Abandoned, lost, or discarded fishing gear at urban coastlines.

Abandoned, lost, or discarded fishing gear (ALDFG) is considered a major threat to ocean biodiversity. Yet, little is known of the interactive impacts of ALDFGs and urban nearshore biodiversity and habitats, especially in Southeast Asia where fisheries efforts are increasing. We identified ALDFG hotspots around Singapore-where 80% of coastal areas are urbanized or anthropogenically modified. Fishing lines and nets were the most common ALDFGs recovered; with strong correlations between ALDFG presence and beaches, intertidal, mangroves, as well as sites with significant coastal modifications. Plastic polymer nets trapped the highest organism diversity and abundance. A total of 1052 trapped individuals comprising 124 species were recovered, the majority in classes Merostomata, Actinopterygii and Malacostraca. The most abundant trapped species was Carcinoscorpius rotundicauda and the highest mortality presentation was in Class Actinopterygii. This study demonstrates that ALDFGs remain a threat to marine biodiversity within urban coastal habitats and at heavily modified shorelines.

Barriers and corridors of gene flow in an urbanized tropical reef system.

Information about the distribution of alleles among marine populations is critical for determining patterns of genetic connectivity that are essential in modern conservation planning. To estimate population connectivity in Singapore's urbanized equatorial reef system, we analysed single nucleotide polymorphisms (SNPs) from two species of reef-building corals with distinct life histories. For Porites sp., a broadcast-spawning coral, we found cryptic lineages that were differentially distributed at inshore and central-offshore sites that could be attributed to contemporary surface current regimes. Near panmixia was observed for Pocillopora acuta with differentiation of colonies at the farthest site from mainland Singapore, a possible consequence of the brooding nature and relatively long pelagic larval duration of the species. Furthermore, analysis of recent gene flow showed that 60-80% of colonies in each population were nonmigrants, underscoring self-recruitment as an important demographic process in this reef system. Apart from helping to enhance the management of Singapore's coral reef ecosystems, findings here pave the way for better understanding of the evolution of marine populations in South-East Asia.