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Frederick T. Short - One of the best experts on this subject based on the ideXlab platform.
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Eelgrass Genetic Diversity Influences Resilience to Stresses Associated with Eutrophication
Estuaries and Coasts, 2019Co-Authors: Holly K. Plaisted, Alyssa B. Novak, Sarah Weigel, Anita S. Klein, Frederick T. ShortAbstract:Eelgrass ( Zostera marina L.), an underwater marine flowering plant, has a high degree of morphological plasticity that allows it to survive and adapt to environmental changes. To test the effect of Eelgrass genetic diversity (measured as allelic richness and observed heterozygosity) on resilience to stresses associated with eutrophication, Eelgrass from ten genetically differentiated populations was studied in outdoor mesocosms. In a full factorial experiment lasting 3 months, Eelgrass was subjected to two light levels (100 and 58% ambient) and two sediment treatments (1 and 8% organic content). Some populations of Eelgrass showed higher resilience, measured as a combination of productivity and survival, when exposed to the stress of high sediment organic matter and, to a lesser extent, reduced light. Overall, Eelgrass resilience correlated positively with Eelgrass source population genetic diversity. The findings show that Eelgrass resilience to stress typical of eutrophic estuaries (low light, high organic sediment) is improved by genetic diversity, with implications for transplantation, conservation, and management.
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Eelgrass Distribution in the Great Bay Estuary 2005
2014Co-Authors: Frederick T. ShortAbstract:) is an essential habitat for the Great Bay Estuary (GBE) because it provides food for wintering waterfowl and habitat for juvenile fish and shellfish. Eelgrass is the basis of an estuarine food chain that supports many of the recreationally, commercially and ecologically important species in the estuary. Additionally, Eelgrass filters estuarine waters, removing both nutrients and suspended sediments from the water column. Eelgrass in the Great Bay Estuary is the largest monoculture in the State of New Hampshire and is considered a vital resource to the State’s marine environment. The present report describes and interprets the Eelgrass distribution data collected in 2005 for the Great Bay Estuary. The Great Bay Estuary is experiencing an alarming decline in both Eelgrass biomass and distribution that appears to be related to the declining water clarity of the estuary. Eelgrass biomass in Great Bay itself (grams of Eelgrass per meter square) has declined steadily (Trowbridge 2006) over the past decade, although the distribution has been relatively constant in Great Bay for the past 10 years at approximately 2,000 acres. In the Piscataqua River, recent declines in both natural and transplanted Eelgrass beds are now evident (Short and Beem, in prep) and are a combination of both loss of biomass and loss of distribution. In Portsmouth Harbor in the past 3 years, Eelgrass has receded at the deep edge of the meadows, creating an overall loss of distribution which has been accompanied by losses in biomass (Rivers 2007). In this study, we refer to Eelgrass biomass as measured by percent cover, i.e., the percent of the bottom which is vegetated with Eelgrass. Biomass is determined through a regression of field-measured biomass and field-measured percent cover. The percent cover map from the aerial distribution can then be converted to biomass (g dry weight Eelgrass m
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Macroalgae and Eelgrass Mapping in Great Bay Estuary Using AISA Hyperspectral Imagery.
2014Co-Authors: Shachak Pe'eri, Frederick T. Short, John Ru Morrison, Arthur C. Mathieson, Phil TrowbridgeAbstract:Results Increases in nitrogen concentration and declining Eelgrass beds in Great Bay Estuary have been observed in the last decades. These two parameters are clear indicators of the impending eutrophication for New Hampshire’s estuaries. The NH Department of Environmental Services (DES) in collaboration with the Piscataqua Region Estuaries Partnership adopted the assumption that Eelgrass survival can be used as the target for establishing numeric water quality criteria for nutrients in NH’s estuaries. One of the hypotheses put forward regarding Eelgrass decline is that an eutrophication response to nutrient increases in the Great Bay Estuary has been the proliferation of nuisance macroalgae, which has reduced Eelgrass area in Great Bay Estuary. To determine the extent of this effect, mapping of Eelgrass and nuisance macroalgae beds using hyperspectral imagery was suggested. A hyperspectral image was made by SpecTIR in August 2007 using an AISA Eagle sensor. The collected dataset was then used to map Eelgrass and nuisance macroalgae throughout the Great Bay Estuary. Here we outline the procedure for mapping the macroalgae and Eelgrass beds. Hyperspectral imagery was effective where known spectral signatures could be easily identified. Comprehensive Eelgrass and macroalgae maps of the estuary could only be produced by combining hyperspectral imagery with ground-truth information and expert opinion. Macroalgae was predominantly located in areas where Eelgrass formerly existed. Macroalgae mats have now replaced nearly 9% of the area formerly occupied by Eelgrass in Great Bay. Results Flow Chart of the Mapping Procedure SHOALS-3000 Survey dates: 9.30.05 10.1.05 Spot Spacing: 4 m X 4 m Coverage: 100% End-members Water attenuation * Each laser measurement is color coded to a flight line.
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effect of grazing by canada geese branta canadensis on an intertidal Eelgrass zostera marina meadow
Marine Ecology Progress Series, 2007Co-Authors: David O Rivers, Frederick T. ShortAbstract:Fishing Island, in Portsmouth Harbor on the Maine-New Hampshire border (USA), is the site of an intertidal Eelgrass (Zostera marina L.) bed that is part of SeagrassNet, an international program for long-term seagrass monitoring. Eelgrass bed parameters of canopy height, percent cover, and aboveground biomass have been monitored quarterly since October 2001 using the Sea- grassNet protocol. A flock of nearly 100 Canada geese Branta canadensis L. over-wintered at Fishing Island and grazed on Eelgrass from January to April 2003, an event that had not been seen at this meadow in 2 decades of observation. Before Canada geese were present, Eelgrass parameters demonstrated seasonal fluctuations typical of the region. During the grazing event, Eelgrass parame- ters declined drastically, and biomass losses reached 680 g m -2 in parts of the meadow. SeagrassNet data demonstrated that Eelgrass did not recover after the geese departed. Additional fieldwork con- ducted from February to July 2003 showed that Eelgrass recruitment via sexual reproduction at Fish- ing Island was minimal, and vegetative recovery was impeded by Canada goose consumption of the plant meristems. Unlike studies in other locations, which show seagrass quickly rebounding from annual grazing events, Eelgrass at Fishing Island showed little recovery from Canada goose grazing through July 2003.
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disturbance of Eelgrass zostera marina by commercial mussel mytilus edulis harvesting in maine dragging impacts and habitat recovery
Marine Ecology Progress Series, 2005Co-Authors: Hilary A. Neckles, Frederick T. Short, Seth Barker, Blaine S KoppAbstract:We studied the effects of commercial harvest of blue mussels Mytilus edulis on Eelgrass Zostera marina L. in Maquoit Bay, Maine, USA, at a hierarchy of scales. We used aerial photography, underwater video, and Eelgrass population- and shoot-based measurements to quantify dragging impacts within 4 sites that had been disturbed at different times over an approximate 7 yr interval, and to project Eelgrass meadow recovery rates. Dragging had disturbed 10% of the Eelgrass cover in Maquoit Bay, with dragged sites ranging from 3.4 to 31.8 ha in size. Dragging removed above- and be- lowground plant material from the majority of the bottom in the disturbed sites. One year following dragging, Eelgrass shoot density, shoot height and total biomass of disturbed sites averaged respec- tively 2 to 3%, 46 to 61% and <1% that of the reference sites. Substantial differences in Eelgrass bio- mass persisted between disturbed and reference sites up to 7 yr after dragging. Dragging did not affect physical characteristics of the sediment. The pattern and rate of Eelgrass bed recovery depended strongly on initial dragging intensity; areas of relatively light dragging with many remnant Eelgrass patches (i.e. patches that were missed by the mussel dredge) showed considerable revegetation in 1y r. However, by developing recovery trajectories from measurements at sites disturbed in different years, we projected that it would require a mean of 10.6 yr for recovery of Eelgrass shoot density within the areas of intense dragging characterizing most of the disturbed sites. A spatial simulation model based on measured rates of lateral patch-expansion (mean 12.5 cm yr -1 ) and new-patch recruitment (mean 0.19 patches m -2 yr -1 ) yielded a mean bed recovery time of 9 to 11 yr following dragging, de- pending on initial degree of plant removal. Model simulations suggested that with favorable environ- mental conditions, Eelgrass beds might recover from dragging disturbance in 6 yr; conversely, recov- ery under conditions less conducive to Eelgrass growth could require 20 yr or longer. This study shows that mussel dragging poses a severe threat to Eelgrass in this region and that regulations to protect eel- grass from dragging impacts would maintain the integrity of a substantial amount of habitat.
Hongsheng Yang - One of the best experts on this subject based on the ideXlab platform.
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restoring Eelgrass zostera marina l habitats using a simple and effective transplanting technique
PLOS ONE, 2014Co-Authors: Yi Zhou, Xujia Liu, Peng Liu, Bingjian Liu, Xiaomei Zhang, Feng Wang, Hongsheng YangAbstract:Eelgrass beds in coastal waters of China have declined substantially over the past 30 years. In this study, a simple new transplanting technique was developed for Eelgrass ( Zostera marina L.) restoration. To assist in anchoring single shoots, several rhizomes of rooted shoots were bound to a small elongate stone ( 50-150 g) with biodegradable thread ( cotton or hemp), and then the bound packet was buried at an angle in the sediments at a depth of 2-4 cm. This stone anchoring method was used to transplant Eelgrass in early November 2009 and late May 2010 in Huiquan Bay, Qingdao. The method led to high success. Three month survivorship of the transplanted shoots at the two transplant sites was >95%. From April 20 to November 19, 2012, the following characteristics of the 2009 and 2010 transplanted Eelgrass beds were monitored: morphological changes, shoot density, shoot height, leaf biomass, and sediment particle size. Results showed that the sexual reproduction period of the planted Eelgrass was from April to August, and vegetative reproduction reached its peak in autumn. Maximum shoot height and biomass were observed in June and July. After becoming established, the transplanted Eelgrass beds were statistically equal to natural Eelgrass beds nearby in terms of shoot height, biomass, and seasonal variations. This indicates that the transplant technique is effective for Eelgrass restoration in coastal waters.
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Eelgrass detritus as a food source for the sea cucumber apostichopus japonicus selenka echinidermata holothuroidea in coastal waters of north china an experimental study in flow through systems
PLOS ONE, 2013Co-Authors: Xujia Liu, Yi Zhou, Hongsheng YangAbstract:Eelgrass ecosystems have a wide variety of ecological functions in which living tissues and detritus may be a food source for many marine animals. In this study, we conducted a laboratory simulating experiment to understand the trophic relationship between the Eelgrass Zostera marina L and the sea cucumber Apostichopus japonicus. A mixture of decaying Eelgrass debris and seafloor surface muddy sediments was used as food to feed A. japonicus, and then specific growth rates (SGR) and fecal production rates (FPR) were measured. According to the proportion of Eelgrass debris, we designed five treatment diets, i.e., ES0, ES10, ES20, ES40, and ES100, with Eelgrass debris accounting for 0%, 10%, 20%, 40%, and 100% in dry weight, respectively. Results showed that diet composition had a great influence on the growth of A. japonicus. Sea cucumbers could use decaying Eelgrass debris as their food source; and when the organic content of a mixture of Eelgrass debris and sediment was 19.6% (ES40), a relatively high SGR (1.54%·d−1) and FPR (1.31 g·ind.−1 d−1) of A. japonicus were obtained. It is suggested that Eelgrass beds can not only provide habitat for the sea cucumber A. japonicus but can also provide an indirect food source for the deposit feeder. This means that the restoration and reconstruction of Eelgrass beds, especially in coastal waters of China, would be a potential and effective measure for sea-cucumber fisheries, in respect to both resource restoration and aquaculture of this valuable species.
Jungbae Kim - One of the best experts on this subject based on the ideXlab platform.
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production dynamics of the Eelgrass zostera marina in two bay systems on the south coast of the korean peninsula
Marine Biology, 2005Co-Authors: Kunseop Lee, Sang Rul Park, Jungbae KimAbstract:Production dynamics of Eelgrass, Zostera marina was examined in two bay systems (Koje Bay and Kosung Bay) on the south coast of the Korean peninsula, where few seagrass studies have been conducted. Dramatically reduced Eelgrass biomass and growth have been observed during summer period on the coast of Korea, and we hypothesized that the summer growth reduction is due to increased water temperature and/or reduced light and nutrient availabilities. Shoot density, biomass, morphological characteristics, leaf productivities, and tissue nutrient content of Eelgrass were measured monthly from June 2001 to April 2003. Water column and sediment nutrient concentrations were also measured monthly, and water temperature and underwater irradiance were monitored continuously at seagrass canopy level. Eelgrass shoot density, biomass, and leaf productivities exhibited clear seasonal variations, which were strongly correlated with water temperature. Optimal water temperature for Eelgrass growth in the present study sites was about 15–20°C during spring period, and Eelgrass growths were inhibited at the water temperature above 20°C during summer. Daily maximum underwater photon flux density in the study sites was usually much higher than the light saturation point of Z. marina previously reported. Densities of each terminal, lateral, and reproductive shoot showed their unique seasonal peak. Seasonal trends of shoot densities suggest that new Eelgrass shoots were created through formation of lateral shoots during spring and a part of the vegetative shoots was transformed into flowering shoots from March. Senescent reproductive shoots were detached around June, and contributed to reductions of shoot density and biomass during summer period. Ambient nutrient level appeared to provide an adequate reserve of nutrient for Eelgrass growth throughout the experimental period. The relationships between Eelgrass growth and water temperature suggested that rapid reductions of Eelgrass biomass and growth during summer period on the south coast of the Korean peninsula were caused by high temperature inhibition effects on Eelgrass growth during this season.
Susan L. Williams - One of the best experts on this subject based on the ideXlab platform.
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Native Eelgrass Zostera marina controls growth and reproduction of an invasive mussel through food limitation
Marine Ecology Progress Series, 2003Co-Authors: Bengt J. Allen, Susan L. WilliamsAbstract:In southern California, native Eelgrass Zostera marina L. and the invasive non-native mussel Musculista senhousia have dynamic complex interactions. Although high densities of M. sen- housia inhibit the growth of Eelgrass, mussel survival and growth decline with increasing Eelgrass shoot density and patch size. The correlation of these Eelgrass attributes with local concentrations of chlorophyll a and water flow speeds suggested that the mussels, which feed on phytoplankton deliv- ered by water currents, might suffer food limitation inside large Eelgrass beds. By supplementing phytoplankton to M. senhousia living in Eelgrass, we confirmed this hypothesis: mussels grew 50% faster when food availability was enhanced. Lab and field experiments investigating the effects of food limitation on growth and reproduction of M. senhousia showed that mussels respond by reduc- ing shell growth, and subsequently fecundity. We found no evidence that mussels reallocated resources preferentially to reproduction when food was limited. Our results highlight how the effects of anthropogenic perturbations that currently threaten Eelgrass populations directly could be magni- fied by interactions with a non-native species. Eelgrass habitat fragmentation and increasingly frequent phytoplankton blooms resulting from coastal development and eutrophication have well- described direct negative effects on Eelgrass. By increasing phytoplankton availability to M. sen- housia, such perturbations also indirectly affect Eelgrass by acting to enhance mussel survival and growth, magnifying the negative effects of the mussel on Z. marina.
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reduced genetic diversity in Eelgrass transplantations affects both population growth and individual fitness
Ecological Applications, 2001Co-Authors: Susan L. WilliamsAbstract:The transplantation of Eelgrass (Zostera marina) for mitigation results in reduced genetic diversity among individuals and populations- in southern California, the Chesapeake Bay, and New Hampshire. Although genetic variation determines the potential for Eelgrass to adapt to the rapidly changing environment in its coastal and estuarine habitats, genetic considerations are not currently included in mitigation and restoration policy. I investigated where and how genetic diversity is lost during Eelgrass transplantation. I then explored associations between genetic diversity and both vegetative propagation and sexual reproduction to evaluate the importance of genetic diversity for short-term population growth. Eelgrass beds used as donor populations vary in genetic diversity, and some have little or no detectable genetic diversity. Genetic diversity is reduced upon transplantation because donor plants are collected from small areas, leading to random sampling errors in selecting stock. This loss can be minimized by using information from regional surveys of genetic diversity and structure in potential donor populations and by revising donor stock collection. There were significant positive associations between genetic diversity and the sexual reproduction of Eelgrass, with a similar trend for vegetative propagation. Individuals het- erozygous for glucose-phosphate isomerase (GPI) developed flowering shoots more than did homozygotes. More seeds germinated from a genetically diverse, untransplanted pop- ulation than from a transplanted population with low genetic diversity. A field transplan- tation of known multilocus genotypes revealed that leaf shoot density in high-diversity Eelgrass increased almost twice as fast as in low-diversity Eelgrass over 22 mo. In a me- socosm experiment under heat stress, Eelgrass heterozygous for either GPI or malate de- hydrogenase (MDH) produced almost twice as many leaf shoots as homozygotes. The difference between treatments in all experiments increased over time. Together, these results imply that there could be economic incentives to planting genetically diverse Eelgrass, and that genetic diversity contributes to Eelgrass population viability even over the short term.
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Genetic diversity and structure of natural and transplanted Eelgrass populations in the Chesapeake and Chincoteague Bays
Estuaries, 1998Co-Authors: Susan L. Williams, Robert J. OrthAbstract:The objective of this study was to gain baseline population data on the genetic diversity and differentiation of Eelgrass (Zostera marina L.) populations in the Chesapeake and Chincoteague bays. Natural and transplanted Eelgrass beds were compared using starch gel electrophoresis of allozymes. Transplanted Eelgrass beds were not reduced in genetic diversity compared with natural beds. Inbreeding coefficients (FIS) indicated that transplanted Eelgrass beds had theoretically higher levels of outcrossing than natural beds, suggesting the significance of use of seeds as donor material and of seedling recruitment following transplantation diebacks. Natural populations exhibited very great genetic structure (FST=0.335), but transplanted beds were genetically similar to the donor bed and each other. Genetic diversity was lowest in Chincoteague Bay, reflecting recent restoration history since the 1930s wasting disease and geographical isolation from other east coast populations. These data provide a basis for developing a management plan for conserving Eelgrass genetic diversity in the Chesapeake Bay and for guiding estuary-wide restoration efforts. It will be important to recognize that the natural genetic diversity of Eelgrass in the estuary is distributed among various populations and is not well represented by single populations.
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Variable responses of native Eelgrass Zostera marina to a non-indigenous bivalve Musculista senhousia.
Oecologia, 1998Co-Authors: Thorsten B.h. Reusch, Susan L. WilliamsAbstract:The transport and establishment of non-indigenous species in coastal marine environments are increasing worldwide, yet few studies have experimentally addressed the interactions between potentially dominant non-native species and native organisms. We studied the effects of the introduced mussel Musculista senhousia on leaf and rhizome growth and shoot density of Eelgrass Zostera marina in San Diego Bay, California. We added M. senhousia over a natural range in biomass (0-1200 g dry mass/m2) to Eelgrass in transplanted and established beds. The effects of the non-indigenous mussel varied from facilitation to interference depending on time, the abundance of M. senhousia, and the response variable considered. Consistent results were that mussel additions linearly inhibited Eelgrass rhizome elongation rates. With 800 g dry mass/m2 of M. senhousia, Eelgrass rhizomes grew 40% less than controls in two Eelgrass transplantations and in one established Eelgrass bed. These results indicate that M. senhousia, could both impair the success of transplantations of Eelgrass, which spread vegetatively by rhizomes, and the spread of established Z. marina beds to areas inhabited by M. senhousia. Although effects on leaf growth were not always significant, in August in both Eelgrass transplantations and established meadows leaf growth was fertilized by mussels, and showed a saturation-type relationship to sediment ammonium concentrations. Ammonium concentrations and sediment organic content were linear functions of mussel biomass. We found only small, non-consistent effects of M. senhousia on shoot density of Eelgrass over 6-month periods. In established Eelgrass beds, but not in transplanted Eelgrass patches (≈0.8 m in diameter), added mussels suffered large declines. Hence, Eelgrass is likely to be affected by M. senhousia primarily where Z. marina beds are patchy and sparse. Our study has management and conservation implications for Eelgrass because many beds are already seriously degraded and limited in southern California where the mussel is very abundant.
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Survival and re-establishment of vegetative fragments of Eelgrass (Zostera marina)
Botany, 1996Co-Authors: Patrick J. Ewanchuk, Susan L. WilliamsAbstract:Vegetative fragmentation of clonal aquatic plants is considered a form of asexual reproduction. Although vegetative fragmentation of Eelgrass (Zostera marina L.) is considered a mode of asexual reproduction and dispersal, no data exist to evaluate the potential contribution of fragments (rhizomes with meristems and green leaf shoots) to Eelgrass populations. We estimated (i) the size of the fragment population relative to the size of adjacent Eelgrass populations, and (ii) the potential for fragments to re-establish in Eelgrass beds in Mission Bay, San Diego, Calif. We surveyed the abundance of fragments on adjacent beaches and determined the survival and growth of detached fragments and of fragments re-established in Eelgrass beds after varying time spent in the water column. Although vegetative fragments occurred throughout the year, but mostly in winter, they represented a loss of
David O Rivers - One of the best experts on this subject based on the ideXlab platform.
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effect of grazing by canada geese branta canadensis on an intertidal Eelgrass zostera marina meadow
Marine Ecology Progress Series, 2007Co-Authors: David O Rivers, Frederick T. ShortAbstract:Fishing Island, in Portsmouth Harbor on the Maine-New Hampshire border (USA), is the site of an intertidal Eelgrass (Zostera marina L.) bed that is part of SeagrassNet, an international program for long-term seagrass monitoring. Eelgrass bed parameters of canopy height, percent cover, and aboveground biomass have been monitored quarterly since October 2001 using the Sea- grassNet protocol. A flock of nearly 100 Canada geese Branta canadensis L. over-wintered at Fishing Island and grazed on Eelgrass from January to April 2003, an event that had not been seen at this meadow in 2 decades of observation. Before Canada geese were present, Eelgrass parameters demonstrated seasonal fluctuations typical of the region. During the grazing event, Eelgrass parame- ters declined drastically, and biomass losses reached 680 g m -2 in parts of the meadow. SeagrassNet data demonstrated that Eelgrass did not recover after the geese departed. Additional fieldwork con- ducted from February to July 2003 showed that Eelgrass recruitment via sexual reproduction at Fish- ing Island was minimal, and vegetative recovery was impeded by Canada goose consumption of the plant meristems. Unlike studies in other locations, which show seagrass quickly rebounding from annual grazing events, Eelgrass at Fishing Island showed little recovery from Canada goose grazing through July 2003.