Total Chlorophyll ConcentrationStatus and TrendsChlorophyll in free flowing ecosystems is predominantly epibenthic, attached to rocks or as benthic algal mats. Planktonic algae may develop in slower moving portions of large rivers and streams. Impoundments may also serve as source regions of planktonic algae for downstream habitats. Planktonic algae only are sampled at non-tidal stations. |
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The nutrient, chlorophyll, DO relationship is less well established in flowing waters but may approach the well described condition for lotic and estuarine environments as rivers widen and flow velocity decreases. Here we would expect to see nutrients fuel phytoplankton growth/senescence/death and concomitant DO depletion. Chlorophyll is sampled from Hancock, MD (POT 2386, Map #13) east to the Choptank River a total of 37 stations. CHLA ranged from 1.2 ug/L at the upper Patuxent Station (Unity, MD) and the Choptank River station to 4.3 ug/L at the station on Rock Creek. Highest median concentration (CHLA > 3.78 g/L) occurred at the Gun Powder River station at Cromwell Bridge Road, on the Patuxent below the dam at Rocky Gorge and on Rock Creek at the bridge on MD 410. These 3 stations constitute 8% of the stations where CHLA is sampled. Stations with the lowest median CHLA concentration (CHLA 2.65 g/L) constituted 78% of the stations where CHLA is sampled. Stations with intermediate concentration were located on upper Antietam Creek, upper Catoctin Creek, Upper Monocacy and the Gunpowder River between Loch Raven and Prettyboy reservoirs. Trends in CHLA were all decreasing and occurred at 51% of all stations. Chlorophyll A correlated with TP at Antietam Creek (Poffenberger Road), Point of Rocks (MD side), Monocacy River at Bridgeport, Potomac River at Whites Ferry (MD side), Patuxent River at Unity, MD and on the Patapsco River at Hollofield and at Washington Blvd. The trends for both CHLA and TP were decreasing at these stations. Chlorophyll A correlated with TN at the Susquehanna River station although the relationship was not as strong (p<0.0006). Chlorophyll data for sampled locations are summarized in these plots. |
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