Multifaceted biological indicators reveal an effective conservation scheme for marine protected areas

Marine protected areas are set up across the globe to safeguard biodiversity and support coastal ecosystem functioning. In Hong Kong, partially protected marine parks and a no-take marine reserve have been managed under legislation for years, yet a comprehensive evaluation of their conservation impact is still pending despite the region's reputation for high marine diversity. Most studies assess conservation effectiveness solely in terms of taxonomic diversity, without delving into the contributions of functional and phylogenetic diversity. In this study, we used environmental DNA combined with multifaceted diversity indicators to assess the impact of the level of protection on the fish community in Hong Kong waters. Our results indicated that the marine protected areas significantly contributed to fish community conservation. The no-take marine reserve exhibited the highest taxonomic and phylogenetic diversity, while partially protected marine parks showed the most balanced community composition. No significant increase in fish functional diversity was found in the protected areas. Water quality, hydrological condition, and protection level were the primary factors affecting community variation for taxonomic, functional, and phylogenetic diversity, respectively. Fish species composition significantly varied with different protection levels, and species turnover was the main component of the dissimilarity. Future management of marine protected areas should assess multifaceted biological indicators and establish a rational conservation scheme.