scholarly journals In situ Responses of the Eelgrass Zostera marina L. to Water Depth and Light Availability in the Context of Increasing Coastal Water Turbidity: Implications for Conservation and Restoration

2020 ◽  
Vol 11 ◽  
Author(s):  
Shaochun Xu ◽  
Pengmei Wang ◽  
Feng Wang ◽  
Peng Liu ◽  
Bingjian Liu ◽  
...  
Keyword(s):  
Water Depth ◽  
Zostera Marina ◽  
Donor Site ◽  
Light Availability ◽  
Shoot Density ◽  
Depth Range ◽  
Light Deprivation ◽  
Depth Limit ◽  
Seagrass Meadows

Accelerating losses of seagrass meadows has led to efforts to restore these highly productive and beneficial ecosystems globally. Depth and light availability are critical determinants of seagrass restoration success. Eelgrass (Zostera marina L.) is the dominant seagrass species in the temperate northern hemisphere, but its global distribution has reduced dramatically. The main aims of this study were to determine: (1) the depth limit for Z. marina survival in Ailian Bay, north China, and (2) how light availability affects the growth and recruitment of Z. marina as a basis for identifying a suitable depth range for successful restoration. To achieve these aims, Z. marina shoots were transplanted from a nearby donor site, Swan Lake, to an experimental site, Ailian Bay, and the temporal responses of Z. marina shoots to light availability at water depths ranging from 1 to 8 m were investigated using in situ suspended cultures. Four suspended shoot transplantation experiments were conducted in 4 years. The results showed that the transplanted Z. marina shoots could survive and branch during an annual growth cycle, permanently underwater, at a depth ≤3 m. Due to the local turbidity of the waters in Ailian Bay, a depth of 4 m led to sufficient light deprivation (reduced to 6.48–10.08% of surface irradiance) to negatively affect seagrass shoot density and clonal reproduction. In addition, reproductive shoot density also tended to decline with water depth and light deprivation. Our results indicated that Z. marina population recruitment, through sexual and asexual (clonal growth) reproduction, were negatively affected by increasing water depth and light deprivation. These findings may provide a suitable depth range for the successful restoration of Z. marina in local coastal waters. They may also be applied to the management and restoration of Z. marina globally.

scholarly journals Morphological and physiological response strategies of Vallisneria natans at different water depths and light conditions

2020 ◽  
Author(s):  
Qingchuan Chou ◽  
Jianfeng Chen ◽  
Wei Zhang ◽  
Wenjing Ren ◽  
Changbo Yuan ◽  
...  
Keyword(s):  
Resource Allocation ◽  
Water Depth ◽  
Control Experiment ◽  
Light Availability ◽  
Field Investigation ◽  
Leaf Length ◽  
Light Conditions ◽  
Water Depths ◽  
Light Acquisition

AbstractPhenotypic plasticity is an important adaptation to spatial and temporal environmental variations. For submerged macrophytes, adaptation to water depth and light variation is particularly important. To determine the morphological and physiological adaptive strategies of Vallisneria natans at different water depths and light conditions, we combined field investigation, light control experiment and in situ physiological response experiment. In the field investigation and the light control experiment, both water depth and light intensity had prominent effects on the morphological of V. natans, especially in fresh weight and leaf length. The leaf length elongated more rapidly at intermediate water depth sites with lower light intensity. In the in situ experiment, the survival boundary of V. natans is 5.5 m in Lake Erhai. Below this depth, the chlorophyll-a content increased gradually with increasing water depth. Our results demonstrated that V. natans can adapt to water depth and light availability by changing morphological, physiological and resource allocation. At low light condition, V. natans invested more resource for light acquisition, simultaneously, changing the photosynthetic pigment content to compensate for light attenuation; conversely, more resource was directed towards reproduction. These results will provide new insight for species selection when conducting aquatic plants restoration in freshwater ecosystem.HIGHLIGHTSWater depth and light availability affect the morphology, physiology, and resource allocation of V. natans.An alternative resource allocation pattern of V. natans could shift between light acquisition and reproduction.

scholarly journals Distribution, structure and state of seagrass habitats in the SW Black Sea (Burgas Bay, Bulgaria)

2015 ◽  
Author(s):  
Dimitar Berov ◽  
Diana Deyanova ◽  
Stefania Klayn ◽  
Ventzislav Karamfilov
Keyword(s):  
Community Structure ◽  
Black Sea ◽  
Organic Matter Content ◽  
Nutrient Concentrations ◽  
The Black Sea ◽  
Depth Range ◽  
Area Index ◽  
Depth Limit ◽  
Seagrass Meadows ◽  
Distribution Structure

Seagrass habitats play an important role in maintaining the biodiversity and functions of coastal marine ecosystems of the Black Sea. Еutrophication pressures in the 1970s and 1980s had a severe impact on phytobenthic communities, including deterioration, decrease in geographical and depth distribution and disappearance from certain areas. The state of Zostera spp. habitats in the SW Black Sea has not been studied since the 1970s. The purpose of this study is to evaluate the current distribution, structure and overall condition of seagrasses in Burgas Bay, Bulgaria. Historical sites with seagrass meadows were surveyed by SCUBA diving between 2009 and 2014, using destructive sampling and georeferenced digital photogrammetry. Nutrient concentrations in water were measured seasonally at selected sites to study the effects of eutrophication on seagrasses. Seagrass biomass, shoot density, leaf length and leaf area index were measured. Species diversity and biomass of zoobenthic organisms were also determined. Community structure was analyzed with multivariate statistical methods based on photo and destructive samples.The geographical extent of the meadows was mapped in GIS on recent satellite images, then verified by georeferenced photo samples. Results indicate that most of the seagrass meadows reported in the area in the late 1970s are present today. A decrease in the depth limit of the habitat was established in areas under local eutrophication pressures. A clear depth-related change in community structure was observed, where Zostera noltei dominated the 1-3 m depth range, followed by a mixed Z. noltei – Zannichellia palustris - Zostera marina community (3-4 m) , and dominance of Z. marina between 4 and 7 m. Zoobenthic communities within seagrass meadows were dominated by the gastropods Bittium reticulatum and Rissoa sp., the bivalve Loripes lucinalis, and oligochaetes. Abundance and species richness, as well as faunal dominance were significantly higher in seagrass meadows than in adjacent unvegetated sediments. Biometric parameters of Z. noltei showed significant correlations with measured eutrophication pressures (nutrient concentrations, LUSI index, sediment organic matter content). The ecological quality status of selected meadows was evaluated by using a multimeric indicator based on Z. noltei phenology data, which also showed clear correlation with anthropogenic pressures.

The deep-water brachiopod Dicoelosia King, 1850, from the Early Silurian tropical carbonate shelf of Anticosti Island, eastern Canada

1999 ◽  
Vol 73 (6) ◽  
pp. 1042-1055 ◽  
Author(s):  
Jisuo Jin ◽  
Paul Copper
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Depth Range ◽  
Eastern Canada ◽  
Bedding Planes ◽  
Iapetus Ocean ◽  
Lateral Margins ◽  
Anticosti Island ◽  
Maximum Flooding Surface

Dicoelosia occurs in two deep water benthic shelly assemblages on an Early Silurian (uppermost Aeronian, Stimulograptus sedgwickii Zone) carbonate ramp to shelf, within the 25 m thick bluish-grey mudstone of the Richardson Member in the middle Jupiter Formation, Anticosti Island, Québec. Dicoelosia dauphinensis new species is erected on the basis of its relatively large, elongate shell, with a concavo-convex lateral profile, moderately wide, planoconvex lobes and subparallel lateral margins. Dicoelosia dauphinensis first occurs in a Gotatrypa-Dicoelosia Community, in which it constitutes about 7 percent of the individuals within sampled populations. This is replaced about 2 m up section by a Resserella-Dicoelosia Community, where D. dauphinensis makes up 22 percent of the individuals preserved on single bedding planes. Subsequently, Dicoelosia becomes a rare component of the Stegerhynchus-Triplesia Community in a shallowing-upward succession of the upper Richardson Member. It is in this upper Richardson shelly community that Stimulograptus sedgwickii is locally common, together with in situ brachiopod nests of Eocoelia, Triplesia, and Lissatrypa at the upper Jupiter Cliff section. The water depth estimated for the Resserella-Dicoelosia Community is between 100-120 m, below the normal depth range of the Clorinda Community (BA5) on Anticosti, in a distal shelf setting about 80-100 km offshore from the Laurentia paleocontinent, on the west side of the Iapetus Ocean. The interpretation of water depth is based on the facts that, 1) Dicoelosia-rich communities are confined to strata, which lack shallow water sedimentological evidence such as thick calcarenites and hummocky cross stratification, 2) Dicoelosia does not occur with shallower water taxa seen in the overlying Clorinda and Stricklandia communities associated with cyclocrinitid algae, corals and stromatoporoids in the Cybèle Member, and 3) Dicoelosia occurs only in the deeper water sections of the Richardson Member, some 10-15 km basinwards from mid-shelf shallower Richardson facies of the Anticosti Basin. Thus, the Dicoelosia-rich communities are interpreted to mark a maximum flooding surface within the distal shelf to ramp Llandovery succession of Anticosti Island.

scholarly journals Distribution, structure and state of seagrass habitats in the SW Black Sea (Burgas Bay, Bulgaria)

2015 ◽  
Author(s):  
Dimitar Berov ◽  
Diana Deyanova ◽  
Stefania Klayn ◽  
Ventzislav Karamfilov
Keyword(s):  
Community Structure ◽  
Black Sea ◽  
Organic Matter Content ◽  
Nutrient Concentrations ◽  
The Black Sea ◽  
Depth Range ◽  
Area Index ◽  
Depth Limit ◽  
Seagrass Meadows ◽  
Distribution Structure

Seagrass habitats play an important role in maintaining the biodiversity and functions of coastal marine ecosystems of the Black Sea. Еutrophication pressures in the 1970s and 1980s had a severe impact on phytobenthic communities, including deterioration, decrease in geographical and depth distribution and disappearance from certain areas. The state of Zostera spp. habitats in the SW Black Sea has not been studied since the 1970s. The purpose of this study is to evaluate the current distribution, structure and overall condition of seagrasses in Burgas Bay, Bulgaria. Historical sites with seagrass meadows were surveyed by SCUBA diving between 2009 and 2014, using destructive sampling and georeferenced digital photogrammetry. Nutrient concentrations in water were measured seasonally at selected sites to study the effects of eutrophication on seagrasses. Seagrass biomass, shoot density, leaf length and leaf area index were measured. Species diversity and biomass of zoobenthic organisms were also determined. Community structure was analyzed with multivariate statistical methods based on photo and destructive samples.The geographical extent of the meadows was mapped in GIS on recent satellite images, then verified by georeferenced photo samples. Results indicate that most of the seagrass meadows reported in the area in the late 1970s are present today. A decrease in the depth limit of the habitat was established in areas under local eutrophication pressures. A clear depth-related change in community structure was observed, where Zostera noltei dominated the 1-3 m depth range, followed by a mixed Z. noltei – Zannichellia palustris - Zostera marina community (3-4 m) , and dominance of Z. marina between 4 and 7 m. Zoobenthic communities within seagrass meadows were dominated by the gastropods Bittium reticulatum and Rissoa sp., the bivalve Loripes lucinalis, and oligochaetes. Abundance and species richness, as well as faunal dominance were significantly higher in seagrass meadows than in adjacent unvegetated sediments. Biometric parameters of Z. noltei showed significant correlations with measured eutrophication pressures (nutrient concentrations, LUSI index, sediment organic matter content). The ecological quality status of selected meadows was evaluated by using a multimeric indicator based on Z. noltei phenology data, which also showed clear correlation with anthropogenic pressures.

scholarly journals Cutting out the middle clam: lucinid endosymbiotic bacteria are also associated with seagrass roots worldwide

2020 ◽  
Author(s):  
Belinda C. Martin ◽  
Jen A. Middleton ◽  
Matthew W. Fraser ◽  
Ian P.G. Marshall ◽  
Vincent V. Scholz ◽  
...  
Keyword(s):  
Rrna Gene ◽  
Depth Range ◽  
Seagrass Species ◽  
16S Rrna Gene Sequences ◽  
Seagrass Meadows ◽  
Halophila Ovalis ◽  
Endosymbiotic Bacteria ◽  
The World ◽  
Cutting Out

AbstractSeagrasses and lucinid bivalves inhabit highly reduced sediments with elevated sulphide concentrations. Lucinids house symbiotic bacteria (Ca. Thiodiazotropha) capable of oxidising sediment sulphide, and their presence in sediments has been proposed to promote seagrass growth by decreasing otherwise phytotoxic sulphide levels. However, vast and productive seagrass meadows are present in ecosystems where lucinids do not occur. Hence, we hypothesised that seagrasses themselves host sulphur-oxidising bacteria that could secure their survival when lucinids are absent. We analysed newly generated and publicly available 16S rRNA gene sequences from seagrass roots and sediments across 14 seagrass species and 10 countries and found that persistent and colonising seagrasses across the world harbour sulphur-oxidising Ca. Thiodiazotropha, regardless of the presence of lucinids. We used fluorescence in situ hybridisation to visually confirm the presence of Ca. Thiodiazotropha on roots of Halophila ovalis, a colonising seagrass species with wide geographical, water depth range, and sedimentary sulphide concentrations. We provide the first evidence that Ca. Thiodiazotropha are commonly present on seagrass roots, providing a mechanism for seagrasses to alleviate sulphide stress globally.

Effect of water depth on population parameters of a Typha glauca stand

1992 ◽  
Vol 70 (2) ◽  
pp. 349-351 ◽  
Author(s):  
I. Waters ◽  
J. M. Shay
Keyword(s):  
Water Depth ◽  
Shoot Density ◽  
Depth Range ◽  
Population Parameters ◽  
Shoot Height ◽  
Frequency Distributions ◽  
Shoot Size ◽  
Shoot Mass ◽  
Response To Water ◽  
Typha Glauca

The response of a Typha glauca stand to a water depth gradient was studied in a small marsh pond in Delta Marsh, Manitoba. Weekly density counts and height measurements were made from May to October 1986 in permanent quadrats at five depths from 25 to 100 cm. Shoot mass was estimated from shoot height using a regression model based on destructive analyses. Shoot density declined significantly from 41 shoots/m2 at 25 cm to 12 shoots/m2 at 85 cm but increased at 100 cm to 38 shoots/m2. Shoot mass increased in shoots growing at water depths from 25 to 65 cm, resulting in relatively constant stand biomass over this depth range. Stand biomass declined at 85 cm and reached its maximum (1789.8 g/m2) at 100 cm. Frequency distributions of shoot size categories based on height deviated from normality and were negatively skewed at all depths, with the greatest skewness occurring at 100 cm. These population parameters were interpreted as evidence of a plastic population response to water depth. Key words: clonal macrophyte, frequency distributions, plasticity, shoot density, Typha glauca, water depth.

scholarly journals The amount of light reaching the leaves in seagrass (Zostera marina) meadows

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257586
Author(s):  
Mats Björk ◽  
Maria E. Asplund ◽  
Diana Deyanova ◽  
Martin Gullström
Keyword(s):  
Zostera Marina ◽  
Light Exposure ◽  
Shoot Density ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Underwater Light Field ◽  
Seagrass Meadows ◽  
Sensitive Film ◽  
Wide Range

Seagrass meadows, and other submerged vegetated habitats, support a wide range of essential ecological services, but the true extents of these services are in many ways still not quantified. One important tool needed to assess and model many of these services is accurate estimations of the systems´ primary productivity. Such productivity estimations require an understanding of the underwater light field, especially regarding the amount of light that actually reaches the plants’ photosynthetic tissue. In this study, we tested a simple practical approach to estimate leaf light exposure, relative to incoming light at the canopy, by attaching light sensitive film at different positions on leaves of Zostera marina, eelgrass, in four seagrass meadows composed of different shoot density and at two different depths. We found that the light reaching the leaves decreased linearly down through the canopy. While the upper parts of the leaves received approximately the same level of light (photosynthetic photon flux density, PPFD) as recorded with a PAR meter at the canopy top, the average light that the seagrass leaves were exposed to varied between 40 and 60% of the light on top of the canopy, with an overall average of 48%. We recommend that actual light interception is measured when assessing or modelling light depending processes in submerged vegetation, but if this is not achievable a rough estimation for vegetation similar to Z. marina would be to use a correction factor of 0.5 to compensate for the reduced light due to leaf orientation and internal shading.

scholarly journals Trait gradients inform predictions of seagrass meadows changes to future warming

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Arianna Pansini ◽  
Gabriella La Manna ◽  
Federico Pinna ◽  
Patrizia Stipcich ◽  
Giulia Ceccherelli
Keyword(s):  
Global Warming ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
Western Mediterranean ◽  
Seagrass Meadows ◽  
Western Mediterranean Sea ◽  
Seagrass Ecosystem ◽  
Rhizome Biomass ◽  
And Function ◽  
Time Substitution

AbstractComparing populations across temperature gradients can inform how global warming will impact the structure and function of ecosystems. Shoot density, morphometry and productivity of the seagrass Posidonia oceanica to temperature variation was quantified at eight locations in Sardinia (western Mediterranean Sea) along a natural sea surface temperature (SST) gradient. The locations are spanned for a narrow range of latitude (1.5°), allowing the minimization of the effect of eventual photoperiod variability. Mean SST predicted P. oceanica meadow structure, with increased temperature correlated with higher shoot density, but lower leaf and rhizome width, and rhizome biomass. Chlorophyll a (Chl-a) strongly impacted seagrass traits independent of SST. Disentangling the effects of SST and Chl-a on seagrass meadow shoot density revealed that they work independently, but in the same direction with potential synergism. Space-for-time substitution predicts that global warming will trigger denser seagrass meadows with slender shoots, fewer leaves, and strongly impact seagrass ecosystem. Future investigations should evaluate if global warming will erode the ecosystem services provided by seagrass meadows.

scholarly journals Testing the effect of water in crevasses on a physically based calving model

2012 ◽  
Vol 53 (60) ◽  
pp. 90-96 ◽  
Author(s):  
S. Cook ◽  
T. Zwinger ◽  
I.C. Rutt ◽  
S. O'Neel ◽  
T. Murray
Keyword(s):  
Finite Element ◽  
Water Depth ◽  
Surface Mass Balance ◽  
Two Dimensional ◽  
Finite Element Code ◽  
Surface Mass ◽  
Starting Point ◽  
Physically Based ◽  
Calving Rate

AbstractA new implementation of a calving model, using the finite-element code Elmer, is presented and used to investigate the effects of surface water within crevasses on calving rate. For this work, we use a two-dimensional flowline model of Columbia Glacier, Alaska. Using the glacier’s 1993 geometry as a starting point, we apply a crevasse-depth calving criterion, which predicts calving at the location where surface crevasses cross the waterline. Crevasse depth is calculated using the Nye formulation. We find that calving rate in such a regime is highly dependent on the depth of water in surface crevasses, with a change of just a few metres in water depth causing the glacier to change from advancing at a rate of 3.5 kma–1 to retreating at a rate of 1.9 km a–1. These results highlight the potential for atmospheric warming and surface meltwater to trigger glacier retreat, but also the difficulty of modelling calving rates, as crevasse water depth is difficult to determine either by measurement in situ or surface mass-balance modelling.

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