Extreme environmental conditions reduce coral reef fish biodiversity and productivity

Abstract

Tropical ectotherms are hypothesized to be vulnerable to environmental changes, but cascading effects of organismal tolerances on the assembly and functioning of reef fish communities are largely unknown. Here, we examine differences in organismal traits, assemblage structure, and productivity of cryptobenthic reef fishes between the world's hottest, most extreme coral reefs in the southern Arabian Gulf and the nearby, but more environmentally benign, Gulf of Oman. We show that assemblages in the Arabian Gulf are half as diverse and less than 25% as abundant as in the Gulf of Oman, despite comparable benthic composition and live coral cover. This pattern appears to be driven by energetic deficiencies caused by responses to environmental extremes and distinct prey resource availability rather than absolute thermal tolerances. As a consequence, production, transfer, and replenishment of biomass through cryptobenthic fish assemblages is greatly reduced on Earth's hottest coral reefs. Extreme environmental conditions, as predicted for the end of the 21st century, could thus disrupt the community structure and productivity of a critical functional group, independent of live coral loss.

Composition, distribution and relative abundance of fishes linked to fringing reefs of southern Veracruz, Gulf of Mexico

“…The most frequent fish species by reef habitat are shown in Table 2. Extreme environmental conditions may limit the establishment and distribution of ichthyofauna [25], especially of roving herbivores [26,27].…”

“…The results of this research reveal that the components and abundance of fish associated with the reef ecosystems of southern Veracruz are related to at least 3 factors: 1) structural complexity, which is a determining in reef fish diversity [31,32,39]; 2) river drainage and the regional rainfall regime [28] which decreases salinity and increases water turbidity in the coastal zone. When these coupled with oceanographic dynamics may be unfavorable for fish recruitment and survival [25,37,40]; and 3) depth, that separates shallow and deep fish associations [3,19].…”

Fish and Fisheries of the Eastern Coast of Mexico, with Emphasis on Coral Reef Species

“…Regional conditions of salinity, temperature, concentration of nutrients, among others, as well as the heterogeneity of the reef environment, create patterns of differential abundance among the three regions. Thus, the proportions estimated from published [11-13, 32, 58, 59] and unpublished data show that, Blue tang (Acanthurus coeruleus), Blue chromis (Chromis cyanea), Yellowhead wrasse (Halichoeres garnoti) and Bluehead (Thalassoma bifasciatum) are higher in the Caribbean, while Glass goby/Masked goby (Coryphopterus hyalinus-personatus), Mardi Gras wrasse (Halichoeres burekae), Doctorfish (Acanthurus chirurgus) and Brown chromis (Chromis multilineata) show a higher relative abundance in the reefs of the Gulf of Mexico ( Table 3) Environmental heterogeneity has been referred to as a cause of ichthyofaunal diversity [60,61] and this heterogeneity can be analyzed at various scales: region, reef and reef zone. At the region level, oceanographic processes (currents, gyres, etc.)…”

The impact of climate change on fish infectious diseases (a review)

“…Причиною цього явища може бути збільшення кількості захворювань у популяціях, де збудник вже існує, або через поширення інфекції переходить до нових чутливих видів. Таким чином, зміни на вищих трофічних рівнях, які тримають хворобу під контролем, можуть призвести до спалахів захворювання і на нижчих рівнях взаємодій [85].…”