A review on operational bioindicators for sustainable coastal management—Criteria, motives and relationships

The basic aim of this work is (1) to review, present and discuss practically useful (operational) bioindicators for sustainable coastal management, (2) to motivate the selection of the given bioindicators and (3) to illustrate that these variables can be modelled and practically applied, e.g., to detect thresholds and regime shifts. These bioindicators are meant to be used at local, regional or national levels and they should meet defined criteria for practical usefulness, e.g., they should be simple to understand and apply to managers and scientists with different educational backgrounds. The target bioindicators discussed and motivated in this work are: Secchi depth, chlorophyll-a concentrations, oxygen saturation in the deep-water zone and macrophyte cover. They are regulated by abiotic factors, such as nutrient concentrations, suspended particulate matter, salinity, coastal morphometry and water exchange. Such relationships are discussed and reviewed and the aim is to illustrate how these bioindicators are interrelated and how they reflect fundamental aspects of coastal ecosystems. The practical use of these bioindicators will be demonstrated by a case-study.