Growth rate of the kelp Saccharina sessilis​ under different wave conditions

Growth rate of the kelp <i>Saccharina sessilis</i> (C. Agardh Kuntze; previously <i>Hedophyllum sessile</i>) among different wave exposures. During June and July 2013, the growth rate of S. sessilis was measured using the hole punch method (Mann 1973 <i>Science</i>) at the rocky intertidal site at Fogarty Creek, Oregon USA (44.838N, -124.058W). Three locations within that site were measured as having low, intermediate, and highly wave exposed conditions (Barner et al. 2016 <i>Journal of Ecology</i>). Growth rate was measured by making a small hole punch in multiple kelps in the different wave-exposed areas, then returning within two weeks to measure growth. Each row in the data is an independent sample - a different individual kelp plant.<br>Original Question: does growth rate of <i>S. sessilis</i> differ among wave exposures?<br><br>Variables in data (column headers)Date: year_month_dayExposure: L=low wave exposure, M=intermediate wave exposure, H = highly wave exposedLength.to.hole: the length between the holdfast and the point at which the hole was initially punched (cm)Growth: difference (in cm) between the original hole punch and the location of the punch after N daysWhen.punched?: date (year_month_day) that the growth measurement was takenN.days: the number of days of growthGrowth.per.day: growth rateWithin tide-series?: was the growth measurement taken during a period of negative low tides or not (1 or 0)