Field measurements of dissolved oxygen distribution in the vicinity of a small fishing harbor in Attica, Greece, are presented, and the positive effect on water quality of rubble mound structures are evaluated. Surveys conducted during the spring and summer periods of 1998, 2000, and 2002 included dissolved oxygen (DO) concentration and temperature measurements in 30 sampling stations inside and outside the harbor basin and in the neighboring beaches. Regular measurements of both wind direction and force in Beaufort scale, as well as some measurements of wave and current were also made.

Dissolved oxygen concentrations in the harbor basin and in the beaches were lower than those measured outside the harbor in the vicinity of the rubble mound breakwater on the order of 1–2 mg/L. Dissolved oxygen concentration was found to increase in the zone of wave breaking. The increase was steeper with increasing wave heights. It is thus concluded that the rubble mound breakwater improves water quality in the surrounding area.

The field measurements agree qualitatively with laboratory measurements performed at National Technical University of Athens of wave breaking on permeable breakwater structures. Further study on the influence of harbor structures on air-sea oxygen transfer is needed before quantitative conclusions can be drawn.