3. Survey Types and Site Selection: Tutorial 3 describes the two types of shoreline surveys and the things to consider when selecting a shoreline survey site.
Survey Types and Site Selection Transcript
• This “survey types and site selection” presentation is the third of six brief tutorials to guide you through everything you need to know about the MDMAP before getting started. In this presentation, we will discuss the two types of shoreline surveys and the things to consider when selecting a shoreline survey site.
• The first consideration when deciding how to select your shoreline monitoring site location is to determine which of the two MDMAP survey protocols you will be following. MDMAP survey sites are either standing stock OR accumulation survey sites, a determination which is usually made by the volunteer lead or program coordinator. Shoreline sites can’t be a mix of both types, and one protocol should be selected at the outset and used throughout the study. Let’s review the similarities and differences between standing stock and accumulation surveys. For a more thorough overview, make sure to go back and take a look at the Shoreline Survey Field Guide. First, both protocols require that you are out in the field for a survey every 28 days plus or minus three days, and both protocols are only used to record data on debris items longer than 2.5 cm in the longest dimension, about the size of a bottle cap. During standing-stock surveys, debris is not removed from the shoreline site and only 1/5th of the total survey area is covered, so surveys can be completed in a shorter amount of time. Standing stock surveys take a little longer to set up, but once you get going they are quicker than accumulation surveys. Accumulation surveys have a more straightforward protocol, but because the full area needs to be surveyed and all debris larger than 2.5 cm is picked up and removed from the shoreline, they tend to take up more time.
• During accumulation surveys, all debris items larger than 2.5 cm in the longest dimension are tallied on data sheets, removed, and disposed of. The surveys can take a significant amount of time depending on the width of the shoreline, as the entire length of the site must be surveyed. The crosshatched area shown here represents the area that must be surveyed. Accumulation surveys require initial clearing of all items larger than 2.5 cm from the site, followed by monthly surveys and removal. This provides an estimate of the net flux of debris onto the shoreline or debris deposition rate, in units of number of items per square meter per day. Note that debris deposition rates will vary over the course of time between surveys, and the calculated flux is only an estimate.
• During standing stock surveys, only one-fifth, or 20%, of the shoreline site is surveyed. The surveyed area is within four randomly-selected transects, such as shown the crosshatched area in the example here. Debris items found within the transects are tallied on datasheets, but are left on the shoreline. As with accumulation surveys, only items larger than 2.5 cm in the longest dimension are recorded. Standing stock surveys are quicker than accumulation surveys, as less area is covered and debris items don’t need to be removed. For standing-stock surveys, each survey event is a snapshot of the concentration of debris at the site, in terms of # of items per square meter. A series of these snapshots over time provides information on changes in the baseline or reference concentration of debris at that location. In standing stock surveys, the measured debris concentration reflects the long-term balance between inputs and removal of debris from the site, which helps us evaluate the long-term, cumulative impacts of debris. Debris cannot be removed from the shoreline site during standing stock surveys to maintain the integrity of the study objectives. This can be hard for some to accept, but leaving the debris on the shoreline allows for analysis of changes in debris concentrations over time, which is important information for the research community.
• The major driver in determining what type of survey you select and your site selection are your study objectives. Accumulation surveys tell you how much debris is being deposited on a beach over a given time period. If your objective is to determine how the composition or amount of debris deposited on a beach changes over time, you would use an accumulation survey to assess debris flux. Standing-stock surveys tell you how much and what types of debris are present on the shoreline, and how the debris load changes over time. If your objective is to determine what time of year debris loads are highest, or how debris loads are changing over the course of many years, you would use the standing-stock survey protocol to assess debris concentrations.
• As mentioned, your site selection will primarily depend on your study objectives. For example, if your study is focused on offshore sources of marine debris, you don’t want to choose a site near a river mouth or stormwater outfall. It’s also important to consider any impact your surveys may have on the local environment. Do not conduct surveys in nesting areas or critical habitat for endangered or protected species. Local land managers and agencies can help you determine an appropriate location for your survey site, and should always be contacted during the site selection process. In many cases, permits or other special permissions may be required. Review the protocol documents in the Get Started Toolbox for a complete list of ideal shoreline site characteristics. Sites should have a sandy or pebble shoreline, allow for direct, year-round access, not contain breakwaters or jetties, and have limited or no regular cleanup activities. Sites should also be at least 100m parallel to the water’s edge, as shown in the figure here. Online mapping tools can be helpful for identifying access points, human interest points, piers, and breakwaters, but local knowledge is the most useful tool in identifying a good survey site. Depending on your location and objectives, you may want to consider selecting more than one 100-m site along a given stretch of shoreline. Once you’ve selected a survey type and shoreline site location, you’re ready to complete the shoreline characterization and begin your surveys!