DRAFT Dudley Pond Water Quality Sampling Program April 2, 2014 Report Author - Toni Moores This document is part of an ongoing Surface Water Quality Committee (SWQC) water quality sampling program initiated for Dudley Pond. The objectives of the Program are to gather Dudley Pond water quality data that will be used to: Compare to similar water quality data gathered in the past at Dudley Pond. Track the trophic index of Dudley Pond during the spring, summer and fall of each year. Summary
On April 2, 2014 water quality data was gathered at three sample points and at three depths at each sample point. Water quality parameters such as, pH, oxidation – reduction potential (ORP), dissolved oxygen (DO), dissolved oxygen % saturation and temperature were measured at three depths at each of the three sample points by SWQC members using a YSI Multimeter. Water and Secchi depths were measured at each of the three sample points. Samples were gathered by SWQC members and analyzed by Nashoba Analytical LLC. Based on somewhat uniform values top to bottom, the Pond was somewhat mixed and therefore it is assumed that the sampling occurred around the time of the spring turnover (water column mixing), even though there was a skim of ice at Sample Point 25. The Secchi depths found on April 2, 2014 were considerably poorer than in the past three years, which indicates that visibility in the water column was not as good as in recent years, possibly due to algae and/or suspended solids from recent rain storm. Based on the trophic state indexes shown below the water quality found on April 2, 2014 was worse than the water quality found during the previous three years. The poor Secchi reading and relatively high phosphorus and chlorophyll a concentrations at Sample Point 24 were responsible for increasing the TSI from 46 to 54 and had it not been for this poor results at Sample Point 24 the TSI range for Dudley Pond on April 2, 2014 would have been comparable to the previous three years
Date April 4, 2011 March 18, 2012 March 24, 2013 April 2, 2014
TSI 31 - 49 39 - 47 35 - 43 39 - 54
Chlorophyll a 2.72 – 3.99 ppb 1.98 – 4.62 ppb 1.39 – 4.46 ppb 2.24 – 5 ppb
Secchi Depth 12’ 1” 12’ 6” 14’ 4” 5’6” – 9’2”
Total Phosphorus 10 – 40 ppb 10 – 20 ppb Non-detect 10 – 20 ppb
This is the first spring sampling that total phosphorus and orthophosphorus were found at all sample points and all depths. As phosphorus is the rate limiting nutrient for weeds and algae, this finding along with poor Secchi depth measurements may indicate that the Pond will experience a larger crop of weeds and/or algae during 2014. The DO % Saturation and ORP data values were lower at Sample Point 25 than in the past three years, with DO % Saturation value a the bottom of Sample Point 25 being considerably lower (27%) than the spring of the previous three years. The reasons for this is unknown.