Record Search Query:[Parameters: Topic='TERRESTRIAL HYDROSPHERE', Term='WATER QUALITY/WATER CHEMISTRY', Variable_Level_1='NUTRIENTS']
The ecology (tidal and weather records, distribution and abundance of microbes and quantification of nitrogen transformation) of an Antarctic tidal lagoon and mudflats at Bratina Island, McMurdo Ice Shelf
A tidal lagoon at Bratina Island experiences a daily inundation with tidal height varying. Low tide reveals a network of ponds, streams and tidal flats that appear to be highly productive with all but the highest intertidal flats colonised by flora of diatoms and cyanobacteria. The tidal lagoon environment and microbial communities was described. The rate of primary production within the ... communities, the effects of tidal cycles on this process and quantification of nitrogen transformations within the lagoon system was investigated. A sketch map was drawn of the lagoon and photos were taken to characterise the area. A tide gauge was installed to provide a near continuous tidal record. An automatic weather station (air temperature, relative humidity, total and net radiation, wind speed and direction and UV-A and UV-B radiation) was installed close to the lagoon inflow/outflow region. In addition, this station logged temperatures of five thermistors in selected locations within the lagoon system. The effects of prolonged aerial exposure on salinity and water content in intertidal sediments was monitored with sediment cores being analysed for water content, salt content, dry weight and conductivity. Spatial and temporal variability in pond and stream water including diel changes were monitored at different depths by measuring temperature, pH, conductivity, dissolved oxygen, nutrient analysis, NO3, NH4, dissolved organic nitrogen, dissolved reactive phosphorus and dissolved organic phosphorus. The algae distribution and abundance was measured by collecting samples from several habitat types for determination of algal species composition, microscopic identification, analysis of dry and ash-free dry weight, and particulate carbon, nitrogen and phosphorus. Chlorophyll a was measured for biomass determination and for pigment analysis. To relate algal distribution and abundance to tidal height, a number of transects were established across the lagoon. Photosynthetic rates of submerged and benthic algal communities were carried out along with experiments in situ for effects of radiation flux, desiccation, salinity and de-nitrification.
All reasonable efforts have been made to remove data affected to any degree by questionable observational conditions, however questionable data likely are still present. Here are the currently-identified issues with the LVIS dataset:
Canopy height bias.
1. Low-lying ground fog was present in some areas (swamps, river valleys etc). This will cause canopy height parameters ... (zt, rh25, rh50, rh75) to be higher than in reality.
2. Canopy return misselected during data processing. Weak canopy top returns or spurious higher-amplitude background noise samples were misselected during data processing.
3. Misselected ground return. Obviosuly, if the ground location has been misselected then canopy height products will be biased. Data product zc is unaffected since its elevation is relative to the eliposoid, not the ground.
Ground elevation bias.
1. Ground return is not contained within the waveform and thus cannot be identified.
2. Ground return misselected during data processing, caused by:
- A mode from a higher reflecting layer within the canopy was misselected as the ground return. This misselection usually implies the ground reflection is "weak" (i.e., contains only a small proportion of the reflected energy from the footprint as a whole) and thus has been "overlooked" by the interpretation algorithm.
- Spurious, higher ampitude background noise was misselected as the ground return. Noise due to aircraft operations (radio operations) was a problem during the New England mission.
3. Ground return is indistinct, i.e., the lowest reflection has become convolved with reflections from higher surfaces. This effect is compounded by within footprint slope and surface roughness.
Improvements in our methods of waveform interpretation will enable better data accuracy. Digitally recording the shape of the return laser pulse means that these improvements can easily be applied.
While substantial efforts have been made to ensure the accuracy of data and documentation, complete accuracy of data sets can not be guaranteed. All data are made available "as is". The LVIS team can not assume responsibility for damages resulting from mis-use or mis-interpretation of datasets or from errors or omissions that may exist in the data. Data users are welcome to collaborate with the ... LVIS team, as this may minimize the potential for misinterpretation of the data.
In order to develop an active community and ensure the flow of ideas between interested parties, the LVIS team makes the following suggestions of individuals who download LVIS data:
- On projects that are integrally dependent on LVIS data, you have the option to request collaboration and/or co-authorship from the LVIS team. (NOTE: This is in no way binding. You are free to use the data on your own. You are not expected or required to contact or work with us in any way. This is simply a suggestion.)
- Please acknowledge the source of the data set as the LVIS team/ project and the appropriate NASA Grant numbers responsible for funding these data sets in any publications using these data and documentation (see LVIS Citations)
- Consider notifying (a simple email will suffice) the LVIS Principal Investigator when any derivative work based on or derived from the data and/or documentation is distributed or presented. (We always appreciate when our data is used and helps result in scientific publications.)
- When derivatives of the LVIS data are distributed in any way, notify subsequent users that such derivative work is not the original LVIS data and/or documentation distributed on the LVIS web site.
- Do not redistribute original data and documentation yourself, instead please direct individuals to http://lvis.gsfc.nasa.gov. It is important that we have the ability to contact users of LVIS data so that we can notify them when we upload new data sets and/or correct mistakes in the existing data sets.
- If you would like to share your work with us, we would greatly appreciate it if you would notify us and/or send a reprint of any publications resulting from the use of the data and/or documentation.
See data use at the project home page.
NASA Goddard Space Flight Center
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J. B. Blair, D. L. Rabine, and M. A. Hofton, The Laser Vegetation Imaging Sensor (LVIS): A medium-altitude, digitization-only, airborne laser altimeter for mapping vegetation and topography, ISPRS Journal of Photogrammetry and Remote Sensing, 54, 115-122, 1999.
Processing of NASA LVIS elevation and canopy (LGE, LCE and LGW) data products, version 1.01. J. B. Blair, M. A. Hofton, and D. L. Rabine. http://lvis.gsfc.nasa.gov, 2006.