The ecology, behaviour and physiology of fishes on coral reef flats, and the potential impacts of climate change

Tebbett

et al. 2018

Ecology and Evolution

The reef flat is one of the largest and most distinctive habitats on coral reefs, yet its role in reef trophodynamics is poorly understood. Evolutionary evidence suggests that reef flat colonization by grazing fishes was a major innovation that permitted the exploitation of new space and trophic resources. However, the reef flat is hydrodynamically challenging, subject to high predation risks and covered with sediments that inhibit feeding by grazers. To explore these opposing influences, we examine the Great Barrier Reef (GBR) as a model system. We focus on grazing herbivores that directly access algal primary productivity in the epilithic algal matrix (EAM). By assessing abundance, biomass, and potential fish productivity, we explore the potential of the reef flat to support key ecosystem processes and its ability to maintain fisheries yields. On the GBR, the reef flat is, by far, the most important habitat for turf‐grazing fishes, supporting an estimated 79% of individuals and 58% of the total biomass of grazing surgeonfishes, parrotfishes, and rabbitfishes. Approximately 59% of all (reef‐wide) turf algal productivity is removed by reef flat grazers. The flat also supports approximately 75% of all grazer biomass growth. Our results highlight the evolutionary and ecological benefits of occupying shallow‐water habitats (permitting a ninefold population increase). The acquisition of key locomotor and feeding traits has enabled fishes to access the trophic benefits of the reef flat, outweighing the costs imposed by water movement, predation, and sediments. Benthic assemblages on reefs in the future may increasingly resemble those seen on reef flats today, with low coral cover, limited topographic complexity, and extensive EAM. Reef flat grazing fishes may therefore play an increasingly important role in key ecosystem processes and in sustaining future fisheries yields.

Section: Discussionmentioning

confidence: 99%

The role of the reef flat in coral reef trophodynamics: Past, present, and future

Tebbett

et al. 2018

Ecology and Evolution

Ann. Limnol. - Int. J. Lim.

“…The assessment of the effects of temperature on fish activity is a significant challenge in the context of climate warming (Harborne, 2013), given that fish may influence habitat features and ecosystem functioning through both trophic and non-trophic activities (Shirakawa et al, 2013). Although some studies have assessed the role of temperature in regulating the activity of sediment reworking (e.g., White et al, 1987;Ouellette et al, 2004), these have not yet assessed this for freshwater fish.…”

Section: Introductionmentioning

confidence: 99%

Influence of temperature on surface sediment disturbance by freshwater fish: a microcosm experiment

Canal

Laffaille

Gilbert

et al. 2015

-Water temperature is a key parameter that regulates activities of ectotherms (e.g., fish) and has been projected to rise in the future in the context of climate change. Surface sediment disturbance (SSD) is an important function performed by fish that modifies benthic habitat properties and may thus influence ecosystem functioning. However, the link between SSD by fish and temperature remains unexplored. In this study, we experimentally assessed the influence of two contrasted temperatures (10 versus 20 xC) on SSD by three freshwater fish species in aquaria. After 10 days, the total surface disturbed by the species was approximately 2-3 times higher at warm than at cold temperature but the number and area of patches disturbed by the species were not significantly different. The stone loach Barbatula barbatula, a benthic fish species, had a higher SSD activity (i.e., total surface disturbed, number and size of patches disturbed) both at cold and warm temperatures than two cyprinid species, chub Squalius cephalus and sofie Parachondrostoma toxostoma. On average, SSD by B. barbatula resulted in approximately two and three more patches than the cyprinid species at 10 and 20 xC, respectively, and the mean patch area disturbed by B. barbatula was about two times larger than the ones disturbed by the cyprinid species. The total surface disturbed by the cyprinids at warm temperature was roughly equivalent to the surface disturbed by B. barbatula at cold temperature. Our results thus suggest that SSD by fish could increase in future warmed conditions.

“…(Nelson et al 2006;Carpenter et al 2011;Potschin and Haines-Young 2011). For example, increasing variability in average values of temperature, rainfall and relative air humidity directly affect ecosystem conditions and services, and are key variables in sustaining people's livelihoods across all levels of society (O'reilly et al 2003;Walker et al 2008;Sullivan and Huntingford 2009;Harborne 2013;Sara et al 2014). In deltas and estuaries, water level plays an important role in preserving biodiversity, enabling agriculture, climate buffering and flood control.…”

Section: Physical Driversmentioning

confidence: 99%

Evolutionary social and biogeophysical changes in the Amazon, Ganges–Brahmaputra–Meghna and Mekong deltas

et al. 2016

Policy-making in social-ecological systems increasingly looks to iterative, evolutionary approaches that can address the inherent complexity of interactions between human wellbeing, provision of goods and the maintenance of ecosystem services. Here, we show how the analysis of available time-series in tropical delta regions over past decades can provide important insight into the social-ecological system dynamics in deltaic regions. The paper provides exploratory analysis of the recent changes that have occurred in the major elements of three tropical deltaic social-ecological systems, such as demography, economy, health, climate, food, and water. Timeseries data from official statistics, monitoring programmes and Earth observation data are analysed to explore possible trends, slow and fast variables, and observed drivers of change in the Amazon, Ganges-Brahmaputra-Meghna and Mekong deltas. In the Ganges-BrahmaputraMeghna delta zone, increasing gross domestic product and per capita income levels since the 1980s mirror rising levels of food and inland fish production. In contrast, non-food ecosystem services, such as water availability, water quality and land stability appear to be deteriorating. In the Amazon delta, natural and anthropogenic perturbations are continuously degrading key ecosystem services, such as carbon storage in biomass and soils, the regulation of water balance, and the modulation of regional climate patterns. In the Mekong delta, rapid economic development, changing land use practices and salinity intrusion, are progressively putting more pressure on the delivery of important provisioning services, such as rice and inland aquaculture production, which are key sources of staple food, farm incomes and export revenue. Observed changes in many key indicators of ecosystem services point to a changing dynamic state and increased probability of systemic threshold transformations in the near future.