MISSION: WATER 16 HEADLINE SURFACE WATER Versatility in the Field “We were looking for something we could use in the field at very low temperatures,” Benstead explains. Just a fraction of the price of more sophisticated sondes—a huge consideration when stocking up on 20 instruments–the ProODO meters combined handheld versatility with onboard datalogging and a large memory. The team also built respiration chambers to create laboratory- like conditions in the field. With ports sized to fit the ProODO probes, stirrers rigged from battery-operated computer fans, and large stoppers that allow quick drainage, the chambers permitted metabolism studies on the spot. “We were taking the tiles out of the stream and putting them into the chamber,” Benstead explains. “You never want to take things back to the lab.” Surprising Results Results from the Hengill study, now being published in a series of papers and journals including Global Change Biology and Ecology, yielded some surprises. “The theory was that primary production is going to increase a little bit, but the results saw much larger increases than we expected,” says Hood. In fact, temperature increases led to explosions of primary productivity. For instance, warming a stream by an average of 3.3°C (5.9°F) over a year tripled the net primary production and nearly tripled the rates of nitrogen and phosphorus use efficiency. In the whole-stream warming experiment, warming led to flushes of Ulva, a filamentous alga that dramatically shifted nutrient cycling and nitrogen efficiency patterns. “Algae growing after warming tended to need less nitrogen,” explains Hood. “They were more efficiently using it. We also think there was more efficient cycling in algal mats— little bugs eat and release nitrogen more quickly at warmer temperatures, and some diatoms in those mats have endosymbionts that fix nitrogen in the summer.” In another element of the study, a boost in mean water temperature of 3.8°C (6.8°F) over two years resulted in a population shift from cold-adapted midges to snails that slowly colonized the warming stream—a direct contrast to the team’s expectation that average body size would become smaller in response to higher temperatures. In short, the Hengill experiments demonstrated that the theories derived from single-species lab studies may be challenged in real-world conditions. That has huge implications for scientists trying to predict the impact of, say, warmer water carrying nitrogen runoff into Lake Erie, or policy makers trying to decide whether wastewater treatment plants should continue focusing only on phosphorus reduction, or if nitrogen should be controlled, too. “It’s allowed us to tackle some of these theoretical ideas in the real world,” says Hood. “It’s allowed us to see where the theory works and where it doesn’t. Because the landscape lends itself to these comparisons, we can create nice, manipulative experiments.” Packed In Jon Benstead of the University of Alabama is an experienced hand at working far from the lab, whether it’s on the North Slope of Alaska or in the rolling hills of Iceland—the sorts of places where you can’t run a longer extension cord to find an outlet, or jog down to the corner store for supplies. That’s made him an expert on packing luggage, which he points out can save thousands of precious grant dollars per trip that would otherwise be sunk into freight costs. To supply his stream warming study in Hengill, Iceland, Benstead and his team disassembled a heat exchanger and 365 meters (1,200 feet) of flexible PVC tubing and packed the pieces as luggage, along with mounds of other scientific equipment. In all, he and four colleagues checked 950 pounds of gear to Iceland in 14 bags for a cost of $950. “Have a good luggage scale in your lab, and know absolutely everything you have to know about your airline’s baggage policy,” Benstead advises fellow water experts headed for the field. “And any time you’re packing, make sure you have checklists and good inventories for everything. It’s all about planning, isn’t it?”