The Physical and Chemical Dynamics of the Water Column Under the Influence of Different Primary Producers in Prospect Park Lake
Majid is an Earth and Environmental Sciences PhD student at CUNY. He has a background in the physical, chemical, and engineering sciences. He is an environmental scientist specializing in aquatics research. He is currently studying the physical and chemical dynamics of an urban shallow lake dominated by three different primary producers. He hopes to understand how these primary producers affect the water column with the aim of combating harmful algal blooms. He also uses computational models to further understand the lake’s dynamic properties.
An understanding of the physiochemical changes caused by different primary producers in a shallow lake is important in order to understand its local and global effects in terms of both water quality and carbon exchange with the atmosphere. Furthermore, NYC urban shallow lakes are plagued with harmful algal blooms. Understanding the physiochemical properties of this type of lake will aid in controlling these blooms and restoring a healthy lake ecosystem. This project involves the sampling, measuring, and analysis of water quality parameters at different locations in the Prospect Park Lake. These parameters elucidate the changes in various physical and biogeochemical processes that a shallow lake undergoes. Weekly or biweekly data was collected throughout the summer for the following parameters: dissolved oxygen, pH, temperature, chlorophyll a, light penetration, conductivity, and nutrient concentrations.
With the support of this fellowship, I was able to finally begin my year-long data collection project for my dissertation to observe the changes that an urban shallow lake undergoes throughout the seasons influenced by different primary producers. Our samples were collected on a weekly or bi-weekly basis from May to the present and will continue until next summer or beyond. We measured temperature, pH, conductivity, and dissolved oxygen using a YSI professional plus device (which is a handheld unit with probes to measure each of those parameters). The parameters were measured at 20cm depth intervals for a total depth of 120 cm at three different locations on the lake. Each of these locations was chosen because of the potential of different primary producers that grow in these locations. Cyanobacteria (phytoplankton) grows at all of the sites. However, at the first and second sites, we have duckweed and ludwigia/lily pads, respectively, as the dominant species. Each of these species interacts with the water column differently, and they cause varying changes to occur. One example is that the duckweed grows on the surface of the water, blocking light and preventing diffusion across the interface.
At each of the sites we also collect water samples to measure the level of chlorophyll a and nutrients. The sample water was collected at three different depths (surface, middle, and bottom). Chlorophyll a is an indirect way of measuring the concentration of phytoplankton/cyanobacteria in the water. Nutrient analysis, which is a time-consuming process, involves measuring the concentration of phosphorus in the form of orthophosphate and/or total phosphorus and nitrogen in the forms of nitrate, nitrite, and ammonia. Putting together all of the data collected, one can formulate the physical and chemical dynamics of the lake at each of the locations. This includes how the water mixes, nutrient and oxygen distribution, and, with further work, a sense of the exchange of greenhouse gases such as carbon dioxide and methane. The work I completed developing protocols, learning and calibrating equipment, running analysis, and fine-tuning methodology throughout this summer has given me a strong start in my long-term lake monitoring for my dissertation.