3.5 Broader applications and considerations
The methods we present are relevant and applicable to temporary lentic habitats in a wide range of regions, particularly where logistical challenges constrain the data available for hydroperiod monitoring. For example, temperature sensor-derived hydroperiod inference may be particularly useful for ponds or wetlands that can have high canopy cover (e.g., some Carolina bays (Sharitz, 2003) or vernal pools (Brooks, 2004)) or other considerations that may make remote sensing difficult, particularly across multiple sites. Temperature sensors may also be helpful in regions where drone activity is discouraged or prohibited, thus limiting targeted, fine-scale aerial data acquisition. This includes national parks, wildlife sanctuaries, or areas where drone flight is otherwise prohibited (for example, drone operation is not logistically feasible in our study region due to restrictions by the United States Border Patrol). Our proposed methods are relatively low-cost and low-maintenance, making them accessible for even small-scale research grants. The long battery life of the sensors and high durability of the design make them ideal for deploying in remote areas. However, we suggest that users visit deployment sites at least once a year, particularly before major seasonal inundation events.
Some scenarios may necessitate modifications to the current design, including components and deployment. For example, complex bathymetry of wetlands may call for the use of more than one temperature sensor to detect hydroperiod inundation, particularly when distinct areas of the temporary habitat have meaningful ecological differences (Chandler, 2017). If longer battery life is desired, the temporal resolution of measurements could also be adjusted to capture temperature data in less frequent intervals. Additionally, users may consider alternative sensor designs. For example, conductivity sensors offer an alternative to temperature loggers. However, custom modifications required to create conductivity sensors can be time-consuming or, if outsourced, may result in units that are >2 times the cost of temperature loggers. Additionally, conductivity sensors may suffer from the same issues related to poor or imprecise detection of drying patterns due to water trapped in sediments. Temperature measurements offer data that are biologically meaningful (temperature as well as presence/absence of water) and that may address multiple needs depending on the objectives of a study. Pressure transducers would likely capture drying dynamics more accurately and are available for as low as ~$300 per sensor (e.g., Onset HOBO Water Level Data Logger, U20L-01). However, the physical dimensions of pressure transducers would require modifications to the current rugged housing unit design, and the additional cost would result in approximately a four-fold reduction in the number of sensors obtained for the same budget. An additional consideration is the ability of sensors to withstand extreme temperatures. The temperature sensors in our design have a range of -20 to 50°C in water; anticipated temperatures outside this range would likely necessitate a different sensor model and may be an important consideration for high-latitude study regions. Finally, deployment methods for the housing unit and sensor may need to be modified depending upon the substrate of the habitat. For example, mud or other soft sediment may require a T-post or similar support structure rather than buried concrete ties depending upon the depth of the soft substrate.