchy of genetic through landscape diversity, focusing on links between diversity and trophic interactions, and on links between regional diversity, local diversity, and ecosystem processes. Maintaining biodiversity and biocomplexity of seagrass and other coastal ecosystems has important conservation and management implications.

Map of Sea grass

Different kinds of Sea grass

1.2 Terms in the Systematic of Sea grass:

The major function BLADES is photosynthesis, but they also function in nutrient absorption and in elimination of waste products.The 

SHORT SHOOT can be thought of as the "stem" of the plant, where the blades originate.

RHIZOMES are subterranean organs that function in propagation of the clone, in anchoring the plants to the substrate, in translocation of materials throughout the clone, and are also involved in nutrient absorption and gas exchange. Short shoots and roots emanate from the rhizomes.

ROOTS are much thinner than rhizomes and function primarily in nutrient absorption. They also contribute to anchorage of the plant and to the elimination of waste products.

2.) Evolutionary trees & roots

Dichotomous keyDefinition: A tool used in plant or animal identification. The dichotomous key is a series of questions, and each question is a choice between two characteristics. The identity of an organism is determined through the process of eliminating characteristics that do not apply to it.

Vegetative Key

Plants with flat leaf blades ...................................... 1

Plants with round or cylindrical leaf blades ...................... Syringodium

filiforme (syn: Cymodocea filiformis)

la. Leaves paddle shaped, each associatedwith 2 scales at the base ....................................2. Halophila specieslb. Leaves in a pseudowhorl, each with 2 scales at the base and two scales halfway up the petiole or leaf stem .......................... 3. Halophila engelmannii

1c. Leaves strap-like or at least linear .......................... 42. Leaves rounded, generally oval in shape, secondary veinsat an angle greater than 45 degrees, leaf marginswith minute serrations; annuals from seeds ..................... Halophila decipiens Pictures of Halophila decipiens

2. Leaves with a pointed tip, secondary veins approximately 45 degrees or

less,

elongated, entire; perennials .................................. Halophila johnsonii

4. Leaf blades generally less than 3 mm in width .................. 5

5. Leaves clustered from a distinct node on a rhizome,

leaf tip is truncated .......................................... Halodule wrightii

5. Leaves, threadlike from a branched stem,

leaf tip is pointed, can be found in active growth

throughout the year ............................................ Ruppia maritima

Anatomy of sea grass

2.1Characters of Sea grass

Seagrass meadows are conspicuous and wide spread in theshallow marine

amount of organic matter and serving as a good substratum for a variety of

epiphytic algae including diatoms (Smith, 1991) and sessile fauna. As

mangrove and coral reef ecosystems are closely associated with the seagrass

ecosystem, there is a lot of export of organic matter and nutrients form the

latter. Seagrass meadows are highly productive and dynamic ecosystems,

which rank among the most productive ecosystems of the oceans (McRoy and

McMillan, 1977; Hillman et al.,1989).

 Higher primary production rates of seagrasses are closely linked

to the higher production rates of associated fisheries and thus the seagrass

communities make significant contributions to the coastal productivity. Several

reports indicate that seagrass biomass is the prime factor influencing the

organization of marine macrofaunal communities. They also control the habitat

complexity, species diversity and abundance of associated invertebrates and

thereby shaping the structure of the marine communities

• Regatta Lady Sea grass Sandal

• SALE - Unisex Sea grass Mesh Beanie (239)

2.2 Evaluation of trees sequence comparisons among genes codifying for the RNA component of the small ribosomal subunit (16S rRNA or 18S rRNA) in cellular organisms have been largely used to reconstruct their phylogenies, and hence the identification of taxa by means of a molecular approach. Furthermore, the direct DNA isolation from environmental samples and the PCR amplification of the pool of rRNA genes with the subsequent cloning and sequencing have opened the door to the description of naturally occurring microbial communities independently from any culturing technique or morphological identification. These studies have unveiled an enormous hidden diversity in a wide variety of microbial communities. Our main objective was to evaluate the usefulness of the 18S rRNA gene clone libraries to describe the structure of the macroeukaryotic leaf-epiphytic assemblage of the seagrass Posidonia oceanica, and monitor the changes occurring in different stages of its seasonal succession (winter, spring and summer). To that end, we compared the results of these libraries with those provided by classical microscopy techniques. Among both approaches, the screening of clone libraries rendered the highest number of distinct units named operational phylogenetic units. However, diversity estimates provided by both methods were comparable and rendered the highest Shannon Diversity Index (H′) at the end of the succession. The major discrepancies were on the different occurrence of some groups. For example, macroalgae were the most frequent epiphytes counted by microscopy, whereas metazoa (specially, bryozoa) dominated the clone libraries. Altogether the results indicate that clone libraries constitute an excellent complementary approach to classical microscopy methods. To the best of our knowledge, this is the first attempt to describe a marine macroeukaryotic community using a molecular approach such as the analysis of 18S rRNA gene clone libraries.

3.) Molecular Systematic of Sea grass Relationships among members of the seagrass genus Halophila (Hydrocharitaceae) were investigated using phylogenetic analysis of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA. The final aligned ITS sequence data set of 705 base pairs from 36 samples in 11 currently recognised species included 18.7% parsimony informative characters. Phylogenetic analysis yielded two most parsimonious trees with strong support for six groups within the genus. Evolutionary trends in Halophila appear to be toward a more reduced simple phyllotaxy. In addition, this study indicates that long distance 'jump' dispersal between major ocean systems may have occurred at least in the globally distributed H. decipiens. Results of ITS analyses also indicate that the wide-spread pacific species H. ovalis is paraphyletic and may contain cryptic species. Likewise, the geographically restricted species H. hawaiiana and H. johnsonii could not be distinguished from H. ovalis with these data and warrant further investigation. Previous taxonomic treatments of the family Zosteraceae in Australia/ New Zealand have recognizedHeter-ozostera tasmanica (monotypic) and four Zostera species all belonging to subgenus Zosterella Z. capricorni Z. muelleri Z.mucronata Z. novazelandica Zostera has always been taxonomically problematic in Australia, where researchers have expresseddifficulty with species recognition due to vague or inconsistent morphological characters. There also has been a lack of agreement on generic (notably the distinctness of Heterozostera) and subgenericdelimitation. Recent anatomical, develop-mental, and molecular studies urge a reevaluation of relationships in the family. To clarify the taxonomy of Zosteraceae,weinvestigated interspecificphylogenetic relationships focusing on Australian species of subgenus Zosterella. We examinedmaterial comprising all genera of Zosteraceae ( Heterozostera Nanozostera Phyllospadix Zostera), six/ seven species of ZosteraSubgenus Zosterella.

3.1 Historical Context Populations of the temperate seagrass, Zostera marina L. (eelgrass), often exist as discontinuous beds in estuaries, harbors, and bays where they can reproduce sexually or vegetatively through clonal propagation. We examined the genetic structure of three geographically and morphologically distinct populations from central California (Elkhorn Slough, Tomales Bay, and Del Monte Beach), using multilocus restriction fragment length polymorphisms (DNA fingerprints). Within-population genetic similarity (Sw) values for the three eelgrass populations ranged from 0.44 to 0.68. The Tomales Bay population located in an undisturbed, littoral site possessed a within-population genetic similarity (Sw = 0.44) that was significantly lower than those of the other two populations. Cluster analysis identified genetic substructure in only the undisturbed subtidal population (Del Monte Beach). Between-population similarity values (Sb) for all pairwise comparisons ranged from 0.47 to 0.51. The three eelgrass populations show significantly less between locale genetic similarity than found within populations, indicating that gene flow is restricted between locales even though two of the populations are separated by only 30 km. The study demonstrates that (i) natural populations of Z. marina from both disturbed and undisturbed habitats possess high genetic diversity and are not primarily clonal, (ii) gene flow is restricted even between populations in close proximity, (iii) an intertidal population from a highly disturbed habital shows much lower genetic diversity than an intertidal population from an undisturbed site, and (iv) DNA fingerprinting techniques can be exploited to understand gene flow and population genetic structure in Z. marina, a widespread and ecologically important species, and as such are relevant to the management of this coastal resource.

3.2 Basic Techniques Subtidal seagrass habitats are prime candidates for the application of principles derived from landscape ecology. Although seagrass systems are relatively simple compared to their terrestrial counterparts in terms of species diversity and structural complexity, seagrasses do display variation in spatial patterns over a variety of scales. The presence of a moving water layer and its influence on faunal dispersal may be a distinguishing feature impacting ecological processes in the subtidal zone. Studying seagrass-dominated landscapes may provide a novel approach to investigating questions regarding self-similarity of spatial patterns, and offers a new perspective for analysing habitat change in a variety of marine environments.

Seagrass beds can be restored by encouraging natural recolonization in areas that have experienced improvements in surface water quality. Proactive methods of eelgrass restoration include transplanting of individuals taken from healthy donor beds or seedlings reared under laboratory conditions. In some cases seeds can be planted or broadcast. Seeding can be used alone, or in concert with transplant techniques. Several technical guidance documents have been published to assist restoration practitioners in selecting transplant sites, and in choosing appropriate restoration methods for eelgrass beds.

This approach to eelgrass restoration focuses on water quality improvement in the study area with the assumption that once suitable conditions are established, seagrass will naturally re-colonize. This approach involves a long-term coordinated effort to upgrade municipal sewage systems, and a program to identify and curtail point and non-point discharges from industrial, residential and agricultural areas in the coastal zone.

3.3 Impact on phylogenetics seagrasses—a unique group of flowering plants that have adapted to exist fully submersed in the sea—profoundly influence the physical, chemical, and biological environments in coastal waters, acting as ecological engineers(sensuWright and Jones 2006) and providing numerous important ecological services to the marine environment(Costanza et al. 1997). Seagrasses alter water flow, nutrient cycling, and food web structure (Hemminga and Duarte 2000).They are an important food source for megaherbivores such as green sea turtles, dugongs, and manatees, and providecritical habitat for many animals, including commercially and recreationally important fishery species (figure 1; Becket al. 2001). They also stabilize sediments and produce large quantities of organic carbon. However, seagrasses and these associated ecosystem services are under direct threat from a host of anthropogenic influences. Seagrasses are distributed across the globe (figure 2), but unlike other taxonomic groups with worldwide distribution, they exhibit low taxonomic diversity (approximately 60 species worldwide, compared with approximately 250,000 terrestrial angiosperms). The three independent lineages of seagrass (Hydrocharitaceae, Cymodoceaceae complex, and Zosteraceae) evolved from a single lineage of monocotyledonous flowering plants between 70 million and 100 million years ago (figure 3a; Les et al. 1997).

Development of a DNA Barcoding System for Seagrasses: Successful but Not Simple Seagrasses, a unique group of submerged flowering plants, profoundly influence the physical, chemical and biological environments of coastal waters through their high primary productivity and nutrient recycling ability. They provide habitat for aquatic life, alter water flow, stabilize the ground and mitigate the impact of nutrient pollution. at the coast region. Although on a global scale seagrasses represent less than 0.1% of the angiosperm taxa, the taxonomical ambiguity in delineating seagrass species is high. Thus, the taxonomy of several genera is unsolved. While seagrasses are capable of performing both, sexual and asexual reproduction, vegetative reproduction is common and sexual progenies are always short lived and epimeral in nature. This makes species differentiation often difficult, especially for non-taxonomists since the flower as a distinct morphological trait is missing. Our goal is to develop a DNA barcoding system assisting also non-taxonomists to identify regional seagrass species. The results will be corroborated by publicly available sequence data. The main focus is on the 14 described seagrass species of India, supplemented with seagrasses from temperate regions. According to the recommendations of the Consortium for the Barcoding of Life (CBOL) rbcL and matKwere used in this study. After optimization of the DNA extraction method from preserved seagrass material, the respective sequences were amplified from all species analyzed. Tree- and character-based approaches demonstrate that

the rbcL sequence fragment is capable of resolving up to family and genus level. Only matK sequences were reliable in resolving species and partially the ecotype level. Additionally, a plastidic gene spacer was included in the analysis to confirm the identification level. Although the analysis of these three loci solved several nodes, a few complexes remained unsolved, even when constructing a combined tree for all three loci. Our approaches contribute to the understanding of the morphological plasticity of seagrasses versus genetic differentiation.

Seagrasses are higher plants capable to complete their life cycle under submerged conditions in the marine environment [1]. They evolved independently at least three times between 75 and 17 million years ago [2]–[4]; hence, seagrasses form a paraphyletic group including four core families (Cymodoceaceae, Hydrocharitaceae, Posidoniaceae, and Zosteraceae). These marine plants cover large geographic ranges worldwide [5], surviving most diverse environmental conditions. They have fundamental roles in the ecology of coastal areas, e.g. as breeding and nursery ground for a variety of marine organisms, coastal stabilizers or coast protectors next to coral reefs and mangroves. Decline in seagrass species and cover were observed throughout the world and the recent estimates indicate that these resources are gradually disappearing at the rate of 110 km2 yr−1 since 1980 [6]. Main factors for the loss of seagrasses are eutrophication and high turbidity due to natural and human influences. Furthermore seagrasses contain highly valuable secondary compounds such as phenolic acids used for traditional medicine and biotechnological purposes (e.g. rosmarinic acid as antioxidant or zosteric acid as an effective antifouling agent).

3.4Limitation of molecular phylogenetics Mediterranean populations of the seagrass Posidonia oceanic;

Posidonia oceanica is an endemic Mediterranean seagrass species

that has often been assumed to contain low levels of genetic

diversity. Random amplified polymorfic DNA (RAPD) markers were

used to assess genetic diversity among five populations from three

geographical regions (north, central, and south) of the western

Mediterranean Sea. Stranded germinating seeds from one of the

central populations were also included in the analysis. Forty-one

putative genets were identified among 76 ramets based on 28 RAPD

markers. Genotypic diversity strongly depended on the spatial

structure, age, and maturity of the meadows. The lowest clonal

diversity was found in the less structured and youngest prairies.

Conversely, a high genotypic diversity was found in the highly

structured meadows. The genotypic diversity in these meadows was

at the same level as in P. australis and higher than previously

reported data for P. oceanica populations in the Tyrrhenian Sea near

the coast of Italy.

Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica he maximum size and age that clonal organisms can reach remains poorly known, although we do know that the largest natural clones can extend over hundreds or thousands of metres and potentially live for centuries. We made a review of findings to date, which reveal that the maximum clone age and size estimates reported in the literature are typically limited by the scale of sampling, and may grossly underestimate the maximum age and size of clonal organisms. A case study presented here shows the occurrence of clones of slow-growing marine angiosperm Posidonia oceanica at spatial scales ranging from metres to hundreds of kilometres, using microsatellites on 1544 sampling units from a total of 40 locations across the Mediterranean Sea. This analysis revealed the presence, with a prevalence of 3.5 to 8.9%, of very large clones spreading over one to several (up to 15) kilometres at the different locations. Using estimates from field studies and models of the clonal growth of P. oceanica, we estimated these large clones to be hundreds to thousands of years old, suggesting the evolution of general purpose genotypes with large phenotypic plasticity in this species. These results, obtained combining genetics, demography and model-based calculations, question present knowledge and understanding of the spreading capacity and life span of plant clones. These findings call for further research on these life history traits associated with clonality, considering their possible ecological and evolutionary implications

4.)Case studies to illustrate molecular/morphological phylogenetics

Chloroplast tRNALeu (UAA) intron sequences provide phylogenetic resolution of seagrass relationships Recent molecular studies have indicated that seagrasses comprise three convergent angiosperm clades. Although seagrass polyphyly has been demonstrated persuasively, other details of their phylogenetic relationships remain uncertain or weakly supported. To further assess seagrass relationships, we explored the potential of chloroplast trnL (UAA) intron sequences for phylogenetic reconstruction in the Alismatidae. Sequence analysis revealed considerable length variation of the trnL intron among the eight species of the subclass Alismatidae examined. These regions (representing large insertions/deletions in loops) were difficult to align and too variable to use reliably in phylogenetic analysis. However, conserved regions of the intron were readily aligned and were characterized by levels of divergence comparable to coding rbcL sequences. When analyzed phylogenetically, conserved trnL intron sequences recovered the same phylogenetic relationships among seagrass clades that were obtained using rbcL data. Combined analysis oftrnL intron and rbcL coding sequences yielded a single most parsimonious tree with levels of nodal support higher than those obtained independently for either of the datasets. Analyses of conserved intron and coding chloroplast DNA sequences provide continued support for the polyphyly of seagrasses, the monophyly of Zosteraceae and a clade comprising Ruppiaceae, Posidoniaceae and Cymodoceaceae. Conserved trnL intron should be useful for evaluating other phylogenetic relationships in subclass Alismatidae.

Contribution of genetics and genomics to seagrass biology and conservation Genetic diversity is one of three forms of biodiversity recognized by the IUCN as deserving conservation along with species and ecosystems. Seagrasses provide all three levels in one. This review addresses the latest advances in our understanding of seagrass population genetics and genomics within the wider context of ecology and conservation. Case studies are used from the most widely studied, northern hemisphere species Zostera marina, Z. noltii, Posidonia oceanica and Cymodocea nodosa. We begin with an analysis of the factors that have shaped population structure across a range of spatial and temporal scales including basin-level phylogeography, landscape-scale connectivity studies, and finally, local-scale analyses at the meadow level—including the effects of diversity, clonality and mating system. Genetic diversity and clonal architecture of seagrass meadows differ within and among species at virtually all scales studied. Recent experimental studies that have manipulated seagrass genetic biodiversity indicate that genotypic diversity matters in an immediate ecological context, and enhances population growth, resistance and resilience to perturbation, with positive effects on abundance and diversity of the larger community. In terms of the longer term, evolutionary consequences of genetic/genotypic diversity in seagrass beds, our knowledge remains meagre. It is here that the new tools of ecogenomics will assist in unravelling the genetic basis for adaptation to both biotic and abiotic change. Gene expression studies will further assist in the assessment of physiological performance which may provide an early warning system under complex disturbance regimes that seagrasses are at or near their tolerance thresholds.At the most fundamental level, ecological interactions of seagrasses with their environment depends on the genetic architecture and response diversity underlying critical traits. Hence, given the rapid progress in data acquisition and analysis, we predict an increasing role of genetic and genomic tools for seagrass ecology and conservation.

5.) Conclusion

The sea grass resoureces in the intertidal areas.a total of six

species of seagrass were found and identified in the Philippines: the

Thalassia hemprichii (dugong grass), Enhalus acocoides (Tropical eel

grass), Cymodocea rotundata (round tipped seagrass), Syringodium

isoetifolium (syring grass), Halophila ovalis (spoon grass), and Halodule

pinifolia (fiber-strand grass).this seagrass are very important in our

environment areas.also they are the habitat of the aquatic life.so us a

human being we are going to protect our seagrass and our marine

environment.we are the one who benefits this marine areas because

our food came from this marine areas just like. Fish, sea urchin, sea

cucumber and ect………….

7.) References

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AppendicesAll the images are indexed as thumbnails. To view a larger image, just click on the thumbnail. A new window will open up to display the image.

A bald eagle rests on seagrass beds exposed by low tide.

Green turtles graze upon turtle grass (Thalassia testudinum

A Bahamian sea star imeadow of turtle grass.

Sea urchins on turtle grass.

Bonnethead shark swimming over seagrasses.

Turtle grass

Shoal grass (Halodule wrightii)

Star grass (Halophila engelmannii)

Johnson'sseagrass (Halophilajohnsonii)

Manatee grass (Syringodium filiforme)

This dwarf seahorse blends effectively along a bed of macroalgae and holding onto a blade of manatee grass.

A yellow spotted sting ray hides in turtle grass.

Scallops are an important recreational species that relies on seagrasses.

Sponges and manatee grass.

Despite heavy algal growth, a French angel and jackknife shelter in a seagrass bed.

When the root systems are broken and there is a depression greater than 20 cm, the scar needs to be filled in.

Measuring seagrass blades within a quadrat.

Shallow seagrass scars can often be restored by placing bird stakes along the scars to recruit birds.

Measuring the depth of a propeller scar helps managers determine the best type of restoration.

A close-up view of seagrass blades in the quadrat.