Growth rate of the kelp Saccharina sessilis under different wave conditions

Growth rate of the kelp Saccharina sessilis (C. Agardh Kuntze; previously Hedophyllum sessile) among different wave exposures. During June and July 2013, the growth rate of S. sessilis was measured using the hole punch method (Mann 1973 Science) 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 Journal of Ecology). 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. Original Question: does growth rate of S. sessilis differ among wave exposures? 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)