Kaitlyn Peters edited Methods.tex  about 9 years ago

Commit id: 9998122728efe7efd4794cb93f21c86de77df538

deletions | additions      

       

\section{Incubation Experiment}  Samples for the experiment were collected from Lancer Park Pond, a stormwater collection pond in Farmville, VA. The pond has a surface area of ~0.06 ha and a maximum depth of 1.5m. Field sediment samples were collected from the littoral zone at depths of 1m and 0.4m. on May 29, 2014, using an Ekman-Dredge. The sediments were sieved through a 250 µm mesh net and retained in buckets. Since, by definition, a “macroinvertebrate is any invertebrate that is 250 µm or larger,” the mesh net effectively eliminated macroinvertebrates from our sediment samples. The 1m and 0.4m sieved sediment slurry was combined and allowed to settle overnight. Overlaying water could then be siphoned off. The CPOM retained by the net was placed into 1 liter bottles. The retained CPOM would later be used to to determine the CPOM density of Lancer Park Pond and to give an estimate of the amount of CPOM to add to our BOD bottles.  Once back at the lab, the 1m and 0.4m sieved sediment slurry was combined and allowed to settle overnight. Overlaying water could then be siphoned off. 10ml sediment samples were taken and placed into pre-weighed crucible, dried, and then ashed at 550 degrees Celcius. The contents of the 1 Liter bottles were also rinsed through a 1mm sieve and visible macroinvertebrates were removed. All retained material was placed into pre-weighed paper bags. The bags were then placed in a drier at 50 degrees Celcius. Once dry, the CPOM was weighed and ashed at 550 degrees Celcius to determine ash free dry mass (AFDM). The AFDM was used to determine the amount of CPOM, in this case leaf disks, needed to add to the BOD bottles. The organic matter content of the leaf disks was determined by randomly selecting 5 senescent tulip poplar leaves that were collected from fall 2013. Each leaf was gently submerged in DI water until it was soft enough to core (about 5 min). A single leaf disk (10mm, #5 cork borer) was cut from the leaf blade avoiding the midrib. The disk was placed into a pre-weighed crucible and dried at 50 degrees Celcius, then ashed at 550 degrees Celcius.  An initial water analysis was performed on the water collected to give a nutrient baseline for the ambient replacement water. Dr. Dina Leech filtered 50 ml of the collected pond water through the GFF and utilized Hach test kits to measure nitrate, nitrite, ammonia, and orthophosphate levels in the ambient water. N was tested using Hach Test Kit N1-12 (cat# 14081-00) using the provided instructions. Detection limits were <8.8 mg/L* for Nitrate, <0.066mg/L for Nitrite, <0.2 mg/L for Ammonia, <0.2 mg/L for Orthophosphate. The nutrient enriched water that was used for nutrient treatment BOD bottles had a target of 300um NH4NO3 and 30 um of KH2PO4.  * This number needs to be corrected.