Measurements of water column chemistry taken hourly over 24-hour periods at three sites in West Falmouth Harbor from 2006 to 2019

West Falmouth Harbor (West Falmouth, MA, USA) has been experiencing a dramatic increase in nitrogen loading from an upgradient municipal wastewater treatment facility since the early 2000’s. As part of a long-term study into the effects of this nitrogen enrichment, we have been measuring water chemistry at stations throughout the harbor to examine nutrient concentrations along the gradient from the highest loaded areas of the site to the most well-flushed. Water samples were taken hourly over 24-hour periods at 3 stations between 2006 and 2019. Due to covid restrictions on field and laboratory work, samples were not collected in 2020-2021; sample collection resumed in 2022 and data will be added after analysis. One station is in the well-flushed outer basin (OH) and one in the inner basin closer to the dominant groundwater N source (Snug Harbor, SH). These two were sampled at least once per year between 2006 and 2019. In two years, samples in the OH were taken at a location approximately 140m from the long-term site from this dataset. Those data can be accessed at doi:10.6073/pasta/73408abf801827966041c219f4222c1f. A third station is in the middle between the two, and was sampled in 2016 and 2018. Samples were processed for ammonium, phosphate, nitrate + nitrite, total nitrogen, and total phosphorus. On some dates, additional samples were run for silicate and chlorophyll. Salinity is reported for all samples. Samples were collected with an ISCO autosampler and stored on ice until analysis. Full analysis details and quality control methods are available in Hayn et al. 2014 (doi: 10.1007/s12237-013-9699-8).