PRETREATMENT ARTIFACTS ASSOCIATED WITH THE REMOVAL OF CALCAREOUS EPIPHYTES FROM SEAGRASS LEAVES

Experimental removal of calcareous epiphytes from seagrass leaves usin g varying dilutions of acetic acid, hydrochloric acid and phosphoric a cid, significantly altered the carbon (C), nitrogen (N) and phosphorus (P) contents of seagrass tissue. In addition to dissolution of the ca rbonate, the acid treatments caused leaching and weak digestion of the leaf material, resulting in the loss of certain organic compounds; th is was positively correlated with the concentrations of the acids appl ied. Removal of calcerous epiphytes from seagrass leaves using diluted acids prior to measurements, such as recommended in hand-books, is th erefore strongly advised against. An alternative pretreatment procedur e for the determination of organic C, N and P in seagrass leaves rich in calcareous epiphytic growth is proposed and tested. This new method ology involves the in situ acidification of untreated powdered leaf ti ssue (including microepiphytes) within silver cups prior to analysis o f the C and N contents. Comparison with results from non-acidified sam ples yields information on inorganic C contents (from the epiphytic ca rbonate) and its contribution as CaCO3 to the dry weight of the sample , which is used to correct the results obtained for organic C, N and P (and other elements).