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Two studies on the acoustics of multiphase materials : seagrass tissue and encapsulated bubblesEnenstein, Gregory Robert 07 October 2014 (has links)
There are two focal points of this thesis: the acoustics of seagrass and the acoustical properties of encapsulated bubbles for underwater noise abatement. The acoustical properties of seagrass have applications in mine hunting, shallow water sonar, and environmental acoustic remote sensing. In order to optimize these applications, a predictive model of acoustic propagation in seagrass beds is sought. Previous laboratory research has indicated that the tissue acoustic properties of seagrass as well as the tissue physical structure and entrained air masses inside the leaves contribute to the overall acoustic behavior. The present research utilized a glass laboratory resonance tube to find the low frequency (1 kHz-4 kHz) acoustic compressibility of two species of seagrass, Thalassia testidinum and Halodule wrightii. By using a mixture of finely divided seagrass tissue suspended in seawater, the bulk moduli of the seagrass species were extracted. In the second section, encapsulated bubbles were analyzed as a method of abating underwater anthropogenic noise sources, since these sources, including marine piledriving and oil and gas exploration and production, pose potential harmful effects to marine life. Previous research, which used an array of rubber-shelled encapsulated bubbles, found the attenuation from these bubbles in be in close accordance with an existing encapsulated bubble model. Experiments were performed in a small laboratory resonance tank, a large outdoor acoustic tank, and at Lake Travis Test Station (LTTS) in order to determine the effects of varying an encapsulated bubble's wall thickness and fill material on bubble resonance frequency and damping. Results found that increasing the wall thickness tended to increase the balloon resonance frequencies measured in the small tank, which was strongly correlated to the frequency of maximum noise reduction in the large outdoor test tank and LTTS tests. The addition of polyester fibers and aluminum wool as fill materials decreased both the resonance frequency and quality factor, whereas helium-filled filled encapsulated bubbles had an increased resonance frequency but decreased quality factor as compared with air-filled bubbles. The resonance quality factor and void fraction further proved to affect the noise reduction near bubble resonance in the outdoor acoustic tank and LTTS tests. The measurements made with a single bubble in a small laboratory tank were correlated to measurements with a full-size system composed of many bubbles operating in open water. / text
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The ecology of a Zostera noltii bed ecosystem in the SolentSamiaji, Joko January 2001 (has links)
No description available.
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Fish and fisheries in the seagrass beds of the Quirimba Archipelago, Northern MozambiqueGell, Fiona Rachel January 1999 (has links)
No description available.
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A Taxonomic and Distributional Study of Seagrass in TaiwanKo, Chih-jen 06 September 2004 (has links)
Ten species of seagrasses are recognized in Taiwan and adjacent islands. They are, namely, Halophila beccarii Aschers., Halophila decipiens Ostenf., Halophila ovalis (R. Br.) Hook. f., Thalassia hemprichii (Solms) Aschers., Cymodocea rotundata Ehrenb. & Hempr. ex Aschers., Cymodocea serrulata (R. Br.) Aschers. & Magnus, Syringodium isoetifolium (Aschers.) Dandy, Halodule pinifolia (Miki) den Hartog, Halodule uninervis (Forssk.) Aschers. and Nanozostera japonica (Ascherson & Graebner) Toml. & Posl. The detail morphological charactors of these speices are descripted for the first time, and can be the basis of further research. These species are mainly distributed in the west coast of Taiwan, Hengchun peninsula, the Green Island, the Orchid Island, Hsiaoliuchiu, the Pescadores Islands, Quemoy and the Pratas Island, the habitats can be categorized as 4 types, which are muddy to sandy tidal flat, coral platform, wave-cut platform and fine-muddy seabed. The relation between types of habitat and occurrence is also discussed.
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Life History Trait and Growth Pattern of a Tripterygiid (Enneapterygius minutus) Population in the Seagrass Meadow on Green Island, TaiwanWang, Shao-i 05 February 2009 (has links)
Fluctuation of the seagrass ecosystem may be informative to the impacts of
environmental changes. This study focuses on a small, inconspicuous triplefin blenny,
Enneapterygius minutus, found in a specific tide pool of seagrass meadow on Gui Wan Bi,
Green Island, Taiwan. Its high abundance and stable residence make this species a suitable
candidate to monitor the condition of the seagrass ecosystem. Monthly collections were made
during low tide from April 2007 to July 2008. The otolith microstructure was examined to
study their age and growth circumstance. Developmental stages of the ovaries based on
histological characteristics together with data of batch fecundity and GSI value were applied
to estimate size at maturation and the spawning seasonality of the individual assemblages in
the tide pool. A length-frequency analysis was made by using the monthly data.
Enneapterygius minutus is a kind of short life species. It has a quite low batch fecundity and a
year-long breeding ability with a seasonal high peak mainly from late winter to late spring.
The recruitment of juvenile individuals began about a month after breeding had occurred.
These data show that Enneapterygius minutus uses seagrass meadows as a hatching and
nursing habitat. According to the close relationship between Enneapterygius minutus and
seagrass meadow, it would be possible to monitor this ecosystem by using this species as an
indicator when it is under environmental stress.
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Isolation and Purification of Planctomycetes associated with Harbor and Lagoon Seagrasses of the Red SeaBream, Holly 07 1900 (has links)
Planctomycetes
are
members
of
a
unique
superphylum
along
with
Verrucomicrobia
and
Chlamydia,
situated
in
the
domain
Bacteria.
They
have
distinct
structural
and
morphological
features,
and
discoveries
made
through
phylogenetic
analysis
indicate
their
important
role
in
nutrient
cycling.
Their
known
relationships
with
marine
photosynthetic
organisms
led
to
the
formation
of
this
study's
hypothesis,
namely,
that
Planctomycetes
can
be
isolated
from
the
biofilm
of
seagrass
species
of
the
Red
Sea
using
cultivation
techniques
adapted
for
these
organisms.
Preparation
of
solid
and
liquid
media
using
M13
with
both
agar
and
gellan,
and
2216
Difco
Marine
Broth
full-
strength,
1/10-strength,
and
with
antibiotics,
resulted
in
the
successful
isolation
of
Planctomycetes
as
confirmed
by
morphological
examination
and
transmission
electron
microscopy.
The
work
performed
in
this
study
provides
a
solid
foundation
for
further
studies
to
elucidate
the
metabolic
pathways
and
ecological
significance
of
Planctomycetes.
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Microplastic accumulation and impacts on eelgrass (Zostera marina L.) ecosystems throughout coastal Massachusetts, USAGerstenbacher, Cecelia M. 29 September 2022 (has links)
Microplastics have been discovered ubiquitously in marine environments. While their accumulation is noted in seagrass meadows, much work is required to understand microplastic accumulation patterns and mechanisms in this ecosystem, as well as microplastic impacts on seagrass plants and their associated epiphytic and sediment communities. We pursue this effort by quantifying microplastic densities in seagrass blades, sediments, and nearby water columns across nine sites in coastal Massachusetts and exploring their relationships to morphological and anthropogenic variables. Further, we synthesize the potential impacts microplastics have on relevant seagrass plant, epiphyte, and sediment processes and functions. Microplastics were found ubiquitously at all sites regardless of proximity to anthropogenic interference, with plant epibiont density influencing their accumulation on seagrass blades, and bulk density influencing accumulation within sediments. Literature review revealed that microplastics may harm seagrass ecosystems via physical obstruction of epiphytic and plant surfaces, nutrient cycle and sediment characteristic alteration, and sediment organism ingestion, with all impacts exacerbated by seagrasses high trapping efficiency. As microplastics become a permanent and increasing member of seagrass ecosystems it will be pertinent to direct future research towards continuing to explore their impacts and patterns behind their accumulation. / 2023-09-28T00:00:00Z
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Assessing the Impact of Groundwater Pollution from Marine Caves on Nearshore Seagrass Beds in BermudaCate, Jenipher R. 14 January 2010 (has links)
This investigation characterized karstic and nearshore environments of Bermuda
to describe 1) behavior and periodicity of cave springs; 2) submarine spring water
quality; and 3) nearshore marine seagrass density. Caves can be conduits for
groundwater pollution where terrestrial anthropogenic processes leach nutrient enriched
water into marine caves springs that flow directly into coastal waters. Seagrass may
serve as an environmental indicator due to its susceptibility to anthropogenic pollution.
In 2007, environmental water monitoring devices were moored at the entrance of
coastal cave springs throughout Bermuda to retrieve data on water quality, flow
volume, velocity and direction. Nutrients (nitrate, phosphate, nitrite, and ammonium)
and fecal bacteria (Enterococcus spp. and Escherichia coli) were measured in each cave.
To qualify a link between terrestrial pollution and the nearshore environment, seagrass
density within 100 m from cave entrances were measured.
Bermuda caves were tidally influenced. Caves in Harrington Sound showed a
delayed tidal flux with smaller ranges due to the restricted tidal inlet. Four caves
exhibited a 1:1 in:out flow ratio. Caves with an imbalance flow ratio could be influenced
by additional entrances, connection to an alternate water body, or cave geometry. Cave
water was similar between caves. Environmental parameters and nutrients changed
together, excluding seasonal variations in temperature (17.89 to 22.94 degrees C). Higher
nutrients and fecal coliforms within caves indicated sewage may be leaching into the
subsurface ground water system. Three seagrass species were evenly distributed within patchy meadows. Densities
ranged from 0.91 to 4.5 (on a Braun-Blanket Scale). Higher mean densities in
Harrington Sound, suggested the enclosed, protected nature of the sound allowed for
reduced wave and current action. Syringodium filiforme decreased in density towards the
ocean signifying a direct influence of cave water on seagrass beds. Tidal in and out-flux
allowed for a constantly changing environment suitable for a mixture of seagrass
species. Higher dissolved inorganic nutrient concentrations were associated with
locations lacking seagrass.
This study found 1) cave springs connected groundwater and nearshore seagrass
ecosystems; and 2) components associated with terrestrial sewage pollution (DIN,
HPO4=, and Enterococcus spp.) were higher within caves than nearshore waters.
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On using airborne optical vertical polarisation to remove sea surface reflectance for enhanced visualisation of seagrass and other benthos.Hart, David January 2009 (has links)
Mapping of marine benthic flora using remote sensing techniques has, over the past decade, been used to locate environmentally stressed areas in the South Australian marine environment. These studies used panchromatic/colour aerial photography and/or medium resolution multispectral satellite imagery to create a time series showing location and rate of seagrass loss. While successful within their project parameters, these studies were limited by conditions at time of image capture, such as sun-glare, wave action and low contrast in deeper waters due to absorption and scattering. This research thesis reports the successful use of polarisation on the capture of visible and near infra-red optical imagery as a method to minimise these limiting factors. Two experimental test flights were undertaken using commercial off-the-shelf digital cameras mounted in the camera port of a light aircraft. The first flight compared vertical polarisation using co-mounted visible and infra-red cameras. The second flight compared vertical and horizontal polarisation using co-mounted identical visible spectrum cameras. The main finding of this series of airborne polarisation experiments is that sea surface reflection is removed by using vertically polarised filters at, and around, the Brewster angle of 53 degrees off nadir, especially when viewing sunwards. The effect is the same in the visible and infra-red parts of the spectrum. This reflection includes sky reflectance, lambertian sun glare, reflection due to wave action, and turbulence, but not direct solar specular reflection. Vertical polarisation filters improve the imaging of benthic flora compared to horizontally polarised imagery and, by extension, non-polarised imagery. The successful use of polarisation to remove surface reflectance over water is limited to imagery captured at or near the Brewster angle. By using successive overlapping frames this can be achieved, as shown by the experiments. Ideally all of the image should be at the Brewster angle. A conceptual design for a conical optical scanner which builds wide-swath imagery where each pixel in each band is solely a record of the vertically polarised signal at the Brewster Angle is presented as a result of these experiments. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374494 / Thesis (M.Sc.) - University of Adelaide, School of Earth and Environmental Sciences, 2009
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The Measurement of Seagrass Photosynthesis Using Pulse Amplitude Modulated (Pam) Fluorometry and its Practical Applications, Specifically in Regard to TransplantationL.Horn@murdoch.edu.au, Lotte Horn January 2006 (has links)
Photosynthetic activity of three seagrass species, Posidonia sinuosa Cambridge et Kuo,
Posidonia australis Hook. f. and Halophila ovalis (R. Br.) Hook., growing in Cockburn
Sound, Western Australia, was assessed using an underwater pulse amplitude modulated
fluorometer (Diving-PAM). The study aimed to determine possible causes and the
extent of stress to seagrasses during transplantation, so that rehabilitation efforts can be
improved by reducing stress during the transplant process.
Absorptance factors for each species were determined as 0.64 ± 0.04 for P. sinuosa,
0.59 ± 0.02 for P. australis and 0.55 ± 0.02 for H. ovalis, which were substantially
lower than previously reported photosynthetic absorption factors. Transmittance,
reflectance and non-photosynthetic absorptance of light diverted between 35-45% of
irradiance from use in photosynthesis. An investigation of potential errors during
measurement of rapid light curves (RLCs) reinforced the importance of ensuring that
leaves remained stationary in the Universal Sample Holder. Any movement of seagrass
leaves resulted in incorrect measurements of electron transport rates (ETR).
A study on seasonal photosynthetic rates of each species found that maximum ETR
(ETRmax) varied seasonally and among species. The highest ETRmax for each species
occurred during summer, when ambient irradiances were at a maximum, and decreased
during autumn. H. ovalis had the highest overall ETRmax in summer, followed by
P. australis and P. sinuosa. Effective quantum yield(ΔF/Fm′)of each species varied
seasonally, changing inversely with irradiance, which agrees with previously reported
studies. ETRmax for each species also showed a diurnal pattern coincident with
irradiance throughout the day. The ÄF/Fm for all species demonstrated a diurnal
decrease in photosynthetic efficiency coincident with the midday irradiance maximum.
Large natural variation in ETR was detected in all species, indicating that the effects of
external stress on ETR may be difficult to detect.
Two adjacent, physically separated seagrass meadows were examined to determine if
apparent visual differences between the sites were reflected by measured physical and
photosynthetic characteristics. ETR, leaf area index and sediment grain size differed
between sites, but ΔF/Fm, canopy height, shoot density and epiphyte biomass did not,
indicating a poor connection between physical and photosynthetic characteristics at
these two meadows. Therefore caution should be used when attempting to visually
assess the photosynthetic activity of a site based on physical characteristics.
Changes in photosynthetic activity were monitored to determine seagrass stress during
transplantation, and post-transplantation recovery. Two transplantation methods, sprigs
and plugs, were examined, and photosynthetic activity was compared before, during and
after transplantation. ETRmax of sprigs took one to two months to increase to the same
level recorded at a control meadow, primarily due to desiccation stress suffered during
transport. The ΔF/Fm′ decreased below 0.2 after transplantation, but fully recovered
after three months. Survival of sprigs was reduced due to strong currents and heavy
epiphytic fouling. The ETRmax of transplanted plugs (5, 10 and 15 cm diameter) took up
to one week to recover to the same level recorded at a control meadow. Survival of
plugs was reduced due to winter swells and storms. Since the leading human-controlled
cause of transplant failure was desiccation stress, future transplanting efforts should
endeavour to keep seagrasses submerged at all times during the transplanting process.
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