Seascape Configuration Leads to Spatially Uneven Delivery of Parrotfish Herbivory across a Western Indian Ocean Seascape

Abstract

Spatial configuration of habitat types in multihabitat seascapes influence ecological function through links of biotic and abiotic processes. These connections, for example export of organic matter or fishes as mobile links, define ecosystem functionality across broader spatial scales. Herbivory is an important ecological process linked to ecosystem resilience, but it is not clear how herbivory relates to seascape configuration. We studied how herbivory and bioerosion by 3 species of parrotfish were distributed in a multi-habitat tropical seascape in the Western Indian Ocean (WIO). We surveyed the abundance of three species with different life histories—Leptoscarus vaigiensis (seagrass species), Scarus ghobban (juvenile-seagrass/adults-reefs) and Scarus rubroviolaceus (reef species) —in seagrass meadows and on reefs and recorded their selectivity of feeding substrate in the two habitats. Herbivory rates for L. vaigiensis and S. ghobban and bioerosion for S. rubroviolaceus were then modelled using bite rates for different size classes and abundance and biomass data along seascape gradients (distance to alternative habitat types such as land, mangrove and seagrass). Bioerosion by S. rubroviolaceus was greatest on reefs far from seagrass meadows, while herbivory rates by S. ghobban on reefs displayed the opposite pattern. Herbivory in seagrass meadows was greatest in meadows close to shore, where L. vaigiensis targeted seagrass leaves and S. ghobban the epiphytes growing on them. Our study shows that ecological functions performed by fish are not equally distributed in the seascape and are influenced by fish life history and the spatial configuration of habitats in the seascape. This has implications for the resilience of the system, in terms of spatial heterogeneity of herbivory and bioerosion and should be considered in marine spatial planning and fisheries management.

Multi-Scale Coral Reef and Seascape Habitat Variables Combine to Influence Reef Fish Assemblages

“…Furthermore, some species change their feeding behaviors based on the structural connectivity of surrounding habitats (e.g., the distance to adjacent seagrass beds). Eggertsen et al (2020) [90] observed increased bite rates for Scarus ghobban when near seagrass beds. We too found that Scarus ghobban contributed strongly to the assemblage structure of parrotfish in the seagrass habitat cluster (Table 2).…”

Diel vertical movements and feeding behaviour of blue humphead parrotfish Scarus ovifrons in a temperate reef of Japan

“…The algae ingested by S. ovifrons are commonly distributed throughout rocky reefs in the region (Ohno et al ., 1990) and are potentially eaten by several co‐occurring grazing fish ( e.g ., Scarus ghobban and Calotomus japonicas ; Nakamura et al ., 2013). Indeed, Scarus ghobban from Mozambique fed primarily on EAM on rocky substrata (Eggertsen et al ., 2020). Intrusions of tropical herbivorous fishes, such as parrotfish, surgeonfish and rabbitfish, into temperate reefs are becoming common with the global ocean warming (Vergés et al ., 2014).…”

Comparative Mitogenome Analyses Uncover Mitogenome Features and Phylogenetic Implications of the Parrotfishes (Perciformes: Scaridae)

“…Therefore, it can help to mitigate the competition between coral reefs and macroalgae and increase the resilience of coral reef ecosystems subjected to anthropogenic or natural disturbances [ 21 , 22 ]. In addition, the excavating and scraping species can break the reef framework into sand-sized sediments and facilitate the cycling of calcium carbonate on reefs, which are also dispensable agents in reef erosion and sediment production and transport [ 23 , 24 ].…”