2011 Chlorophyll Sampling Results

chlorophyll

October 18, 2011

The Day - October 18, 2011 started out cloudy and windy but cleared by noon. Weather is important to record as the chlorophyll molecule absorbs sunlight, using this energy to build carbohydrates. This means that bright sun levels are linked to increased algal and phytoplankton production, and it is this productivity that we are measuring with our chlorophyll a sampling.

Methods - The sampling methods are described in the main chlorophyll page. Note in our 2011 data:

If a single river site had more than one sample the results were averaged for reporting on this webpage.
All results were rounded to two decimal places.
An excel file of the data is included in the overall 2011 excel downloadable dataset.

Units: 2011 results are listed in ug/L yet 2005 results are listed in mg/m³. How does the unit 'ug/L' compare to 'mg/m^3' Micrograms/liter (ug/L) are the same as milligrams/cubic meter (mg/m³) and are completely interchange.

graph

Examining trends in the data. A trend line is a straight line used to connect multiple points in the data or the best fit connecting the data. The steepness of the trend in the data indicates the strength of the trend, the flatter the line the lower the strength of the trend. Once a trend line has been established an R² value is used to see how well the line fits the data, in other words is there a consistent relationship between the two variables being plotted on the graph (in our case this is chlorophyll and RMs)? A perfect match would be a value of 1.0, a strong relationship would be 1.0-0.7, and a moderate linear relationship would have values between 0.7 and 0.4. Our value of 0.022 falls very low suggesting that there is not a strong relationship between river mile and chlorophyll. This means we would not want to make predictions on chlorophyll levels in the river just using river miles.

Results for the 2011 samples show four areas in the estuary where there were spikes in chlorophyll productivity. Canarsie Pier in Jamaca Bay, Memorial Beach in Nyack, Ulster Landing Park in Saugerties and Cohotate Preserve in Athens had chlorophyll levels that reached higher than 2.0 ug/L. However, looking at the overall chlorophyll sample data plotted by River Mile (RM) the readings were relatively low with a dozen sites falling below 0.3 ug/L.

Below is a chart of those sections of the river with the highest and the lowest Chlorophyll readings.

*Chlorophyll Readings > 2.0 ug/L*				*Chlorophyll Readings < 0.3 ug/L*
Location	RM	ug/L	5 highest	Location	RM	ug/L	8 lowest
Canarsie Pier	-6.5	2.56	This year the highest levels of chlorophyll from our sample locations was represented by levels over 2.0 ug/L. They included only the four sites listed to the left.	Brighton Beach	-9	0.14	This year the lowest levels of chlorophyll from our sample locations was represented by levels below 0.3 ug/L. They include the dozen sites listed to the left.
Memorial Beach, Nyack	28	5.62		Valentino Pier, Brooklyn	-2	0.17
Ulster Landing, Saugerties	97	7.02		Governor's Island, Upper Bay	-1	0.06
Cohotate, Athens	115	2.51		HRPT Pier 40	2	0.21
				HRPT Pier 45	2.5	0.09
				HRPT Pier 95	5	0.18
				GW Bridge	12	0.12
				Englewood Boat Basin	13	0.07
				Alpine Boat Basin	18.5	0.13
				Croton Point Park	35	0.15
				Cold Springs	55	0.22
				Quiet Cove Poughkeepsie	78	0.16
				Saugerties Light House	102	0.27
				Hudson Waterfront	118	0.25

What are some of the parameters that can impact chlorophyll levels in the river?

Sunlight is one of the biggest factors:
- Long sunny summer days promote photosynthesis producing higher chlorophyll values than shorter cloudy days in fall and winter.
- Turbidity levels in the river directly affects the amount of sunlight that can penetrate the water column. In very turbid sections of the river the chlorophyll clusters closer to the surface where the light penetration is highest.
Nutrients also contribute to chlorophyll values. Nutrient levels in the estuary would be expected to be higher than nutrient levels in the open ocean.
Water depth and water speed (currents) are also important. Shallow, slow moving water will be more easily penetrated by sunlight and often has higher nutrient levels.
Local water input from smaller tributaries that enter the Hudson can contribute additional nutrients, as well as chlorophyll directly.

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