Seawater incubations were conducted in a flow-through seawater mesocosm facility housed in the Environmental Systems Laboratory at the Woods Hole Oceanographic Institution (Woods Hole, MA, USA). Details of the seawater pumping, filtering, and temperature tempering can be found in Mazzotta et al. without modification. Filtered seawater tempered to 20 ºC collected in a head tank and delivered a flow rate of 190 L/hr to the mesocosm tanks, yielding a residence time of 80 minutes. Straw samples were suspended approximately 10 cm from the bottom of the tank on stainless steel wire holders, each holding four samples (Figure ). Samples were suspended rather than clamped because, in trial experiments, clamping led to preferential cracking of some straws at points of deformation. Samples were randomly positioned on the sample holders, and time points were randomly positioned in the tank along its long axis to mitigate any potential bias of sample positioning in the mesocosm tank (Figure ). All samples were massed before placement in the mesocosm tank.