Urban coral reefs: Degradation and resilience of hard coral assemblages in coastal cities of East and Southeast Asia

© 2018 The Author(s) 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

Heavy Metals Contamination in Sediments along the Eastern Coast of the Gulf of Thailand

Levels of Hg, Cd, Pb, Zn, Cu, Ni, Fe and Mn in surface sediments were investigated in 52 stations along the Eastern Coast of the Gulf of Thailand. The sediment samples were collected in March 2004. Concentrations of the heavy metals ranged from 0.005 - 0.121 microgram g-1 for Hg, <0.006 - 0.19 microgram g-1 for Cd, 1.69 - 66.3 microgram g-1 for Pb, 7.48 - 131 ±g g-1 for Zn, 14.4 - 103 microgram g-1 for Cu, <0.64 - 79.9 microgram g-1 for Ni, 1.17 - 92.8 milligram g-1 for Fe and 0.03 - 1.71 mg g-1 for Mn. Only Pb and Cu in the sediments exceeded the effects range low of the proposed marine and coastal sediment quality guidelines for Thailand. The calculated geoaccumulation index (Igeo) showed that the sediments were moderately polluted with Pb in some locations, particularly at Map Ta Phut Industrial Estate, and were slightly polluted with Cu, Zn and Mn at some sampling stations. All metals (except Cu) were associated with each other in the sediments. Organic matter, clay and silt were the major sediment components responsible for most metals sorbed in the study area

Toxicity of Mercury to Growth and Survival of Seabass Larvae, Lates calcarifer and the Modifying Effects of Salinity

ABSTRACT: Short-term chronic toxicity tests were conducted to investigate the adverse effects of mercury (Hg) on growth (measured as dry weight) and survival of seabass larvae, Lates calcarifer, and the modifying effects of salinity. Seven-day static-renewal tests were conducted at four salinities: 2, 10, 20 and 30 psu. The experiments were repeated three times for each salinity. Results indicated that seabass larvae were very sensitive to low concentrations of Hg. Based on the actual measured Hg concentrations, the mean NOEC, LOEC and LC 50 values for survival were 30.8, 52.5 and 46.2 µg L -1 , respectively, while the mean NOEC, LOEC, IC 25 and IC 50 values for growth were 5.2, 12.6, 8.5 and 19.2 µg L -1 , respectively. Salinity did not have any significant effects on the toxicity of Hg on survival and growth of seabass larvae. One possible explanation is that Hg preferentially forms very strong complexes with sulfhydryl groups (-SH) in proteins rather than with chloride

Toxicity of mercury and copper to marine phytoplankton, Dunaliella salina, Tetraselmis sp. and Chaetoceros calcitrans

Static 96-hour phytoplankton growth tests were carried out to measure the toxicity of mercury (Hg) and copper (Cu) on growth (cell density) and chlorophyll a content of three marine phytoplankton species: Dunaliella salina, Tetraselmis sp. and Chaetoceros calcitrans. The experiments were carried out at a temperature of 27±1ºC, using natural seawater (salinity 30 psu) filtered with a 0.4 μ polycarbonate membrane, under continuous illumination of 3800±200 lux and they were repeated three times for each metal. Resultsshowed that C. calcitrans was the most sensitive species to Hg and Cu, followed by Tetraselmis sp. and D. salina, respectively. In addition, Hg was found to be more toxic to the three species than Cu. The mean IC50 values of Hg on growth of D. salina, Tetraselmis sp. and C. calcitrans were 0.277, 0.144 and 0.043 mg L-1, respectively, while those of Cu were 1.132, 0.270 and 0.090 mg L-1, respectively