Science Serving Maryland's Coasts

Leslie Brandt, Gustavus Adolphus College

Class Year: 

Project Title: 

Epiphytic Algae as UV Filters on Leaves of the Seagrasses Zostera marina L. and Ruppia maritime L.


Epiphytes are considered detrimental to seagrasses as they reduce the amount of light, i.e. photosynthetically available radiation (PAR) that reaches the plant surface. This study evaluated the possibility that epiphytes can also be beneficial to seagrasses by reducing the amount of UV-B that reaches seagrass leaves. As UV-B may not only negatively affect seagrasses but also their epiphytes, possibly eliminating a positive filtering effect, artificial seagrass leaves made out of a UV-B transparent material were deployed at Horn Point Cove (Ruppia maritime and high nutrients) and Chincoteague Bay (Zostera marina and low nutrients) under a UV-B screen as well as under natural conditions (unscreened). At days 1, 3, 5, 7 and 12 after deployment, the leaves were collected and transmittance of UV and PAR quantified. No significant difference was found in the epiphytic load of UV-B-screened and unscreened leaves, suggesting that the present UV-B levels are not detrimental to epiphytic growth on seagrasses. In contrast, epiphytes transmitted a significantly lower amount of radiation in the UV-B range than in the PAR range. Therefore, epiphytic layers are effective UV-B filters on seagrass leaves. This benefit of epiphytes is lost when PAR transmission is reduced to levels below the compensation point.