The Bryozoan Diversity Mystery: Why Do We Have About 1000 Species in Japanese Waters?

Bryozoans are clonal and colonial organisms that have a species-specific biological potential to perform tactial (reactive) growth alterations. These biological potentials subdivide encrusting bryo-zoan morphotypes into several different pathways of individuality of morphoprocesses, a term in-troduced by V. N. Beklemishev (1890–1962), and applied to bryozoans with various degrees of colony integration. The frequency distribution of these morphotypes (z-/m-/c-/s-laminae) has been studied in bryozoans occurring in the vicinity of 5 Japanese marine biology stations, located along the latitudinal gradient in Japan from cool-temperate to (marginally) tropical. With increasing light influx and temperature, substrate occupation and thickness of biofilms increase, and filamentous microalgae and cyanobacteria gradually replace diatoms. Likewise, the warmer the water, the more frequent became s- and c-laminae. Both are the morphotypes with the best relative potential to perform tactical response and to overgrow biomats. In warmer water, bryozoan coverage tends to decrease benthic microbial diversity. In cool waters, the opposite is often the case. This indicates that biofilms contribute to differentiate the substrate surface into various bryozoan microhabitats, and thus contribute to the overall bryozoan diversity present in Japanese waters