Factors controlling nitrogen fixation in temperate seagrass beds

2015 ◽  
Vol 525 ◽  
pp. 41-51 ◽  
Author(s):  
PLM Cook ◽  
V Evrard ◽  
RJ Woodland
Keyword(s):  
Nitrogen Fixation ◽  
Seagrass Beds

scholarly journals Negligible isotopic fractionation of nitrogen within temperate <i>Zostera</i> spp. meadows

2018 ◽  
Author(s):  
Douglas G. Russell ◽  
Wei Wen Wong ◽  
Perran L. M. Cook
Keyword(s):  
Nitrogen Fixation ◽  
Coastal Zone ◽  
Solid Phase ◽  
Isotopic Fractionation ◽  
Nitrogen Isotope ◽  
Small Contribution ◽  
Seagrass Beds ◽  
Seagrass Meadows ◽  
Nitrogen Inputs ◽  
External Sources

Abstract. Seagrass meadows form an ecologically important ecosystem in the coastal zone. Excessive nitrogen inputs to the coastal zone pose a key threat to seagrass through eutrophication and associated algal overgrowth. The 15N / 14N ratio of seagrass is commonly used to assess extent to which sewage derived nitrogen may be influencing seagrass beds. There have however, been no studies comparing the 15N / 14N ratios of seagrass beds, their associated sediments and of critical importance, the porewater NH4+ pool, which is most bioavailable. Here, we undertook a study of the 15N / 14N ratios of seagrass tissue, sediment porewater NH4+ pool and the sediment solid phase to elucidate the extent of any fractionating processes taking place during organic matter mineralisation and nitrogen assimilation. The study was undertaken within two coastal embayments known to receive nitrogen from a range of sources including marine, urban and sewage sources. The δ15N of porewater ammonium was strongly correlated with the δ15N of both the sediment solid phase and seagrass tissue (r2 of 0.89 and 0.85) respectively. The δ15N porewater NH4+ minus the δ15N seagrass tissue ranged between −1.4 and 7 ‰ with an average 1.6 ‰. We suggest the most likely explanation for this was fractionation during assimilation as a consequence of diffusion limitation, although the magnitude of this change was relatively small. Nitrogen fixation may have also contributed a small amount to the observed isotopic depletion of the plants relative to the sediment porewater NH4+ pool. A consideration of the nitrogen isotope values of the seagrass bed nitrogen pools compared to external sources suggest the dominant source of nitrogen to seagrass is recycling from within the bed, with a relatively small contribution from water column assimilation, particulate trapping and nitrogen fixation.

scholarly journals Nitrogen Fixation in Subtropical Seagrass Sediments: Seasonal Patterns in Activity in Santa Rosa Sound, Florida, USA

2021 ◽  
Vol 9 (7) ◽  
pp. 766
Author(s):  
Rachel Presley ◽  
Jane M. Caffrey
Keyword(s):  
Organic Matter ◽  
Nitrogen Fixation ◽  
Organic Matter Content ◽  
High Growth ◽  
Matter Content ◽  
Seasonal Patterns ◽  
Seagrass Beds ◽  
Halodule Wrightii ◽  
Substrate Types ◽  
Nitrogen Demand

Seagrass beds are important coastal habitats that are diminishing globally. Nitrogen, a key nutrient, often limits seagrass growth. Nitrogen fixation provides new, bioavailable nitrogen to the plants. This study explores its importance and factors controlling rates in sediments colonized by two dominant taxa in Northwest Florida, Thalassia testudinum and Halodule wrightii, compared to unvegetated sediments. We hypothesized that nitrogen fixation rates would be greater in seagrass colonized sediments, particularly during high growth periods. We expected to observe a positive relationship between rates and porewater sulfide concentrations because sulfate reducers were the dominant diazotrophs in similar studies. Rates were higher in vegetated areas. In H. wrightii beds, nitrogen fixation was driven by the decreased availability of porewater ammonium relative to phosphorus. In T. testudinum beds, rates were highest during winter. Organic matter may be a controlling factor in all substrate types albeit the exact mechanism driving nitrogen fixation differs slightly. During the summer and fall, nitrogen fixation provided between 1–15% of T. testudinum nitrogen demand. Annually, nitrogen fixation provided 4% and 1% of T. testudinum and H. wrightii nitrogen demand, respectively. Nitrogen fixation was an important source of nitrogen during periods of senescence and dormancy when organic matter content was high.

Pemetaan Pulau Kecil Gelasa Kabupaten Bangka Tengah

2019 ◽  
Vol 2 (1) ◽  
pp. 11-14
Author(s):  
Wahyu Adi
Keyword(s):  
Coral Reefs ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Image Interpretation ◽  
Vegetation Coverage ◽  
Small Island ◽  
Shallow Waters ◽  
Small Islands ◽  
Seagrass Beds ◽  
Cover Density

Pulau Kecil Gelasa merupakan daerah yang belum banyak diteliti. Pemetaan ekosistem di pulau kecil dilakukan dengan bantuan citra Advanced Land Observing Satellite (ALOS). Penelitian terdahulu diketahui bahwa ALOS memiliki kemampuan memetakan terumbu karang dan padang lamun di perairan dangkal serta mampu memetakan kerapatan penutupan vegetasi. Metode interpretasi citra menggunakan alogaritma indeks vegetasi pada citra ALOS yaitu NDVI (Normalized Difference Vegetation Index), serta pendekatan Lyzengga untuk mengkoreksi kolom perairan. Hasil penelitian didapatkan luasan Padang Lamun di perairan dangkal 41,99 Ha, luasan Terumbu Karang 125,57 Ha. Hasil NDVI di daratan/ pulau kecil Gelasa untuk Vegetasi Rapat seluas 47,62 Ha; luasan penutupan Vegetasi Sedang 105,86 Ha; dan penutupan Vegetasi Jarang adalah 34,24 Ha.   Small Island Gelasa rarely studied. Mapping ecosystems on small islands with the image of Advanced Land Observing Satellite (ALOS). Previous research has found that ALOS has the ability to map coral reefs and seagrass beds in shallow water, and is able to map vegetation cover density. The method of image interpretation uses the vegetation index algorithm in the ALOS image, NDVI (Normalized Difference Vegetation Index), and the Lyzengga approach to correct the water column. The results of the study were obtained in the area of Seagrass Padang in the shallow waters of 41.99 ha, the area of coral reefs was 125.57 ha. NDVI results on land / small islands Gelasa for dense vegetation of 47.62 ha; area of Medium Vegetation coverage 105.86 Ha; and the coverage of Rare Vegetation is 34.24 Ha.

Commercial trawling in seagrass beds: bycatch and long-term trends in effort of a major shrimp fishery

2014 ◽  
Vol 513 ◽  
pp. 143-153 ◽  
Author(s):  
CD Stallings ◽  
JP Brower ◽  
JM Heinlein Loch ◽  
A Mickle
Keyword(s):  
Seagrass Beds ◽  
Shrimp Fishery ◽  
Long Term Trends

NEW CLOVER CULTIVARS FOR WAIKATO DAIRY PASTURE: ESTABLISHMENT, PRODUCTION AND NITROGEN FIXATION DURING THE FIRST YEAR

1988 ◽  
pp. 207-211
Author(s):  
S.F. Ledgard ◽  
G.J. Brier ◽  
R.N. Watson
Keyword(s):  
Nitrogen Fixation ◽  
White Clover ◽  
Dairy Cow ◽  
Red Clover ◽  
First Year ◽  
Buried Seed

Clover cultivars grown with ryegrass were compared in an establishment year under dairy cow grazing. There was no difference in total annual productton but summer production was greater with Pawera red clover and with Kopu or Pitau white clovers. Clovers differed little in the proportion of nitrogen fixed, except during summer when values were highest for Pawera. Pawera was less prone to nematode attack than white clover cultivars but was more susceptible to clover rot. Resident clovers and high buried seed levels (e.g., 11-91 kg/ha) made introduction of new clover cultivars difficult. Sown clovers established best (50-70% of total clover plants) when drilled into soil treated with dicamba and glyphosate. Keywords: white clover, red clover, nematodes. nitrogen fixation, pasture renovation

A Study on the Farmers’ Awareness and Acceptance of Biofertilizers in Kottayam District

GIS Business ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. 425-431
Author(s):  
Subin Thomas ◽  
Dr. M. Nandhini
Keyword(s):  
Organic Matter ◽  
Nitrogen Fixation ◽  
Plant Growth ◽  
Plant Growth Promoting Rhizobacteria ◽  
Nutrient Cycle ◽  
Plant Growth Promoting ◽  
Promote Plant Growth ◽  
Growth Promoting ◽  
Structured Questionnaire ◽  
Area Data

Biofertilizers are fertilizers containing microorganisms that promote plant growth by improving the supply of nutrients to the host plant. The supply of nutrients is improved naturally by nitrogen fixation and solubilizing phosphorus. The living microorganisms in biofertilizers help in building organic matter in the soil and restoring the natural nutrient cycle. Biofertilizers can be grouped into Nitrogen-fixing biofertilizers, Phosphorous-solubilizing biofertilizers, Phosphorous-mobilizing biofertilizers, Biofertilizers for micro nutrients and Plant growth promoting rhizobacteria. This study conducted in Kottayam district was intended to identify the awareness and acceptance of biofertilizers among the farmers of the area. Data have been collected from 120 farmers by direct interviews with structured questionnaire.

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