A Place Where the Eelgrass Flows

Seagrasses can form dense underwater meadows, some of which are large enough to be seen from space. Although they often receive little attention, they are one of the most productive ecosystems in the world. Seagrasses provide shelter and food to an incredibly diverse community of animals, from tiny invertebrates to large fish, crabs, turtles, marine mammals and birds. Seagrasses provide many important services to people as well, but many seagrasses meadows have been lost because of human activities. Work is ongoing around the world to restore these important ecosystems.

Even though seagrasses and seaweeds look superficially similar, they are very different organisms. Seagrasses belong to a group of plants called monocotyledons that include grasses, lilies and palms. Like their relatives, seagrasses have leaves, roots and veins, and produce flowers and seeds. Chloroplasts in their tissues use the sun's energy to convert carbon dioxide and water into sugar and oxygen for growth through the process of photosynthesis.

Veins transport nutrients and water throughout the plant, and have little air pockets called lacunae that help keep the leaves buoyant and exchange oxygen and carbon dioxide throughout the plant. Like other flowering plants, their roots can absorb nutrients.

Unlike flowering plants on land, however, they lack stomata—the tiny pores on leaves that open and close to control water and gas exchange. Instead, they have a thin cuticle layer, which allows gasses and nutrients to diffuse directly into and out of the leaves from the water. The roots and rhizomes thicker horizontal stems of seagrasses extend into the sediment of the seafloor and are used to store and absorb nutrients, as well as anchor the plants.

In contrast, seaweeds algae are much simpler organisms. They have no flowers or veins, and their holdfasts simply attach to the bottom and are generally not specialized to take in nutrients.

Associated Data

Scientists are studying what genes were lost and which were regained as seagrasses evolved from algae in the sea to plants on land, and then transitioned back to the sea. The entire genome of one seagrass, the eelgrass Zostera marina , was sequenced in , helping us understand how these plants adapted to life in the sea, how they may respond to climate warming, and the evolution of salt tolerance in crop plants.

Seagrasses grow in salty and brackish semi-salty waters around the world, typically along gently sloping, protected coastlines. Because they depend on light for photosynthesis, they are most commonly found in shallow depths where light levels are high. Many seagrass species live in depths of 3 to 9 feet 1 to 3 meters , but the deepest growing seagrass Halophila decipiens has been found at depths of feet 58 meters.

While most coastal regions are dominated by one or a few seagrass species, regions in the tropical waters of the Indian and western Pacific oceans have the highest seagrass diversity with as many as 14 species growing together. Antarctica is the only continent without seagrasses. Seagrasses grow both vertically and horizontally—their blades reach upwards and their roots down and sideways—to capture sunlight and nutrients from the water and sediment. They spread by two methods: Similar to grasses on land, seagrass shoots are connected underground by a network of large root-like structures called rhizomes.

The rhizomes can spread under the sediment and send up new shoots. When this happens, many stems within the same meadow can actually be part of the same plant and will have the same genetic code—which is why it is called clonal growth. In fact, the oldest known plant is a clone of the Mediterranean seagrass Posidonia oceanica , which may be up to , years old, dating back to the ice ages of the late Pleistocene.

Seagrasses reproduce sexually like terrestrial grasses, but pollination for seagrasses is completed with the help of water. Male seagrass flowers release pollen from structures called stamens into the water.

Seagrasses produce the longest pollen grains on the planet up to 5mm long compared to under 0. The clumps are moved by currents until they land on the pistil of a female flower and fertilization takes place. There is also evidence that small invertebrates, such as amphipods tiny shrimp-like crustaceans and polychaetes marine worms , feed on the pollen of one seagrass Thalassia testudinum , which could help to fertilize the flowers in a way similar to how insects pollinate flowers on land.

Self-pollination happens in some grass species, which can reduce genetic variation.

• A Place Where the Eelgrass Flows (Paperback).
• Breadcrumb.
• APPLES, APPLES, AND MORE APPLES.
• BEAUTY AND THE TOMCAT.
• Seagrass and Seagrass Beds | Smithsonian Ocean;
• a Place Where Eelgrass Flows Reed Poetry Xlibris Corporation Hard. 9781456820503;
• The Boys Book of Spycraft: How to be the Best Secret Agent Ever (Buster Books)?

Individual seagrass plants avoid this by producing only male or female flowers, or by producing the male and female flowers at different times. Just like land grasses, fertilized seagrass flowers develop seeds. Seagrass seeds are neutrally buoyant and can float many miles before they settle onto the soft seafloor and germinate to form a new plant. A few seagrass species such as the surfgrass Phylospadix can settle and live on rocky shores. Animals that eat seagrass seeds—including fish and turtles—may incidentally aid with their dispersal and germination if the seeds pass through their digestive tracks and remain viable.

The 72 species of seagrasses are commonly divided into four main groups: Zosteraceae, Hydrocharitaceae, Posidoniaceae and Cymodoceaceae. Their common names, like eelgrass, turtle grass, tape grass, shoal grass, and spoon grass, reflect their many shapes and sizes and roles in marine ecosystems. Seagrasses range from species with long flat blades that look like ribbons to fern or paddle-shaped leaves, cylindrical or spaghetti blades, or branching shoots.

The tallest seagrass species— Zostera caulescens —was found growing to 35 feet 7 meters in Japan. Some seagrass species are quick growing while others grow much more slowly. These distinct structures and growth forms affect how seagrasses influence their environment and what species live in the habitats they create.

Seagrasses are often called foundation plant species or ecosystem engineers because they modify their environments to create unique habitats.

These modifications not only make coastal habitats more suitable for the seagrasses themselves, but also have important effects on other animals and provide ecological functions and a variety of services for humans. Seagrasses have been used by humans for over 10, years. They've been used to fertilize fields, insulate houses, weave furniture, thatch roofs, make bandages, and fill mattresses and even car seats.

Our data show a dramatic the state of continual change, being built up in one increase of turbulence at the canopy-water interface place and broken down in another, but there is and within the canopy due to flow disruption by the dynamic equilibrium between these two processes'.

Turbulence is not only generated in the case Fonseca et al. Erosion of the beds can be due to wave and tidal action in 'weak' places Den Hartog or to high sedimentation rates and consequent burial of the Ecological implications plant. These environmental Frada-Orestano In contrast, organisms inhabiting seagrass far from being exhaustively described a n d understood.

This difference can be due to the physi- cally uniq. Thanks are due to the Director of the press. Equipment for this study and participa- Most of the experimental studies have focused on the tion of the 2 co-authors A. Current flow around Zostera marina reducing shear stress at the bottom, enhancing fine plants and flowers: Mechanistic implications for pollina- favonng a larger number of species and individuals. Seagrasses baffling the current and acting as 'sediment Importance of local changes in fishes as well Eckman , Butman On the other hand, turbulence, increas- Blols, J.

C , Frabcaz, J. Observations sur les herbiers a zosteres de la region d e ing within the canopy, can augment residence time of Roscoff Cah. Systematics and ecology of the hydroid resuspend deposited seston, as observed with animal population on two Posidonla oceanica meadows.

Algal undergrowth of Posidonia reduction on filter-feeding activity, as hypothesized by oceanica beds in the Gulf of Naples: Growth rates and Boudouresque, C. Un nouveau type d'herbier a Posidonia oceanica: Shoot density, distance into the Butman, C. Larval settlement of soft-sediment meadow from the bed edge and ambient current invertebrates: L'herbier a Posidonia In conclusion, Zostera marina plants interact strongly oceanica des c6tes siciliennes: Workshop o n Posidonia oceanica hydrodynamic drag a n d generating turbulence via flow beds.

Gis Posidonie, Marseille, p. Current and flux reduction, shear stress at Carey, D. Particle resuspension in the benthic the canopy level and turbulence intensity are positively boundary layer induced by flow around polychaete tubes. Scardi, M,, Mazzella, L. Structure of epiphytic community of Posidonia oceanica leaves in a most of the mechanisms often invoked 'intuitively' to shallow meadow. Rernarque sur la morphologie et la organisms in eelgrass meadows. Workshop on Posidonia ocean- gache.

You are here:

Stn mar Endoume; Suppl. The influence of Cionco, R. On the coupling of canopy flow to marine bottom communities on the depositional environ- ambient flow for a variety of vegetation types and ment of sediments. Boundary Layer Meteorology The dynamic aspect in the ecology of of habitat complexity, competition and predation in struc- seagrass communities. Structure, function and classification in assemblages.

Estuarine perspec- seagrass communities. Academic Press, New York, p. Marine Sci- Hill, P. S , Nowell, A. Flume evalu- ence 4. Photosynthetic respon- concentration and excess boundary shear stress. Effect of a kelp forest on Dennison, W. Role of daily light coastal currents. Jeudy de Grissac, A Effects des herbiers a Mar Ecol.

Effect of water motion sedimentologie littorale. Gis Posidonie, Mar- Eckman, J. Hydrodynamic processes affecting seille, p. Faunal relationships in temperate seagrass Eckman, J. The role of hydrodynamics in recruit- beds. Handbook of ment, growth and survival of Argopecten irradians L. Garland Anomia sirnplex D'Orblgny within eelgrass meadows. Consumer ecology of seagrass Eckman, J.

Boundary skin friction beds. Seagrass ecosys- and sediment transport about a n animal tube mimic. A comparison of canopy Koehl, M. Flow, flapping, and friction and sediment movement between four species of photosynthesis of Nereocystis leutkeana: Feeding currents and particle capture Two levels were used in the treatments: Lbbb or 2 boxes two patches; e. Physical scenario Experimental approach where physical structures of mimics were the main factor responsible for the changes in food availability within the canopy e.

Biological scenario Experimental approach where physical structures of mimics plus the presence of high densities of filter feeders were the main factors responsible for the changes in food availability within the canopy e. Tree diagram showing the relationships among all the measured factors. Cockles sampling The filter feeder cockle Cerastoderma edule was chosen due to its abundance and reliable behavior as model organism [12] , [48] , [49]. Water chlorophyll measurements in the racetrack flume Three water samples 1 L per sample were taken: Statistics analysis Significant differences in hydrodynamic parameters i.

The graduated grey shading outlines the extent of the patch canopies. Significant differences are shown in bold. L, low shoot density; H, high shoot density and b, bare sediment. Water chlorophyll a content. Mean chlorophyll stomach content of the cockles along the racetrack flume for different treatments and scenarios. Discussion This work provides the first quantitative evidence that food availability to filter feeders is modulated by seagrass patch complexity i.

Interaction between mimics and flow In agreement with previous studies [33] , [34] , [45] , [46] , [54] , our results showed the development of a turbulent patch—wake behind the forefront patch, an increase of TKE at the edges of the patch and a gradual reduction of the velocity within the seagrass canopy. Resource concentration balance Even though turbulence increased at the patch edges of the high shoot density treatment i. Filter feeder food intake rate Cockle FIR was higher in all seagrass treatments than in control ones i. Ecological relevance This work showed that food availability in seagrass meadows is the outcome of a complex interaction between hydrodynamic forces and habitat complexity together with intra-specific competition consumption and bio-mixing.

Conceptual model showing the effects of filter feeders and shoot density on resource availability and concentration. Data Availability The authors confirm that all data underlying the findings are fully available without restriction. Fonseca MS, Fisher JS A comparison of canopy friction and sediment movement between four species of seagrass with reference to their ecology and restoration.

Mar Ecol Prog Ser Trends Ecol Evol 9 5 — Trends Ecol Evol Wilson DM The effect of submerged vegetation on the growth and the incidence of siphon nipping and incidence of siphon nipping of the northern quahog, Mercenaria mercenaria Bivalvia , The University of Alabama at Tuscaloosa. Oecologia 87 3 — Irlandi EA The effects of seagrass patch size and energy regime on growth of a suspension-feeding bivalve. J Mar Res 54 1 — J Exp Mar Biol Ecol 1 21— Allen BJ, Williams SL Native eelgrass Zostera marina controls growth and reproduction of an invasive mussel through food limitation.

Helgoland Mar Res Can it be kept sustainable? J Sea Res 63 2 — Mar Ecol Prog Ser 1 — J Environ Manage 53 2 — Helgoland Mar Res 56 1 3— Danovaro R, Fabiano M Seasonal changes in quality and quantity of food available for benthic suspension-feeders in the Golfo Marconi North-western Mediterranean. Est Coast Shelf Sci 44 6 — Wildish D, Kristmanson D Benthic suspension feeders and flow. Arkema KK Flow-mediated feeding in the field: J Exp Mar Biol Ecol 1 45— Can J Fish Aquat Sci 42 6 — Muschenheim DK The dynamics of near-bed seston flux and suspension-feeding benthos.

J Mar Res 45 2 — J Exp Mar Biol Ecol 3 — J Exp Mar Biol Ecol 2 — J Exp Mar Biol Ecol 1 65— Limnol Oceanogr 39 7 — Zostera japonica dwarf eelgrass facilitates itself and reduces condition of Ruditapes philippinarum Manila clam on intertidal flats. Mar Bio 9 — Spatially explicit effects on ammonium uptake rates. Limnol Oceanogr 53 4 — Est Coast Shelf Sci 35 6 — Mar Ecol Progr Ser 6: Biology, ecology and conservation. PloS one 8 5 e doi: Sobral P, Widdows J Effects of increasing current velocity, turbidity and particle-size selection on the feeding activity and scope for growth of Ruditapes decussatus from Ria Formosa, southern Portugal.

J Exp Mar Biol Ecol 1 — Widdows J, Brinsley M Impact of biotic and abiotic processes on sediment dynamics and the consequences to the structure and functioning of the intertidal zone. J Sea Res 48 2 — Am Nat 2 — Ecology 85 11 — Mar Freshw Res 61 2 — Ecology 91 7 — Ecology 86 8 — Est Coast Shelf Sci Mar Ecol Prog Ser 97 2 — In situ measurements and numerical modeling of bivalve filtration in the boundary layer. Limnol Oceanogr 50 6 — Hydrobiologia 1—3 — Results from technique to collect suspended food resources.

Ritchie RJ Universal chlorophyll equations for estimating chlorophylls a, b, c, and d and total chlorophylls in natural assemblages of photosynthetic organisms using acetone, methanol, or ethanol solvents. Photosynthetica 46 1 —