Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including "reef compression" (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas.

Most lost fishing gear is made of non-biodegradable plastics that may sink to the sea floor or drift around in currents. It may remain unnoticed until it shows up on coral reefs, beaches and in other coastal habitats. Stony corals have fragile skeletons and soft tissues that can easily become damaged when they get in contact with lost fishing gear. During a dive survey around Koh Tao, a small island in the Gulf of Thailand, the impact of lost fishing gear (nets, ropes, cages, lines) was studied on corals representing six different growth forms: branching, encrusting, foliaceous, free-living, laminar, and massive. Most gear (>95%) contained plastic. Besides absence of damage (ND), three categories of coral damage were assessed: fresh tissue loss (FTL), tissue loss with algal growth (TLAG), and fragmentation (FR). The position of the corals in relation to the fishing gear was recorded as either growing underneath (Un) or on top (On), whereas corals adjacent to the gear (Ad) were used as controls. Nets formed the dominant type of lost gear, followed by ropes, lines and cages, respectively. Branching corals were most commonly found in contact with the gear and also around it. Tubastraea micranthus was the most commonly encountered coral species, either Un, On, or Ad. Corals underneath gear showed most damage, which predominantly consisted of tissue loss. Fragmentation was less common than expected, which may be related to the low fragility of T. micranthus as dominant branching species. Even if nets serve as substrate for corals, it is recommended to remove them from reefs, where they form a major component of the plastic pollution and cause damage to corals and other reef organisms.

The highest concentration of Malaysian coral reefs is found in the coastal area of Semporna, eastern Sabah, which is located just within the boundaries of the Coral Triangle, the area of maximum marine species diversity. The Semporna reefs consist of five major geomorphological reef types, which include lagoonal reefs inside a proto-atoll, fringing reefs, continental patch reefs, a barrier reef and a reef capping an oceanic island. Surveys were carried out in this area to compare the species richness patterns of the scleractinian coral families Agariciidae, Euphylliidae, and Fungiidae from nearshore to offshore reefs. In total, 44 species of Fungiidae, 31 Agariciidae and 15 Euphylliidae have been observed, including 12 new records for Sabah and 4 records that are so far considered endemic to northeast Borneo. Based on coral species compositions for each site, multivariate analyses suggest the distinction of two main groups that reflect a difference in reef exposure, with a gradient in increasing coral diversity from the exposed barrier reef to the relatively sheltered nearshore reefs. Some reefs have been damaged by blast fishing, a threat still prevalent in the area. Nevertheless, the high coral species diversity is remarkable, and to date, Semporna holds the record for the highest species richness of Fungiidae, which surpasses records from other areas in the Coral Triangle.