GULF PRODUCTIVITY IN TROUBLE DUE TO PHYTOPLANKTON DECLINE

“I was sitting right on this chair and I was hootin’ and hollerin’, because it was just too good to be true,” he says. That’s because, for nearly two decades, Balch has been making eerily similar measurements of ocean color as he creates his own long-term baseline study of the gulf. He uses all the latest gear — he’s got an updated plastic Forel-Ule scope, electronic light meters, access to NASA satellite data, GPS and submersible data-hunting drones. But what’s being measured? It’s basically the same.

"And we had all the information we needed to then go back to calculate what were the Forel-Ule scales and then to compare them to what Bigelow saw over a century ago,” Balch says. Ocean color is a revealing indicator of ocean content. Where it’s bluest it’s purest, with the least amount of organic matter. Where it’s greener, plant life, including the microscopic phytoplankton, which provide about half the oxygen we breathe, is likely abundant. Where it’s browner or yellower, you can bet that’s dissolved organic matter washing out from shore. Balch has been using color scales and many other data points to take a close look at changes in the gulf’s biochemical systems. But until recently, he only had color data going back to the 1970s. Discovering Bigelow’s work opened the window on the gulf’s past much wider.

“The coordinates are there. The temperature and salinity he measured as well, and the color. And it’s yellower. It’s extraordinary, the changes in water color now that we see compared to what they used to be,” Balch says. It’s still predominantly blue, but the range from blue to yellow is greater — about twice as wide along the scale as what it was in Bigelow’s day. And that correlates with increased precipitation scientists link to climate change. It’s washing dissolved organic material from watersheds up and down the coast into the gulf. Balch says it’s like dark, yellow-brown tea steeped from dead leaves and soil. And that, he says, contributes to massive declines in the productivity of phytoplankton.

“Think of it like basically putting sunglasses over the ocean. So the phytoplankton now have to compete with the tea that’s coming in and is absorbing all the blue light that the plants need for photosynthesis. That’s one of the hypotheses,” he says. Balch and his colleagues have measured declines in phytoplankton productivity of as much as 80 percent, which may correspond with declines in some gulf species higher up the food chain. And using current models of continuing increased precipitation, he and his colleagues predict the trend will continue. On Thursday, they’ll load a cargo container full of equipment onto a borrowed research vessel and set out from Portsmouth for a three-day voyage to gather more baseline data from the changing Gulf. In more senses than one, they’ll be sailing in Henry Bigelow’s wake.