One of the amazing aspects about IITF is its long-standing partnership with the Luquillo LTER program, where collaborations are in place covering different aspects of the Luquillo Experimental Forest (LEF) within the El Yunque National Forest managed by USFS. Between IITF and LTER various streams across the LEF are visited and sampled weekly for multiple parameters of stream chemistry. The Luquillo LTER has one of the longest and continuous records of tropical stream chemistry starting in the 80’s! Amongst the many parameters is dissolved organic carbon (DOC) that generally comes from all the leaf litter (also called organic matter) that falls into streams and undergo different processes in the water.
These leaves are shredded by the shrimp and other macroinvertebrates (freshwater bugs that we can see with our eyes), some leaves are broken down due to physical processes as they are transported down river, and leaves also start to decompose in the water and release different solutes that become dissolved in the water such as DOC. The release of solutes, or leaf leaching process, is similar to steeping a bag of tea in water; the water gains properties and changes color as all the tea leaves releases different solutes. But why are DOC or leaves important? Leaves themselves, are an important food source for shrimp and macroinvertebrates. DOC is an important food or energy sources for the microbial communities that drive many of the biological processes occurring in freshwater ecosystems. Collectively, between DOC, leaf litter broken down by shrimp and microorganism, they sustain the different carbon and nutrients cycles in streams. One of the data sets that I am analyzing is the collection of leaf litter that falls into streams with the goal of understanding the timing, magnitude, and drivers of leaf litter. The data consists of leaf litter baskets in three different parts of a stream to quantify the inputs of litter that fall from trees (vertical baskets), leaves that would come from land or hills slopes (lateral baskets) and leaves that are being delivered from upriver (submerged baskets). The baskets were set up in 2016 and have been visited every two weeks and is an ongoing project. The content of these different baskets are collected every two weeks, taken to a lab to dry, categorized (wood, leaf, miscellaneous, etc.) and weighed. All this work is done in partnership with the Stream Flow Reduction Experiment (StreamFRE) within the Luquillo LTER program. The weights from the different baskets over time provide long-term detailed information of leaf litter delivery to streams to better understand the factors that influence the biological processes and fauna in streams.