With a change of habitat, this project described habitat cascades supported by seagrass and drifting/entangled seaweeds, respectively as primary and secondary habitat formers, testing which factors can shape habitat cascades in soft-bottom seagrass systems. Compared to the project 1, here the differences between primary and secondary habitat formers are less pronounced as both of them are plants, able to provide shelter, resources, stress buffering in an analogous way. Then, I expected less noticeable effects of the secondary habitat former on the potential effect of the habitat cascade compared to project 1.
In this study, I described an habitat cascade based on the facilitation that the seagrass Zostera muelleri provides toward the drifting seaweeds entangled on its leaves, hypothesizing that:
(1) the presence of a secondary habitat former (here, Ulva) on the seagrass bed has a relevant role in controlling habitat cascades in soft-bottom estuaries, i.e., I expect to find more complex invertebrates’ communities when seagrass and Ulva are co-occurring;
(2) these habitat cascades occur over a wide range of spatio-temporal conditions, including across latitudes, estuaries, seasons;
(3) the secondary habitat former biomass and ‘type’ (here whatever the the seaweed is alive or an artificial mimic) control abundance and biodiversity of invertebrates, i.e., I expect to find more abundant and richer communities when living and abundant seaweeds occur;
(4) the invertebrates’ communities and HCs associated with morphologically different secondary habitat former mimics are different across latitudes;
(5) gastropods use the secondary habitat former as a predation shelter.