Community size structure varies with predator-prey size relationships and temperature across Australian reefs

Mean reef fish body size decreases towards warmer waters

Aquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal-reef fish surveys across a 15°C spatial sea surface temperature (SST) gradient, we found that the mean length of fish in communities decreased by ~5% for each 1°C temperature increase across space, or 50% decrease in mean length from 14 to 29°C mean annual SST. Community mean body size change was driven by differential temperature responses within trophic groups and temperature-driven change in their relative abundance. Herbivores, invertivores and planktivores became smaller on average in warmer temperatures, but no trend was found in piscivores. Nearly 25% of the temperature-related community mean size trend was attributable to trophic composition at the warmest sites, but at colder temperatures, this was <1% due to trophic groups being similarly sized. Our findings suggest that small changes in temperature are associated with large changes in fish community composition and body sizes, with important ecological implications.

Changes in sea floor productivity are crucial to understanding the impact of climate change in temperate coastal ecosystems according to a new size-based model

The multifaceted effects of climate change on physical and biogeochemical processes are rapidly altering marine ecosystems but often are considered in isolation, leaving our understanding of interactions between these drivers of ecosystem change relatively poor. This is particularly true for shallow coastal ecosystems, which are fuelled by a combination of distinct pelagic and benthic energy pathways that may respond to climate change in fundamentally distinct ways. The fish production supported by these systems is likely to be impacted by climate change differently to those of offshore and shelf ecosystems, which have relatively simpler food webs and mostly lack benthic primary production sources. We developed a novel, multispecies size spectrum model for shallow coastal reefs, specifically designed to simulate potential interactive outcomes of changing benthic and pelagic energy inputs and temperatures and calculate the relative importance of these variables for the fish community. Our model, calibrated using field data from an extensive temperate reef monitoring program, predicts that changes in resource levels will have much stronger impacts on fish biomass and yields than changes driven by physiological responses to temperature. Under increased plankton abundance, species in all fish trophic groups were predicted to increase in biomass, average size, and yields. By contrast, changes in benthic resources produced variable responses across fish trophic groups. Increased benthic resources led to increasing benthivorous and piscivorous fish biomasses, yields, and mean body sizes, but biomass decreases among herbivore and planktivore species. When resource changes were combined with warming seas, physiological responses generally decreased species' biomass and yields. Our results suggest that understanding changes in benthic production and its implications for coastal fisheries should be a priority research area. Our modified size spectrum model provides a framework for further study of benthic and pelagic energy pathways that can be easily adapted to other ecosystems.

A generalizable and tunable engineered ecosystem provides a clear route to prosperity and well-being to harness the world's aquatic "blue" food systems to help end hunger: A perspective

Seafood security is essential in modern society. In 2013, Bush and colleagues stated, 'Aquaculture, farming aquatic organisms, provides close to 50% of the world's supply of seafood, with a value of United States $125 billion. It makes up 13% of the world's animal-source protein (excluding eggs and dairy) and employs an estimated 24 million people'. With the increase in the human population and reducing fishing resources, humans increasingly rely on aquacultural products as the primary protein sources for many countries. Aquacultural productivity has been improving in recent years, and in certain countries, the aquaculture output is more than the fishing output. For example, Chinese aquaculture production is more than fishing output, which provides one-third of animal protein. Thus, intensive aquaculture has become the main supply with global aquatic products (FAO). In recent years, it is estimated that each person consumption of aquaculture products is 130 kg in some countries (Iceland). Here, we illustrate the road blocker in farmed shrimp production and provide our resolution. The global pandemic of white spot syndrome (WSS), caused by the white spot syndrome virus (WSSV), bears a devastating economic loss in farmed shrimp production, thereby jeopardizing seafood security. Currently, there is no effective control for WSS. Conventional single-species intensive farming removes the spatiotemporal interaction between different species. We hypothesize that establishing the spatiotemporal interface of a predator-prey may control WSS outbreak. We search for the pathways for the mechanisms by which predator-prey species interact and compete across spatial scales to characterize WSSV dispersal at regional scales for the local spatiotemporal structure of viral transmission. Thus, we create a generalizable and tunable engineered ecosystem that provides a clear route to prosperity and well-being to harness the world's aquatic "blue" food systems to help end hunger.