Hi all,
Since the last trip on 8 March, river flow has gone from about a quarter of the seasonal norm to well above average. The freshwater pulse resulted in a plume of highly turbid freshwater (>10 NTU) downstream to station 30, and strong salinity-based stratification from the tip of the saltwedge at station 30 to the mouth. Despite cool water temps (~15C), bottom water dissolved oxygen was depressed (2-4 mg/L) in the upper estuary from station 30 to station 70. The unusually salty and warm bottom water at station 140 is due to intrusion from the intercoastal waterway. Two subsurface layers of elevated chlorophyll, one at 1-2 m and the other along the bottom, were observed at stations 50 and 60. The surface water sample from station 60 was examined microscopically and contained a mixed assemblage of the two dinoflagellates that have been blooming for the past 6 weeks, Prorocentrum minimum and Heterocapsa triquetra, and also several species of cryptophytes, and small diatoms. None of the major taxa were concerning, fish-kill/toxin wise.
Stay well,
– Nathan
