Macroinvertebrate variability between microhabitats of peritidal stromatolites along the South African coast

Along the coastline near Port Elizabeth, South Africa, actively accreting peritidal stromatolite systems host a persistent metazoan community, which seemingly does not disrupt or consistently graze upon these structures. Macroinvertebrate communities occurring in different microhabitats (or mesofabric types) within this system were compared. This was achieved by identifying and counting the invertebrates found across different mesofabric types at different depth profiles. Mesofabric type was an important predictor of the invertebrate assemblage but was not the primary driver of their distribution. One of the well-laminated mesofabrics had more invertebrates than expected. The seasonal changes observed (such as the greater metazoan abundance observed in colloform mat types in winter compared to the greater metazoan abundance found in rimstone mat types in summer) were attributed to resource availability, specifically macroalgae. These findings are discussed in light of top-down forcing by metazoans on stromatolite microhabitats, and the consequent refugia benefit offered by these structures.