Academic literature on the topic 'Sea grass meadows'

This study investigates the status and anthropogenic pressures on seagrass ecosystem. Urbanization and tourism in the coastal areas of Bintan, Indonesia were increasing in the recent years. They have become new pressures to intertidal ecosystem and habitats, particularly seagrass ecosystem. Seagrass meadows are the important ecosystem and habitats in Bintan region. They provide a wide range of ecosystem services, including for small-scale fisheries and have being Dugongs (Dugong dugon) habitats for food. Currently, the sea grass status is less healthy or damaged with 11 species. The anthropogenic disturbance processes have affected the spatial distribution, percent coverage, biodiversity, and community structure of sea grass. Moreover, several species are hard to find. Directly, sea grass meadows are impacted by introduced coastal development (i.e. settlement area, tourism accommodation, port, etc.), land-based pollution, reclamation, boating traffic, dredging activities and tourism activities. Sea grass conservation area and marine spatial planning based on the land- and seascape connectivity is important for conservation efforts and sustainable management of sea grass.

Although the anthropogenic impact on Posidonia oceanica meadows in the Mediterranean Sea has been studied over the last few decades, the data about the status of this endemic magnoliophyte are scarcer from the Adriatic Sea. Samples of P. oceanica meadows were collected in June and July 2004 using SCUBA diving at 8 sites in the area of the Dugi Otok Island, all at depths of 10 m. The meadow's shoot density was measured, and shoots were collected to be examined and compared through number of leaves per shoot, leaf surface per shoot, leaf area index, number and biomass of taxa of epiphytic flora. Significant differences in P. oceanica meadow structure were found among investigated sites, especially between sites in the vicinity of the fish farm and the other sites. Meadow density decreased at sites in the Dugi Otok channel and the main impact factors seem to be the input of organic matter, originating from the fish cages and sewage input. These human activities are a source of nutrient pollution and stimulate blooms of phytoplankton and higher algae. The sea grass meadow vitality seems to be more negatively affected in the channel. The highest values of shoot density were recorded at investigated sites VR and ME at the outer part of the Dugi Otok Island. The shoot density was very low at site FU, situated in the channel. Biomass of the epiphytic algae exhibited the highest values at the site FU, while at the other investigated sites the values were significantly lower. Concerning the epiphytic macroflora, a total of 55 taxa of epiphytic macroalgae were identified and the class Rhodophyta dominated in all samples. The present study shows the high differences in morphological and structural characteristics of Posidonia oceanica meadows among various sites with and without anthropogenic influence.

The effects of polychaete (Lysidice ninetta, L. collaris, Nematonereis unicornis (Annelida: Polychaeta)) and limnoriid isopod (Limnoria tuberculata (Crustacea: Isopoda)) borers in the Mediterranean sea grass Posidonia oceanica (Potamogetonaceae) were assessed in the meadows of Olbia and Genoa (western Mediterranean Sea). Borer invertebrates were mainly found into the old leaf sheaths of the sea grass. At Olbia, a mean density of borers (202.6±34.8 ind m−2) significantly higher than at Genoa (23.2±7.3 ind m−2) was observed. In 3.3% of samples from Olbia, large polychaetes and isopods were also observed boring into living plant tissues. Only fractions from 0.8—3.9% of the sheath production was actually removed by borers at the two studied meadows. The fact that sheath weight loss with time was higher at Genoa than at Olbia regardless of the presence of borers suggests that other factors than the activity of such organisms are important in the sheath decay process.

The presence of suctorian ciliates attached to the cuticle of heavily ornamented free-living marine nematodes, especially the family Desmodoridae, has been reported. Observations of nematode hosts and their attached ciliates were made from samples extracted from very fine muddy sands of tropical Australian sea grass meadows. Measurements of the point of attachment of the ciliates revealed that they tend to position themselves near the anus/cloaca of the nematode host.

Cymodoceaceae is a family of flowering plants, sometimes known as the “manatee-grass family,” the family Cymodoceaceae includes only marine species. The angiosperm phylogeny II system, of 2003 (unchanged from the APG system, of 1998), does recognize Cymodoceaceae and places it in the order Alismatales, in the clade monocots. They are marine hydrophytes that grow and complete their life cycle in a submerged condition, in a saline environment. Like terrestrial plant they obtain their energy from light through photosynthesis thus, they grow only in clear and shallow water, and at the suitable condition, they form beds or meadows. The family includes five genera, totalling 16 species of marine plants occurring in tropical seas and oceans (so-called seagrasses). Cymodoceaceae consist of five genera such as Amphibolis, Cymodocea, Halodule, Syringodium, and Thalassodendron. In this genera Cymodocea rotundata Ehrenb. and Hempr. Ex Asch. Cymodocea serrulata, (R.Br.) Asch. and Magnus, Halodule pinifolia (Miki) Hartog, Halodule uninervis (Forssk.) Asch and Syringodium isoetifolium (Asch.) are the species mostly adopted in Indian coastal region. These seagrass species have unique nature and wide application to the environment including human being. In this article botanical aspects, phytochemistry and ethnopharmacology of these five seagrass species belong to Cymodoceaceae family will be discussed.

Stable carbon isotope measurements (δ13C) were used to assess the sources of carbon assimilated by the fan mussel Pinna nobilis, in sea grass Posidonia oceanica meadows, and an associated shrimp Pontonia pinnophylax which occurs within this bivalve's mantle cavity. The primary carbon sources available to both animals displayed a wide range of δ13C values, from −12·3 to −22·3‰. The δ13C and δ15N of Pinna nobilis and Pontonia pinnophylax suggest that they assimilate carbon from similar sources, occupy comparable trophic levels and that their association is commensal.

Abstract. Evolution of vegetation in the Utinoe Lake basin was studied. Periodicity of vegetation changes in its basin were reconstructed by the palynological data. The Middle Holocene stage of the vegetation evolution proceeded in the conditions of general planetary increase in average annual temperatures, accompanied by flooding of lowland plains by the Sea of Japan. Composition of the polydominant forests on the ridges during the Middle-Late Holocene was more rich what the present time were formed. Vegetation of the foothill plains was represented with sedge and mixed meadows. The Late Holocene stage was characterized by a decrease in average annual temperatures and series of climatic changes. Its beginning was marked by the cooling, during which the coastal lowlands were freed from sea waters. Climate deterioration caused expansion of dark coniferous and small-leaved plants in the Utinoe Lake basin, as well as reduction of polydominant forests. On the foothills near the coast of the Peter the Great Bay sedge meadows were developed, sometimes there were thickets of Betula sect. Nanae and sphagnum swamps. At the end of the Late Holocene the warming occurred again. On the mountain frame of the Utinoe Lake basin, the vegetation formations with the dominance Q. mongolica, Q. dentata, A. holophylla, P.koraiensis with the presence of birches began to dominate. The dissemination of Pinus densiflora, Ulmus, Carpinus cordata and Acer has increased. On the lowlands the sedge-reed meadows with different grass dominated.

The diversity of coastal vegetation (salt marsh) that includes halophytic herb communities on marine deposits forming under active seawater influence on the White Sea western coast is discussed. The great diversity of coast habitats is responsible for the great variety of vegetation. The vegetation prodromus contains 18 associations (with 3 variants) and 1 community type, belonging to 7 alliances, 5 orders and 5 classes. Classes Zosteretea marinae (sublitoral sea grass vegetation), Potametea pectinati (aquatic meso- and olygotrophic vegetation), Thero-Salicornietea (pioneer annual succulents littoral com­munities) and Honckenyo-Elymetea arenariae (vegeta­tion of sandy, pebbly or gravely beaches, coastal banks and dunes) are represented by in one association for each. Juncetea maritimi (sea shore meadows on weakly and moderate saline substrates), the largest class, provides the main vegetation variety. The characteristics of syntaxa ecology, and global and regional distributions are made. The widespread and rare associations that need an addi­tional study of composition, distribution and synecology are defined. The area of syntaxa distribution are widened to the east. New variant (ass. Festucetum rubrae var. Alopecurus arundinaceus var. nov.) is suggested.

2007/2008
L’obiettivo di questa tesi è valutare l’influenza di vari fattori biotici e abiotici che possono influenzare l’abbondanza degli uccelli acquatici nella laguna di Grado e Marano. La laguna di Grado e Marano è situata nel NE del mare Adriatico e ha un’estensione approssimativa di 160 km2. Il passo introduttivo nell’implementazione della struttura del progetto è stato individuare un sistema innovativo per la raccolta, la standardizzazione e l’archiviazione dei dati ornitologici. Immagini satellitari ASTER sono state utilizzate per classificare differenti tipi di habitat, incluse le praterie di fanerogame. Nel Sistema Informativo Geografico sono state incluse quattro variabili abiotiche (azoto e fosforo totale, salinità e tessitura del sedimento) e tre fattori biotici (comunità bentonica, praterie di fanerogame e l’abbondanza degli uccelli acquatici presenti (Mean values: December 2006, January and February 2007), raggruppati in unita funzionali o guilds). Una griglia UTM con celle di grandezza 1km x 1km (Operational Geographic Units, OGU), è stata sovrapposta all’intera laguna. Per definire le unità ecologiche sono state applicate la classificazione gerarchica e l’analisi delle componenti principali. Da ultimo è stata usata l’analisi di corrispondenza per esaminare la relazione tra uccelli acquatici raggruppati in guilds e le unità ecologiche. L’integrazione dei metodi standard di censimento con i database relazionali per archiviare e analizzare i dati ornitologici, con le tecniche di telerilevamento e di GIS e con i metodi di analisi multivariata, rappresenta un set di strumenti efficienti e potenti per il monitoraggio integrato della laguna. Il soddisfacente risultato ottenuto si potrebbe applicare per ottenere un miglioramento della struttura gestionale di numerose zone umide dell’Adriatico. The purpose of this thesis is to estimate the influence of several biotic and abiotic factors on the abundance of waterbirds in the Grado-Marano Lagoon. The Grado-Marano Lagoon is situated in the Northeast of the Adriatic Sea with an extension of approximately 160 km2. Design of an innovative system for ornithological data gathering, standardisation and storage has been an initial step in the whole project structure. Waterbirds census was carried out by periodically monitoring the bird population over a two-year period (July 2006- July 2008). The present research is making use of the integrated waterbirds census database December 2006 - February 2007 (Daylight Time Counts completed by Aerial Surveys). Terrestrial and aerial survey methods allowed us to describe bird density and habitat use. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite images were utilized to classify different types of morphologies and habitat, including sea grass meadows. Four abiotic factors (total nitrogen, total phosphorous, salinity and sediment texture) and three biotic factors (benthic community, sea grass meadows and waterbird guild abundance) were integrated into a GIS. The flexibility of the procedure proposed in this PhD research depends on the concept of the Operational Geographic Unit (OGU) as a useful tool to integrate in a GIS georeferenced multisource data A regular UTM grid of square cells (OGU), 1km × 1km, was superimposed on the entire lagoon. Using the Hierarchical Cluster Analysis technique it was possible to delineate ecological units (clusters of OGUs) and Principal Component Analysis was used to reduce the dimensionality of the factors considered. Subsequently, Correspondence Analysis (CA) was used to examine the relationship between waterbird guild abundance and ecological units. The results obtained from this study show that sea grass meadows represent a fundamental trophic resource for aquatic birdlife in the lagoon. It is therefore indispensable to assess the distribution of phanerogam meadows and to identify the principal ecological parameters. In this context, GIS techniques allow us to integrate significant amounts of environmental data and multivariate analysis helps us to reduce the dimensionality of the data set. The integration of standard waterbirds census methods, relational databases for the ornithological data storing and analysis, remote sensing techniques, GIS technologies and multivariate statistical methods provides us with a set of powerful and efficient tool for lagoon integrated monitoring. It demonstrates the promising potentials in reforming the management frameworks of the numerous coastal wetlands in the Adriatic.
XXI Ciclo
1979

A group of sea otters laze at the edge of Elkhorn Slough. They float on their backs in the steel- gray water, paws folded against their chests, gazing at the small boat steered by ecologist Brent Hughes of the University of California– Santa Cruz. Hughes has documented a profound shift in the slough’s ecology, triggered by the otters. Sea otters were nearly driven to extinction by fur hunters in the 1800s, and were gone from Elkhorn Slough for a century. In 1984, when the first sea otters recolonized, Elkhorn Slough’s once bountiful eelgrass beds had dwindled to a few small, scattered patches. Now, more than thirty years after the sea otters’ return, expanding eelgrass beds grow lush beneath the water’s surface, the dense leaves sheltering juvenile fish and feeding an array of invertebrate grazers. The slough, on the central California coast, is one of the most severely polluted estuaries on the planet. Artificial fertilizer applied to 2.69 million acres of farmland in the neighboring Salinas Valley runs into its waters. The excess nutrient load causes eutrophication. It also fuels the growth of epiphytic algae that thrive on the surface of eelgrass leaves, blocking the sunlight the grass needs and smothering whole beds. The problem is common in estuaries around the globe, which receive heavy loads of nutrients from rivers draining polluted watersheds. Seagrass meadows filter contaminants from water and prevent coastal erosion in addition to acting as nurseries for fish and invertebrates. These crucial habitats are disappearing. The global distribution of seagrasses has decreased by 29 percent over the last 140 years, and 58 percent of the surviving seagrass meadows are in decline. Nutrient pollution of coastal waters had long been thought to be the main driver of this trend. But in Elkhorn Slough, the eelgrass has made a remarkable comeback even as pollution loads continued to climb. The mechanism of this welcome ecological shift was unknown until Hughes demonstrated that sea otters are the key. He began to put the pieces of the puzzle together when he went diving in Tomales Bay, an unpolluted estuary to the north. The eelgrass in Elkhorn Slough was lush and green despite intense pollution; in Tomales Bay, where there are no sea otters, the eelgrass was a dull brown, smothering under epiphytic algae.

By late April, the snow is gone from the beaver meadow. The promises of March are starting to be fulfilled: insects are on the wing, some of the willows have furry catkins along their branches, and fish jump from the quiet waters of the beaver ponds. I can no longer easily get around the beaver meadows on foot unless I wear chest waders. The sound of the beaver meadow in March was primarily wind. By April, the sound is primarily moving water. The water gurgles, shushes, and whispers. In another month it will roar with the melting snows. Another three miles up the creek valley and 1,500 feet higher, one of my long-term study sites still lies under 6 feet of snow, but in the meadow I see only one patch of tenacious snow-ice in the deep shade beneath a spruce along the northern edge of the meadow. I know that snow will still fall here during late spring storms, but it will melt quickly. March felt on the cusp, as if it could as easily tip toward winter or spring. Late April is definitely spring headed toward summer. The beaver meadow remains a riverscape more brown and tan than green. The willows are still leafless, although some of the branch tips are turning pale yellow-green and others seem to be taking on a more vivid orange hue. I can see the leaf buds starting to swell. The grass has just begun to grow in dark green tips steadily forcing their way through the thick mat of last year’s dead stems. Clusters of new leaves on low-growing wintergreen are the only other sign of green outside of the channels. Some of the smaller side channels are thick with emerald green algae undulating slowly in the current. A stonefly lands on my hand. Its slender, dark gray body seems surprisingly delicate for a creature that has hatched into the vagaries of April air, with its potential for blasting winds and sudden snow squalls.

This chapter focuses on the author's quest to see Henslow's Sparrow in Ames, New York. The Henslow's Sparrow population has had a 95 percent decline since the mid-sixties. It does not belong in that part of New York State and is one of those species with fussy needs: damp, grassy meadows that include matted vegetation and a variety of weeds. Those wide, empty, weed-choked fields are less and less common; farming and building houses are some activities that destroy the habitat that the Henslow's Sparrow needs to breed. Audubon named the bird after John Stevens Henslow, who first found the bird in 1829 in Kentucky. The chapter then considers how the author found a deep connection with the Henslow's Sparrow.

June, when the snows come hurrying from the hills and the bridges often go, in the words of Emily Dickinson. In the beaver meadow, the snows are indeed hurrying from the surrounding hills. Every one of the 32 square miles of terrain upslope from the beaver meadow received many inches of snow over the course of the winter. Some of the snow sublimated back into the atmosphere. Some melted and infiltrated into the soil and fractured bedrock, recharging the groundwater that moves slowly downslope and into the meadow. A lot of the snow sat on the slopes, compacted by the weight of overlying snow into a dense, water-rich mass that now melts rapidly and hurries down to the valley bottoms. North St. Vrain Creek overflows into the beaver meadow, the water spilling over the banks and into the willow thickets in a rush. I can hear the roar of water in the main channel well before I can see it through the partially emerged leaves of the willows. Overhead is the cloudless sky of a summer morning. A bit of snow lingers at the top of the moraines. Grass nearly to my knees hides the treacherous footing of this quivering world that is terra non-firma. I am surrounded by the new growth of early summer, yet the rich scents of decay rise every time I sink into the muck. I walk with care, staggering occasionally, in this patchy, complex world that the beavers have created. I abruptly sink to mid-thigh in a muck-bottomed hole, releasing the scent of rotten eggs, but less than a yard away a small pocket of upland plants is establishing a roothold in a drier patch. A seedling spruce rises above ground junipers shedding yellow pollen dust and the meticulously sorted, tiny pebbles of a harvester ant mound. I extract my leg with difficulty and continue walking. As I walk around the margin of another small pond, the water shakes. Sometimes the bottom is firm in these little ponds, sometimes it’s mucky—I can’t tell simply by looking through the water.

By mid-March, daytime temperatures above freezing have left muddy puddles all over the unpaved road that runs above and beside the beaver meadow. This road extends to the national park trailhead farther upstream but is now closed for winter. I enter the beaver meadow on a lightly overcast day that is windy, as I expect March to be. Lack of recent snowfall and warm temperatures have caused the snowpack to shrink down, and I no longer break through into hidden pockets of air around the base of the bushy willows. I do break through the ice on my snowshoes, sinking in a slow motion that allows me to scramble and keep my feet dry . . . mostly. I sink in above the ankle at one point and the resulting icy ache makes me appreciate the ability of beavers to stay warm. The snow covering the higher peaks and the adjacent lateral moraines appears about the same, but numerous spots of bare ground have appeared along the creek banks. The remaining snow resembles a blanket draped over the undulating, grassy ground rather than an integral part of the landscape. I stand on the snowbank at the downstream end of one of the larger beaver ponds. The dam merges into a vegetated berm and appears to be intact, but I can hear water flowing swiftly somewhere beneath the snow. Most puzzling is that I can’t see where the water is going: the nearest downstream standing water has no apparent inflow or current. Mysterious, intricate plumbing surrounds me. The beaver meadow is on the move, flowing and changing, preparing for the season of birth and growth. Standing water is noticeably more abundant than a month ago. Interspersed among the ice and snow are big puddles and little ponds, some connected and draining, others isolated and still. The still pond waters have a shallow covering of meltwater underlain by ice with large, irregularly shaped air pockets trapped in the upper layer. These I can easily break with the tip of my ski pole. Thousands of tiny bubbles deeper in the ice look milky.

The Patagonian steppes and the Río de la Plata grasslands occupy a vast proportion of the plains, plateaus, and hills of southern South America, and are characterized by the almost absolute absence of trees. Prairies and steppes (grass and low shrubs) are the dominant physiognomic types, and forests are restricted to some riparian corridors. Savannas become important only in the ecotones of these regions, whereas meadows may be locally important under particular topographic or edaphic conditions. The Río de la Plata grasslands (RPG), one of the most important grassland regions in the world, extend between 28°S and 38°S latitude, covering about 700,000 km2 of eastern Argentina, Uruguay, and southern Brazil. The boundaries of these grasslands include the Atlantic coastline to the east, dry temperate forests to the south and west, and subtropical humid forests to the north. Woody vegetation within the region is restricted to small areas near water bodies, such as the gallery forests along the large Paraná and Uruguay rivers and their tributary streams. The Patagonian steppes occupy the southern tip of the continent from approximately 40°S, and are framed by the Andes to the west and the Atlantic coast to the east and south and cover more than 800,000 km2 of Chile and Argentina. Toward the west, the region displays a sharp ecotone with the subantarctic forests, whereas to the north it grades into a broad zone of Monte scrublands in central Argentina. The RPG and the Patagonian steppes are separated by a wide strip of woody vegetation, the Monte and Espinal phytogeographic units (see chapter 10; Cabrera and Willkins, 1973). In this chapter, we describe the heterogeneity and main characteristics of the dominant ecosystems of the Patagonian steppes and the RPG, focusing on environmental controls and human-induced changes. Although numerous criteria have been applied to describe the internal heterogeneity of both regions, we emphasize here the structural and functional attributes of vegetation as integrators of climate, physiography, and land use.

Just when spring appears to have arrived, a late-season storm blows down from the north. Despite the overcast sky, the temperature at first is beguilingly warm. Rain starts to fall, then changes to sleet as the temperature drops. “Rough winds do shake the darling buds of May,” indeed. The sleet becomes graupel—crusty, rounded pellets of snow—and then wet flakes. Blobs of slush fall from overhanging branches and float briefly down the creek before melting and dispersing. Pulses of wind and snow gust in as birds shelter silently among the densely needled branches of big spruce trees. The moose that has spent the winter around the beaver meadow lies calmly in a protected spot at the base of a spruce. A foot of snow obliterates the newly green shoots of grass. I see no outward indication of it, but perhaps, in the warm darkness of the lodge, the beaver kits have been born. They start small, only about a pound at birth, but they are born fully furred, with open eyes and incisors erupted, almost ready to get down to the business of chewing branches. Each year’s litter is born in May or early June. Usually two to four kits are born, but a litter can be a single kit or as many as eight kits. Baby food for beavers is herbaceous vegetation, which the kits start eating within two weeks. By the end of July or early August the kits will be weaned and able to forage on their own. A varied diet of vegetation allows them to reach a weight of 10 to 16 pounds by the time the ice returns. The first year is a grace period for the new kits. Unlike the yearlings, the kits do not help maintain the lodge or cache food against the lean days of winter. They simply get to enjoy life and explore the wondrous new world into which they have been born. Diverse human observers watching this exploration by young beavers have interpreted their activities as an expression of joy.