Water Quality Data Collected at Western Washington University's Shannon Point Marine Center in Anacortes, Washington USA: 1974 - 2023

<b>Introduction:</b>This file contains water quality data collected by Western Washington University's Shannon Point Marine Center in Anacortes Washington USA from 1974 through 2023. Water sampling was begun in 1974 by Paul Cassidy (deceased). Over the years, measurements have include temperature (in ^oC), salinity (in PSU), dissolved oxygen (in mg/L), dissolved carbon dioxide (in mmoles/L), pH, nitrate+nitrite (in µmoles/L N), ortho-phosphate (in µmoles/L P), ammonium (in µmoles/L N), chlorophyll (in µg/L), phaeopigments (in µg/L), turbidity, total alkalinity (in mEq/L), and carbonate alkalinity (in mEQ/L). The types of measurements and the methods used to make them have changed over time. Although the data presented here are through the end of 2023, many of the measurements continue, and more recent data can be obtained by emailing SPMC at [e-mail]. The following provides the best available information about the methods used.<b>Collection Sites and Methods:</b>The earliest collections were made from surface waters at the Shannon Point Beach (48^o 30' 31" N, 122^o 41' 07" W); however, sampling was later changed (at an unknown date prior to 1993) to collecting water from the SPMC pump house. Collections from the pump house generally involved taking triplicate seawater samples from a seawater tank or hose that tapped into the system downstream of the pumps. The intake pipe for this water was located at approximately 48^o 30' 32" N, 122^o 41' 11" W. Since 2010, samples have been consistently taken from a hose at the pump house that taps into the system just past the pumps. Samples were usually taken weekly or monthly, depending on staff availability. In 2009, the seawater system was substantially overhauled. During this time, the intake pipe for the seawater system was moved further offshore (48^o 30' 31" N, 122^o 41' 07" W) to deeper waters (approximately 20 ft below MLLW).<br>In 2011, divers also sampled seawater monthly at the end of the seawater system intake pipe to determine whether passing through the system to the collection point for the weekly samples altered the measurements. At the same time, comparisons were made to data collected from a sonde deployed by the Washington State Department of Ecology at the intake. Measurements taken from samples collected at the pump house were on average 1.5^oC higher in July, August, and September and 0.2^oC higher during the rest of the year. Passing through the seawater intake pipe and pumps also caused a reduction in chlorophyll concentrations that averaged 0.3 µg/L throughout the year. It did not significantly affect salinity, pH, dissolved oxygen, nitrate plus nitrite, phosphate, or phaeopigment measurements.<br><b>Measurements of Temperature, Dissolved Oxygen, pH, and Salinity</b>Measurements of pH, temperature, dissolved oxygen, and salinity have been made with a variety of calibrated handheld meters (usually manufactured by YSI, VWR, Orion, or Thermo) immediately after collecting the samples.<br><b>Measurements of Nitrate plus Nitrite (Jan 91 – Dec 23), </b><b><i>ortho</i></b><b>-Phosphate (Jan 91 – Dec 23), and Ammonia Nitrogen (Jan 91 -Dec 97)</b><br>Nutrients have been measured by hand and on several different automated analyzers. From Jan 1991 to May 2009, the nitrate plus nitrite measurements were made on an Alpkem Corporation instrument using method A303-S170-22 for Nitrate/Nitrite. <i>Ortho</i>-phosphate and ammonia nitrogen measurements were made by hand according to Parsons et al. (1984). Starting in May 2009, nitrate plus nitrite and <i>ortho</i>-phosphate analyses were conducted on a Lachat QuikChem 8500 using Methods 31-107-04-1-G for nitrate plus nitrite and 31-115-01-1-H for <i>ortho</i>-phosphate. A SmartChem 200 discrete analyzer replaced the Lachat QuikChem in early 2020, and nitrate plus nitrite and <i>ortho</i>-phosphate analyses were conducted as described in Van Alstyne (2024).<br><b>Chlorophyll (Nov 1992-Dec 2023) and Phaeopigments (Dec 1992-Dec 2023)</b><br>From 1992 until Jun 1993, chlorophyll and phaeopigments measurements were made spectrophotometrically using the methods described in Parsons (1984). Beginning June 15, 1993, the methods were changed to the fluorometric methods described for chlorophyll a and phaeopigments in Parsons et al. (1984).<br><b>Measurements of Turbidity (Apr 74 – Mar 92), Total Alkalinity (Aug 77 – Mar 92), Carbonate Alkalinity (Aug 77 – Mar 92), and Dissolved Carbon Dioxide (Aug 77 – Mar 92)</b><br>There are no written records of how these measurements were taken; however, it is believed the alkalinity and carbon dioxide data were obtained using LeMotte test kits (https://lamotte.com/products/environmental-science-education/).<br><br><b>References</b><br>Parsons,TR, Maita Y, Lalli C (1984) A manual of chemical and biological methods for seawater analysis. Pergammon Press, Oxford.Van Alstyne, KL (2024) Standard methods for seawater nutrient analyses at the Shannon Point Marine Center using a Smart Chem 200 discrete analyzer. figshare. Online resource. https://doi.org/10.6084/m9.figshare.25386589.v2<br>