1. Why are PEARL data divided into two broad groupings: “Lakes & Streams” and “Wetlands, Estuaries, Coastal & Terrestrial”?
The reason for this system of grouping data tables relates to the way in which PEARL data are spatially referenced. Lakes and streams data are referenced to individual waterbodies. All lakes data are identified by the MIDAS lake code (Moosehead Lake, for example, is 0390) – a system that was established by DEP and IF&W many years ago. Streams data are geo-referenced to individual stream segments using codes derived from the National Hydrographic Dataset (NHD: http://nhd.usgs.gov/). Internal lookup tables in the PEARL system link each MIDAS lake code or NHD stream segment to their landscape context: watershed (the series of nested hydrologic units developed by USGS: HUC-8, HUC-10 and HUC-12), town and county. These linkages allow PEARL users to search for data by watershed or by town/county, in addition to waterbody name or code.
In contrast to lakes and streams data, all other data types in PEARL are spatially referenced only by unique combinations of town and watershed (HUC-12). This spatial referencing system also allows the user to search for, and extract, data using either watershed or political boundaries.
2. Why are there more lakes and streams data in PEARL than wetlands, estuarine, coastal and terrestrial data?
This is simply a time issue. PEARL started about 8 years ago as an on-line forum for serving lakes data. Modifications to PEARL’s internal architecture that now enable other data types to be served on PEARL have been made only in the past 1-2 years. Now that these capabilities are in place, PEARL users will see an increasing number of both lake and non-lake data displayed on the site.
3. I am looking for information on fish and freshwater mussels in Maine. On PEARL’s home page, should I go to DATA or to FOCUS TOPICS > Freshwater Biodiversity?
It depends on how much background and other information you are looking for. Both avenues will lead to PEARL’s fish and mussel core data tables – for example IF&W’s mussel and lake fish surveys. However, the Freshwater Biodiversity pages provide supporting information and topic overviews that are not found in the DATA pages. Here are 4 examples of the options available to you:
1. You want to find out what fish and mussel data sets are available in PEARL.
Do this: PEARL Home > Data > Browse Data Sets > Fauna under either Lakes & Streams or Wetlands etc. This displays all of the relevant data set titles in the PEARL Data Bank. Opening any table will display the full data set.
2. You are only looking for summary species lists for a lake or a watershed.
Take this route: PEARL Home > Data > Search by Lake or Search by Watershed. Once the lake or watershed overview page displays, simply click on the Fish or Mussel button to generate a species list. Note that this list is generated dynamically once you click the button – thus it always reflects the most current data in the PEARL Data Bank.
3. Rather than a summary species list, you want to see all of the fish or mussel data for that lake or watershed.
In the lake or watershed overview page, scroll down until you see the Fauna icon (a picture of a loon); click on this icon to display the fauna tables; then select a table to open. In this case, since you have already selected the lake or watershed, PEARL automatically extracts and displays only those data records that derive from the area of interest.
4. You want to find a list of all PEARL data sets that contain fish information.
While you could Browse through all Fauna data titles, a more direct approach is: PEARL Home > Data > Search by Topic > Fauna > Fish.
5. You are looking for species distribution maps and other background information about Maine’s fish and mussel species.
Take this route: PEARL Home > Focus Topics > Freshwater Biodiversity. From the Biodiversity home page, select a taxonomic group and then the type of information you are looking for.
4. I want to know more about where PEARL data come from and how the information was collected.
Each data set in the PEARL Data Bank has metadata – background information about the data. Access the metadata by clicking on the “About the Data” button at the top left of the data table. PEARL metadata are always presented in the same format and include such information as: (i) who provided the data; (ii) their contact information; (iii) a map of data collection locations; (iv) time period of data collection; (v) descriptions of each of the parameters in the data table. Before using PEARL data, always read the metadata!
5. Who provides data to PEARL?
PEARL currently hosts data from state and federal agencies, NGOs, university researchers, students and other individuals. Anyone with quality data can host their information on PEARL. Data providers may send their data to the PEARL team for upload. Alternatively, with password access and basic training, providers can upload data themselves from their own computer and then configure the on-line appearance of those data tables. Similarly, providers themselves can update their tables at any time - and even remove their data entirely from PEARL. If you have data that you would like to see made available to anyone in the world with internet access, please contact Peter Vaux.
6. Do PEARL data have to address certain topics?
No. PEARL accepts any type of environmental data from Maine. Data can be contemporary or historical, but should be geo-referenced. All data sets are tagged by information category (e.g. water quality, fauna, etc) and so are automatically sorted and displayed within the appropriate information grouping.
7. How can I evaluate the quality of the different data sets in PEARL?
Our policy is to add data to PEARL only if these data appear to be of reputable quality and if they are supported by metadata (information about how the data were collected, field sampling protocols, analytical methodologies, etc.). Nevertheless, PEARL data sets are not uniform. They come from studies with different designs, different questions that were addressed and different levels of “sophistication”. The metadata contain the key information that is needed to be able to fully interpret the data themselves. Click on the “About the Data” button at the top of each data table. For additional information, you should always consult the data provider and/or the reference(s) indicated in the metadata.
8. Some of the lake water quality data tables include a “station” field. How can I find out where each station is located in the lake?
Open the lake’s depth map from the Lake Overview and Data Access page. These bathymetric maps generally include the location(s) of the sampling station(s). Note that we are currently working with DEP to re-design their lake water quality narratives. The re-designed narratives will include an index map that shows the sampling stations, in addition to providing a direct link to the full bathymetric map.
