The Johansen Fish Resilience Lab is stationed on the beautiful Moku-o-loe (Coconut) Island (http://www.himb.hawaii.edu), utilizing the state of the art facilities at Hawaii Institute of Marine Biology (HIMB) as well as the amazing coral reefs at our doorstep and throughout the Hawaiian Archipelago. Our research focuses on how tropical coral reef organisms react and adapt to natural and human-induced environmental stressors and include work to understand species habitat selection, range-shift, habitat invasions, and the environmental requirements of species to function and thrive. All of our work is designed to help preserve, restore and sustain coral reef ecosystems despite growing environmental disturbance.
WHY ARE WE LOSING FISH ?
-We have several projects aimed at answering this question:
Nearshore tropical coral reef are a source of vital ecosystem services to over 600 million people worldwide, providing fisheries, tourism and shoreline protection. Yet, along with global climate change, coral reef organisms are exposed to multiple local stressors, including coastal developments and land-use practices that result in nutrient and sediment discharge to near-shore reefs. High sediment and nutrient run-off cause a loss of fish species, increased algal growth and loss of coral. Consequently, sediment and nutrient run-off is now classified as one of the primary and most damaging threats to coral reefs worldwide. Luckily, this is a localized threat that can be dealt with effectively at the local scale. To retain ecosystem health and minimize the risk of decline, there is a need for well-informed scientific information on which to base management relating to threshold limits of sediment run-off and water quality targets. We are conducting several projects to understand sediment impacts on coral reef fishes, by combining studies of field ecology, behavioral avoidance, and stress physiology of reef fishes. Our ultimate goal is to quantify the water quality condition required to maintain healthy fish populations on inshore reefs, and assist management and local communities in reaching those water quality targets.
Herbivorous reef fishes are critical for the resilience of coral reefs by promoting and facilitating the settlement, growth and survival of corals and coral recruits. The protection of herbivorous fishes is seen as an essential management tool for the conservation and protection of coral reefs, as reductions in herbivore abundance can lead to uncontrolled algal growth and degradation of coral habitat. However, long-term ocean warming and episodic marine heatwaves (i.e. discrete periods of extremely high ocean temperatures that can persist for days to months) pose a major threat to herbivores. Recent observations during heatwaves have documented sharp declines of >50% in the abundance of coral reef fishes and a loss of herbivores. We are working to understand the effects of ocean warming on herbivorous fishes, in order to identify resilient and sensitive species and clarify the degree to which heating may compromise the delivery of herbivore services.
The coral reefs of the southern Persian / Arabian Gulf (PAG) are exposed to the most extreme temperatures of any coral reef ecosystem on Earth, with summer temperatures regularly exceeding 36C (97F). These reefs are exposed to conditions that are similar to those projected for most coral reefs under unabated climate changes by 2100, and already seen today during heatwaves. One of the big mysteries of the PAG coral reefs is the fact that many reef fish species seem to disappear from visual censuses during seasonal extremes. Prevailing theory suggests that reef fishes may be migrating away from the reefs to deeper, cooler water to survive the summer months. Alternatively, they may become dormant within the reef matrix, only to emerge again once conditions improve. We are putting this question to the test. Using the Arabian Gulf reefs as a natural laboratory for how coral reefs around the globe will fare under climate change, the outcome of this study will be informative to fisheries and environmental managers alike. For this project, the Johansen Fish Resilience Lab is working closely with Professors John Burt and Holly Shiels via New York University Abu Dhabi, UAE.