The quality of surface waters in and around ports is important to support marine life. Polluted waters are, however, not only harmful for marine life, it can also contaminate sediments which in turn will boost dredging costs. Water quality can be polluted from many sources, assessment of sources is needed for appropriate action. In general a wide set of measures are available to reduce pollution from such variety of sources including application of barriers  preventing excess of run-off (see also bioswales), stormy-water treatment plants, or ecological optimisation of port infrastructure. Pollution from ships, i.e. oil spills, can be another important source. Emergency response units with suitable equipment to confine and remove such spills can be very effective in limiting the impact.