MEPS 580:153-167 (2017)  -  DOI: https://doi.org/10.3354/meps12300

ABSTRACT: Lithified microbial mats (microbialites) dominated shallow oceans during the Precambrian but are rare in modern environments. Factors restricting the prevalence of modern microbialites have been linked predominantly with reduced marine calcium carbonate levels and metazoan disruption. Some living microbialites only manage to persist together with an abundant metazoan community because of, among other factors, the regulatory pressure of fish predators on the grazing macrofauna. In peritidal pools formed by layered microbialites (termed ‘stromatolites’) along the South African coastline, fishes occur regularly, yet the dynamics of their interactions with co-occurring metazoans or other habitat features are unknown. We therefore aimed to link multivariate fish abundance to correlates of potential food resources and physico-chemical variability, using a generalised linear modelling approach. The fish community comprised both a resident species (the gobiid Coryogalops sordidus) and a number of transient fishes, most notably Myxus capensis (Mugilidae) and Rhabdosargus holubi (Sparidae) that dominated the fish biomass in the pools yet displayed sporadic or seasonal fluctuations. Generally, fish abundance was largely related to physical forces primarily associated with spatial salinity gradients of pools as well as swell conditions, with resource variability offering some, but minimal overall, contribution. These insights suggest limited top-down predatory control by fishes on macrofauna, but rather that this environment invokes the recruitment of typical marine estuarine-dependent fish species. However, abundance and growth patterns of recruits suggest that these pools are unfavourable nurseries for juvenile development and export, likely because of their limited size, reduced feeding opportunities and spatial extent, unlike typical estuaries.

KEY WORDS: Ichthyofauna · Juveniles · Living microbialite · Nursery · Predator · Recruitment cues · Tidal pools