Monitoring the water quality of Lake Merritt, Oakland, Ca.: A study on species abundance in compliance with the water quality index Giang N. Pham Abstract The impacts of urban development and human interaction on the water quality of a man-made lake in Oakland were quantitatively examined in order to determine the suitability for aquatic habitation. Using a water quality index, samples of the water were collected and the various pH, temperature, water hardness (dissolved solids), ammonia, salinity, dissolved oxygen, and nitrate/nitrite contents were investigated. To complement the physical-chemical composition assessment, relative abundance of fish in each sampling site were also noted and the correlations determined. The principal adverse effects on Lake Merritt were related to storm water run off, nearby housing development and other construction, direct pollution from recreational activities on and around the lake, contamination from adjacent roadways, attempts at improving the water quality for specific species, and interactions with the ocean. Results showed that there is a direct relationship between high water quality (conforming the most to the water quality index) and higher relative species abundance of aquatic wildlife. It was correctly anticipated that the water quality is “best” in the southwestern most region (site 2), indicating high index values where the lake suffers the least impacts from its surroundings, but is greatly affected by the ocean (thereby showing high salinity levels). These findings show that the aspects of water quality that have been speculated to be greatly affected by activities around the lake have led to poorer water quality and therefore lower abundance of aquatic wildlife. Turbidity and water flow rate have also been qualitatively assessed and considered, although not thoroughly examined and may greatly influence species abundance as well.Introduction Every large body of water in world has been tainted and “polluted” by man’s presence, in one way or another (Gleick 1998). Even the simplest of interactions by man can leave a body of water affected adversely, inadvertently affecting creatures that rely on the water as a sanctuary and source of sustenance as well. Both point source and non-point source pollution have impacted water quality for recreation, drinking water, and aquatic life in all major bodies of water on Earth (USGS 2001). This is especially true in highly populated, industrialized nations, such as the United States. After three decades of efforts to protect the nation's waters, many of our waterways are still seriously degraded to the point where they are not only unfit for human consumption, but also inhospitable to many of their formerly indigenous aquatic wildlife (Gleick 1998). One reason for this is that biological monitoring and assessment programs are still not in place in most locations. Multi-faceted approaches, involving actions such as watershed restoration and pollution prevention, water aeration, and pollution point source removal are being taken by industries, communities, and several levels of government to address these problems (Alameda Flood Control Dist. 1982). The methods needed to remove pollution from these bodies of water, however, have not been agreed upon, nor has a universal method to monitor and judge the quality of the water. Many argue that healthy aquatic ecosystems are developed by focusing on the biological integrity of a system (Water Quality Associates 1992). Fish therefore, are often considered the best overall measure of a body of water’s health because their presence indicates successful functioning of many complex habitat systems including stream flow, water temperature, water quality and channel habitat (Water Quality Associates 1992). Pollution, whether from a direct point source or indirectly, has serious impacts on the aquatic ecosystem. Drops in dissolved oxygen and increases in ammonia can create environments where only a limited number of species—those tolerant to such conditions will survive. This lowers species diversity and organism abundance (Buell and Girard 1994). The pollutants can also be hazardous to humans that are in contact with the water, through drinking, washing, or enjoying recreational activities in the water. Many North Americans are exposed to these risks (Alameda Flood Control Dist. 1982). It is therefore beneficial for community members to monitor the health of their streams, if not for the indigenous species, then for the health of the community. The two, however, are obviously interrelated. By cleaning up pollution for one cause, the effects would inevitably positively affect the other cause as well.Situated in the heart of the city of Oakland, Lake Merritt, the nation’s oldest wildlife refuge and a former sewer system for the entire city, has gone through tremendous changes since its first use by man. Yet, even today, it is still observed as having very poor water quality by most of its local residents (Water Quality Associates, 1992). Today, thousands of people still make contact with the water in the lake and have no idea how sanitary it really is. Many past observations have stated that the water quality is extremely poor and most believe that the water is inhospitable to aquatic wildlife. The latter has been proven untrue, as many fish still swarm to this site during certain seasons (Carlton 1966). This makes Lake Merritt a good urban model to test out methods for assessing water quality with both physio-chemical means and biological means, especially since no water quality monitoring of the lake has been done since the early 1960s. The examination of aquatic wildlife communities can be a useful means of monitoring changes occurring within the lake. I tested the hypothesis that water quality measurements and use of the water quality index, used in conjunction with a biological sampling regime can accurately determine water quality. I predicted that the water quality index had a strong positive relationship with the abundance of organisms found in the lake. Methods Study site and sampling locations Lake Merritt lies directly in the region considered to be the heart of Oakland, located in an area towards the north-western region of the city. Directly to the west of the lake is the San Francisco bay and towards its east are the Oakland Hills. The Oakland Hills consist of many streams, forming a
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