2025-08-18 SMA-03-000007 Testimony Maki Morinoue

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a interventions of land-based stressors44.Management strategies that 0.30 leverage such policies to help mitigate coastal runoff,particularly in 0.25 urban areas,may support increased coral survival during severe marine 4 heatwaves. ID P 0.20 We also found thattotal fish biomass and scraper biomass were impor- ° tant factors in our models(Extended Data Table2).Healthyfish popu- 0 0.15 lations provide numerous reef-scale ecosystem functions29,including o some species releasing beneficial nutrient subsidies that increasecoral a 0.10 thermal tolerance45.Scrapers remove fast-growing algal turfs that could otherwise outcompete and overgrow stress-compromised corals30 By 0.051 Low Moderate comparison to phytoplankton biomass and coastal runoff,the slopes 0 5 10 15 20 25 30 35 40 45 50 of the relationships between total fish biomass and scraper biomass Cover of reef-building organisms(%) with heat-driven coral loss Were Weak(Extended Data Fig.4).Intense b Resource Probability marine heatwaves can cause severecoral mortality even on highly pro- management scenario Low Moderate High tected,uninhabited reefswith intact fish population s46,suggestingthat Initial condition Q 0.83 0.17 0.02 extreme heat stress may simplyoverwhelm the functional roles of reef Sea-based only Q 0.30 0.70 0.14 fish over shorttime scales.However,abundant fish populations,in par- Land-based only Q 0.17 0.83 0.26 ticular herbivores,can supportcoral reef recovery potential following Integrated land-sea Q 0.02 0.98 0.80 disturbance 2.Understanding whether this positive relationship holds across gradients in land-based impacts is key for supporting targeted og oa o� 06 05 06 810 o�� fisheries management in coastal marine ecosystems. 640 Coral reefs four years postdisturbance t 490 o The dominant reef-builders in tropical coral reef ecosystems are 360 oa hard corals and crustose coralline algae21.Crustose coralline algae ° are encrusting calcifying algae that fuse the reef framework together 5250 05 and promote coral growth by serving as a successional prerequisite for 6 160 06 coral recruitment and suppressing competitive fleshy algae 21.Given that coral cover can take a decade or more to recover to prebleaching N 90 0- level s41,assessing the total cover of reef-building organisms(hard 40 coral+crustosecora Ili nealgae)is more indicative of coral reef recovery potential following disturbance.Our surveys four years following the 10 2015 marine heatwave found that reef-builder cover ranged from 3.4 0 111110011 to 51.9%(mean of 24.3%±1.7 s.e.;n=55;Fig.4a).Critically,there were 25 50 75 100 125 150 175 200 225 250 275 different reefs with high(more than or equal to the 75th percentile)and „4111l Scraper biomass(kg hal) 41864 low(less than or equal to the 25th percentile)reef-builder cover before Fig.4 1 Local management scenarios thatsupport coral reef persistence and after the marine heatwave.Nearly two-thirds of reefs with high four years postdisturbance.a,Percentage cover ofreef-building organisms reef-builder cover in 2019 did not support such levels ofcover before (hard coral+crustose coralline algae)among reefs surveyed(n=55)in 2019, the marine heatwave.Similarly,we observed a more than 40%change four years following the marine heatwave.colours represent low(<-25th in the location of reefs with low reef-builder cover between 2015 and percentile),moderate(>25th and<75th percentile)or high(>-75th percentile) 2019.This reshuffling of reefs in terms of relative reef-builder cover cover.b,Probability oflow,moderate or high cover ofreef-builders shown in suggested differential coral reef persistence in the years following relation to variations inscraperbiomassand wastewater pollution.Example severe heat stress. scenarios show that simultaneously decreasing wastewater pollution We used an ordinal logistic regression framework to identify the and increasing scraper biomass results in afargreater probability ofhigh local land-sea human impacts and environmental factors that best reef-builder cover(scenario'C')than achievingeither management scenario in supported coral reefpersistence in theyears following the 2015 marine isolation(scenariosA'and'B').The upper(250kgha')and lower(30kgha') heatwave.Decreased wastewater pollution and increased scraper management scenarios for scraper biomass represented the 92nd and 36th biomass were the most important and significant(P<0.05)in pre- percentiles,respectively.We specifically chose250 kg ha-'as it approximates the long-term mean(2003-2019;n=17)scraper biomass inKealakekuaBay,a dictingwhetherareefhadrelativelyhigherreefbuildercoverfour marineprotected area in our study region where no fishing has been allowed years postdisturbance(Extended Data Table3).Pollution from human since1969(Supplementary Fig.11).Similarly,the upper(600,0001 ha-')and waste affects coastal marine ecosystems glObally48and is especially lower(2,5001h')management scenarios chosen for wastewater pollution harmful to corals from untreated sources,such as septic tanks and represented the 95th and 36th percentiles ofthe 2019 distribution, cesspools,which are both common in Hawai'i49.Consequently,high respectively(Supplementary Fig.12).Probability values and lineswere derived concentrations oftoxins and pathogens]each into coastal waters that from the top model from ordinal logistic regression modelling(Extended Data increase coral disease,reduce coral growth and reproduction,and Table3,Methodsand Supplementary Information).Coloursfor low,moderate increase coral susceptibility to bleaching42.These negative impacts and high in bare the same as those in a.See Extended Data Table lforfu111istof on coral persistence aretherefore much reduced in areas ofdecreased local land-sea human impacts and environmental factors included in the wastewater pollution.Scrapers reveal bare substrate as they feed and analysis,includingthose removed that were highly correlated(r>0.7,Methods facilitate the settlement,growth and survival ofcrustose coralline and Supplementary Fig.8).See Supplementary Fig.9for predictor variable algae and corals following acute disturbance30.Beyond these top-down distributions. effects on benthic condition,bottom-up effects of improved habitat quality could be contributing to the positive relationshipwe observed between scraper biomass and higher reef-builder cover.Parrotfish are the dominant scrapers in Hawai'i,and typically have home ranges of Nature I www.nature.com 1 5