BIO 460 - Class / Group Project
Introduction:
Several studies show that calcium and phosphate ions react in the presence of certain other conditions, particularly high pH, to cause precipitation of calcium compounds and adsorption or complexion of phosphate with them. In some cases, lime (calcium carbonate) has been used as a treatment for excess phosphate concentrations that would otherwise stimulate primary producers.
We will examine the effects of lime additions on phosphate availability and phytoplankton growth by conducting a set of replicated mesocosm experiments. Mesocosms are large vessels that hold enough water to allow larger scale manipulations, more complicated biological responses, and longer and more detailed sampling. Although they are not exact recreations of natural ponds, they come close and permit effective replication and manipulation.
Methods and Materials:
We will set up 6 mesocosm tanks outside the greenhouse. Each tank will be filled nearly full with city tap water, then aerated overnight to allow degassing of chlorine that is routinely added to it. The following morning we will add raw water from "Lake Leutze" and various treatments, with two tanks receiving each kind of treatment. One set of tanks will receive added macronutrients (100 ml each of nitrate, phosphate, and silicate solutions). Another will receive the same nutrients plus 200 g of powdered commercial grade lime. Another set will serve as controls and will receive only distilled water (300 ml). These additions will be repeated approximately every two days (Monday, Wednesday, and Friday staring on Nov. 14 and running through Nov.24).
We will divide into our four groups for the major tasks. These tasks will be grouped as follows:
Each measurement and sampling effort should be repeated on the same days as nutrient/lime additions take place, ideally before the actual additions, which should include stirring with a paddle or bucket. All samples should be collected from each tank in triplicate, i.e., 3 SRP + 3 TP, 3 TSS, or 3 Chl a. The responsible groups should secure everything they need to execute their tasks before they have to get started. Some samples may be filtered and/or frozen for later analysis, while others must be processed immediately. Sampling should continue through the entire experimental period, including a sample collected after the last manipulation on Nov. 24. Each group has responsibility for conducting the appropriate assays, data collection, and presentation. The week after Thanksgiving should be used for sample analyses; we will have only one lab period after the holiday, and may need to use that time for lab work, with a class period for data presentation.