Spatial patterns and drivers of fish and benthic reef communities at São Tomé Island, Tropical Eastern Atlantic

Abstract

Marine communities vary across spatial scales due to changes in habitat structure, wave exposure, depth and anthropogenic activities. Here, we quantitatively characterized, for the first time, the reef fish assemblages and benthic communities in six sites around São Tomé Island, in the Tropical Eastern Atlantic region. We performed 139 underwater visual census and 112 photo‐quadrats across six sites around the island to explore the relative importance of exposure, depth and topographic complexity as drivers of fish and benthic reef communities. Planktivores were the most important trophic group, in terms of both fish abundance and biomass. Small fishes (0–7 cm) dominated the abundance, whereas biomass was mainly concentrated in 8–15 and 16–30 cm body size classes. About 30% of the total benthic cover was composed of turf algae and circa of 28% of calcareous coralline algae, whereas corals were comparably less abundant (only 8%). Among these, Montastraea cavernosawas the most abundant coral (46% of the coral cover and 4% of total benthic cover). Wave exposure was the most important driver of the reef fish assemblages and was also important for benthic communities. Also, fish species composition seemed to respond, although weakly, to benthic composition. Topographic complexity had little effect on the indicators of fish assemblages but seemed to drive some changes in benthic cover. Overall, our results evidence the dominance of small planktivorous reef fish assemblages and of turf algal communities in São Tomé. Taken together, they support the idea of benthic communities shaped by wave action, with minor importance of corals, and of important energetic contribution from planktonic material. We also suggest that the relatively low biomass of medium and large fish species reflects the long‐term fishing pressure in São Tomé Island.

Predicted Shifts in the Distributions of Atlantic Reef-Building Corals in the Face of Climate Change

“…Montastraea cavernosa presents a wider distribution being very common in the Caribbean (Horta-Puga, 2003) and is also abundant on the Brazilian coast in reefs from northeastern to southeastern Brazil (Laborel, 1970). In the eastern Atlantic, it occurs off the African coast in São Tomé Island and is the dominant coral in some areas (Laborel, 1974;Maia et al, 2018). Montastraea cavernosa can occur in both shallow and mesophotic areas (Goreau and Wells, 1967), where it can thrive and become one of the main stony coral components (Goodbody-Gringley et al, 2015).…”

Reef microhabitats mediate fish feeding intensity and agonistic interactions at Príncipe Island Biosphere Reserve, Tropical Eastern Atlantic

“…(2014) and Maia et al. (2018). We focused on individuals larger than 5 cm in total length, because identification of smaller individuals in RUVs can be unprecise (Fontoura et al., 2020; Longo & Floeter, 2012).…”

“…For quantifying fish feeding pressure (FP) on the benthic substrate and agonistic interactions among fishes, we analysed the central 10 min of each video, since the initial and final minutes were discarded in order to minimize the diver effects over fishes' behaviour (Longo et al, 2014). Each fish recorded biting the substrate or performing agonistic interactions inside the 2 m 2 area was identified, had its total length (cm) visually estimated and assigned to a trophic guild, according to Mouillot et al (2014) and Maia et al (2018). We focused on individuals larger than 5 cm in total length, because identification of smaller individuals in RUVs can be unprecise (Fontoura et al, 2020;Longo & Floeter, 2012).…”

“…Friedlander & Parrish, 1998; Williams et al., 2015). However, in the Tropical Eastern Atlantic (TEA), ecological aspects of fish and benthic assemblages remains understudied (but see Friedlander, Ballesteros, Fay, & Sala, 2014; Maia et al., 2018; Tuya, Bosch, Abreu, & Haroun, 2017). Thus, there is a gap in the knowledge concerning the relationship between habitat features and organisms' interactions.…”

“…Thus, there is a gap in the knowledge concerning the relationship between habitat features and organisms' interactions. Located in TEA, Príncipe Island is part of the Gulf of Guinea biodiversity hotspot (Roberts et al., 2002) and a variety of microhabitats are found on its rocky and biogenic reefs (Maia et al., 2018). These habitats are constituted of some key benthic organisms, including Epilithic Algal Matrix (EAM), calcareous coralline algae, macroalgae, hard corals, sponges, zoanthids and gorgonians (Laborel, 1974; Maia et al., 2018), potential resources that could possibly mediate fishes' biological interactions and, consequently, shape community structure.…”