Collaborative research: rapid: interactions between pulse and press disturbance following a 1,000 year coastal flood in hawaii

The National Science Foundation Division of Environmental Biology awarded the University of New Orleans $115,090 on August 1, 2026, under the Biological Sciences program (CFDA 47.074) to study how the invasive seaweed Avrainvillea lacerata (mudweed) interacts with coastal disturbance to affect Hawaiian rocky intertidal communities following a 1,000-year coastal flood event in March 2026.

The project leverages a 20-year continuous survey dataset from the south shore of Oʻahu and the extreme flooding event as a natural before-and-after experiment to test whether mudweed increases community resistance to flooding or prevents recovery to pre-disturbance conditions. The March 2026 storm inundated the island with more than two trillion gallons of water, causing severe coastal flooding and persistent brown-water conditions that altered freshwater, sediment, and nutrient inputs to shallow-water ecosystems. Results will inform resource managers on invasive species management strategies for maintaining local food security and native species habitat in Hawaiian rocky intertidal zones. The project integrates research findings into existing secondary and university-level educational programs to support biological sciences workforce training.

Work is performed in New Orleans, Louisiana with a period of performance from August 1, 2026 through July 31, 2027.

Abstract

O?AHU, hawai?i experienced a 1,000-year storm event in march 2026 that inundated the island with more than two trillion gallons of water, resulting in severe coastal flooding and persistent brown-water alerts. This unprecedented input of freshwater, sediments, and nutrients has the potential to drastically alter the composition and abundance of the shallow-water organisms surrounding the island. Hawaiian rocky intertidal communities are susceptible to such disturbances yet valued for sustaining local food security and providing crucial refuge for native species. A long-term (20-year) continuous survey along the south shore of o?AHU shows these shoreline communities are lush, with a high abundance of seaweed and herbivores (urchins, limpets). This dataset also captured the initial invasion and spread of the seaweed avrainvillea lacerata (mudweed). Mudweed dramatically changes rocky reefs to sediment-rich habitats, thereby altering the organisms that thrive there. This project leverages the extreme flooding event and two-decade long dataset with a before-and-after natural experiment to test how a habitat-forming, invasive species interacts with coastal flooding to affect intertidal communities. The results of this study will help resource managers determine whether mudweed increases the resistance of communities to flooding or instead prevents them from returning to their pre-disturbance state. Furthermore, this project will be integrated with existing secondary and university-level educational programs to support the training of students for the biological sciences workforce. This study aims to test whether the invasive, habitat-forming seaweed avrainvillea lacerata alters the resistance and recovery of hawaiian rocky intertidal communities following the march 2026 flooding event. In the pulse-press framework for resilience, IT is predicted that communities with greater chronic disturbance (more mudweed) will be more resistant to pulse disturbances but be less likely to recover native species, leaving the community in an altered stable state. To measure community resistance and recovery post-flooding, six sites will be surveyed along the south shore of o?AHU four times over the next 12 months. Documented variation in mudweed coverage among sites provides for an examination of how communities respond to flooding under varying levels of press disturbance. Surveys done during negative low tides will quantify the percent cover of seaweed species, and the density (M2) of sea urchins and sea cucumbers stratified across the intertidal zone. Environmental measurements (temperature, salinity, and nitrogen content) will distinguish flooding effects from background conditions. Species coverage and densities pre- and post-flooding will be compared with historical data to determine community resistance and recovery, with chronic invasion as a potential mechanism. Research outcomes will improve the ability to predict community change in response to invasive ecosystem engineers in understudied tropical systems and thereby inform conservation biology. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.