Citizen scientists highlight conservation value of a small subtropical reef, Flinders Reef, southeast Queensland, Australia

Subtropical reefs are unique ecosystems that require effective management – informed by regular ecological monitoring – to foster resilience to environmental changes. Resources to conduct monitoring are limited, and citizen science can complement data from local management agencies. Here, citizen science efforts document the ecological status of a subtropical reef, Flinders Reef, Moreton Bay Marine Park, Australia. Ecological surveys, following Reef Check Australia and CoralWatch protocols, were conducted by 44 trained volunteers. Ten sites at Flinders Reef were surveyed at 5-10 m depth in autumn and spring. Additionally, underwater photos and depth surveys were integrated with satellite imagery to create a detailed habitat map. Coral cover across sites ranged between 14% and 67%. Branching corals dominated the site with 67% cover and showed 89% dissimilarity in coral community composition compared to other sites. Coral community composition was mostly explained by spatial variation, of which 16% was influenced by wave exposure. Observed reef impacts including physical damage, unknown scars and coral disease were three times lower than studies on more accessible reefs in Moreton Bay Marine Park. Invertebrate abundance was relatively low (6.65 individuals per 100 m2), with the most abundant groups observed being sea urchins (Diadema spp.), gastropods (Drupella spp.) and anemones. Butterflyfish were recorded at every site and were the most abundant fish group surveyed. Findings highlight the healthy condition of Flinders Reef, likely influenced by its offshore location and protection status as a ‘no-take’ zone. This study demonstrates that increasing the current 500m radius protection zone by a further 500m could double the protected area of coral, offering potential further conservation benefits. The findings resulting from the ecological data analysis and created benthic habitat map, provide an example of how citizen science based projects can assist marine park authorities and the public in ongoing conservation efforts.

Flinders Reef is a relatively small subtropical reef located at the northern entrance to Moreton 106 Bay. The reef is protected as a Marine National Park Zone (also referred to as a green zone, 107 i.e., a 'no-take' area where extractive activities like fishing or collecting are not allowed 108 without a permit) within the Moreton Bay Marine Park. Moreton Bay provides habitat for 109 many marine species including over 1,600 invertebrates, 125 coral species, 9 species of 110 dolphin, migrating humpback whales, manta rays, grey nurse sharks, leopard sharks, and 111 large herds of dugong [26]. Reef Health Impact Surveys [23]  and invertebrate indicator species, and coral health status for 10 sites, accompanied by the 127 first detailed habitat map of the reef. Habitat maps provide an important management tool, 128 but currently the existing map of Flinders Reef is limited to an outline of the exposed 129 sandstone platform without any spatial description of benthic composition.  Australia (26° 58.715' S, 153° 29.150' E) (Fig 1). A 500 m radius zone provides protection as 139 a green zone under a no-take, no fishing, no collecting or anchoring policy since 2009 (Fig   140   1). The area beyond the green zone is designated as a Conservation Park Zone with eight 141 moorings that are accessible to recreational boats for e.g., diving and fishing activities.

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The Marine National Park "Green" Zone (500 m radius) where no fishing or anchoring is  Ten survey sites were established at 5-10 m depth within the green zone (Fig 1). Four of the      Table). At each site, surveys consolidated into larger groups for visualisation purposes (S1 Table).  Differences between autumn and spring surveys were tested using a Student's t-test based on 241 the overall mean of measurements for the four survey types, i.e., substrate, reef impact, 242 invertebrate and fish. No significant differences across seasons were found, therefore, 243 measurements were averaged across seasons (S2 Table). Measurements per survey type were  Table), as responses in coral    There was no significant difference in the overall mean of measurements for the four survey 306 types between autumn and spring at Flinders Reef (p > 0.050, S2 Table). Therefore, results 307 were pooled across the two seasons.   Overall, the number of reef impacts detected was low (Fig 3B). The most common impacts 322 observed were coral physical damage (average of 0.12 occurrences per 100 m 2 ) followed by 323 coral disease and unknown scars (both averaged 0.08 occurrences per 100 m 2 ). Turtle   Fish community composition was largely dominated by butterflyfish which were recorded at 346 each of the ten sites (Fig 3D), and a total of 524 individuals were counted during the surveys.

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On average, 6.12 butterflyfish were recorded per 100 m 2 ranging from 2.62 at Donna to 12.10   Wave exposure and community composition 378 Sites located on the northwestern side of Flinders Reef were the least exposed to waves.

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Significant wave height was 0.9 m for Turtle Cleaning and Plate, and 1.2 m at Coral Garden 380 (Fig 5A). Wave heights for the seven remaining sites varied between 1.5 and 1.6 m (Fig 5A).

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The median significant wave height across all sites was 1.54 m, separating the less exposed 382 sites (located west to north of Flinders Reef) from the more exposed sites (east to south),  groups with the non-metric multidimensional scaling plot (Fig 3C). Each dot represents a 20 397 m survey segment within a site.

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There was a significant contribution of site (p < 0.001) and wave height (p < 0.001) to coral 400 community composition (    three-fold increase of areas that include hard rock substrate (Fig 1 and 2